Can Heartworm Disease in Dogs Be Cured with Symptoms?

Characteristics and Life Cycle of Heartworms

The heartworms of the genus Dirofilaria belong to the family Onchocercidae and are characterized by their slender, white appearance. The male worms measure between 12 to 16 centimeters in length, featuring a short, blunt tail that curves spirally at the end. The female worms, on the other hand, are longer, reaching 25 to 30 centimeters, with a straight tail and are capable of giving birth to live larvae, known as microfilariae, which lack a protective sheath.

Heartworms utilize fleas, dark flies, or mosquitoes as intermediate hosts. Adult worms reside in the right ventricle and pulmonary artery of the host, while the microfilariae circulate throughout the body's bloodstream. When a mosquito feeds on an infected host, it ingests the microfilariae, which then develop into infective larvae. When the mosquito feeds again, it injects these larvae into the dog's body. The journey from the initial infection to the reappearance of microfilariae in the dog's bloodstream takes approximately six months. Adult worms can survive within the host for several years, and the occurrence of the disease is closely linked to the activity of mosquitoes.

Symptoms and Pathological Changes

The earliest symptoms include chronic coughing, which intensifies during exercise, along with fatigue. Subsequently, palpitations become more frequent, the pulse becomes weak, and heart murmurs may be heard. Palpation of the liver area may reveal pain, and there may be fluid accumulation in the chest and abdomen, leading to an increase in abdominal circumference and generalized edema. Breathing difficulties, especially after exercise, are common. In the later stages, anemia, progressive weight loss, weakness, and eventual systemic failure can lead to death. In some cases, seizureslike neurological symptoms may occur, and sudden death can result from the massive infestation of the right ventricle and vena cava.

Upon postmortem examination, findings may include endocarditis, cardiac hypertrophy, dilatation of the right ventricle, and pulmonary endocarditis. Severe cases may lead to venous congestion, causing ascites and liver enlargement. In cases of heavy infestation, a large number of heartworms can be observed in the right ventricle and pulmonary artery.

Differential Diagnosis

(1) Heartworm Disease vs. Canine Hepatitis

Both conditions present with liver pain, jaundice, and weakness. However, in canine hepatitis, the dog's feces may first become dry and then loose, with a pale color (grayishgreen). The liver dullness area expands, and the urine may turn a dark brown color. Dogs with hepatitis may become drowsy or comatose in the later stages, with increased serum bilirubin levels. They may also cough, become swollen, and have a rapid heartbeat.

(2) Heartworm Disease vs. Canine Cirrhosis

Both conditions involve liver pain, jaundice, and ascites. However, in canine cirrhosis, the liver initially becomes slightly enlarged and painful, then gradually shrinks and hardens. In the later stages, there may be spasms, drowsiness, and no coughing. The dog may become swollen and have a rapid heartbeat.

(3) Heartworm Disease vs. Canine Tuberculosis

Both conditions present with chronic coughing (worse with exercise), progressive weight loss, fatigue, ascites, jaundice, liver pain, and breathing difficulties. However, canine tuberculosis can cause an increase in body temperature and may present with purulent or bloody nasal discharge.

Reminders

The primary clinical manifestation of heartworm disease is a decline in cardiovascular function, which is more common in dogs over two years of age, while it is rare in dogs under two years old. Microfilariae can be detected in the blood by examining a blood smear under a microscope. Serological diagnosis is also possible, and ELISA kits are commonly used for clinical diagnosis.