Ecological associations of vesicular stomatitis virus in rural Central America and Panama.

The principal objective of this study was to determine ecological associations of vesicular stomatitis virus (VSV)- New Jersey and VSV-Indiana in rural Central America and Panama. Two types of information were linked: the results of neutralizing antibody tests performed on sera from 3,232 lifetime residents of 189 rural study communitities of Central America and Panama, and ecological characteristics of the study communities as determined from natural resource atlases. The major finding was that neutralizing antibody acquistion to VSV-New Jersey was greatest for persons living at elevations between 350 and 649 meters, with relatively open, dry vegetation and distinct seasonal alternation of dry and moist (not wet) ground conditions. Similar ecological associations were found for VSV-Indiana, except that the risk of infection was also high in moist environments with dense tree cover. The results suggest that VSV-New Jersey and VSV-Indiana have similar but not identical maintenance and transmission cycles and that basic maintenance cycles for both viruses may exist in dry, open habitats rather than in tropicla rain forest habitats as was previously assumed for VSV-Indiana.

The impact of control measures on urinary schistosomiasis in primary school children in northern Cameroon: a unique opportunity for controlled observations.

As part of a program to integrate schistosomiasis control into the primary health care system in northern Cameroon, an unexpected opportunity to undertake a controlled evaluation of the impact of interventions was recognized. Inadvertently, a large part of Mindjil, one of four assessment villages, had been essentially excluded from the program, creating a unique natural control. The prevalence of infection with Schistosoma hematobium in school-aged children was 7% in the areas where the control program was implemented, and 71% in the excluded areas (P < 0.0002). High intensity infection was 1% and 26% in the two areas, respectively (P < 0.0002). Children in the school where the control interventions were implemented had a significantly lower prevalence of infection with Schistosoma hematobium (P < 0.005). Subjects in intervention areas demonstrated greater knowledge about the transmission of schistosomiasis than those in the control area. This study documented and quantified program impact in a controlled manner not usually possible in field studies and also illustrated how unrecognized intracultural diversity (within culture differences) in target populations may effect disease control programs in communities.

Is trichuriasis associated with iron deficiency anemia?

We performed quantitative fecal examinations, hemograms, and serum iron determinations on 103 first-grade children from Vieques Island, Puerto Rico, to determine whether trichuriasis was associated with iron deficiency and anemia. Although hemoglobin values tended to be slightly lower in Trichuris-infected children, there was no association between trichuriasis and serum iron or transferrin saturation values. These data demonstrate that in lightly infected children such as the population studied trichuriasis is not associated with iron deficiency anemia.

Evaluation of alternate methods of rapid assessment of endemicity of Onchocerca volvulus in communities in southern Cameroon.

Potential diagnostic indicators of onchocerciasis (subcutaneous nodules, depigmentation or leopard skin, microfilaruria, diethylcarbamazine patch test positivity, excoriations, and pruritus) were evaluated in a rain forest region of southern Cameroon for usefulness in rapid assessment of onchocerciasis endemicity in communities. Thirty-two study villages were selected, representing high, intermediate, and low prevalence levels, and 846 adult male residents of these communities 20 or more years of age were examined according to a defined protocol. Skin snips (from each iliac crest) served as the reference standard. Skin snip positivity was 75.5%; the effect of age was minimal. Leopard skin and nodules showed the strongest correlation with both the skin snip prevalence and community microfilarial load, as reflected by the adult male study population. We selected > or = 20% nodules or > or = 20% leopard skin as the most appropriate local criteria for assigning a community to high priority for control, which corresponds to a > or = 90% skin snip prevalence in adult males. While this criteria should not be applied to regions with savannah onchocerciasis, we believe the methodology can and should be used to determine appropriate diagnostic indicators for rapid assessment of Onchocerca volvulus endemicity in regions with different dynamics of transmission and clinical expression of disease.

Ivermectin distribution and the cultural context of forest onchocerciasis in South Province, Cameroon.

This investigation examined the cultural context of forest onchocerciasis in several communities in the Dja-Lobo Division of southern Cameroon. The study sought to elucidate behaviors that would enhance or diminish health status relative to forest onchocerciasis and other filarial infections, and to make culturally sensitive and appropriate recommendations regarding the development of health education materials and the long-term sustainability of the ivermectin distribution program in Dja-Lobo. The study consisted of two sequential components; the first was a qualitative study of a few severely affected villages and the second was a quantitative study of 212 randomly selected heads of households from eight villages. The Boulou and Baka peoples in these communities defined general filariasis (minak) as small worms under the skin, identified flies as important transmitters of the illness, and indicated that blindness and other skin and ocular problems were a consequence of the illness. Illness of the Dja (referring to an illness found near the Dja River) was another illness that was closely linked to onchocerciasis; local people indicated it was transmitted by the black flies found near the Dja River, resulting in severe itching and leopard skin. These and other cultural-behavioral data on filariasis were used to implement a health education and distribution program.

