Aspects of the Maintenance of the Life Cycle of Fasciola hepatica in Lymnaea columella in Minas Gerais, Brazil

Fascioliasis is a parasitic disease of domestic ruminants that occurs worldwide. The lymnaeid intermediate hosts of Fasciola hepatica include Lymnaea columella, which is widely distributed in Brazil. A colony of L. columella from Belo Horizonte, MG, was reared in our laboratory to be used in studies of the F. hepatica life cycle, the intermediate host-parasite relationship and development of an anti-helminthic vaccine. In the first experiment 1,180 snails were exposed to miracidia of F. hepatica eggs removed from the biliary tracts of cattle from the State of Rio Grande do Sul. In the second and third experiments the snails were exposed to miracidia that had emerged from F. hepatica eggs from Uruguay, maintained in rabbits. The rates of infection in the first, second and third experiments were 0, 42.1 and 0 percent respectively. Over 15,806 metacercariae were obtained and stored at 4ºC. Four rabbits weighing 1.5 kg each were infected with 32-44 metacercariae and two with 200. Three rabbits begin to eliminate eggs of the parasite in the feces from 84 days after infection onwards. The biological cycle of F. hepatica in L. columella and the rabbit was completed within 124 days

Possible competitive displacement of planorbids by Melanoides tuberculata in Minas Gerais, Brazil

Several species of snails, including Pomacea haustrum, Marisa cornuarietis and Helisoma duryi, have been identified as probable competitors and/or predators of planorbid intermediate hosts of Schistosoma. During the last few years, studies carried out in the Caribbean region have shown reductions and even disappearances of populations of Biomphalaria glabrata and B. straminea in breeding places where the snail Melanoides tuberculata was introduced. Observations made over a period of 10 years in two lakes close to Belo Horizonte, MG, showed that there were marked reductions in autochthonous populations of B. glabrata and B. straminea after the arrival of M. tuberculata, both Biomphalaria species disappearing completely after eight years

Geographical distribution of Biomphalaria snails in the State of Minas Gerais, Brazil

Published and unpublished observations on geographical distribution of Biomphalaria snails in the State of Minas Gerais, Brazil, were compiled. This work is aimed at knowing the present occurrence of Biomphalaria species in this region, and at contributing to the elaboration of the planorbid chart of Minas Gerais. In malacological surveys, performed by several researchers, the presence of seven species of this genus was recorded. Those planorbids were found in 12 mesoregions, in 283 (33.1 percent) municipalities out of 853 with the following distribution: B. glabrata (185 municipalities), B. straminea (125), B. tenagophila (58), B. peregrina (57), B. schrammi (26), B. intermedia (20) and B. occidentalis (2). B. glabrata and B. tenagophila are found naturally infected by Schistosoma mansoni in Minas Gerais. In 24 municipalities the three snail hosts of S. mansoni in Brazil, B. glabrata, B. tenagophila and B. straminea, are present

Resistance of Biomphalaria occidentalis from Varzea das Flores dam, Minas Gerais, to Schistosoma mansoni infection detected by low stringency polymerase chain reaction

Biomphalaria occidentalis Paraense, 1981 from Varzea das Flores dam, MG, Brazil, was exposed to infection with Schistosoma mansoni. Individual infection was performed with 140 B. occidentalis and 100 B. glabrata snails using LE and SJ strains. Two groups of B. occidentalis were killed after seven day-miracidia exposure to detect S. mansoni DNA, through the low stringency polymerase chain reaction (LS-PCR), and were negative. The infection rates were 69.2 percent (LE strain) and 96.7 percent (SJ strain) for B. glabrata and 0 percent for B. occidentalis. LS-PCR enabled early resistance diagnosis

Susceptibility of Biomphalaria tenagophila and Biomphalaria straminea to Schistosoma mansoni infection detected by low stringency polymerase chain reaction

In order to determine Schistosoma mansoni infection rates in Biomphalaria tenagophila and B. straminea, low stringency polymerase chain reaction (LS-PCR) technique was used as a complementary method to light exposure technique. LS-PCR has already been standardized in our laboratory to detect the trematode DNA in B. glabrata. Higher S. mansoni infection rates were detected using conventional method and LS-PCR. The parasite DNA profile was detected in both species after 7-day exposure to miracidia, using LS-PCR. This technique enables early detection of schistosomiasis transmission focuses, in endemic areas, before the beginning of cercariae shedding

Rearing of Lymnaea columella (Say, 1817), intermediate host of Fasciola hepatica (Linnaeus, 1758)

