Abstract
Introduction
Human migration and the presence of natural vectors (mollusks) of Schistosoma mansoni are the primary causes of the expansion of mansoni schistosomiasis into southern areas of South America. Water conditions are favorable for the expansion of this disease because of the extensive hydrographic network, which includes the basins of the Paraná and Uruguay rivers and favors mollusk reproduction. These rivers also aid agriculture and tourism in the area. Despite these favorable conditions, natural infection by S. mansoni has not yet been reported in Argentina, Uruguay, or Paraguay.
Methods
Two species of planorbid from Argentina, Biomphalaria straminea and B. tenagophila, were exposed to the miracidia of five Brazilian strains of S. mansoni.
Results
Biomphalaria tenagophila (Atalaya, Buenos Aires province) was infected with the SJS strain (infection rate 3.3%), confirming the experimental susceptibility of this Argentinian species. Biomphalaria straminea (Rio Santa Lucía, Corrientes province) was susceptible to two Brazilian strains: SJS (infection rate 6.7%) and Sergipe (infection rate 6.7%).
Conclusions
These results demonstrate that species from Argentina have the potential to be natural hosts of S. mansoni and that the appearance of foci of mansoni schistosomiasis in Argentina is possible.
Schistosomiasis; Biomphalaria ; Susceptibility
INTRODUCTION
Mansoni schistosomiasis has expanded in recent decades, primarily because of the
migration of individuals who have been parasitized by Schistosoma
mansoni, live in inadequate sanitary conditions in peripheral areas of
large cities, and contaminate the water supply with their waste. These water
supplies contain trematode vectors such as freshwater mollusks, permitting the
establishment of disease foci. In recent decades in Brazil, the disease has spread
toward the southern states, with autochthonous cases of this parasitosis reported in
Paraná, Santa Catarina, and Rio Grande do Sul101 Bernardini OJ, Machado MM. Esquistossomose mansoni em Santa
Catarina: isolamento do Schistosoma mansoni primeiro foco de transmissão ativa
em São Francisco do Sul. Arq Cat Med 1981; 10:212.
02 Espíndola KS, Machado MM, Hofmann PR. Natural and experimental
infection of planorbids from the island of Santa Catarina (Brazil). Rev Inst Med
Trop São Paulo 1992; 34:289-294.
03 Carvalho OS, Nunes IM, Caldeira, RL. First report of Biomphalaria
glabrata in the state of Rio Grande do Sul, Brazil. Mem Inst Oswaldo Cruz 1998;
93:39-40.-404 Graeff-Teixeira C, Anjos CB, Oliveira VC, Velloso CFP, Fonseca MBS,
Valar C, et al. Identification of a transmission focus of Schistosoma mansoni in
the southernmost brazilian state, Rio Grande do Sul. Mem Inst Oswaldo Cruz 1999;
94:9-10.. Ecosystem changes in
northeastern Argentina caused by the construction of dams have led to an increase in
infectious diseases due to an increase in temperature505 Gorodner J, Alonso JM, Zibelman O, Galván M, Merino D, Balbachan SE,
Miranda O. Impacto ambiental de modificações ecológicas realizadas em uma área
subtropical. Rev Soc Bras Med Trop 2004; 37:154-157.. Of the planorbid
vector species of S. mansoni found in the southernmost states of
Brazil (Rio Grande do Sul and Santa Catarina), Biomphalaria
tenagophila is the most common606 Teles HMS, Pareira PAC, Richinitti LMZ. Distribuição de Biomphalaria
(Gastropoda, Planorbidae) nos Estados do Rio Grande do Sul e Santa Catarina,
Brasil. Rev Saude Publica S Paulo 1991; 25:350-352.,707 Schlemper Jr BR, Ferreira Neto JA, Thiago PTS, Bressan C, Amarante
AR, Distribuição geográfica de planorbídeos em Santa Catarina, Brasil. Rev Soc
Bras Med Trop 1996; 29:411-418.. This species is
responsible for schistosomiasis foci in São Francisco do Sul, Santa Catarina. Among
the species described in Rio Grande do Sul (Brazil), the primary vector of
S. mansoni in the South American continent, B.
glabrata, is responsible for the occurrence of the disease in the
municipality of Esteio404 Graeff-Teixeira C, Anjos CB, Oliveira VC, Velloso CFP, Fonseca MBS,
Valar C, et al. Identification of a transmission focus of Schistosoma mansoni in
the southernmost brazilian state, Rio Grande do Sul. Mem Inst Oswaldo Cruz 1999;
94:9-10.. In Uruguay, Paraguay, and Argentina, numerous
planorbid breeders have been described in association with B.
