Ehrlichia canis in dogs of Mexico: Prevalence, incidence, co-infection and factors associated.

Rickettsial infections in dogs of Mexico were investigated. A total of 246 dogs were blood sampled and initially screened to detect Ehrlichia canis, E. chaffeensis, E. ewingii, Anaplasma phagocytophilum and Rickettsia rickettsii by a quantitative real-time PCR (qPCR) assay. Sixty-five dogs were monitored and sampled twice 7-8 months apart. Using the qPCR, 72 positive dogs to E. canis were detected (prevalence of 29.26%). These dogs were also tested by nested PCR to detect the same pathogens. None of the studied dogs were positive to E. chaffeensis, E. ewingii, R. rickettsii nor A. phagocytophilum by both PCR assays. The cumulative incidence of E. canis infection was 38.46%. Sequencing analysis of the nested PCR products revealed 100% and 98.1% identity of E. canis and R. parkeri, respectively. We found a dog co-infected with E. canis and R. parkeri.

Ticks infesting dogs in rural communities of Yucatan, Mexico and molecular diagnosis of rickettsial infection.

Rickettsial infection in dog-associated ticks in three rural communities of Yucatan, Mexico was investigated using qPCR and nested PCR assays. A total of 319 dogs were studied and ticks samples were collected. A total of 170 dogs were infested with ticks (frequency of 53.4%). Overall, 1,380 ticks representing seven species were collected: Amblyomma mixtum, A. ovale, A. parvum, A. cf. oblongoguttatum, Ixodes affinis, Rhipicephalus microplus, and R. sanguineus sensu lato. The most abundant species was R. sanguineus s.l. with a mean intensity of 7.4 ticks/host. Dogs in the communities of Chan San Antonio and Yaxcheku were 2.84 and 2.41 times more likely to be infected with R. sanguineus compared with Sucopo (p < 0.05). Adult pools of A. mixtum, A. parvum, I. affinis, R. microplus, and A. c.f. oblongoguttatum were negative to E. chaffeensis, E. ewingii, A. phagocytophilum, and R. rickettsii. However, pools of R. sanguineus s.l. adults and A. ovale adults, as well as nymphs of Amblyomma spp. were positive to E. canis. Sequencing analysis of the nested PCR products amplifying the 16S rRNA gene fragment of E. canis confirmed the results and revealed 100% identity with sequences of E. canis. This is the first report worldwide of E. canis infection in A. ovale by PCR. This finding does not necessarily indicate that A. ovale is a competent vector of E. canis because pathogen transmission of this specific tick to a naïve dog remains to be documented. This study documented that different tick species parasitize dogs in Yucatan, Mexico, where R. sanguineus s.l., A. ovale, and nymphs of Amblyomma spp. were shown to be infected with E. canis. These findings highlight the need for control strategies against tick infestations in dogs to prevent the risk of tick-borne disease transmission among companion animal and probably human populations.