Dirofilaria Immitis is the scientific name for heartworm. These scrounging roundworm spread from one host to another through mosquito bites which commonly affects dogs. Heartworm parasites are small thin like threads that lives mostly in the lung arteries. It damages the tissues and lung vessels of the animal that leads to health problems. Sporadically, heartworms that are fully developed migrate at the right side of the heart of its host. Hence, it makes the veins swell and infected, this leads to severe disease that can result to death. Although it’s more common in dogs, some animals like foxes, cats, wolves, sea lions, as well as other animals can also be infected. However, in rare cases, humans too can be afflicted with these types of parasites.
Course of Infection
Parasitic heartworms have to undergo some stages of its life to become mature and infect the hosts’ heart. These parasites use mosquitoes as their carrier to continue their cycle of life by transporting the eggs or young ones from one host to another. However, in order to have a successful transmission, mosquito’s temperature should be 27°C and above for 2 weeks, otherwise heartworm cycle will be immobilized. The spread usually occurs during the warm season because these parasites need warmth in order to live and survive inside the mosquito’s salivary glands before transmission. The infection begins when the tainted mosquito bites the dog. Since the infection spreads in the body of the animal through blood flow, the heartworm will be carried all over the body and will reside mostly in the lungs and heart. Those parasites that reside inside the dogs’ heart will wait for six to seven months to become adults and multiply.
3rd stage (L3) – after being infected, the larval heartworms that have been injected by the infected mosquito will grow and develop in as little as 1 to 2 weeks.
4th stage (L4) – on this stage, the larval will begin to molt beneath the skin where the dog was bitten. After molting, the heartworms will travel to other parts of the body such as the abdomen and chest; they will stay there for 45 up to 60 days after the date of infection.
5th stage (L5) – the parasite will molt again to become immature adults. Within 75 to 120 days of infection, these immature parasites will then penetrate the bloodstream and will carry them to the heart. Heartworms will live there and will increase it size on the next three to four months. The male heartworms are around 23cm while female will grow up to 30cm long. The male heartworms can be distinct by looking at its tail that is coiled.
After 6 to 7 months of infection, the adult heartworms have already mated and females are starting to produce offspring that are called “microfilariae”.
The new heartworms can live and flow in the hosts’ bloodstream for up to 2 years. They will stay there and wait for another cycle until a mosquito bites and sucks the blood out of the infected animal. Once the mosquito ingested the microfilariae, it will go through stages of molting that will process it to be an infectious 3rd larval phase. The microfilariae will travel to the mosquito’s salivary glands and stay there until the mosquito bites a new breeding place for the heartworms. Microfilariae’s incubation time can be as short as 2 weeks or up to 6 weeks long before it can be transmitted to a new host. However, this will depend on the climate, the warmer the better. If the temperature goes below 14°C or 57°F, the heartworms larval cycle of life will come to an end.