Which flies are responsible for the transmission of Thelazia, an eyeworm found in cattle and horses?

The transmission of Thelazia, the eyeworm affecting cattle and horses, is primarily facilitated by muscid flies. These flies, which include species such as the face fly, are known to feed on bodily fluids and, in the process, may come into contact with the infective larvae of Thelazia. When they feed around the eyes of the host animals, they can inadvertently transfer the larvae, leading to infection. The relationship between muscid flies and Thelazia highlights the role of specific fly species in spreading certain parasitic infections, emphasizing the importance of managing these fly populations in the prevention of such diseases.

Other types of flies, such as fruit flies, house flies, and horse flies, do not play a significant role in the transmission of Thelazia. Fruit flies typically feed on decaying organic matter and do not interact with livestock in a way that would facilitate the transmission of this particular parasite. House flies, while common pests around livestock, are not effective vectors for Thelazia. Horse flies, although known for their painful bites and potential to transmit other diseases, are not involved in the lifecycle of this specific eyeworm. Understanding these details is crucial when managing parasite control strategies in agricultural settings.