External ophthalmomyiasis caused by Dermatobia hominis. A retrospective study of nine cases and a review of the literature

Bilateral Ophthalmomyiasis Externa of Lid by Musca domestica: A Rare Presentation

A case of severe blepharoconjunctivitis in the last three weeks diagnosed the slit lamp as external ophthalmomyiasis. On ocular examination, numerous pupae were present on the lid margins, firmly adhering to the lid lashes bilaterally. All of them were removed mechanically under topical anesthesia. They were 67 in number. Healing occurred without any complications. In such cases of blepharoconjunctivitis, physicians should consider the possibility of ophthalmomyiasis externa, especially in places where high numbers of livestock are found. Otherwise, there is a chance of missing the diagnosis, which can be met with a more serious condition called ophthalmomyiasis interna.

First record of Psorophora ferox (Diptera: Culicidae) infested with eggs of Dermatobia hominis (Diptera: Cuterebridae), in Ucayali: Peru

INTRODUCTION

Dermatobia hominis belongs to the Cuterebridae family, Diptera order; These flies inhabit tropical regions where they are called "fly of death" since the larvae are capable of causing lesions in domestic animals, wild animals including humans, the adult females of D. hominis capture other dipteran to oviposit their eggs on them (phoresis), when hematophagous mosquitoes land on an animal and / or human in order to feed on their blood, the eggs hatch and the larvae immediately penetrate the skin where they will develop to later abandon the host, then in the soil and / or other moist substrate the pupal stage develops, finally new adult flies will emerge from the pupae.

OBJECTIVE

The primary goal of the present study was to determine as first record, the presence of Psorophora ferox infested with eggs of Dermatobia hominis, Peru.

METHODOLOGY

The present study was carried out in an area of the private reserve "El Vencedor", located within the city of Pucallpa, Ucayali Region-Perú. The area is characterized by being humid tropical, with an average temperature of 26ºC and humidity of 92%, while the annual precipitation is approximately 1570 mm3. The capture method was carried out with the help of a hand net type "butterfly" or also called Jama.

RESULTS

A total of 668 mosquitoes of different species were collected, the most abundant being Psorophora albigenu and Psorophora ferox, which represented 88.72% and the least abundant was Culex coronator and Uranotaenia apicalis with 0.15% of the total sample collected.

CONCLUSIONS

Within these specimens it was captured a mosquito of the species Ps. ferox with the presence of 8 eggs of D. hominis, of which 3 would have hatched, while in the remaining 5, the larvae would remain inside the eggs.

Ophthalmomyiasis Externa and Importance of Risk Factors, Clinical Manifestations, and Diagnosis: Review of the Medical Literature

OBJECTIVE

This review aims to describe and compare the risk factors, clinical course, diagnosis, and parasitologic features of external ophthalmomyiasis. We also discuss the different preventive measures and the effect of global warming in a large case series reported from January 2000 to December 2022.

METHODS

We perform a literature review of reported cases of external ophthalmomyiasis to determine the clinical characteristics, therapeutic management, and information on the organisms that most commonly cause external ophthalmomyiasis.

RESULTS

A total of 312 cases of external ophthalmomyiasis were recorded. The most common causative organism was Oestrus ovis (Linnaeus) (Diptera: Oestridae), accounting for 72.1% of cases, followed by Dermatobia hominis (Linnaeus Jr. in Pallas, 1781) (Diptera: Oestridae) at 5.4%, Lucilia sericata (Meigen) (Diptera: Calliphoridae) at 0.96%, and Chrysomyia bezziana (Villeneuve) (Diptera: Calliphoridae) at 0.96%. Before experiencing symptoms, 43.6% of cases reported having direct contact with flies or being hit in the eye, 33% reported no associated risk factors, 9.3% reported living with sheep and goats, and 7.7% reported a history of foreign objects entering the eye. The most common symptoms for those affected by O. ovis were sudden onset, including a foreign body sensation and movement, redness, tearing, itching, swelling, irritation, photophobia, burning, and ocular secretion. In cases caused by D. hominis, symptoms included eyelid edema, pain, redness, itching, movement within the lesion, ocular irritation, and discharge. Regarding occupational or recreational activity, agriculture, and livestock had the highest incidence, followed by trades and technical activities, being a student, and having traveled to an endemic region for work or recreation.

