Local investigation into the role of Culicoides species diversity (Diptera: Ceratopogonidae) in recurrent horse dermatitis cases in southwest France.

The study investigates the role of a particular type of insect, known as Culicoides, in recurrent horse dermatitis cases in southwest France. The results indicate that horses are constantly exposed to the bites of these insects, even indoors, and highlight the need for ongoing research and surveillance.

Research Purpose and Background

• The researchers aimed to investigate the role of insects from the genus Culicoides in causing recurrent dermatitis, also known as ‘sweet itch’, in horses. This skin condition is common in France, affecting approximately 10% of horses, and is caused by an allergic reaction to the saliva of biting flies.
• Previous studies on the subject were limited, hence this study engaged in a field survey in southwest France to identify the species of Culicoides associated with horse populations and estimate their abundance based on trapping site location. The study also aimed to identify whether these insects were present indoors, which could indicate a higher risk of exposure for horses.

Research Methodology

• Three Onderstepoort Veterinary Institute (OVI) traps were used to trap insects once a week, from mid-June to the end of July 2022.
• These traps were placed both indoors and outdoors near horse facilities and used during the known peak activity period for adult insects.

Results of the Study

• The study found that Culicoides obsoletus/scoticus was the most abundant species (58.3%), followed by C. circumscriptus (12.1%), C. nubeculosus (11.5%), C. punctatus (5.6%) and others.
• It was noted that C. obsoletus/scoticus and C. circumscriptus were notably present indoors, accounting for 54% and 11.4% of captures respectively.

Conclusions and Recommendations

• The research highlights the continuous exposure of horses to bites from Culicoides, including those that occur at night and indoors.
• The authors underscore the need for continuous research and monitoring to better understand and manage the effects of exposure to these insects.