PIP: The cultural context of forest onchocerciasis was studied in the Boulou and Baka ethnic communities in the Dja-Lobo Division of southern Cameroon. A 2-day survey used focus group interviews followed by a questionnaire administered to 212 randomly selected individuals in 8 communities (88 male and 124 females heads of household) to assess their knowledge about onchocerciasis. Most people (98%) had some knowledge about the disease. Minak was the term used for filariasis by most people (97%) and people knew (90%) that black fly (nyamendimi) was responsible for its transmission. Other vectors of the illness identified were mosquitoes, dirty water, sorcery, and taboo foods. 81% thought that maternal transmission was possible and 66% indicated that filariasis could be transmitted sexually. Virtually all respondents associated itching and rash with minak (filariasis) and more than 60% also recognized the swelling of the skin and leopard skin as manifestations of filariasis. Filariasis, malaria, worms, and blindness were placed in the middle category when the severity of various diseases was ranked by 20 Boulou adults. In contrast, the Baka did not think that filariasis caused blindness, nor that it is linked to eye-worms. However, the 212 individuals ranked blindness as the most severe among other diseases (filaria, malaria, diarrhea, and intestinal worms). 80% of the Boulou and Baka adults had had filariasis in the previous year, but only 5% of the Boulou children and none of the Baka children had had filariasis during that time period. With respect to intestinal worms, 71% of the Boulou adults and 60% of the Baka adults had had intestinal worms in the previous year, while more than 90% of the Boulou children and all of the Baka children had had intestinal worms. Of the 90% who revealed that they had had filariasis at least once before, 69% sought treatment. 54% had tried traditional treatment, while 50% had tried Notezine, 49% had tried Phenergan, and 38% had tried M.G. Lumiere.

Prevalence and intensity of Schistosoma haematobium and S. mansoni infection in Qalyub, Egypt.

We report the preliminary findings of a comprehensive schistosomiasis survey in the Qalyub region of the Nile Delta. A systematic sample of households in eight villages was studied, and 8,712 individuals submitted stool and urine specimens for parasitologic examinations. The prevalence of Schistosoma mansoni infection (40.5%) was much higher than that reported previously in this area, and the prevalence of S. haematobium (27%) was much lower. The geometric mean egg output for both parasites was surprisingly low. The apparent increase in S. mansoni infection may be largely due to the use of a very sensitive parasitologic technique, but the decrease in S. haematobium prevalence is unexplained. Preliminary results of snail surveys, however, indicate a profound decrease in the population levels of Bulinus species, a phenomenon which may be related to ecological changes since construction of the Aswan High Dam.

The epidemiology of schistosomiasis in Egypt: Qalyubia Governorate.

The primary objectives of this study, carried out in Qalyubia Governorate in Egypt (south-central Nile Delta), were to continue tracking historical trends of infection prevalence of Schistosoma mansoni and S. haematobium, determine whether satellites (ezbas) of mother villages differed significantly with respect to schistosomiasis transmission, and to asses schistosomiasis-induced morbidity on a population basis using ultrasonography. Our study revealed that S. haematobium has virtually disappeared from Qalyubia governorate, and that S. mansoni prevalence continues to decline slowly (17% in 1991 compared with 19% in 1990). The prevalence of intestinal schistosomiasis was actually higher in the mother villages than in the ezbas of the same villages, indicating that prevalence based on surveys of villages alone did not (at least for Qalyubia) cause underestimates of true prevalence. (A mother village is the large village in an area that includes hamlets or ezbas. In many areas, the infection rate in ezbas is significantly higher than in the larger central village.) Ultrasonographic studies revealed that less than 3% of the population had stage 2 or stage 3 periportal fibrosis, commonly associated with chronic schistosomiasis mansoni. This low level of morbidity was consistent with earlier data from Qalyubia, which also showed a low level of S. mansoni-induced morbidity in this governorate.

Limitations of the intradermal test for schistosomiasis mansoni: experience from epidemiologic studies in a Puerto Rican community.