CONCLUSION

Patients with red eyes may suffer from external ophthalmomyiasis, which requires a thorough examination to diagnose and treat it early. Moreover, as the temperature increases due to climate change, it is essential to consider how this will affect the spread of different pathogens.

Ophthalmomyiasis in a preterm neonate resulting in blindness: A case report from Botswana

Myiasis is an infestation of human tissue by insect larvae. While rare, healthcare-associated myiasis has been reported from immobilized patients in resource-limited healthcare facilities in warm climates without adequate vector control measures. We describe a case of Ophthalmomyiasis in a hospitalized neonate in Botswana that resulted in vision loss. The neonate, who was initially hospitalized due to the complications of prematurity, received phototherapy for jaundice, and to avoid phototherapy-related retinopathy, the neonate's eyes were covered using cotton gauze and adhesive tapes that potentially damaged the skin as commercially available eye covering was not in stock. Therefore, eye covering was not changed and when the eye covering was removed almost 3 days after placement, insect larvae were noted in the patient's eyes and nose. Ophthalmologic evaluation revealed perforated corneal ulcer and uveal prolapse in the right eye resulting in complete blindness and corneal scarring of the left eye. The patient's clinical course was further complicated by an Enterobacter species bloodstream infection. This case highlights the importance of vector control as a major patient safety measure for neonatal units in warm climates. Flies had been observed in the room and mitigation measures included reducing fly populations through traps, screens, and removal of standing water and leftover food. Every mother and staff were sanitizing hands when entering the room and gowns were used. This case also reinforces the importance to conduct vigilant monitoring of patients, especially neonates with eyes covered during phototherapy.

Orbital myiasis on recurrent undifferentiated carcinoma in the COVID-19 era: a case report and brief review of the literature

Background

Myiasis is defined as the infestation of living tissues by Diptera larvae. Ophthalmic involvement occurs in less than 5% of cases. As the most uncommon type of involvement, orbital myiasis usually affects patients with poor personal hygiene, a low socioeconomic status, a history of surgery, and cancer.

Findings

In January 2020, an 89-year-old man presented to the Oculoplastic Department of Farabi Eye Hospital (Iran) with a history of left-side progressive orbital mass for six months. A large infiltrative mass of the left orbit with extension to the globe, periorbita, and adnexa was remarkable at the presentation, and its appearance suggested malignancy. Our findings persuaded us to perform exenteration and histopathological evaluation which were reported as “undifferentiated carcinoma”. Regular follow-up visits were recommended. In June 2020, with a 3-month delay, the patient presented with the recurrence of the mass complicated with mobile alive larva. Examinations revealed numerous maggots crawling out of an ulcerative and foul-smelling lesion. He stated that fear of COVID-19 infection postponed his follow-up visit. The patient underwent immediate mechanical removal of larvae, followed by wide local excision of the mass.

Conclusion

Patients with carcinoma of the adnexal tissues seem to be more prone to myiasis infestation even though it is an uncommon disease. Since COVID-19 is an ongoing pandemic with no end in sight appropriate protocols should be implemented to prevent loss of follow-up in these high risk patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12348-021-00271-1.

In vitro larvicidal activity of ivermectin and povidone-iodine against Oestrus ovis

Purpose

To assess the in vitro larvicidal activity of ivermectin and povidone-iodine (PVP-I) against Oestrus ovis, the most frequent cause of external ophthalmomyiasis.

Methods

L1 O. ovis larvae were collected from the nasal boots of sheep slaughtered in local abattoirs and transferred onto Petri dishes containing mucosal tissue (25 larvae/dish). The larvicidal activity of the following formulations was tested: 1% ivermectin suspension in balanced sterile saline solution (BSSS), 1% ivermectin solution in propylene glycol, propylene glycol, 0.6% PVP-I in hyaluronic acid vehicle (IODIM®), and combination of ivermectin 1% solution and 0.6% PVP-I. One mL of each formulation was added to different Petri dishes containing the larvae. The time needed to kill the larvae was recorded.

