A Study of Cryptosporidium parvum Genotypes and Population Structure

Genetic evidence for the occurrence of two Cryptosporidium parvum subgroups is presented. This evidence is based on restriction fragment length polymorphism analysis of several independent loci. Sequence analysis of the b -tubulin intron revealed additional polymorphism. The stability of the genetic profiles following passage of C. parvum isolates between different hosts was investigated.

Seroprevalence of Trypanosoma cruzi Infection in Students at the Seven-Fourteen Age Range, Londrina, PR, Brazil, in 1995

Seropositivity for Chagas disease was evaluated in 834 children aged between 7 and 14 from the Municipal Teaching System in the district of Londrina, State of Paraná. A seroprevalence rate of 0.1% was found through the use of an indirect immunofluorescent test and an enzyme-linked immunosorbent assay. This low rate of seroprevalence provides evidence that the vectorial transmission of Chagas disease has been eliminated in Londrina. The main reason for the elimination of vectorial transmission of Trypanosoma cruzi infection, as evaluated by serological tests, may be a remarkable change in the economic structure of the northern region of Paraná in the 1960's. At that time coffee production was almost completely replaced by soy beans, wheat and grazing in the rural areas. This change deeply affected the rural ecology and caused an exodus of the population from rural to urban areas as well as a decrease in the total number of the population of that region. The measures introduced for controlling the disease through the Program of Chagas Disease Control established by the Fundação Nacional de Saúde of the Brazilian Ministry of Health, certainly, had a positive impact on the reduction of American trypanosomiasis prevalence in the area under study. However, it does not seem that this was the most relevant factor responsible for the elimination of vectorial transmission of Chagas disease in Londrina.

Haemolymph and Fat Body Metallo-protease Associated with Enterobacter cloacae Infection in the Bloodsucking Insect, Rhodnius prolixus

Analysis of zymograms with SDS-polyacrilamide gel electrophoresis containing gelatin as substrate, and performed on samples of haemolymph or fat body taken from Rhodnius prolixus inoculated or not with Enterobacter cloacae, demonstrated distinct patterns of protease activities: (i) in the haemolymph two proteases were induced in insects inoculated with bacteria; (ii) two proteases were detected in the fat bodies derived from non-inoculated controls or insect inoculated with sterile culture medium; (iii) haemolymph and fat body had both the same apparent molecular weights proteases (46 and 56 kDa); and (iv) these enzymes were characterized as metallo-proteases. The association of these enzymes in Rhodnius infected with bacteria was discussed.

Ultrastructural Details of Cryptosporidium parvum Development in Calf Intestine

Cryptosporidium parvum and C. muris appear to be different species found in calves, with different oocysts size and distribution on the gastrointestinal tract. This work presents new images of C. parvum ultrastructure in calf intestine, mainly its development in nonmicrovillous cells and the presence of microtubular structures in the membrane enveloping the macrogamonts and immature oocysts.

Experimental Infection of Swine by Isospora suis Biester 1934 for Species Confirmation

A survey of Isospora suis performed in 177 faecal samples from 30 swine farms detected thin wall type I. suis oocysts in seven samples. This type of oocyst measuring 23.9 by 20.7 mm had a retracted thin wall similar to that of the genus Sarcocystis. This type of oocysts, isolated from four different faecal samples, was inoculated in four-five-days-old piglets free of contamination in order to verify the life cycle and pathogenicity of the species. The pigs were kept in individual metal cages and fed with cow milk. Daily faecal collections and examinations were performed until the 21st day after infection. MacMaster and Sheather' s methods were used for oocyst counting and identification. Infected piglets produced yellowish-pasty diarrhoea with slight dehydration. The prepatent and patent periods were respectively from 6 to 9 and 3 to 10 days after infection. Oocyst elimination was interrupted on the 10th and 11th days after infection with biphasic cycles. Thin and thick wall oocysts were detected in the same faecal samples. Thin walls were not observed in unsporulated oocysts. The observations suggest that this type of oocysts could appear in specific strains which occur in the later stages of their development. These oocysts seem to be responsible for clinical and pathogenic signs of neonatal isosporosis in pigs.

