Assessment of control and epidemiologic details of the schistosomiasis mansoni in Bananal, São Paulo, Brazil.

The purpose of our study in the municipality of Bananal, state of São Paulo, Brazil, was to stop the transmission of schistosomiasis mansoni. Particular emphasis was given to such items as the active surveillance and eventual treatment of hosts, mapping parasite foci, and increasing the extent of basic sanitation in the municipality. Now, our records indicate that the eradication of schistosomiasis in the municipality of Bananal is attainable. However, as the vector Biomphalaria tenagophila can still be found in some water bodies within this municipality, it remains included in the area where schistosomiasis is endemic, which calls for very strict measures to avoid the human cases of schistososomiasis. The expansion of the coverage of the basic sanitation network and treatment of Schistosoma mansoni cases diagnosed during periodic surveys are part of the plans to eradicate schistosomiasis in Bananal.

On an acute case of Chagas disease in a region under vector control in the state of São Paulo, Brazil.

No vector transmitted cases of Chagas disease had been notified in the state of São Paulo since the 1970s. However, in March, 2006, the death of a six-year-old boy from the municipality of Itaporanga was notified to the Center for Epidemiological Survey of the São Paulo State Health Secretariat: an autochthonous case of acute Chagas disease. The postmortem histopathological examination performed in the Hospital das Clínicas of the Botucatu School of Medicine confirmed the diagnosis. Reference to hospital records, consultation with the health professionals involved in the case and interviews with members of the patient's family supplied the basis for this study. We investigated parasite route of transmission, probable local reservoirs and vectors. No further human cases of acute Chagas disease were diagnosed. No locally captured vectors or reservoirs were found infected with Trypanosoma cruzi. Alternative transmission hypotheses - such as the possible ingestion of foods contaminated with vector excreta - are discussed, as well as the need to keep previously endemic regions and infested houses under close surveillance. Clinicians should give due attention to such signs as uni- or bilateral palpebral edema, cardiac failure, myocarditis, pericarditis, anasarca and atypical signs of nephrotic syndrome or nephritis and consider the diagnostic hypothesis of Chagas disease.

Age-dependent acquisition of protective immunity to malaria in riverine populations of the Amazon Basin of Brazil.

Five community-based cross-sectional surveys of malaria morbidity and associated risk factors in remote riverine populations in northwestern Brazil showed average parasite rates of 4.2% (thick-smear microscopy) and 14.4% (polymerase chain reaction [PCR]) in the overall population, with a spleen rate of 13.9% among children 2-9 years of age. Plasmodium vivax was 2.8 times more prevalent than P. falciparum, with rare instances of P. malariae and mixed-species infections confirmed by PCR; 9.6% of asymptomatic subjects had parasitemias detected by PCR. Low-grade parasitemia detected by PCR only was a risk factor for anemia, after controlling for age and other covariates. Although clinical and subclinical infections occurred in all age groups, the risk of infection and disease decreased significantly with increasing age, after adjustment for several covariates in multilevel logistic regression models. These findings suggest that the continuous exposure to hypo- or mesoendemic malaria may induce significant anti-parasite and anti-disease immunity in native Amazonians.

[Infestation by triatomines in rural settlement and resettlement areas the Region of Pontal do Paranapanema, State of São Paulo]. / Infestação por triatomíneos em assentamentos e reassentamentos rurais na Região do Pontal do Paranapanema, Estado de São Paulo.

This study had the aim of assessing the characteristics of triatomine infestation in human dwellings in rural settlement and resettlement areas with regard to the time when infestation began. We analyzed data relating to 48 triatomine surveys carried out in 105 settlement areas and six resettlement areas in the region of Pontal do Paranapanema between January 1984 and June 2005. Among the 16 surveys in settlement areas, seven (43.8%) had positive findings, all of them in communities established eight or more years previously. Among the 32 surveys in resettlement areas, 23 (71.9%) had positive findings, all of them in communities established for periods shorter than eight years. Since the inhabitants of such communities frequently move, the need for constant vigilance to detect any cases of infestation by vector triatomines in new settlements cannot be overemphasized.

[Chagas Disease Control Program in the State of São Paulo: persistence of high triatomine infestation rates in some localities during the 1990s]. / Programa de Controle da Doença de Chagas no Estado de São Paulo: persistência de alta infestação por triatomíneos em localidades na década de 1990.