Results

893 larvae were tested. The median time needed to kill the larvae was 46, 44, 11, 6, and 10 minutes for Iodim®, ivermectin 1% suspension, propylene glycol, ivermectin 1% solution, and a combination of ivermectin 1% solution with 0.6% PVP-I, respectively. Kaplan-Meyer analysis disclosed that the survival curves were significantly lower in samples treated with ivermectin 1% solution, ivermectin 1% solution + 0.6% PVP-I, and propylene glycol than in samples receiving other treatments or BSSS.

Conclusion

In this in vitro study, ivermectin 1% solution in propylene glycol, ivermectin 1% solution + 0.6% PVP-I, and propylene glycol alone showed a good, relatively rapid larvicidal activity against O. ovis larvae. Further experimental and clinical studies are necessary to establish whether, or not, these formulations may be considered as potential candidates for the topical treatment for external ophthalmomyiasis caused by O. ovis.

Dermatobiosis in Panthera onca: first description and multinomial logistic regression to estimate and predict parasitism in captured wild animals

Dermatobia hominis is a parasite widely distributed in neotropical regions. The parasitic phase of the cycle is characterized by the formation of a subcutaneous nodule in the host, which can promote infestation by other dipterans and skin infections. The aim of this report is to register parasitism by D. hominis in free-ranging Panthera onca captured in the Brazilian wetland and to determine significant biological and meteorological factors that are likely to influence the presence of larval parasitism in captured wild jaguars. Between 2011 to 2020, 34 jaguars were captured and examined manually by searching for lesions characteristic of myiasis. By manual compression in the subcutaneous nodules, larvae morphologically identified as D. hominis (first and third instars) were collected from 13 jaguars. A multinomial logistic regression showed that adult jaguars had 16.49-fold higher odds of being parasitized than subadults. Thus, jaguars captured in the season of July-September have 34.01- and 11.42-fold higher odds of being parasitized compared to the seasons of October-December and April-June, respectively, which is associated with high total monthly precipitation in the previous season. The present study is the first to describe parasitism by D. hominis larvae in jaguars.

The Botfly, A Tropical Menace: A Distinctive Myiasis Caused by Dermatobia hominis

Dermatobia hominis, also known as the human botfly, is native to tropical and subtropical Central and South America and seen in travelers from endemic to temperate regions including the United States and Europe. Cutaneous infestation botfly myiasis involves the development of D. hominis larvae in the skin and is common in tropical locations. The distinct appearance of a cutaneous D. hominis infestation facilitates early diagnosis and intervention where cases are common. However, the identification of D. hominis in temperate regions may prove challenging due to its rarity. D. hominis may be misdiagnosed as folliculitis, an epidermal cyst, or an embedded foreign object with secondary impetigo. One should have a heightened suspicion in someone returning from a vacation in an endemic area, such as Belize. Here we describe the presentation, differential diagnosis, and treatment and encourage enhanced preventative measures among tourists when visiting tropical and subtropical regions. Additionally, we propose a novel classification system for assessing the various stages of infestation and suggest that patients reporting travel to Latin America and experiencing pain disproportionate to an insect bite should lead physicians to consider myiasis caused by D. hominis.

Oral myiasis: Analysis of cases reported in the English literature from 1990 to 2020

Myiasis is an infection caused by the deposition of fly larvae in tissues, and its involvement in the human oral cavity is uncommon. Herein, we have performed a data analysis of published cases of oral myiasis. A search was performed in PubMed, Ovid, Web of Science, Scopus, and LILACS. Geographic distribution, demographic data, associated factors, clinical features, fly types, treatment, and presence of sequelae were analyzed. A total of 122 articles reported the cases of 157 infected individuals. The most affected countries were India (41%) and Brazil (29.5%). Male predominance (67.5%) and a mean of 41.9 years of age were observed. The gingiva (29%) was the most affected site, followed by palate (25%) and lip (21%). There were different forms and combinations of treatments: manual removal of larvae and surgical debridement, application of asphyxiating substances, antibiotic therapy, and use of ivermectin. The condition predominantly affects individuals with neurological and/or locomotor disabilities, of low socioeconomic status, with poor oral hygiene and chemical dependence and individuals with previous injuries or with the absence of lip sealing. The establishment of a standard treatment protocol, enabling comparison in future studies and providing uniformity in treatment strategies offered by health services is strongly recommended.

