Multiyear prospective study of intestinal parasitism in a cohort of Peace Corps volunteers in Guatemala.

We conducted a prospective, longitudinal study in a cohort of 36 Peace Corps volunteers (PCVs) in Guatemala to study the incidence and natural history of intestinal parasitic infections during the PCVs' >2-year overseas stay. PCVs collected stool specimens at least monthly and when ill with gastrointestinal symptoms. Of the 1,168 specimens tested, 453 (38.8%) were positive for at least one parasite and 48 (4.1%) were positive for a pathogenic parasite. A median interval of 187 days (range, 14 to 752 days) elapsed before the first documented parasitic infection, and the median intervals from arrival until subsequent infections (e.g., second or third) were >300 days. The PCVs had 116 episodes of infection with 11 parasites, including up to 4 episodes per PCV with specific nonpathogens and Blastocystis hominis. The incidence, in episodes per 100 person-years, was highest for B. hominis (65), followed by Entamoeba coli (31), Cryptosporidium parvum (17), and Entamoeba hartmanni (17). The PCVs' B. hominis episodes lasted 6,809 person-days (28.7% of the 23,689 person-days in the study), the E. coli episodes lasted 2,055 person-days (8.7%), and each of the other types of episodes lasted <2% of the person-days in the study. Gastrointestinal symptoms were somewhat more common and more persistent, but not significantly so, in association with pathogen episodes than with B. hominis and nonpathogen episodes. Although infections with pathogenic parasites could account for only a minority of the PCVs' diarrheal episodes, the continued acquisition of parasitic infections throughout the PCVs' >2-year stay in Guatemala suggests that PCVs repeatedly had fecal exposures and thus were at risk for infections with both parasitic and nonparasitic pathogens throughout their overseas service.

The contrasting epidemiology of Cyclospora and Cryptosporidium among outpatients in Guatemala.

We compared epidemiologic characteristics of Cryptosporidium and Cyclospora in surveillance data from outpatient departments in Guatemala. Routinely-submitted stool specimens were screened by microscopy. Age, sex, and symptom data were collected. Cyclospora was detected in 117 (2.1%) and Cryptosporidium in 67 (1.2%) of 5,520 specimens. The prevalence of Cyclospora peaked in the warmer months, while Cryptosporidium was most common in the rainy season. Both affected children more than adults, but Cryptosporidium affected children at a younger age than Cyclospora (median age 2 years versus 5 years; P < 0.001). Cyclospora showed a stronger association with diarrhea than Cryptosporidium, even when data were stratified by age. These contrasts may reflect differences in the relative importance of transmission modes, the frequency of exposure, and the development of immunity.

Epidemiologic studies of Cyclospora cayetanensis in Guatemala.

In 1996 and 1997, cyclosporiasis outbreaks in North America were linked to eating Guatemalan raspberries. We conducted a study in health-care facilities and among raspberry farm workers, as well as a case-control study, to assess risk factors for the disease in Guatemala. From April 6, 1997, to March 19, 1998, 126 (2.3%) of 5, 552 surveillance specimens tested positive for Cyclospora; prevalence peaked in June (6.7%). Infection was most common among children 1.5 to 9 years old and among persons with gastroenteritis. Among 182 raspberry farm workers and family members monitored from April 6 to May 29, six had Cyclospora infection. In the case-control analysis, 62 (91%) of 68 persons with Cyclospora infection reported drinking untreated water in the 2 weeks before illness, compared with 88 (73%) of 120 controls (odds ratio [OR] 3.8, 95% confidence interval [CI] 1.4, 10.8 by univariate analysis). Other risk factors included water source, type of sewage drainage, ownership of chickens or other fowl, and contact with soil (among children younger than 2 years).

Mitochondrial DNA variation among Anopheles albimanus populations.

