Immunological profiles of patients from endemic areas infected with Schistosoma mansoni

Crude extracts of eggs (SEA) adult worms (SWAP) or cercariae (Cerc) have been used to stimulate Peripheral Blood Mononuclear cells (PBMC) and have provided rather distinct profiles of responses in different types of patients. In genenral it is clear that patients with early infections respond strongly to SEA while response to SWAP are developed more slowly. As infection progresses into the more chronic phases, a general pattern is seen whic leads to lower anti-SEA proliferative responses in the face of higher responses to SWAP and variable anti-cerc responsiveness. Cured not re-exposed patients express very high levels of anti-SEA proliferation. It has recently been seen that those individuals who live in endemic areas and have continued water contact, but are reapeatedly stool-negative (who are presumed to have self-cured or be putatively resistant; endemic normals) are strongly responsive to antigenic extracts, particularly to SEA. Furthermore, our results show that endemic normal individuals have significantly higher IFN gamma production upon PBMC stimulation with schistosome antigens than infected individuals. With the emergence of more studies it is becoming apparent that both the intensity and the prevalence of a given area may influence or shape the general responsiveness of the population under study.

Cross-sectional and evolutive studies of schistosomiasis mansoni in untreated and mass treated endemic areas in the southeast and northeast of Brazil

Cross-sectional and evolutive studies on schistosomiasis mansoni were carried out before and after mass treatment in the endemic areas of Capitao Andrade and Padre Paraíso, state of Minas Gerais, Riachuelo, state of Sergipe, Alhandra, state of Paraíba, and Aliança, Alegre and Coroatá, lowland of the state of Maranhao, Brazil, in the last eighteen years. The studies included clinical and fecal examination by the Kato-Katz quantitative technique, skin testfor Schistosoma mansoni infection, evaluation of man-water contact and other epidemiological investigations such as infection rate and dynamic of the snail population. Results showed: (1) Higher prevalence of S. mansoni infection, greater egg load elimination and higher and earlier morbidity of the chronic froms of the disease in the southeast areas of Capitao Andrade and Padre Paraíso; (2) The incidence of hepatosplenic form is higher in some family clusters, in whites and mullattos in all the endemic areas but develop earlier in the southeast; (3) The prevalence and morbidity of schistosomiasis are decreasing both in the mass treated northeast and in the untreated southeast areas; (4) The mass treatment reduces rapidily the prevalence of the infection and the morbidity of the disease but can not control it because of the frequent reinfections due to the intensity of man-water contact.

Spatial and temporal distribution of anopheline larvae in two malarious areas in Sucre State, Venezuela

The spatial and temporal distribution of anopheline larvae was studied in two coastal malarious areas of Sucre, State, Venezuela. Seven habitat types were sampled in the village of Guayana and eight species of Anopheles were collected. Anopheles aquasalis was the predominant species collected and was most abundant in the brackish marsh habitat (71 larvae per 100 samples). It was most abundant during the rainy season. At the second location, Santa F e, six habitat types were sampled and four anopheline species were collected. Habitats where An. aquasalis was most abundant were temporary freshwater ponds (34 larvae per 100 samples) and mangroves (10.5 larvae per 100 samples). At this location it was also most abundant in the rainy season. During the dry season it was collected in small numbers in river pools (1.3 larvae per 100 samples) along with large numbers of An. pseudopunctipennis (479 larvae per 100 samples). Larval control could be an important component of the malaria control program because major habitats could be defined and presence and abundance of larvae was limited to specific times of year.

Adult abundance, biting behavior and parity of Anopheles aquasalis, Curry 1932 in two malarious areas of Sucre State, Venezuela

The principal vector of malaria in eastern Venezuela, Anopheles aquasalis, is exophagic and exophilic. Control using indoor insecticide house sprays has failed to lower the number of malaria cases. Therefore, studies were initiated in two villages of the eastern coastal state of Sucre to better understand this vector's biology and develop a more integrated control program. An. aquasalis was found to have a crepuscular biting behavior with a major peak at dusk and a minor peak at dawn. Mosquitos were collected more outdoors than indoors. Forty-seven percent of the biting took place before people went to bed (22:30 hr) and 69% of the mosquitos biting during this time period bite outdoors. Outdoor biting could be the reason why indoor spraying alone did not lower malaria cases. Seasonal abundance was greater in the rainy season compared to the dry season. Seasonal parous rates were high (78.3%-100%) and similar indoors and outdoors and between dry and wet season in Santa F e. In Guayana, the seasonal parity was lower (34.6%-42.2%) than Santa F e with indoor parity slightly higher than outdoors. Malaria cases were higher in Santa F e, but adult mosquito density was much lower than in Guayana. This difference could have been due to higher parity in Santa F e compared to Guayana. The greater distance to the nearest breeding site and presence of alternative hosts in Guayana can not be discounted as factors which contributed to the difference in malaria transmission between locations. We concluded that knowledge on seasonal occurrence, biting activity, resting behavior and breeding site location can be used to design a new control strategy for this vector.

