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> **APHIS Evaluation of the Status of Panama Regarding Screwworm
> (*Cochliomyia hominivorax*)**

**Animal and Plant Health Inspection Service**

**Veterinary Services**

**August 2007**

**[Abbreviations]{.underline}**

APHIS Animal and Plant Health Inspection Service

ARS Agricultural Research Service

BPP *Barrera Permanent de Prevencion* (Permanent Preventive Barrier or
Control Zone)

CFR Code of Federal Regulations

CMA *Control de Movilización de Animales* (Control of Animal Movement)

COPEG *Comisión para la Erradicación y Prevención del Gusano Barrenador
del Ganad (*Commission for the Eradication and Prevention of Screwworm)

COPFA *Comisión Panamá-Estados Unidos Prevención Fiebre Aftosa*
(Panama-US Comisión for the Prevention of Foot and Mouth Disease)

DECA *Dirección Ejecutiva de Cuarentena Agropecuaria* (Executive
Directorate for Agricultural Quarantine)

DINASA *Direccion Nacional de Salud* *Animal* (National Directorate of
Animal Health

FAO Food and Agriculture Organization of the United Nations

FMD foot and mouth disease virus

FVE *Franja de Vigilancies Epidemiologica* (literally strip or area of
epidemiologic vigilance)

GBG *gusano barrenador del ganado* (New World Screwwrom; *Cochliomyia
hominivorax)*

ICA *lnstituto Colombiano Agropecuario* (Colombian Agricultural
Institute)

ISO International Organization for Standardization

LADIVES *Laboratorio de Diagnóstico de Enfermedades Vesiculares*
(Laboratory for the Diagnosis of Vesicular Disease)

MIDA *Ministerio de Desarrollo Agropecuario (*Ministry of Agriculture
and Livestock Development)

OIE Office International des Epizooties (World Organization for Animal
Health)

OIRSA *Organismo Internacional Regional de Sanidad Agropecuaria*
(Regional International Organization for Plant Protection and Animal
Health)

PANAFTOSA Pan-American Center of Aftosa Fever Pan American
Foot-and-Mouth Disease Center

SW screwworm (*Cochliomyia hominivorax)*

UNESCO United Nations Educational, Scientific and Cultural Organization

USD United States Dollar

USDA United States Department of Agriculture

[**Executive Summary** 4](#__RefHeading___Toc175129261)

[**Introduction** 7](#__RefHeading___Toc175129267)

[**Hazard Identification** 10](#__RefHeading___Toc175129272)

[**Release Assessment** 13](#__RefHeading___Toc175129274)

\--[**Authority, organization, and infrastructure of the veterinary
services** 13](#__RefHeading___Toc175129275)

\--[**Disease status in the region** 17](#__RefHeading___Toc175129280)

\--[**Disease status of adjacent regions**
19](#__RefHeading___Toc175129282)

\--[**Extent of active disease control program**
19](#__RefHeading___Toc175129283)

\--[**Vaccination status of the region**
24](#__RefHeading___Toc175129285)

\--[**Separation from adjacent regions of higher risk**
24](#__RefHeading___Toc175129287)

\--[**Movement controls and biosecurity from higher-risk regions**
24](#__RefHeading___Toc175129289)

\--[**Livestock demographics and marketing practices in the region**
26](#__RefHeading___Toc175129290)

\--[**Disease surveillance in the region**
27](#__RefHeading___Toc175129291)

\--[**Emergency response capacity** 29](#__RefHeading___Toc175129292)

\--[**Release Assessment Conclusions** 32](#__RefHeading___Toc175129293)

[**Exposure Assessment** 33](#__RefHeading___Toc175129294)

[**Consequence Assessment** 34](#__RefHeading___Toc175129296)

[**Risk Estimation** 35](#__RefHeading___Toc175129299)

[**References** 36](#__RefHeading___Toc175129300)

[]{#__RefHeading___Toc175129261 .anchor}**Executive Summary**

Panama submitted a request to the United States Department of
Agriculture's Animal and Plant Health Inspection Service (APHIS) seeking
recognition as a region free of the *Cochliomyia hominivorax* screwworm
(SW). To accomplish this, a country needs to be removed from the list of
affected countries in Title 9, Code of Federal Regulations (9 CFR 93).
This requires rulemaking. Upon receipt of the request, APHIS initiated
an evaluation of the status of the Republic of Panama with regard to SW
to assess the risk of exempting Panama from current CFR restrictions by
removing Panama from the list of SW affected countries.

The eradication and prevention of SW in Panama was the result of a
cooperative program strongly supported by USDA using the systematic
release of adult *Cochliomyia hominivorax* flies sterilized by exposure
to irradiation. The sterile fly mates with the native fertile female fly
population to produce sterile eggs, interrupting the lifecycle resulting
in eradication of the population \[14\]. This effort resembles the SW
eradication and prevention cooperative programs utilized in Mexico and
the other Central American countries which APHIS currently recognizes as
SW-free. All of these programs used the sterile fly dispersion
methodology and all have remained successfully SW free since eradication
was completed.

In 1998, Panama began field activities as a cooperative program
involving Panama's Ministry of Agriculture and Livestock Development
(*Ministerio de Derarrollo Agropecuario, Direccion Nacional de Salud
Animal* (MIDA)), Commission for the Eradication and Prevention of
Screwworm (*Comisión para la Erradicación y Prevención del Gusano
Barrenador del Ganad* (COPEG)) and the United States Department of
Agriculture (USDA). The permanent biological barrier was established in
the Darien Gap region adjoining Colombia and the continent of South
America in 2001.

The success of the sterile fly release method has resulted in the
eradication of SW from all of Central America and the establishment a
permanent biological barrier between Central American and the South
American continent maintained through the continued release of sterile
flies, intensive monitoring and movement controls. This permanent
biological barrier was established in the sparsely inhabited Darien Gap
area of Panama, an area roughly 100 miles long and 30 miles wide. The
area has a very low human and domestic animal population and has no
major roads connecting the Republic of Panama into Colombia.

The US is evaluating the SW status of Panama because of the potential
risk of introduction of SW from Panama to the US. Therefore, the
assessment evaluated the infrastructure, and control measures in place
for SW and includes an assessment of SW surveillance measures,
laboratory capacity, emergency response procedures, and other factors
that could influence the risk of SW introduction into the United States.
Supporting documentation for this risk analysis consists of
documentation provided by MIDA, COPEG, USDA and other technical sources
that could influence the likelihood of disease introduction into the
United States.

This risk analysis was conducted according to OIE guidelines and
therefore includes hazard identification, release assessment, exposure
assessment, consequence assessment, and risk estimate \[12\]. The
documentation provided indicates that SW has been eradicated in Panama.

*Hazard identification*

The hazard under consideration is New World Screwworm (*Cochliomyia
hominivorax*) (SW).

*Release assessment*

APHIS finds that SW was successfully eradicated from the Republic of
Panama outside the area of the Darien Gap and that an effective
prevention program is in place based on the establishment and
maintenance of a permanent biological barrier in the Darien Gap.
Eradication was accomplished through the release of sterile male flies.
Although SW was eradicated in the Darién Gap, assurance that SW is not
reintroduced into Panama is supported by the continued monitoring and
release of sterile flies, even after eradication.

APHIS has no evidence that SW currently exists in Panama as SW has not
been detected in domestic livestock outside the permanent biological
barrier since 2003. Panama's current surveillance practices for SW are
such that an incursion of SW would be recognized and the veterinary
infrastructure is well trained and equipped to contain and eliminate an
outbreak. The biological barrier ensures that SW will not be released
into Panama from the South American continent. The maintenance and
monitoring of the permanent biological barrier in the Darien Gap is the
responsibility of COPEG, supported by the cooperative efforts of USDA
and MIDA. If SW were reintroduced into Panama, it would likely be
detected and contained before spreading.

The likelihood of introduction of SW into the US is limited to the
importation of SW infested live animals, as *Cochliomyia hominivorax*
larvae survive only in living tissues. Therefore, there is no risk
associated with the importation of commodities such as meat or animal
byproducts. To pose a risk for US livestock, an infested live animal
would have to be imported, the infestation remain undetected and
untreated, followed by the emergence of viable larvae from the wound and
successful pupation in soil resulting in the emergence of fertile flies.
These fertile flies would need to mate successfully and depositing
fertile eggs in the wound of a domestic animal. The management and
inspection practices in the US associated with the care of animals of
sufficient value to warrant importation would be likely to result in the
treatment of infested wounds resulting in the elimination of viable
larvae. General good animal husbandry practices, which include insect
control measures, would further mitigate the likelihood of introduction
and establishment of endemic SW in the US.

Panama shares a common land border with Colombia, a region that APHIS
does not consider to be free of SW. In this regard, the risk profile of
Panama resembles that of countries where SW was previously eradicated,
such as Mexico and the Central American countries when the successful
cooperative eradication programs were completed but the country shared a
border with a country that remained affected with screwworm.

*Exposure Assessment*

APHIS assessed the probability of exposure of susceptible animal
populations in the United States to SW carried by imported livestock
from Panama. APHIS considers that the most likely pathway of exposure of
US cattle and other species susceptible to SW is through contact with
infected/infested animals under conditions that would allow completion
of the SW lifecycle \[11\]. Other more indirect exposure pathways, such
as through animal products, are not likely to result in
infection/infestation because the larvae of the SW do not remain viable
in other media except viable flesh.

