Seroprevalence and molecular characterization of Leishmania in dogs from an endemic area of zoonotic visceral leishmaniasis in Brazil

Abstract

Visceral leishmaniasis (VL) can cause large-scale and tenacious epidemics with high fatality rates. Current seroprevalence and circulating Leishmania species were evaluated in dogs domiciled in the municipality of Sabará, a small historic and touristic city in the Brazilian state of Minas Gerais. A total of 3926 dogs domiciled in seven different districts of Sabará were serologically tested for canine visceral leishmaniasis (CVL) by indirect enzyme-linked immunosorbent (ELISA) and immunofluorescence (IFA) assays, in a two-years census survey (2011-2012). The average positivity rate of canine infection was 3.4%. Three additional diagnostic tests - imprint/smear direct parasitological, molecular (LnPCR) and myeloculture - were performed in a random sample of fifty seropositive dogs composed of symptomatic (39) and asymptomatic (eleven) animals. LnPCR showed 100% of positivity for Leishmania DNA in, at least, one among four tissue samples tested (mesenteric lymph node, skin, spleen and bone marrow), independently of the clinical canine group. Higher and statistically equivalent positivity rates (98% and 96%) for Leishmania DNA were found in canine lymph node and spleen. Asymptomatic dogs showed expressive positivity rates in all three additional diagnostic techniques. Leishmania infantum was confirmed as the etiological agent of CVL in Sabará.

Keywords: Brazil; Canine visceral leishmaniasis; Dogs; Leishmania infantum; LnPCR; Myeloculture.

Fig. 1

Geographical localization of the municipality of Sabará, in the Metropolitan area of the state capital, in Minas Gerais, Brazil. The Metropolitan area of Belo Horizonte is marked in red (left map). Sabará is marked in green in the expanded map of the Metropolitan area (right map).

Fig. 2

Frequency distribution of additional diagnostic tests for CVL (A) and LnPCR positivity according to canine DNA source (B), in a random sample of 50 seropositive dogs for CVL. The dogs were later classified as symptomatic (dark gray) or asymptomatic (light gray), based on the presence or absence of CVL clinical signs. There was no statistical difference between the clinical canine groups, for any test or DNA source. The dogs were domiciled in Sabará (Minas Gerais state, Brazil). Period of study 2011–2012.

Fig. 3

Agarose gel electrophoresis analysis of mesenteric lymph node canine DNA after LnPCR. The gel was stained by ethidium bromide. Lanes: M-100 bp DNA ladder; 1 to 50-individual seropositive dogs for CVL; PC-Positive DNA control (L. chagasi MHOM/PP75); NC-negative control (no DNA). The red arrows point to the characteristic 353 bp band of Leishmania DNA in the samples. All the dogs were domiciled in Sabará (Minas Gerais state, Brazil). Period of study: 2011–2012.