Risk Factors for Seroconversion by Leishmania infantum in a Cohort of Dogs from an Endemic Area of Brazil

Abstract

Visceral leishmaniasis (VL) has recently emerged in various urban and peri-urban areas of Brazil and other countries. Understanding the urbanization of VL requires identification of risk factors associated with human and canine infection. To determine the predictors of risk for canine VL, a survey was conducted of 1,443 dogs, from which a cohort was selected (n = 455) and evaluated for approximately 26 months. Serology was conducted with two enzyme-linked immunosorbent assays (ELISA): one conducted in the Laboratory of Zoonosis of the Belo Horizonte Health Department (LZOON) and the other in the Laboratory of Immunopathology of the Federal University of Ouro Preto (LIMP). A molecular diagnostic method (PCR–restriction fragment length polymorphism) and a structured questionnaire were also used. To identify the factors associated with seroconversion, two time-dependent Cox regression models were performed with different sensitivities (model 1, seroconversion by ELISA/LZOON; model 2, seroconversion by ELISA/LIMP). The overall incidences of seroconversion were 6.5/1000 dogs-months and 11.2/1000 dogs-months for ELISA/LZOON and ELISA/LIMP, respectively. Increased risk of seroconversion was associated with short fur (model 1: hazard ratio [HR] 1.9), the presence of dry leaves (model 1: HR 2.8) or manure (model 1: HR 3.5) in the backyard, dogs sleeping predominantly in the backyard (model 2: HR 2.1), the presence of symptoms (model 2: HR 2.0), and positive molecular results during follow-up (model 2: HR 1.5). Decreased risk was associated with insecticide spraying in the house (model 2: HR 0.5). These results indicate that more-vulnerable domiciles, certain dog behaviors, lack of vector control measures, and positive molecular results were associated with the occurrence of canine VL. Furthermore, it is important to emphasize that PCR-positive dogs should be monitored, owing to the possibility of seroconversion. Identifying risk factors for seroconversion in dogs is crucial for developing adequate strategies for VL prevention and control.

Seroprevalence and risk factors associated with visceral leishmaniasis in dogs in Jaciara, State of Mato Grosso

“…Epidemiological studies indicate that the infection is associated with particular risk factors such as the length of an animal's coat, the areas in the house frequented by the dog 4 , and the socioeconomic and demographic indicators of the region 5 . The aim of this study was to determine the seroprevalence of CVL in urban and rural areas by identifying the risk factors involved in the transmission of this disease in the municipality of Jaciara, State of Mato Grosso.…”

“…Short-coated dogs have twice the risk of infection as longhaired dogs because the protection afforded by long hair hinders biting by phlebotomines 4 ; In fact, all dogs in the rural areas were had short coats.…”

“…Although, the knowledge of the owners about the sandfl ies be related to increased risk of infection, a result of exposure to the vector, as reported in the State of Minas Gerais 8 or of the ineffectiveness of control measures in the study area considered endemic. Furthermore, few owners implemented control measures such as using repellent collars and/or environmental insecticides 4 , or having their dogs vaccinated against CVL or castrated as a means of population control. These measures were also investigated in this population.…”

Factores de riesgo en escenarios emergentes de leishmaniasis visceral urbana, Misiones, Argentina

“…Así, la presencia de árboles, el manejo de residuos orgánicos y la percepción de la calidad de los servicios públicos no mostraron una asociación con el riesgo de la leishmaniasis visceral humana. Estas condiciones se han asociado a la abundancia de vectores en Posadas (9,10), mientras que en un foco de Brasil, la infección asintomática por L. infantum en humanos se asoció positivamente con la ausencia de residuos (35).…”

Evaluation of a Prototype Flow Cytometry Test for Serodiagnosis of Canine Visceral Leishmaniasis

“…During such periods, B lymphocytes do not secrete polyclonal antibodies, and consequently, serological methods are less sensitive at this stage of infection (30,31). Moreover, it has been observed that these dogs are more likely to seroconvert than are PCR-negative dogs (32). Vaccines against CVL have been promoted as an important tool and a cost-effective strategy for controlling the disease (33).…”