*Consequence Assessment*

APHIS also assessed the biological and economic consequences of
introducing SW into the United States. This assessment concluded that SW
has the potential to cause significant distress and suffering in
affected animals. The economic costs of control and eradication would be
substantial if *Cochliomyia hominivorax* were to become established in
the United States. The magnitude of the biologic and economic
consequences following an introduction of SW would depend on the
location, time of the year, the rate of spread, ability to detect the
disease rapidly, demographics and movement patterns of susceptible
species, and relative ease of employing eradication procedures. Direct
consequences include effects of the disease on animal health, subsequent
production losses, total cost of control and eradication, the effect on
the environment, and public health consequences. Indirect consequences,
including impacts on international trade and associated domestic
consequences, are not likely to result from an outbreak of screwworm
because of the existing available treatment options.

*Risk estimate*

In summary, although a SW outbreak in the United States would be likely
to have animal health and economic consequences, APHIS considers the
risk of infected live animals entering the United States from the
Republic of Panama and exposing U.S. livestock to be low.

[]{#__RefHeading___Toc175129267 .anchor}**Introduction**

Panama submitted a request to the Animal and Plant Health Inspection
Service (APHIS) seeking recognition as free of *Cochliomyia
hominivorax,* known more commonly as New World Screwworm (SW) \[10\].
This risk analysis was conducted according to the format recommended by
OIE and, therefore, includes hazard identification, release assessment,
exposure assessment, consequence assessment, and risk estimate \[12\].

*Hazard identification*

The hazard under consideration is SW.

***History of SW in the US***

The US reported the presence of SW as early as 1825 in the Western
States. By 1933, SW had migrated from the Southwest to the Southeast
United States in a shipment of infested animals and within the year six
states in the southeast were infested \[7\]. The economic impact in the
southeastern States at this time was substantial with producers
experiencing losses of \$400 million annually. In 1935, in spite of
control efforts approximately half the counties in Texas were infested,
resulting in 180,000 livestock deaths \[5\].

Eradication of SW was not practical until the development of the sterile
fly release technique. SW was first eradicated using sterile fly release
in Florida in 1959, however, quarantine regulations were difficult to
enforce and small reinfestations continued to be reported in Florida,
southern Alabama, and Louisiana. These reinfestations were successfully
controlled by saturating the areas of the outbreak with sterile flies.

Eradication of indigenous SW in the US was completed by 1966. However,
sporadic outbreaks continued to appear as the result of SW flies
entering from Mexico. In 1972, the United States experienced its worst
outbreak of SW cases since 1966 when California, Arizona, New Mexico,
Texas, Oklahoma, and Arkansas reported SW-infested livestock. In 1972
Texas confirmed 90,000 cases, after reporting 444 in 1971. The resources
to contain this outbreak were considerable. Plans were then developed to
progressively eradicate SW in Mexico and establish a biological barrier
to prevent incursion of the SW fly into the US. The eradication of SW in
Mexico began in 1972 at the Texas-Mexcio border and progressed southward
until eradication was completed in 1991 \[14\].

Following eradication of SW in the US, several limited outbreaks have
occurred in the US as the result of importation of infested live
animals. In 1997, SW larvae were detected on a dog shipped to San
Antonio, TX, from a US military base in Panama \[5\]. In l998, following
the positive identification of SW larvae in a goat in Texas, more than
40,000 head of livestock and dogs in the area were examined for signs of
SW infestation. Fortunately, no other larvae were found before the onset
of cold weather eliminated the potential for any SW flies present to
winter over; however, the origin of the SW was never confirmed.

In 1999, SW larvae were found in a horse imported from Venezuela. In
2000, one of 16 horses shipped to Florida from Argentina was discovered
to have SW larvae in a wound, however, none of the other horses showed
any signs of SW. In this case the SW larvae were at least 24 hours from
maturity and it was considered unlikely that any larvae had dropped from
the wound. As a precaution, the premises were treated to ensure that any
larvae that might have exited the wound were destroyed \[4\]. These
findings prompted APHIS to respond with an emergency action and put in
place an interim rule to institute inspection and treatment for SW for
horses, ruminants, swine, and dogs for animals imported from countries
considered to be affected by SW \[2\]. The interim rule was made final
in 2002 \[4\]. Panama was included in the list of SW affected countries
in Title 9, Code of Federal Regulations (9 CFR) when the SW regulations
were put in place in 2000[^1].

*History of the Screwworm Eradication Program*

The Screwworm Eradication Program in Panama was established in 1994
through the cooperative efforts of the government of Panama and the
Animal and Plant Health Inspection Service of the United States
Department of Agriculture (USDA-APHIS). The Screwworm Eradication
Program utilizes the Sterile Insect Technique to release sufficient
numbers of sterile male SW flies to mate with the wild fly population.

Following successful eradication of SW in the United States, the Sterile
Fly Release Program was expanded into Mexico in 1972 to establish a
biological barrier at the Isthmus of Tehuantepec in southern Mexico.
Eradication in Mexico was completed in 1991. The Program was later
expanded with the goal of covering the entire Central American Isthmus
and Panama and eventually reaching the Darien Gap area on the border
with Colombia. The Screwworm Eradication Program progressed southward
toward Panama, completing eradication in Belize and Guatemala in 1994,
El Salvador in 1995, Honduras in 1996, Nicaragua in 1999 and Costa Rica
in 2000.

Use of the Sterile Insect Release Technique to eradicate *Cochliomyia
hominivorax* has proven to be a very efficient eradication technique
because the female fly mates only once while the male mates many times
so that sterile males can mate multiple times with the fertile wild
females. The result of mating with a sterile male is the production of
non-viable egg masses which interrupt the insect's life cycle. In this
way the release of sufficient numbers of sterile males in an area
results in eradication after several lifecycles. In Panama, the flies
will continue to be released in the permanently established biological
buffer area at the Darien Gap to prevent reintroduction across the
Colombia border from the South American continent where SW remains
endemic.

Sterile SW flies are artificially raised in a laboratory and sterilized
by exposing them to a low dose of irradiation just before they pupate.
Irradiation at this time inhibits the development of the ovaries in
females and the testes in males without affecting any other body part
resulting in normally developed but sterile adult flies. The sterile
flies are dispersed by airplane on regular intervals at controlled
density to saturate an area.

The original sterile fly production plant for the program was in
Mission, Texas and was replaced by a plant at Tuxtula, Gutierrez,
Chiapas Mexico in 1976. Construction on the Panama Mass Rearing and
Research Facility began in February, 2004, in Pacora, Panama, about 25
miles east of Panama City where sterile fly production will begin in
2008 \[2, 3, 4, 7\].

[]{#__RefHeading___Toc175129272 .anchor}**Hazard Identification**

APHIS identifies several animal diseases listed by OIE as hazards when
considering trade in animals and animal products from foreign regions
\[13\]. One of these diseases is SW. SW is exotic to the United States;
therefore, before opening trade in live animals with a region or country
considered to have been affected with SW, APHIS conducts an import risk
analysis. OIE does not suggest restrictions on the import of animal
products because the SW larva cannot survive for any length of time in
dead tissues or animal products \[13\].

The New World screwworm, *Cochliomyia hominivorax*, is an obligate
parasite of warm blooded animals during its larval stages. *Cochliomyia
hominivorax* is in the subfamily Chrysomyinae of the family
Calliphoridae (dipterous flies) of the order Diptera (true flies) that
is endemic only in the tropical and subtropical regions of North,
Central, and South America. In the Spanish language, SW is known as the
gusano barrenador del Ganado (GBG) and may also be referred to as
Coquerel.

*Cochliomyia hominivorax* is a serious pest of warm-blooded animals,
capable of causing injuries and death to livestock, domestic animals,
occasionally birds and infrequently human beings. *Cochliomyia
hominivorax* infestation occurs when the eggs hatch in the wound and the
larvae feed on the animal's flesh. Unlike most other species of
blowflies, adult female SWs do not lay their eggs on carrion \[13\]. The
female SW fly lays her eggs only in the flesh of living animals, at the
edges of wounds or body orifices. Individual females lay eggs in
clusters of 300 eggs tightly adhered to each other and the wound
substrate. Virtually any wound is attractive, whether natural (from
fighting, injury, predators, thorns, disease, and/or tick and insect
bites) or man made (from shearing, branding, surgical sites, castrating,
de-horning, docking, and/or ear-tagging). Commonly infested natural
wounds are the navels of newborn animals and the vulval and perineal
regions of perinatal animals, especially if traumatized. If eggs are
deposited on mucous membranes, the larvae can invade natural body
openings such as the nostrils and associated sinuses, the eye orbits,
mouth, ears, and genitalia.

Multiple infestations are typical with additional female SW flies
depositing their eggs. As many as 3,000 larvae may be found in a single
wound. A bloody discharge often exudes from the infested wounds,
frequently accompanied by a distinct fetid odor. Infested animals
usually exhibit discomfort, may go off feed, and may separate themselves
from the rest of the flock or herd to seek shady or secluded areas to
lie down. Animals with severe SW infestations may die in 7 to 14 days if
wounds are not treated to kill the larvae, especially in cases of
massive infestations. Death is generally the result of toxicity and/or
secondary infection. However, most cases are less severe and
characterized by weight loss and secondary bacterial infections \[11\].

The larvae typically emerge from the egg within 12-24 hours but may
emerge as early as 8 hours after being deposited in the wound \[7, 11\].
The freshly emerged larvae immediately begin to feed by burrowing into
the wound to feed on the underlying tissues, enlarging and deepening the
wound \[11\]. Enlargement of the wound attracts additional SWs. Larvae
feeding on the skin and underlying tissues of the host cause a condition
known as wound or traumatic myiasis. Within the wound the larvae undergo
two moults before reaching maturity at 5-7 days after hatching. The
larvae then leave the wound, fall to the ground to burrow and pupate
between one week and several months \[11\].

