Emerging Infectious Diseases
[Volume 5 No.2 / March - April 1999]

Letters

An Outbreak of Gastroenteritis in Japan due to Escherichia coli O166

To the Editor: Enteroaggregative Escherichia coli (EAggEC) heat-stable
enterotoxin 1 (EAST1) was originally found as an enterotoxin of EaggEC (1).
Recently, Yamamoto et al. (2) reported that the EAST1 gene, or its
variants, were present not only in EAggEC but in other diarrheagenic E.
coli, including some enteropathogenic E. coli (EPEC) and enterotoxigenic E.
coli (ETEC). Hedberg et al. (3) found that an outbreak of gastrointestinal
illness in 1991 had been caused by EAST1-producing E. coli that possessed
the EPEC gene locus for enterocyte effacement. We propose that E. coli
producing EAST1 but possessing no other identifiable pathogenic properties
may compose either a new group of diarrhea-associated E. coli or a new
subgroup of ETEC.

In an outbreak of gastroenteritis on July 23, 1996, in Osaka, Japan, 54 of
91 persons attending a meeting held in an office building on July 22, 1996,
became ill. The patients did not eat any common foods except the lunch
served at the office. Symptoms were diarrhea in 52 (96%); abdominal pain in
32 (59%); nausea in 8 (15%); fever in 8 (15%); and vomiting in 5 (10%). The
mean incubation period was 17 hours.

Stool specimens of 33 patients were examined, and E. coli O166 with an
unidentifiable H antigen were isolated from 29 specimens. Laboratory tests
for other bacterial pathogens and viruses were negative. The isolates
showed the same DNA banding pattern in pulsed-field gel electrophoresis
after treatment with the restriction enzymes Xba I or Not I.

The E. coli O166 organisms did not adhere to HEp-2 cells in a localized,
diffuse, or enteroaggregative manner and did not give mannose-resistant
hemagglutination of human or bovine red blood cells. Although the organisms
were further analyzed for expression of known ETEC colonization factors by
a dot-blot assay using specific monoclonal antibodies, they did not express
CFA/I, CS1, CS2, CS3, CS4, CS5, CS6, CS7, CS17, PCFO159, PCFO166, or
CFA/III. In polymerase chain reaction (PCR) tests, the bacteria did not
have coding genes for verocytotoxin of enterohemorrhagic E. coli,
heat-labile, or heat-stable enterotoxin of ETEC, attachment and effacement
(eaeA) of EPEC, or invasion (invE) of enteroinvasive E. coli. Consequently,
they are not assigned to any of the recognized diarrheagenic groups of E.
coli: EPEC, ETEC, enterohemorrhagic E. coli, enteroinvasive E. coli,
EAggEC, and diffusely adhering E. coli. According to the PCR method of
Yamamoto et al. (2), however, the organisms possessed the EAST1 gene.

To our knowledge, this is the first report of an outbreak caused by
EAST1-producing E. coli that did not have other well-characterized
virulence genes. We believe that these strains should be assigned to a new
subgroup of ETEC. Such strains would not be detected in most current
surveys for diarrheagenic E. coli, as tests for EAST1 are rarely included.
The role of EAST1 in pathogenicity has been controversial. We propose that
diarrheal specimens be examined for EAST1-producing E. coli so that the
distribution of these organisms worldwide can be determined.

Yoshikazu Nishikawa,* Jun Ogasawara,* Anna Helander,  and Kosuke Haruki*
*Osaka City Institute of Public Health and Environmental Sciences, Osaka,
Japan; Gteborg University, Sweden

Acknowledgment

We thank Sylvia M. Scotland, who retired from the Laboratory of Enteric
Pathogens, Central Public Health Laboratory, London, for her critical
review of the manuscript.

References

  1. Savarino SJ, Fasano A, Robertson DC, Levine MM. Enteroaggregative
     Escherichia coli elaborate a heat-stable enterotoxin demonstrable in
     an in vitro rabbit intestinal model. J Clin Invest 1991;87:1450-5.
  2. Yamamoto T, Wakisaka N, Sato F, Kato A. Comparison of the nucleotide
     sequence of enteroaggregative Escherichia coli heat-stable enterotoxin
     1 genes among diarrhea-associated Escherichia coli. FEMS Microbiol
     Lett 1997;147:89-95.
  3. Hedberg CW, Savarino SJ, Besser JM, Paulus CJ, Thelen VM, Myers LJ, et
     al. An outbreak of foodborne illness caused by Escherichia coli
     O39:NM, an agent not fitting into the existing scheme for classifying
     diarrheagenic E. coli. J Infect Dis 1997;176:1625-8.

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

Vibrio cholerae Outbreak in Italy

To the Editor: On 16 June, the microbiology unit of the Hospital of Lodi
communicated to the local public health unit that Vibrio cholerae had been
isolated and identified by standard biochemical tests in stool samples of
an outpatient whose clinical data were unknown. On the same day, we
contacted and interviewed the patient to investigate risk factors for
cholera. The patient reported abdominal pain starting on 6 June and then
severe diarrhea (10 to 12 stools per day) until 13 June; on that day the
patient went to his general practitioner, who gave him loperamide and
suggested a coproculture. The patient never traveled to cholera-endemic
areas; did not eat raw mussels, uncooked fish, or vegetables of uncertain
origin or from cholera-infected areas; and did not swim in rivers or lakes.
The patient reported that he ate a seafood salad in the canteen of his work
place on 5 June and that three out of the four persons who ate the same
kind of salad also had abdominal symptoms. Subsequently, the Istituto
Superiore di Sanit (ISS) in Rome confirmed isolation of toxinogenic V.
cholerae O1, biotype El Tor, serotype Ogawa, from stools from the index
patient.

The canteen where the index patient had eaten the seafood salad was 1 of 17
supplied by a single cooking center that used a precooked, frozen,
ready-to-eat product including shrimps, scallops, mussels, hen clams,
cuttlefishes, and squid. Each product was cooked and frozen in the country
of origin and mixed in Italy by an importer who packaged the seafood salad.
Tracking the products around the world was difficult, but we learned that
at least some had come from Far East countries where cholera is endemic.
Approximately 125 servings of the same food were distributed within our
local public health area (Azienda Sanitaria Locale) and more than 400 in
other areas.

We performed an epidemiologic case-control investigation beginning 18 June
involving 454 persons (94 who had eaten the seafood salad and 360 controls
who had eaten in the same canteen any food except seafood salad); 37 (39%)
of the persons who had eaten the seafood salad had had at least one episode
of diarrhea or other relevant gastrointestinal symptoms, as compared to one
(0.3%) of those who had not eaten it. We did not find symptomatic patients.
The corresponding odds ratio was 233 (95% confidence interval, 97 to 560).
No symptomatic person had to be hospitalized because of symptoms or
required intravenous treatment; three or more loose or watery stools during
a 24-hour period were reported in 24 cases. We performed coprocultures
(using TCBS medium) between 23 June and 3 July of all 94 persons who had
eaten the seafood salad. One positive coproculture for V. cholerae O1 Ogawa
(same strain) was identified on 25 June; the isolation was subsequently
confirmed by the ISS. This second patient with a positive culture worked in
a factory in a different town. She had severe diarrhea on 6, 7, and 8 June.
Her family doctor gave her rifaximin but did not ask for a coproculture,
but a specimen was obtained on 23 June. She did not report risk factors for
cholera infection, except having eaten seafood salad on June 5 in the
canteen of her work place. The delay between exposure to V. cholerae and
the coprocultures was longer than 1 week (median delay 26 days, range 19 to
31), and it is therefore not surprising that others who had eaten the
seafood salad did not have positive results. Both the culture-positive
index case-patient and the woman were recultured three more times; negative
results were obtained.