The purpose of our investigation was to analyze the persistence, in the State of São Paulo, of domiciliary units highly infested with Chagas disease triatomine vectors. Comprehensive epidemiologic information collected from 1990 to 1999 in the State of S o Paulo was retrieved from database files. Consistently high infestation rates were found in 43 localities distributed among 21 municipalities in the Ara atuba region. Captures produced predominantly peridomiciliary Triatoma sordida specimens, mostly adult females and fifth-instar nymphs, 94.6% of which containing ingesta negative for human blood. The houses, mostly inhabited (87.4%), were located near the residual woodland savanna in 64.3% of the localities. Poultry coops were found in association with 97.6% of all domiciliary units. Interestingly, in all the houses with persistent infestation, the inhabitants paid no evident attention to hygiene Lack of timely infestation control associated with the biological characteristics of the reduviid species involved, along with the conditions prevailing around the dwellings, favor the repeated invasion and consequent maintenance of colonization by triatomines.

[The efficiency of the examination of compressed fecal samples for Schistosoma mansoni eggs]. / Eficiência do diagnóstico coproscópico de Schistosoma mansoni em fezes prensadas.

The control of schistosomiasis depends mostly upon the sensitivity of stool examinations. We used both the Kato-Katz technique and the compression of samples between the slide and a polypropylene cover glass, according to Ferreira. Out of 1,282 samples collected between 1998 and 2000 in the Palha District, Municipality of Bananal, São Paulo State, Brazil, 105 (8.2 %) were positive. The first and second methods revealed 90 (7%) and 88 (6.9 %) positive cases, respectively. According to the kappa statistic, both methods were in agreement. In Bananal, the proportion of positive cases and egg per gram (epg) values are low, which calls for the examination of larger than usual volumes of feces. The viability of Schistosoma mansoni eggs can also be checked when using the second method, which dispenses with glycerin solution, measuring plates and sieves. The latter cause a further loss of precision in epg determinations.

[The Chagas Disease Control Program of the São Paulo State: the contribution of serology to the epidemiological investigation of triatomine-infested domiciliary units during the 1990s]. / Programa de Controle da Doença de Chagas no Estado de São Paulo: sorologia de moradores como parte de investigação de unidades domiciliares com presença de triatomíneos vetores na década de 1990.

The Chagas Disease Control Program in São Paulo State, Brazil, now in the entomological surveillance phase, includes a serological examination of individuals residing in domiciliary units infested with vector triatomines infected with Trypanosoma cruzi. From 1990 to 1999, this action included area in which triatomine searches were conducted either as a routine procedure, according to their levels of intra- or peridomiciliary infestation, or at the request of local residents. Among residents of the 1,415 UDs inspected, we collected 5,587 blood samples for serological examination, 87 of which (1.56%) tested positive, seven of which from individuals under 29 years of age. The species most frequently captured were Panstrongylus megistus, Triatoma sordida, and Triatoma tibiamaculata in the adult stage. No association was found between presence of seropositive residents and triatomines infected with Tr. cruzi (OR = 1.498; 0.875 < OR < 2.564, 95% C.I.). Our purpose was to use serological testing to investigate the situation of areas identifiable as being at risk of Chagas disease transmission and to compare the results with extant data about Tr. cruzi infection both in humans and vector triatomines.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): IV. Study on the public awareness of its risks in the Palha District.

A rather high prevalence of mansoni schistosomiasis has been observed in some localities of Bananal, State of São Paulo, during the past decade. The highest prevalence of schistosomiasis was found in the Palha District; it was thus considered adequate for an evaluation of public awareness of the risks involved in acquiring schistosomiasis, a likely outcome of certain behavior patterns. We interviewed 542 district-dwellers. The 5-to-39 age-group constituted 65.5% of the whole sample. Concerning the infection, 69.2% had hearsay information; 46.1% know the infection; 69.6% know how it is acquired; 31.5% know about the symptoms and 57.1% know what can be done to avoid infection; 17.7% declared to have acquired the infection at least once in their lifetime; 62.3% reported total or partial immersion in collections of water of Bananal, once or twice a week, 53.9% of these for bathing or fishing. Although most (91.7%) households have treated running water, are connected to the sewage network or have septic tanks, 9% of the people interviewed use to defecate on the field. It became clear that the educational messages aimed at this population had not been adequate, having failed to fulfil any expectations. The local people received only piecemeal and subjective information about their problem. The control of schistosomiasis requires an integrated practice, which includes the analysis of macro-determinant factors, such as basic sanitation, habitation, education and health care. In short, we require a multidisciplinary vision of the mechanisms of transmission of the infection, which depends upon adequate planning and well trained personnel, intent on their educational work, to attain satisfactory results.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): III. Seroepidemiological studies in the Palha District.

