Peer-reviewed veterinary case report
Heartworm screening in shelter dogs using qPCR and antigen tests
By Negron, Veronica et al.·Published in Parasites & vectors·2022·Department of Veterinary Pathobiology, United States·View original on PubMed →
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Original publication title: Probe-based qPCR as an alternative to modified Knott's test when screening dogs for heartworm (Dirofilaria immitis) infection in combination with antigen detection tests.
- Species:
- dog
Plain-English summary
A group of 300 shelter dogs in Texas were tested for heartworm infection, which can cause serious health issues. The dogs were screened using two methods: a traditional test that looks for heartworm larvae in the blood and a newer DNA test that detects heartworm DNA. The results showed that both tests were effective, with the DNA test detecting heartworm in about 20% of the dogs, while the traditional test found it in about 22%. This study suggests that the DNA test could be a reliable alternative to the traditional method for diagnosing heartworm in dogs.
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Abstract
BACKGROUND: Current recommendations for diagnosis of Dirofilaria immitis infection in dogs rely on the detection of antigen produced largely by adult females coupled with the visualization of microfilariae (mf) in the circulation via a microfilaria detection test (MFDT). It is hypothesized that qPCR assays used in parallel with antigen detection tests will perform better in detecting mf than modified Knott's test (MK), when combined with antigen detection. This study compares probe-based qPCR and MK techniques for mf detection used in parallel with the DiroCHEKantigen test to screen for heartworm infection in shelter dogs. METHODS: Matching blood and serum samples were collected from 300 shelter dogs in Brazos and Harris counties, Texas, USA. Blood was assessed for the presence of mf via MK and the presence of D. immitis DNA by a species-specific probe-based qPCR assay. Serum samples were tested for the presence of heartworm antigen using DiroCHEKbefore and after immune complex dissociation (ICD) via heat treatment. In addition, the performance of each diagnostic test was evaluated via Chi-square test, Cochran's Q test, and post hoc analysis. RESULTS: Qualitatively, MK detected mf in 22.0% (66/300) of samples, 55 of which were morphologically identified as D. immitis and 11 as Acanthocheilonema reconditum. The range of heartworm mf was 28 to 88,803 mf/ml (median: 6627.5). Real-time PCR detected D. immitis DNA in 20.7% (62/300) of samples. Heartworm antigen was detected in 24.7% (74/300) of samples pre-ICD, and in 29.3% (88/300) post-ICD. When comparing tests, the Chi-square and McNemar's tests showed that the difference between positive and negative proportions was statistically significant. The Cochran test showed the difference in the distributions of cases and non-cases was significant when individual tests were combined (χ = 62.3, df = 3, P < 0.0001) and when parallel methods were combined (χ = 43.1, df = 4, P < 0.0001). CONCLUSION: Considering individual and combined test performances, practicality, and efficient use of bench time, this heartworm-specific probe-based qPCR method is a viable option as a mf detection test to be used in parallel with antigen tests for canine heartworm infection in diagnostic and research settings.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/36038928/