Parasitismo natural de bufalinos em Botucatu, SP, Brasil: III. Dinâmica do parasitismo gastro-intestinal em vacas e suas crias

Gastro-intestinal parasitism of 24 buffalo cows before parturition, and post-parturition, their infection and that of their respective calves during the following 30 weeks were studied. Willis, Hoffmann and whenever possible, the modified Gordon & Whitlock techniques were used for fecal examinations. Toxocara vitulorum eggs were the earliest forms encountered in calves feces, as follows: during the 1st week after birth, 58.33% of the calves were positive, and in the 4th week, 100% of these animals were positive. Eggs of Strongyloides sp were in the 1st week after birth in two of the calves and in the 5th week, all for them were positive. The next parasites to appear were the Coccidia of which oocysts were detected in the feces of two calves in the 2nd week after birth, and 58.33% of the calves were positive for these in the 3rd week, and in the 6th week, all calves shed oocysts in their feces. On the other hand, eggs of Strongylids were the last forms to appear in calves feces. However, despite their sporadic appearance in the feces, eggs of these parasites were observed continuously from the 11th week onwards, and at this point, the percentage of positive samples began to increase to reach its peak. Relatively to adult animals, eggs of T. vitulorum were observed in the feces of 11 cows, one or twice at most; eggs of Strongyloides sp were seen only once in the feces of four buffalo cows and eggs of Strongylids in 21 out of 24 cows. Oocysts of Coccidia were observed in 16 cows. Mechanisms of infestation of calves with these parasites are discussed.

Nomimoscolex touzeti n. sp. (Cestoda), a parasite of ceratophrys cornuta (L.): first record of a monticellidae in an amphibian host

Nomimoscolex touzeti n. sp. is described from one Ceratophrys cornuta (L.) caught in Amazonian Ecuador. Its taxonomic relationships to the others species are discussed. This new species is characterized by a cortical position of vitellaria; by the presence in the uteroduct of conglomerates of 20-40 eggs; by a weak ovary width/proglottis width ratio; by ventral excretory canals anastomosed; by a powerful vaginal sphincter and by a long cirrus. N. touzeti is the first record of Monticellidae in an amphibian host.

Estudos bionômicos de Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae): III. Dinâmica populacional

A population dynamics study of D. maximus was caried out under laboratory condictions (28-C e 65% ñ 5% U.R.) and the methodology was the same that have been used for hearing this insects. In order to evaluate the population growth rate of this species, during a 24 months period, five colonies started with a couple recently emerged were observed. Each couple (a male and a female) was mantained in a glass container measuring 20 cm of diameter and 20 cm in height with filter paper on the botton. The insects were monthly feeding with normal mice blood, and at this day the number of eggs, nymphal stages and adults was registered. All graphical representations of the populations growth rate showed the same shape. It was found that the average of nymphal stage represented 64.31% of the hole population whereas the oviposition curved showed to be inverse to this one (28.57%) a small percentage of adults was found: males 3.85% and females 3.12%. In this study observations on the biologycal cycle, longevity and fertility rates were also carried out.

Fecundity of Biomphalaria straminea and B. glabrata in the laboratory: a twelve-month comparative study

In the present comparative study a Biomphalaria straminea sample from Picos (Piauí) showed expressive advantages related to fecundity over a B. glabrata sample from Belo Horizonte (Minas Gerais) such as: higher egg-mass production in 10 out of 12 months of study; higher egg production in all months of study; higher egg per egg-mass ratio in 11 out of 12 months of study; 66% of the egg-masses containing more than 20 eggs while in B. glabrata 70% of the egg-masses showed less than 20 eggs; three times less empty egg capsules than B. glabrata; attainning maximum fecundity in half the time required by B. glabrata. Mortality however was higher and sooner in B. straminea, suggesting higher semelparity in this species than in B. glabrata, a possibility that requires confirmation through long-term studies with other samples of both species. This first finding of a B. straminea sample more fecund than B. glabrata is discussed in relation to other data from the literature, and some recommendations are made on the quantification of fecundity of planorbid snails.