Barriers to gene flow between Pacific and Atlantic coast populations of Anopheles albimanus were reported in an earlier study of variation in the intergenic spacer of the nuclear ribosomal DNA. We examined the distribution of mitochondrial DNA haplotypes among A. albimanus populations to test for gene flow barriers with an independent genetic marker. A region of the NADH dehydrogenase subunit 5 gene was amplified by the polymerase chain reaction (PCR) in 1,105 mosquitoes collected from 16 locations in Guatemala and in single collections from Mexico, Honduras, Nicaragua, Costa Rica, Panama, Colombia, and Venezuela. The PCR products were tested for variation using single strand conformation polymorphism analysis and 45 haplotypes were detected. Haplotype frequencies did not vary between coasts in Guatemala. Populations within approximately 200 km of one another were panmictic. However, at distances > 200 km, FST and geographic distances were correlated suggesting that populations are isolated by distance.

Variation in ribosomal DNA intergenic spacers among populations of Anopheles albimanus in South and Central America.

Variation in the length and copy number of intergenic spacers (IGS) of nuclear ribosomal DNA were examined to test for genetic differentiation among Anopheles albimanus populations. Extensive collections were made in Guatemala but populations were also sampled over a large range of its distribution in Central and South America. Discriminant analysis of IGS patterns in individual mosquitoes indicated that populations generally had unique sets of IGS length variants. The IGS patterns from populations on the Pacific side of Central America were distinct from those on the Atlantic side or from South America. Cluster analysis indicated a similar trend. The IGS diversity in Central America was 50% greater than in South America. These results suggest that barriers to gene flow exist among Atlantic and Pacific coast populations of An. albimanus. No gene flow barriers were detected among populations from Colombia, Ecuador, Peru, and Venezuela.

Cutaneous leishmaniasis in Guatemala: comparison of diagnostic methods.

A comparison was made of methods used to diagnose suspected cutaneous leishmaniasis in Guatemala. The most sensitive method was a combination of thin smears made from superficial scrapings of the ulcers and inoculation of culture medium with either aspirates or scrapings. The diagnosis was confirmed in 252 (70%) of 362 patients. Ability to cultivate Leishmania was correlated with the concentration of amastigotes seen on thin smears. Leishmania were cultured in 42 (27%) of 153 patients with no amastigotes found in 400 oil-immersion fields and in 174 (83%) of 209 patients with at least 1 amastigote. No difference in diagnostic outcome was found when we compared smears or cultures taken from the center or the border of the ulcer or from an incision made tangential from the ulcer. We found no difference when we compared smears obtained with scalpels, capillary tubes, or dental broaches. The use of scrub brushes soaked in iodine neither decreased the rate of culturing parasites nor decreased contamination rates.

Placebo-controlled clinical trial of meglumine antimonate (glucantime) vs. localized controlled heat in the treatment of cutaneous leishmaniasis in Guatemala.

Sixty-six Guatemalans with parasitologically proven cutaneous leishmaniasis were randomly and equally divided into 3 treatment groups: those receiving meglumine antimonate (Glucantime), 850 mg antimony/day im for 15 days; those receiving localized controlled heat from a radio-frequency generator, 50 degrees C for 30 sec, 3 treatments at 7 day intervals; and those receiving treatment with a placebo. Of 53 isolates identified, 40 were Leishmania braziliensis braziliensis and 13 were L. mexicana mexicana. Thirteen weeks after beginning treatment, the number of patients from each group with completely healed and parasitologically negative lesions were as follows: meglumine antimonate, 16 (73%); localized heat, 16 (73%); and placebo, 6 (27%). The cure rate for those with infections due to L. b. braziliensis in each group was as follows: meglumine antimonate, 11 out of 14 (79%); controlled heat, 9 out of 14 (64%); and placebo, 0 out of 11.

Cutaneous leishmaniasis in Guatemala: isoenzyme characterization of isolates from humans.

Leishmania organisms cultivated from cutaneous lesions of humans in Guatemala were characterized by cellulose acetate electrophoresis. Six isolates had electrophoretic enzyme patterns identical to World Health Organization reference strains of Leishmania braziliensis braziliensis, and 5 had patterns identical to reference strains of Leishmania mexicana mexicana.