The identification of this cholera outbreak is a sentinel episode
confirming (1,2) that, if not adequately monitored, food preparation and
distribution can cause serious infectious diseases in industrialized
countries.

Luca Cavalieri d'Oro,* Elisabetta Merlo, Eugenio Ariano, Maria Grazia
Silvestri, Antonio Ceraminiello, Eva Negri,* and Carlo La Vecchia*
*Istituto di Ricerche Farmacologiche "Mario Negri," Milan, Italy; Azienda
Sanitaria Locale della Provincia di Lodi, Lodi, Italy; and Universit
degli Studi di Milano, Milan, Italy

References

  1. Centers for Disease Control and Prevention. Cholera associated with
     food transported from El SalvadorIndiana, 1994. MMWR Morb Mortal Wkly
     Rep 1995;44:385-6.
  2. Centers for Disease Control. Cholera associated with imported frozen
     coconut milkMaryland, 1991. MMWR Morb Mortal Wkly Rep 1991;40:844-5.

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

Shiga ToxinProducing Escherichia coli O157:H7 in Japan

To the Editor: Shiga toxin-producing Escherichia coli (STEC) O157:H7
infection, which can cause hemolytic uremic syndrome and death, is a global
public health concern. Patients younger than 5 years of age are at high
risk for hemolytic uremic syndrome (1) and shed the organism longer than
adults (2). The public health importance of this symptomatic shedding in
transmission among preschool children is well established (3); however,
that of symptom-free shedding in adults is unknown. We report here that the
rate of symptom-free STEC O157:H7 shedding is higher in adults 30 to 49
years of age than in others.

STEC infections have been notifiable in Japan since August 1996. When STEC
is found in the feces of patients in schools, families, and hospitals,
local health centers and public health institutes must test (generally
using MacConkey sorbitol agar with cefixime-potassium tellurite medium) for
the pathogen in stool specimens of contacts of the patients. The pathogen
is also sought twice a month in the stool specimens of food-handlers. All
isolates from culture-positive patients are collected by Japan's National
Institute of Infectious Diseases.

In 1997, 1,412 STEC O157:H7 human isolates were examined for subtyping of
Shiga toxin genes stx1 and stx2 by polymerase chain reaction, for
genotyping by XbaI-digested pulsed-field gel electrophoresis (PFGE) (4,5),
and for their relationship with symptoms; 1,381 isolates (from
culture-positive persons with well-characterized clinical status) were
further analyzed. The rates by age group among STEC O157:H7-shedding
persons reporting one or more symptoms (vs. culture-positive persons
without symptoms) were as follows: 82% (475 of 576) younger than 10 years
old; 81% (145 of 178), 10 to 19 years; 63% (98 of 156), 20 to 29 years; 25%
(32 of 128), 30 to 39 years; 34% (34 of 100), 40 to 49 years; 54% (57 of
106), 50 to 59 years; 56% (38 of 68), 60 to 69 years; 68% (47 of 69), older
than 70 years. Culture-positive persons under 20 years of age, especially
children under 10 years of age, were more likely to have symptoms than
other age groups. Intermediate rates of symptom-free persons with positive
stool cultures occurred in young adults (20 to 29 years of age) and the
elderly (70 years of age), while the highest rates of stool-positive,
symptom-free persons were adults, especially those between 30 and 49 years
of age. In terms of pathogen virulence, we did not find significant
differences in the distribution of stx subtypes and PFGE genotypes between
strains shed by symptomatic and asymptomatic persons. These results suggest
that the rate of symptom-free STEC O157:H7 shedding may be associated with
age rather than organism-related factors. Possible age-related host factors
that could influence the presence of STEC O157:H7 in the stools of
symptom-free persons include qualitative and quantitative differences in
intestinal cross-reactive antibodies against STEC O157:H7, intestinal
bacterial flora, or the sensitivity to Stx toxins between children and
adults. Further investigations will be required to determine the relative
importance of these and other host factors. Our finding of a high rate of
asymptomatic shedding in adults may suggest the potential for secondary
transmission of the bacteria from symptom-free STEC O157:H7-shedding adults
to healthy children.

Acknowledgments

We thank investigators of prefectural and municipal public health
institutes for their collaboration.

This work was supported by a grant from the Ministry of Health and Welfare
of Japan.

Jun Terajima, Hidemasa Izumiya, Akihito Wada, Kazumichi Tamura, and Haruo
Watanabe
National Institute of Infectious Diseases, Tokyo, Japan

References

  1. Tarr PI. Escherichia coli O157:H7: clinical, diagnostic, and
     epidemiological aspects of human infection. Clin Infect Dis
     1995;20:1-8.
  2. Belongia EA, Osterholm MT, Soler JT, Ammend DA, Braun JE, MacDonald
     KL. Transmission of Escherichia coli O157:H7 infection in Minnesota
     child day-care facilities. JAMA 1993;269:883-8.
  3. Karch H, Russman H, Schmidt H, Schwarzkopf A, Heesmann J. Long-term
     shedding and clonal turnover of enterohemorrhagic Escherichia coli
     O157:H7 in diarrheal diseases. J Clin Microbiol 1995;33:1602-5.
  4. Watanabe H, Wada A, Inagaki Y, Itoh K, Tamura K. Outbreaks of
     enterohaemorrhagic Escherichia coli O157:H7 infection by two different
     genotype strains in Japan. Lancet 1996;348:831-2.
  5. Izumiya H, Terajima J, Wada A, Inagaki Y, Itoh K, Tamura K, et al.
     Molecular typing of enterohemorrhagic Escherichia coli O157:H7
     isolates in Japan by using pulsed-field gel electrophoresis. J Clin
     Microbiol 1997;35:1675-80.

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

Streptococcus pyogenes Erythromycin Resistance in Italy

To the Editor: Streptococcus pyogenes resistance to erythromycin began to
emerge as a serious problem worldwide in the early 1990s. In some areas in
Italy, 30% to 40% of strains have beome resistant (1-3). Throughout Italy,
the use of macrolides, particularly the newest ones (azithromycin and
clarithromycin), has increased in the treatment of infections caused by
Group A streptococci. This therapeutic approach is contrary to current
guidelines, which recommend using betalactam antibiotics as first-choice
therapy and reserving macrolides only for patients allergic to betalactams.

In 1997 in Finland, a decrease was observed in the use of macrolide
antibiotics in ambulatory patients from 2.40 defined daily doses per 1,000
inhabitants in 1991 to 1.38 in 1992. Subsequently, the maintenance of doses
at 1.28 to 1.74 defined daily doses resulted in a substantial decrease in
the percentage of group A streptococcal resistance to erythromycin,
reported as 16.5% in 1992, 19% in 1993, 15.6% in 1994, 10% in 1995, and
8.6% in 1996 (4). These data prompted us to evaluate such phenomena in our
geographic area, the urban area of Genoa, Italy (approximately 120,000
inhabitants).

