[Emerging Infectious Diseases * Volume 3 * Number 2 * April-June 1997]

1st International Conference on Emerging Zoonoses

Epidemiology of Emerging Zoonoses in Israel

---------------------------------------------------------------------------

The epizootiologic, climatic, and ecologic conditions in the Middle East,
combined with socioeconomic and agricultural structures in Israel, have
created a unique and hazardous veterinary public health situation in this
country. In this paper, emerging zoonotic diseases are newly introduced
disease agents or endemic zoonoses whose previous epidemiologic patterns
have changed.

As of 1996, 15 zoonotic diseases of animals, anthrax, brucellosis,
cysticercosis (bovine), erysipelas, leishmaniasis (canine), leptospirosis,
listeriosis, malleus (glanders), psittacosis (chlamydiasis), Q fever,
rabies, Rift Valley fever (RVF), salmonellosis, trichinosis, and
tuberculosis (bovine and avian) (Table 1), have been declared notifiable in
Israel. When diagnosed in animals, these diseases are officially reported
to the state veterinary officers, who in turn report them to the medical
officers. Of these notifiable zoonoses, RVF has never been recorded in
Israel, and glanders has not been reported since 1951; ten are notifiable
in humans at the national level.

            Table 1. Selected zoonotic diseases in Israel, 1996
            ----------------------------------------------------
                                   Animal           Human
                                Year    Occur-    Year    Occur-
                             Notifiable rence  Notifiable rence
            ----------------------------------------------------
            Anthrax          1945       1993   1949       1984
            Brucellosis      1952       +++    1949       +
            Cysticercosis    1981       +      NN         +
            (bovine)
            Erysipelas       1945       (+)    NN         +
            Leishmaniasis    1945       ( )    1949       1994
            (canine)
            Leptospirosis    1945       +      1949       (+)
            Listeriosis      1961       +      1993       +
            Malleus          1945       1951   NN         never
            (glanders)
            Psittacosis      1952       +      NN         +
            Q fever          1952       +      1949       (+)
            Rabies           1955       +      1949       1960
            Rift Valley fever1978       never  NN         never
            Salmonellosis    1959       +++    1949       ++
            Trichinosis      1982       ( )    No         +
            Tuberculosis     1945       1993   1949
            (bov., av.)
            Botulism         NN         +      1993
            (types C,D)
            Echinococcosis   NN         ++     1980       (+)
            ----------------------------------------------------
            NN Not notifiable
            0000 Never reported
            - not reported, probably no occurrence
            Year Year of last occurrence
            (+) exceptional occurrence
            + low sporadic occurrence
            ++ enzootic/endemic
            +++ High occurrence

This article examines five of the reportable animal diseases whose
epidemiologic features have changed in Israel during the last decade:
Brucella melitensis in cattle, Salmonella enteritidis in poultry, rabies,
canine leishmaniasis, and trichinosis in wild boars. Two nonreportable
diseases in animalsbotulism in ruminants and echinococcosiswill also be
discussed briefly. (Table 1). Recently, the possibility that bovine
spongiform encephalopathy (BSE) may be a zoonotic disease has been
discussed worldwide. Thus, we also describe steps adopted by the Veterinary
Services and Animal Health (VSAH) to prevent the introduction of BSE into
Israel. The data on zoonotic diseases in animals are from VSAH's annual
reports to the Office International des Epizootics in Paris. If not
otherwise mentioned, the data on the diseases in humans are from the weekly
and monthly reports of the Ministry of Health in Jerusalem.

Brucella melitensis in Dairy Cattle

Bovine brucellosis is usually caused by Brucella abortus, less frequently
by B. melitensis, and rarely by B. suis. The disease is manifested by
abortion and excretion of the organisms in uterine discharges and in milk.
Brucellosis is highly pathogenic for humans, B. melitensis is regarded as
more pathogenic than B. abortus. B. melitensis is the main causative agent
of caprine and ovine brucellosis; it appears to occur mainly in the
Mediterranean regions, but infection occurs worldwide.

