Thelaziids

Affected hosts: The primary hosts for these parasites are cattle, horses, and various small ruminants. While these organisms do not infest plants, their presence represents a critical management issue in the animal husbandry sector of agriculture, as they directly impact the physical condition and market value of livestock.

Biology and life cycle: The life cycle involves an intermediate host, typically filth flies (genus Musca). The fly ingests the larvae while feeding on the lacrimal secretions of an infected animal. Inside the fly, the larvae develop into an infective third-stage form. When the fly visits another animal to feed, the larvae are deposited into the eye, where they mature into adults.

Damage and impact: Infestation causes severe irritation, manifesting as conjunctivitis, keratitis, and corneal opacification. Infected animals experience significant pain, photophobia, and excessive tearing. If untreated, the condition leads to ulceration of the cornea and permanent loss of vision, which significantly hinders the growth and productivity of the affected herd.

Protection and control: Management of Thelaziidae requires a dual approach focusing on the host and the environment.

• Systemic treatment of infected livestock with macrocyclic lactones.
• Implementation of fly control programs in pastures and stables.
• Use of protective masks or repellents on animals during peak fly activity.
• Sanitary maintenance of animal housing to reduce breeding sites for flies.
• Regular veterinary check-ups for early detection of eye worms.