The Palha district, municipality of Bananal, State of São Paulo, Brazil, had 10.3% cases of Schistosoma mansoni diagnosed from 1994 to 2000 by coproscopy: about three times the municipality average. The immunofluorescent antibody test was used to assess gut-associated IgM antibody titers of samples from 452 inhabitants. It disclosed 129 (28.5%) positive cases. Subjects were classified according to age, sex, birthplace, and period of residence. Titers varied from 8 to 4,096 (geometric mean: 170.2). Seropositives were aged from 6 to 69 years (average: 24.5), 75% of them aged 34 or less, predominantly males (78 or 60.5%). Of all subjects, 65.7% were born and had been living in Bananal since; 24.2% came from neighboring municipalities and are residing in Bananal from two months to 89 years (average: 22.7 years). Further Kato-Katz coproscopy from 97 seropositives (geometric mean titer, 619) revealed S. mansoni eggs in 11 subjects (11.3%). Serology was deemed useful in screening subjects to be further investigated by coproscopy, considering that blood collection had better acceptance than supplying fecal samples. Higher than average serological titers may indicate new cases in endemic areas. Longitudinal studies associated with epidemiological investigation, including titer evolution are advised, as isolated data are difficult to interpret.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): II. Intermediate hosts.

We conducted monthly snail captures in Bananal, State of São Paulo, Brazil, between March 1998 and February 2001, to identify Schistosoma mansoni vectors, estimate seasonal population changes, and delimit foci. We also evaluated the impact of improvements in city water supply and basic sanitation facilities. We identified 28,651 vector specimens, 28,438 as Biomphalaria tenagophila, 49 of them (0.2%) infected with S. mansoni, and 213 as B. straminea, none of the latter infected. Vectors predominated in water bodies having some vegetation along their banks. Neither population density nor local vegetation could be linked to vector infection. We found the first infected snails in 1998 (from March to May). Further captures of infected snails ocurred, without exception, from July to December, when rainfall was least. Irrespective of season, overall temperature ranged from 16.5 degrees C to 21 degrees C; pH values, from 6.0 to 6.8. Neither factor was associated with snail population density. Frequent contact of people with the river result from wading across it, extracting sand from its bottom, fishing, washing animals, etc. Despite a marked reduction in contamination, cercaria shedding persists. Whatever the location along its urban course, contact with river Bananal, particularly of the unprotected skin, entails risks of infection.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): I. Efficiency of diagnostic and treatment procedures.

Bananal is an important focus of Schistosoma mansoni in the State of São Paulo. Accordingly, programmed active search for human cases, annual coproscopic surveys and treatment of infected cases were started in 1998, aiming at producing a sharp prevalence rate drop by the year 2000. S. mansoni eggs were searched for in two Kato-Katz slides per patient. Cases were followed up according to the routine of the local Family Health Program. In 1998, 130 samples out of 3,860 showed S. mansoni eggs; in 1999, 105 out of 3,550, and in 2000, 64 out of 3,528. Prevalence rates were 3.4%, 2.9%, and 1.8%, and average egg-counts 59, 64, and 79 eggs per gram of feces respectively. Prevalence rates decreased steadily after treatment, but persistently positive cases showed no significant decrease in parasite burdens. Egg count variation depended on sex and age bracket. Persistent residual cases admittedly preclude the eradication of this infection by only searching for and treating carriers. In addition, resistance to therapy and low sensitivity of fecal examinations, can not be ignored. Moderate to heavy worm burdens, frequently associated with hepatomegaly elsewhere, produced no serious cases in Bananal.