As of 1996, the dairy cattle of Israel, approximately 120,000 lactating
cows and 230,000 younger animals on 1,500 farms, are free of infection with
B. abortus. Since 1984, VSAH's ongoing, compulsory surveillance of all
farms has reported no cases of B. abortus. The surveillance includes
periodic bulk milk testing. In the event of a positive reaction, the test
is repeated on bulk milk from groups of cows, and the cows of a suspected
group undergo individual blood testing. Cows with positive test results are
slaughtered with full state compensations, and their organs are
bacteriologically examined in the State Reference Laboratory for
Brucellosis in the Kimron Veterinary Institute. In spite of the absence of
B. abortus, vaccinations of all 2- to 6-month-old dairy heifers with B.
abortus strain 19 vaccine has not been discontinued.

The status of B. melitensis in small ruminants, however, is different.
Brucellosis, which has been present in sheep and goat flocks (mainly in the
Bedouin sector) for decades, has increased considerably since the mid-1980s
A countrywide serologic survey was carried out during 1994-1995, in which
906 (10.1%) out of the 4,738 examined flocks were found infected. The total
number of reacting animals was 4,785 (3.16%) out of 151,409 examined sheep
and goats. Accordingly, a sharp rise in the occurrence of B. melitensis in
humans has been recorded from one case per 100,000 in 1983 to 11 cases per
100,000 (total 498 cases) in 1988 to 11 cases per 100,000 (total 498 cases)
in 1988. The most common sources of human infection are locally prepared
unpasteurized goat and sheep cheeses and milk (1).

An important phenomenon regarding B. melitensis in Israel is its
penetration into cattle herds. Until the late 1980s, these were mainly
small herds of locally bred Baladi beef cattle. In sporadic exceptional
cases, introduction of B. melitensis into dairy cattle farms was also
observed. Such a case was recorded for the first time in 1977 when raw
unpasteurized whey, a by-product of sheep cheese, from a central dairy
plant was fed to the lactating cows in one of the largest and finest dairy
herds in Israel, in the centrally situated Valley of Yezreel (2). The case
came to the attention of VSAH only after three dairy workers were
hospitalized with Malta fever. It took 2 years and the slaughter of 28 cows
for the herd to become disease-free again. According the VSAH "test and
slaughter" policy, all cattle in a farm where the seropositivity rate does
not exceed 50% are subject to monthly repeated serologic examinations.
Animals with positive test results are slaughtered, and compensations are
paid to the owners. The farm may be declared free of brucellosis, and
quarantine measures are discontinued after three consecutive negative
serologic tests of the entire herd. If more than 50% of the cows react
positively to the serologic test, the entire herd is slaughtered. Since
this incident, only pasteurized whey has been permitted as animal feed;
however, a second major outbreak occurred in late 1988, when cattle on a
dairy farm with 765 animals in western Galilee tested positive on the
periodic milk-ring test and was infected with B. melitensis (3).
Circumstantial evidence implicated contaminated whey from sheep or goat
milk as the most likely vehicle of infection. The epidemiologic
investigation was inconclusive, but researchers hypothesized that the
pasteurized whey could have been recontaminated when transported in tankers
not properly disinfected after having transported raw goat's milk. The
dairy herd was put under quarantine, and test and slaughter policies were
applied; implementation of these policies led to the compulsory slaughter
of 175 animals (23% of the herd). The farm was declared free of
brucellosis a year after the initial infection and two consecutive herd
tests with negative results. No human cases were involved. From this
outbreak, it could be concluded that vaccination of cattle with strain 19
vaccine did not confer adequate protection against infection with B.
melitensis, although it may have prevented abortions. These observations
were later supported by additional data from other outbreaks in dairy
cattle.

Since 1988, eight additional outbreaks of B. melitensis in large dairy
cattle farms throughout Israel have been recorded (Figure 1). The largest
outbreak occurred in 1994 when the entire cattle population (761 cattle) of
a large kibbutz dairy farm had to be slaughtered because the infection rate
exceeded 60%. In this outbreak, more than 30 members of the kibbutz
community, as well as the attending veterinarian, were infected, most by
direct contact with the infected cows or placenta and by the consumption of
unpasteurized milk. At present, an additional outbreak with human cases is
being investigated.

             [Figure 1] [Figures not available in ASCII version]
             Figure 1. Brucella mellitensis in dairy cattle,
             Israel 1988-1996.