tenagophila and B. straminea
808 Paraense WL. Estado atual da sistemática dos planorbídeos
brasileiros. Arq Mus Nac Rio de Janeiro 1975; 55:105-128.
09 Bonetto A, Bechara JA, Tassara M. Los moluscos de La família
Planorbidae en el área Del río Paraná Medio. Physis Sec B 1982;
41:1-6.
10 Rumi A, Hamann MI. Potential schistosome-vector snails and
associated trematodes in ricefields of Corrientes Province, Argentina.
Preliminary results. Mem Inst Oswaldo Cruz 1990; 85:321-328.
11 Borda CE, Rea MJF. Susceptibilidad de Biomphalaria tenagophila de
las cuencas de los ríos Paraná y Uruguay a Schistosoma mansoni. Rev Panam Salud
Publica 1997; 1:167-173.-1212 Borda CE, Rea MJF. Biomphalaria tenagophila potencial vector of
Schistosoma mansoni in the Paraná River basin (Argentina and Paraguay). Mem Inst
Oswaldo Cruz 2007; 102:191-195.
, which are known to be natural vectors of S. mansoni.
Breeding conditions are favorable for these mollusks in the flooded fields used for
plantations and in irrigation canals and reservoir dams. A study was conducted in
Argentina to investigate the growth of natural populations of Biomphalaria in the La
Plata river basin. A greater steady growth was confirmed for
B. tenagophila compared with B. peregrina
1313 Rumi A, Gregoric DEG, Roche A. Tendencias del crecimiento individual
en poblaciones naturales de Biomphalaria spp. (Gastropoda, Planorbidae) en La
cuenca del Plata, Argentina. Comun Soc Malacol Uruguay 2009;
9:185-193.
. Despite the existence of schistosomiasis foci in the Brazilian states
bordering Argentina, Uruguay, and Paraguay, there have been no reports of the
natural transmission of schistosomiasis in the basin of the La Plata river in these
countries1212 Borda CE, Rea MJF. Biomphalaria tenagophila potencial vector of
Schistosoma mansoni in the Paraná River basin (Argentina and Paraguay). Mem Inst
Oswaldo Cruz 2007; 102:191-195.,1414 Borda CE, Rea MJF. Susceptibility and compatibility of Biomphalaria
tenagophila from the Río de la Plata basin with Schistosoma mansoni from Brazil.
Mem Inst Oswaldo Cruz 2010; 105:496-498.. However, experimental studies with populations of
B. tenagophila from Argentina, Uruguay, and Paraguay have
demonstrated that this species is susceptible to the Brazilian strain of S. mansoni
1111 Borda CE, Rea MJF. Susceptibilidad de Biomphalaria tenagophila de
las cuencas de los ríos Paraná y Uruguay a Schistosoma mansoni. Rev Panam Salud
Publica 1997; 1:167-173.,1212 Borda CE, Rea MJF. Biomphalaria tenagophila potencial vector of
Schistosoma mansoni in the Paraná River basin (Argentina and Paraguay). Mem Inst
Oswaldo Cruz 2007; 102:191-195.,1414 Borda CE, Rea MJF. Susceptibility and compatibility of Biomphalaria
tenagophila from the Río de la Plata basin with Schistosoma mansoni from Brazil.
Mem Inst Oswaldo Cruz 2010; 105:496-498.
15 Borda CE, Pellegrino J, Susceptibilidad de Biomphalaria tenagophila
y B. glabrata a dos cepas de Schistosoma mansoni. Rev Inst Med Trop São Paulo
1976; 18:157-164.-1616 Borda CE, Rea MJF. Intermediate and definitive hosts of Schistosoma
mansoni in Corrientes province, Argentina. Mem Inst Oswaldo Cruz 2006;
101:233-234.
