Thelaziasis in an urban woman in Beijing: a case report and literature review (2025)

Background

Thelaziasis is a zoonotic disease mainly caused by Thelazia callipaeda (Spirurida, Thelaziidae, Thelazia), which can cause mild to severe signs and lesions, such as foreign body sensation, itching, tearing, eye pain, conjunctival bleeding, conjunctivitis, corneal ulcers, and even blindness. Thelaziasis cases have been reported mainly in agricultural areas and areas with high potential for contact with domestic animals [1].

Case presentation

We report a case of Thelazia callipaeda infection in the right eye of a 41-year-old woman working in an office. The patient presented with persistent foreign body sensation, pruritus, and redness despite initial treatment with polyethylene glycol and levofloxacin eye drops. Subsequent examination revealed the presence of multiple Thelazia callipaeda worms, which were successfully removed. Postoperative treatment with gatifloxacin eye ointment resulted in significant symptom relief with no recurrence over two months.

Conclusions

This case highlights the thelaziasis in urban settings, emphasizing the need for ophthalmologists to consider parasitic infections in differential diagnosis even in well-maintained environments. Then, we provided an overview of human thelaziasis in China by mining publicly available databases from 2014 to 2023, suggesting a difference in regional distribution that warrants further epidemiological studies.

In July 2022, a 41-year-old woman presented to the Peking University Third Hospital with complaints of a foreign body sensation in her right eye. Initial slit-lamp examination revealed corneal epithelial damage without any visible foreign body in the conjunctival sac (Fig.1A). The patient was prescribed polyethylene glycol eye drops (Siran) to be administered one drop four times daily, and levofloxacin eye drops (Cravit) to be administered one drop three times daily.

Despite medication, the patient’s symptoms persisted. She returned to the hospital in August, reporting itching, redness, and foreign body sensation in her right eye for one month. The patient resided in central Beijing and owned an American Shorthair cat. She also had a history of seasonal allergies and hyperthyroidism.

Upon re-examination, severe congestion and significant papillary hyperplasia of the upper palpebral conjunctiva with pseudomembrane were noted in the right eye (Fig.1B; Video 1). An eyelid retractor was used to expose the superior conjunctival sac fully. Four white linear worms were observed in the nasal and temporal sides of the conjunctival sac and were removed with forceps under topical anesthesia (Fig.1C; Video 2). The worms were very active in physiological saline (Video 3). Conjunctival smear test showed massive eosinophils and neutrophils (Fig.1D).

The worms were sent for laboratory examination. The entire worm demonstrated the typical slender and elongated body shape (Fig.1Ea). The anterior end of the worm displayed a buccal capsule, a distinctive feature of Thelazia callipaeda (Fig.1Eb). The posterior end showed well-defined cuticular striations and the presence of spicules, indicative of a male Thelazia callipaeda (Fig.1Ec). Genetic testing confirmed the infection as Thelazia callipaeda, with high similarity to known sequences in the GenBank database (query cover: 98%, max score: 1288) (Related files 1).

The patient underwent conjunctival sac rinsing to ensure no worms remained. Aqueous humor flash in the right eye was negative (Fig.1F).

The patient’s medical history was reviewed after identifying the worms. She could not recall recent exposure to flying insects but noted her cat had an eye disease. Pathological examination of the cat was not performed as the patient refused.

Post-surgery, GatifloxacinEyeGel(Diyou) was administered one drop four times daily. One week later, the patient’s symptoms were significantly relieved, and no recurrence was reported over the following two months.

Thelaziasis is a zoonotic disease mainly caused by Thelazia callipaeda (Spirurida, Thelaziidae, Thelazia), transmitted by Drosophilid flies of the genus Phortica as the vector. The ultimate hosts of T. callipaeda can be domestic carnivores(dogs and cats), wild carnivores(foxes and wolves), rabbits, and humans [2]. The adult stage is parasitic in the eyes of the definitive host, mostly in the eyelid and under the palpebral membrane, and in the conjunctival sac, rarely entering the subconjunctival. Thelaziasis can cause mild to severe signs and lesions, such as foreign body sensation, itching, tearing, eye pain, conjunctival bleeding, conjunctivitis, corneal ulcers, and even blindness [2]. In addition, the host infected with Thelazia callipaeda is easy to be complicated by bacterial infections such as Pasteurella, Chlamydia, Staphylococcus , and so on, leading to the aggravation of the host’s symptoms [3]. Due to the weak tendency of infants’ chief complaints, it was easy to be missed when infants were infected. Moreover, infants often rub their eyes with their hands, which is very easy to cause secondary bacterial infection [4], leading to aggravation of the patient’s symptoms.

Among over 16 species of the genus Thelazia (Spirurida, Thelaziidae), only Thelazia callipaeda (T. callipaeda, Railiet and Henry, 1910 [5]), Thelazia californiensis (T. californiensis, Price, 1930 [6]), and Thelazia gulosa have been found to affect humans [7, 8]. Thelazia callipaeda is also known as “the oriental eyeworm” because of its original distribution in the former Soviet Union and East Asia [9], while T. californiensis [10]and T. gullosa [8] are mainly distributed in North America. In recent years, thelaziasis has also been reported in Eastern and Southern Europe [2, 11,12,13]. Thelaziasis cases have been reported mainly in agricultural areas and areas with high potential for contact with domestic animals [1]. Thelazia is transmitted by Phortica okadai in Asia and P.variegate in Europe [14].

