Severe Skin Lesions Caused by Persistent Bites of the Stable Fly Stomoxys calcitrans (Diptera: Muscidae) in a Donkey Sanctuary of Western Spain.

This research focuses on investigating the main cause of severe skin lesions in donkeys in a sanctuary in western Spain. The findings reveal that persistent bites from the Stomoxys calcitrans stable fly are the primary cause of these skin lesions.

Investigation into the Cause of Severe Skin Lesions in Donkeys

• After numerous donkeys in a western Spain sanctuary showed signs of distinct skin lesions in 2021, a thorough study was conducted to identify potential causes.
• The skin lesions were primarily concentrated on the donkeys’ extremities, and less so on their faces and chests.
• Methods such as the use of cotton leggings to prevent bites, as well as other treatments including antiparasitic, antiseptic washes and dermatitis lotion, were found to be effective in improving the donkeys’ conditions.
• However, skin scraping tests turned up negative for any major causative agents.
• A histopathological examination of the lesions was carried out, revealing inflammatory infiltrate at the superficial dermal level, indicative of a chronic dermatitis condition.

Entomological Study and Results

• Between May and October 2021, a field entomological study was carried out to determine if any specific insect species was responsible for the donkeys’ skin lesions.
• Many Stomoxys calcitrans stable flies were found in sticky traps placed around the sanctuary, as well as in decomposing straw bedding.
• Other species of blood-sucking flies, although in lower numbers, were also found in other traps around the farm.
• Based on the entomological data gathered, the locations of the bites, and the clinical signs observed, it was determined that the S. calcitrans stable fly was primarily responsible for the skin lesions in the donkeys.
• This case was the first known instance of donkeys being affected by the stable fly in Spain.

Differential Diagnoses

• For a more informed diagnosis, a brief discussion was provided considering potential evidence caused by other biting insect groups.