Canine cutaneous leishmaniasis.

Canine cutaneous leishmaniasis (CCL) is a significant veterinary problem. Infected dogs also serve as parasite reservoirs and contribute to human transmission of cutaneous leishmaniasis. Histologically, the lesions were nodular to diffuse interstitial granulomatous dermatitis with histiocytic pseudorosettes together with numerous amastigotes within macrophages and occasionally within the interstitium. Organisms were often contained within clear and intracellular vacuoles. The other inflammatory cells, which were present in the biopsies of the Leishmania-infected dog, were lymphocytes and plasma cells. The histopathology results emphasized the role of dog, particularly asymptomatic dog, as reservoirs for CCL because of the high cutaneous parasite loads. These results may help to explain the maintenance of high transmission rates and numbers of CCL cases in endemic urban regions.