BACKGROUND Dogs are the main peridomiciliary reservoir of Leishmania infantum thus the correct diagnosis of infection is essential for the control of the transmission and treatment as well. However, the diagnosis is based on serological assays that are not fully effective. OBJECTIVE We aimed to establish an effective serological assay for the diagnosis of L. infantum infected dogs using Leishmania-derived recombinant antigens. METHODS Leishmania derived rK39-, rK28-, rKR95-based enzyme-linked immunosorbent assay (ELISA) was standardized using symptomatic and asymptomatic L. infantum-infected dogs. Then 2,530 samples from inquiry in endemic areas for VL were evaluated and the results compared with recommended assays by the Brazilian Ministry of Health (MH algorithm). Further samples from a cohort of 30 dogs were searched. FINDINGS For rK39-, rK28- and rKR95-ELISA the sensitivity was around 97% and specificity 100%. The positivity of these three ELISA in the inquiry samples was 27-28%, around 10% higher than the assays currently in use. When cohort samples were searched, we observed likely false-negative results (> 65%) with supposedly negative samples that turned positive six months later with the assays in use (MH algorithm). MAIN CONCLUSIONS For the diagnosis of L. infantum-infected dogs, rK39-based ELISA showed better diagnostic performance than other assays in use in Brazil and worldwide.

Com o objetivo de avaliar os fatores de risco e a classificação clínica associados à soropositividade para Leishmaniose Visceral Canina (LVC) no município de Colares, estado do Pará, foram coletadas e analisadas 435 amostras de soro sanguíneo de cães de ambos os sexos, idade a partir de 4 meses, com ou sem de raça definida e com ou sem sintomatologia clínica sugestiva da doença, dos bairros e das localidades da zona rural. A sorologia foi realizada empregando-se os métodos Ensaio Imunoenzimático (ELISA/S7) e Reação de Imunofluorescência Indireta (RIFI), em lâminas fixadas com antígenos de Leishmania infantum. O sexo não apresentou significância estatística (P > 0,05). Observou-se prevalência significativa de LVC com relação à faixa etária e classificação clínica (P < 0,05). A prevalência foi maior para cães na faixa etária menor de 2 anos e para os classificados clinicamente como sintomáticos, sendo que Onicogrifose e alterações cutâneas foram as alterações clínicas mais frequentes.

In order to evaluate the risk factors and clinical classification associated with seropositivity for Canine Visceral Leishmaniasis (CVL) in the city of Colares, Pará State, 435 serum samples were collected from dogs of both sexes, aged from 4 months, with or without standard breed and with or without clinical symptoms suggestive of disease, from the neighborhoods and the rural areas, and analyzed. Serology was performed using immunoenzymatic assay (ELISA/S7) and Immunofluorescence Assay (IFA) methods in fixed slides with antigens from Leishmania infantum. Sex did not present statistic significance (P>0.05). There was significant prevalence of LVC regarding age and clinical classification (P < 0.05). The prevalence was higher for dogs aged less than 2 years and for those classified as clinically symptomatic, and onychogryphosis and skin changes were the most common clinical changes.

A ocorrência de dirofilariose pulmonar humana relaciona-se com a prevalência de infecção por Dirofilaria immitis na população canina. Várias espécies de mosquitos são vetores desse nematóide. Analisaram-se amostras de sangue canino coletados nas vilas Pingo d'Água e União, município de Salvaterra (Ilha do Marajó, PA), em junho, 2004 (n=34) e abril, 2005 (N=90). Os diagnósticos parasitológico e imunológico (ELISA - kit SNAP® 3DX™, Biobrasil) foram comparados (chi2, alfa=0,05) no exame de 34 amostras. A prevalência na população (N=90) foi avaliada pelo ELISA. O ELISA revelou mais positivos (25/34; 73,5%) que a gota espessa (23/34, 67,6%) e o Knott (21/34, 61,8%), mas a diferença não foi significativa (p>0,05). A freqüência de infecção por D. immitis na faixa de 0 a 2 anos foi 58%, enquanto em cães mais velhos foi 100%. A prevalência da dirofilariose canina em Pingo d'Água e Vila União foi alta (53,5%), indicando risco de transmissão do parasito às pessoas nessa área.

The occurrence of human pulmonary dirofilariasis maintains a relation with the prevalence of Dirofilaria immitis infection in the canine population. Several mosquito species are vectors of this nematode. Canine blood samples collected in Pingo d'Água and União villages, Salvaterra municipality (Marajó Island, Pará), in June, 2004 (n=34) and April, 2005 (N=90) were analyzed. Parasitological and immunological (ELISA - kit SNAP® 3DX™, Biobrasil) diagnoses were compared following the examination of 34 samples. The prevalence in the population (N=90) was evaluated by means of ELISA. ELISA revealed more positive samples (25/34; 73.5%) than thick smears (23/34, 67.6%) or Knott (21/34, 61.8%), but the differences were not significant (p>0.05). The frequency of D. immitis infection was 58% in dogs ranging from 0-2 years old, whereas in older dogs it was 100%. The prevalence of canine dirofilariasis was high in Pingo d'Água and Vila União (53.5%), indicating the risk of parasite transmission to the people in this area.