. Paraense & Corrêa1717 Paraense WL, Corrêa LR. A potential vector of Schistosoma mansoni in
Uruguay. Mem Inst Oswaldo Cruz 1989; 84:281-288. assessed the susceptibility of a
planorbid population from Uruguay that was morphologically similar
to B. straminea and confirmed an infection rate of 23% after
exposure to miracidia of the SJ strain of S. mansoni. The
susceptibility exhibited by the mollusks depends on the degree of physiological
adaptation between the parasite and its intermediary host, as suggested by
Magalhães1818 Magalhães LA. Estudo dos dados obtidos de uma população de
Biomphalaria glabrata de Belo Horizonte infectada por Schistosoma mansoni da
mesma cidade e de uma população de Biomphalaria tenagophila de Campinas
infectada por S. mansoni de São José dos Campos. Rev Soc Bras Med Trop 1969;
3:195-196., thus explaining the different infection rates observed
among populations of the same species of mollusk when infected with different
strains of the parasite. Physiological adjustment was also demonstrated by Paraense
& Corrêa,1919 Paraense WL, Corrêa LR. Variation in susceptibility of populations
of Australorbis glabratus to a strain of Schistosoma mansoni . Rev Inst Med Trop
São Paulo 1963; 5:15-22. who reported that S. mansoni that were
adapted to B. glabrata from Belo Horizonte (State of Minas Gerais
(MG), Brazil) resisted infection when challenged by B. tenagophila
from São José dos Campos (State of São Paulo (SP), Brazil) and vice versa. Paraense
& Corrêa1919 Paraense WL, Corrêa LR. Variation in susceptibility of populations
of Australorbis glabratus to a strain of Schistosoma mansoni . Rev Inst Med Trop
São Paulo 1963; 5:15-22. demonstrated the existence of two strains of the trematode
in Brazil: one from Belo Horizonte (BH) that uses B. glabrata as an
intermediary host and one from São José dos Campos (SJ) that uses sympatric
B. tenagophila as an intermediary host.
The great rivers that form the La Plata river basin are the most likely dispersion routes of schistosomiasis toward Argentina, Paraguay, and Uruguay. In the Mesopotamia region of Argentina in which these rivers are located, numerous B. tenagophila and B. straminea breeders are known vectors of S. mansoni. Biomphalaria peregrina, a mollusk that has not yet been found to be naturally infected by the trematode but has high infection rates in the laboratory, is also present in this region. The aim of the present study was to perform susceptibility tests on the planorbid mollusks B. tenagophila and B. straminea from Argentina after exposure to a number of Brazilian strains of S. mansoni. Studies of the association between mollusks and S. mansoni have epidemiological significance because they facilitate the prediction of areas that become endemic regions for schistosomiasis.
METHODS
The specimens of B. straminea and B. tenagophila used in the present study were isolated in the laboratory from specimens collected in Argentina from the Santa Lucía River, in the province of Corrientes, and in Atalaya on the La Plata river, in the province of Buenos Aires, respectively. These specimens were provided by Dr. Alejandra Rumi. Five strains of S. mansoni were used for the susceptibility tests: the BH strain (Belo Horizonte, MG, Brazil), which was maintained in sympatric B. glabrata; the SJ strain (São José dos Campos, SP, Brazil), which was maintained in sympatric B. tenagophila; the SJS strain (São José dos Campos, SP, Brazil), which was genetically selected for susceptibility and maintained in sympatric B. tenagophila that were genetically selected for susceptibility to S. mansoni 2020 Zanotti-Magalhães EM, Magalhães LA, Carvalho JF. Relação entre a patogenicidade de Schistosoma mansoni em camundongos e a susceptibilidade do molusco vetor. I. Infecciosidade das cercarias e carga de vermes. Rev Saude Publica S Paulo 1991; 25:359-366. ; the BA strain (Bahia, Brazil), which was isolated from the feces of a tourist from Barra Grande, Bahia, Brazil, and maintained in B. glabrata from Minas Gerais (MG, Brazil); and the SE strain (Sergipe (SE), Brazil), which was isolated from B. glabrata from Ilha das Flores (SE, Brazil) and maintained in sympatric B. glabrata. Five groups of B. tenagophila (5-7mm) and B. straminea (2-3mm), each containing 30 specimens, were individually