Cross-sectional spatial and epidemiological analysis of canine visceral leishmaniasis cases in the triple border region, Brazil, Argentina and Paraguay, between 2015 and 2020

Abstract

Visceral Leishmaniasis is one of the most important vector-borne zoonoses in the world. In 2013, the first autochthonous canine case of the disease in the state of Paraná, southern region of Brazil, was reported in Foz do Iguaçu, on the triple border between Brazil, Argentina and Paraguay. In 2015, the first human case was related. Once the endemic was confirmed, the Zoonoses Control Center (ZCC), an agency of the Municipal Health Department, started actions to implement the Human Visceral Leishmaniasis (HVL) Surveillance and Control Program (VLSCP), of the Ministry of Health. Between 2015 and 2020, 12,205 dog samples were analyzed for the diagnosis of the disease. A prevalence of 37.94% (4,630 samples) was found: 2016 had the highest prevalence, with 46.25%, and the year with the lowest prevalence was 2020, with 25.98%. Possible risk factors for dogs were analyzed, and the results obtained were: whether the request for the exam was performed by the ZCC was a significant protective factor, with a lower prevalence (37.5%) than dogs coming from private clinics (OR = 0.89, p-value = 0.016). Males were significantly more infected than females, with 41.1% and 35.7% positivity, respectively (OR = 1.24, p < 0.0001). Companion dogs and mixed breed dogs were significantly less affected than the other groups tested (OR = 0.44, p < 0.001; OR = 0.79, p = 0.012, respectively). The dogs' dark coat color was a significant risk factor with respect to the other color categories. Short and medium coat sizes were significantly considered risk factors, with 41.3% and 31.3% positivity. Long-haired dogs had only 22.7% positivity. In univariate analyses, giant, large and medium dogs were significantly more affected than small dogs. Dogs up to four years of age were significantly less affected than those in other age groups. There was a coincidence of human and canine cases in the spatial distribution. However, according to the literature, a higher incidence would be expected in humans, due to the high prevalence found in dogs. Therefore, further studies should be carried out to understand the dynamics of the disease in this region.