*Figure 1. Simplified screwworm ([Cochliomyia hominivorax]{.underline})
life cycle* \[6\]

> ![](media/image2.jpeg){width="3.375in" height="2.7534722222222223in"}

The duration of the life-cycle is temperature dependent and under
tropical or semitropical conditions the whole cycle may be completed in
less than 3 weeks \[6\]. The most profound effect of ambient temperature
is on the off-host pupal stage, which can vary from 1 week to 2 months\'
duration depending on the season. In cooler weather the complete life
cycle may take up to 2-3 months, however with an average air temperature
of 22°C (71° F) it is completed in about 24 days, and in tropical
conditions averaging 29°C (84° F) it may be completed in only 18 days.
SW cannot winter over well under non-tropical conditions, preferring hot
humid conditions and may only sustain an endemic population in tropical
to semi-tropical areas \[9, 11, 14\].

Male *Cochliomyia hominivorax* flies become sexually mature and able to
mate within 24 hours of emerging from the pupa. Female *Cochliomyia
hominivorax* flies are responsive towards males and mate approximately 3
days after emerging from the pupa. Male *Cochliomyia hominivorax* are
aggressive breeders and mate frequently but females mate only once; thus
the mating of sterile male flies with the fertile (wild) females
resulting in production of sterile eggs serves to break the life cycle.
About 4 days after mating, female flies are ready to lay their
fertilized eggs (oviposit) in batches of up to 300 eggs and are able to
lay up to 4 egg batches at 3 to 4 day intervals. Adult flies live on
average for 2-3 weeks under field conditions but may live up to 60 days
under optimal conditions \[9, 11, 14\]. They are powerful fliers with a
potential range of 20 to 30 miles, although they may range over
considerably longer distances if carried by the wind or in search of an
appropriate host in which to lay their eggs in areas of sparse animal
density.

*Cochliomyia hominivorax* diagnosis is readily done by microscopic
examination of the larvae, pupae or adult stages. Physical distinctions
at all stages can be used to differentiate *Cochliomyia hominivorax*
from some 20 species of flies capable of producing myiasis. This
includes, among others, members of the Calliphoridae family, such as the
closely related *Cochliomyia macellaria* (common name- Fabricius or
secondary screwworm) or *Phaenicia* spp. (common name- bottle flies).
Another dipterous fly with neotropic distribution in the Cuterebridae
Family, *Dermatobia hominis* (common names- human bot fly, American
Warble or Torsalo)*,* is also frequently associated with myiasis and has
a multiple host range.

*Cochliomyia hominivorax* infestation may be treated with topical or
systemic application of approved chemicals to kill the larvae (*9 CFR
93*). The larvae should be physically removed from the wounds with
tweezers and wounds should be treated until the wound is completely
healed. Treating wounds and spraying or dipping animals with an approved
product such as organophosphates or other insecticide will provide
protection against SW for up to 7 to 10 days. However, the most
effective way to control SW infestation remains eradication.

[]{#__RefHeading___Toc175129274 .anchor}**Release Assessment**

A release assessment describes the biological pathway(s) necessary for
an importation activity to introduce pathogenic agents into a particular
environment and estimates the probability of that introduction \[12\].
This release assessment addresses the 11 factors described under 9 CFR
92.2 for evaluation of foreign animal disease status. Risk factors and
issues of concern, which may directly or indirectly affect the risk
estimate, are identified during this process. APHIS evaluated the
current status of Panama with regard to SW to decide whether it can
recognize Panama as SW free and remove it from the SW-affected list.
This action would be taken based on the risk finding that susceptible
animals originating in Panama would pose a very low import risk to the
US.

[]{#__RefHeading___Toc175129275 .anchor}**Authority, organization, and
infrastructure of the veterinary services**

Screwworm eradication in the Republic of Panama was accomplished through
a Cooperative Agreement, signed on February 11, 1994, between the
Panamanian Ministry of Agriculture and Livestock Development (MIDA) and
United States Department of Agriculture (USDA) \[1\]. The Cooperative
Agreement establishing the Panama-US Commission to Eradicate and Prevent
SW (*Comisión para la Erradicación y Prevención del Gusano Barrenador
del Ganad,* COPEG) was created as a part of the USDA Regional Plan to
eradicate SW in Central America. COPEG serves as the Veterinary
Authority, and in this role directly controls the specifics of the
eradication and prevention program with the full cooperation of Panama's
veterinary infrastructure with financial and scientific support from
USDA. COPEG applied the preexisting infrastructure and legal framework
developed within Panama for the eradication of foot and mouth disease
disease (FMD) and shares many of the resources developed under the
*Comisión Panamá-Estados Unidos Prevención Fiebre Aftosa* (COPFA).

*COPEG*

As specified in the Cooperative Agreement, COPEG (also referred to as
the Commission), has 2 full time Directors, one of which is a USDA
official and other is the Panamanian MIDA Director. In addition, there
are also 8 Commission members, 4 designated by the Secretary of the USDA
and 4 designated by Panama MIDA. The Commission annually reviews all its
activities, provides guidance and approves annual work plans and
budgets. The Cooperative Agreement supports all phases of eradication
and prevention.

The Cooperative Agreement provides COPEG with the legal basis to conduct
the eradication and preventive phases of the SW program by mandating the
development and execution of annual work plans. It provides for the
necessary technical support activities including; establishment of
animal quarantine control measures and treatment stations, maintenance
of livestock census, SW surveillance, establishment and maintenance of
laboratory support and aerial dispersion of sterile SW flies in Panama.
The Cooperative Agreement provides for the training of personnel,
development of general education efforts and conduct of periodic
training exercises to support emergency outbreak response. The
development of a contingency plan to respond to outbreaks is also part
of the Cooperative Agreement \[1\].

Funding is provided jointly by USDA and MIDA. The Cooperative Agreement
specifies that during the eradication phase, USDA provided 85% of the
financial resources and MIDA provided the remaining 15%. Following
completion of the eradication phase, the continued funding to maintain
the permanent biological barrier is to be funded 90% by USDA and 10% by
MIDA. Annually the cooperative eradication and prevention program has
cost between \$7.8 and 10.5 million USD \[8\].

Figure 2. COPEG organizational chart.

Three groups within COPEG carry out the majority of field operations;
*Control De Movilizacion de Animales* (CMA), *Franja de Vigilancie
Epidemiologica* (FVE) and *Barrera Permanente de Prevencion* (BPP).
*Control De Movilización de Animales* (Control of Animal Movement or
CMA) works with the Panamanian Ministry of Agriculture and Livestock
Developments *Dirección Ejecutiva de Cuarentena Agropecuaria* (Executive
Directorate for Agricultural Quarantine or DECA) to conduct field
surveillance for SW and vesicular diseases at movement control points
throughout the Republic of Panama. Field operations for disease control
and surveillance measures are managed by *Franja de Vigilancie
Epidemiologica* (FVE, literally strip of epidemiologic vigilance) and
*Barrera Permanente de Prevencion* (BPP, Permanent Preventive Barrier)
maintains and monitors the permanent biological barrier in the Darien
Gap.

Diagnostic support is provided by LADIVES (*Laboratorio de Diagnóstico
de Enfermedades Vesiculares*). This lab was initially established to
handle the diagnostic work for the FMD eradication and prevention
efforts under the *Comisión Panamá-Estados Unidos Prevención Fiebre
Aftosa* (COPFA, Commission of the Panama-United States to Prevent Foot
and Mouth Disease) and continues to do diagnostic work for FMD and other
vesicular diseases. LADIVES also serves as the regional FAO Reference
Laboratory.

COPEG maintains approximately 90 full time inspectors with 53 working in
the Darien Gap area of Panama along the Panama-Colombia border with an
additional 40 inspectors in the free zone north and west of the Darien
Gap to monitor livestock for both SW and FMD \[6\].

*Republic of Panama*

In the Republic of Panama, the Ministry of Agriculture and Livestock
Development (*Ministerio de Desarrollo Agropecuario* or MIDA) is the
federal department within the government of Panama responsible for the
agriculture and livestock sectors. The roles and responsibilities of
MIDA are considered equivalent to United States Department of
Agriculture (USDA). MIDA has 10 Regional Directorates, one located in
each province and two in the Province of Panama (East Panama and West
Panama). MIDA, among other responsibilities, develops and maintains the
legislation and enforcement capability to support the Cooperative
Agreement including establishment of the authority to support quarantine
measures, provides the authority to enter premises for Program purposes
and establishment of mandatory reporting of suspected cases of SW. MIDA
is responsible for the purchase and distribution of insecticides for use
in both the eradication effort and barrier maintenance. MIDA obtains the
support of police and other state security agencies in Panama for the
enforcement activities and ensures that MIDA field personnel cooperate
with the COPEG by reporting infestations and submitting samples of
dipterous larvae collected from wounds for identification.

Within MIDA, the National Directorate of Animal Health (*Direccion
Nacional de Salud Animal* (DINASA)) has roles and responsibilities
similar to APHIS/VS. Within DINASA *Dirección Ejecutiva de Cuarentena
Agropecuaria* (Executive Directorate for Agricultural Quarantine or
DECA) assists in conducting field surveillance for SW, primarily in the
areas of Panama outside the Inspection and Control Zones in Darien
Province, DECA also works closely with COPEGs *Control de Movilización
de Animales* (Control of Animal Movement or CMA) in animal quarantine
activities and the control of animal movements.

