Background: Canine Visceral Leishmaniasis is a zoonosis affecting dogs worldwide. Its epidemiological importance is observed in Brazil, wherein the largest number of cases originates in the Northeast Region of the country. The disease is caused by the etiologic agent Leishmania chagasi (= infantum) and transmitted by an invertebrate form of sand fly of the genus Lutzomia. Domestic dogs are one of the main reservoirs. The aim of this study was to use molecular analysis to diagnose dogs naturally infected with Leishmania spp. in the city of Jequié, State of Bahia, Brazil, and to describe the clinical signs, as well as the hematological and biochemical profiles associated with these cases.Materials, Methods & Results: In the present study, 198 dogs underwent physical examination and had blood samples collected for hematological, biochemical and PCR tests for Leishmania infantum. Two primers have been used for the molecular diagnostic technique (PCR): first, the ITS-1 specific to Leishmania species followed by the PCR-RFVL to identify the genus; and second, the primer pair RV1/RV2 specific to the Leishmania infantum species in all the samplesAmong the 198 samples collected, four animals tested positive for the Leishmania infantum via PCR, two of which were symptomatic and two asymptomatic. Among the symptomatic animals, animal one presented with diffuse alopecia, ulcerated lesions on the tip of the ears, ophthalmopathy, onychogryphosis, cachexia, anemia and neutrophilic leukocytosis, and animal two presented with alopecia, pustules, crusting, diffusely-spread erythema, anemia, hyperproteinemia, thrombocytopenia and azotemia. Among the two asymptomatic dogs, one animal had anemia, hyperproteinemia, thrombocytopenia, leukocytosis with neutrophilia, and azotemia; the other animal’s laboratory findings revealed hyperproteinemia and leukocytosis with neutrophilia.Discussion: Although 48 animals presented clinical signs, as well as hematological and biochemical alterations commonly reported in the available literature on Leishmaniasis, only two tested positive by PCR. This implies that a positive diagnosis for this pathology should not be given only based on nonspecific clinical and laboratory data. On the other hand, two animals positive via PCR were asymptomatic, and could act as silent disseminators of the parasite in the region. Since the region is considered endemic for the disease, many dogs may be in the chronic phase, with low parasitemia. The fact that blood with low parasitemia was examined may have influenced the estimate of the ocurrence, as it is common knowledge that in such cases the PCR can deliver a false-negative result due the low amount of DNA for amplification. The ideal tissue should be obtained from the spleen, liver, lymph nodes or via bone marrow puncture. However, it was not possible to collect this kind of tissue due to the need for general anesthesia, which is a limiting factor when the study is conducted with domiciliated animals. Clinical signs found in positive animals involve different systems, due to the multisystemic nature of the disease, and evaluation for differential diagnosis is essential to rule out other pathologies that lead to similar changes, such as systemic lupus erythematosus, ehrlichiosis, and babesiosis, among others. Some of the hematologic changes found in positive animals included: anemia, hyperproteinemia, leukocytosis; all of which are respectively correlated with spinal cord dysfunction, splenic sequestration and hyperglobulinemia due to the intense immune response. We concluded that the PCR enabled the identification of canine visceral leishmaniasis cases in the city of Jequié. However, our study did not identify a relationship between the molecular positivity of dogs to Leishmania infantum and the clinical signs and the hematologic and biochemical analysis of samples from suspected cases.Keywords: zoonosis, molecular diagnosis, symptomatology, DNA sequence.
Investigation of canine visceral leishmaniasis in a non-endemic area in Brazil and the comparison of serological and molecular diagnostic tests