From January 1991 to June 1998, 311 (6.1%) of 5,117 strains of S. pyogenes
throat swabs from patients with pharyngotonsillitis were isolated. We
observed a higher number of group A streptococci isolates from throat swabs
starting in 1996 than we had in 1991 to 1995 (chi-square = 35.653, p
<0.0001). All isolates were tested for susceptibility to penicillin and
erythromycin by standard susceptibility tests (broth microdilution) as
recommended by the National Committee for Clinical Laboratory Standards.
All isolates were susceptible to penicillin. From 1991 to 1996, the
percentage of S. pyogenes resistant or with intermediate resistance to
erythromycin increased from 0% to 50% (1992, 6%; 1993, 13%; 1994, 14%;
1995, 24%; 1996, 50%). In 1997 and the first half of 1998, resistance to
erythromycin decreased to 39% and 34%, respectively. The number of
resistant strains before 1996 was significantly lower than from 1996 to
1998 (chi-square = 50.386, p <0.0001). Analysis of antibiotic consumption
in our district showed an increase in the use of macrolides (erythromycin
and the new compounds clarithromycin and azithromycin) from 0.445 defined
daily dose per 1,000 inhabitants in 1994 to 1.140 in 1996. In 1997 and in
the first half of 1998, consumption decreased to 0.9 and 0.8, respectively;
we observed a correlation between the number of resistant isolates and the
defined daily dose increase (correlation [R2] = 0.795, p = 0.0153).

S. pyogenes resistance to erythromycin rose from 6% to 50% in only 4 years
and then rapidly decreased from 50% to 34% in an 18-month period,
corresponding to a 57% decrease in defined daily dose (from 1.41 in 1996 to
0.8 in the first half of 1998). Our data suggest that S. pyogenes
resistance to erythromycin is associated with frequency of macrolide use.

Matteo Bassetti, Enrico Mantero, Giorgio Gatti, Antonio Di Biagio, and
Dante Bassetti
University of Genoa, G. Gaslini Children's Hospital, Genoa, Italy

References

  1. Cipriani P, Debbia EA, Gesu GP, Menozzi MG, Nani E, Nicolosi V, et al.
     Indagine policentrica AMCLI sull'incidenza di resistenze agli
     antibiotici in S. pyogenes. Microbiologia Medica 1995;10:171-4.
  2. Cornaglia G, Ligozzi M, Mazzariol A, Valentini M, Orefici G, Fontana
     R. Rapid increase of resistance to erythromycin and clindamycin in
     Streptococcus pyogenes in Italy, 1993-1995. Emerg Infect Dis
     1996;2:339-42.
  3. Cocuzza C, Blandino G, Mattina R, Nicoletti F, Nicoletti G. Antibiotic
     susceptibility of group A streptococci in 2 Italian cities: Milano and
     Catania. Microb Drug Resist 1997;3:379-84.
  4. Seppala H, Klaukka T, Vuopio-Varkila J, Muotiala A, Helenius H, Lager
     K, et al. The effect of changes in the consumption of macrolide
     antibiotics on erythromycin resistance in group A streptococci in
     Finland. Finnish Study Group for Antimicrobial Resistance. N Engl J
     Med 1997;337:441-6.

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

Estimated Incidence of Clostridium difficile Infection

To the Editor: Since the publication of our article Increasing
hospitalization and death, possibly due to Clostridium difficile diarrheal
disease (1), we have received several requests to estimate the incidence of
C. difficile infection. Our original study included only hospitalized
patients treated at the Lovelace Medical Center from 1993 to 1996, and no
information on the incidence of C. difficile infection. In response to
these requests, we used inpatient and outpatient medical claims for the
Lovelace managed care population to calculate incidence rates. We searched
medical claims for the Lovelace Health Plan/Senior Plan (LHP) to identify
patients who had a C. difficile diagnosis between January 1, 1993, and
December 31, 1997. LHP members are residents of New Mexico, most residing
in or near Albuquerque.

LHP had approximately 713,000 person-years of enrollment from 1993 to 1997.
We identified 104 members with a C. difficile diagnosis on a claims record
during this period. This group includes most of the patients in our
original study. Most patients (62.5%) were identified exclusively from
inpatient records; another 15.4% had both an inpatient and an outpatient
record with a C. difficile diagnosis; and 22.1% had only an outpatient C.
difficile diagnosis. We calculated an age-adjusted rate of infection
(adjusted to the 1990 U.S. population), for each year and for the 5-year
period. The incidence of C. difficile infection for all members during 1993
to 1997 was 14.8 cases per 100,000 person-years of enrollment. The patients
rates for male and female were essentially the same (14.4 vs. 15.5,
respectively). The rates increased dramatically with age. For persons ages
0-4, the age-adjusted rate per 100,000 person-years of enrollment (number
of cases) was 5.3 (2); for 5-14, 2.7 (3), for 15-24, 2.2 (2); for 24-34,
6.4 (6); for 35-44, 9.2 (12); for 45-54, 15.7 (17); 55-64, 16.8 (10);
65-74, 38.5 (19); and 75+, 98.9 (33). The overall average rate of infection
was 15.4; there were 104 cases.

The rate of infection may have declined since 1993 in this population. The
1993 rate was 24.5 per 100,000 person-years of enrollment, declining to
11.1 in 1997 (1993, 24.4; 1994, 19.1; 1995, 9.9; 1996, 12.3; and 1997,
11.1).

Our method for estimating rates has some limitations. We did not examine
laboratory records to confirm the diagnosis. In addition, some
laboratory-confirmed infections may not have resulted in a claims record
with a C. difficile diagnosis. The Lovelace managed-care population is an
insured, generally healthy population that may not have the characteristics
of patients in other health care delivery settings or, because of its
geographic restriction, the characteristics of the general U.S. population.
Nevertheless, these estimates provide a basis for determining the magnitude
of the public health problem of C. difficile infection. Additional
surveillance studies are needed to better estimate the incidence of
infection and to determine whether the incidence has declined during recent
years.

Floyd Frost,* Judith S. Hurley,* Hans V. Petersen,* and Roman N. Casciano
*Southwest Center for Managed Case Research, Albuquerque, New Mexico, USA;
and Analytica Group, Ltd., New York, New York, USA

Reference

  1. Frost F, Craun GF, Calderon RL. Increasing hospitalization and death
     possibly due to Clostridium difficile diarrheal disease. Emerg Infect
     Dis 1998;4:619-25.

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

Diphtheria in Eastern Nepal

To the Editor: Diphtheria, caused by Corynebacterium diphtheriae, was a
major childhood killer until the advent of the Expanded Program on
Immunization when diphtheria, pertussis, and tetanus (DPT) vaccination was
greatly increased; diphtheria gradually declined in many countries. We
report two cases of diphtheria identified at the B.P. Koirala Institute of
Health Sciences Hospital, Dharan, Nepal.

During April 1996, a 6-year-old patient had fever (for 5 days), difficulty
in swallowing and breathing, and change of voice (for 4 days). Throat
examination showed a grayish-white membrane over the right tonsil, uvula,
and adjacent soft palate. The membrane could not be removed, and the larynx
could not be examined. Swabs were taken from the membrane area and sent to
the laboratory, where smears were made and stained by Gram and Albert
stains. Gram-stained smears showed a large number of gram-positive bacilli
with the appearance of Chinese letters, and Albert stain showed bacilli
with numerous metachromatic granules. A diagnosis of faucial diphtheria,
with a strong possibility of laryngeal diphtheria, was made. The patient
was treated with parenteral penicillin and diphtheria antitoxin. His
condition improved after 6 days of therapy.

In December 1996, a 9-year-old patient sought treatment for chronic pain
and discharge in the left ear. On examination, he had mucopurulent
discharge, antral perforation, and mastoid tenderness. Throat examination
showed bilateral tonsilitis. A provisional diagnosis of acute mastoiditis
associated with acute septic tonsillitis was made. Throat swabs were
collected and sent to the laboratory; smear findings showed typical
organisms morphologically resembling C. diphtheriae. Culture done on 10%
defibrinated sheep blood agar and Loefflers serum slope grew colonies
consistent with C. diphtheriae. In addition to local antibiotic to the ear,
the patient was given parenteral penicillin, gentamicin, and metronidazole.
Because the patient had no features of systemic toxicity, no antidiphtheria
serum was administered. The patient became well and was discharged on day
4.

