Canine Anaplasmoses in south and Southeast Asia: A systematic review

Canine anaplasmoses are tick-borne infections caused by two species of bacteria in the genus Anaplasma. Anaplasma phagocytophilum is the causative agent of granulocytic anaplasmosis with a global distribution and the etiological agent of human anaplasmosis while A. platys causes cyclic thrombocytopenia with a lower prevalence. This review offers a comprehensive and up-to-date analysis of canine anaplasmoses in South and Southeast Asia, a region where the disease has not received adequate attention. It provides detailed insights into the prevalence, geographical distribution, clinical signs, diagnostic methods, treatment strategies, risk factors, vectors, and zoonotic potential of canine anaplasmoses encompassing research published from 2000 to 2024. Seventy-one studies met the selection criteria. Infection with A. platys is more prevalent among dogs in the region, with cases reported in 13 countries, compared to A. phagocytophilum, which has been reported only in India and Malaysia. The infection rate of the two species varies widely between 1.3 % - 70.5 %. Concurrent infections with eight other canine pathogens were reported. Although Anaplasma DNA was detected in Rhipicephalus sanguineus, and four other tick species, specific biological vectors for A. phagocytophilum and A. platys have not been identified in these regions. Risk factors for canine anaplasmosis include sex, age, tick infestation, lack of tick-controlling methods, concurrent louse infestation, and climatic factors. Apart from 49 human cases of granulocytic anaplasmosis in India, extent of human infection remains largely unknown. Since most of the studies were limited to specific localities, accurately assessing the disease burden is a challenge. Overall, limited information is available on geographic distribution, prevalence, genetic diversity, vectors, and zoonotic potential of the pathogens in the region.