Assessment of the speed of transmission of Ehrlichia canis, Anaplasma phagocytophilum, and Borrelia burgdorferi sensu stricto by infected ticks through an in vitro experimental model

Background Canine vector-borne diseases (CVBDs) have significant clinical and public health implications. Methods This experimental study used a validated continuous flow in vitro feeding system (CFIFS) to investigate the speed of transmission (SOT) of three tick-borne pathogens (TBPs): Ehrlichia canis by laboratory-infected Rhipicephalus sanguineus (18.3% infection rate), Anaplasma phagocytophilum by laboratory-infected Ixodes ricinus (56%), and Borrelia burgdorferi sensu stricto (s.s.) by laboratory-infected I. ricinus (76%). Three experiment were conducted, one per pathogen/tick model. Fifty eight to sixty ticks were used per feeding systems. Four to six replicates were done per experiment. All ticks were from lab-reared. The tick infections were performed by feeding the nymphal stages on infected hosts. Results All ticks began to attach and feed three hours after being introduced to the feeding system. At the maximum of attachment, 89.7% of R.sanguineus were attached at 57 hours, 4 to 30% of attachement at 51 hours for I.ricinus infected with A.phagocytophilum and 6.3 to 47.9% at 48 hours for I.ricinus infected with Borrelia burgdorferi s.s.. PCR tests were used to detect the presence of pathogens from blood samples collected every three hours. Swab samples from the inner face of the feeding membrane were also collected and tested every six hours during the B. burgdorferi s.s. study. In this experimental in vitro design, after the first tick attachments were noticed, Ehrlichia canis has a SOT of 3–6 hours, A. phagocytophilum of 12–15 hours, and B. burgdorferi of 42–45 hours in blood, but only 3–6 hours on inner membrane swabs. Conclusion The findings of this in vitro study highlight the transmission time of some tick-borne pathogens, confirming previous data obtained in vitro or in vivo, by using the same design for all tick/pathogen model. It is a way to estimate the possibility of using acaricidal drugs to block pathogen transmission based on the speed of transmission and the speed of kill of these compounds.