In the first case, a throat culture could not be done because the patient
had already received local antiseptic paint. However, the diagnosis was
clinically consistent with classic diphtheria with features of toxicity. In
the second case, diphtheria was suspected only after bacteriologic
examination. Unlike patient 1, patient 2 had no evident features of
systemic toxicity. Hence the isolate could be nontoxigenic. Localized
diphtheria due to nontoxigenic C. diphtheriae is known to occur (1).

The two patients did not give a complete history of immunization and may
not have been vaccinated (or may have been partially vaccinated) with DPT.
On the Indian subcontinent, DPT vaccination coverage is reported to be 80%.
However, it may not be so in all areas, and immunization may have decreased
to approximately 50% in certain areas of Southeast Asia (2). This may also
be true in certain areas of eastern Nepal. An immunization status survey
done in midwestern Nepal from 1989 to 1990 showed that DPT coverage was
unsatisfactory (3). Lack of sustained immunization may even result in
outbreaks. The recent epidemics of diphtheria in the Ukraine, Russian
Federation, and other countries of the former Soviet Union are examples of
resurgence due to ineffectively maintained immunization programs (4,5).

Diphtheria, still occasionally seen in many Southeast Asian countries
including India and Nepal, is thought to be declining in these areas.
However, accurate data have not been recently available, particularly from
Nepal, because reporting is infrequent, laboratory confirmation is not
available, and the extent of carriers is not clearly known (2).

These two cases show the persistence of diphtheria in a population in Nepal
immunized with DPT and underscore the need for careful surveillance,
laboratory documentation of clinical diphtheria, and increased immunization
of children in this area.

H. Srinivasa, S.C. Parija, and M.P. Upadhyaya
B.P. Koirala Institute of Health Sciences, Dharan, Nepal

References

  1. Dixon JMS, Noble WC, Smith GR. Diphtheria, other mycobacterial, and
     corynebacterial and coryneform infections. In: Topley and Wilson's
     principle of bacteriology, virology and immunology. Vol 3. 8th ed.
     London: Edwards Arnold; 1990. p. 55-79.
  2. Srinivasa H. Immunizing children in Southeast Asia: a critical
     appraisal of current EPI status and future prospects. In: Immunizing
     agents for tropics: success, failure and some practical issues (BPKIHS
     Monograph Series 1). B.P. Koirala Institute of Health Sciences
     (BPKIHS) Hospital, Dharan, Nepal; 1997. p. 1-8.
  3. Shrestha IB. Immunization status in mid-western region of Nepal. In:
     Health Research Abstract 1991-1994. Nepal Research Council 1995.
     Proceedings of Second National Seminar on Health Research in Nepal at
     Kathmandu, Nepal. 1994 Dec 20-22.
  4. The World Health Reports. Fighting disease, fostering development.
     Report of the Director General, World Health Organization, Geneva;
     1996.
  5. Begg N, Balraj B. Diphtheria: are we ready for it? Archives of
     Childhood 1995:568-92.

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

Commercial Use of Burkholderia cepacia

To the Editor: In their review of the potential threat to human health by
the commercial use of Burkholderia cepacia, Holmes et al. (1) focus on the
biopesticidal uses of this bacterium in agriculture. By virtue of its
ability to antagonize a number of soilborne plant pathogens, B. cepacia is
an attractive natural alternative to currently used chemical pesticides,
such as captan, mancozeb, and metalaxyl. The replacement of these highly
toxic agents, which are among the mainstays of crop protection chemicals,
by safer products is a laudable goal. However, despite being nonpathogenic
to healthy humans (and thus classified as a Biosafety Level 1 species), B.
cepacia can cause life-threatening pulmonary infection in persons with
cystic fibrosis. Holmes et al. call for a moratorium on the use of B.
cepacia in agriculture until more is known about risks from such use.

Perhaps of greater concern than agricultural use is B. cepacia's use as a
bioremedial agent. Holmes et al. only briefly refer to the capacity of this
species to degrade chlorinated aromatic substrates such as those found in
certain pesticides and herbicides. By virtue of its extraordinary metabolic
versatility, B. cepacia can use such compounds as nutrient carbon energy
sources. In addition, some strains produce enzymes capable of degrading
nonnutritive substrates, such as trichloroethylene (TCE), a major ground
water contaminant used in the dry cleaning industry and in degreasing
solvents.

The degree to which B. cepacia is being used in bioremediation products is
unknown; however, the species has been used extensively to degrade ground
water TCE contamination in at least one large U.S. city. A number of
environment-friendly bioremediation products containing only naturally
occurring, nonpathogenic bacteria are being marketed for use in drain
opening and grease eradication systems. Because their formulations are
proprietary, it is not known if these products contain B. cepacia; however,
franchises that distribute such totally natural, noncorrosive, nontoxic
products specifically target fast-food restaurants, photo processing
facilities, and hospital radiology departments.

In the United States, the biopesticidal use of microorganisms such as B.
cepacia is regulated by the Environmental Protection Agency (EPA) under the
Federal Insecticide, Fungicide, and Rodenticide Act; however, the use of
naturally occurring, nonpathogenic bacteria as bioremedial agents is
essentially unregulated. Only new microorganisms (i.e., intergeneric or
formed by combining genetic material from organisms in different genera)
are regulated by EPA under the Toxic Substances Control Act (TSCA) (2).
Ironically, TSCA regulations provide a strong disincentive to the
development of safer microbiologic alternatives for use in bioremediation.
For example, although the genetic elements responsible for TCE degradation
by B. cepacia have been cloned, their recombination into another
nonpathogenic bacterial host (e.g., Escherichia coli) would constitute a
new microorganism, the licensure of which would be considered prohibitively
time-consuming and expensive by many companies.

In Canada, biopesticidal uses of microorganisms are regulated by the Pest
Management Regulatory Agency of Health Canada, under the Pest Control
Products Act (PCPA); bioremedial uses are regulated by Environment Canada
under the Canadian Environmental Protection Act (CEPA) (3). Both naturally
occurring and genetically engineered microorganisms are strictly controlled
under these acts. However, accurate species identification is the
cornerstone of all notification of products under the Canadian regulations.
This presents a further dilemma. At least five genomovars (discrete
species) constitute what has recently been designated the "B. cepacia
complex" (4). Insofar as the taxonomy of this group is poorly defined,
there are no conventional taxonomic designations to distinguish pathogenic
from nonpathogenic species. At present, it appears that all five B. cepacia
genomovars are capable of causing infections in vulnerable persons (4).

Because the epidemiology of B. cepacia complex infection in humans is
incompletely understood, the threat posed by the inclusion of this species
in biopesticides and bioremedial products is difficult to quantify.
However, we agree with Holmes et al. that such use should be approached
with considerable caution. In a broader context, the commercial use of B.
cepacia illustrates our incomplete understanding of nonpathogenic bacteria
and their potential to cause human disease. Regulations governing the use
of microorganisms in industry must constantly adapt to keep pace with the
emergence of infections due to nonpathogens and limit risk to human health.

