Infectivity of promastigotes and amastigotes of Leishmania infantum in a canine model for leishmaniosis

Seven dogs experimentally infected with amastigotes or culture promastigote s of Leishmania infantum MON-1 were observed for a period of up to 38 month s. The course of infection was monitored by clinical and parasitological ex aminations, haematological and serum protein analysis, and by anti-leishman ia antibody levels. Two of the three amastigote-inoculated dogs developed a symptomatic infection with haematological and protein alterations, and a s trong humoral immune response. The third dog was asymptomatic with no haema tological or protein alterations and developed a steady humoral response. F our promastigote-inoculated dogs remained asymptomatic throughout the obser vation period, with only transient antibody responses to leishmanial antige n, and no haematological or protein alterations. The detection of the paras ite in biological material obtained at necropsy showed that dogs with no cl inical signs or other manifestations of disease may be infected. This indic ates that asymptomatic carriers may be present in the canine population, bu t not identifiable by the usual serological tests, and suggests that epidem iological surveys based on serology may underestimate the prevalence of can ine leishmaniosis and the parasite transmission risk. (C) 2000 Elsevier Sci ence B.V. All rights reserved.