|Year : 2022 | Volume
| Issue : 1 | Page : 9-12
Myiasis and extremity involvement: A concise update
Tariq Akhtar Ansari, Ganesh Singh Dharmshaktu
Department of Orthopaedics, Government Medical College, Haldwani, Uttarakhand, India
|Date of Submission||26-Jul-2021|
|Date of Decision||30-Aug-2021|
|Date of Acceptance||22-Sep-2021|
|Date of Web Publication||25-Feb-2022|
Ganesh Singh Dharmshaktu
Department of Orthopaedics, Government Medical College, Haldwani - 263 139, Uttarakhand
Source of Support: None, Conflict of Interest: None
The human myiasis or infestation of larvae of various species of fly bots is uncommon but interesting health challenge in some parts of the world. The basic knowledge of this disease, however, should be beneficial to clinicians across disciplines as a spectrum of manifestations involving various organs are described in the medical literature. The extremity involvement is rather uncommon and is often found with underlying associated conditions. The diagnosis and identification of the causative species is important for documentation and management. Clinical suspicion, wound lavage, dressing, and debridement are important steps in optimal management. Appropriate systemic pharmacotherapy is supplemented for quick recovery. Prevention, however, coupled with avoidance of predisposing factors is the best management in both community and health-care settings. As the disease is more commonly noted in lower socioeconomic conditions and rural settings, the working knowledge of this condition should come in handy in anticipating, suspecting, and thus diagnosing the condition early for a prompt recovery.
Keywords: Human botfly, human infestation, larvae, maggot, myiasis
|How to cite this article:|
Ansari TA, Dharmshaktu GS. Myiasis and extremity involvement: A concise update. J Surg Spec Rural Pract 2022;3:9-12
|How to cite this URL:|
Ansari TA, Dharmshaktu GS. Myiasis and extremity involvement: A concise update. J Surg Spec Rural Pract [serial online] 2022 [cited 2023 Mar 31];3:9-12. Available from: http://www.jssrp.org/text.asp?2022/3/1/9/338529
| Introduction|| |
Human myiasis (Greek Mya = fly) is an infestation of fly larvae (maggot) that deposit eggs into living mammals or warm-blooded vertebrates and complete their life cycle. The typical hosts are mammals, birds, and accidentally men. Various fly species, anatomical location, and burden of fly larvae have bearing on their myriad clinical presentation. Dermatobia hominis is the primary human bot fly. This fly is restricted to tropical America from Mexico to northern Argentina. Cochliomyia hominivorax and Chrysomya bezziana are primary screwworms noted in the New World and Old World, respectively. Flies that are animal parasites, with an occasional human infestation, are from genera Cuterebra, Oestrus, and Wohlfahrtia. While more common D. hominis lay eggs in the bodies of blood-sucking arthropod-like mosquitoes to complete their life cycle. Species such as Cochliomyia, Cuterebra, and Wohlfahrtia have more direct life cycles and these can lay eggs directly or in the vicinity of wound. In species such as Cochliomyia the larvae stay for a longer time within host tissues and may spread to other tissue by subdermal spread. In this review, articles from the year 2000 onward in English medical literature are included for important takeaways. The disease limited to extremity involvement is included and articles describing those involving other anatomical regions are excluded. Articles describing the therapeutic role of maggots have also been excluded. The authors do not claim to include all articles and similar or less relevant articles may have been omitted to make this a crisp and short review.
| Skin Involvement|| |
The skin is a common site of myiasis and these cutaneous myiases usually present as furuncle, localized inflammation, skin wounds, and myiasis linearis (or larva migrans) among others. The predisposing factors to increased incidence have been described and are listed in [Table 1]. Furuncle-like lesion in the exposed parts, following a period of stay at endemic areas and history of mosquito bite, may be suspected with this condition. The usual feature of skin problem is 2–3 cm wound, mildly tender and pruritic. The skin lesion may or may not be associated with broken skin with serous or serosanguinous discharge.
| Diabetes and the Risk|| |
Diabetes is an important comorbidity associated with human myiasis. The common presentation in diabetics is skin involvement with a wound infested with larvae of various fly species. Common among them are Cochliomyia hominivorax, Chrysomya bezziana, Phormia regina, Sarcophagi, Calliphora, Lucilia sericata, and Stomoxys. Neglected and mismanaged wounds provide favorable conditions to develop wound myiasis. In one large series of 18 cases of myiasis in diabetic foot, most cases had necrotic tissue and all cases had additional bacterial infection superimposed with myiasis. Myiasis was commonly encountered from May to July season. The most common agent identified was L. sericata. All cases underwent larval debridement therapy and wound care, but most cases require one or other forms of surgical intervention. The associated diabetic neuropathy, which is common in the settings of diabetic foot infection, might be the reason that little or no pain is perceived by the patient. The risk of infestation also increased in cases who are bedridden or are paralyzed.
In a report from the Saudi Arabia region, myiasis was confirmed when a larva was removed from a wound in the back of shoulder region. A third-stage larva of Sarcophaga species was diagnosed on microscopic examination. Calliphoridae species was found in a another case in diabetic foot infection with wound. In a study of 42 cases with preexisting wounds and myiasis, old age, male sex, homelessness, and alcoholism were frequent cofactors. The most common species noted was Phaenicia sericata (green blowfly), whereas humpback and flesh fly were noted in other cases. One case with diabetes with drainage and malodorous discharge from a toe wound, previously treated for tinea pedis, was found to be infested with visible larva. Whirlpool debridement and proper wound dressing resulted in clinical improvement. Associated infection with Gram-negative bacteria was also associated in the same case. In a series of three elderly cases, including two diabetics and one with hypertension and hemiplegia, third-stage larvae of Sarcophaga haemorrhoidalisin two and that of P. regina in one case were identified. These cases highlight complex nature of disease in the setting of underlying diabetes mellitus.
