Cutaneous myiasis

What is it cutaneous myiasis?

Myiasis is infestation by the larvae (worms) of fly species within the arthropod order Diptera (adult two-winged flies). The larvae feed on the hostliving or dead tissue, bodily substances or ingested food. Cutaneous myiasis is myiasis that affects the skin.

Myiasis can be classified clinically according to the area of the body infested, for example, cutaneous, ophthalmic, atrial and urogenital. Cutaneous presentations include furuncular, migratory, and wound myiasis, depending on the type of infesting larvae.

Furuncular myiasis

Dermatobia hominis

• Dermatobia hominis is found in Central and South America. The female fly D. hominis lays her eggs in the foliage o carrier insects, most commonly mosquitoes. The eggs are passed to humans by direct contact with foliage, or during a bite by the carrier.
• Once the eggs hatch, the larvae burrow no pain on the host's skin producing a small red papule (bump). The papule then becomes a kind of furuncular (similar to boil) nodule with a central pore through which organism breathe Occasionally, the end of the larva's tail can be seen through this pore.
• Over the next 5 to 10 weeks, the larvae develop further and burrow deeper into the host's skin, forming a dome-shaped cavity. Symptoms include itching, sensation of movement, stabbing pain (often at night), and serosanguinous (thin, yellow, or bloody) download.
• The larvae eventually return to the surface of the skin, then fall to the ground where they pupate to form flies.
• Lesions usually resolve with minimal scarring after the larvae emerge or are shed. The most important complications of D. hominis are bacterial super-infection (rare) and tetanus. D. hominis has caused fatal cerebral Myiasis in infants due to infestation of the skin covering the fontanelles.

Cordilobia

• Cordilobia is found in tropical Africa. All three Cordylobia species can cause furuncular myiasis, however, C. anthropophaga is the most common culprit.
• These flies prefer shade and generally lay their eggs on objects contaminated with urine or feces, such as sandy soil or wet clothing that dry on the ground.
• The eggs hatch in 1-3 days and the larvae can survive for up to 2 weeks while waiting to come into contact with a host. The larvae painlessly penetrate the host's intact skin. They develop over 8-12 days. After this, they emerge from the skin, fall to the ground and pupate.
• Symptoms develop within the first 2 days of infestation and can range from a "stinging heat" sensation to severe pain. Agitation and insomnia can also occur. Furuncular lesions with around inflammation they develop rapidly over a period of 6 days after symptoms begin. In the final stages, the tail end of the larvae can sometimes be seen in the central pore, and it can pull away when touched.
• If there are multiple sites of infestation, Hosts may develop enlarged lymph nodes and fever. If the lesions are numerous, they can get together forming big plates with a serous (thin, yellow) discharge.

Cuterebra species

• Cuterebra is found in parts of North America. Human Cuterebra infestation is rare as the usual hosts are rodents, rabbits, and squirrels.
• Cuterebra eggs are laid near their usual hosts on grass or undergrowth. Humans probably inadvertently come into contact with the eggs, which then hatch, and the larvae enter the host through the skin mucous membranes of the nose, eyes, mouth or anus.
• Almost all human cases are present in August, September, or October.
• The typical injury It is a 2-20 mm red nodule or papule with a central pore, through which the body breathes. The larva is occasionally visible through this pore. A serous, serosanguinous or purulent (consisting of pus) a discharge may occur. The lesions can be itchy or painful, and some patients experience a sensation of movement within the lesion.

Wohlfahrtia vigil and opaque Wohlfahrtia

• W. vigil is found in parts of North America, Europe, Russia, and Pakistan. W. opaca is found in parts of North America. Larvae of W. vigil and W. opaca cause furuncular myiasis in cats, dogs, rabbits, ferrets, mink, foxes, and humans. In almost all hosts, infestations occur primarily in the very young, because the larvae cannot penetrate the adult skin.
• The females of both Wohlfahrtia species are most active in shady areas, during the late afternoon. The larvae are dropped onto the host's skin, which then penetrate. Boils form within 24 hours. The larvae develop for 4-12 days, then leave the skin, fall to the ground and pupate.
• Most of the cases occur during the months of June to September.

Migratory myiasis

Gasterophilus intestinalis

• G. intestinalis is the most common cause of human migratory (or progressive) myiasis and is found worldwide. G. intestinalis is generally an intestinal parasite of horses and other equidae.
• Humans are an accidental host and are infested by direct contact with the eggs in the horse's fur or the eggs can be deposited directly on human skin. The larva initially produces a papule similar to furuncular myiasis. Then the larva burrows into the lower layers of the epidermis, causing an intense itch, like a snake and raised in red linear injury that advances at one extreme and vanishes at the other as it seeks a place to develop. The injury can extend up to 30 cm per day and can continue for several months. The infestation may end spontaneously with or without suppuration (formation of a purulent sore).

Hypoderma bovis and H. lineatum

• Hypoderma species generally infest livestock and are found in most places in the Northern Hemisphere.
• Human infections are rare and generally occur in rural areas where livestock are raised. The eggs are deposited on the hairs of the body and the larvae enter through the skin or mucous membrane from the mouth The larva migrates in subcutaneous tissue, causing a raised area 1 to 5 cm slightly red, tender and poorly defined. A “prick” sensation and, less commonly, burning and itching are reported. After several hours to several days, the redness subsides, leaving a yellow color.pigmented patch, while the larva wanders elsewhere. A faint, irregular, palpable the line connects the old area of redness with the new one. The larvae can migrate from 2 to 30 cm per day. Most often, the larvae eventually die in the subcutaneous tissue.
• In about 1 in 15 human cases, the subcutaneous larvae penetrate dermis and forms a slow-growing, tender red nodule (warble). A central pore develops, through which the larvae can be visible. The pore intermittently drains a serosanguinal discharge, which then becomes purulent. The itching becomes intense and the larva grows, emerges, and falls to the ground to pupate.
• Human hypodermic myiasis is usually a mild disease, but can cause fever, muscle pain, joint pain, scrotal swelling, ascites (fluid in the peritoneal cavity of the abdomen), fluid around the heart, and invasion of the brain and spine cable.

