The role of dogs in the epidemiology of human visceral leishmaniasis in northern Pakistan.

Infantile visceral leishmaniasis (VL) was first reported from north Pakistan over 3 decades age in the remote valleys of the western Himalayas. These foci were reported as being completely devoid of domestic dogs. The later emergence of sporadic cases of infantile VL in the sub-Himalayan region of the country, where dogs are abundant, enabled us to investigate the prevalence of canine disease and study its relation with disease in humans. A serological survey in dogs by direct agglutination test (DAT) and enzyme-linked immunosorbent assay (ELISA) indicated that 18% (DAT) and 26.6% (ELISA) harboured anti-Leishmania antibodies, with older dogs showing higher prevalence; 10% of the infected dogs had no clinical signs of leishmaniasis. Deoxyribonucleic acid (DNA) probing by 32P-labelled Lmet 2 cDNA probe showed high sensitivity with aspirates obtained from the popliteal lymph nodes of dogs but not with skin snips. Parasites isolated from dogs in these foci were identified as L. infantum by isoenzyme characterization.