EVALUATION OF DOGS AS SENTINELS OF THE TRANSMISSION OF TRYPANOSOMA-CRUZI IN A RURAL AREA OF NORTH-WESTERN ARGENTINA

Dogs, the main domestic reservoirs of Trypanosoma cruzi in the Argenti ne chaco, may be useful as sentinels of vector-mediated transmission o f Trypanosoma cruzi in control programmes if canine infections acquire d by all other routes could be excluded. In the present study, in the province of Santiago del Estero, Argentina, the dog populations in the neighbouring villages of Amama, Trinidad, Mercedes, Villa Matilde and Pampa Pozo were studied immediately before spraying of residual insec ticides (in 1992 in Amama, Trinidad and Mercedes and 1993-1994 in the other villages) and twice during a subsequent programme of triatomine surveillance (in 1994 and 1996). Overall seropositivity for Trypanosom a cruzi infection (i.e. the proportion of dogs found positive by at le ast two different serological tests in any one survey) steadily declin ed from 65% (54/83) in 1992 to 39% (70/182) in 1994 and 15% (36/237) i n 1996. No seroconversion was detected between the 1994 and 1996 surve ys in any dog aged >2 years. However, among the dogs aged <2 years (wh ich were born after virtual elimination of Triatoma infestans from the villages), seropositivity fell from 15% (12/81) in 1994 to 5% (6/131) in 1996. Thirteen demographic, behavioural and entomological variable s were analysed by logistic multiple-regression analysis for their ass ociation with seropositivity in dogs born locally during the surveilla nce programme. The total number of Triatoma guasayana collected in the bedroom areas of the owner's house, having a mother which was seropos itive for Trypanosoma cruzi, and the number of seropositive dogs with which it cohabited were all found to be significant predictors of sero positivity in any dog. The results are the first indication that Triat oma guasayana is the vector responsible for the new cases of Trypanoso ma cruzi infection seen in dogs in domestic or peridomestic sites duri ng the surveillance programme.