Heartworms are among the most common and serious health threats dogs face. It was once thought that heartworms were a problem only in southern climates, but it is now known that heartworms are a threat worldwide. Heartworms are present on every continent in the world with the exception of Antarctica.

All dogs are at risk for heartworms. Those that spend extended periods of time outside are at especially high risk. Heartworms are spread by mosquitoes. The parasite spend part of their life cycle in the mosquito. The mosquito ingests the larvae when it bites an infected dog. The larvae is deposited when it bites another dog. They burrow into the dog. When they reach adult form, they travel to the right side of the dog’s heart, where they may remain for several years. Female heartworms produce thousands of young each day. The young can circulate in the dog’s blood stream for up to 3 years before another mosquito bites and provides a host. The larvae must remain in the mosquito for about 10 days in warm climates before reinfecting a dog. As heartworms multiply, they infest the chamber on the right side of the heart as well as the lungs. They may also infest veins entering the liver and heart. Heartworms are fatal if left untreated.

A dog may have heartworms for years without showing any symptoms. Often, when the symptoms occur, it is often too late for treatment.The dog may die as soon as 72 hours after he or she begins exhibiting symptoms.

Symptoms can include coughing, fatigue, fainting, and difficulty breathing. Treatment for heartworms is safer now than it has been in the past, but there is still a risk the dog will die. Early detection increases the chances of survival. Dogs should be tested every spring for heartworm infection.

The best treatment for heartworm is prevention. Heartworm prevention is available, usually in the form of a monthly pill, available from veterinarians. The pills work by killing the young before it has a chance to mature and reproduce. Dogs should be tested prior to starting heartworm prevention as it may cause severe reactions in infected dogs. Heartworm prevention is not 100% effective, so dogs must still be tested once a year.

Cats are also susceptible to heartworms. Although infection is not as common as it is in dogs, heartworms can still occur in cats in areas where heartworm infestation is high. Prevention is available for cats, check with your veterinarian to see what he/she recommends for cats in your area.

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