John J. LiPuma* and Eshwar Mahenthiralingam
*MCP Hahnemann University, St Christopher's Hospital for Children,
Philadelphia, Pennsylvania, USA; and University of British Columbia,
Vancouver, British Columbia, Canada

References

  1. Holmes A, Govan J, Goldstein R. Agricultural use of Burkholderia
     (Pseudomonas) cepacia: a threat to human health? Emerg Infect Dis
     1998;4:221-7.
  2. Microbial products of biotechnology; final regulations under the Toxic
     Substances Control Act; final rule. Washington: U.S. Environmental
     Protection Agency, 1997. Federal Register. Vol 62. p. 17910-58.
  3. Guidelines for the notification and testing of new substances:
     organisms. Pursuant to the New Substances Notification Regulations of
     the Canadian Environmental Protection Act. Ottawa, Canada: Environment
     Canada, Health Canada, 1997.
  4. Vandamme P, Holmes B, Vancanneyt M, Coenye T, Hoste B, Coopman R, et
     al. Occurrence of multiple genomovars of Burkholderia cepacia in
     cystic fibrosis patients and proposal of Burkholderia multivorans sp.
     nov. Int J Syst Bacteriol 1997;47:1188-200.

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

Human Rabies in Israel

To the Editor: Rabies, a major zoonotic disease in the Middle East, has two
main epidemiologic forms: urban and sylvatic. The last case of human rabies
in Israel was in the Golan Heights in 1971 (1). Twenty-five years later, in
1996, rabies was reported in a 20-year-old soldier, and then two cases were
documented in 1997.

The first case-patient, a soldier in the Golan Heights, was bitten on the
lip by an unidentified animal while sleeping. The wound was cleansed and
sutured; clinical signs started 39 days later with high fever and headache.
The patient was admitted to an emergency room with hallucinations,
difficulty in swallowing, and generalized weakness, and rabies was
considered in the differential diagnosis; 3 days later the patient became
comatose. Samples of saliva, serum, and cerebrospinal fluid; skin biopsy
tissue; and corneal impressions were sent to the Pasteur Institute, Paris,
France. Eight days after clinical signs developed, rabies was diagnosed by
the Kimron Institute by heminested reverse transcription-polymerase chain
reaction (hnRT-PCR) on the patient's saliva (2). The RT step was performed
with the specific primer 113 (5'-GTAGGATGATATATGGG-'3 at 1013-1030),
followed by PCR with the 509 (5'-GAGAAAGA ACTTCAAGA-'3 at 1156-1173) and
304 (5'-GAGT CACTCGAATATGTC-'3 at 1513-1533) primers. The hn-PCR was
performed with the 509 and 105 (5'-TTCTTATGAGTCACTCGAATA TGTCTTGTTTAG-'3 at
1393-1426) primers (3). The PCR results were confirmed by the Pasteur
Institute 3 days later, and the patient died 35 days after clinical
symptoms appeared.

The second case-patient was a 7-year-old girl admitted to the hospital
unconscious. Two months before admission, she had been scratched while
sleeping by an unidentified animal. On the second hospital day, generalized
convulsions and gasping occurred. During the following days, brain stem
function progressively deteriorated. Rabies was diagnosed by hnRT-PCR on
the saliva sample, and the diagnosis was confirmed by the Centers for
Disease Control and Prevention (CDC). The patient died despite supportive
care.

The third case-patient, a 58-year-old man with fever, headache, and sore
throat, was diagnosed as having pharyngitis and received an oral
antibiotic. The patient had been bitten 3 months earlier while sleeping. On
admission, the lumbar puncture, computerized tomography scan, and
electroencephalogram were normal. On the third hospital day, he had
respiratory arrest; during orotracheal intubation, acute laryngospasm with
copious amounts of salivation occurred. Rabies was suspected, and viral RNA
in the saliva was detected by hnRT-PCR. One day later the patient died.

We injected antemortem saliva and postmortem brain tissue from these
patients into suckling mice intracerebrally. Virus was isolated from saliva
samples of case-patients 1 and 3 but not from the sample of case-patient 2.
Rabies virus antigen in the brain tissue was confirmed by direct
immunofluorescence assay, and viral RNA was detected by RT-PCR.

For genetic analysis, we used brain samples from the three case-patients
and from animals that died of rabies near the location of the case-patients
to amplify and sequence a 328-bp (264 bp from the 3' of the N gene and 64
bp of the 3' NS-N region) fragment. On the basis of homologic results of
nucleotide sequences in the three case-patients and in virus isolates from
animals in the same regions, we concluded that a reservoir for rabies in
foxes is responsible for infection of all three humans.

The three human isolates were tested with a panel of 19 anti-N protein
monoclonal antibodies (CDC, Atlanta, GA, USA) and compared with those of
rabies isolates from the geographic vicinity of the human cases. Isolates
from case-patients 1 and 3 belonged to variant 1 (MAb C18 negative) and
were similar to virus isolates from 10 foxes, one jackal, and four cattle
in the same regions. Isolates from case-patient 2 belonged to antigenic
variant 2 (MAbs C2, C7, C12, C13, C18 negative) and were similar to
isolates from four foxes, one dog, and one cow in the vicinity of the
second case-patient.

Early antemortem diagnosis of virus in an infected human is very important.
Checking for virus in saliva eliminates the difficulty of tissue sampling
from humans with suspected cases of rabies, and the sensitivity of hnRT-PCR
makes it the technique of choice for detecting limited amounts of virus.
Previous work showed that a 200-bp region of the N gene had only one
nucleotide difference between them (4). Moreover, two samples from a region
in western Mexico, isolated 30 years apart, were identical in sequence (4).
Incorporation of the reference strains Pasteur and SAD B19 into our
phylogenetic tree indicated that the three human viruses we isolated belong
to lyssavirus genotype 1.

Dan David,* Charles E. Rupprecht, Jean Smith, Itzhak Samina,* Shmuel
Perl,* and Yehuda Stram*
*Kimron Veterinary Institute, Bet Dagan, Israel; and Centers for Disease
Control and Prevention, Atlanta, Georgia, USA

References

  1. Shimshony A. Veterinary public health in Israel. Revue Scientifique et
     Technique Office International Des Epizooties 1992;11:77-98.
  2. Heaton PR, Johnstone P, McElhinnely M, Coweley R, O'Sullivan E, Whitby
     JE. Heminested PCR assay for detection of six genotypes of rabies and
     rabies related viruses. J Clin Microb 1997;35:2762-6.
  3. Smith JS. Rabies virus. In: Murray PR, Baron EJ, Pfaller MA, Tenover
     FC, Yolken RH, editors. Manual of clinical microbiology. 6th ed.
     Washington: American Society for Microbiology; 1995. p. 907-1003.
  4. Smith JS, Seidel HD, Warner CK. Epidemiology and historical
     relationships among 87 rabies virus isolates determined by limited
     sequence analysis. J Infec Dis 1992;166:296-307.

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

Emerging Infections and Disease Emergence

To the Editor: Emerging infections have been defined as diseases whose
incidence in humans has increased within the last 2 decades or threatens to
increase in the near future (l). This definition, with minor variations,
has continued to be used, although occasional debate erupts over whether
one disease or another is truly emerging. Use of the term "emerging" has
facilitated communication about the changed pattern of infectious diseases
in recent years. While the study of infectious organisms and clinical
training about emerging infections are manifestly necessary, they are not a
sufficient foundation for understanding the process of disease emergence. I
would propose, specifically, that we distinguish between emerging
diseasesthe study of specific infections that are changingand the study
of disease emergence.

Studies of emerging infections typically rely on disease, organismic, or
syndromic approaches. Meetings on emerging infections typically cover newly
recognized or characterized organisms or diseases and update information
about the recognition, diagnosis, treatment, prevention, and control of
these infections. This ongoing education is essential for practicing
clinicians, who finished their formal training before AIDS, Lyme disease,
ehrlichiosis, Helicobacter pylori infection, cryptosporidiosis,
cyclosporiasis, and many other infections were described. These meetings
also help clinicians learn how to fit new information into their existing
knowledge base: What is the probability that a person with rash and fever
has ehrlichiosis and that a person with fever and pulmonary infiltrates has
hantavirus pulmonary syndrome?

