VTNE Review: Heartworm disease

pathophysiology of heartworms

• reside in pulmonary artery and right ventricle, causing right ventricular hypertrophy

• worms transmitted as L3 larvae through mosquito bites

what bacteria has been identified in heartworms and how is it treated?

wolbachia; doxycycline

clinical signs in dogs

• exercise intolerance

• cough

• dyspnea

• ascites

severe clinical signs in cats

• salivation

• tachycardia

• shock

• neurologic symptoms

• sudden death

• vomiting and weight-loss (chronic symptoms)

heartworm associated respiratory disease (HARD) in cats

syndrome in cats that appears similar to asthma but occurs secondary to heartworm infestation

diagnosis in dogs

• heartworm antigen test (preferred)

• modified knotts test may detect microfilaria (less sensitive than antigen test)

• right sided cardiac enlargement on thoracic radiographs and enlarged pulmonary arteries

• infection may cause proteinuria or an increased eosinophil count

diagnosis in cats

• heartworm antigen test may have false negatives due to low worm burden in cats

• heartworm antibody test indicates exposure but not necessarily active infection

• in some cases, thoracic radiographs and/or echo can aid in diagnosis

treatment for dogs

• melarsomine

• confinement after treatment helps to decrease the chance of thromboembolism

• wolbachia treated with doxycycline

“slow kill” method

involves starting monthly heartworm preventative and waiting for the adults to die

• not recommended by the American Heartworm Society

treatment in cats

• do not tolerate melarsomine

• treatment is usually symptomatic with bronchodilators and/or corticosteroids until the worms die

prevention

• ivermectin (Heartgard)

• milbemycin (Sentinel)

• Moxidectin (Trifexis)

• Selamectin (Revolution)

• Moxidectin Topical (Advantage multi)

• Moxidectin injectable (Proheart)