Molecular diagnosis and risk factors of canine ehrlichiosis in the municipality of Itabuna-Bahia, Brazil

Abstract

Ehrlichiosis is an emerging zoonosis worldwide and has had several adverse effects on public health. Canine monocytic ehrlichiosis (CME), caused by Ehrlichia canis, has the tick Rhipicephalus sanguineus as the vector. The main clinical signs in affected dogs are fever, apathy, anorexia, weight loss, and neurological signs. The diagnosis is made through the association of clinical signs with parasitological, serological, and molecular tests. The aim of this study was to evaluate the occurrence of E. canis infection in dogs from the city of Itabuna-Bahia, as well as to identify the risk factors related to infection. For this, 405 dogs from the Center for Zoonoses Control (CCZ), non-governmental organizations (NGOs), and dogs domiciled and semi-domiciled in the city of Itabuna, southern Bahia, were evaluated. After initial physical evaluation of the dogs, blood samples were collected by venipuncture for subsequent DNA extraction and E. canis testing using the nested Polymerase Chain Reaction (nested-PCR) technique. In addition, an epidemiological questionnaire that included questions related to the animals was administered to the dog owners to identify the risk factors for exposure to the etiological agent and to the vector. Approximately 17% of the dogs in the municipality of Itabuna-Bahia tested positive for E. canis by nested-PCR, a result higher than that found in other studies conducted in the same municipality. Among the factors associated with E. canis infection, contact with other dogs (p = 0.0226) was an important factor for the dissemination of CME, since dogs are reported to be reservoirs of E. canis. Male dogs (p = 0.0016) presented lower risk for E. canis infection. Other studies, however, describe no association between animal gender and infection by E. canis. Preventive measures to reduce exposure to the vector of ehrlichiosis are necessary.