Retrospective analysis of feline heartworm disease (Dirofilaria immitis): diagnostic patterns in cats presenting with respiratory or vomiting signs (2013–2023, USA)

Feline heartworm infection, caused by the mosquito-borne nematode Dirofilaria immitis , is a serious and potentially fatal disease in cats. The true prevalence of this infection is likely underestimated due to the nonspecific nature of clinical signs, such as coughing, vomiting, or respiratory distress, and the diagnostic limitations of current feline heartworm antigen (Ag) and antibody (Ab) assays. This study aimed to enhance understanding of its recognition and detection by linking diverse clinical presentations with diagnostic test results. Anonymized feline medical records spanning 10 years from more than 1,000 Banfield U.S. veterinary clinics were analyzed using machine learning methods. Cats were included if records contained respiratory, vomiting, or heartworm-specific diagnostic codes and at least one heartworm Ag or Ab test. Test positivity rates were linked to clinical signs. For cats tested with both assays, concordance between results was assessed. Of 146,111 eligible cats, 91,438 (62.58%) underwent heartworm testing, and 1,555 (1.70%) were positive on at least one assay. Cats with heartworm-specific diagnostic codes had the highest positivity, but those with respiratory or vomiting codes accounted for 7.01 and 10.10% of all positives. Among 127 cats tested with both assays, 24.41% were discordant, mainly Ag-positive/Ab-negative. Heartworm infection should be considered in any cat with respiratory signs (including asthma-like presentations) or vomiting. To improve its detection, both heat-treated Ag and Ab assays should be used to screen cats annually, and in cats presenting with respiratory signs or vomiting.