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Editor,—We report five cases of thelaziasis, including a rare case of infection of a hospital inpatient. Thelaziasis is a nematode infection of ocular tissue that is caused by Thelazia callipaeda, which is found in China, India, Thailand, Korea, and Japan. This parasite has been identified in the conjunctival sac, and lacrimal gland and canal of dogs, cats, cows, badgers, rabbits, foxes, and monkeys in Asia.1
Thelaziasis results when flies ingest embryonated eggs in the ocular tissue of an infected host; the eggs develop into larvae and are deposited onto the conjunctiva of a new host. Drosophilae—namely,Amioto okadai, A magna, and A nagatai, are the intermediate hosts.2
To our knowledge, with the exception of Japan 157 cases have been reported worldwide (China, 124; Korea, 24; Thailand, 5; India, 2; Russia and Indonesia, 1 each). In Japan, approximately 100 cases have been reported, mostly in the western regions, especially in Kyushu (66 cases).3 4 To date, there have been no reported cases of inpatient infections.
The clinical features of the five patients are summarised in Table 1. Patients (three men, two women; ages, 57 to 83 years) were examined at Muikaiti Hospital and Tuwanokyouzon Hospital from 1989 to 1999. Patients 1, 2, 3, 4 were outpatients, but patient 5 was an inpatient who had been hospitalised for more than a year. There were no other cases in the same hospital ward or infection of medical personnel. All patients were infected unilaterally (three right eyes, two left eyes). The patients' subjective symptoms were foreign body sensation, visual disorder, and ocular pain. Patient 5 had senile dementia and her symptoms are unknown. Clinical findings were conjunctival congestion, follicles, and whitish worms in the conjunctiva. Patients did not report having had flies in their eyes, but do keep animals such as dogs, cats, and cows. They had never visited the Kyushu region of Japan. The worms were removed (two to five worms per patient) with forceps using topical anaesthesia and antibiotic eye drops (Fig 1). The patients' symptoms resolved and there were no recurrences. The presence of the Thelazia callipaeda worms was confirmed by parasitologists.
Kirschner et al reported a case of conjunctivitis caused by Thelazia californiensis and a fly was believed to have been the possible mode of transmission in the Sierra Mountain foothills of California.5 Mimori et alreported Thelazia callipaeda infection in a man in Kumamoto Prefecture, Japan, who resided in the mountains.6 The hospitals in which our patients were examined are located in a remote mountainous region of Shimane Prefecture in western Honshu. Patients lived in the suburbs in which the hospitals were located; the infections might have occurred in their places of residence.
In the case of the infection of the inpatient, the infection route is unclear. Some farms that raise beef cattle are located near the hospital, and it is possible that flies from these farms transported the parasite to the hospital.
The authors have no proprietary interest in any aspect of this report.