exposed to 10 miracidia of each of the specified strains of S. mansoni. The miracidia were obtained from eggs retrieved from the feces of Swiss mice (Mus musculus) that were experimentally infected with the respective strains of Schistosoma mansoni. After exposure, the groups of mollusks were kept in aquariums containing dechlorinated water at room temperature (±25°C) and fed lettuce ad libitum. The water was changed periodically, and from the fourth to the 16th week after exposure to the miracidia, the mollusks were examined to confirm the liberation of cercariae. The aquariums were maintained under artificial light at 28°C. At the end of the experiment, the surviving mollusks were compressed between two glass plates and examined under a stereoscopic microscope to confirm the presence of sporocysts in the tissue. Statistical analysis of survival was performed by comparing the 10 survival curves obtained from the combinations of species of mollusk (B. tenagophila and B. straminea) and trematode strain (BH, SJ, BA, SE, and SJS). Alternative analysis was also performed to investigate the species effect and the strain effect on survival. The survival curves were adjusted using the Kaplan-Meier method and compared with log-rank statistics, for which the significance probability allowed an assessment of the differences between the curves.
RESULTS
Table 1 displays the number of mollusks that were infected and the mortality rate. Figure 1 and Figure 2 display the infectivity of mollusks from the fourth week of infection to the end of the experiment. Only four of the specimens of B. straminea that were exposed to infection exhibited elimination of cercariae: two that were exposed to the SJS strain and two that were exposed to the SE strain. The prepatent period was six weeks for the SJS strain and eight weeks for the SE strain. The specimens of B. straminea that were exposed to the SE strain and eliminated cercariae died between the eighth and ninth weeks of infection. The specimens of B. straminea that were exposed to the SJS strain and eliminated cercariae died between the eighth and ninth weeks of infection: one survived for one week and the other for two weeks. Only one of the specimens of B. tenagophila that were exposed to infection eliminated cercariae: the SJS strain of S. mansoni. The prepatent period was seven weeks, and this mollusk died between the seventh and eighth weeks of infection.
- Prepatent period and infectivity of Biomphalaria tenagophila from Argentina after exposure to five different strains of Schistosoma mansoni. BH: Belo Horizonte; SJ: São José dos Campos; SJS: São José dos Campos, genetically selected.
- Prepatent period and infectivity of Biomphalaria straminea from Argentina after exposure to five different strains of Schistosoma mansoni. BH: Belo Horizonte; SJ: São José dos Campos; SJS: São José dos Campos, genetically selected.
Analysis of the survival curves ( Figure 3, Figure 4A, and Figure 4B), which were softened by the Weibull distribution, revealed a highly significant difference between the curves (p<0.0001). The shortest survival times were associated with the SE strain (Sergipe). No significant difference (p=0.32580) was observed for the effect of the mollusk species ( Figure 4A). A significant difference (p<0.0001) was observed for the effect of the strain ( Figure 4B), which disappeared (p=0.7018) when the SE strain was removed from the data set (Sergipe).
- Survival curves adjusted for the Weibull distribution with respect to the experimental groups. B: Biomphalaria; BH: Belo Horizonte; SJS: São José dos Campos; SJS: São José dos Campos, genetically selected.
- Survival curves adjusted for the Weibull distribution with respect to the two species of mollusks, B. straminea and B. tenagophila (A), and the strains of Schistosoma mansoni used in the experiments, BA, BH, SE, SJ, and SJS (B). B: Biomphalaria; BH: Belo Horizonte; SJS: São José dos Campos, genetically selected; BA: Bahia, SE: Sergipe; SJ: São José dos Campos.
DISCUSSION
The susceptibility of mollusks that are vectors of S. mansoni is
controlled genetically and is heritable over generations2121 Newton WL. The inheritance of susceptibility to infection with
Schistosoma mansoni in Australorbis glabratus. Exp Parasitol 1953;
2:242-257.
