Serological, clinical and histopathological changes in naturally infected dogs with Leishmania infantum in the Khemisset province, Morocco.

Canine leishmaniasis (canL) is widespread in the north of Morocco and the Leishmania infantum local strains are highly virulent. An epidemiological survey was carried out in 1993-1995 in the Khemisset province. In this region, the severity of the disease was assessed during regular visits to the identified foci by clinical examination of 323 dogs. Clinical signs were protean and occurred in various combinations. Biopsies were made on available sick dogs; the main histological changes were severe infiltration of the spleen, lymph nodes and bone marrow by mononuclear cells and hyperplasia of macrophage cells with amastigotes in their cytoplasm. The seroprevalence among 323 dog sera tested by ELISA showed a rate of 16.71%. The highest prevalence of the disease was 23.6% in the Sid El Ghandour hamlet. A comparison of the results of this study with those from the year following the first examination on the same site (Sid El Ghandour) of 67 dogs showed that the disease prevalence had not increased significantly (23.6% to 25.33%).

Immune response against Leishmania antigens in dogs naturally and experimentally infected with Leishmania infantum.

Cell-mediated and humoral immune response in naturally and experimentally infected dogs was studied using crude and pure antigens. Both types of infections induced severe signs of visceral disease, but the symptoms observed in natural infections were more pronounced than in experimental infections. In addition, asymptomatic infections were not observed in experimentally infected animals. Disease evolution in laboratory infections was rapid and an increase in antibody titer to crude parasite antigen was correlated with the appearance and aggravation of clinical symptoms. Peripheral blood lymphocyte proliferation to crude antigen and pure gp63 was observed early following experimental infection, but was abolished once the infected dogs began to exhibit clinical signs. A similar pattern was observed in naturally infected dogs. Serum from all patent dogs showed high antibody titers to rK39 in enzyme-linked immunosorbent assays (ELISA), and reacted by western blotting with several antigens, 12 to 120 KDa, including gp63 and gp70. In the case of asymptomatic dogs. antibody titers to crude antigen were low and only a few antigens were identified by western blotting. None of the pure proteins examined, gp63, gp70, and rK39 were recognized by western blotting or ELISA. However, asymptomatic dogs exhibited specific lymphocyte proliferation to both crude antigen and the potential vaccine candidate gp63.