*Figure 3. Organization chart of MIDA,*
\[http://www.mida-dinasa.gob.pa/\]

![](media/image3.png){width="5.396527777777778in"
height="5.147916666666666in"}

The 1994 Cooperative Agreement between MIDA and USDA for the eradication
and prevention of SW was incorporated directly into Panamanian Law No.
13, and was amended in 1999 to support the building of the sterile fly
production plant in the Pacora, Panama. Panama has a well developed
system of legislative and regulatory support for the SW program, much of
it developed for the earlier FMD eradication efforts. Panamanian Law No.
23, (1997 and amended as Law No. 62 in 2002), provides for the
zoosanitary authority to support measures for the prevention, diagnosis,
investigation, control and eradication of the animal disease, and
provides the legal mechanism for quarantine, public health and the
environmental protection. Under Panamanian law notification of the
veterinary authorities is mandatory for SW.

The authority to establish Control and Inspection Zones used for SW
eradication and prevention are also found in regulation used earlier in
the FMD eradication program. Law No. 6, dated March 30, 1993, amended
Decree No. 121, dated May 12, 1966, that established inspection and
control zones in Darien and San Blas (Kuna Yala Indigenous Area)
Provinces in the border region with the Colombia. Decree No. 85, dated
September 17, 1973, established control and eradication measures for
contagious and parasitic diseases of livestock with provisions that
allow the National Guard to lend support when needed in outbreak control
and authorizing entry on to the proprieties of livestock holders. This
Decree puts MIDA in charge of the Monitoring Committee to supervise the
field veterinarians that carry out COPEG related activities. The legal
authority to cooperate with international animal health organizations
such as OIRSA (Regional International Organization for Plant Protection
and Animal Health or *Organismo Internacional Regional de Sanidad
Agropecuaria*) and Pan-American Center of Aftosa Fever (PANAFTOSA) is
also provided in this regulation.

*USDA*

USDA/APHIS has played a very active role in the eradication and
prevention of SW in North and Central America. In Panama, USDA has
provided extensive financial and scientific resources for the effort as
a full participant in COPEG. The Cooperative Agreement specifies that
USDA provide one of the two full time COPEG Directors and is responsible
for the appointment of 4 of the 8 Committee Members. USDA has
cumulatively spent at least 90 million dollars (USD) on SW eradication
and prevention in Panama with annual contributions roughly averaging \$5
million USD \[8\].

The new sterile fly production plant in Pacora, Panama, was completed in
2007 at the cost of \$40 million USD, was funded 90% by the US and 10%
by Panama \[briefing book\]. The ongoing cost of operating the program
and the production plant is projected to be between \$7 and 9 million
USD annually with funding to maintain at 90% the US and 10% Panama
\[6\].

*Discussion:* In the Republic of Panama the eradication and prevention
of SW has been accomplished through the cooperative efforts of COPEG,
MIDA and USDA. Panama has available the necessary legal authority,
infrastructure, budget, and supporting resources to carry out the
program and maintain their screwworm free status. APHIS could not
identify any risk issues associated with this factor that would pose an
unacceptable risk to the United States if trade with were to occur.

[]{#__RefHeading___Toc175129280 .anchor}**Disease status in the region**

SW eradication in Panama proceeded from west to east. The last case of
SW in the Western Region was reported in August of 2000. In 2001 the
last case of SW in the Central Provinces of Panama and Colon was
reported. However, in early 2003, as the result of the accidental
release of fertile flies an outbreak occurred which resulted in 439
cases of SW (discussed further below under Emergency response capacity).

As with previous eradication programs in the other Central American
countries, SW eradication in the Republic of Panama was considered to be
complete after no reports of SW were made for 6 months in areas outside
of the permanent biological barrier at the Darien Gap. In the other
Central America countries the successful completion of the SW
eradication programs in that country was always accompanied by the
implementation of a similar program in the adjacent country to
progressively eradicate SW southward from Mexico. Since 1991, the long
term goal of the USDA/APHIS eradication plan has been to eradicate SW
from all of Central America and to establish a permanent biological
barrier in the Darien Gap region of Panama to prevent reinfestation from
South America. Panama is the most southern country in Central America
and borders the continent of South American by sharing a border with
Colombia. USDA/APHIS considers South America, including Colombia to be
endemic for SW and there is no active SW eradication program in place in
Colombia. However, since 2003 COPEG has routinely dispersed sterile
flies over first 20 nautical miles into Colombia to effectively extend
the functional size of the permanent biological into Colombia.

Figure 4. Map of Panama, showing provinces and indigenous areas.
[]{.mark}![](media/image4.png){width="6.25in"
height="3.5416666666666665in"}

In this regard, the SW status of Panama does not differ from the other
North and Central American countries from which SW has been successfully
eradicated that bordered on countries where SW was still endemic. In the
specific case of Panama the maintenance of the permanent biological
barrier serves to mitigate the presence of SW in Colombia and other
parts of South America by actively dispersing sterile flies and
intensely monitoring for SW reinfestation.

No cases of SW have occurred in Panama outside the biological barrier
since 2003 and the number of reported cases within the barrier area has
been very low. In both 2004 and 2006 there were only two cases of SW
detected within the Inspection Zone and in 2005, COPEG inspectors found
4 positive cases of SW in domestic animals (2 pigs and 2 cattle) in
areas within the Inspection Zone. All cases were located within the
biological barrier area and very close to the Colombian border. After
identification of SW the location is saturated by additional sterile fly
release over an area of least 25 by 25 miles. The additional release is
done for at least 8 weeks to allow for at least two complete lifecycles
of the fly to occur.

The infrequent but continuing identification of SW within the area of
the permanent biological barrier, especially in the areas closest to the
Colombian border, is an expected occurrence. The measures in place in
the Inspection and Control Zone; including the continued sterile fly
dispersal with intensive surveillance and movement controls, are
integral to maintaining SW freedom in the rest of Central America. The
Inspection and Control Zone activity is designed to detect and prevent
the incursion of SW from the South American continent. The
identification of these infrequent cases of SW is an indication of the
success of the efforts and effectiveness of the permanent biological
barrier. The permanent biological barrier will continue to be maintained
through the systematic dispersal of sterile flies and intensive
monitoring by COPEG \[6\].

*Discussion*

The last reported native case of SW outside the permanent biological
barrier in the area of the Darien Gap occurred in 2001. The continued,
but extremely low, finding of SW within the buffer area adjoining the
border with Colombia is an expected occurrence. The established
permanent biological barrier and continued intensive surveillance will
act to prevent the escape of SW into the rest of Panama and Central
America. APHIS could not identify any risks associated with this factor
that would pose an unacceptable risk to the United States if trade with
Panama in live animals were to occur.

[]{#__RefHeading___Toc175129282 .anchor}**Disease status of adjacent
regions**

Panama is bordered on the south by the Pacific Ocean and on the north by
the Caribbean Sea with a total of 2,490 km of coastline. Panama has a
330 km long land border on the west with Costa Rica and a 225 km border
on the east with Colombia. As previously mentioned, SW has been
eradicated from Costa Rica but Colombia is still considered to be
affected

Cooperative Programs successfully eradicated SW in 1991, Guatemala in
1994, Belize and El Salvador in 1995, Honduras in 1996, Nicaragua in
1998 and Costa Rica in 2000. These eradication efforts were all done
through a series of cooperative agreements similar to that supporting
COPEG with extensive USDA financial and technical support. The ultimate
goal of the USDA Regional Screwworm Plan has been to eradicate SW in all
of Central America and to establish a permanent biological barrier to
prevent reinfestation from South America

In Colombia, under an initiative of the Republic of Panama and the USDA
Regional Screwworm Plan, a number of SW eradication activities have been
implemented with the intent of expanding the protection zone beyond the
Panama border, into Colombia's Choco region. COPEG is currently
dispersing sterile flies 20 nautical miles into Colombia on a routine
basis. COPEG officials have also developed training activities to foster
the exchange of information from their counterpart in Colombia, the
Colombian Agricultural Institute (*lnstituto Colombiano Agropecuario*
(ICA)), to allow for epidemiological surveillance further into Colombia.

*Discussion:* The existence of a common land border with a SW-affected
region presents a risk for re-introducing SW into Panama from Colombia.
However, the work supported by USDA thorough COPEG to establish and
maintain a permanent biological barrier at the Darien Gap serves to
mitigate the risk of reinfestation of Panama with SW.

[]{#__RefHeading___Toc175129283 .anchor}**Extent of active disease
control program**

In Panama the eradication program was initiated in 1994 following the
signing of the Cooperative Agreement \[1\]. By 2001, eradication had
been accomplished in the western part of Panama and the dispersal area
was moved eastward toward the Darién Gap. Establishment of the permanent
biological barrier was begun in the Darien Gap area in 2001 by
concentrating the dispersal of sterile flies over a smaller area east of
the canal and closer to the Colombian border.

The permanent biological barrier established by COPEG includes
maintaining Control and Inspection Zones in Darien Province and Kuna
Yala to monitor for SW and FMD (see Figure 5). Restrictions established
for the FMD eradication program have been in place in this area since
1966. All physical premises in the Control and Inspection Zones are
regularly monitored by COPEG personnel, who maintain a census and
registry of all livestock and livestock holdings. All domestic animals
are subject to movement controls and inspection. Cattle may only leave
Darien to move directly to slaughter under formal authorization and may
only go directly to slaughter establishments where they are subject to
official inspection for both FMD and SW. Swine are limited to those
raised for personal consumption.