Wound myiasis

Wound myiasis occurs when fly larvae infest open wounds on a living host. Mucous membranes (eg, oral, nasal, and vaginal membranes) and body cavity openings (eg, in or around the ears and eye socket) can also be affected. Severe cases may be accompanied by fever, chills, pain, bleeding from the infested site, and secondary infection. Blood tests may show elevated neutrophils and eosinophils. Massive tissue destruction, loss of eyes and ears, erosion of bones and sinuses, and death can occur.

Factors that make humans susceptible to wound myiasis include poor social conditions, poor hygiene, old or very young age, psychiatric disease, alcoholism, diabetes, peripheral vascular illness, poor dental hygiene, and physical disabilities that restrict the ability to deter flies.

Cochliomyia hominivorax

• Cochliomyia hominivorax is found in Central and South America. In humans, C. hominivorax infestations generally occur in or around the ears, nose, and eye socket. Even small wounds like a tick bite or an ingrown toenail can attract C. hominivorax. The female lays her eggs on the edges of wounds or healthy mucous membranes. Within a day, the eggs hatch and the larvae feed on the tissue causing massive tissue destruction and large deep injuries. An odor is produced that attracts more female flies to lay additional batches of eggs. A single wound can contain up to 3,000 larvae, which eventually fall to the ground to pupate.

Chrysomya bezziana

• Chrysomya bezziana is found in Africa, India, and Southeast Asia. The life cycle and biological activity of C. bezziana is similar to that of C. hominivorax. As these larvae burrow deeper into the host's tissue, only the black ends of the tail are seen. C. bezziana infests wounds, areas of soft skin, and mucous membranes. The only presentation features of a nasal breast The infestation can be a swollen face associated with headaches, fever, nasal burning and runny nose.

Wohlfahrtia magnifica

• Wohlfahrtia magnifica is found in parts of Europe, Russia, North Africa, and the Middle East. Adult W. magnifica flies are active in the summer months during the warmest part of the day. In humans, wounds, ears, eyes, and nostrils are often infested. Larvae of W. magnifica are generally less destructive than C. bezziana and C. hominivorax.

How is cutaneous myiasis diagnosed?

• The diagnosis of cutaneous myiasis is made primarily on the clinical appearance of the lesions, associated symptoms, and travel history. Dermoscopy biopsy and ultrasound may be helpful See myiasis pathology.
• Submerging the lesion underwater can confirm the diagnosis: if the larva is alive, bubbles will be produced.
• G. intestinalis larvae can be diagnosed by massaging a thin layer of mineral oil over the red lesion. Low magnification, black transverse Stripes representing spines can be seen on the larva's body segments.

What is the treatment for cutaneous myiasis?

Occlusion, you can use manual extraction of larvae and larvicides.

Occlusion

• The larvae require contact with air to breathe. The occlusion kills the larva or induces it to move up, where it can be eliminated.
• A variety of occlusive Substances such as petroleum jelly, animal fat, beeswax, paraffin, hair gel, mineral oil and bacon. The occlusive substance is placed over the pore of the boil, or over the myiasis area of the wound, for up to 24 hours.
• Once the larvae have migrated to the surface of the skin, they can be removed with forceps. This can be difficult as the larvae resist extraction by using their spines to anchor themselves to the host. D. hominis is the most difficult larva to extract due to its conical shape.
• Occasionally, the larva suffocates without emerging. Retained larvae can cause a inflammatory response, leading to a foreign body granuloma formation (a group of inflammatory tissues) that can progress to calcification.

Manual removal of larvae

Furuncular myiasis

• A surgical incision It's done. The larva is then removed with forceps. Care must be taken to avoid damaging the larva, as retained parts can cause a severe inflammatory reaction. Anesthetizing the larva with local anesthetic it can prevent you from anchoring your spines.
• Alternatively, Local anesthesia it is forcibly injected into the base of the lesion in an attempt to create enough fluid pressure to push the larva out of the pore.
• A commercial vacuum snake venom extractor can also be used to suck out the larvae.
• Traditional larvae removal methods involve squeezing the skin around the boil with your fingers or wooden spatulas.
• Hypodermal myiasis can be treated with these methods if a sled has formed.

Migratory myiasis

• Hypoderma larvae can be removed through a surgical incision if there is no sled formation, but it can be difficult to capture.
• Gasterophilus can be removed by making a small surgical incision over the leading edge of the advancing lesion and using the tip of a sterile needle to remove it.

Wound myiasis

• Manual removal followed by irrigation is used to treat wound myiasis. Surgery may be necessary to remove dead tissue from the host.

Larvicides

• Ivermectin is a broad-spectrum antiparasitic agent that can kill the larvae or at least cause them to migrate out of the skin. Ivermectin can be administered topically or as an oral dose.

• The mineral turpentine can be effective against Chrysomya larvae and can aid in their elimination in cases of wound myiasis.
• Ethanol spray and betel leaf oil can be used topically to treat C. hominivorax myiasis.

How can myiasis be prevented?

• Use window and mosquito nets, insect repellants and insecticides, suitable protective clothing, and good skin and wound hygiene to prevent flies, mosquitoes, and ticks from reaching the skin.
• Cover open wounds and change bandages daily
• In the case of C. anthropophaga, hang clothes to dry in sunlight and / or iron (heat destroys both eggs and larvae)
• Improve hygiene and sanitation (for example, remove trash from living areas)