Heartworm—Feline

Heartworm is transmitted to cats by the bite of an infected mosquito. The larvae migrate away from the entry site, where many die in the subcutaneous tissue. Within 50–80 days of infection, the larvae become immature adults that migrate via blood to the main pulmonary artery, where final maturation and mating occur.

New research indicates that feline heartworm infection causes pathology not only when the heartworm reaches an adult stage but also during the immature development stages.
Feline Heartworm
Diagnosis
Treatment

The symptoms of feline heartworm are often non-specific and transient, making it difficult to diagnose by clinical signs alone.

There are two serologic tests available—antigen and antibody tests. Antigen tests detect the presence of an adult infection and have a similar sensitivity to canine tests. The specificity is very high. Antigen tests are highly specific and result in few false positives. Antibody tests, on the other hand, indicate that the cat has mounted an antibody response to a previous infection. A positive antibody test may indicate that the cat is currently infected with juvenile or adult worms, or may indicate a previous heartworm infection. 

The American Heartworm Society and other industry leaders recommend following up positive tests with:

  • Another antigen test
  • Radiographs
  • Blood work, at the practitioner’s discretion depending on clinical assessment

This allows the practitioner to better understand the stage of infection in the cat.

Feline Heartworm Antigen Diagnostic Algorithm

Feline Heartworm Diagnostic Algorithm

View/print the feline heartworm algorithm. (PDF)