The last eight outbreaks have been attributed to indirect contact with
infected nomadic sheep and goat flocks, which apparently contaminated the
pasture from which fodder was supplied to the lactating cows. Another route
of infection might have been dogs, most probably infected by consuming
infected placentas. Serologic examinations of dogs were carried out on two
of the farms, and antibodies were found in samples of 9 of the 39 dogs
tested. The infected dogs were then euthanized. It should be noted that
Israel is free of B. canis. The introduction of B. melitensis into dairy
cattle farms, a serious public health hazard, may be almost inevitable in a
highly contaminated environment.

Salmonella enteritidis

Salmonellosis is an infectious disease of humans and animals caused
primarily by intestinal bacteria of which 2,375 serovars are recognized, a
number constantly increasing. Salmonellosis appears to be most prevalent in
areas of intensive animal husbandry, especially of poultry or pigs. S.
enteritidis, especially of the phage-type TP4, emerged as a serious public
health hazard in Europe during the late 80s, mainly as a contaminant of
table eggs because of its transovarian infection in laying hens (4).
National programs have been implemented in some countries to control S.
enteritidis in poultry and protect the consumer.

Since the initial report from Europe, in 1988, of the emerging animal and
public health problem caused by S. enteritidis PT4 in poultry, Israeli
policy and activities have undergone a three-phase evolution:

1) 1988-1991: To prevent introduction of S. enteritidis, Israel implemented
strict quarantine conditions, including testing (serologic and
bacteriologic), on the import of breeding poultry, chicks, and hatching
eggs. From 1988 to 1991, 11 imported breeding flocks (five broiler
chickens, five laying chickens, one turkey), 103,100 birds, and 149,970
hatching (layer) eggs were found infected with S. enteritidis PT4 and
destroyed. The policy of strict border control of imported day-old chicks
and hatching eggs probably contributed to the delay in the appearance of
human infection until 1992.

2) 1992-1993: For the first time local breeding flocks were found infected
with S. enteritidis PT4 and destroyed along with their offspring laying
chick flocks. A surveillance program was implemented in the 200 local
breeding flocks. The program included bacteriologic examinations of dead
birds forwarded to the regional poultry disease laboratory, as well as
monthly visits of state poultry disease officers to each breeding farm for
sanitation control that included drag swab tests, sampling of caecal
contents for bacteriologic examinations, and in several flocks, rapid
slight agglutinations. Hatcheries were included as well. After the
surveillance, infected flocks (31 [10 broilers, 20 layer, one goose] which
comprised 272,188 birds and 2.8 million hatching eggs) were destroyed. The
state had to compensate the owners approximately 1.5 million U.S. dollars;
$300,000 in 1992, $1.17 million in 1993). "Competitive exclusion," a
preventive-curative technique developed in Finland and tried experimentally
on six breeding flocks produced inconclusive results (5). During 1992 and
1993, a significant increase in laboratory-contracted human cases of S.
enteritidis PT4 infection was recorded by the Ministry of Health: nine
cases in 1991, 203 in 1992, and 473 in 1993.

During 1993, to evaluate the S. enteritidis infection rate on commercial
farms, VSAH surveyed 88 broiler and layer breeding farms and found 18
(26.8%) of the 67 surveyed broiler breeder farms and 6 (28.5%) of the 21
layer breeder farms infected by direct cultures. In another investigation,
35 flocks of laying hens were examined in slaughterhouses, of which 12
(30.8%) were infected with S. enteritidis. Out of the said 10 isolates,
five were identified as PT4. In addition, 39 hatcheries throughout the
country were surveyed, of which 12 (30.8%) were infected with S.
enteritidis. These findings, combined with the alarming increase human S.
enteritidis infection rates, led to a reevaluation of the general policy,
which examined experience in other countries and local data. One of the
main decisions was to concentrate the efforts in the layer line and
discontinue the stamping out policy in the broilers line. The first step
was to prohibit the simultaneous incubation of layer- and broiler-hatching
eggs in the same hatchery.

The updated policy to concentrate and intensify the control efforts upon
the layers breeding stock while generally improving sanitary conditions in
all lines and to implement the control upon handling of table-eggs seems to
have contributed to the improvement of the public health situation
regarding S. enteritidis PT4.

