A Field Outbreak of Dictyocaulus filaria in Sheep in the Northwest of Iran

Background and aim: Dictyocaulus filaria is a threadlike worm that lives in the airways of the lungs in sheep and goats and can lead to pneumonia. In November ۲۰۲۲, a report of emaciation, anorexia and, weakness with frequent coughs in a flock of ۱۴۵ sheep (including ۳۰ males and ۱۱۵ females) located in the city of Miyaneh (East Azarbaijan province) was reported to the private sector veterinary clinic. Materials and Methods: During the necropsy of two dead sheep, and by cutting the air ducts and lung tissue, a large number of milky white worms were observed in the bloody secretions of the pulmonary ducts, and the smaller ducts became inflamed due to cellular infiltration and the ducts were filled with bloody exudate. The isolated worms were placed in ۷۰% alcohol and were examined morphologically in the laboratory using an optical microscope. Results: Dictyocaulus filaria worms were diagnosed. Male worms were ۵.۴-۶.۸ cm and females were ۷.۵-۸.۴ cm long. The uterus of the female worm was full of eggs containing larvae, approximately ۹۵-۱۱۰ ×۵۲-۶۵ μ. Infected sheep were treated orally with levamisole at a dose of ۷.۵ mg/kg. Conclusion: The present article is the first report of contamination and loss of sheep due to Dictyocaulus filaria in the field in East Azarbaijan province, Iran. Regular and strategic antiparasitic therapy should be performed using broad-spectrum antiparasitic drugs in small ruminants.