Chronic respiratory disease in a horse infected with Dictyocaulus arnfieldi.

The study presents a case of chronic respiratory disease in a six-year-old Thoroughbred horse caused by Dictyocaulus arnfieldi infection, contracted from a shared pasture with a donkey.

Case Overview

• The study revolves around a six-year-old Thoroughbred gelding that displayed symptoms related to respiratory disease developed after the horse was placed on a pasture occupied by a donkey.
• Primary symptoms included a harsh, dry cough and an increased effort to exhale. These symptoms persisted despite attempts to alleviate the condition with corticosteroid therapy and bronchodilators.

Procedure and Findings

• Medical investigators observed eosinophils, a type of white blood cell, in the horse’s tracheal and bronchial mucus. The presence of increased eosinophils usually signals an allergic reaction or infection.
• Further examination revealed Dictyocaulus arnfieldi, a commonly found parasite in horses, especially those sharing grazing lands with donkeys or mules.
• The identification of Dictyocaulus arnfieldi in the mucus implied that the horse had been infected by the parasite, which led to the development of the respiratory disease. The parasite is of the lungworm variety, which affects the airway of horses causing a cough and difficulty breathing.

Treatment and Outcome

• To counter the infection, the horse was treated with high-dose thiabendazole, an anthelmintic medication used to treat worm infestations.
• The medication was administered at 10 times the therapeutic dosage (440 mg/kg) for two successive days. This aggressive treatment resulted in a permanent cessation of the clinical signs, indicating the pathology was related to the detected lungworms.

Significance of the Study

• This study highlights the potential for respiratory disease development in a horse due to Dictyocaulus arnfieldi infection, particularly when the horse shares a pasture with an infected donkey.
• The research underscores the crucial role that early detection and identification of the causative factors play in the successful treatment of the disease, as conventional therapies (corticosteroid and bronchodilators) proved ineffective.
• This study raises awareness about the risk to horses from Dictyocaulus arnfieldi present in shared pastures with donkeys, and the need for parasite control measures.