Dispersão geopolítica da ocorrência de Fasciola hepatica no Estado de Santa Catarina, Brasil

During 12 years feces samples from cows, water buffaloes, sheeps and goats were examined by sequencial tamis filtration to show the occurence of Fasciola hepatica eggs. The material came from 129 municipalities of Santa Catarina State, and 5 g of feces per animal were examined. The occurrence of F. hepatica was confirmed in 64.82% of the municipalities. Considering the host, F. hepatica was confirmed in goats from Florianópolis, São José, São João Batista and Guaramirim municipalities; in sheeps from Brusque, Pomerode, Palhoça and São José; in water buffaloes from 9 and in cows from 86 municipalities. For this study, 13,762 feces samples were examined and in 3,814 the presence of eggs of F. hepatica was demonstrated. The percentage of occurence for host species was 27.86 in cows, 24.72 in water buffaloes, 16.92 in sheeps and 15.66 in goats. By the results it was demonstrated that Itajaí Valley at Southest Hidrographic Basin, in Santa Catarina State is an endemic area of F. hepatica, even though Uruguai Hidrographic Basin was not referred as a geographical record for this parasite.

Natural infection of wild rodents by Schistosoma mansoni parasitological aspects

The evaluation of the role of rodents as natural hosts of Schistosoma mansoni was studied at the Pamparrão Valley, Sumidouro, RJ, with monthly captures and examination of the animals. Twenty-three Nectomys squamipes and 9 Akodom arviculoides with a shistosomal infection rate of 56.5% and 22.2% respectively eliminated a great majority of viable eggs. With a strain isolated from one of the naturally infected N. squamipes, we infected 75% of simpatric Biomphalaria glabrata and 100% of albino Mus musculus mice. The adult worms, isolated from N. squamipes after perfusion were located mainly in the liver (91.5%) and the mesenteric veins (8.5%). The male/female proportion was 2:1. The eggs were distributed on small intestine segments (proximal, medial and distal portions) and the large intestine without any significant differences in egg concentration of these segments. In A. arviculoides, the few eggs eliminated by the stools were viable and there was litlle egg retention on intestinal segments. Considering the ease to complete S. mansoni biological cycle in the Nectomys/Biomphalaria/Nectomys system under laboratory conditions, probably the same is likely to occur in natural conditions. In support to this hypotesis there are also the facts that human mansonic shistosomiasis has a very low prevalence in Sumidouro and endemicity among the rodents has not changed even after repetead treatments of the local patients. Based on our experiments, we conclude that N. squamipes has become a natural host of S. mansoni and possibly may participate in keeping the cycle of schistosomiasis transmission at Pamparrão Valley.

Nectomys squamipes (Rodentia: Cricetidae) as an experimental model for schistosomiasis mansoni

Twenty specimens of Nectomys squamipes born in captivity, were infected with 500 cercariae by the transcutaneous route. Coprologic examinations were carried out from the 5th to 23rd week after infection. On the 7th, 8th, 12th, 16th, and 23rd weeks the animals were sacrificed and perfused. The oogram was performed in segments of the small intestine (proximal, medial and distal portions) and the large intestine. The average pre-patent period was of 42 days. The average number of eggs varied from 350 on 6th week, to 800 on the 13th. From the 14th week on, the average number of eggs eliminated was lower than 50 per gram of feces. The recovery of worms kept steady on the 7th, 8th, and 12th week (16.85%; 15.45% and 11.95%), decreasing to 7.70% on the 16th week and 8.45% on the 23rd week. The proportion of male/female worms was about the same on the first two weeks, but from the 12th week on, the proportion was: 1,4/1 on the 12th week; 2,5/1 on the 16thweek and 1,8/1 on the 23rd weekThese observations suggest that N. squamipes may used as an experimental model for schistosomiasis mansoni, to wich it develops resistance mechanism, useful for immunity studies.

