The parasite Dirofilaria immitis causes heartworm disease in dogs. Infection with this parasite occurs when a female mosquito bites your dog and transfers larvae into your dog’s system. The larvae travel through the blood vessels and into the heart, where they grow for six to seven months. Once mature, these worms can reach 14 inches. Once worms reach adulthood, symptoms such as breathing difficulty begin to present in your dog.
Disease Course and Symptoms
Once worms reach full maturity, they begin to affect the function of the heart. They interrupt the heart valves and clog blood vessels. This affects the normal blood supply to the heart, lungs, liver and kidneys. Symptoms of heartworm infection include dry coughs, shortness of breath, weakness, nervousness, lethargy and loss of stamina. With increased exercise or activity, sudden death is possible. As the infestation worsens, destruction of lung, liver and kidney tissue occurs.
Treatment and Prevention
Treatment does exist for heartworm and involves injectable drugs to kill the adult worms and microfilariae, or immature heartworms. According to VCA Animal Hospitals, treatment is successful in 95 percent of cases. Heartworm preventative medications exist to prevent infestation. Antigen tests must rule out current infestations before preventative medications can be prescribed.