Optimizing heartworm diagnosis in dogs using multiple test combinations

Area of Science:

• Veterinary Diagnostics
• Parasitology
• Infectious Diseases

Background:

• Heartworm (HW) diagnostics utilize various methods targeting different Dirofilaria immitis life stages.
• Antigen (Ag) and microfilariae (Mf) tests are common for dogs, while antibody (Ab) tests are validated for cats.
• Heat-treatment (HT) can improve HW Ag test sensitivity by disrupting immune complexes.

Purpose of the Study:

• To compare diagnostic methods for HW infection in high-risk dogs.
• To evaluate individual and paired diagnostic tests, including feline Ab tests in dogs.
• To assess the impact of heat-treatment on HW Ag test sensitivity.

Main Methods:

• One hundred stray adult dogs in Florida shelters were tested.
• Methods included microfilariae (Mf), HW Ag, and HW Ab tests (feline Ab tests used experimentally).
• Two versions of each test platform were employed.

Main Results:

• Point-of-care (POC) Ag tests identified 14 positive dogs; HT Ag testing identified an additional 12.
• Individual Ag test sensitivity/specificity ranged from 50-57%/100% compared to HT Ag.
• Pairing POC Ag with Mf tests improved sensitivity without sacrificing specificity.

Conclusions:

• Screening dogs with both POC Ag and Mf tests enhances diagnostic performance over single Ag tests.
• Current HW testing methods may miss over 25% of infected dogs.
• Improved, accessible, and cost-effective HW testing solutions are needed for shelters.