Ecological changes
from water resources development projects often affect the epidemiology of water-associated
diseases. In order to investigate the occurrence and distribution of freshwater
snails of medical and veterinary importance in the area of influence of the Serra
da Mesa Hydroelectric a survey has been performed since 1997 and revealed the
occurrence of well-established populations of
Biomphalaria straminea
(Dunker, 1848) in the 8 municipalities surrounding the lake. Areas of epidemiologic
risk for schistosomiasis were selected and studies of parasite-mollusc compatibility
were undertaken using specimens from 19 populations of
B. straminea and
3 strains (CM, EC and PB) originally isolated from
B. straminea. Among
1,135 specimens used 15 became infected (infection index of 1.3%) and 8 populations
were susceptible to the schistosome strains:
B. straminea from Campinorte
(Castelão, susceptible to CM and EC strains, and Planeta Água, EC strain),
Colinas (Tocantinzinho river, CM and EC strains), Minaçu (Canabrava river,
EC strain), Niquelândia (Codemin, CM and PB strains, and Almas river, CM
strain), Uruaçu (touristic area, PB strain) and Santa Rita do Novo Destino
(Maranhão river, CM and EC strains). These results, associated with marked
social and ecological changes occurred, strongly suggest the possibility of
B.
straminea coming to act as a vector of schistosomiasis in the studied area.