Researchers testing 402 shelter dogs in Albuquerque found that the number classified as positive for Dirofilaria immitis antigen differed before and after a heat-based serum process called immune complex dissociation. Four dogs, or 0.99%, were antigen-positive before the process. Afterward, 14 dogs, or 3.47%, were positive.
Whole-blood samples were screened with a probe-based real-time polymerase chain reaction assay, or qPCR, a method that looks for parasite genetic material. No Dirofilaria immitis microfilariae DNA was detected. The combination means the study did not establish that every post-treatment antigen-positive dog had active infection.
The two tests did not agree
The sample came from a single shelter in Albuquerque, Bernalillo County. Serum and whole blood were collected between January and September 2023. Sampling was opportunistic and took place before spay or neuter surgery in dogs estimated to be older than 6 months. Researchers recorded estimated age, sex, American Kennel Club breed group and coat color.
Serum was tested with the DiroCHEK ELISA under pre- and post-immune-complex-dissociation conditions, with positive and negative controls. In the post-treatment procedure, 250 µL of serum was heated to 103 °C for 10 minutes and then centrifuged at 16,000 RCF for 10 minutes.
Whole-blood DNA was screened with a probe-based real-time qPCR assay. The researchers compared antigen detection with age, sex, American Kennel Club breed group and coat color using univariate Fisher’s exact or chi-squared tests, with P-values of 0.05 or less as the cutoff.
The pre-treatment estimate had a 95% confidence interval of 0.27% to 2.52%, while the post-treatment estimate had a 95% confidence interval of 1.91% to 5.77%. Those ranges describe uncertainty around the estimates in this sampled shelter group; they do not make the result a prevalence estimate for all dogs in New Mexico.
Why the result is hard to interpret
The authors say the antigen-positive, qPCR-negative pattern can be compatible with early or occult infection, very low microfilarial concentrations, recent heartworm-prevention treatment or cross-reactivity with other parasites. Here, cross-reactivity means a test reaction to material from another parasite. Heat treatment may allow that reaction, so post-treatment antigen positivity may not always represent Dirofilaria immitis infection.
Confirmatory follow-up testing or diagnostic imaging would be needed to classify antigen-positive, qPCR-negative dogs. Until then, the findings are best read as a local estimate of antigen positivity rather than proof that every post-treatment positive represented active infection.
Univariate analysis found no potential association between antigen detection and estimated age, sex, American Kennel Club breed group or coat color. That result is an association analysis, not evidence that any demographic characteristic causes infection risk.
The study’s reach is limited. It describes 402 dogs from one shelter in Albuquerque, sampled in 2023, and does not provide direct evidence about owned dogs, other shelters, the wider New Mexico dog population or humans. Clinical history was unavailable at sampling, limiting epidemiological interpretation in this shelter population.
Paper data and sources
Original title: Seroprevalence and molecular surveillance of Dirofilaria immitis in shelter dogs from central New Mexico, USA.
Authors: Maureen A Kelly, Alexa Starnes, Mary Schech et al.
Journal/Repository: Parasites & vectors
Status: Peer-reviewed
First online: 2026-08-20
DOI: 10.1186/s13071-026-07341-0
Original paper · Full text