In the life cycle of Thelazia callipaeda, ovoviviparous adults live in the conjunctival sac of the definitive host and release first-stage larvae (L1) wrapped in a sheath [15]. L1 larvae are ingested by the Drosophilid flies of the genus Phortica intermediate host during feeding on tears and lacrimal secretions image. In the digestive tract of the intermediate host, L1 larvae emerge from the sheath, invade various host tissues, and then molt twice to become infective L3 larvae. Fully developed L3 larvae break out of the capsules and migrate to the mouthparts of Drosophilid flies of the genus Phortica, where they remain until the Drosophila feeds on the lacrimal gland secretions of the definitive host [8, 16, 17].

China is the country with the largest number of thelaziasis cases in the world [18]. In China, since the first human cases of Thelaziasis were identified in Beijing and Fujian in 1917, to 2018, a total of 653 cases were reported. This article reviews and summarizes the reported thelaziasis in China in the past ten years (2014–2023).

We searched the PubMed, Web of Science, and Wanfang databases. Relevant articles or book chapters in all languages were reviewed. The search terms included were { (Thelazia callipaeda) OR (thelaziosis) OR (thelaziasis) OR (thelazi)} in English and { (Jiemoxishunxianchong) OR (dongfangyanchong) } in Chinese, respectively.

Between 2014 and 2023, 86 cases of human conjunctival thelaziasis were reported in China (Fig.2; Table1). The provinces with the highest number of cases were Guizhou (n = 15) and Henan (n = 15), followed by Shandong (n = 9), Sichuan (n = 7), and Hubei (n = 6). Epidemiological investigations revealed that patients’ ages ranged from 5 months to 85 years. Among the 73 cases with specified gender, 43 were male (58.9%) and 30 were female (41.1%). Of the 76 cases with reported ages, 16.9% (13 cases) were children under 6 years old, 2.67% (2 cases) were children aged 7–18 years, 32.0% (24 cases) were adults aged 18–60 years, and 22.7% (17 cases) were elderly over 60 years old. Among the 56 described cases of eye infection, 91.1% (51 cases) were unilateral. Symptoms included foreign body sensation in 38 patients and itching in 13 patients. Of the 38 patients with detailed residential information, 13 (34.2%) lived in urban areas and 25 (65.8%) lived in rural areas. Additionally, 16 patients explicitly recalled a history of fly contact. Among the 45 patients who reported their animal husbandry status, 27 (60%) raised animals, with 16 keeping dogs, 1 keeping a cat, 8 keeping both dogs and cats, 1 keeping cattle, and 1 keeping other animals.

The data of our review indicated that the disease predominantly affects males and rural residents, with a significant proportion of patients having a history of animal husbandry and fly exposure. Managing and controlling infections caused by Thelazia callipaeda requires a comprehensive approach. Key measures include enhancing public health education to raise awareness of transmission vectors, such as Drosophilid flies, and promoting hygiene practices. Besides, regular veterinary check-ups, especially in urban areas, can facilitate early detection and treatment of infections in pets, thereby reducing the risk of human transmission. Furthermore, environmental controls, including effective waste management and the use of insect repellents, are essential for curbing fly populations and subsequently decreasing the incidence of thelaziasis. Community engagement is crucial for sustaining these preventive measures. Alongside timely diagnosis and treatment, these strategies constitute an effective response to this zoonotic threat{Ren, 2017 #845}{Zheng, 2020 #846}{Zhao, 2017 #848}{Cheung, 2021 #879}. As to ophthalmologists, when urban residents visit the Department of ophthalmology with the chief complaint of eye itching and foreign body sensation, ophthalmologists cannot ignore the possibility of Thelazia callipaeda infection. It is necessary to carefully ask the patient’s allergy history, pet raising history, living environmental hygiene status, and eye flying insect contact history. At the same time, the patient’s eyes should be carefully examined under the slit lamp to avoid missed diagnosis and misdiagnosis.

Author notes

1. Shumei Tan and Pei Zhang were co-first Authors.

Authors and Affiliations

1. Department of Ophthalmology, Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Peking University Third Hospital, No 49 North Garden Road, Haidian District, Beijing, 100191, China

   Shumei Tan,Pei Zhang,Yingyu Li,Ziyuan Liu&Xuemin Li

2. Peking University People’s Hospital, No.11 Xizhimen South Street, Xicheng District, Beijing, 100044, China

   Fanshu Li

Contributions

Shumei Tan was responsible for the main writing of the article, Pei Zhang provided the results of morphologic and genetic testing, Fanshu Li and Yingyu Li were responsible for the writing and picture production of the article, Ziyuan Liu provided clinical records, and Xuemin Li guided the article.

Corresponding authors

Correspondence to Ziyuan Liu or Xuemin Li.

Ethics approval and consent to participate

The study protocol was established, according to the ethical guidelines of the Helsinki Declaration and was approved by the Human Ethics Committee of Peking University Third Hospital (approval number: S2024042). Written informed consent was obtained from the patient for the publication of this case report.

Consent for publication

Written informed consent was obtained from the patient for the publication of this case report.

Competing interests

All authors declare that they have no conflicts of interest.

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