Seroprevalence and molecular surveillance of Dirofilaria immitis in shelter dogs from central New Mexico, USA

BACKGROUND: Dirofilaria immitis, the causative agent of canine heartworm disease, is a mosquito-borne filarial nematode, endemic to most of North America. Clinical signs may include coughing, exercise intolerance, abnormal heart sounds, and lethargy, which can lead to heart failure and death in severe cases. For accurate diagnosis, the American Heartworm Society (AHS) recommends testing dogs annually for the detection of heartworm antigens and microfilariae. In this study, we assessed the prevalence and potential risk factors for D. immitis in dogs from Albuquerque, New Mexico, using antigen and microfilariae detection tests. METHODS: , Zoetis) with pre- and post-immune complex dissociation (ICD) via heat treatment, although this is not currently recommended by AHS. Following genomic DNA extraction, we also screened whole blood using a newly optimized probe-based real-time polymerase chain reaction (qPCR) assay. To assess the potential association between D. immitis presence and risk factors, including age, sex, breed group, and coat color, a univariate analysis was performed using Fisher's exact test or the chi-squared test. RESULTS: Serum of 4 (0.99%) dogs tested antigen-positive pre-ICD, while 14 (3.47%) dogs tested antigen-positive post-ICD. We did not detect any positive dogs for D. immitis microfilariae by the probe-based qPCR. No risk factors were associated with the detection of the D. immitis antigen in this dog population. CONCLUSIONS: Although microfilariae were not detected in this study, it is possible that infections were in the early stages of disease progression, with D. immitis detected in pre- and post-ICD via antigen testing. Low seroprevalence and the absence of microfilariae DNA detected highlight the importance of using both pre- and post-ICD antigen detection alongside molecular-based microfilariae tests, particularly for companion animals living in low-endemic regions and for shelter populations that are less likely to be on heartworm prevention.