3) 1994-
In 1993, after the publication of state regulations forbidding the
simultaneous incubation of layer and broiler hatching eggs, VSAH
discontinued intensive surveillance and, eventually, stamping out of
broiler breeding farms, to concentrate efforts on the layer line.
Consequently, the number of stamped-out broiler poultry flocks decreased
from 24 in 1993 to nine in 1994 to only one in 1995. VSAH implemented four
steps: a) Strict control of the layers breeding stock and hatcheries,
including bacteriologic examinations of meconium, offspring, and laying
birds and monthly sampling of drag swabs from the hatcheries and the
breeding farms; b) improvement of sanitary conditions in poultry farms; c)
introduction of an (inactivated) S. enteritidis vaccine, combined with the
live attenuated Salmonella typhimurium vaccine in parent-stock breeding
flocks; and d) enforcement of new state regulations regarding the handling
of table-eggs, their collection, transportation, packing, marking,
chilling, and marketing.

These measures were possible because of a single, centralized veterinary
system that combines modern diagnostic facilities, field activities, and
legal enforcement tools. The results of the measures described are
reflected in the number of reported human S. enteritidis isolates (Table
2).

       Table 2: Reported Salmonella enteritidis isolates in humans
       --------------------------------------------------------------
              S. enteritidis        S. enteritidis (PT4)
       --------------------------------------------------------------
       1989   357                   -
       1990   878                   -
       1991   987                   9
       1992   926                   203
       1993   1376                  473
       1994   1450                  750
       1995   997                   557
       --------------------------------------------------------------
       Furnished by Dr. Vered Agmon, Ministry of Health, Jerusalem.
       Preliminary figures for 1996 indicate that decline continues.

Rabies

Rabies, a major zoonosis caused by the neurotropic Lyssavirus,
transmissible to all mammals, occurs in all parts of the world. It is
especially prevalent in the temperate zones and where there is a large
canine population. Generally, in countries where the virus reservoir is
predominantly within the stray dogs which are the main vectors, the term
"urbanic rabies" is applied. On the other hand, when the reservoir is
mainly the wildlife population, the term "sylvatic rabies" is used. Urban
rabies predominates in Asia, Africa, and South America.

The evolution of rabies in vector animals, since 1948 is presented in Table
3. Annual vaccination of owned dogs became compulsory in 1957; vaccination
coverage is estimated at 60%. In 1979, rabies became sylvatic (involving
mainly fauna [foxes] rather than dogs) and remained so until 1990. A
transitory change was observed during 1991-92 when a sharp rise in the
number of rabid dogs converted the picture into "urban rabies" (dogs/fauna
ratio:2/1). This change, combined with the penetration of the disease into
the densely populated coastal region where rabies had been practically
absent for more than 30 years, could have been an outcome of the Gulf war
at the beginning of 1991 when many people (nearly 50% of the inhabitants of
Tel Aviv and other coastal cities) left their homes for safer areas during
the Iraqi missile attacks. Many of them abandoned their pets, establishing
a large stray-dog population. Subsequent steps to eliminate stray dogs may
have reversed the situation during 1992. Since 1993 (up to November 1996),
the pattern of predominantly sylvatic rabies has been reestablished.

 Table 3. Mean annual number of rabies cases in animals and humans,
 1948-1995
 --------------------------------------------------------------------------
                       Domestic          Wildlife
             No. of    animals                      Other  Fauna   Human
    Years     years   Dogs   Cats  Foxes  Jackals   fauna   (%)    cases
 --------------------------------------------------------------------------
 1948-1957   10      72.0   3.9   0.1     9.9      0.4     12.0   23
 1958-1966   9       19.4   0.9   0.3     0.8      0.1     5.6    2
 1967-1978   12      8.6    0.3   1.3     0.3      0.16    16.5   2
 1979-1990   12      6.2    0.25  12.6    1.25     1.3     70.1   0
 1991-1992   2       27.0   0     11.0    2        0       32.5   0
 1993-1995   3       14.25  1.25  35.25   4        4       72.2   0
 --------------------------------------------------------------------------

Rabies is practically endemic in most of Israel; clusters of rabies cases
in foxes are observed mainly in areas around the cities of Beer-Sheva,
Arad, Jerusalem, and Nazareth, but sporadic cases are scattered in other
areas (Figure 2).

             [Figure 2] [Figures not available in ASCII version]
             Figure 2. Rabies in fauna in Israel, 1992-1996.

