Association between large strongyle genera in larval cultures--using rare-event poisson regression

Area of Science:

• Veterinary Parasitology
• Equine Health
• Helminthology

Background:

• Intensive anthelmintic use has reduced large strongyle prevalence in horses, while cyathostomins exhibit drug resistance.
• Larval culture diagnostic values for Strongylus vulgaris are variable, and associations with other large strongyles are unclear.

Purpose of the Study:

• To investigate statistical associations between Strongylus vulgaris infection and the simultaneous occurrence of Strongylus edentatus and Triodontophorus spp. in horses.
• To address the diagnostic challenge posed by the rare occurrence of large strongyle species.

Main Methods:

• Modified Poisson regression analysis was employed.
• Data from 663 horses across 42 Danish farms were analyzed.
• Prevalence of S. vulgaris, S. edentatus, and Triodontophorus spp. were determined.

Main Results:

• Individual prevalences were 12% for S. vulgaris, 3% for S. edentatus, and 12% for Triodontophorus spp.
• Both S. edentatus and Triodontophorus spp. showed significant positive associations with S. vulgaris infection (relative risk > 1).
• S. edentatus was associated with selective therapy and negatively correlated with recent anthelmintic treatment.

Conclusions:

• The presence of S. vulgaris in larval cultures can suggest the likely co-occurrence of other large strongyle species.
• These findings improve the interpretation of diagnostic tests for equine strongyle infections.