The intermediate host of Fasciola hepatica, Lymnaea columella, collected in Belo Horizonte, Minas Gerais, Brazil, was reared in our laboratory. The aim of the current study was to standardize a rearing and maintenance technique. Two kinds of diet were tested: fresh lettuce (A) and rodent ration + 10 percent CaCO3 plus fresh lettuce (B). The age for the beginning of oviposition ranged from 27 to 57 days. Ten days after oviposition at 24.7§C, 100 percent eclosion occurred. The complete life cycle varied from 37 to 67 days. The average numbers of eggs per egg mass were 26.3 and 31.1 with diets (A) and (B), respectively. The lettuce and ration fed snails presented a increased growth although the difference was not statistically significant (p > 0.05). The mortality rate varied from 40 to 64 percent after 90 days. The maximum longevity was 183 days, 21.5 mm length and 11 mm wide. The methodology to mass breed and maintain these snails was found to be suitable in the laboratory.

Investigaçäo sobre a transmissäo da esquistossomose no complexo turístico da Serra do Cipó, MG / Investigation on transmission of schitosomiasis in the touristc complex of Serra do Cipó, MG, Brazil

Procede a levantamento malacológico, inquérito parasitológico e análise de água do Complexo Turístico da Serra do Cipó, MG, Brasil, objetivando detectar focos de transmissäo da esquistossomose e avaliar as condiçöes de balneabilidade das coleçöes hídricas. De fevereiro de 1997 a agosto de 1998, foram coletados 215 moluscos do gênero Drepanotrema lucidium (Pfeiffer, 1839), em 15 dentre 391 estaçöes pesquisadas nos municípios de Santana do Riacho e Jaboticatubas. As taxas de prevalência de esquistossomose nos moradores de Santana do Riacho de Jaboticatubas, foram de 3,9 por cento e 6,5 por cento, respectivamente. Dos 35 indivíduos infectados, 88,5 por cento relataram contato prévio com água em outras localidades endêmicas e foram tratados com oxamniquina. Camundongos sentinelas imersos em dois pontos do rio Cipó näo apresentaram vermes de Schistosoma mansoni no fígado e intestino após 50 dias. As condiçöes de balneabilidade das águas dos rios Cipó e Soberbo foram consideradas satisfatórias assim como as qualidades físico-químicas das mesmas. Nesse período, näo houve transmissäo de esquistossomose na regiäo graças à ausência de moluscos do gênero Biomphalaria, hospedeiros de S. mansoni, parasitados nas coleçöes hídricas. Medidas profiláticas foram recomendadas às autoridades em saúde para a manutençäo de condiçöes epidemiológicas satisfatórias no complexo

Molecular characterisation of intermediate snail hosts and the search for resistence genes

The relationship between schistosomes and their intermediate hosts is an extremely intricate one with strains and species of the parasite depending on particular species of snail, which in turn may vary in their susceptibility to the parasites. In order to gain a better understanding of the epidemiology of the disease we have been investigating the use of molecular markers for snail identification and for studying host-parasite relationships. In this paper we will draw on examples concerning schistosomiasis in West and East Africa to illustrate how a molecular analysis can be used as part of a total evidence approach to characterisation of Bulinus species and provide insights into parasite transmission. Particular emphasis is given to ribosomal RNA genes (rRNA), random amplified polymorphic DNA (RAPDs) and the mitochondrial gene cytochrome oxidase I (COI). Snails resistant to infection occur naturally and there is a genetic basis for this resistance. In Biomphalaria glabrata resistance to Schistosoma mansoni is known to be a polygenic trait and we have initiated a preliminary search for snail genomic regions linked to, or involved in, resistance by using a RAPD based approach in conjunction with progeny pooling methods. We are currently characterising a variety of STSs (sequence tagged sites) associated with resistance. These can be used for local linkage and interval mapping to define genomic regions associated with the resistance trait. The development of such markers into simple dot-blot or specif PCR-based assays may have a direct and practical application for the identification of resistant snails in natural populations.

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. Histopahology reflects these differences. In a state of tolerance numerous sporocysts in diffenrent stages of differentiation are seen in the absence of host tissue reaction. However, extensive diffuse and focal proliferation of amebocystes 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 months later failed to shed cercariae, exhibited focal and diffuse proliferation of amebocystes in many organs in the absence of parasitic 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 strutures 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) amebocystic 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.