By contrast, understanding the process of disease emergence involves
studying the origins and ecology of emerging infections. Many disciplines
relevant to disease emergence lie outside traditional infectious disease
training and research and include evolutionary biology, demography,
population dynamics, ecology, vector biology, climatology, epidemiology,
genetics, veterinary medicine, and behavioral sciences (2). Infectious
diseases of animals and plants have both a direct and indirect impact on
human health. The study of infectious diseases in other species may provide
important insights into understanding the process of disease emergence in
humans. The study is also relevant to understanding the species-to-species
spread of organisms.

Tools used to study and understand disease emergence include mathematical
modeling, geographic information systems, remote sensing, molecular methods
to study the genetic relatedness of organisms, and molecular phylogeny.
Paleobiology, paleoecology, and studies that allow the reconstruction of
past events may help inform future research and policy.

A major challenge is to reach people with relevant skills, knowledge, and
experience and develop a coherent framework to advance the understanding of
the process of disease emergence. No one institution, organization, or
country can itself prevent or manage emerging infectious diseases.

In the study of emerging infections we focus on the organism, the patient,
and the human population. The study of disease emergence must be at the
systems level and must look at ecosystems, evolutionary biology, and
populations of parasites and hosts, whatever their species. A primary goal
should be to identify conditions or combinations or sequences of events
that herald a changed pattern of infections so that preventive strategies
can be used.

Mary E. Wilson
Mount Auburn Hospital, Cambridge, Massachusetts, USA; Harvard Medical
School and Harvard School of Public Health, Boston, Massachusetts, USA

References

  1. Lederberg J, Shope RE, Oaks SC Jr., editors. Emerging infections:
     microbial threats to health in the United States. Institute of
     Medicine. Washington: National Academy Press, 1992.
  2. Wilson ME, Levins R, Spielman A, editors. Disease in evolution: Global
     changes and emergence of infectious diseases. Vol 4. New York: Ann N Y
     Acad Sciences; 1994.

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

Malaria Control in South America

To the Editor: The article by Roberts et al. regarding DDT use and malaria
in South America (1) correctly observes that health policy makers have
shifted the emphasis of malaria control programs from vector control to
case detection and treatment and that malaria control has been woefully
underfunded in recent years. However, their conclusions that increased
malaria is due to decreased spraying of homes with DDT and that DDT is
still needed for malaria control do not withstand close scrutiny.

The authors did not mention several factors influencing malaria increase in
recent decades, including growing antimalarial-drug resistance, the
deterioration of public health systems responsible for malaria control, and
large-scale migration to areas at high risk for malaria (e.g., almost all
Brazilian malaria cases occur in the Amazon region) (2,3). Extradomiciliary
malaria transmission, poor housing conditions, and human behavior in
frontier areas such as the Amazon region limit the usefulness of
insecticides. Thus, the deduction of causality between less house spraying
with DDT and increased malaria incidence under those circumstances is
questionable.

Roberts et al. have not actually linked increased malaria with eliminating
DDT use but rather with eliminating house spraying altogether, without
implementing effective alternatives. Malaria's recent decline in Brazil is
due to a strategy that combines health education, aggressive case detection
and treatment, and environmental management to eliminate Anopheles breeding
sites (C. Cato Prates, unpub. data). A similar strategy has sharply
reduced malaria incidence and deaths in Colombia (W. Rojas, unpub. data).
In Mexico, use of two synthetic pyrethroid insecticides (deltamethrin and
lambda cyhalothrin) for bed-net treatment and house spraying is controlling
malaria at a much lower cost than the use of the alternative insecticides
tried earlier and mentioned by Roberts et al. (4). Far from being pursued
"without meaningful debate," the reduction and phaseout of DDT and other
persistent organic pollutants is the subject of a 3-year United
Nationsfacilitated global negotiation process begun in June 1998.

Roberts et al. assert that DDT applied indoors does not move easily from
the application site; however, a mass balance model indicates that 60% to
80% of the DDT ends up outdoors within 6 months (K. Feltmate, A model and
assessment of the fate and exposure of DDT following indoor application
[bachelor's thesis]. Ontario: Trent University; 1998). From there, DDT can
be transported long distances in air, waterborne sediments, and biota,
accumulating in humans and other nontarget species (5). Meanwhile,
residents of sprayed houses accumulate high, persistent body levels of DDT
through skin contact and food contaminated with DDT from air and dust (6).

Long considered a probable human carcinogen, DDT also is associated with
reduced lactation, premature births, absorbed fetuses, and lower birth
weights (7-9). In addition, recent animal research has raised the
possibility that exposure of human fetuses or infants to DDT may cause
permanent behavioral changes and impairment of body systems (10-12).

Synthetic pyrethroid insecticides used on bed nets or for house spraying
against malaria-infected mosquitoes seem safer for human health than DDT
because humans and other mammals possess the ability to hydrolyze the
pyrethroids rapidly and excrete them from the body (13-14). Nevertheless,
DDT and pyrethroids share known health risks, notably endocrine disruption,
and the possible transgenerational consequences of chronic human exposure
to pyrethroids have not yet been studied (10,15-16). Optimal protection of
human health requires the development of integrated malaria control
strategies that eliminate or reduce routine insecticide use by taking
maximum advantage of environmental management, biological controls, and
other nonchemical vector control measures (17).

Patricia C. Matteson
U.N. Food and Agriculture Organization Programme for Community Integrated
Pest Management in Asia, Hanoi, Vietnam

References

  1. Roberts DR, Laughlin LL, Hshieh P, Legters LJ. DDT, global strategies,
     and a malaria control crisis in South America. Emerg Infect Dis
     1997:3:295-302.
  2. Wirth DF, Cattani J. Winning the war against malaria. Technology
     Review 1997;Aug/Sep:52-61.
  3. World Resources Institute, United Nations Environment Programme,
     United Nations Development Programme, the World Bank. World Resources
     1998-99. New York: Oxford University Press; 1998.
  4. Matteson PC, editor. Disease vector management for public health and
     conservation. Washington: World Wildlife Fund-US; 1999.
  5. Wania F, Mackay D. Tracking the distribution of persistent organic
     pollutants. Environmental Science & Technology News 1996;30:390-6.
  6. Bouwman H, Cooppan RM, Becker PJ, Ngxongo S. Malaria control and
     levels of DDT in serum of two populations in Kwazulu. Journal of
     Toxicology and Environmental Health 1991;33:141-55.
  7. Rogan WJ, Gladen BC, McKinney JD, Carreras N, Hardy P, Thullen J, et
     al. Polychlorinated biphenyls (PCBs) and dichlorodiphenyl
     dichloroethan (DDE) in human milk: effects on growth, morbidity, and
     duration of lactation. Am J Public Health 1987;177:1294-7.
  8. Gladen BC, Rogan WJ. DDE and shortened duration of lactation in a
     northern Mexican town. Am J Public Health 1995;85:504-8.
  9. Toxicological profile for 4,4'-DDE, 4,4'-DDD (updated). Atlanta: U.S.
     Department of Health and Human Services, Public Health Service, Agency
     for Toxic Substances and Diseases Registry; 1994. Pub. no. TP-93/05.
 10. Eriksson P. Developmental neurotoxicity of environmental agents in the
     neonate. Neurotoxicology 1997;48:5719-26.
 11. Rehana T, Rao PR. Effect of DDT on the immune system in Swiss albino
     mice during adult and perinatal exposure: humoral responses. Bull
     Environ Contam Toxicol 1992;48:535-40.
 12. Banerjee BD, Saha S, Mohapatra TK, Ray A. Influence of dietary protein
     on DDT-induced immune responsiveness in rats. Indian J Exp Biol
     1995;33:739-44.
 13. Ray DE. Pesticides derived from plant and other organisms. In: Hayes
     WJ, Laws ER, editors. Handbook of pesticide toxicology. Vol 2. San
     Diego (CA): Academic Press; 1991. p. 585-636.
 14. Casida JE, Gammon DW, Glickman AH, Lawrence LJ. Mechanisms of
     selective action of pyrethroid insecticides. Annu Rev Pharmacol
     Toxicol 1983;23:413-38.
 15. Patro N, Misha SK, Chattopadhyay M, Patro IK. Neurological effects on
     deltamethrin on the postnatal development of cerebellum of rat.
     Journal of Biosciences 1997;22:117-30.
 16. Smolen MJ, Sang S, Liroff RA. Hazards and exposures associated with
     DDT and synthetic pyrethroids used for vector control. Washington:
     World Wildlife Fund-US;1999.
 17. Resolving the DDT dilemma: protecting biodiversity and human health.
     Toronto, Canada: World Wildlife Fund-Canada; 1998.