The wildlife potentially involved with rabies comprises mainly foxes
(Vulpes vulpes) but in recent years, a significant increase in the number
of jackals (Canis aureus) has been observed in the central and northern
parts of the country. During 1995, 63 foxes and 14 jackals were tested at
the central rabies diagnostic laboratory at the Kimron Veterinary
Institute; 30 (47.6%) foxes and 2 (14.3%) jackals were infected. The
figures for 1996 are similar. Other wildlife species, involved with rabies
are the mongoose (Herpestes ichneumon ichneumon), badgers (Meles meles
canescens), and the stone marten (Martes foina syriaca). During 1986 to
1996, rabies was diagnosed in 251 foxes, 31 jackals, four mongooses, four
badgers, and three martens, which were sent to the Kimron Veterinary
Institute. The actual incidence of the disease was much higher. In view of
the growth of the jackal population, rabiesif spread within that
speciesmay increase considerably the already serious threat to humans and
farm animals. Recently, seven cattle herds in northern Israel were found
infected, more than twice the mean annual number for decades. This might
reflect the increased rabies incidence among the extremely dense
populations of foxes and jackals in that region.

Oral vaccination of wildlife in Israel has been considered, but vaccine and
baits evaluation is still in its experimental stages. At any rate,
vaccination will only be practical if it is effective for both foxes and
jackals and involves entire ecologically related regions (the West Bank,
the Jordan Valley, and probably the western parts of Jordan and southern
Lebanon).

Canine Leishmaniasis

Canine leishmaniasis is a chronic viscera-cutaneous disease caused by
Leishmania infantum (in the Old World), of which the dog acts as the source
reservoir. The vectors of leishmaniasis are phlebotomine sandflies
belonging to the genera Phlebotomus (Old World) and Lutzomyia (New World).

Canine leishmaniasis was common before 1948 but seemed to disappear after
that. Since 1955, no cases have been reported in dogs. However, four human
cases of visceral leishmaniasis (Kala-azar) (two in 1980 and two in 1982)
were reported by the Ministry of Health in two restricted areas in eastern
and western Galilee. The disease became regarded as endemic in these areas,
although no canine cases were detected there.

From January 1995 through November 1996, 30 clinical cases of canine
leishmaniasis were reported from five communities in the Judean hills
northwest of Jerusalem and from one location in western Galilee (Figure 3).
Diagnosis was carried out by the Koret Veterinary School and the Kuvin
Center of the Hebrew University, which reported that the cases were caused
by L. infantum (G. Benet, pers. comm.).

             [Figure 3.] [Figures not available in ASCII version]
             Figure 3. Canine Leishmaniasis in Israel,
             1995-1996.

Trichinosis

Trichinosis is a parasitic disease. Human infections are established
through the consumption of insufficiently cooked pork infected with the
causative nematode Trichinella spiralis.

No cases of trichinellosis (trichinosis) have been recorded in domestic
pigs in Israel since 1948, though a substantial number of pigs are
slaughtered (more than 100,000 in 1995) and each batch is sampled for
representative microscopy examinations. In light of the accumulated data
about the absence of infection in the housed pigs, the sample rate is
limited. Trichinosis in animals was declared notifiable in 1982 when its
potential hazard was reflected by the admission to Israeli hospitals of 20
clinically infected persons from southern Lebanon, close to the northern
Israeli border.

According to a state regulation published in 1977, the entire carcass of
hunted wild boars should be presented to accredited veterinary inspectors
at specified inspection stations. Until 1991, 100-200 such carcasses,
approximately 10% of the actual number of killed boars, were annually
presented for microscopy examinations without detecting any infections.
However, in 1992, hunters from northern Galilee were hospitalized with
symptoms of acute trichinosis after eating pork derived from game.
Consequently, public awareness of the disease grew, and the number of
samples from wild boars submitted for laboratory examination increased two-
to three-fold from previous years. In May 1992, the first case was found in
a wild boar from the Lebanese frontier, followed by 19 additional cases
between 1993 and 1996, all in wild boars shot in three areas: (upper
Galilee; central and western Galilee, and the Carmel Hills). By October
1996 alone, no fewer than nine cases of trichinosis were diagnosed.(see
footnote) According to the Animal Diseases Regulations, carcasses of
animals found infected are condemned; no alternative measures, such as
cooking or freezing, are officially permitted.