External ophthalmomyiasis by Oestrus ovis: A case report from Davangere

External ophthalmomyiasis is an infestation of the eye with larvae of Dermatobia hominis or Oestrus ovis (sheep bot fly). We describe a case of ophthalmomyiasis in a 38-year-old male, who presented with ocular foreign body sensation, redness, pain, and watering of the eye. The causative larvae were removed and sent to the laboratory for identification. By studying morphological features, it was identified as the first instar larvae of O. ovis. The patient was put on topical and oral antibiotics but was lost to follow-up. This is probably the first report from this part of Karnataka.

Miíase maxilofacial: relato de casos

Introdução: A miíase é uma afecção produzida pela infestação de larvas de moscas em pele e outros tecidos, sendo mais frequente nos países subdesenvolvidos e tropicais. Além disso, quando diagnosticada e tratada tardiamente pode levar o paciente a óbito. Objetivo: Há várias formas de tratamento descritas e a escolha da terapia varia a cada caso, segundo o número de larvas e o tecido envolvido. O intuito deste trabalho é relatar dois casos clínicos de miíase envolvendo a região maxilofacial, demonstrando a eficiência e a segurança da terapia escolhida. Relato de caso: Dois pacientes foram tratados através da remoção mecânica das larvas com auxílio de pinça e administração, por via oral, de antiparasitário (Ivermectina 12mg, dose única). Observou-se uma redução total de larvas nas feridas sem nenhuma intercorrência significativa. Conclusão: A remoção mecânica das larvas associada com Ivermectina em dose única é uma opção viável para o tratamento de miíase na região maxilofacial.

Ocular Manifestations of Mosquito-Transmitted Diseases

Of the 3,548 known mosquito species, about 100 transmit human diseases. Mosquitoes are distributed globally throughout tropical and temperate regions where standing water sources are available for egg laying and the maturation of larva. Female mosquitoes require blood meals for egg production. This is the main pathway for disease transmission. Mosquitoes carry several pathogenic organisms responsible for significant ocular pathology and vision loss including West Nile, Rift Valley, chikungunya, dengue viruses, various encephalitis viruses, malarial parasites, Francisella tularensis, microfilarial parasites, including Dirofilaria, Wuchereria, and Brugia spp., and human botfly larvae. Health care providers may not be familiar with many of these mosquito-transmitted diseases or their associated ocular findings delaying diagnosis, treatment, and recovery of visual function. This article aims to provide an overview of the ocular manifestations associated with mosquito-transmitted diseases.

Myiasis caused by Dermatobia hominis in Mexico: morphological and molecular identification using the cytochrome oxidase I gene

Myiasis caused by Dermatobia hominis , the human botfly, is frequent in the Americas, however, scarce morphological and molecular information exist regarding this dipteran. We describe three cases in urban areas of Mexico were D. hominis is not endemic. Morphological and genetic identification were performed using the cytochrome oxidase I as a molecular marker. The mitochondrial cytochrome oxidase I gene is useful for inferring the genetic divergence of D. hominis .

Imported and Autochthonous Cases of Myiasis Caused by Dermatobia hominis: Taxonomic Identification Using the Internal Transcribed Spacer Region

Dermatobia hominis is a fly endemic to and widely distributed throughout the Americas; it is found from the southern regions of Mexico to Argentina. However, because of widespread travel, myiasis has become common in countries where neither the disease nor the species that cause this infection are endemic. Central Mexico, for instance, is not a region where myiasis is endemic. We, thus, describe three cases of D. hominis myiasis: two autochthonous cases from the southern part of Mexico and one imported from Costa Rica. In addition, morphological and genetic identification was performed on the maggots extracted from the patients.

External ophthalmomyiasis due to Dermatobia hominis. A case report

CLINICAL CASE

A 46-year-old woman with no relevant medical history, native of Honduras and resident in Spain for one and a half months. The patient went to the Emergency Department due to inflammation of the upper eyelid of the right eye, with an area that simulated an abscess. This was drained (obtaining hardly any purulent content). Treatment was prescribed with oral and topical antibiotics, as well as an anti-inflammatory drug. One week later the patient returned, with improvement of the inflammatory signs, but with discomfort and corneal erosions. After eversion of the upper eyelid, a «worm» type parasite emerged from the tarsus. The extraction was completed with a clamp, and was later identified as Dermatobia hominis (Dh) by examination of a fresh specimen. The subsequent outcome of the patient was favourable.

