Human ocular thelaziasis: A case report from Manipur, India

This is a case report of asymptomatic human ocular thelaziasis that was discovered accidentally just before a planned cataract surgery. A 69-year-old farmer from a rural area presented to the outpatient department of Ophthalmology with diminished vision in both the eyes, which was diagnosed as bilateral cataract. On the day of operation of the right eye, after instillation of 4% lignocaine hydrochloride eyedrops, a small, motile, chalky white, translucent worm was removed from the conjunctiva. It was morphologically identified as a female Thelazia callipaeda (T. callipaeda).

Keywords: Human thelaziasis, Manipur, Oriental eyeworm

Thelazia callipaeda (T. callipaeda), also known as the “Oriental eyeworm”, was first described by Railliet and Henry in 1910. The first human case was reported from Peiping, China by Stucky in 1917, who extracted four worms from the eye of a coolie. ^[1] The two important species infecting the human eye are T. callipaeda and in rare cases, Thelazia californiensis (T. californiensis). T. callipaeda is found in China, India, Thailand, Korea, Japan, Russia, Northern Europe, and Southern Italy. ^[2] However, T. californiensis is exclusively prevalent in the Western United States. ^[2]

The conjunctival sac, lacrimal gland, and lacrimal duct of dogs, cats, cows, rabbits, badgers, deer, foxes, and monkeys may be infested by the adult worms. ^[3] Transmission occurs through nonbiting flies belonging to the Drosophilidae family, of the genera Amiota and Musca autumnalis, which act as intermediate hosts. They ingest the embryonated eggs when feeding on animal lacrimal secretions. The larvae develop in the body cavity of the flies and are eventually deposited in the conjunctival sac of the new host. Third stage larvae that are usually deposited in the eyes, molt twice from the third stage to the fourth stage and then from the fourth stage to the fifth stage or young adults in 3-6 weeks. Humans are considered accidental hosts. Human thelaziasis usually presents with mild conjunctival irritation, foreign body sensation, excessive lacrimation, follicular hypertrophy and less often hypersensitivity to light, ocular pain, corneal opacities, ectropion, and secondary bacterial infections.

A 69-year-old male Hindu farmer from a rural area of Manipur, India presented to the outpatient department of Ophthalmology on March 2, 2012, with dimness of vision in both the eyes (more dimness in the right eye than in the left eye) for 6 months, and occasional gritty sensation and watering of the right eye for about 1 month. There was no history of redness of the eyes, ocular pain, or ulcers. The personal hygiene of the patient was very poor and he was a chronic alcoholic. The patient had a pet dog. There was no history of contact with cats or cattle. The patient gave a past history of pulmonary tuberculosis, for which antitubercular drugs were taken for 6 months.

On examination, he was diagnosed with hypermature cataract in the right eye and grade 3 nuclear cataract in the left eye. There was no conjunctival congestion, and the cornea and pupils were normal. Vision was recorded as perception of light (PL) positive and projection of rays (PR) accurate in the right eye, and 1/60 in the left eye and 1/60 in the left eye. Fundus examination revealed no details due to dense cataract in the right eye and a dull foveal reflex in the left eye. The patient was advised cataract operation for both the eyes. Routine blood, blood sugar, and electrocardiogram (ECG) were normal but chest x-ray showed old pleural effusion. On March 22, 2012, cataract operation was carried out on the left eye and the first postoperative day was uneventful with vision of 6/12. On March 24, 2012, the right eye was planned for operation and after the instillation of 4% lignocaine hydrochloride eyedrops on the right eye, a white, motile, translucent, thread-like worm was observed crawling in the lower fornix of the conjunctiva. It was removed with sterile forceps, put in normal saline, and sent to the Microbiology department for identification, and finally preserved in 70% alcohol. However, operation proceeded following the application of antiseptics and the first postoperative day was uneventful with vision of 6/18; the patient was discharged and the patient has maintained satisfactory vision in the follow up visit.

Morphologically, the worm was thin, thread-like, white to creamy in color, and measured about 17 mm in length and 0.3 mm at its maximal width [Figure 1]. When examined in detail, microscopically, the anterior end was found to bear a pair of prominent cephalic extensions protruding forward and a rectangular buccal cavity with no teeth-like structures [Figure 2]. The esophagus was 0.6 mm in length and the esophago-intestinal junction was normal and distinct. The intestine was simple, tubular, and could be traced to the posterior end. The vulva was anterior to the esophago-intestinal junction and about 0.5 mm from the anterior end [Figure 3]. This differentiates T. callipaeda from T. californiensis as the latter’s vulval opening is posterior to the esophago-intestinal junction. Mature eggs were seen in the posterior half of the worm [Figure 5]. Transverse cuticular striations were seen on the whole body of the worm [Figure 5]. The posterior end was blunt and not curved with spicules [Figure 4]. The anal opening was distinct and located at about 0.4 mm from the caudal end. The number of cuticular striations could not be measured due to the lack of clear visibility. On the basis of these observations, the worm was identified as a female T. callipaeda.

Case reports of human thelaziasis have increased in several areas of Asia, predominantly in rural communities that have poor living and socioeconomic conditions; human thelaziasis mainly affects children and the elderly. Over 250 cases of T. callipaeda infestation in humans have been reported worldwide so far in the medical literature. ^[3] In India, the first case of T. callipaeda infection was reported from Salem, Tamil Nadu in 1948. ^[4] Subsequently, about eight cases were reported by various authors from Manipur, Assam, Himachal Pradesh, and Karnataka. ^{[5],[6],[7],[8],[9]}

Most of the cases reported from China, Japan, India, Russia, Thailand, and Korea, including the present case, were extraocular. However, Zakir et al. documented intraocular thelaziasis of the vitreous. ^[10]

The present case is documented because the nematode was isolated from an apparently asymptomatic individual before the start of cataract surgery, although Mahanta et al. reported a similar case from Assam where they discovered the worms during the cataract operation. This is the third documented case from Manipur, India; the patient had most likely acquired the infection from the dog and his poor hygiene may have been the predisposing factor. ^[5]

The occurrence of Thelazia infestation in Manipur as well as the whole of Northeast India might be more than what is present in the record, and may be underreported. The reasons for these are that the patients do not seek medical treatment in most of the occasions as spontaneous exit of the worms usually cures the disease, and the lack of awareness of the problem among the medical fraternity.

Source of Support: None, Conflict of Interest: None

[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]