Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina. I--The dog reservoir: an epidemiological profile.

A community-based survey of household-associated mongrel dogs was undertaken in a rural area of Argentina to investigate pet population dynamics and the behavior of natural Trypanosoma cruzi infection in the reservoir by xenodiagnosis and serologic techniques. Age structure of dog population suggested that individuals participate in the domestic cycle of transmission for a mean period of 4 years; age-specific sex ratios indicated differential survival of female dogs in all age groups, especially among pups. An overall prevalence rate of 84%, increasing from 69% below age 1 to 100% in dogs older than 3 years, strongly support a highly efficient T. crusi transmission to dogs, where eongenital/lactogenic transmission might be involved. A 98% of concordance was found between serologic results and parasitologically confirmed infections. Seroreactive dogs below age 10, unlike humans, showed an age-independent persistence of parasitemia. At least 50% of dogs tested were closely associated with sleeping quarters of people. A highly efficient T. cruzi transmission, close trophic association with Triatoma infestans bugs, age-independent persistence of parasitemia, suitable exposure patterns and high recruitment of susceptible individuals, qualify dogs as amplifying hosts of Chagas' disease in rural communities of central and northern Argentina. Control measures directed to reduce dog-vector contact should be encouraged by primary healthcare programmes, and performed in connection with chemical control of vector bugs.