The role of cytokines in the pathogenesis of hepatic granulomatous disease in Schistosoma mansoni infected mice

Cytokines are important in the cell-mediated response to Schistosoma mansoni eggs. We have found that Th2 cytokine responses (e.G. IL-4 and IL-5) are argumented after egg laying begins while the response (IL-2 and IFN-*) are down regulated in S. mansoni infected mice. Treatment of mice with anti-IL-5 monoclonal antibodies (Mab) suppressed the eosinophil response almost completley but did not affect granuloma size and slightly increased hepatic fibrosis. Anti-IL-4 treatment abolished IgE responses in infected mice and decreased hepatic fibrosis slightly. Anti-IFN-* treatment had no effect on hepatic pathology. Anti-IL-2 treatment decreased granuloma size significantly and decreased hepatic fibrosis markedly. Anti-IL-2 treatment dramatically decreased IL-5 secretion by splenic cells in vitro and decreased peripheral blood and tissue eosinophilia. In contrast IL-4 secretion was unaffected and serum IgE was normal or increased. IL-2 and IFN-* secretion by splenic cells of treated mice were slightly but not significantly increased suggesting that anti-IL-2 treatment affecting Th2 rather than Th1 responses.

Morphological features of collagen degradation in advanced hepatic schistosomiasis of man

Optical and electron microscopical evidences of focal matrix degradation were frequently seen in liver sections taken from patients with periportal ("pipe-stem") fibrosis caused by schistosomiasis mansoni. Besides present of focal areas of rarefaction, fragmentation and dispersion of collagen fibers, the enlargend portal spaces also showed hyperplasia of elastic tisue and disarray of smooth muscle fibers following the destrution of portal vein branches. Ultrastructural cahnges represented by focal lytic and/or electron dense alterations of colagen fibrils were similar to those first seen in experimental material and designated as "chronic collagen degradation". Elastin and related microfibrils were also affected by focal condensation, fragmentation, distorsion and dissolution. Schistosome eggs were scanty in the tissue sections examined. Matrix degradation represented involuting changes related to the progressive diminution of parasite aggression, which occurs spontaneously with age or after cure by chemotherapy. Changes of focal matrix degradation now being described represent the basic morphological counterpart of periportal fibrosis involution documented clinically, especially by ultrasonography, in patients with hepatosplenic schistosomiasis submitted to curative chemotherapy.

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.

Effector functions of eosinophils in schistosomiasis

The dual function of eosinophils is clearly illustred in schistosomiasis. Well equipped in membrane receptors for immunoglobulins and complement, and due to the presence of granule basic proteins, eosinophils can become cytotoxic for parasite larvae and thus participate to protective immunity. However mediators can also exert their cytolytic effect on normal cells or tissues, inducing therefore pathology. Through ADCC mechanisms against schistosome larvae in vitro involving different antibody isotypes (IgG, IgE and IgA) and also in experiments performed in vivo, eosinophils have been clearly involved in protective immunity. Although no direct evidence of the protective role of eosinophils were brought in humans, the striking association of eosinophil-dependent cytotoxic antibody isotypes with resistance to reinfection (for instance IgE and IgA antibodies), whereas in vitro blocking antibody isotypes (IgG4, IgM) were detected in susceptible subjects, strongly, suggested the participation of eosinophils in antibody-dependent protective immune response. However eosinophils could also participate to granuloma formation around S. mansoni eggs and consequently to the pathological reactions induced by schistosomiasis.

Experimental murine schistosomiasis mansoni: estabilishment of the chronic phase of the disease

After the acute hyperergic phase of schistosomal infection, the chronic phase of the disease corresponds to the estabilishment of a relative equilibrium between the host and the parasite. This involves: (1) A shift from the predominance of the TH2 response observed in the acute phase, to the predominance of the TH1 response in the chronic phase of the disease, with modification of lymphokine and immunoglobulin secretions patterns. (2) Redistribution of hosts responses to parasite, with predominance of systemic controls in the acute phase, and a shift towards local tissue responses in the chronic phase. This redistribution relieves the hyperergic responses involving the whole body of the host, and delimits cellular and molecular reactions to parasites to only those tissues that are directly involved by the adult parasites and their eggs. Mobilization of eosinophil granulocytes in schistosomal periovular granulomas is one of examples of this redistribution.

