Which animal is most significantly affected by the brown dog tick?

The brown dog tick, scientifically known as Rhipicephalus sanguineus, primarily targets dogs as its main host. These ticks have a strong affinity for canines and are known to thrive in environments populated by dogs. The importance of this relationship is evident as brown dog ticks can transmit various diseases to dogs, including canine ehrlichiosis and babesiosis, which can have serious health implications for the affected animals.

While humans may occasionally be bitten by these ticks, the primary and most significant impact is on the dog population. This is why the answer focuses specifically on dogs as the most affected animal by the brown dog tick. The other options may mention humans and cats, but the centrality of the brown dog tick's lifecycle and its role as a vector for disease strongly emphasizes dogs as the primary concern.