A cross-sectional study on canine Leishmania (L) infantum chagasi infection in Amazonian Brazil ratifies a higher prevalence of specific IgG-antibody response than delayed-type hypersensitivity in symptomatic and asymptomatic dogs

Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil / Federal University of Par?. Tropical Medicine Institute. Bel?m, PA, Brazil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Public Health Department. Health Care Secretary of Barcarena. Barcarena, PA, Brazil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Medical School of S?o Paulo University. Pathology Department. S?o Paulo, SP, Brazil. Medical School of S?o Paulo University. Pathology Department. S?o Paulo, SP, Brazil. Medical School of S?o Paulo University. Pathology Department. S?o Paulo, SP, Brazil This was a cross-sectional study which analyzed the prevalence and the clinical and immunological spectrum of canine Leishmania (L.) infantum chagasi infection in a cohort of 320 mongrel dogs living in an endemic area of American visceral leishmaniasis in the Amazonian Brazil by using, mainly, the indirect fluorescence antibody test (IFAT-IgG) and the delayed-type hypersensitivity (DTH), and the parasite research by the popliteal lymph node aspiration. The IFAT and DTH reactivity recognized three different immune response profiles: (1) IFAT((+))/DTH((-)) (107 dogs), (2) IFAT((-))/DTH((+)) (18 dogs), and (3) IFAT((+))/DTH((+)) (13 dogs), providing an overall prevalence of infection of 43 per cent (138/320). Thus, the specific prevalence of IFAT( (+) )/DTH( (-) ) 33.4 per cent (107/320) was higher than those of IFAT( (-) )/DTH( (+) ) 5.6 per cent (18/320) and IFAT( (+) )/DTH( (+) ) 4.0 per cent (13/320). Moreover, the frequency of these profiles among 138 infected dogs showed that the IFAT( (+) )/DTH( (-) ) rate of 77.5 per cent (107/138) was also higher than those of 13.0 per cent (18/138) of IFAT( (-) )/DTH( (+) ) and 9.5 per cent (13/138) of IFAT( (+) )/DTH( (+) ) rates. The frequency of asymptomatic dogs (76 per cent-105) was higher than those of symptomatic (16.6 per cent-23) and oligosymptomatic ones (7.4 per cent-10). A total of 16 (11.6 per cent) L. (L.) i. chagasi isolates were obtained from infected dogs, all from the IFAT( (+) ) /DTH( (-) ) profile: 41 per cent (9/22) from symptomatic, 33.3 per cent (3/9) from oligosymptomatic, and 5.2 per cent (4/76) from asymptomatic dogs. These findings strongly suggested that despite the higher frequency of asymptomatic dogs (76 per cent-105), the majority (72.4 per cent-76) was characterized by the IFAT( (+) ) /DTH( (-) ) profile with a doubtful immunogenetic resistance against infection.