DISCUSSION

Preseptal cellulitis in patients from tropical and sub-tropical areas can be caused by Dh.

Ophthalmomyiasis externa: A case report from Alkharj, Saudi Arabia

Ophthalmomyiasis is an infestation of mammalian eyes with larvae or maggots of certain flies. Oestrus ovis is the most common cause of human myiasis. This article reports a case of ophthalmomyiasis externa caused by Oestrus ovis (sheep nasal botfly) in a young healthy male, living in Al Kharj, Kingdom of Saudi Arabia. Patient presented with acute symptoms in left eye in April, mimicking as unilateral conjunctivitis/keratitis/external ocular foreign body/uveitis. Prompt diagnosis and mechanical removal of five live larvae from conjunctival fornices of the left eye under topical anaesthesia and cyclopentolate 1% eyedrops, not only relieved patient’s severe symptoms in a single day but also prevented rare yet sight threatening complications.

External Ophthalmomyiasis Due to Dermatobia hominis Masquerading As Orbital Cellulitis

Human parasitization by oestrid flies is a rare occurrence. The authors report a case of ophthalmomyiasis externa caused by Dermatobia hominis infestation in a 10-year-old female. Misdiagnosis resulted in a delay in treatment, which can be potentially devastating in cases of orbital or ocular involvement. The treatment of choice is early surgical removal of the larvae to minimize the inflammatory response and the extent of surgery. Patients should also be screened for multiple sites of cutaneous infestation. When the organism is completely excised, the prognosis is good.

Myiasis caused by Dermatobia hominis: countries with increased risk for travelers going to neotropic areas

Here, we review the human botfly (Dermatobia hominis), which belongs to a group of Diptera generically known as "myiasis-causing flies," characterized by the ability of their larvae to develop in animal flesh. In addition to its medical and economic importance, there is an academic interest in this botfly because of its peculiar biology, particularly because a phoretic diptera is needed to complete the life cycle. The larvae penetrate the host's skin, causing furuncle-like lesions that are pruritic, painful, and resemble subcutaneous nodules, producing irreversible perforations in the skin. Although D. hominis is distributed from Mexico to Argentina, a review performed by our working group from 1999 to 2015 determined that the countries with the highest infection rates in travelers are Belize, Bolivia, and Brazil. Interestingly, infected men show a higher variation in the distribution of the lesions than in women. Many treatment schemes have been suggested, including the application of highly dense liquids to the lesion to cause anoxia in the D. hominis larvae. We showed, for the first time, a Bayesian inference between D. hominis and other myiasis-causing flies. The flies grouped into two main clusters according to their capacity to produce facultative and obligatory myiasis, and D. hominis was phylogenetically close to Cuterebra spp.

External ophthalmomyiasis: a case series and review of ophthalmomyiasis in Turkey

Ophthalmomyiasis externa is the infestation of the superficial external ocular structures by fly larvae. This is a particularly rare condition, which has nevertheless been reported in several countries worldwide. It is common in sheep-farming areas, especially in Mediterranean countries. The patients may present with classic conjunctivitis, pseudomembranous conjunctivitis, conjunctival hemorrhages, punctuate keratitis, keratouveitis, and eyelid edema with erythema. Herein, we present three cases of external ophthalmomyiasis caused by Oestrus ovis larvae and review ophthalmomyiasis cases reported from Turkey.

Ophthalmomyiasis Externa: A Report of Three Cases

Three patients were admitted to our clinic with symptoms of conjunctivitis. On ocular examination, moving larvae were seen in the conjunctival sac. All of the larvae were immobilized by topical cyclopentolate and removed mechanically under topical anesthesia. The patients healed without any complications after the treatment. Physicians should consider ophthalmomyiasis externa in patients presenting with similar symptoms, especially in areas with high numbers of livestock. Otherwise the diagnosis can be missed.

