Myiasis is a disease caused by the invasion and colonization of human tissues and organs by the larvae of flies. This is manifested by the formation of necrotic tissue in the lesion, the colonization of fly eggs and the spread of fly larvae. This disease is mostly found in areas with poor sanitary conditions. Poor wound care, necrotic tissue formation, reduced immunity, and frequent contact with flies are risk factors for this disease. Myiasis can be divided into obligate and facultative parasitism,^[1] while some scholars have classified myiasis according to its location.^[2] In addition, some cases of myiasis are secondary to wound infection or poor surgical maintenance.^[3,4]

The clinical manifestations and treatment plan for myiasis vary significantly. The treatment principles include debridement of the lesion, infection control, treatment of the primary disease, and promotion of wound healing.^[2] This study reports a case of myiasis secondary to a right neck suppurative lesion admitted to Sun Yat-sen Memorial Hospital, Sun Yat-sen University, in November 2022 and discusses the diagnosis and treatment of the disease.

A 59-year-old female patient with a history of nasopharyngeal carcinoma was treated with radiotherapy. Initially, there was no obvious cause of suppuration in the right neck, which was approximately 1 cm × 1 cm in size; therefore, she was treated with antibiotics at the local hospital. One week later, the suppurative lesion was reduced with pruritus, and no further review or treatment was performed. Three months later, the wound was wiped, and the skin had ruptured with bleeding. The surface defect size was approximately 2 cm × 2 cm, and maggots were found in the wound. She was diagnosed with myiasis and admitted to Sun Yat-sen Memorial Hospital. Physical examination on admission showed that the lesion on the right neck had expanded to 6 cm × 4 cm and was accompanied by dark brown necrotic tissue and more than ten white maggots, with a small amount of blood oozing.

In the initial treatment, the exposed maggots were removed individually by forceps. The wound was flushed with hydrogen peroxide and iodine complex and then covered with Vaseline gauze to create an anaerobic environment to reduce the residual number of maggots. The infection was controlled by intravenous infusion of piperacillin and tazobactam sodium. After 3 d of debridement and infection control, the necrotic tissue and maggots of the lesion were effectively controlled (Figure 1A and B).

After debridement, the lesion was resected to normal tissue around the wound margin, protecting the neck blood vessels. After complete resection, the area was cleaned by alternating irrigation with iodine complex and normal saline (Figure 1C and D). The live maggots were collected and sent to the Pathogen Biology Diagnosis Centre of Zhongshan School of Medicine, Sun Yat-sen University, for species identification. The fly species was identified as Chrysomya bezziana based on the morphological characteristics and the amplified cytochrome c oxidase I (COI) gene sequences from the collected larvae (supplementary Figure 1).

After complete debridement, the size of the right pectoralis major myocutaneous flap was determined according to the defect area in the right neck. The tissue size of the skin flap must meet the needs of protecting the blood vessels of the neck, and it is also necessary to avoid excessive tissue size and swelling of the skin flap that would compress the operative area. The prepared right pectoralis major myocutaneous flap was transferred to cover the neck defect. After the flap was prepared and the defect in the operative area was repaired, the blood supply through the flap was repeatedly confirmed to be normal, the donor area was locally drawn and sutured, and a negative-pressure drainage tube was placed under the skin (Figure 1E and F).

After the repair, the subcutaneous effusion fluid was fully drained, especially to ensure smooth drainage around the vascular pedicle, to avoid effusion pressing on the vascular pedicle and affecting the blood supply to the flap. The negative-pressure drainage tube was removed on the third day after the operation, pressure was applied with a bandage to eliminate the dead space, and oral albendazole was used to strengthen the treatment. No serious complications or adverse reactions occurred, the flap survived, the wound healed well, and the patient was discharged 12 d after surgery. Three and six months after surgery, the infection remained controlled without recurrence, the flap survived, and no surgical trauma or donor complications were observed (Figure 1G and H). From an aesthetic point of view, the patient and her family were very satisfied.

Treatment of myiasis requires thorough debridement and promotion of wound healing. Blind debridement and the use of stimulant drugs may irritate maggots, aggravate their activity, invade deep tissues, destroy blood vessels, and even endanger life. Before surgical resection of the right neck lesion, a balloon occlusion test^[5] was performed to ensure that the internal carotid artery could be clamped without affecting the blood supply to the brain, and the test results were subsequently confirmed.

The base of the lesion was close to the internal jugular vein and the common carotid artery, which caused great trouble in the repair of the defect. In the reconstruction of head and neck defects, surgeons often use free flaps or pedicled flaps to repair large soft-tissue defects.^[6] Considering that the right neck defect was adjacent to a vital neck blood vessel and given the destruction of all of the defects by radiotherapy,^[7] it was better to use a pedicled flap for repair without vascular anastomosis.

The pedicled flaps that can be used for the repair and reconstruction of neck defects include a supraclavicular artery island flap, a latissimus dorsi flap, a trapezius flap and a pectoralis major flap. The blood supply of a supraclavicular artery island flap is derived from the supraclavicular artery.^[8] Relevant contraindications for the use of a supraclavicular artery island flap include old age, malnutrition, history of cervical radiotherapy, and history of cervical lymph dissection.^[9] The body mass index (BMI) of the patient was less than 17, and the thickness of the supraclavicular artery island flap could not meet the needs of protecting the neck blood vessels; therefore, this reconstruction scheme was not chosen.

The latissimus dorsi flap is a common skin flap used in breast reconstruction. Its blood supply comes from the transverse and descending branches of the thoracic dorsal artery.^[10] The disadvantage of using a latissimus dorsi flap is that the patient position needs to be changed during the operation. Changing the patient position during the operation not only increases the difficulty of the operation but also increases the risk of spread; therefore, this approach is not the first choice for repair.

The blood supply of a trapezoidal myocutaneous flap is derived from the transverse carotid artery. The blood supply of the pectoralis major myocutaneous flap is derived from the acromial artery.^[11] In this patient, the size of the pectoralis major myocutaneous flap and the length of the flap vessel pedicled were more suitable for repairing the defect, and patient position changes were avoided during preparation of the flap, which also has the advantage of protecting the carotid artery during repair and reconstruction.^[12] Ultimately, the surgical team decided to use the pedicled pectoralis major myocutaneous flap as the reconstruction option.

For the treatment of myiasis, good results can be achieved through debridement, infection control and wound healing. For critical patients, early intervention should be used to avoid serious complications. For the repair of intraoperative defects, an optimal repair plan and alternative plan should be developed after comprehensive consideration according to the defect condition and the general status of the patient. Preoperative evaluation and postoperative care also play crucial roles in determining the treatment efficacy.

Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethical approval: The manuscript was approved by the Medical Ethics Committee of Sun Yat-sen Memorial Hospital, Sun Yat-sen University.

Conflicts of interests: We have no competing interests to declare.

Contributiors: YKC and YLH performed the examination of the patient and wrote the manuscript. ZFY analyzed and interpreted the patient data regarding myiasis.The morphological characteristics and cytochrome c oxidase I (COI) gene-based molecular identification of Chrysomya bezzinma was performed by QF and DZ. All the authors read and approved the final manuscript.

All the supplementary files in this paper are available at http://wjem.com.cn.