Epidemiology and Current Treatment Trends in “ Thelaziasis ”

Thelaziasis is a parasitic disease caused by nematode worms of the Thelazia genus that inhabit the conjunctival sacs of various mammalian hosts, including humans. The disease is primarily reported in areas with high agricultural activity and close proximity to domestic animals. In humans, thelaziasis is a rare but emerging zoonotic disease with increasing incidence worldwide, particularly in Asia. The life cycle of Thelazia spp. involves adult worms residing in the conjunctival sac, where they mate and lay eggs that hatch into larvae. The larvae mature into adults, completing the life cycle, and can cause various clinical signs such as lacrimation, photophobia, conjunctivitis, and mild to severe ocular pain. In rare cases, the infestation can lead to corneal ulceration, keratitis, or even blindness. The transmission of Thelazia spp. occurs through infected flies, particularly fruit flies of the Drosophilidae family, which serve as intermediate hosts. Prevention measures such as wearing protective glasses and avoiding close contact with animals can reduce the risk of transmission. Diagnosis of thelaziasis is made by detecting the adult worms in the conjunctival sac during ocular examination. Treatment involves the mechanical removal of the worms using forceps or suction under local anesthesia, followed by the administration of topical antibiotics to prevent secondary bacterial infection. Systemic antiparasitic drugs such as ivermectin or albendazole may also be prescribed to kill any remaining larvae in the body. This chapter mainly deals with thelaziasis causative agents, epidemiology, transmission, clinical symptoms, diagnosis, treatment, and preventive measures.