Incidence of myiasis among humans-a review

Myiasis, the infestation of tissues of live humans and other vertebrate animals with dipteran larvae (maggots), is a phenomenon of widespread occurrence throughout the tropical regions of the world. It is commonly seen in domestic and wild animals but occurs rarely in man also. The tissue invasion in man by maggots is generally a well-recognized complication of neglected wounds. The condition may be asymptomatic but occasionally results in more or less severe problems and even death when larvae invade body cavities or areas that forbid their direct visual examination. Many cases of myiasis, however, usually do not reach the attention of medical practitioners because of the tendency of the mature larvae to migrate out of the lesion for pupation. In the present study, the authors reviewed the past literature describing the cases of human myiasis, causative fly species and predisposing factors for the onset of the same. The aim of the present manuscript is to provide a database for the future reference of medical entomologists, medical practitioners and veterinarians. Review of literature revealed that 37 fly species belonging to ten families were responsible worldwide for the onset of human myiasis. The incidence of myiasis among humans can be correlated to increasing fly populations, poor hygienic conditions and presence of domestic animals in the close vicinity. Other factors responsible for myiasis include neglected open wounds and foul-smelling discharge from natural body openings. Moreover, ignorance plays a key role in its occurrence since people are generally unaware about the actual cause and often correlate the condition to their superstitious beliefs. It is emphasized that the patients should not neglect their wounds and should take proper medical care; otherwise, myiasis may supervene.

Animal-inflicted ocular and adnexal injuries in children: A systematic review

Eye injury remains the leading cause of monocular blindness in children despite 90% of injuries being potentially preventable. Children interact with animals in a variety of situations, and the associated dangers may be underestimated. Animals are capable of causing ocular and adnexal injuries that are cosmetically and visually devastating. We examine the current literature regarding the nature and severity of animal-inflicted ocular and adnexal injuries in children.

Ophthalmomyiasis externa by Musca domestica in a case of orbital metastasis

Infestation of the living tissues of the eye, ocular adnexae or orbit by larvae of flies of the order Diptera is known as ophthalmomyiasis. Ophthalmomyiasis externa is a limited superficial infestation of external ocular structures such as conjunctiva and adnexae. A case of follicular carcinoma thyroid with orbital metastasis presenting as ophthalmomyiasis externa is reported. The patient presented with foul smelling ulcers of the medial and lateral orbital walls of the right eye extending into the lids and nose, teeming with maggots. Computerized Tomography (CT) showed widespread bone destruction with extension into surrounding sinuses. Over 200 maggots were manually removed after immobilisation with turpentine oil instillation. Entomological examination showed it to be a case of accidental myiasis caused by the common housefly Musca domestica. The patient was managed conservatively and the ulcer cavities filled up with healthy granulation tissue. This case is presented on account of its rarity.

Botfly larva masquerading as periorbital cellulitis: identification by point-of-care ultrasonography

Myiasis, or the infiltration of the botfly larvae, is a relatively frequent problem encountered by travelers to parts of Latin America. This is a novel case report that documents a Dermatobia hominis infestation of the left facial region with secondary periorbital cellulitis diagnosed by point-of-care ultrasonography.

Orbital parasitosis

Orbital parasitoses are uncommon diseases. Due to specific characteristics of orbital space, many different diseases, such as tumors and inflammatory disease, can present with similar clinical manifestations. The aim of this study is to review the most important clinical, epidemiological, and treatment aspects of orbital parasitoses described worldwide.

Myiasis

Myiasis is defined as the infestation of live vertebrates (humans and/or animals) with dipterous larvae. In mammals (including humans), dipterous larvae can feed on the host's living or dead tissue, liquid body substance, or ingested food and cause a broad range of infestations depending on the body location and the relationship of the larvae with the host. In this review, we deeply discuss myiasis as a worldwide infestation with different agents and with its broad scenario of clinical manifestations as well as diagnosis techniques and treatment.