22 Richards CS. Genetic of a molluscan vector of schistosomiasis.
Nature 1970; 227:806-810.-2323 Santana JV, Magalhães LA, Rangel HA. Seleção de linhagens de
Biomphalaria glabrata e B. tenagophila visando maior susceptibilidade ao
Schistosoma mansoni. Rev Saúde Pública São Paulo, 1978;
12:67-77.. The
different degrees of susceptibility exhibited by the vectors of the trematode are
the result of the frequency of the phenotypes of the parasite that are pre-adapted
to the population of mollusks. The results of the present study demonstrated that,
of the five strains of S. mansoni used, only the SJS and SE strains
were able to develop in populations of Argentinean mollusks. The SJS strain
originated from a population of B. tenagophila that is sympatric to
the SJ strain1919 Paraense WL, Corrêa LR. Variation in susceptibility of populations
of Australorbis glabratus to a strain of Schistosoma mansoni . Rev Inst Med Trop
São Paulo 1963; 5:15-22., which was genetically selected for its
susceptibility2020 Zanotti-Magalhães EM, Magalhães LA, Carvalho JF. Relação entre a
patogenicidade de Schistosoma mansoni em camundongos e a susceptibilidade do
molusco vetor. I. Infecciosidade das cercarias e carga de vermes. Rev Saude
Publica S Paulo 1991; 25:359-366.. Although B. glabrata from Belo
Horizonte was resistant to infection by the SJ strain, this species of mollusk was
susceptible to infection by the SJS strain2424 Zanotti-Magalhães EM, Magalhães LA, Carvalho JF. Relação entre a
patogenicidade do Schistosoma mansoni em camundongos e a susceptibilidade do
molusco vetor. IV. Infecciosidade dos miracídios. Rev Saúde Pública Sao Paulo
1997; 31:488-494.. In the present study,
B. tenagophila and B. straminea from Argentina
released cercariae after exposure to miracidia of the SJS strain of S.
mansoni. Among the five Brazilian strains of S.
mansoni used in the susceptibility tests, B.
tenagophila specimens from the province of Buenos Aires (Argentina)
were susceptible only to the SJS strain, with liberation of cercariae and an
infection rate of 3.3% (Table 1). This
result demonstrates that B. tenagophila is only susceptible to
parasites that originate in mollusks of the same species, corroborating the results
of Borda & Rea1212 Borda CE, Rea MJF. Biomphalaria tenagophila potencial vector of
Schistosoma mansoni in the Paraná River basin (Argentina and Paraguay). Mem Inst
Oswaldo Cruz 2007; 102:191-195.,1414 Borda CE, Rea MJF. Susceptibility and compatibility of Biomphalaria
tenagophila from the Río de la Plata basin with Schistosoma mansoni from Brazil.
Mem Inst Oswaldo Cruz 2010; 105:496-498.,1616 Borda CE, Rea MJF. Intermediate and definitive hosts of Schistosoma
mansoni in Corrientes province, Argentina. Mem Inst Oswaldo Cruz 2006;
101:233-234., who found that liberation of cercariae only
occurred in B. tenagophila from Corrientes (Argentina) after
exposure to the SJ strain of S. mansoni. The infection rate
confirmed by the authors was between 2% and 22%1414 Borda CE, Rea MJF. Susceptibility and compatibility of Biomphalaria
tenagophila from the Río de la Plata basin with Schistosoma mansoni from Brazil.
Mem Inst Oswaldo Cruz 2010; 105:496-498., with a prepatent
period of 31 to 54 days. In the present study, the prepatent period was seven weeks.
The longer prepatent periods and lower infection rates indicate that the development
of the trematode was hampered in the mollusk. However, subsequent generations of
B. tenagophila were more susceptible to S.
mansoni, as reported by Borda & Rea1414 Borda CE, Rea MJF. Susceptibility and compatibility of Biomphalaria
tenagophila from the Río de la Plata basin with Schistosoma mansoni from Brazil.
Mem Inst Oswaldo Cruz 2010; 105:496-498., who found a
higher infection rate in the F1 generation of B. tenagophila.