The intradermal reaction with Schistosoma mansoni adult-worm antigen (35-40 microgram/ml nitrogen) was evaluated as an edpidemiologic tool in an endemic Puerto Rican community where the prevalence of S. mansoni infection was 36% and the geometric-mean egg count was 17.6 eggs/g. Subcutaneous injections of antigen were made in forearms, and stool specimens were examined for S. mansoni eggs by a formol-ether concentration method. Of 296 persons tested, 43% had positive intradermal reactions (greater than or equal to 1.0 cm 2 at least twice the area of the control wheal), compared to 48% positive stool examinations. However, sensitivity was low at 36% for children 14 yr old or less, and only 73% to 79% for adults. The test results were very specific for children (96%), but 32% of stool negative adults were positive. Mean wheal area was not directly related to intensity of infection as determined by egg counts in either children or adults, but did increase directly with age. Mean wheal areas were greater for males than females (both children and adults) at all intensities of infection. Because of unsatisfactory sensitivity and specificity the intradermal test may overestimate the prevalence of infection when rates are low, and underestimate prevalence of infection when rates are high. For its proper interpretation, complementary parasitologic data from stool surveys are required.

The Boqueron Project after 5 years: a prospective community-based study of infection with Schistosoma mansoni in Puerto Rico.

The Boqueron Schistosomiasis Project is a prospective community-based study of Schistosoma mansoni infection after the interruption of transmission by nonchemotherapeutic control measures. The study methods and the parasitologic results of the first five annual stool surveys are described in this report. In the first year, 1972, among 904 inhabitants (88% of the total population) the prevalence of infection was 40%, and the geometric mean intensity of infection among positives was 16.1 eggs per gram (epg). Snail control was begun in early 1973 with molluscicides and habitat modification. Intensive monitoring every 2 weeks revealed only 63 noninfected Biomphalaria glabrata in the community during the subsequent 4 years. The incidence of new infectins among people negative in all previous surveys dropped from 17% in 1972 to 1% in 1974 and has remained negligible since then. Among young children and newborn, only four new infections (all less than 5 epg) were found after the first control year. Despite this low rate of transmission, prevalence only decreased from 37% to 34%, and the population geometric mean fecal egg output has not substantially changed in a cohort of 528 individuals examined in each of the six annual surveys. Possible reasons for the minimal change in parasitologic status are discussed and include water contact behavior outside the community and changes in laboratory techniques. Data from the first 5 years of the study suggest that in a population where mean intensity of infection with S. mansoni is low, further decreases in prevalence and intensity of infection occur slowly. The implications for control programs based on nonchemotherapeutic measures are discussed.

Quality control for parasitologic data.

Accuracy of data is of paramount concern for all research. The task of providing objective assurances of accuracy of parasitologic data for a large, multi-center epidemiologic research project in Egypt (Epidemiology 1, 2, 3 [EPI 1, 2, 3]) presented a unique set of challenges undertaken jointly by the Ministry of Health's Qalyub Center for Field and Applied Research with technical assistance from Tulane University (New Orleans, LA). The EPI 1, 2, 3 project was part of large bilateral research program, the Schistosomiasis Research Project, undertaken jointly by the governments of Egypt and the United States. This paper describes the nature of the quality control system developed to accomplish this task, presents results and discusses the findings.

Immunodiagnosis of infection with Schistosoma haematobium and S. mansoni in man.

We utilized the circumoval precipitin (COP) test, Ouchterlony immunodiffusion, and the enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of human infection with Schistosoma mansoni or S. haematobium, or with both species of schistosome. Only the COP test correctly identified all of those with schistosome infection, although differentiation as to schistosome species was impossible. Circumoval precipitates around S. haematobium eggs from human urine were more numerous and larger than those around S. mansoni eggs obtained from mouse livers. Ouchterlony immunodiffusion with S. mansoni or S. haematobium worm extract failed to diagnose correctly approximately one of every five infected individuals. Mean absorption values of the S. mansoni soluble egg antigen (SEA) used in the ELISA were similar in serum samples from persons infected with either or both species of blood flukes. This suggests that S. mansoni SEA is not species-specific. The ELISA correctly identified, however, 30 of 32 infected individuals, indicating high sensitivity.

Ancylostoma larva in a muscle fiber of man following cutaneous larva migrans.

This is a report of a case of massive cutaneous larva migrans in a 20-year-old man who also had pulmonary symptoms and larval invasion of the skeletal muscles. In sections of a muscle biopsy specimen taken 3 months after the initial cutaneous lesions, a third-stage Ancylostoma larva, probably A. caninum, was found within a muscle fiber.

Morbidity from Schistosoma mansoni in a Puerto Rican community: a population-based study.