The geographic understanding of snail borne disease in endemic areas using satellite surveillance

The current status of research on use of earth observing satellite sensors and geographic ifnormation systems for control program management of schistosomiais and fascioliasis is reviewed.

Inter-relation of sylvatic and domestic transmission of Trypanosoma cruzi in areas with and without domestic vectorial transmission in Minas Gerais, Brazil

During the period 1980-1986, we captured triatomine bugs and mammalian reservoir hosts from sylvatic and domestic situations in different municipalities of the State of Minas Gerais. Trypanosoma cruzi was isolated from captured bugs, mammals and patients. After cultivation in LIT medium, the electrophoretic enzyme profiles were determined. We obtained atotal of 32 parasite isolates from regions with active domestic transmission, and 24 isolates form areas under control. For the first areas the results suggest introduction of T. cruzi from sylvatic habitats, through incursion of infected opossums and/or sylvatic T. sordida, which appears to have given rise to at least one acute human infection. Of particular interest is the finding of sylvatic opossums and a T. sordida nymph infected with ZB, that could indicate return of parasites from chronic human infections to sylvatic transmission cycles. For the areas under control we also interpret the results as interaction between sylvatic and domestic cycles of transmission, here through the invasion of houses by bugs carrying the Z1 zymodeme from the sylvatic environment. The Multivariate Correspondence Analysis gives a spatial description between the different parasite isolates and confirms the existence of a bridge in the opposite direction in the region with active vectorial transmission including the exporting of Z2 through the peridomestic environment into the sylvatic cycle. For the others areas this bridge corresponds especially to Panstrongylus megistus, importing Z1 into the domestic environment.

A Comparison of Two Brazilian Populations of Culex quinquefasciatus (Say, 1823) from Endemic and Non-endemic Areas to Infection with Wuchereria bancrofti (Cobbold, 1877)

Culex quinquefasciatus is known to be an efficient insect host of Wuchereria bancrofti. In Brazil Cx. quinquefasciatus is widely distributed throughout the country and is often abundant in and around human habitations. In contrast, Bancroftian filariasis is limited to three foci in Brazil. Experiments were undertaken to compare the vector capacities of Cx. quinquefasciatus originating from Maceió (Alagoas), one of the endemic areas of W. bancrofti infection in Brazil, and Belo Horizonte (Minas Gerais), a non endemic area. Laboratory-reared Cx. quinquefasciatus were dissected 20 days after blood feeding on microfilaraemic patients. Survival rates and the number of infective larvae that developed did not differ in female mosquitoes of different origins. Thus both populations of Culex were susceptible to infection with W. bancrofti

Attempts to Improve Xenodiagnosis: Comparative Test of Sensibility Using Rhodnius neglectus, Panstrongylus megistus, Triatoma vitticeps and Triatoma infestans in Endemic Areas of Brazil

From June 1984 to July 1992, 392 xenodiagnostic tests were applied on 264 patients with chronic Chagas disease from Brazilian endemic areas of Virgem da Lapa and Coronel Murta, situated in the Jequitinhonha Valley, in the State of Minas Gerais. The susceptibilities of Rhodnius neglectus, Panstrongylus megistus, Triatoma vitticeps and Triatoma infestans were compared. Most of the time 20 nymphs (fourth instar) of each species were applied to 161 women and 103 men aged between 5 and 83 years of age. The tests were prepared to compare the susceptibilities of two species at a time, using the same patients for each test. Results showed a xenopositiveness of 26.28% (103 tests) being 27.98% in women (68 positive in 243 applied tests) and 23.49% in men (35 positive in 149 applied tests). The relative frequency of xenopositiveness displayed a great superiority of P. megistus and T. vitticeps. In tests from type I, for example, P. megistus was the unique responsible for 10.73% of positive xenodiagnosis vs. only 0.98% in T. infestans. Other parameters analized in this work confirm this superiority, and corroborate that T. infestans can be replaced by P. megistus and /or T. vitticeps in order to upgrade the efficacy of xenodiagnosis

Antibodies anti Bloodstream and Circumsporozoite Antigens (Plasmodium vivax and Plasmodium malariae/P. brasilianum) in Areas of Very Low Malaria Endemicity in Brazil

During 1992-1994, 33 malaria cases were reported in two regions in Brazil where few sporadic atypical cases occur, most of them in home owners, who are weekenders, while home caretakers live there permanently. Indirect Fluorescent Antibody Test (IFAT), with Plasmodium vivax, and Enzime Linked Immunosorbent Assay (ELISA) with repeat peptides of the circumsporozoite (CS) proteins of the 3 known P. vivax variants and P. malarie/P. brasilianum, were performed on 277 sera, obtained within a 5 to 10 km range of malaria cases. Very rarely did any of these donors recall typical malaria episodes. Blood smears of all but 5 were negative. One of the 5 malaria cases included in our serology was of a home owner, 1 of a permanent resident, 3 from Superintendência de Controle de Endemias employees who went there to capture mosquitoes. In Region 1 the prevalence of IFAT positive sera was 73% and 28% among caretakers, 18% and 9.6% among home owners. In Region 2 (3 localities) no distinction was possible between caretakers and home owners, IFAT positivity being 38%, 28% and 7%. The relative percentage of positive anti-CS repeats ELISA, differed for each of the peptides among localities. Dwellings are in the vicinity of woods, where monkeys are frequently seen. The origin of these malaria cases, geographical differences and high seropositivity is discussed

