Heartworm disease in dogs is caused by a parasitic worm called Dirofilaria immitis. This disease is transmitted through the bite of infected mosquitoes. When a mosquito bites a dog, it can introduce the heartworm larvae into the dog's bloodstream. Once inside the dog, these larvae can grow into adult worms, which primarily reside in the heart and pulmonary arteries, leading to severe health issues.

The lifecycle of the heartworm involves several stages:
1. **Infection**: A mosquito bites an infected dog, ingesting microfilariae (the immature form of heartworms).
2. **Development**: The microfilariae develop into infective larvae within the mosquito over 10-14 days.
3. **Transmission**: The mosquito then bites another dog, transferring the infective larvae.
4. **Growth**: Inside the new host, the larvae mature into adult heartworms over a period of 6 to 7 months.
5. **Reproduction**: Adult heartworms can live for several years, producing more microfilariae and continuing the lifecycle.

Preventive measures such as monthly heartworm medications are crucial for protecting dogs from this disease, especially in areas where mosquitoes are prevalent. Regular veterinary check-ups can help in early detection and management of heartworm disease.

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Topics covered in this question:

Dog Health Parasites Preventive Care Dog Diseases Heartworm