Comparative histopathology of Biomphalaria glabrata, B. tenagophila and B. straminea with variable degrees of resistance to Schistosoma manzoni miracidia

A comparative histopathological study of three snails species - Biomphalaria glabata, B. tenagophila and B. straminea - which had been infected with Schistosoma mansoni miracidia reveled similar qualitative features, consisting of areas of sporocyst proliferation and differentiation associated with reactive host reaction, at the time they were actively eliminating great number of cercariae. However, in specimens that were exposed to miracidia but failed to eliminate cercariae later on, different histopathological pictures were observed in different snail species. While B. glabrata exhibited frequent focal (granulomatous) proliferation of amebocytes in several organs, B. tenagophila and B. straminea only rarely showed such reative changes, suggesting that the mechanism of resistance to miracidial infection probably follows different pathways in the snail species studied.

Levantamento malacológico em parques urbanos de Belo Horizonte, Minas Gerais, Brasil / A malacological survey in city parks in Belo Horizonte, Minas Gerais, Brazil

Existem atualmente na regiäo metropolitana de Belo Horizonte 18 parques urbanos (também denominados "parques ecológicos") com coleçöes hídricas (lagoas, nascentes, córregos etc). Pesquisas iniciais em 17 destes parques mostraram a ocorrência de moluscos hospedeiros intermediários do Schistosoma mansoni em pelo menos quatro deles. Capturas mensais nestes parques, de agosto/94 a fevereiro/96, mostraram os seguintes resultados em relaçäo aos planorbíneos: Parque Julien Rien: 1.145 exemplares de Biomphalaria glabrata (2 mm a 13 mm); Parque Betânia: 149 exemplares de B. glabrata (4 mm a 13 mm); Parque Santa Lúcia: 2.431 exemplares de B. straminea (3 mm a 9 mm) e Parque Lagoa do Nado: três exemplares de B. tenagophila (3 mm a 10 mm). As visitas aos parques teräo prosseguimento e, após um diagnóstico sobre a situaçäo de cada parque, seräo sugeridas às autoridades municipais medidas de controle e/ou erradicaçäo adequadas a cada área.

Esquistossomose: nova ocorrência de Biomphalaria straminea em Belo Horizonte, Minas Gerais / Schistosomiasis: new occurence of Biomphalaria straminea in Belo Horizonte, Minas Gerais

Em Belo Horizonte, Minas Gerais, Brasil, a Biomphalaria straminea é encontrada na regiäo da Pampulha. Recentemente, o molusco foi encontrado em valas da antiga Barragem de Santa Lúcia, foco extinto de esquistossomose transmitida por B.glabrata. Os moluscos foram coletados e examinados para verificar se estavam naturalmente infectados com Schistosoma mansoni. Os exemplares negativos foram usados para criaçäo ou infecçäo com a cepa LE de S. mansoni, mantida no laboratório, e outra cepa VGS, obtida de ovos de fezes de escolar de Belo Horizonte. Dentre 1.890 moluscos capturados em 1994 e 1995, nenhum estava infectado com S. mansoni. Dentre 87 exemplares coletados no criadouro e expostos à cepa LE, nove (10,3 por cento) eliminaram cercárias; dentre 83 moluscos da F1, dez (12 por cento) eliminaram cercárias e dentre 88 exemplares coletados e expostos à cepa VGS, dez (11,3 por cento) eliminaram cercárias. Em Belo Horizonte, a esquistossomose é transmitida por B. glabrata e B. tenagophila. Entretanto, atualmente existe o risco de aparecimento de novo foco, no qual a B. straminea poderá vir a ser a transmissora, se medidas profiláticas adequadas näo forem tomadas pelas autoridades responsáveis pela construçäo de um parque e lago no local.

Suscetibilidade aos agentes quimioterápicos de isolados de Schistosoma mansoni oriundos de pacientes tratados com oxamniquine e praziquantel e näo curados / Susceptibility to the chemotherapeutical compounds of Schistosoma mansoni from patients treated with oxamniquine and praziquantel and not cured ones

Ten inhabitants of Itaquara, Bahia, Brazil treated with oxamniquine and subsequently praziquantel were not cured. Schistosoma mansoni isolates derived from these patients were studied. Snails were infected with miracidia derived from the feces of these patients and the cercariae produced used to infect albino mice. The animals were then treated with a single oral dose of oxamniquine (25, 50 and 100mg/kg) or praziquantel (100, 200 and 400 mg/kg). The response to chemotherapy was significantly different in some of the isolates although it was not possible to characterize any of them as resistant. In addition, DNA analysis of the isolates by means of ®Random Amplified Polymorphic DNA® indicated a low degree of variability as compared with a laboratory strain, LE. Thus, it was not possible to characterize these organisms at a genetic level as a distinct strain.

