The subclinical form of experimental visceral leishmaniasis in dogs

Abstract

Pathological aspects of a subclinical form of experimental canine leishmaniasis is reported here for the first time. Fifteen mongrel dogs were used in the present study. Eight dogs were infected and seven were used as control. Four of the control dogs were inoculated with spleen cells from non-infected hamsters. The eight mongrel dogs inoculated intravenously with amastigotes forms of Leishmania chagasi evolved for periods as long as 25 months without any clinical characteristic sign of classical Visceral Leishmaniasis (VL). Most of the laboratory test results were compatible to those of the seven control animals but culture of bone marrow aspirated material and serologic testing (IIF) demonstrated or provided evidence that the animals were infected. The most important and predominant histopathological lesion in infected animals were epithelioid granulomas presented in the liver, spleen, adrenal gland and lung of some animals. Channels containing erythrocytes in some granulomas of the liver suggest that these granulomas are formed inside sinusoidal capillaries. Despite the animals were proved to be infected and presented characteristic histologic lesions, they did not present external signs of disease. The granulomatous aspect of the lesions indicates a good immunologic reactivity and suggest that a host-parasite equilibrium does exist in the dog experimental model.

Clinical, Parasitologic, and Immunologic Evolution in Dogs Experimentally Infected with Sand Fly-Derived Leishmania chagasi Promastigotes

“…11,12,28 Our finding of small liver granulomas, an indication of an active cell mediated immune response, in the intradermally infected dogs is consistent with what was observed in resistant dogs naturally infected in endemic areas. [29][30][31] However, the previous work by Killick-Kendrick and others 10 showed development of severe disease (timing or nature not specified) in 48% of dogs infected intradermally with approximately 10 5 L. infantum promastigotes isolated from the mid guts of infected sand flies. These dogs were followed for a prolonged period (5 years), whereas the dogs in our study were followed only for 1 year.…”

The fucose-mannose ligand-ELISA in the diagnosis and prognosis of canine visceral leishmaniasis in Brazil.

“…21 The parasitologic tests also show lower sensitivity, with positive results only in cases of advanced canine visceral leishmaniasis. 10 An analysis of a cohort of 1,798 naturally infected dogs showed that sensitivity compared to parasitology was 99.2% for the IF assay and 92.1% and 85.8% for a rapid test antibody for L. donovani (TRALd) when performed in the laboratory or in the field, respectively (Genaro O, unpublished data). If the field screening were performed only by analysis with TRALd (Corixa Corp., Seattle, WA), 14.2% of the dogs already parasitologically confirmed to have kala-azar would not be detected or removed from the area, and thus would survive as Leishmania reservoirs.…”

“…However, it is known that in human and canine kala-azar, antibodies to Leishmania appear in the circulation soon after infection, leading to an early subclinical period. 10 The early detection of infected dogs in the field could improve the control program since it would identify dogs that are still subclinical but already infective for sand flies. 3 We have recently tested the diagnostic and predictive value of the fucose-mannose ligand (FML)-ELISA for human kala-azar in Brazil.…”

Comparison between splenic and lymph node aspirations as sampling methods for the parasitological detection of Leishmania chagasi infection in dogs

“…Accurate diagnosis of canine infection by Leishmania is essential in veterinary practice, since the treatment of infected dogs includes 15-20 daily injections of potentially toxic drugs, and in some countries, killing of infected animals is one of the measures applied in order to control the disease dissemination (Costa & Vieira 2001, Moreno & Alvar 2002. Dogs with symptomatic disease have fever, anemia, skin lesions, emaciation, hypergammaglobulinemia, hepato-splenomegaly, and lymphoadenomegaly, among other signs of the disease (Feitosa et al 2000, Moreno & Alvar 2002 cells of internal organs such as spleen, liver, and bone marrow (Oliveira et al 1993). In dogs, parasites are also found in peripheral lymph nodes and skin.…”