Frequency and Clinical Epidemiology of Canine Monocytic Ehrlichiosis in Dogs Infested with Ticks from Sinaloa, Mexico

Ehrlichia canis is a rickettsial intracellular obligate bacterial pathogen and agent of canine monocytic ehrlichiosis. The prevalence of this disease in veterinary medicine can vary depending on the diagnostic method used and the geographic location. One hundred and fifty-two canine blood samples from six veterinary clinics and two shelters from Sinaloa State (Mexico) were analyzed in this study. All animals were suspected of having Canine Monocytic Ehrlichiosis (CME). The diagnostic methods used were the ELISA (Snap4Dx, IDEXX) together with blood smear and platelet count. From all dogs blood samples analyzed, 74.3% were positive to E. canis by ELISA and 40.1% were positive by blood smear. The sensitivity and specificity observed in the ELISA test were 78.8% and 86.7%. In addition, thrombocytopenia was presented in 87.6% of positive dogs. The predominant clinical manifestations observed were fever, anorexia, depression, lethargy, and petechiae. Consequently, this is the first report in which the morulae were visualized in the blood samples, and E. canis-specific antibodies were detected in dogs from Sinaloa, Northwest of Mexico. 1. Introduction Ehrlichia canis is the causative agent of canine monocytic ehrlichiosis (CME). Moreover, CME is an emerging disease in veterinary medicine, and E. canis has been considered in the last decade as a potential zoonotic pathogen [1, 2]. It is a worldwide disease transmitted by a tick bite. The competent vector for its transmission is the Ixodidae ticks Rhipicephalus sanguineus and Dermacentor variabilis [3]. In dogs, the CME is a multiphase disorder that progresses in three stages: acute, subclinical, and chronic. Each phase is characterized by several clinical and hematologic abnormalities. Thrombocytopenia is a common finding in E. canis infected dogs and many clinicians tend to use it as an indication for antibiotic treatment, and it is observed in 84% of the cases and its severity varies in the different disease phases [4]. During the subclinical stage a moderate thrombocytopenia is observed, while the chronic phase is characterized by severe leukopenia and anemia. In this stage dogs show other complications such as hypocellular marrow, suppressed splenic sequestration, decreased life of platelets, and an increase of circulating migration-factor platelet inhibitor [3, 4]. The relationship between the magnitude of thrombocytopenia and prevalence of E. canis has been established in countries such as Brazil in 2004 where 84.1% of infected dogs showed thrombocytopenia [3]. Taken together, more data is necessary to