Molecular diagnosis of Leishmania spp. in dogs from a subtropical region of Argentina

ASCENCIO M; SARMIENTO N; SCHNITTGER L; FLORIN-CHRISTENSEN M; RODRIGUEZ AE

Congreso; International Congress on Tropical Veterinary Medicine, 2nd Joint AITVM-STVM Meeting; 2018

Leishmaniasis is a disease caused by flagellated hemoparasites of thegenus Leishmania. The parasites are transmitted through the bites offemale Phlebotomus and Lutzomyia sand flies to humans and othermammals. The most important Leishmania parasite that infects humans anddomestic animals in Latin America is L. infantum, also known as L.chagasi, one of the etiological agents for visceral leishmaniasis. Dogs arevery susceptible to this parasite, and act as main reservoirs. Also, they may sufferfrom a complex and deadly syndrome that includes hair loss or scaling, weightloss, skin lesions, deformed and elongated nails (onychogriphosis),hepatomegaly and splenomegaly. However many dogs course asymptomaticinfections. Dogs have also been reported as a domestic source of L.braziliensis, the most widespread etiological agent of American tegumentaryleishmaniasis. In Argentina, human visceral leishmaniasis reemerged in 2006 inthe Northeastern province of Misiones, and following this first case, L.infantum DNA was found in dogs. By early 2015, 140 human cases wereregistered in subtropical provinces such as Salta (NW) and Corrientes (NE) andclinical cases of canine leishmaniasis were observed in two NE localities. Theobjective of this research was to evaluate the presence of Leishmania spp.DNA in the blood of dogs of Mercedes, Corrientes, a town with about 33.000inhabitants, where no human cases have been reported so far, but canineleishmaniasis clinical cases have started to appear. Blood samples wereobtained from 166 domestic dogs of urban and peri-urban areas throughvenipuncture, and stored in tubes with EDTA at -20oC until use. Location,clinical signs if any, age and gender of all individuals were recorded. Chelex100® resin was used for genomic DNA extraction, following an optimized protocolpreviously established in our laboratory. A highly sensitive direct PCR wasused to amplify a 116 bp conserved DNA region of the kinetoplast minicircle,using 13A/13B primers. The results of amplification were verified by agarosegel electrophoresis. Ninety-three out of 166 dogs (56%) were positive for Leishmaniaspp. molecular detection, of which 87% did not show any related clinicalsigns. Within the symptomatic group, hair loss, thinning, peeling of the noseand onychogyphosis were observed. No association was found between percentagesof PCR-positive animals and sex or gender. According to the geographical distributionof PCR-positive and negative samples, we can conclude that there were noparticular infection foci, since cases were distributed throughout the sampledregion (4 km2). Importantly, approximately half of the sampled dogs werepositive for Leishmania spp. with the potential of acting as reservoirs,in spite of the lack of any clinical manifestations. The choice of controlmeasures for canine leishmaniosis has so far been controversial. In Mercedesdistrict, Leishmania-seropositive dogs are euthanized, in an attempt tocontrol the disease. However this measure is upsetting for veterinarians anddog owners on one hand, and on the other serological tests only detect a minorproportion of the infected animals that could be acting as reservoirs. Furtherstudies on this emerging disease, its distribution and vectors are needed tounderstand its epidemiology and design adequate control measures. This work wassupported by Fundación Universidad de Morón (PID 9-2015) and INTA (PNSA111505).