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.

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.

Ocorrência de Sarasinula marginata (Mollusca: Soleolifera) em Belo Horizonte, MG, Brasil / Occurrence of Sarasinula marginata (Mollusca: Soleolifera) in Belo Horizonte, MG, Brazil

The occurrence of Sarasinula marginata, a possible intermediate host of Angiostrongylus costaricensis, in the city of Belo Horizonte, MG, Brazil, is reported on

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.

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

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...

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.

Fatores que podem afetar a criaçäo e manutençäo de caramujos infectados e a produçäo de cercárias de Schistosoma masoni / Factors that can affect the breeding and maintenance of infected snails and yield of cercariae of Schistosoma mansoni

Foram estudados fatores que afetam a produçäo em massa de cercárias do Schistosoma mansoni. Rotíferos e ostracodos causaram diminuiçäo de produçäo em nossa colônia. Os rotíferos foram erradicados facilmente lavando-se os aquários e a alface com ácido acético diluído. Já o ostracodo foi de difícil erradicaçäo, produzindo mortalidade nos caramujos infectados, que alcançou níveis de 50-60% por mês. Moluscos infectados mantidos na incubadora a temperatura constante e em total escuridäo apresentaram maior eliminaçäo quando iluminados, a aproximadamente 30-C. A eliminaçäo de cercárias foi praticamente a mesma entre os pHs 5-7. Traços de metais pesados adicionados à água destilada afetaram negativamente a eliminaçäo. Finalmente, a manutençäo em incubadora, embora apresenta-se maior mortalidade de moluscos, foi mais simples e eficiente para a produçäo em massa de cercárias que o sistema convencional com água corrente

Resistência de Biomphalaria peregrina de Santa Rita do Sapucaí, Minas Gerais, a infecçäo com três cepas de Schistosoma mansoni / Resistance of Biomphalaria peregrina from Santa Rita do Sapucaí, State of Minas Gerais, Brazil, to infection with strain of Schistosoma mansoni

Descendentes do planorbídeo Biomphalaria peregrina, coletados em Santa Rita do Sapucaí, Minas Gerais, Brasil, foram expostos a miracídios de três cepas de Schistosoma mansoni: "LE" de Belo Horizonte, MG; "SJ" de Säo José dos Campos, SP e "AL" do Estado de Alagoas. Dentre 300 exemplares expostos, nenhum se infectou com as três cepas do trematódeo. Por outro lado, 300 exemplares de B. glabrata, dos grupos de controle, apresentaram taxas de infecçäo de 61,1 a 95,3% com as três cepas do trematódeo. As taxas de mortalidade de B. peregrina e de B. glabrata foram de 20,0 e de 28,0%, respectivamente

Primeiro encontro de biomphalaria tenagophila (D'Orbigny, 1835) naturalmente infectada, com schistosoma mansoni, em Itajubá, sul do Estado de Minas Gerais, Brasil / First finding of naturally infected Biomphalaria tenagophila (d'Orbigny, 1835) at Itajubá, South of Minas Gerais State, Brazil

Foi descrito o primeiro encontro de Biomphalaria tenagophila, naturalmente infectada, em Itajubá, no sul do Estado de Minas Gerais, Brasil. Nas coleçöes hídricas que cortam a Granja Wenceslau Neto foram coletados 1.501 exemplares de B. tenagophila, dos quais dois (0,14%) eliminavam cercárias de S. mansoni. Estes dados indicaram que a transmissäo da esquistossomose mansoni continua sendo possível nessa cidade, localizando-se, hoje, em Itajubá, o primeiro foco de endemia no sul do Estado de Minas Gerais

Sarasinula marginata (Semper, 1885) (Mollusca, Soleolifera) de Belo Horizonte (MG, Brasil) como hospedeira intermediária potencial do Angiostrongylus costaricencis Morera & Céspedes, 1971 / Sarasinula marginata (Semper, 1885) (Mollusca, Soleolifera) from Belo Horizonte (MG, Brasil) as a potential intermediate host of Angiostrongylus costaricensis Morera, Cespedes, 1971

Specimens of Sarasinula marginata were collected in kitchen and house gardens of Belo Horizonte, Minas Gerais. The susceptibility of these molluscs for Angiostrongylus costaricensis was tested by infecting 15 laboratory--reared slugs (F1). The positivity demonstrated was of 80.0.

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.