    Footnote. Dr. John Wortabet (1827-1908), an Armenian-Lebanese
    physician who worked in the St. John Hospital in Beirut and
    lectured in the medical college there during the second half of
    the 19th century diagnosed trichinosis in humans in south Lebanon
    during a massive outbreak in the village of El-Chiam in November
    1880more than 115 years ago. His exemplary observations about the
    outbreak, which involved 262 cases, including six deaths, were
    published in Lancet (6). A second outbreak, in the Northern Golan,
    was reported by Dr. Wortabet in Lancet (4 August 1883). In this
    outbreak, 40 inhabitants of the village Ein-Kinya, were infected
    after consuming raw pork from a wild boar. However, in this
    outbreak, no deaths were recorded. His footnote, at the end of the
    report, is still timely: "From personal observation and experience
    I have found the use of pork in Syria decidedly unhealthy. The
    wild boar in winter is a delicacy, but unless previously examined
    with the microscope, according to German law, or cooked more
    thoroughly than is usually done, its use cannot be free from the
    danger of communicating trichinae to man." Data about Dr. Wortabet
    courtesy of Drs. Mertyn Malkinson and Arieh Sheskin.

Botulism

Botulism is a highly fatal toxemia caused by ingestion of the toxin of
Clostridium botulinum. There are eight types and subtypes of Cl. botulinum,
of which types A, B, and E are of most importance in human botulism; types
C and D affect farm animals, mainly cattle, horses, chickens, and sheep.

In 1978, a major outbreak of botulism (type D) caused the deaths of many
dairy cattle and small ruminants from farms in central and northern Israel
(7). Spores of Cl. botulinum type D, as well as the toxin itself, spread to
many farms from two central animal feed plants by recycled poultry manure
that included remains of avian cadavers and was not properly sterilized.
Many farms are suspected to have been contaminated by the spores through
the centrally produced and countrywide distributed infected feed.
Consequently, annual botulism vaccinations of cattle and of other
vulnerable animals with a vaccine, including toxoids of Cl. botulinum types
C and D adsorbed onto aluminum hydroxide gel, are conducted in most parts
of Israel. Sporadic cases involving unvaccinated animals (mainly young
cows) occur every year, along with an exceptionally large number of
outbreaks, (23) recorded in 1995, found by the Kimron Veterinary Institute
to be caused by botulism type D. In all these cases, poultry manure was the
suspected source of intoxication.

Although botulism types C and D are not generally regarded pathogenic to
humans, it has recently been decided to prohibit the release of meat from
ruminants with suspected cases for human consumption.

Echinococcosis

Echinococcosis, also called hydatid disease, is caused in humans by
ingestion of eggs of the cestode Echinococcus, of which the most
predominant and epidemiologically significant is Echinococcus granulosus.
The adult tapeworm is carried by dogs and other carnivores. The
intermediate hosts in which the cystic forming larval stage develops
include various food animals and humans. The infection cycle is maintained
by the availability of infected organs to carnivore hosts. Data from
slaughterhouses show that the countrywide infection rate per 1,000 animals
in 1995 was 0.9 for cattle and 39.9 for sheep (8).

In 1981, human hydatid disease was declared notifiable by the Ministry of
Health. During 1991 to 1995, 38 human cases were officially recorded in the
country, but the actual number is much higher. For example, El-On et al.
(9) conducted epidemiologic studies in 1988 in the town of Yirka, a
semirural Druze community of 8,200 persons in northern Israel, and found a
cumulative percentage of confirmed present or recent past hydatid
infections of 12 (1.6%) of 758, leading to an extrapolated rate of 1,583
per 100,000 persons, which is comparable with that in hydatidosis-endemic
areas worldwide. This remarkable situation could be explained by four
combined factors: 1) High infection rates in sheep and goats (10%); 2)
high infection rates in owned dogs (14.2%); 3) widespread practice of
illegal slaughter of sheep and goats, performed without veterinary
inspection and followed by uncontrolled disposal of the infected slaughter
offal; and 4) a large number of hunting dogs kept at the homes of many of
the Druze people, who traditionally hunt.

The prevalence of hydatid disease in neighboring Moslem villages was lower,
mainly because of the smaller number of dogs kept at homes and the general
aversion in the Moslem community to any contact with dogs.

Israel's Measures to Prevent the Introduction of BSE

BSE, a fatal neurologic disease of adult cattle first discovered in the
United Kingdom in 1986, is one of the transmissible spongiform
encephalopathies caused by unconventional agents extremely resistant to
heat and chemical treatments.