Susceptibility is easier to obtain than an increase in resistance2525 Zuim NRB, Zanotti-Magalhães EM, Magalhães LA, Linhares AX. Seleção
genética de Biomphalaria glabrata e Biomphalaria tenagophila visando a alteração
da suscetibilidade e resistência ao Schistosoma mansoni. Rev Soc Bras Med Trop
2005; 38:387-390..
Bernadini & Machado101 Bernardini OJ, Machado MM. Esquistossomose mansoni em Santa
Catarina: isolamento do Schistosoma mansoni primeiro foco de transmissão ativa
em São Francisco do Sul. Arq Cat Med 1981; 10:212. confirmed that B. tenagophila
was the vector species in schistosomiasis foci in Santa Catarina (Brazil). Along the
coast of Rio Grande do Sul (Brazil), the population of B.
tenagophila in the Taim Ecological Station has been shown to be
resistant to infection by S. mansoni
2626 Coelho PMZ, Carvalho OS, Andrade ZA, Martins-Sousa RL, Rosa FM,
Barbosa L, et al. Biomphalaria tenagophila/Schistosoma mansoni interaction:
premises for a new approach to biological control of schistosomiasis. Mem Inst
Oswaldo Cruz 2004; 99:109-111.
. These Brazilian states share a border with the Argentinean province of
Corrientes. Paraense2727 Paraense WL, Biomphalaria tenagophila guaibensis ssp.n. from
Southern Brazil and Uruguay (Pulmonata:Planorbidae). I. Morphology. Mem Inst
Oswaldo Cruz 1984; 79:465-469. reported morphological differences in the penile
complex of planorbids in Rio Grande do Sul (Brazil) and Uruguay, suggesting the
existence of a subspecies called B. tenagophila guaibensis, which
had previously2828 Paraense WL, Corrêa LR. Probable extension of schistosomiasis
mansoni to southernmost Brazil. Mem Inst Oswaldo Cruz 1987;
82:577. been shown to be resistant to infection by the BH and SJ
strains of S. mansoni. However, specimens of B.
tenagophila tenagophila from Tramandaí (on the northern coast of the
same state) exhibited an infection rate of 2.08% after exposure to SJ miracidia.
Biomphalaria straminea specimens from the province of Corrientes (Argentina) were infected by the SJS and SE strains (Table 1), an unprecedented result for this species from Argentina. Paraense & Corrêa1717 Paraense WL, Corrêa LR. A potential vector of Schistosoma mansoni in Uruguay. Mem Inst Oswaldo Cruz 1989; 84:281-288. observed a morphologically similar species infection of B. straminea from Uruguay after exposure to the SJ strain. Biomphalaria straminea specimens from Argentina were notably susceptible to the Sergipe strain (SE), which was isolated from naturally infected B. glabrata. Infection by this strain, which has a high degree of endemicity for schistosomiasis, caused a higher mortality rate in the mollusks ( Figure 3, Figure 4A and Figure 4B). This increased mortality was attributed to the parasite; the larval stages of the trematode compromise the tissues and organs of mollusks infected with S. mansoni 2929 Coelho MV. O parasito -Schistosoma mansoni. In: Cunha AL, editor. Esquistossomose mansoni, São Paulo: USP Edition; 1970, p. 1-12. . The prepatent period ranged from six to eight weeks, indicating restricted S. mansoni development, although one of the specimens survived for two weeks. Figueiredo3030 Figueiredo CCSB. Dispersão de Biomphalaria straminea no estado de Sergipe: um estudo comparativo com dezenove anos de intervalo. Mem Inst Oswaldo Cruz 1989; 84:383-387. observed a natural infection rate of 2.5% for B. straminea from Laranjeiras, Sergipe (Brazil), which the author considered to be relatively high. This species is a significant transmitter of S. mansoni in this Brazilian state. The SE strain used in the present study was obtained from naturally infected B. glabrata and collected from Ilha das Flores in Sergipe (SE), Brazil. The significance of B. straminea as a vector of S. mansoni is associated with greater endemicity in northeastern Brazil. Furthermore, an extended geographical distribution of