In the present study, D. immitis infection was detected in 29.7% of shelter dogs. The overall heartworm prevalence found in this study was higher than previous reports in owned dogs (3.1%) [7] and shelter dogs (16.0%) [21] across Texas. Several factors could be associated with this difference, including population of dogs tested, lack or lower frequency of heartworm prophylaxis, and diagnostic testing decision. In the canine population, MK is considered the preferred and most sensitive concentration method to detected and differentiate mf of D. immitis from other filarioid nematodes [3, 8]. However, MFDT cannot detect amicrofilaremic infections and should always be performed in association with heartworm antigen tests to prevent false negative results [3, 8]. Although the sensitivity and specificity rate vary among of the commercial heartworm antigen test kits, antigen testing is considered the most sensitive diagnostic method [3]. The ELISA methods have shown higher sensitivity and specificity rates ranging from 85.7% to 100% depending on the number of mature female D. immitis present [3, 10].

The use of molecular approaches for diagnosing heartworm infections has increased over the past years, including conventional PCR and qPCR targeting nuclear and mitochondrial genes [4, 22, 23]. The integration of molecular assays in the diagnosis of filarial infections has been shown to be an efficient and reliable screening tool to confirm the disease in intermediate and definitive…