Epidemiological Characteristics of Schistosoma mansoni Infection in Rural and Urban Endemic Areas of Minas Gerais, Brazil

To compare the epidemiological profile and socioeconomic factors associated to the infection by Schistosoma mansoni in a rural and an urban endemic area a cross-sectional study was performed in Água Branca de Minas (rural area) and Bela Fama (urban area), both situated in the State of Minas Gerais, Brazil. Two hundred and eighty eight individuals were surveyed in the rural area and 787 in the urban area. Water contact and socioeconomic questionnaires were used to identify risk factors for the infection. The prevalences of 38.8% and 9.7% and the geometric mean of eggs per gram of faeces of 117.8 and 62.3 were found in the rural and urban areas, respectively. By multivariate statistical analysis age groups over nine years old and previous specific treatment were associated with the infection in rural area. In urban area age over nine years old, low quality housing, weekly fishing and swimming were associated after adjustment by logistic regression

Factors Involved in Schistosoma mansoni Infection, in Rural Areas of Northeast Brazil

Two contiguous villages in Tracunhaém county (State of Pernambuco), endemic for schistosomiasis, were studied: Itapinassu (138 inhabitants) and São Joaquim (91 inhabitants). Agriculture predominates in the former region while ceramics is the main activity in the latter. Although no statistical difference was found regarding prevalence, severe infection (>400 epg) predominated in Itapinassu, probably related to the kind of occupation. No association was found between parasite burden and severity of disease, in spite of the high infection rates for Schistosoma mansoni in both communities (approx. 60%). Typical epidemiological features of schistosomiasis such as age-related prevalences and intensities of infection (high in children, low in adults) were also mutual characteristics. Nutritional status determined through anthropometric evaluation was carried out by measuring specific anthropometric indicators. A deficit of energy intake, as well as vitamin A and riboflavin deficiencies were detected. The prevalence of moderate or severe undernutrition in patients under 18 years old was 21.9% in Itapinassu and 24.1% in São Joaquim. In this group an association was found between prevalence of schistosomiasis and chronic undernutrition. Similarly, for patients over 18 year old the prevalence of undernutrition was higher than 20%. However, in this case no association between nutritional status and either prevalence of schistosomiasis or parasite burden could be detected. The two communities had not been treated for eight years.

A New Species of Simulium (Diptera: Simuliidae) from Open Areas in Central Amazonia, Brazil

The larva, pupa, male and female of Simulium daltanhani n. sp. are described and illustrated. This species shares diagnostic characteristics with Simulium quadrifidum Lutz, Simulium cauchense Floch & Abonnenc, Simulium brevifurcatum Lutz and Simulium siolii Py-Daniel. It was collected in three counties (Manaus, Presidente Figueiredo and Itacoatiara) in the State of Amazonas, Brazil. Its habitat includes streams in disturbed, open areas where the forest has been cut for road construction; it was not collected in adjacent forested streams, suggesting that it colonizes disturbed habitats. The larval subesophageal ganglion is discussed as a useful character, when pigmented, to distinguish this species within a limited geographic area.

Ecology of mosquitoes (Diptera: Culicidae) in areas of Serra do Mar State Park, State of São Paulo, Brazil. I - Monthly frequency and climatic factors

The ecology of mosquitoes were studied (Diptera: Culicidae) in areas of Serra do Mar State Park, State of São Paulo, Brazil. Systematized monthly human bait collections were made three times a day, for periods of 2 or 3 h each, in sylvatic and rural areas for 24 consecutive months (January 1991 to December 1992). A total of 24,943 specimens of adult mosquitoes belonging to 57 species were collected during 622 collective periods. Coquillettidia chrysonotum was the most frequent collected mosquito (45.8%) followed by Aedes serratus (6.8%), Cq. venezuelensis (6.5%), Psorophora ferox (5.2) and Ps. albipes (3.1%). The monthly averages of temperature and relative humidity were inserted in the ten-year average limits of maximum and minimum of the previous ten-years. Rainfall accompanied the curve of the ten-year averages. Those climatic factors were influential in the incidence of some species; temperature: Anopheles cruzii, An. mediopunctatus, Ae. scapularis, Ae. fulvus, Cq. chrysonotum, Cq. venezuelensis, Runchomyia reversa, Wyeomyia dyari, Wy. confusa, Wy. shannoni, Wy. theobaldi and Limatus flavisetosus; relative humidity: Ae. serratus, Ae. scapularis, Cq. venezuelensis and Ru. reversa; rainfall: An. cruzii, Ae. scapularis, Ae. fulvus, Cq. venezuelensis Ru. reversa, Wy. theobaldi and Li. flavisetosus.