Oestrus ovis ophthalmomyiasis with keratitis

A 35-year-old male patient presented with complaints of redness, swelling around the eyelids, watering, and irritation in the right eye. At presentation his best-corrected visual acuity was 20/20 partial in the right eye. The tarsal conjunctiva of the upper eyelid showed injection with pseudomembrane. Underneath the pseudomembrane we noticed four motile larvae. The cornea showed an irregular cobweb-like mucous plaque adherent to the epithelium, with a clear stroma. The pseudomembrane was easily peeled-off under topical anaesthesia. The organisms were removed and identified as Oestrus ovis. Three days later the patient was comfortable and his visual acuity was 20/20 in the right eye.

Myiasis of the upper eyelid

Myiasis rarely occurs in the eyelids. We report a 3-year-old girl with a myiasis of the upper eyelid after a trip to Central America. A 1.5 cm larva of a Dermatobia hominis was excised. Infestation with D. hominis should be suspected when a localized swelling with a central fistula in an eyelid is present in patients who have been to Central and South America.

Botfly myiasis: a case report

Cutaneous infestation by the human botfly, Dermatobia hominis, results in furuncular myiasis. This condition is endemic to the forested areas of Mexico, Central and South America. However, because of widespread travel, furuncular myiasis has become more common in North America. Misdiagnosis and mismanagement can occur owing to limited awareness of the condition outside endemic areas. To our knowledge, there is only a single report of botfly myiasis in the recent emergency medicine literature, which is surprising since the emergency department is likely to be the place many patients with this condition first seek attention. We present and discuss the case of a 50-year-old man with furuncular myiasis acquired in Belize. Parasitic infestation should be included in the differential diagnosis of a new skin lesion in patients who have travelled to endemic areas.

Ivermectin: uses and impact 20 years on

PURPOSE OF REVIEW

Ivermectin was first discovered and used in veterinary medicine over 20 years ago. This review highlights some of the recent published research from 2005 through June 2006 on the use of ivermectin in both helminth and arthropod infection.

RECENT FINDINGS

In recent years, several published studies have detailed the expanding role for ivermectin in multiple endo and ectoparasitic infections, including scabies, pediculosis, soil transmitted helminths, gnathostomiasis and myiasis. In addition, there is increasing experience with parenteral ivermectin for the treatment of disseminated strongyloidiasis. The success of ivermectin in reducing Onchocerca volvulus and Wuchereria bancrofti transmission through universal treatment in disease control programs continues to be well documented, but recent epidemiologic data describe suboptimal response to ivermectin by O. volvulus in a minority of individuals, the molecular markers for which are currently under investigation.

SUMMARY

Over 20 years of research and clinical use have advanced ivermectin from its beginnings as a veterinary anthelmintic to its significant role in several successful disease control programs. Nevertheless, further research is needed to understand the basis for suboptimal response and to better define optimal drug regimens for varying diseases.

Myiasis as a risk factor for prion diseases in humans

Prion diseases are transmissible spongiform encephalopathies of humans and animals. The oral route is clearly associated with some prion diseases, according to the dissemination of bovine spongiform encephalopathy (BSE or mad cow disease) in cattle and kuru in humans. However, other prion diseases such as scrapie (in sheep) and chronic wasting disease (CWD) (in cervids) cannot be explained in this way and are probably more associated with a pattern of horizontal transmission in both domestic and wild animals. The skin and mucous membranes are a potential target for prion infections because keratinocytes and lymphocytes are susceptible to the abnormal infective isoform of the prion protein. Iatrogenic transmission of Creutzfeldt-Jakob disease (CJD) was also recognized after corneal transplants in humans and scrapie was successfully transmitted to mice after ocular instillation of infected brain tissue, confirming that these new routes could also be important in prion infections. Some ectoparasites have been proven to harbour prion rods in laboratory experiments. Prion rods were identified in both fly larvae and pupae; adult flies are also able to express prion proteins. The most common causes of myiasis in cattle and sheep, closely related animals with previous prion infections, are Hypoderma bovis and Oestrus ovis, respectively. Both species of flies present a life cycle very different from human myiasis, as they have a long contact with neurological structures, such as spinal canal and epidural fat, which are potentially rich in prion rods. Ophthalmomyiases in humans is commonly caused by both species of fly larvae worldwide, providing almost direct contact with the central nervous system (CNS). The high expression of the prion protein on the skin and mucosa and the severity of the inflammatory response to the larvae could readily increase the efficiency of transmission of prions in both animals and humans.