Molecular detection and factors associated with selected tickbone zoonoses in dogs in Chilanga district in Zambia

Abstract

Vector borne diseases, also referred to as zoonoses, have been responsible for some of the worst plagues of mankind. The close relationship between humans and animals increases chances of transmission of vector-borne zoonoses. Among some of these infections are pathogens transmitted by ticks which are currently considered to be second only to mosquitoes as vectors of human infectious diseases in the world. Tick-borne zoonoses are not considered a priority due to resource constraints and focus on other more fatal vector-borne diseases. The aim of this study was to determine the prevalence of specific canine associated tick-borne zoonotic pathogens including Rickettsia species, Ehrlichia canis and Anaplasma phagocytophilum in dogs. A cross sectional study was conducted from February 2016 to September 2016. A total of 301 canine blood samples were collected from three localities in Chilanga district and analyzed at University of Zambia School of Veterinary Medicine. The Polymerase Chain Reaction (PCR) was performed using species specific primers targeting a portion of the 16S rRNA gene for the Anaplasma spp and Ehrlichia canis and gltA gene for Rickettsia species. Approximately nine positive samples of Anaplasma spp and 15 positive samples of E. canis were sequenced using the Genetic Analyzer 3130 Applied Biosystems (AB, USA). Epidemiological data was analyzed using the Chi-square test and logistic regression in SPSS version 20. Out of the total 301 dogs sampled, 79.7% had ticks on them. The prevalence of Rickettssia spp was 0.3%, Ehrlichia canis was 34.9% and that of Anaplasma spp was 9%. The risk factors found to be associated with increased prevalence of infection with tick-borne pathogens of zoonotic importance included breed of dog, use of the dog, its level of confinement as well as the method of tick control used by the owner. For E. canis infections, the factors that were found to increase the risk of infection by zoonotic tick-borne pathogens were use of non-conventional tick control methods and functions dogs were occupied with specifically hunting as well as roaming with odds ratios of 2.0, 10.0 and 3.0, respectively. For Anaplasma spp infection, age and breed were found to be factors influencing infection. Dogs younger than one year old were more likely to be infected (OR = 2.4) compared to the older dogs aged one year and above. Mongrels were nine times more likely to be infected by Anaplasma spp compared to the cross breeds. After sequencing, Ehrlichia spp. in our study showed 100% similarity to Ehrlichia canis. Two types of Anaplasma spp. were detected, the first type was similar to Anaplasma platys and the second type was similar to Anaplasma spp closely related to A. phagocytophilum detected in South African Dogs. The results of this study indicated that tick-borne zoonotic pathogens are prevalent in canines in Chilanga District and this portrays a potential risk of human exposure because of their companionship with dogs. Therefore, there is need to raise awareness of the dangers to the communities about the threat of these pathogens as well as the remedial measures they can easily use to reduce the risk to themselves through quality care of their animals