The Inspection Zone extends from the border with Colombia approximately
40 km into the Province of Darién, including portions of the indigenous
areas of Emberá-Wounan and Kuna Yala. In the Inspection Zone the rearing
of animals susceptible to FMD is prohibited, with the exception of swine
for personal consumption. All holdings with animals within the
Inspection Zone are registered and monitored by the regional
epidemiologist. The Control Zone encompasses the remainder of the Darien
Provence and Kuna Yala. In the Control Zone commercial cattle production
is minimal and only permitted under regulation.

MIDA\'s Agricultural Quarantine Directorate (DECA), in cooperation with
COPEG, employs a staff of 15 inspectors and 1 supervising veterinarian
to inspect all animals moved from the province of Darien at 3 movement
posts,in Platanilla, Palmas Bellas and Agua Fría \[6\]. Cattle may only
leave Darien to move directly to slaughter under formal authorization
and may only go directly to slaughter establishments where they are
subject to official inspection for both FMD and SW.

Figure 5. Map of Panama, showing the Province of Darien in white, Kuna
Yala Indigenous area in tan. The Inspection Zone is outlined in red.
\[7\]

![](media/image5.jpeg){width="6.997916666666667in"
height="3.5277777777777777in"}

To conduct disease surveillance in the Inspection and Control Zones,
COPEG maintains 19 field surveillance control posts staffed with 53
inspection officers supervised by 3 veterinarians in Darien with
additional posts in the Kuna Yala Indigenous Area staffed by 8 officers.
The responsibilities of the inspectors include visiting all animal
holdings in the Inspection and Control Zones to do animal health
monitoring, maintain the animal census, sample suspicious wounds,
provide disease awareness training to animal owners, provide wound
treatment medication and kits for sample submission by animal owners and
issue movement control certificates.

Figure 6. Map of the control posts located in the permanent biological
barrier in eastern Panama, indicating the location of the Inspection
(turquoise), Control (grey)and Atlantic Zones (purple) with the names
and locations of movement controls points \[note that Buena Ventura and
Sanson are locations for area inspectors\]. \[8\]

![](media/image6.png){width="5.98125in" height="5.0472222222222225in"}

To maintain the permanent biological barrier 30-32 million flies are
dispersed each week at the rate of 3,000 sterile flies per square mile.
Dispersal flights occur 4 days a week, with 3 flights each day with no
seasonal variation. Currently an average of 30 to 40 dispersal flights
are done each month to maintain the biological barrier \[8\]. All
flights are logged and mapped using a global information system (GIS) to
ensure that greater than 90% of the target area is consistently covered
on a weekly basis.

During the eradication process the number of flights was substantially
higher as a larger area was saturated with sterile flies. The program
began in 1998 with 418 flights, increased to 619 in 1999 and reached a
high of 1305 in 2000. From 2001 onward, as eradication proceeded from
west to east it was possible to decrease the number of flights in the
free areas and concentrate the dispersal in the area of the permanent
biological barrier. In 2001 there were 859 sterile fly dispersal
flights, 623 in 2002, 654 in 2003, 586 in 2004 and 418 in 2006. Flights
20 nautical miles into Colombia began in 2003 and now average 25 to 40 a
month for an annual total of more than 400 dispersal flights \[8\].

Following the positive identification of a SW sample within the barrier
area, the location is recorded and more intensive sterile fly release in
a grid of at least 25 by 25 miles over the area for at least 8 weeks to
cover two SW lifecycles. After detection of SW in the Inspection Zone
monitoring of the area by COPEG investigators is also enhanced to alert
animal owners of the occurrence of a case of SW and survey for the
presence of lesions presenting risk of infestation (navel infection of
newborns, natural or surgical wounds, such as castration or dehorning)
to increase sampling.

As part of the ongoing prevention program COPEG utilizes approximately
90 full time inspectors in the barrier zone (Darien Gap) of Panama along
the Panama-Colombia border to directly monitor animal health, visually
inspect and sample for both SW and vesicular diseases. In addition,
there are 40 inspectors working in the north and west of Panama in the
free zone to monitor livestock for both SW and FMD \[6, 7\]. The
inspectors visit the animal holdings and directly observe the animals
for clinical signs of SW and FMD, maintain a census of the number of
animal holdings and animals, record the numbers of animals observed for
clinical signs of FMD and SW, sample larvae from any suspect wounds and
report to the monitoring epidemiologist. Within the Inspection Zone, all
animal holdings are visited at least monthly by the local COPEG
inspectors. The inspectors also provide sample collection vials to
sample suspect larvae from wounds and distribute wound treatment powder
(5% Coumaphos, a topical organophosphate insecticide) to treat any open
wounds the animal owners may find. All samples, whether taken by the
inspector or the animal owner, are submitted for laboratory
identification.

Cattle and other species susceptible to FMD or SW may only leave the
Darien Province to go directly to an approved slaughterhouse. All
susceptible species leaving the control and inspection zones are subject
to visual inspection at both the movement control post and at the
slaughterhouse. The inspection process involves disembarking the animals
to allow visual observation for signs of FMD and SW. Documentation is
verified and placement of a sanitary seal on the shipment which is then
sent directly to the slaughterhouse. All animals arriving under this
seal are subject to mandatory inspection for FMD and SW at slaughter.

The USDA provides the sterile flies from a production facility in Tuxtla
Gutierrez, Chiapas, Mexico, until new production plant in Panama begins
production. Construction on the Panama Mass Rearing and Research
facility was begun in February, 2004, in Pacora, Panama, about 25 miles
east of Panama City and construction was completed in July 2007. The new
\$40-million, 210-acre facility will house more than 250 employees and
has the capacity to produce up to 150 million sterilized flies per week.
The new facility incorporates new technology to improve the efficiency
of the production process and enhance quality control. USDA\'s
Agricultural Research Service (ARS) Screwworm Research Unit (SRU) will
be consolidated from other locations and countries to the Pacora facilty
to provide continuing research support.

*Discussion*

Screwworm eradication in Panama was accomplished using the release of
sterile fly release method and establishment of a permanent biological
barrier that is maintained by continuous distribution of sterile SW
flies. The eradication program was the result of the cooperative efforts
of USDA and Panama through COPEG. Panama has an active disease control
and surveillance program and maintains the permanent biological barrier
with continuous distribution of sterile SW flies. SW is a reportable
disease in Panama requiring notification of authorities.

[]{#__RefHeading___Toc175129285 .anchor}**Vaccination status of the
region**

Vaccination is not an applicable control method.

[]{#__RefHeading___Toc175129287 .anchor}**Separation from adjacent
regions of higher risk**

The Darien Province forms the border between the Republic of Panama and
Colombia. This border is characterized by mountainous rainforest on the
Panamanian side and flat marsh and swamp on the Colombian side of the
border. This area is called the Darien Gap and is roughly 100 miles long
and 30 miles wide and is characterized by rocky coasts, mangrove swamps
with lowland and upland tropical forests. The remote nature of the
Darien Gap was first utilized over 40 years ago in the eradication and
control effort for FMD because it serves as a natural barrier to
dissemination of infectious diseases such as FMD.

The land supports very little agriculture and is sparsely populated
primarily by three Amerindian ethnic groups (Embera, Waunana and Kuna).
Much of this border is contained in the National Park Darien which is
the largest national park (579,000 Hectares = 2,235 square miles) in
Central America. United Nations Educational, Scientific and Cultural
Organization (UNESCO) declared the area to be a World Heritage Site in
1981 and a Biosphere Reserve in 1982. There are no major roads crossing
the Darien Gap connecting Republic of Panama and Colombia, including the
Pan-American Highway which does not cross this area preventing land
crossing from Central America to South America. Its natural physical
characteristics enhance its effectiveness for creation of the biological
barrier explained elsewhere in this document.

*Discussion*

APHIS finds that the natural and biological barriers of the Darien Gap
limit the movement of fertile SW flies or potentially affected animal
species from the South American continent into Panama effectively
controlling the risk of SW introduction into the Republic of Panama
outside of the permanent biological barrier.

[]{#__RefHeading___Toc175129289 .anchor}**Movement controls and
biosecurity from higher-risk regions**

In the Republic of Panama there is a comprehensive network of movement
control posts and 2 quarantine stations managed by COPEGs *Control de
Movilización de Animales* (CMA) and MIDA/DECA. Movement control posts
are for general animal movement control for FMD, vesicular diseases and
SW. All animals passing through these Movement Control Posts are checked
for documentation and visually inspected individually. All wounds are
examined, sampled and treated. Animals with suspect wounds may be
retained until a diagnosis is confirmed.

Figure 7. Location of COPEG Animal Movement Control Posts (puestos),
livestock auctions (subastas) and slaughterhouses (mataderos). \[8\]

![](media/image7.png){width="5.9847222222222225in"
height="4.332638888888889in"}

All species potentially affected by SW are visually inspected at the
movement control points. More than 500,000 animals have been inspected
at control posts in Panama since 2002 (see Table 1). The data from 2003
reflect the increased surveillance efforts involved following the
accidental release of sterile flies (see description in the Emergency
response capacity section).