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

Malaria Control in South America Response to P.C. Matteson

To the Editor: Dr. Matteson, whose letter relies heavily on unpublished
information and nonrefereed publications, states that growing drug
resistance has contributed to increasing malaria. While drug resistance is
important, when DDT use declined below effective levels (1), the proportion
of Plasmodium falciparum infections (including infections with resistant
strains) compared with P. vivax infections (no resistance) did not
progressively increase (2). Moreover, malaria has increased in Central
America, where drug resistance is unknown (3-6). As for attributing
increasing malaria to deteriorating public health systems, the changes
imposed on developing countries (in organizational structures of malaria
control programs and prohibiting DDT [1,7]) correlate with increasing
malaria rates (1).

Dr. Matteson states that large-scale migration explains why almost all
Brazilian malaria cases occur in the Amazon Basin. However, DDT cleared
malaria from the more populated and temperate southern regions of the
country (8, unpublished report: U.S. Agency for International Development
review in 1973-74 of Brazil's malaria eradication program). When DDT was in
full use (pre-1980), large increases in malaria did not accompany
population movement (1). With the 1970s' colonization program of the Basin
came malaria problems, but not large population-based malaria increases.
DDT prevented that (1,9-11). However, since DDT has been eliminated,
persistent urban malaria is again becoming a problem (12-16).

Other factors (biting behavior, housing conditions, and human behavior),
which Dr. Matteson attributes to increasing malaria, have always thwarted
interdiction of malaria transmission in the Amazon Basin (17;18; an
unpublished report: U.S. Agency for International Development review in
1973-74 of the malaria eradication program in Brazil) and are no more
important today than they were before.

A UN-facilitated global negotiation process cited as a meaningful debate
for malaria control is an effort to provide a legally binding agreement for
global elimination of DDT and other persistent organic pollutants, not an
open forum for debate of DDT use for malaria control.

Dr. Matteson claims that DDT is associated with reduced lactation. In the
United States, where DDT has been banned for 26 years, mothers who stay
home breast-feed for an average of 25.1 weeksmothers who work parttime,
for 22.5 weeks (19). In Belize, mothers in urban areas, where DDT is not
used for malaria control, breast-feed less than 38.4 weeksmothers in rural
areas with lifetime exposures to DDT breast-feed more than 57.2 weeks (20).

The World Wildlife Fund's mass balance model of DDT sprayed in houses used
to refute our assessment that DDT does not readily move away from sprayed
houses also mentions that "There are few...data against which to validate
the results of this...model, although actual data...should not be difficult
to obtain." (21). Studies of DDT use in agriculture show that most DDT
settles where it is applied (22).

Studies have shown no meaningful population-based adverse health effects
from DDT use, despite more than 50 years' exposure, and evidence argues
forcefully that DDT does not cause breast cancer (23).

Donald R. Roberts and Larry L. Laughlin
The Uniformed Services University of the Health Sciences, Bethesda,
Maryland, USA

References

  1. Roberts DR, Laughlin LL, Hsheih P, Legters LJ. DDT, global strategies,
     and a malaria control crisis in South America. Emerg Infect Dis
     1997;3:295-302.
  2. Brasil. Registro de casos de malria1960 a 1997. Gerncia Tcnica de
     Malria/FNS-Brasilia, Brasilia, Brasil.
  3. Pan American Health Organization. Status of malaria programs in the
     Americas. XL report. Washington: The Organization; 1991. p. 145.
  4. Pan American Health Organization. Status of malaria programs in the
     Americas. XLII report. Washington: The Organization; 1994. p. 116.
  5. Pan American Health Organization. Status of malaria programs in the
     Americas. XLIII report. Washington: The Organization; 1995. p. 25.
  6. Pan American Health Organization. Status of malaria programs in the
     Americas. XLIV report. Washington: The Organization; 1996. p. 23.
  7. Roberts DR. Resurgent malaria: DDT and global control. U.S. Medicine
     1998;34:36-8.
  8. de Bustamante FM. Distribuio geogrfica e periodicidade estacional
     da malria no Brasil e sua relao com os fatores climticos. Situao
     atual do problema. Revista Brasileira de Malariologia e Doenas
     Tropicais 1957;9:181-90.
  9. Pinheiro FP, Bensabath G, Rosa APAT, Lainson R, Shaw JJ, Ward R, et
     al. Public health hazards among workers along the Trans-Amazon
     Highway. Journal of Occupational Medicine 1977;19:490-6.
 10. Smith NJH. Colonization lessons from a tropical forest. Science
     1982;13:755.
 11. Roberts DR. Health problems of colonists. Science 1982;217:484.
 12. Sandoval JJF, Diniz R, Saraiva MGG, da Silva EB, Alecrim WD, Alecrim
     MGC, et al. Histrico da malria na cidade de Manaus e proposta de
     controle integrado. Rev Soc Bras Med Trop 1998;31, Suplemento 1:141.
 13. Amaral JCOF, Machado RLD, Segura MNO, Oliveira GS, Povoa MM. Avaliao
     longitudinal da infeco causada por Plasmodium falciparum e/ou
     Plasmodium vivax na populao de duas localidades de Icoaraci,
     Distrito de Belem, Para. Rev Soc Bras Med Trop 1998;31 Suplemento
     1:16.
 14. da Silva EB, Costa MF, Melo YFC, Alecrim MGC. Inqurito
     soroepidemiologico numa rea urbana em fase de ocupao, na cidade de
     Novo Aryao-Amazonas-Brasil. Rev Soc Bras Med Trop 1998;31 Suplemento
     1:82.
 15. Ventura AM, Pinto AY, Uchoa R, Calvosa V, Santos MA, Filho MS, et al.
     Malria por Plasmodium vivax em crianas-I-aspectos epidemiologicos e
     clnicos. Rev Soc Bras Med Trop 1998;31 Suplemento 1:82.
 16. Suarez MC, Fe NF, Alecrim WD. Estudo do processo de transmisso da
     malria em uma rea de invaso recente na cidade de Manaus Amazonas.
     Estudo entomologico. Rev Soc Bras Med Trop 1998;31 Suplemento 1:15-6.
 17. Forattini OP. Entomologia medica: I volume parte Geral, Diptera,
     Anophelini. So Paulo (Brasil): Faculdade de Higiene e Sade Publica;
     1962. p. 414.
 18. Rachou RG. Some manifestations on behaviouristic resistance in Brazil.
     Semina Suscep. Insects to insecticides, Panama, Report.: WHO
     1958:208-95.
 19. Frank E. Breastfeeding and maternal employment: two rights don't make
     a wrong. Lancet 1998;352:1083-4.
 20. Central Statistical Office, Belize. 1991 Belize family health survey,
     final report. Reprinted by U.S. Dept of Health and Human Services;
     1992. p. 69.
 21. Resolving the DDT dilemma: protecting biodiversity and human health.
     Toronto, Canada: World Wildlife Fund-Canada; 1998.
 22. World Health Organization. DDT and its derivatives. Environmental
     health criteria 9. Geneva: The Organization; 1979. p. 194.
 23. Safe, SH. Xenoestrogens and breast cancer. N Engl J Med
     1997;337:1303-4.

