Onchocerca cervicalis in horses: dermal histopathology.

The study compares skin tissue samples from Midwestern U.S. horses with and without onchocerciasis, caused by the parasite Onchocerca cervicalis. The major finding is that horses with the disease consistently have perivascular mononuclear dermatitis, a type of skin inflammation. There was no observed seasonal variation in parasite count or immune cell response within the horses, and horses with onchocerciasis also displayed a skin inflammation often related to allergic reactions, known as eosinophilic dermatitis.

Objective of the Research

• The primary objective of this research was to compare the skin histopathology of horses affected with Onchocerca cervicalis parasite, leading to onchocerciasis, and those that are not affected.
• The study aimed to identify any consistent pathological differences between the two groups of horses that could be attributed to onchocerciasis.

Methodology and Observations

• The scientists examined ventral midline skin samples, which were sourced from horses in the Midwestern U.S.
• The key difference identified between the two groups was the prevalence of perivascular mononuclear dermatitis, which is characterised by inflammation of the skin surrounding the blood vessels, in the horses with onchocerciasis. This finding suggests that the disease may noticeably affect the skin of inflicted horses.
• Additionally, no seasonal variance in the number of parasites or in the influx of immune cells was detected. This negates the hypothesis that disease progression or severity might be tied to environmental factors or the horses’ immune response over different seasons.
• Eosinophilic dermatitis, another type of skin inflammation often associated with allergies or parasitic infections, was also noted in horses suffering from onchocerciasis. The cause of this dermatitis in the observed horses remains unknown and might be an area of further research.

Significance of the Research

• This research adds to the collective understanding about Onchocerca cervicalis and how the parasite contributes to onchocerciasis in horses.
• The findings may help to better diagnose the condition by providing additional physical indicators, such as the presence of perivascular mononuclear dermatitis, and to understand the disease’s progression.
• It also sheds light on potential areas for further research, such as the connection between onchocerciasis and eosinophilic dermatitis and the factors that might influence the progression of the disease beyond seasonal variations.