Table 1. Annual inspection data for susceptible species passing through
control posts in portions of Panama outside the Inspection and Control
Zones. \[7\]

  -------------- ---------- ---------- ---------- ---------- ---------- -----------
  **Species**    **2002**   **2003**   **2004**   **2005**   **2006**   **Total**

  **Cattle**     66,159     102,006    73,073     72,949     64,432     378,619

  **Horses**     2,998      3,210      1,918      2,173      2,221      12,520

  **Swine**      22,741     23,442     23,320     24,106     7,093      100,702

  **Sheep**      16         1,684      455        319        281        2,755

  **Goats**      118        155        78         181        145        677

  **Buffalo**    0          112        64         48         19         243

  **Dogs**       107        1,658      276        717        218        2,976

  **Birds**      2,241      4,631      4,153      3,902      2,258      17,185

  **Cats**       0          0          0          9          3          12

  **Rabbits**    0          0          0          4          1          5

  **Other        0          92         38         17         4          151
  species**                                                             

  **Total**      94,380     136,990    103,375    104,425    76,675     515,845

  **Vehicles**   5713       44920      27807      47,456     47,168     173064
  -------------- ---------- ---------- ---------- ---------- ---------- -----------

\*source annual reports received 7/23/07

In nearby Kuna Yala Indian Reserve on the north coast (shown in purple
as Zona Atlantica in Figure 6) the inspectors and restrictions put in
place for FMD eradication have been maintained. In the Zona Atlantica
the same restrictions are applied as in the Control Zone of Darien; such
that only livestock for personal consumption are kept and all cattle
leaving the Darien Province may only go directly to COPEG monitored
slaughterhouses where they are subject to inspection. COPEG does
surveillance in the Inspection and Control Zones at 19 field
surveillance control posts staffed with 53 inspection officers
supervised by 3 veterinarians in Darien with additional posts in the
Kuna Yala Indigenous Area staffed by 8 officers. Samples from suspicious
wounds from the entire country are submitted for positive identification
(See Table 2).

*Discussion:* The movement controls established previously as part of
FMD legislation continue to be implemented and enforced by COPEG and
MIDA officials. These established movement controls limit the illegal
movement of livestock from the Inspection and Control Zones in Darien
Province and the Kuna Yala region into the rest of Panama. The
continuous monitoring of the permanent biological barrier in the Darien
Gap is a strong feature of the cooperative FMD and SW eradication and
prevention programs. The system of inspection posts and monitoring
throughout Panama significantly limits the risk of introduction and
spread of SW in Panama.

[]{#__RefHeading___Toc175129290 .anchor}**Livestock demographics and
marketing practices in the region**

Panama has a total human population of approximately 3 million with 45%
of the populations living in rural areas. More that 70% of Panamanian
exports are agricultural products, however, the vast majority of these
imports are plant products such as sugar and bananas**.** Nonetheless,
livestock raising (cattle, pigs, and poultry) is an important and
long-established economic activity in Panama, and beef and hides are
exported. Panama has about 1.5 million head of cattle on 40,000 holdings
\[9\]. Cattle are primarily raised in the southwestern provinces of
Chiriquí, Los Santos, and Veraguas. There are 300,000 swine on 28,000
holdings, located primarily in the central and western provinces of
Panamá, Los Santos, Chiriquí, and Veraguas. Cattle are only allowed to
be raised in the Control Zone area of Darien province where the cattle
population density is low and involves roughly 8% of the province, with
an estimated 0.9 animals per hectare. In the Inspection Zone area of
Darien province commercial cattle rearing is prohibited and agricultural
production is limited to swine raised for self-consumption.

The poultry population in Panama is approximately 14 million chickens on
150,000 holdings located primarily in the central provinces of Panamá,
Coclé, and Colón. There are an additional 200,000 turkeys, ducks, and
geese on 20,000 holdings throughout Panama as well as a small population
of horses and mules (135,000 head on 46,000 holdings), and sheep and
goats (12,000 head on 1,000 holdings) \[9\]. Few SW susceptible live
animals are exported.

*Discussion:* Currently, the export of live animals from Panama is not a
large part of the Panama's agricultural economy. SW larvae are not able
to survive in non-viable tissue so the importation of meat or other
animal products would not pose a risk for introduction of SW into the
US.

[]{#__RefHeading___Toc175129291 .anchor}**Disease surveillance in the
region**

Currently, both active and passive surveillance for SW is conducted
throughout all of Panama. Surveillance for SW outside of the Inspection
and Control zones is primarily the responsibility of MIDA through DINASA
in cooperation with COPEG. In the Inspection and Control Areas of the
Darien Province and the Kuna Yala and Emberá - Wounnan tribal reserves
in the eastern part of San Blas province, COPEG is directly responsible
for conducing surveillance.

Animals are inspected for the presence of SW at Movement Control points
throughout the country as well as at slaughterhouses, cattle auctions,
fairs and other exhibitions. In 2006, more than 76,000 animals were
inspected and more than 17,000 were found to exhibit a total of 25,720
wounds. Each wound was examined and treated. All wounds showing signs of
infestation (myasis) were sampled.

All cattle auctions in Panama are also actively monitored by CMA. In
2006, more than 98,000 animals were inspected, more than 7,000 presented
with wounds which were examined and effectively treated. Samples from
wounds were submitted for identification, none of which were identified
as SW \[8\]. Auctions were also used as points of contact with animal
owners to provide educational information and distribute wound treatment
powder.

In both the Inspection and Control areas active surveillance efforts
include frequent routine visits by COPEG personnel to all livestock
holdings. In the Inspection Zone inspections occur on a monthly basis
and in the Control Zone inspections occur at least several times a year.
The visits include education about SW and efforts are made to encourage
submission of larvae samples from wounds. In 2006 the inspectors did
more than 46,000 visits in the Inspection Zone Control Zones \[8\].

Table 2. Samples submitted for identification between 2002 and 2006, by
Province and Comarca. The numbers of positive samples are shown in
brackets \[7\].

  ------------------------- ---------- ---------- ---------- ---------- ----------
  **Province**              **2002**   **2003**   **2004**   **2005**   **2006**

  **Bocas del Toro**        9          11         12         9          7

  **Chiriquí**              41         34         23         92         77

  **Coclé**                 16         7          6          7          1

  **Colon**                 63         71 (27)    34         37         7

  **Comaraca Emera**        7          11 (9)                4          1

  **Comaraca Kuna Yala**    12         10 (3)     8          5          3

  **Comaraca Ngobe Bugle**  5          7          6          6          6

  **Darien**                106 (4)    344 (288)  34 (2)     71 (4)     45 (2)

  **Herrera**               12         13         8          12         10

  **Los Santos**            10         12         14         19         15

  **Panama**                76 (1)     257 (131)  75         76         60

  **Veraguas**              20         25         39         38         19

  **Total**                 **377      **802      **259      **376      **251
                            (5)**      (458)**    (2)**      (4)**      (2)**
  ------------------------- ---------- ---------- ---------- ---------- ----------

Samples from suspect wounds were submitted from all sections of the
country (see Table 2). The high numbers of samples submitted and found
positive in 2003 were the result of an accidental release of fertile
flies \[see emergency response section\] which affected areas outside of
the Inspection and Control Zones including the Provinces of Colon and
Panama. In 2005, four positive samples taken from two animals (i.e.,
represent only 2 positive cases) and in 2006 both positive samples were
from the same case.

It should be noted that no SW have been identified outside the
Inspection and Control Zones in Darien Province since 2002.

*Discussion:* The infrastructure developed for FMD surveillance has been
applied effectively to the SW eradication and control program. The
measures in place in the Inspection and Control Zones, which includes
the Darien Province and the Emera and Kuna Yala indigenous Comaracas,
are adequate to rapidly detect and eradicate SW and prevent the
reintroduction of SW into the rest of Panama. Submission of diagnostic
samples from all parts of Panama reflects both targeted surveillance
within the inspection and control areas and surveillance in the
livestock production areas. APHIS finds that the active surveillance
program in Panama is sufficient to detect the presence of SW if it were
to be reintroduced into Panama

**Diagnostic laboratory capacity**

The diagnosis of *Cochliomyia hominivorax* may be done by microscopic
examination of any of the larvae, pupae or adult stages. All suspect
larval samples collected in Panama are sent for microscopic
identification to the *Laboratorio de Larvas del Laboratorio de
Diagnóstico de Enfermedades Vesiculares* (LADIVES). LADIVES is located
in Río Tapia, Tocúmen, Panamá, and was established in 1982 for the FMD
eradication and prevention program with the cooperation of MIDA and
USDA. LADIVES also serves as the regional diagnostic laboratory for
Central America and is a cooperating lab for FAO and OIRSA. LADIVES has
Biosecurity Level 3 (BL-3) capabilities and has been ISO certified since
2004 (ISO: 9001-2000). Diagnostic results can be available within 24
hours to allow for rapid implementation of emergency measures if
necessary.

COPEG has field personnel trained to take samples and submit them for
identification. COPEG also has technically trained identifiers, capable
of identifying all the states of SW, in the production facility as part
of the Quality Control Department of the Dispersal Center and in other
local laboratories. As the SW program reached the end of the eradication
phase, the number of suspicious samples submitted to the central
laboratory *Cochliomyia hominivorax* has decreased.

