Which parasite is primarily spread through mosquito bites to dogs?

• A. Flea
• B. Coccidia
• C. Tapeworm
• D. Heartworm

Answer: (D)

The essential idea here is vector-borne transmission via a mosquito. Heartworm disease is spread when a mosquito bites an infected dog, picks up larvae, and then transmits those larvae to another dog during a subsequent bite. The larvae migrate and mature in the heart and pulmonary arteries, which leads to coughing, exercise intolerance, and other signs of heart and lung disease. This is why heartworms are classically described as mosquito-borne parasites in dogs.

Fleas are common vectors for certain tapeworms, but they’re not the primary route for heartworm transmission. Coccidia are protozoa that spread through ingestion of oocysts in contaminated environments, not through mosquitoes. Tapeworms typically transmit when a dog ingests an infected flea or undercooked meat, not via mosquito bites. The key distinction is that heartworm relies on mosquitoes for transfer, while the others rely on different routes. Regular heartworm prevention and annual testing are important in areas with mosquitoes.