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

On the Etiology of Tropical Epidemic Neuropathies

To the Editor: In a recent report of an epidemic of optic neuropathy in Dar
es Salaam, Tanzania (1), Dolin et al. state that the disease is clinically
identical to one of the forms of epidemic neuropathy found in Cuba between
1991 and 1993 (2). Cases of peripheral neuropathy have been part of both
epidemics (1,2). Both epidemics occurred in nutritionally deficient
populations (1,3).

Dolin et al. state that the cause of the Tanzanian epidemic is unknown and
probably difficult to establish; however, we believe findings from the
Cuban epidemic could be used to study the etiology of this and other
tropical epidemic neuropathies.

In Cuba, several research groups isolated and characterized an enterovirus
in the cerebrospinal fluid (CSF) of epidemic neuropathy patients (4,5).
Enterovirus sequences were found in CSF of 40 (36%) of 111 epidemic
neuropathy patients versus 1 (8%) of 12 control surgical patients (p <
0.01, chi-square test with 2 x 2 contingency tables) (5). Recently, this
enterovirus has been shown to form quasispecies, which could account for
altered biologic properties (de la Fuente et al., submitted for pub.). We
thus propose that epidemic neuropathy has a nutroviral etiology:
Nutritional deficits and stress make the population more likely to become
ill after infection with enterovirus quasispecies with altered biologic
properties.

The relationship between the host's nutritional status and virus evolution
could be key in understanding the cause of epidemic neuropathy, the
Tanzanian epidemic of optic neuropathy, and other tropical epidemic
neuropathies. Etiologic factors must be identified before appropriate
intervention and treatment strategies can be implemented.

Jos de la Fuente and Mara P. Rodrguez
Centro de Ingeniera Gentica y Biotecnologa, Havana, Cuba

References

  1. Dolin PJ, Mohamed AA, Plant GT. Epidemic of bilateral optic neuropathy
     in Dar es Salaam, Tanzania. N Engl J Med 1998;338:1547-8.
  2. The Cuba Neuropathy Field Investigation Team. Epidemic optic
     neuropathy in Cubaclinical characterization and risk factors. N Engl
     J Med 1995;333:1176-82.
  3. Romn GC. On politics and health: an epidemic of neurologic disease in
     Cuba. Ann Int Med 1995;122:530-3.
  4. Ms P, Pelegrino JL, Guzmn MG, Comellas MM, Resik S, Alvarez M, et
     al. Viral isolation from cases of epidemic neuropathy in Cuba. Arch
     Pathol Lab Med 1997;121:825-33.
  5. Rodrguez MP, Alvarez R, Garca del Barco D, Falcn V, de la Rosa MC,
     de la Fuente J. Characterization of virus isolated from the
     cerebrospinal fluid of patients with epidemic neuropathy. Ann Trop Med
     Parasitol 1998;92:97-105.

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

Risk for Ebola Virus Infection in Cte d'Ivoire

To the Editor: In Ta National Park, Cte d'Ivoire, where a new strain of
Ebola virus was isolated (1), the World Health Organization is conducting a
project to identify the reservoir of the virus and evaluate the risk for
its emergence in local populations. In March 1998, we conducted qualitative
and quantitative surveys of the villagers' awareness of and risk for Ebola
infection. In four villages close to Ta National Park (4 km to 10 km), we
carried out structured interviews with 150 villagers and in-depth
interviews with 17 villagers and three traditional healers.

Of the 150 villagers participating in the structured interviews, 18.0% had
heard of Ebola (90.7% had heard of yellow fever). Of those aware of Ebola,
96.3% thought it life-threatening; 65.4% of them thought it preventable.
When ill, 81.2% of the respondents generally relied on traditional healers
or herbal medicine. During in-depth interviews traditional healers
discussed their treatment practices. In one treatment, an incision is made
on the skin and medicinal herbs are applied to the incision. Such
traditional practices were implicated in the spread of Ebola virus in
Gabon, where a traditional healer and his assistant (who were infected with
Ebola virus) were suspected of spreading the virus to their patients
through an unsterilized blade (1). The same practices would seem to pose a
risk for virus transmission in Cte d`Ivoire.

Even though officially Ta National Park is protected from human activities
to preserve its natural ecology, 84.0% of the 150 respondents to our survey
often hunted or farmed in the park, 62.2% had encountered chimpanzees, and
53.3% had eaten chimpanzee meat. According to the in-depth interviews,
chimpanzee meat is available at bush meat markets and is thought safe for
eating, even though primates infected with Ebola virus have been linked
with human cases (2,3).

Our survey results show that, even though no large-scale Ebola outbreaks
have occurred in this area, villagers living near the park are at
particularly high risk for infection because they are not aware of Ebola
and do not know that their local customs and behavior may be putting them
at risk. To prevent future Ebola epidemics in Africa, information,
education, and communication (IEC) programs should be established (3).
Moreover, further sociocultural studies on perceptions and behavior should
be conducted in addition to exploring the nature of the virus and its cycle
in the wild (2,4,5).

Osamu Kunii,* Pierre Formenty, Jeanne Diarra-Nama, and Nol Nahounou
*International Medical Center of Japan, Tokyo, Japan;  WHO Ta Forest
Project, Abidjan, Cte d'Ivoire; Ministre de la Sant Publique et des
Affaires Sociales, Abidjan, Cte d'Ivoire

References

  1. Georges AJ, Leroy Em, Renault AA, et al. Ebola Hemorrhagic Fever
     Outbreaks in Bagon, 1994-1997. Epidemiologic and Health Control
     Issues. J Infect Dis 1999;179(Suppl1):S65-75.
  2. Le Guenno B, Formenty P, Wyers M, Gounon P, Walker F, Boesch C.
     Isolation and partial characterisation of a new strain of Ebola virus.
     Lancet 1995;345:1271-4.
  3. Morris K. Facing up to tomorrow's epidemics. Lancet 1997;349:1301.
  4. Georges-Courbot MC, Lu CY, Lansoud-Soukate J, Leroy E, Baize S.
     Isolation and partial molecular characterisation of a strain of Ebola
     virus during a recent epidemic of viral haemorrhagic fever in Gabon.
     Lancet 1997;349:181.
  5. Tukei PM. Threat of Marburg and Ebola viral haemorrhagic fevers in
     Africa. East Afr Med J 1996;73:27-31.

Emerging Infectious Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, GA

URL: ftp://ftp.cdc.gov/pub/EID/vol5no2/ascii/letters.txt

Please note that figures and equations are not available in ASCII format; 
their placement within the text is noted by [fig] and [eq], respectively. 
Greek symbols are spelled out. The following codes are used: 
(ft) for footnote; (sup) for superscript; (sub) for subscript; 
>/= for greater than or equal to.