Treatment of Northern fowl mite (Ornithonyssus sylviarum) infestation on poultry in research facilities can be challenging.
The mite has a rapid reproductive cycle (egg to adult in 5 to 7 d), and chemical treatments can be toxic to birds, personnel, and
the environment. In addition, antimite treatment may interfere with experimental research designs. The current study evaluated
the efficacy of topical application of an entomopathogenic fungus, Beauveria bassiana, in the treatment of a naturally occurring
infestation of Northern fowl mites in pen-housed roosters (n = 14; age, 18 mo). Two groups of 7 roosters each were used in 2
experiments: Beauveria (30 mL, 2.9 × 1010 spores per bird) compared with water (30 mL, control), and Beauveria compared with
the common topical organophosphate agent tetrachlorvinphos–dichlorvos (30 mL). We also assessed a higher dose of Beauveria
(300 mL, 2.9 × 1011 spores per bird) in the 7 birds that were not exposed to tetrachlorvinphos–dichlorvos. Beauveria reduced mite
levels relative to the control group but did not outperform tetrachlorvinphos–dichlorvos when used at an equal volume and
frequency. Increasing the volume and frequency of Beauveria application improved outcomes such that visual inspection failed
to detect any mites. The results presented here suggest that, when applied in sufficient doses, Beauveria effectively reduces mites
on poultry and can be an important part of an integrated pest management program. Additional research is needed to document
the most effective dose, frequency, and location of B. bassiana application to control Northern fowl mites in poultry