Age-targeted chemotherapy for control of urinary schistosomiais in endemic populations

Severity of urinary tract morbidity increases with intensity and duration of Schistosoma haematobium infection. We assessed the ability of yearly drug therapy to control infection intensity and reduce S. haematobium-associated disease in children 5-21 years old in an endemic area of Kenya. In year I, therapy resulted in reduced prevalence (66% to 22%, P < 0.001) and intensity of S. haematobium infection (20 to 2 eggs/10 mL, urine), with corresponding reductions in the prevalence of hematuria (52% to 19%, P < 0.001). There was not, however, a significant first-year effect on prevalence of urinary tract abnormalities detected by ultrasound. Repeat therapy in years 2 and 3 resulted in significant regression of hydronephrosis and bladder abnormalities (41% to 6% prevalence, P< 0.001), and further reductions in proteinuria. Repeat age-targeted therapy was associated with decreased prevalence of infection among young children (< 5yr) entering into the target age group. Two years after discontinuation of therapy, intensity of S. haematobium infection and ultrasound abnormalities remained suppressed, but hematuria prevalence began to increase (to 33% in 1989). Reinstitution of annual therapy in 1989 and 1990 reversed this trends. We conclude that annual oral therapy provides an effective strategy for control of morbidity due to S. haematobium on population basis, both through regression of disease in treated individuals, and prevention of infection in untreated subjects.

New approaches for the control and eradication of schistosomiasis in Venezuela

Schistosomiasis in Americawith the exception of Brazil, behaves as a chronic mild disease with few clinical manifestations due to low parasite burden. These features restrict the clinical and parasitological diagnosis. The most commonly used stool examination method, Kato-Katz, becomes intensitive when the majority of individuals excrete less than 100 eggs/g of feces. In view that antigen-detecting techniques have not been able to reveal light infections, the antibody detecting assays remain as a very valuable diagnostic tool for epidemiological surveillance. The Venezuelan Schistosomiasis Research group (CECOICE) has designed a mass chemotherapy strategy based on sero-diagnosis. Since blood sampling is one of the important limitating factors for large seroepidemiological trials we developed a simple capillary technique that sucessfully overcomed most of the limitations of blood drawing. In this sense, ELISA seems to be the most adecuate test for epidemiological studies. Soluble egg Schistosoma mansoni antigen (SEA) has been largely used in Venezuela. The sensitivity ELISA-SEA in our hands is 90% moreover its specific reach 92% when populations from non-endemic areas but heavily infected with other intestinal parasites are analyzed. The Schistosomiasis Control Program is currently carrying out the surveillance of endemic areas using ELISA-SEA as the first screening method, followed by the Circumoval Precipitin test for validation assay. The results with these two serological techniques allowed us to defined the criteria of chemotherapy in populations of the endemic areas. On the search of better diagnostic technique, Alkaline Phosphatase Immunoenzyme Assay (APIA) is being evaluated in field surveys.

Controle da esquistossomose mansônica em área de baixa transmissao

The schistosomiasis is transmitted by Biomphalaria tenagophila in our study area (Pedro de Toledo, Sao Paulo, Brazil). From 1980 to 1990 epidemiological surveys in a population of 4.000 inhabitants, has shown that: prevalence Kato-Katz (KKT), immunofluorescence (FT) and intradermal (IDT) techniques were 22.8%, 55.5% and 51.8% respectively; intensity of infection was low, 58.5 eggs per gram of faeces (epg); there were no symptomatic cases; prevalences were higher in mates, children and rural zone; index of potential contamination was 57.5% in the age group 5 to 20 years; 2/3 of patients were autochtonous; cases were no-randomly aggregated; transmission was focal and only 0.4% of snails were infected; water contacts through recreation showed the most important odds ratio; knowledge, attitudes and practices were satisfatory. From the epidemiological control findings a control programme was carried out; yearly faeces exams, chemotherapy, molluscocide, health education and sanitation. Thus, the prevalence decreased sharply to 3.3% and intensity of infection to 30.3 epg; the incidence rates ranged between 0.4% and 2.5% annualy; the sanitation became better and the youngsters were the main target in prophylaxis. To improve control, immunodiagnosis has to be conducted and the involvment of the population should be increase. However, we cannot forget that re-infection and the involvment of the population should be increase. However, we cannot forget that re-infection, therapeutic failure, etc, could play a major role in the maintnance this residual prevalence.