Orbital myiasis

Yan-Ling Huang, MD,a Lu Liu, MD,c Hao Liang, MD,a Jian He, MD,a Jun Chen, MD,a Qiao-Wen Liang, MD,a Zhi-Yuan Jiang, MD,b Jian-Feng He, MD,a,∗ Min-Li Huang, MD,a,∗ and Yi Du, MDa,∗
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1. Introduction

Maggots are larvae of Diptera flies, most of which are mainly found in human and animal feces, garbage, decaying plants and animal carcasses and feed on feces and decaying organic matter. In cases of accidents or in certain specific species, they can infest vertebrate animals, including humans, and feed on living or dead tissue, as well as on body fluids,[1] leading to myiasis. Myiasis mainly occurs in animals such as cattle, goats and pigs but occasionally occurs in humans.[2] Advanced age, disease-ridden status, poor self-care, poor hygiene, and rural background are reported risk factors for human myiasis. A pastoral or rural background provides the conditions for the prevalence of myiasis because it is a zoonotic disease. Myiasis is mainly prevalent in tropical and subtropical regions, where a warm and humid climate prevails almost throughout the year,[1] or in developing countries with a large population density and poor sanitation.

Ophthalmomyiasis can involve the eye, orbit, and periorbital tissues. It is classified as external, internal or orbital in accordance with the site of the larvae infestation.[3] Limited superficial infestation of external ocular tissues such as the palpebra and conjunctiva is called external ophthalmomyiasis. When the larvae invade deeply and migrate into the subretinal space, internal ophthalmomyiasis occurs. Orbital myiasis is a more extensive infestation involving orbital tissue and is the most serious form. Once established, orbital myiasis progresses rapidly and can completely destroy the orbital tissues within days.[4] Fortunately, it is the least common form,[5] with only a few cases reported. Management of orbital myiasis ranges from simple manual removal of the maggots to destructive surgeries of the globe and orbit.[6]

Medical professionals are unfamiliar with orbital myiasis because it is such a rare disease, which may increase the difficulty of recognition and treatment. Here, we report a case of orbital myiasis and conduct a systematic literature review of cases previously reported in the literature, aiming to better outline the clinical features and therapeutic management of orbital myiasis. The patient himself consented to the publication of the study. This case report was approved by the ethics review committee of First Affiliated Hospital of Guangxi Medical University, (2019-KY-E-036), Nanning, China, and an informed consent form was signed by the patient himself.

2. Case report

A 72-year-old male patient presented to the emergency department on October 31, 2015, with a complaint of repeated pain for two years after trauma to his right eyelid and a 2-day history of symptoms aggravated by the wriggling out of larvae. The patient reported that his right upper lid had been injured by cane leaves 2 years prior, but no treatment was received. Then, he experienced repeated pain in his right eye, accompanied by gradually decreased vision until it was completely lost 1 year previously. His painful symptoms worsened 2 days before presentation, with bleeding, a crawling sensation and larvae wriggling out (Fig. ​(Fig.1).1). He denied a history of alcoholism, previous ocular surgery, or prolonged use of medications.

Orbital myiasis
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Figure 1
A color photograph demonstrating that the right orbit was destroyed and several larvae were wriggling out.

On ophthalmic examination, the visual acuity test revealed no light perception in his right eye. His right periorbital skin was red and edematous, and the eyelid was thickened. There was a large eyelid wound of approximately 4 cm ∗ 1 cm filled with numerous white larvae, some of which were crawling out. No abnormalities were found in the left eye or upon systemic examination. A computed tomography scan revealed that the right eyeball protruded and that the soft tissues around it were swollen (Fig. ​(Fig 2). Two days later, magnetic resonance imaging showed that the shape of the right eyeball was changed and that the normal structure of the eyeball could not be identified (Fig. ​2). A diagnosis of orbital myiasis was made.

Figure 2
(A and B) An orbital computed tomography scan showed that right eyeball protrusion and periocular soft tissue edema. Two days later, (C) magnetic resonance imaging showed that the shape of the right eyeball was changed and the normal structure of the eyeball could not be identified.

Considering potential infections, the patient received topical levofloxacin eye drops, intravenous ceftazidime and levofloxacin, and a tetanus antitoxin injection. In view of imaging evidence of total destruction of the globe caused by infiltration of the larvae, exenteration of the right orbit was performed in the patient. All necrotic tissues and nearly 100 larvae were removed. Then, the wound was closely observed for infections and possibly missed larvae. Within three days after surgery, there were still 3 larvae crawling out of the orbit. On the ninth postoperative day, the defect was repaired via reconstruction with a pedicled musculocutaneous flap from the forehead region (Fig. ​(Fig.3).3). The patient recovered well postoperatively and was discharged uneventfully. During the 6-month follow-up period, the wound healed well, and the patient had no further complaints. Subsequently, he was lost to follow-up.

Figure 3
The second week after orbit exenteration and frontal flap reconstruction.

The histopathological examination of the orbital contents revealed hyperplastic inflammatory granulation tissue, large areas of necrotic tissue and acute inflammatory exudates. The larvae were identified as the larvae of Lucilia sericata (Diptera: Calliphoridae) (Fig. ​(Fig.4A and B).