Israel has adopted the following rigorous steps (taken since the very first
announcement of the new disease in the United Kingdom) to prevent the
introduction of BSE and to safeguard early detection of eventual occurrence
of the disease in the local livestock:

  1. State veterinarians, farm animal practitioners, slaughterhouse
     veterinarians, and cattle breeders associations were notified and
     updated by a) articles and updates in the monthly Veterinary Bulletins
     (more than 350 items since December, 1987; b) workshops and lectures,
     central and regional, some of them with participation of British
     experts and demonstration of British videotaped clinical BSE cases;
     circulars, including detailed descriptions of clinical BSE
     epidemiology and symptoms.
  2. The import of meat and bone meals, derived from ruminants from the
     United Kingdom was banned since December 1988, and from all other
     countries since July 1990.
  3. BSE was declared an officially notifiable disease in 1992.
  4. A pathologist from the Kimron Veterinary Institute was trained in
     contemporary diagnostic techniques at the Central Veterinary
     Laboratory, Weybridge, United Kingdom (October 1992).
  5. Since 1993, bovine brains presented to the Kimron Veterinary Institute
     after any CNS-related symptoms, are histopathologically examined for
     BSE changes. During 1993-1996, 583 brains (1993, 72; 1994, 134; 1995,
     167; 1996, 210) were examined, all found negative. Most of the brains
     were of bovines older than 2 years. This sample size exceeds the
     number of brains to be examined annually to detect BSE on a country
     level, as recently recommended by the Office International des
     Epizootics. The recommendation was to examine a minimum of 50 brains
     annually if the national cattle population, 209 months of age or
     older, is up to 500,000 and 91 brains if the cattle population is
     1,000,000. The Israeli cattle population of said age group is less
     than 250,000.
  6. In April 1996, an interministerial BSE expert advisory panel was
     established to recommend new/updated steps for BSE
     prevention/monitoring.Detailed recommendations were presented in July
     1996, most of which are already adopted.
  7. The panel paid special attention to the import conditions for meat and
     offals. This issue is related to the documented presence in Israel, of
     a considerable population-cluster that may be exceptionally vulnerable
     to transmissible spongiform encephalopathies. Accumulated scientific
     evidence indicates that this population, composed mainly of Jewish
     persons of Libyan and Tunisian origin, demonstrates a genetically
     linked susceptibility to CJD, probably related to a codon 200 mutation
     (10). This is expressed by an annual CJD incidence of nearly 100 per
     million, compared to less than 1 per million in the general population
     (E. Kahana, pers. comm.). Probable enhanced vulnerability of these
     persons, if exposed to the BSE agent, cannot be ruled out.
  8. Another recommendation referred to adding immunohistochemistry and
     immunoblotting techniques to the routinely used conservative
     histopathologic examination of BSE and further increasing the number
     of examined bovines.
  9. CJD was declared a notifiable disease in humans by the Ministry of
     Health in June 1996.
 10. Since August 1996, the feeding of farm animals, including poultry and
     fish, with meat and bone meals derived from mammals has been
     officially banned.
 11. Imported meals from poultry or fish origin are systematically examined
     at the port of entry to confirm the obtained written certification
     regarding the absence of mammalian ingredients.

The emergence of zoonotic diseases in Israel may be due to unique
epizootiologic, climatic, and ecologic conditions in the regions as well as
specific conditions within the country.

Nomadism, prevalence of disease carriers and their vectors, close proximity
of ultramodern farms housing susceptible livestock of exotic breeds or
their crosses to traditionally maintained flocks of disease-endemic breeds,
and dense overpopulated protected wildlife are the major contributing
factors to emerging zoonoses. But the cardinal factors predominant in the
Middle East are the need for improved veterinary infrastructure, direct
information exchange, and cooperation between the countries of the region.

Out of the seven diseases we reviewed, at least four, brucellosis, rabies,
leishmaniasis, and echinococcosis, can be effectively controlled only if
cooperation and animal health information systems are established on a
regional level.

The assistance of the international community to the establishment of
regional veterinary cooperation in the Middle East is of great importance.

Acknowledgements

Thanks to Dr. Van Ham of the Department of Epidemiology, Veterinary
Services and Animal Health, Beit Dagan, Israel, for the maps used in this
article.

Arnon Shimshony
Veterinary Services and Animal Health, Beit Dagan, Israel

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Emerging Infectious Diseases
National Center for Infectious Diseases
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Updated: 97/05/14