Table 3. Samples submitted, by year \[7\]

  ------------- ------------ ------------- -------------------------------
  **Year**      **Total      **Total       **Total Positive Samples for
                Samples**    Negative**    *Cochliomyia hominivorax***

  **1998**      9,927        367           9,560 (96%)

  **1999**      5,743        743           5,000 (87%)

  **2000**      1,094        900           194 (18%)

  **2001**      1,066        1,017         49 (5%)

  **2002**      377          372           5 (1%)

  **2003**      802          344           458 (57%)

  **2004**      259          257           2 (\<1%)

  **2005**      376          372           4 (2 cases) (\<1%)

  **2006**      247          245           2 (1 case) (\<1%)
  ------------- ------------ ------------- -------------------------------

LADIVES has tracked the species identified in submitted samples since
2000. Seven other species have been identified with some frequency. The
majority of these were identified as *Dermatobia homini* (common names-
human bot fly, American Warble or Torsalo)*.* In 2005, 178 of the 392
samples submitted were *Dermatobia hominis* and in 2006, 140 of 247. The
most frequently identified species are *Phaenicia* spp. (bottle flies;
62 identified 2005 and 67 in 2004) and *Cochliomyia macellaria*
(secondary screwworm;71 were identified in 2005 and 54 in 2004) \[7\]*.*

*Discussion:* Laboratory diagnosis of SW in Panama is the responsibility
of the central LADIVES laboratory in Toucaman. APHIS considers Panama to
have the diagnostic capabilities to adequately diagnose the presence of
SW.

[]{#__RefHeading___Toc175129292 .anchor}**Emergency response capacity**

Panama has in place a contingency plan for SW outbreaks under the
supervision of COPEG. The emergency procedures and implementation is
based on the cooperation of COPEG, MIDA/DINASA and the public health
agency (National System for Sanitary Emergencies). The contingency plans
are supplemented by official instructions and guidelines detailing
procedures for disease notification and confirmation, sampling methods,
and diagnostic procedures. In compliance with ISO-9001 certification,
COPEG keeps their updated emergency plan and manuals on their website.

[]{.mark}

The emergency procedures are comprehensive and are designed for both SW
and FMD. The Emergency Committee (*Comité de Emergencia*) manages the
process in consultation with the Director General of COPEG to manage an
outbreak on the national level. COPEG secures and allocates the
necessary resources, as well as acts as a liaison with local regional
animal holdings and the media.

The emergency procedures define the roles and responsibilities of the
various supporting agencies for field activities and eradication,
including CMA, BPP, FVE and LADIVES. LADIVES provides laboratory support
in the area of the outbreak with the capability to immediately report
findings to the committee. An epidemiologic investigation is conducted
in the affected area under the direction of the Emergency Committee. The
directors of BPP and FVE are responsible for the initial activities in
the affected zone including providing trained personnel, supplies, and
conducts inspections of all animal holdings within a 5 Km radius of the
outbreak.

CMA establishes additional movement control points around the outbreak
area and preventive treatment to local livestock. Visits to all animal
holding in the affected and surrounding area are conducted to examine
animals for the presence of SW, educate the owners as to the presence of
SW in the area and distribute treatment and sampling supplies. The fly
release/distribution patterns are adjusted by the by the dispersal
center (*Centro de Dispersión*) to saturate the surrounding 25 square
mile area for a minimum of 6 to 8 weeks to eliminate the presence of
fertile SW flies.

[]{.mark}

The effectiveness of this emergency response was demonstrated in 2003
following the accidental dispersion of fertile flies. Shipments of flies
received between January 24 and 26, 2003 from the plant in Chiapas,
Mexico, were found to contain roughly one third fertile insects due to a
processing failure in the sterilization system. It is useful to note the
new plant in Pacora, Panama, will use a more advanced production
technology serving and improved quality control thereby decreasing the
future likelihood of producing or releasing fertile flies \[6\].

In response to the accidental release of fertile flies a General Alert
was called on January 30, 2003, followed by implementation of the
emergency campaign to bring the accidental infestation under control
(\"Operation Contention 2003\"). The General Alert was lifted after the
re-infestation was controlled on May 23, 2003. A total of 439 positive
cases of SW in livestock were diagnosed during this time period. With
the exception of a single case in a goat west of the canal, all the
cases were located within the area of accidental release. During the
General Alert the emergency plan was implemented with the participation
of 190 government officials from a variety of agencies \[7\].

The area dispersion of sterile flies was greatly extended to contain the
outbreak and eradicate the fertile SW. In addition to intensification of
release of sterile flies in the area where the accidental release
occurred, the area of sterile fly release was temporarily expanded west
of the canal into eastern portion of the Province of Coclé and
approximately 200 miles into Colombia \[7\].

Movement control and inspection measures were also increased during the
General Alert. Additional emergency check points were added to the
existing movement control posts; one near the International Airport at
Tocuman and the other in Gatún. During the General Alert 53,803 animals
and 18,088 vehicles were inspected. Increased control measures were
applied to animals leaving or entering the Control zone in Darién,
including increased surveillance of all animals moving to
slaughterhouses.

Figure 5. Location of positive screwworm diagnoses during 2003 General
Alert (in red). \[7\]

![](media/image8.jpeg){width="6.248611111111111in"
height="2.9784722222222224in"}

Visitation efforts were most intensive in the area extending from west
of the Panama Canal to the border with Colombia, to alert animal owners
of the accidental release of fertile flies and increase surveillance
efforts. These visits allowed for additional inspection and sampling, as
well as education and treatment efforts. Technical personnel inspected
all the properties in the potentially infested area, with over 18,000
visits occurring during the period of the General Alert with additional
technical visits during the remainder of 2003. The education efforts
included more than 1,500 meetings with animal owners and targeted
efforts in mass media with direct promotional materials in potentially
infested areas, including, bulletins, posters, pamphlets. General
education and dissemination of information was done throughout the
entire Republic of Panama as part of the General Alert.

The General Alert lasted a total of 114 days; however, 99% of the
positive samples were diagnosed during the first 40 days. This is a good
indication of the effectiveness of the surveillance component of the
emergency response effort and its rapid implementation. A total of 580
samples submitted during the time of the General Alert of which 438 were
positive. The last reported case of SW associated with the fertile fly
release was reported on May 19, 2003. Of the 438 positive samples, 280
were from the Province of Darien, 132 from the adjacent Province of
Panama and 27 from the Province of Colon, closely reflecting the
distribution pattern of the fertile flies. For all of 2003, a total of
797 samples were submitted of which 459 were positive. In the three
month period (June-August) following the General Alert, 120 samples were
submitted of which only 14 were positive. For the last 4 months of the
2003, 60 additional samples were submitted and only 4 of these were
positive.

Table 4. Sample history by month for 2003.

  ----------------- ----------------- ----------------- -----------------
  **Month**         **Total**         **NEG**           **POS**

  **Jan**           39                35                4

  **Feb**           474               56                419

  **Mar**           45                32                13

  **Apr**           20                19                1

  **May**           46                43                3

  **Jun**           35                32                3

  **Jul**           49                40                9

  **Aug**           36                34                2

  **Sep**           18                17                1

  **Oct**           13                13                0

  **Nov**           16                14                2

  **Dec**           9                 8                 1

  **2003**          **802**           **344**           **458**
  ----------------- ----------------- ----------------- -----------------

During the 2003 outbreak, cattle were the most frequently affected (296
cases or 67%). Swine (82 or 19%), horses (40 or 9%), dogs (16 or 4%) and
birds (3 or \<1%) were also affected. No human cases were reported. The
most frequently affected sites were the navels of newborns (32%),
injuries (lacerations and abrasoinsI, 20%) and surgical sites (such as
castration and dehorning, 15%) \[8\]. In 2004 the number of samples
submitted remained high as part of the increased surveillance effort. In
2004, the year following the accidental release of fertile flies, a
total of 253 samples were submitted with only 2 positively identified as
SW, representing less than 1% of samples submitted for the entire year.
Both of these positive samples were from the Darien Province.

*Discussion:* Panama has in place the infrastructure and legal authority
to declare an emergency and take appropriate action in case of a SW
outbreak. The emergency response capability was proven to be responsive
and efficient in 2003 following accidental release of fertile flies. The
emergency response plan is comprehensive and allows COPEG to respond
rapidly with extensive resources and utilizing the cooperation of
several government agencies to rapidly contain and eradicate the
accidental infestation. APHIS was unable to identify specific
limitations in this system that would pose a risk to the United States.

[]{#__RefHeading___Toc175129293 .anchor}**Release Assessment
Conclusions**

Based on the preceding assessment of the 11 factors specified in 9 CFR
92.2, APHIS has no evidence that SW currently exists in Panama. SW has
not been detected in domestic livestock outside the inspection zone
since 2003. Panama's current surveillance practices for SW are such that
an incursion of SW would be recognized and the veterinary infrastructure
is well trained and equipped to contain and eliminate an outbreak.

Panama shares a common land border with a region (Colombia) that APHIS
does not consider to be free of SW. Unlike previous eradication programs
that progressively eradicated SW southward from Mexico and the other
Central American countries, SW eradication in the Republic of Panama was
not accompanied by the implementation of a similar program in the
adjacent country of Colombia. However, the establishment and maintenance
of the permanent biological barrier in the Darien Gap region of Panama
serves to limit future incursions of SW from the South American
continent which APHIS considers to be endemic for SW. The establishment
and maintenance of the permanent biological barrier in the Darien Gap
has been the long term goal of the Central American SW eradication
program and is designed to identify and control incursions of SW from
South America.

The likelihood of introduction of SW into the US is limited to the
importation of live animals, as SW larvae survive only in living
tissues. Therefore, there is no risk associated with the importation of
commodities such as meat or animal byproducts. To pose a risk for US
livestock, an infested live animal would have to be imported, with the
infestation undetected and untreated, followed by the emergence of
viable larvae from the wound followed by burrowing of the larvae in
soil, pupate successfully under moderate temperatures, hatch out as
fertile adult male and female flies, mate successfully and deposit
fertile eggs in the wound of a domestic animal. The management practices
associated with the care of animals, specifically wound management,
would likely prevent viable larvae from maturing further mitigating the
risk of introducing SW in the US.