Experimental Infection of Culex (Culex) quinquefasciatus and Aedes (Stegomyia) aegypti with Wuchereria bancrofti

A study was conducted to determine the susceptibility of local strains of Culex quinquefasciatus and Aedes aegypti to infection with the strain of Wuchereria bancrofti that occurs in Maceió, State of Alagoas, Brazil. Cx. quinquefasciatus blood fed simultaneously on the same microfilariae carrier ingested more blood and 2-3x more microfilariae than Ae. aegypti. Survival rates of both species of insects living for 21 days after blood feeding on microfilaraemic patients were not significantly different from the survival rates of mosquitoes that blood fed on amicrofilaraemic individuals. W. bancrofti parasites underwent normal development in Cx. quinquefasciatus, with third stage larvae first being recorded on the 11th day post infection, and their numbers increasing thereafter. Development of filariae in Ae. aegypti did not proceed beyond the first larval stage, and there was a progressively increasing number of non-viable larvae with the passage of time. It is concluded that Ae. aegypti is not involved in the transmission of W. bancrofti in Maceió.

The Effects of a DNA Virus Infection on the Reproductive Potential of Female Tsetse Flies, Glossina morsitans centralis and Glossina morsitans morsitans (Diptera: Glossinidae)

Reproductive anomalies associated with the tsetse DNA virus infection in the female tsetse hosts, Glossina morsitans centralis Machado and Glossina morsitans morsitans Westwood, inoculated with the virus during the 3rd instar larval stage were studied and the data compared to those obtained from the control females injected with sterile physiological saline. Virus infected flies had significantly longer first and second pregnancy cycles (P<0.0001) and produced pupae that were of significantly less weight in milligrams (P<0.0001) compared to controls. Transmission of the virus to progeny was not absolute and only 21% of G. m. centralis and 48% of G. m. morsitans first progeny flies from infected females developed salivary gland hypertrophy as a result of transmission from mother to progeny. The virus infected females produced significantly fewere pupae compared to the controls during the experimental period (P<0.00001).

Effects of Schistosomal mansoni infection on Calomys callosus coelom-associated lymphomyeloid tissue (milky spots)

Calomys callosus Rengger, 1830 (Rodentia: Cricetidae) is a mouse-like South American wild rodent, which is permissive to Schistosoma mansoni infection. In this paper we studied the effect of schistosomal infection in C. callosus mesenteric and omental milky spots (MS), subsidiary foci of coelom-associated lymphomyeloid tissue (CALT), during the acute, transitional (acute to chronic), and chronic phases of the infection. MS were morphologically analyzed by histological methods, using brigthfield and confocal laser scanning microscopies. The MS of infected animals were mainly of lymphomyelocytic (42 to 90 days) and lymphoplasmacytic (160 days of infection) types and showed frequent presence of lymphoid follicles with germinal centers, plasmacytogenesis and plasmacytosis, mastocytosis, megakaryopoiesis, erythropoiesis and less pronounced eosinopoiesis. These results indicate that MS are a preferential site of germinal-center-dependent and independent plasmacytogenesis, and a bone marrow-like organ, committed with various cellular lineages. The consequence of C. callosus MS reactivity for schistosomal infection is still unknown and is under investigation.

Histopathologic features associated with susceptibility and resistance of biomphalaria snails to infection with Schistosoma mansoni

Resistance and susceptibility of Biomphalaria snails to Schistosoma mansoni sporocysts occur in different degrees. Histopathology reflects these diferences. In a state of tolerance numerous sporocysts in different stages of differentiation are seen in the absence of host tissue reaction. However extensive diffuse and focal proliferation of amebocytes with sequestration and destruction of many parasitic structures appear in resistant snails. Some snails are totally resistant and when exposed to infecting miracidia may never eliminate cercarie. Sequential histopathological examination has revealed that in such cases the infected miracidia are destroyed a few minutes to 24 hr after penetration in the snail. However, B. glabrata that were exposed to S. mansoni miracidia and three moths later failed to shed cercariae, exhibited focal and diffuse proliferation of amebocytes in many organs in the absence of pasitic structures. These lesions were similar to those observed in resistant snails that were still eliminating a few cercariae, with the difference that no recognizable sporocystic structures or remmants were present. Histological investigation carried out in similarly resistant B. tenagophila and B. straminea presented essentially normal histologic structures. Only occasionally a few focal proliferative (granulomatous) amebocytic reactions were seen in ovotestis and in the tubular portion of the kidney. Probably, there are two types of reactions to miracidium presented by totally resistant snails: one would implicate the immediate destruction of the miracidium leaving no traces in the tissues; the other involving late reactions that seem to completely destroy invading sporocysts and leave histological changes.