| Nosocomial Infestation|| |
Report of nosocomial myiasis in a case with multiple trauma, following motor vehicle accident, was reported with Sarcophaga cruenta (Meigen 1826) as the culprit agent. Another case of parasitosis by Sarcophaga (Bercaea) Africa species in the heel of a patient with associated diabetes was reported as nosocomial myiasis. Prevention of health-care-associated myisais can be ensured by two methods-minimizing patient risk factors and reduction of fly population in the surrounding environment. Once an infestation is reported, quick, multidisciplinary action, preservation of maggot, and circumstance leading to infestation should be investigated. Good communication with patients and relatives is another key step to allay apprehension and form the basis of informed and shared decision-making process.
| Nondiabetic Situation|| |
In a recent report, severe sporadic pain in the right second toe in a lady who recently returned from Panama holiday tour resulted in a nonhealing ulcer puncture type wounds on the plantar aspect with serous discharge. Surgical exploration revealed a large parasite infestation finally identified as D. hominis larvae (botfly) A case report with a history of travel to Belize and history of bitten by some insects was later found infested with as botfly larvae D. hominis. Bite over posterolateral aspect of right forearm led to itching and circular erythematous lesion with necrotic center with resultant skin breakdown in later course of disease. Central punctum with a visible tip of the larva was seen and a single larva was removed. The nondiabetics may also get wound myiasis of extremities that is not fatal but have varied morbidity. Four cases of Chrysomya beziana infestation in foot and leg involvement were reported in a small series. Other bacterial co-infections were also reported in all cases. Another case of an obligatory myiasis of leg with C. bezziana as a causative agent in a diabetic female was reported which was then managed by the use of turpentine oil to evacuate many larvae due to asphyxiation and thus required no use of forceps. A report of two cases, one diabetic with venous stasis ulcer and one nondiabetic with leg wound, revealed Phorid larvae infestation with Megaselia scalaris. Better identification of species is instrumental to report and record the pattern of myiasis in a particular geographic region.
| Pin Site Myiasis|| |
Myiasis by direct invasion of larvae in wounds adjacent to pin site of external fixator is one of the growing concerns as reported sporadically. A case of pin site infestation in a case of open femur fracture managed with an external fixator was described to be finally found to harbor C. hominivorax screwworm as causing agent. Edema, redness, and warmth were complained by the patient surrounding the areas of external fixator pins. Surgical cleaning and oral ivermectin along with intravenous ampicillin/sulbactam were initiated. Later, development of osteomyelitis developed with Pseudomonas aeruginosa and Stenotrophomonas maltophilia which were susceptible to trimethoprim/sulfamethoxazole. Involvement with the similar agent was reported in another case highlighting a cautious approach in excluding myiasis in selected pin-tract infection cases. Halo pins for cervical fracture infested with myiasis in two separate cases were managed by removal of pins and debridement to highlight an uncommon presentation., Tibia pins with small infected wounds adjacent to distal pins might have favored localized myiasis in an another case managed by complete removal of maggots and systemic antimicrobial therapy. Another case of pin site myiasis was reported along with associated risk factors such as diabetes, poor hygiene, and immobilization. Frequent reporting of such cases in the literature calls for proper documentation and studies in this context in the future.
| Associated Conditions|| |
An interesting case was noted with previous history of rheumatological disease and presenting with accompanying ear pain following history of a fly bite. Ear drainage was done to evacuate multiple larvae. In the follow-up, temporomandibular joint pain, swelling, and also pain in the same side ankle and right knee were noted. The HLAb27 was positive with normal sacroiliac joint in this case and the short course of prednisolone improved the symptoms. The authors postulated that either myiasis or associated undocumented bacterial co-infection may be the reason behind this. Myiasis of left foot and leg in a different case with chronic lymphedema and ulcer has also been reported. Inappropriate management by the primary practitioner and failure to debride well resulted in a progressive, painful necrotizing infection of lower extremity. L. sericata was probable larvae and underlying Providencia and other bacterial causes for sepsis were also identified. Regular dressing, scrubbing, pulse lavage, and broad-spectrum antibiotic coverage led to avoidance of amputation. One case of bilateral lower extremity multiple necrotic wounds with preexisting severe uncontrolled schizophrenia was dressed to healing with povidone–iodine along with a regimen of oral ivermectin to treat concomitant body lice. A proper listing of associated conditions may help outline high-risk groups in clinical settings for a vigilant observation.
| Treatment|| |
The most important treatment of myiasis is prevention. Care of wound and protection of the limb is crucial. Manual removal of all visible larvae and screwworms from the wound and regular debridement and dressing is required in most cases. In rare instances, surgical incisions can be used judiciously for removal of larvae or excision of devitalized tissue. It can also be used to reach hidden larvae within the wound. No specific medication is described for myiasis., Extraction of complete larva is crucial for successful management. Suffocation, beeswax, and petroleum jelly have been tried, but they neutralize the agent but do not extract larva. Careful removal with not rupturing the larva should be the aim with judicious use of tweezers, forceps, or venom extractors as adjunct tools. Laceration of larvae during surgical exploration should be checked and prevented so that the risk of inflammatory reaction, bacterial infection, or granuloma formation is minimized. It has to be supported by appropriate systemic antimicrobial therapy. Injection of lidocaine in the base of tissue cavity for inhabiting larvae may be another technique in selected cases. Ether was used as a safe, novel, and noninvasive method to extract wild maggots and larvae from wound myiasis. Manual removal of all visible larvae and regular dressing is the mainstay of extremity myiasis wound management. Finally, prevention of associated risk factors and better hygiene can go long way in preventing this nagging problem.
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Conflicts of interest
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