Live animals imported into the US are subject to inspection at the port
of entry (horses in 9CFR93.306, ruminants in 93.408, and swine in
93.507), at which time the presence of larva infested wound would most
likely be observed and treated with either topical or systemic agents.
In addition, on arrival in the United Sates horses and swine imported
from Panama are subject to quarantine; under 9CFR93.308 horses undergo a
seven day quarantine to observe for clinical signs of Venezuelan equine
encephalitis and under 9CFR93.507 all swine undergo a15 day quarantine.

APHIS finds that SW was successfully eradicated in Panama and an
effective prevention program is in place through the establishment and
maintenance of a permanent biological barrier in the Darien Gap. If SW
were reintroduced into the Panama, it would likely be detected and
contained before spreading. The maintenance and monitoring of permanent
biological barrier the Darien Gap is the responsibility of COPEG,
supported by the cooperative efforts of USDA and MIDA. APHIS concludes
that the likelihood of SW release into the US to be low.

[]{#__RefHeading___Toc175129294 .anchor}**Exposure Assessment**

An exposure assessment as defined by the OIE describes the biological
pathway(s) necessary for exposure of animals and a human in an importing
country to the hazards released from a given risk source, and estimates
the probability of the exposure(s) occurring \[12\]. Since APHIS\'
regulatory authority is limited to animal health, the potential risks to
animals are the primary focus of this evaluation.

APHIS considers that the most likely pathway of exposure of US cattle
and other species susceptible to SW is through contact with
infected/infested animals. Other more indirect exposure pathways, such
as through animal products, are not likely to result in
infection/infestation because the larvae of the SW do not remain viable
in other media except viable flesh.

**Imported live animals**

APHIS considers the most likely pathway of introduction in the US of SW
would be the importation of a live animal infested with SW larvae.
However, the survival period of SW larvae in the wounds of live animals
is relatively short, approximately 1 week, and SW larvae are readily
killed by routine wound management measures.

Following the successful eradication of SW in Panama and the
establishment and maintenance of the permanent biological barrier in the
Darien Gap adjoining the South American continent, APHIS concluded the
likelihood of exposure of susceptible U.S. livestock to SW from infected
live animals from Panama to be low. APHIS considers exposure of a
susceptible U.S. animal population to illegally imported infected live
animals from Panama to be unlikely.

[]{.mark}

[]{#__RefHeading___Toc175129296 .anchor}**Consequence Assessment**

A consequence assessment describes the biologic and economic
consequences of introducing the hazards under consideration into the
United States. This consequence assessment addresses both direct and
indirect consequences as recommended by the OIE \[12\].

The magnitude of the biologic and economic consequences following an
introduction of SW would depend on the location of the introduction,
time of the year of introduction, the rate of spread and whether other
environmental conditions at the introduction site that might facilitate
this spread, ability to detect the disease rapidly, demographics of
susceptible species, movement patterns and the ease of employing
eradication procedures. Direct consequences include effects of the
disease on animal health and the subsequent production losses, the total
costs of control and eradication, the effect on the environment, and
public health consequences. Indirect consequences including impacts on
international trade and associated domestic consequences are not likely
to result from an outbreak of SW because of the existing available
treatment options.

**Animal health consequences**

Many animal species, as well as humans, are susceptible to SW. The
severity of the disease depends largely on the degree of infestation and
health status of the animal, young animals usually more severely
affected than older animals. The most serious potential effects of SW
introduction would be on the cattle and sheep industries. An Australian
estimate done in 2002 found that untreated herds could have 10 to 15
percent of cattle infested at any one time with the greatest source of
loss from the death of newborn calves as a result of navel infestation,
which can be as high as 30 to 50 percent.

[]{.mark}

**Economic consequences**

The overall cost of control and eradication depends on the mitigation or
policy option chosen to control and eradicate the disease. Potential
costs include disease control measures such as imposing quarantine
measures and movement controls, and direct costs related to treatment of
affected and other herds, surveillance and laboratory testing, etc.

APHIS estimates that the U.S. livestock industry benefits of nearly
\$900 million a year as a result of the eradication of the SW in the
U.S. \[6, 14\].

In southwest Texas in l998, a rancher submitted larvae removed from a
wound on an Angora goat and one of these larvae was identified as that
of a SW by the National Veterinary Services Laboratory (NVSL) in Ames,
Iowa. As a result of this diagnosis more than 40,000 head of livestock
and dogs were inspected, however, no other indication of SW was found
before cold weather eliminated the potential for spread.

In an estimate made in 2002 by Australia it was found that if screw-worm
fly were to become established in northern Australia (the only area of
the country with an appropriate climate), it could cost more than \$400
million Australian dollars annually in lost production and control
measures. Any additional impact on humans, companion animals and
wildlife could also result from endemic screw-worm and have serious
implications for community health in the north of Australia.

[]{#__RefHeading___Toc175129299 .anchor}**Risk Estimation**

Risk estimation consists of integrating the results from the release
assessment, exposure assessment, and consequence assessment to produce
overall measures of risk associated with the hazards identified at the
outset. Thus, risk estimation takes into account the whole risk pathway
from hazard identification to the unwanted event \[12\].

APHIS concludes from the release assessment that there is no evidence
that SW currently exists in Panama. APHIS considers the likelihood of
introducing SW into the United States from Panama via export of live
animals to be low. APHIS concludes from the exposure assessment that the
probability of exposure of susceptible US livestock to SW via live
animals from Panama is very low. Conversely, APHIS concludes that the
animal health and economic consequences of a SW outbreak in the United
States could be some consequential because control and eradication
measures could be costly depending on the extent of spread and season of
the year.

In summary, although a SW outbreak in the United States would be likely
to have animal health and economic consequences, APHIS considers the
risk of infected live animals entering the US from Panama and exposing
US livestock to be low.

[]{#__RefHeading___Toc175129300 .anchor}**References**

1\. APHIS (1994) Cooperative Agreement between the U.S. Department of
Agriculture and the Panama Ministry of Agriculture and Livestock
Development for the Eradication and Prevention of Screwworms. Signed in
Panama City, Panama, on February 11, 1994.

2\. APHIS (2000) Interim Rule; Importation of Horses, Ruminants, Swine,
and Dogs; Inspection and Treatment for Screwworm \[Docket 00-028-1\].
U.S. Department of Agriculture, Animal and Plant Health Inspection
Service. Published November 13, 2000: 65 FR 67617-67624.

3\. APHIS (2001) Panama Cooperative Screwworm Eradication Program,
Environmental Analysis. U.S. Department of Agriculture, Animal and Plant
Health Inspection Service, Veterinary Services. Panama Cooperative
Screwworm Eradication Program, Environmental Analysis, July 2001

4\. APHIS (2002) Final Rule; Importation of Horses, Ruminants, Swine,
and Dogs; Inspection and Treatment for Screwworm \[Docket 00-028-2\].
U.S. Department of Agriculture, Animal and Plant Health Inspection
Service. Published March 15, 2002: 67 FR 11561-01165.

5\. APHIS (2002b). Screwworm Factsheet. U.S. Department of Agriculture,
Animal and Plant Health Inspection Service, Veterinary Services,
Emergency Programs.

6\. COPEG (2006). Panama- United States Commission for the Eradication
and Prevention of Screwworm Briefing Book.

7\. COPEG (2007). Panama- United States Commission for the Eradication
and Prevention of Screwworm. *Information in support of request for
recognition of screwworm free status for the Republic of Panama.*

8\. COPEG (2007) Panama- United States Commission for the Eradication
and Prevention of Screwworm; additional information provided (by email)
July 23, 2007.

9\. FAO (2001). United Nations Food and Agriculture Organization.
Agricultural Census.

10\. MIDA (2006). Ministerio de Desarrollo Agropecuario, Direccion
Nacional de Salud Animal. *Request for the Recognition as Free of
Screwworm.* Official MIDA request received from the Republic of Panama,
October 2006.

11\. OIE (2000). New World Screwworm (*Cochliomyia hominivorax*) and Old
World Screwworm (*Chrysomya bezziana*). *In* Manual of Standards,
Diagnostic Tests and Vaccines. Paris, World Organization for Animal
Health: Section 2.2.8.

12\. OIE (2006). Risk Analysis. *In* Terrestrial Animal Health Code,
14^th^ edition. Paris, World Organization for Animal Health: Section
1.3.

13\. OIE (2006). Health Standards, New World Screwworm (*Cochliomyia
hominivorax*) and Old World Screwworm (*Chrysomya bezziana*). *In*
Terrestrial Animal Health Code, 14^th^ edition. Paris, World
Organization for Animal Health: Section 2.2.8.

14\. Vargas-Teran, M., and H.C. Horrman, N. Tweddle (2005). Impact of
screwworm eradication programs using the Sterile Insect Technique. *In:*
Sterile Insect Technique. Principles and Practice in Area-Wide
Integrated Pest Management, V.A. Dyck & A. S. (Eds.). IAEA. Springer
Press: 630-647.

[^1]: Title 9, Code of Federal Regulations (9 CFR); SW affected
    countries are listed specifically in 93.301(j) horses; 93.405(a)(3)
    ruminants; 93.505 swine(b) and 93.600(a) dogs. 9 CFR 71.3(b) lists
    SW as a disease not known to exist in the United States.