A population-based approach was used to investigate morbidity from Schistosoma mansoni in a rural community in eastern Puerto Rico that was representative of remaining endemic foci on the island. In 1974 the prevalence of infection 855 of 1,056 inhabitants was 32.7% and the geometric mean egg output was 17.6 eggs per gram. A standardized medical history was obtained, and physical and laboratory examinations were performed on 737 (70%) of the community residents. Quantitative S. mansoni egg counts were performed on 1 gram of feces with a modified Ritchie formol-ether concentration technique; other intestinal parasites were recorded on a semi-quantitative basis. Interviews and physical examinations were conducted "blind" to minimize observer bias, and statistical analysis was done on data from 149 infected subjects and 149 noninfected controls matched by age and sex. For subjects under 20 years of age the frequency of hookworm infection and trichuriasis and absolute eosinophilia was significantly higher in the infected group, but no difference was found in the frequency of signs and symptoms of schistosomiasis. For the subjects 20 years and over, the symptom "blood in the stool" was reported more frequently in the infected group, but hematocrit level did not differ between infected and noninfected controls. Although palpable livers were noted more frequently in infected (8) than in noninfected (1) subjects 20 years and over, further evaluation of these subjects cast doubt upon a causal role for S. mansoni. These data indicate that morbidity from S. mansoni infection in the community is low, a finding consistent with the apparent decline in S. mansoni morbidity in Puerto Rico during recent decades and the relatively low intensity of infection in this community. Nevertheless, because of the sporadic occurrence of S. mansoni-induced disease on the island, and because heavily infected subjects are clearly at greater risk of disease, we are recommending treatment for community residents with high egg output.

Patterns of antischistosomal drug usage in Qalyubia Governorate of the Nile Delta.

To further investigate factors responsible for the recently documented changes in schistosomiasis patterns in the Nile Delta, questionnaire-derived information on antischistosomal drug usage was obtained from a 25% systematic sample of 609 residents of a stable village in the south-central Delta. Ten percent of the population had received antischistosomal drugs during the previous 4 years. Most of the drugs administered were injectable compounds, and 92% of individuals receiving them failed to complete the treatment regimen. Additional sources of information from a village physician, a pharmacist and a major pharmaceutical corporation confirmed and expanded the survey findings, indicating that antischistosomal drug usage cannot explain the recently observed changing patterns of human schistosome infections in the Nile Delta region.

Dengue outbreaks in Guánica-Ensenada and Villalba, Puerto Rico, 1972-1973.

Epidemics of dengue fever occurring in Puerto Rico in 1963 to 1964 and 1969 were caused by dengue-3 and dengue-2 (DN-2) viruses, respectively, but endemic dengue transmission has never been documented on the Island. Since the 1969 epidemic, a surveillance system has detected DN-2 activity on the Island during each of the years 1970 through 1973, which suggests endemic persistence of the virus. This report describes the investigation of localized outbreaks of DN-2 in Guanica-Ensenada (1972) and Villalba (1973), and presents epidemiological, serological, and virological data from the outbreaks. Analysis of geographic distribution of dengue activity in Puerto Rico in recent years indicates that the DN-2 transmission in 1970 to 1973 may represent a long tail-off of the 1969 epidemic rather than the emergence of a truly endemic situation.

A modification of the formol-ether concentration technique for increased sensitivity in detecting Schistosoma mansoni eggs.

The low Schistosoma mansoni egg counts generally found in Puerto Rico require a sensitive technique for epidemiologic studies. The Ritchie formol-ether concentration technique has been modified to make it more useful for this purpose. The modified technique was compared with the older technique by analyzing fecal specimens from ten individuals with varying levels of infection. It was also compared with the Kato thick-smear technique with specimens from 25 other patients. In both series, three replicates of each technique were done on each stool. Results indicated that the modified technique was more sensitive than the older technique in terms of number of eggs counted, and that the sediment was smaller and clearer and required about 15% less time to examine. In comparison with the Kato technique, it was more successful in detecting light infections, although at higher levels of intensity, when expressed on an eggs-per-gram basis, the thick smear detected relatively more eggs. For the series as a whole, coefficients of variation for the three replicates done on each stool were smaller for the modified concentration technique than for the Kato technique. This is interpreted to reflect satisfactory reproducibility of the concentration technique when compared to the Kato technique. The concentration technique has the additional advantages over the thick smear of detecting other intestinal parasites and allowing for transportation and storage after feces are preserved in formalin.

Changes in antischistosomal drug usage patterns in rural Qalyubia, Egypt.

To investigate the usage of antischistosomal drugs in the Nile Delta, an antischistosomal drug history was obtained by interview from a sample of inhabitants of the villages of Halaba (1,024, or every 4th household) and Kharkania (505, or every 20th household), south-central Nile Delta. Only 3% and 0.4% of participants, respectively, in the 2 villages reported receiving antischistosomal drugs during the previous 4 years. Most villagers received oral compounds (praziquantel and niridazole), and the treatment regimen was completed by 95%. This study reveals changes in antischistosomal drug usage since a study 8 years earlier in the village of Halaba, when most of the drugs were injectable compounds.