Schistosoma mansoni: the sex ratios of worms in animals infected with cercariae from three species of Biomphalaria

A relacao de vermes machos e femeas de Schistosoma mansoni foi determinada em camundongos infecatos com cercarias das cepas LE, SJ e AL, eliminadas pelos moluscos hospedeiros do parasita no Brasil. Os numeros de vermes machos e femeas do Schistosoma mansoni foi determinada em camundongos infectados com cercarias das cepas LE, SJ e AL, eliminadas pelos moluscos hospedeiros do parasita no Brasil. Os numeros de vermes machos e femeas recuperados em inoculacoes de cercarias provenientes de Biomphalaria glabrata e B. tenagophila, foram semelhantes, variando de 1,1:1 a 1,6:1 com LE e AL e de 1:1,1 com SJ. Nos animais inoculados com cercarias provenientes de B. straminea a relacao de vermes macho e femea foi semelhante a obtida com cercarias provenientes das outras duas especies com a cepa LE, relacao de 1,5:1...

Schistosoma mansoni: níveis de infecciosidade para os moluscos hospedeiros intermediários do Brasil / Schistosoma mansoni: infectivity levels for intermediate snail hosts of Brazil

The levels of infectivity of Schistosoma mansoni for the three species of Biomphalaria, intermediate hosts of parasite in Brazil were studied after exposing of molluscs to miracidia in the laboratory and in the field. The LE and SJ strains of S. mansoni, maintained in laboratory were used in these experiments as well as the WVS and RFS strains obtained from faeces of schoolchildren from Belo Horizonte, MG. The results show the high level of infectivity of S. mansoni for B. glabrata with infection rates varying from 4.7 to 85.5 per cent. The snail B. straminea was susceptible to LE, SJ and WVS strains, with infection rates of 11.0 to 24.6 per cent, B. tenagophila was susceptible only to LE and SJ strains with infection rates of 2.5 to 6.5 per cent. The mean number of cercariae of the WVS strain shed per day, by B. straminea and B. glabrata were 93 +/- 59 and 782 +/- 1,120, respectively.

Influence of temperature on development of Schistosoma mansoni female cercariae in Biomphalaria glabrata

Nestes experimentos a relacao de larvas de Schistosoma mansoni, macho e femea, em Biomphalaria glabrata de Belo Horizonte e de Ribeirao das Neves, MG, Brasil, criada no laboratorio ou capturada no campo variou de 1:1 a 1:1,3 ou 1,4:1...

Development of Schistosoma mansoni em Biomphalaria tenagophila, Biomphalaria straminea and Biomphalaria glabrata

Foi feito estudo comparativo do desenvolvimento do Schistosoma mansoni na fase intra-molusco, atraves de cortes histologicos, em Biomphalaria tenagophila, B. straminea e B. glabrata. Duzentos moluscos de cada especie foram expostos individualmente a 50 miracidios de S. mansoni da linhagem AL. Nenhuma larva foi observada nos exemplares fixados 72 horas apos a exposicao...

Molluscicide control of snail vectors of schistosomiasis

A review of the methodology recommended by the World Health Organization for the use of molluscicides for the control of snail vectors of schistosomiasis is presented. Discussion of the principle molluscicides used, their advantages and disadvantages, the techniques and equipment required for their application and evaluation of effect as well as the biological control of snails is included.

Degree of host-parasite compatibility between Schistosoma mansoni and their intermediate molluscan hosts in Brazil

The compatibility of Biomphalaria tenagophila, B. straminea and B. glabrata from Minas Gerais with different strains of Schistosoma mansoni was evaluated using the method of Frandsen (1979b) in standardized experiments. One hundred and fifty of each species of snail were individually exposed in the laboratory to 50 miracidia of S. mansoni lines LE, SJ and AL. The cercariae from the infected snails were counted and used to calculate TCP/100 indices, which were compared with those of Frandsen (1979b). For B. tenagophila the TCP/100 indices varied from 37,996 to 74,266 (class II and III). The snail was poorly compatible with LE (class II) and compatible with SJ and AL (class III). For B. straminea the indices varied from 9,484 to 20,508. The snail was not very compatible with SJ (class I) and poorly compatible with LE and AL (class II). For B. glabrata the indices varied from 588,828 to 1,039,065. The snails was extremely compatible (class VI) with the three lines of S. mansoni. These results confirm the epidemiological importance of B. glabrata in Brazil followed by B. tenagophila and B. straminea.