Production of Schistosoma mansoni cercariae by Biomphalaria glabrata from a focus in Belo Horizonte, Minas Gerais

A densidade planorbidica, as taxas de infeccao e a producao mensal de cercarias de Schistosoma mansoni por Biomphalaria glabrata, foram determinadas em foco do Barreiro de Baixo (Belo Horizonte MG, Brasil). Durante 38 meses, de 1984 a 1987, foram capturados 5.366 moluscos dentre os quais 324 (6,0 por cento) estavam infectados com o S. mansoni. O total de cercarias eliminadas foi de 5.667.312. Cada molusco eliminou em media 17.422 cercarias durante sua permanencia no laboratorio. A maior longe vidade dos moluscos infectados foi de 218 dias. Foi observada a cura natural de 42 (12,9 por cento)dos exemplares infectados, apos cerca de 130 dias de captura. A densidade planorbidica media, no foco durante esse periodo fo de 16,3 moluscos por conchada. A eliminacao de cercarias pelos moluscos do campo foi comparada com a de exemplares criados no laboratorio, infectados em massa com a linhagem LE de S. mansoni de Belo Horizonte. Os moluscos do laboratorio eliminaram em media 6.061 cercarias por exemplar, numero 2,8 vezes menor do que os moluscos do campo, devido a longevidade menor. A taxa de prevalencia da esquistossomose no foco foi de 14,3 por cento.

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.

Resistência de Biomphalaria Schrammi de arcos, Minas Gerais, Brasil, à infecçäo com duas cepas de schistosoma mansoni / Resistence of Biomphalaria schrami of Arcos, Minas Gerais, Brazil, to infection with 2 strains of schistosomo mansoni

Descendentes do plonorbídeo Biomphalaria schrammi Crosse, 1864, coletados na localidade de Calcioländia, município de Arcos, Minas Gerais, Brasil foram expostos a miracídios de duas cepas de Schistosoma mansoni:"LE" de Belo Horizonte, Minas Gerais e "SJ" de Säo José dos Campos, Säo Paulo, Brasil. Dentre 172 exemplares expostos, nenhum se infectou com as duas cepas deste trematôdeo. Por outro lado, 100 exemplares de Biomphalaria glabrata, dos grupos controle, apresentaram taxas de infecçäo de 88 e 40% com as cepas "LE" e "SJ", respectivamente. A taxa de mortalidade de B. schrammi chegou a 44% enquanto a de B. glabara näo atingiu 10%

Atividade moluscicida de alguns produtos naturais sobre Biomphalaria glabrata / Molluscicide activity of some natural products on Biomphalaria glabrata

Foi avaliada, em laboratório, a açäo moluscicida de extratos aquosos (macerado e fervido), hexânico e etanólico de Aristolochia brasiliensis, Caesalpinia peltophoroides, Caesalpinia pulcherrima, Delonix regia, Spathodea campanulata e Tibouchina scrobiculata. As soluçöes dos extratos obtidos foram testadas sobre caramujos adultos e desovas de Biomphalaria glabrata, criados em laboratório, nas concentraçöes de 1, 10, 20, 200 e 1000ppm. Dos extratos testado o mais ativo foi o etanólico das flores da D. regia (flamboyant) que apresentou atividade moluscicida sobre caramujos adultos na concentraçäo de 20ppm

Potencialidade de Biomphalaria tenagophila do lago Pampulha, Belo Horizonte, MG, como hospederia do Schistosoma mansoni / Potentiality of Biomphalaria tenagophila from Pampulha lake, Belo Horizonte, MG, as a host of Schistosoma mansoni

Caramujos Biomphalaria tenagophila descendentes de exemplares coletados no lago da Pampulha, Belo Horizonte, Minas Gerais, foram expostos a miracídios de quatro cepas de Schistosoma mansoni: LE e HK de origem local, Belo Horizonte, AL do Estado de Alagoas e SJ, de Säo José dos Campos, SP. As cepas LE, AL e SJ säo mantidas em laboratório e HK foi obtida de fezes de paciente que reside próximo à Pampulha. As taxas de infecçäo experimental foram de 4% (LE), 6% (HK), 30% (SJ) e 40% (AL). Esses indícios de infecçäo foram semelhantes aos obtidos por vários autores para populaçöes de B. tenagophila de Minas Gerais. Caramujos infectados experimentalmente eliminaram número de cercárias comparável ao de B. glabrata do controle e de B. tenagophila capturada no lago, com infecçäo natural (cerca de 2.000 cercárias/molusco). Devido à alta densidade planorbídica atual em alguns pontos do lago, número de cercárias eliminadas por exemplares naturalmente infectados, afluxo de pessoas para pesca e lazer, contaminaçäo das águas por dejetos humanos, os autores alertam para o risco de crescimento do foco de esquistossomose no local

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...