Which type of transmission is associated with canine ehrlichiosis?

Canine ehrlichiosis is primarily transmitted through the bite of infected ticks. The life cycle of the tick involves the tick feeding on a host animal, becoming infected with the Ehrlichia organism, and then transferring the bacteria to another host animal during its feeding. This cycle is often referred to as host-tick-host transmission, where the tick serves as a vector that facilitates the spread of the disease between dogs. The effectiveness of this transmission method is influenced by factors such as the species of the tick involved, the environment, and the population of dogs that are exposed.

The other transmission methods listed—direct contact, vertical transmission, and airborne transmission—are not the primary mechanisms through which this particular disease is spread. Direct contact usually involves the exchange of bodily fluids or close interaction between animals, which is not how Ehrlichia is typically transmitted. Vertical transmission refers to the transfer of infectious agents from a mother to her offspring, which is not characteristic of ehrlichiosis; while airborne transmission involves pathogens spreading through the air, which does not apply to this tick-borne disease either. Thus, host-tick-host transmission is the correct association for canine ehrlichiosis, emphasizing the role of ticks in its lifecycle and spread.