Demonstrated laboratory effectiveness of an anthelmintic medicated feed for the treatment of Oxyspirura petrowi infections in northern bobwhite (Colinus virginianus).

Abstract

In May 2024, a medicated anthelmintic feed was approved by the U.S. Food and Drug Administration to treat parasitic infection in wild quail following evidence linking parasites to northern bobwhite (Colinus virginianus) population impacts. During the approval process, it was confirmed that the feed significantly reduced parasite burdens in wild bobwhite populations after 3 weeks of treatment. However, no studies were conducted on the drug's efficacy in individual bobwhite in a controlled laboratory setting. In this study, we infected pen-reared bobwhite with Oxyspirura petrowi, an eyeworm commonly found in wild bobwhite. We treated the birds with anthelmintic feed for 3 weeks at different frequencies (0, 2, and 5 times/week) to determine the optimal feed amount and feeding frequency for parasite control. One third of the birds were euthanized weekly and examined for O. petrowi. A stepwise Poisson regression revealed that the total amount of feed eaten was the strongest predictor of the number of live O. petrowi found. None of the categorical variables assessed, including feeding frequency, affected the predicted parasite reduction. All birds that consumed ≥38.887 g of feed were parasite-free, although this may be a liberal estimate, as 15 of the 48 worms were not recovered from birds not given anthelmintic feed. In addition to the feed, factors such as the bobwhites' innate immune responses or potential unnoticed worm injuries likely contributed to the reduced O. petrowi numbers. Regardless, this study determined that a medicated anthelmintic feed effectively reduces O. petrowi infection intensity in individual bobwhite. Additional findings include observing O. petrowi migration between eyes and determining whether O. petrowi tissue is resorbed or expelled after parasite death.