Induction of protective immunity against Schistosoma mansoni infection by antigens purified from PIII, a fraction of adult worm, associated to the downregulation of granuloma formation

This study was performed in order to define Schistosoma mansoni antigens able to function as modulator agents in BALB/c mice granulomatous hypersensitivity to parasite egg. The antigens P-24, P-35 and P-97 were purified by affinity chromatography from a fraction of S. mansoni adult worm antigenic preparation, denominated PIII, involved in the inhibition of granulomatous response to eggs. Immunization of mice with these antigens, in the presence of Corynebacterium parvum and Al(OH)3 as adjuvant, induced a significant protection degree against challenge infection, as observed by the decrease on worm burden recovered from portal system. In vitro blastogenesis assays revealed that purified antigens were able to induce significant proliferation of spleen cells from S. mansoni-infected mice. This protection was correlated to significant decrease in granuloma size induced by PIII. From these results, we concluded that PIII preparation contains antigens capable of mediating protective anti-parasite immunity and down-regulating granulomatous hypersensitivity to S. mansoni eggs.

Susceptibility of Nectomys rattus (Pelzen, 1883) to experimental infection with Schistosoma mansoni (Sambon, 1907): a potential reservoir in Brazil

The aim of the present research was to evaluate the potential of Nectomys rattus, the "water rat", to develop Schistosoma mansoni infection. Comparison with N. squamipes was carried out. Both species of rodents were submitted to transcutaneous infection using different infective cercariae loads: 50, 100 or 500. N. rattus showed high susceptibility to S. mansoni, with an infection rate of 71%. Rodents were able to excrete viable eggs of S. mansoni in the feaces during all infection period. For both species, the small intestine, followed by the liver and the large intestine, presented the highest concentration of eggs among the surveyed organs. Infection caused no animal death. Moreover, N. rattus accomplished the parasite's life cycle, by infecting the snails Biomphalaria glabrata and later Mus musculus. These evidences indicate that both N. rattus, as for N. squamipes are potential reservoirs for schistosomiasis in Brazil. Considering the fact that N. rattus and N. squamipes exist in the same natural ecosystems of S. mansoni, we suggest that these rodents must be regarded as influential factors in epidemiology surveys.

Resolution of an Infection with Leishmania braziliensis Confers Complete Protection to a Subsequent Challenge with Leishmania major in BALB/c Mice

Both Leishmania major and L. braziliensis induce cutaneous leishmaniasis in BALB/c mice. Whereas BALB/c mice die of infection with L. major, they cure an infection with L. braziliensis. We report here that after curing an infection with L. braziliensis, BALB/c mice are resistant to challenge with L. major. When challenged with L. major, L. braziliensis pre-treated BALB/c mice mounted a delayed-type hypersensitivity response to L. major and produced high amounts of interferon-g (IFN-g ) but low amounts of interleukin-4. The IFN-g produced by the L. braziliensis pre-infected mice was involved in the protection seen against L. major challenge since treating the mice with a neutralizing anti-IFN-g abrogated the protection. This suggests that cross-reactive antigen epitopes exist between L. braziliensis and L. major and that pre-infection with L. braziliensis primes BALB/c mice to epitopes on L. major that can elicit a protective Th1 response to the parasite.

Serodiagnosis of Trypanosoma cruzi Infection Using the New Particle Gel Immunoassay - ID-PaGIA Chagas

The ID-Chagas test is a particle gel immunoassay (PaGIA). Red coloured particles are sensitised with three different synthetic peptides representing antigen sequences of Trypanosoma cruzi: Ag2, TcD and TcE. When these particles are mixed with serum containing specific antibodies, they agglutinate. The reaction mixture is centrifuged through a gel filtration matrix allowing free agglutinated particles to remain trapped on the top or distributed within the gel. The result can be read visually. In order to investigate the ability of the ID-PaGIA to discriminate negative and positive sera, 111 negative and 119 positive, collected in four different Brazilian institutions, were tested by each of the participants. All sera were previously classified as positive or negative according to results obtained with three conventional tests (indirect immunofluorescence, indirect hemaglutination, and enzime linked immunosorbent assay). Sensitivity rates of ID-PaGIA varied from 95.7% to 97.4% with mean sensitivity of 96.8% and specificity rates varied from 93.8 to 98.8% with mean specificity of 94.6%. The overall Kappa test was 0.94. The assay presents as advantages the simplicity of operation and the reaction time of 20 min. In this study, ID-PaGIA showed to be highly sensitive and specific.