B. straminea in South America has been noticed in recent years606 Teles HMS, Pareira PAC, Richinitti LMZ. Distribuição de Biomphalaria (Gastropoda, Planorbidae) nos Estados do Rio Grande do Sul e Santa Catarina, Brasil. Rev Saude Publica S Paulo 1991; 25:350-352.,1010 Rumi A, Hamann MI. Potential schistosome-vector snails and associated trematodes in ricefields of Corrientes Province, Argentina. Preliminary results. Mem Inst Oswaldo Cruz 1990; 85:321-328.. Michelson & Dubois3131 Michelson EH, Dubois L. Competitive interaction between two snails hosts of Schistosoma mansoni: laboratory studies of Biomphalaria glabrata and B. straminea. Rev Inst Med Trop São Paulo 1979; 21:246-253. defined B. straminea as a species of competitive superiority due to its capacity to invade territory occupied by other species. A number of authors3030 Figueiredo CCSB. Dispersão de Biomphalaria straminea no estado de Sergipe: um estudo comparativo com dezenove anos de intervalo. Mem Inst Oswaldo Cruz 1989; 84:383-387.,3232 Barbosa FS, Pereira da Costa DP, Arruda F. Competitive interactions between species of freshwater snails. I. Laboratory studies: IB. Comparative studies of the dispersal and the vagility capabilities of Biomphalaria glabrata and B. straminea. Mem Inst Oswaldo Cruz 1984; 79:163-167.,3333 Barbosa FS, Pereira da Costa DP, Arruda F. Competitive interactions between species of freshwater snails. I. Laboratory studies: IC. Comparative survival of Biomphalaria glabrata and B. straminea kept out of water. Mem Inst Oswaldo Cruz 1985; 80:155-157. have commented on the displacement of B. glabrata by B. straminea in northeastern Brazil and the high capacity of B. straminea to resist periods of drought, which are characteristic of this region. Naturally infected B. straminea 3434 Santos L, Costa IB, Figueiredo CCSB, Altomani MAG. Primeiro encontro de Biomphalaria straminea (Dunker, 1848) no município de Cruzeiro, vale do Paraíba, Estado de São Paulo, naturalmente infectada por cercarias de Schistosoma mansoni. Rev Inst Adolpho Lutz São Paulo 1980; 40:165-166. have been found in Cruzeiro, in the valley of the Paraíba do Sul River (SP, Brazil). In experimental tests3535 Dias LCS, Ueta MT, Guaraldo AMA. Suscetibilidade de Biomphalaria glabrata, B. straminea e B. tenagophila a diferentes cepas de Schistosoma mansoni. Rev Inst Med Trop São Paulo 1987; 29:205-212, specimens from this municipality were susceptible to human and wild strains of S. mansoni. This species was reported606 Teles HMS, Pareira PAC, Richinitti LMZ. Distribuição de Biomphalaria (Gastropoda, Planorbidae) nos Estados do Rio Grande do Sul e Santa Catarina, Brasil. Rev Saude Publica S Paulo 1991; 25:350-352. in a pisciculture aquarium in Porto Alegre (RS, Brazil). B. straminea and B. tenagophila have been identified in rice fields in Corrientes (Argentina); B. straminea was more abundant than B. tenagophila 1010 Rumi A, Hamann MI. Potential schistosome-vector snails and associated trematodes in ricefields of Corrientes Province, Argentina. Preliminary results. Mem Inst Oswaldo Cruz 1990; 85:321-328. .
The results of the present study confirm the susceptibility of B. tenagophila from Argentina to a S. mansoni strain that originated in sympatric B. tenagophila. The susceptibility of B. straminea to two Brazilian strains demonstrates the potential of this species to establish schistosomiasis foci in Argentina.
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04Graeff-Teixeira C, Anjos CB, Oliveira VC, Velloso CFP, Fonseca MBS, Valar C, et al. Identification of a transmission focus of Schistosoma mansoni in the southernmost brazilian state, Rio Grande do Sul. Mem Inst Oswaldo Cruz 1999; 94:9-10.
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Publication Dates
-
Publication in this collection
15 Oct 2013
History
-
Received
26 June 2013 -
Accepted
27 Sept 2013