Evaluation of UNICEF/Arab Republic of Egypt/WHO schistosomiasis Control Project in Beheira Governorate.

We evaluated the UNICEF/Government of Egypt/WHO Schistosomiasis Control project in 2 districts of Beheira Governorate of the Nile Delta during 3 weeks in February 1988. The project, begun in 1983, was focused on reducing prevalence, intensity, and morbidity due to schistosomiasis by providing diagnosis and treatment with praziquantel to schoolchildren. Schools were visited twice. Following the completion of the school surveys, the program was extended into the community. Chemotherapy was delivered by mobile and static teams. The evaluation indicated that, with respect to accuracy of diagnosis, record-keeping, and coverage of targeted populations, project tasks were performed exceedingly well by highly motivated, well-supervised mobile teams. Static teams in rural health centers were less successful in providing diagnosis and chemotherapy to village populations. We resurveyed 6 randomly selected schools to assess the impact of chemotherapy. Overall, the prevalence of Schistosoma mansoni infection was reduced from 60.3% to 24.8% between the first and second surveys (approximately 1 year apart) and was still lower (41.1%) than initial levels up to 3 years after the last treatment with praziquantel. The percentages of those with greater than or equal to 34 S. mansoni eggs/slide using the Kato-Katz technique showed a marked and prolonged decrease (17.1% to 0.3% to 2.2%). The prevalence of S. haematobium infection dropped from 37.6% to 5.5% and was still 9.9% at the time of the evaluation. The percentages of those with greater than or equal to 50 S. haematobium eggs/10 ml urine dropped less dramatically (17% to 4.4% to 11.9%). Mobile teams conducting vigorous chemotherapy programs targeted at schoolchildren can have long-lasting benefits in terms of prevalence and intensity.

An evaluation of quantitative techniques for Schistosoma haematobium eggs in urine preserved with carbolfuchsin.

The objective of this study was to determine a suitable method for quantitating Schistosoma haematobium eggs in urine specimens preserved in carbolfuchsin. Using a 0.002% carbolfuchsin-phenol-alcohol solution as a stain/preservative for urine obtained from 30 patients infected with S. haematobium, we compared egg counts obtained with four quantitative techniques: Nytrel filtration, Nuclepore filtration, suction filtration and centrifugation. Centrifugation gave statistically higher values than all other techniques for absolute number of eggs recovered in the preserved urine. We also measure a statistical difference between the counts obtained from Nuclepore filtration of fresh urine and those established on an equivalent volume of preserved urine by Nuclepore and Nytrel filtration. The preserved urine frequently caused obstruction of both Nuclepore filters and Whatman No. 1 filters (used in suction filtration), rendering them technically difficult to use and less satisfactory than other methods. From the techniques we examined, we conclude that in field studies where preservation of urine is necessary, preparation of Nuclepore filters with fresh urine, or centrifugation of a carbolfuchsin-preserved urine, are the methods of choice for quantitation of specimens.

Larvicidal activity of albendazole against Necator americanus in human volunteers.

This study evaluated the efficacy and tolerance of a single oral 400-mg dose of albendazole on Necator americanus larvae, and compared its efficacy when administered between meals or with a meal. Twenty-nine healthy and hookworm-free male volunteers were exposed on the forearm to approximately 45 8-day-old N. americanus larvae. All subjects developed discrete maculopapular eruptions at the site of larval application. Following a random double-blind study design, each subject received at the end of the 6th post-infection day either the investigational drug or a placebo as follows: Group I (n = 8)-placebo; Group II (n = 11)-400 mg albendazole with a meal; Group III (n = 10)-400 mg albendazole 3 or more hours after or before a meal. On day 56 post-infection, the stools of all subjects who received placebo were positive for N. americanus eggs (by zinc sulfate flotation technique), compared with 48% positivity (10/21) in those who received albendazole (P = 0.01). By day 63 post-infection, an additional three subjects in the treatment group became positive, for an overall 62% rate of positivity (13/21), i.e., albendazole prevented patent infection in 38%. Administration of albendazole with a meal did not alter drug efficacy. In those subjects in whom patent infections were not prevented, egg output was one-fourth that of the placebo group. There was no difference in viability of eggs appearing in feces of treated and untreated subjects as judged by larval development in Harada-Mori cultures. Our data indicate that albendazole is active against pre-intestinal stages of N. americanus in human infections.