What is Miaz?
Miaz, myiasis (from the Greek. Myia – a fly, other transcriptions: myiosis, myasis) – a disease caused by the penetration and stay of larvae and adult arthropods in the tissues and cavities of the human body.
Typically, these insects (flies) feed on decaying substances of animal and plant origin; therefore, miasis usually occurs solely in places with poor sanitary conditions; in most cases, the infection occurs as a result of the casual negligence of a person. In humans, the disease can be caused by various species of these insects.
The endemic areas are tropical areas of Africa, South America, Mexico, California and New Guinea.
Causes of Miaz
The main miaz pathogens are the thornbill larvae (Cordylobia anthropophaga) and the sand flea (Tunga penetrans), whose females penetrate the skin through their moves, where the fertilized animal swells from eggs to the size of a pea, causing painful ulcerations.
In domestic practice, there are cases of parasitization in humans of wolfarth fly larvae (Wohlfahrtia magnifica) and various gadflies (usually Russian and sheep).
Representatives of the genus Gastcrophilus, Hypoderma, Dermatobia and Cordylobia affect the skin; Fannia affects the digestive tract and urinary system; Phonnia and Wohlfahrtia can infect open wounds and ulcers; Oestrus affect the eyes; as well as Cochliomyia penetrate into the nasal passages and carry out their invasion.
The larvae of flies are relatively stable in relation to various factors, in particular chemical reagents. It is possible to note the ability of the “rat” – the larvae of the Eristalis fly to dwell in wastewater and other highly contaminated places (accumulation of liquid feces, etc.); the larvae of many flies do not die in solutions of formalin or alcohol as compared with the larvae of other insects. All these features of the larvae of flies determine their ability to live for one or another period in an unusual environment for them, for example, in the human intestines, where they can get with food.
Pathogenesis during Miaz
Adult flies lay eggs in the eyes, ears, nose, wounds of people or inject them subcutaneously. Less commonly, visceral lesions are observed due to accidental ingestion of the larvae.
Miases are classified both by the location of the larvae in the host and by the biological properties of the larvae of the corresponding species of flies.
Miases are divided into random, optional and obligate.
- Random miases cause the larvae of those species of flies that normally develop in rotting substances. They enter the human body by accident. Flies lay eggs on food, underwear, etc. Larvae emerging from eggs can be swallowed with food. From underwear, larvae can creep into the urethra. Thus, a person becomes infected with intestinal or urinary myiasis.
- Obligatory miases lead an exclusively parasitic lifestyle, affecting various herbivores.
- Optional myiasis causes occasional lesions (for example, lesions caused by meat or house flies).
According to localization, there are skin, tissue, cavity miiasis (ear, nose), intestinal, miiasis of the urinary tract, genitals and ocular.
- Cutaneous (tissue) myiasis, in turn, is of various forms.
– Epidermal myiasis; the larvae live in the thickness of the epidermis and do not go beyond it (for example, the larva of the 1st phase of the Gastrophilus gadfly, causing creeping disease).
– Subcutaneous myiasis with localization of the larvae in the connective tissue layers of the skin, and the epidermis can be affected for the second time (for example, the skin gadfly of Hypoderma cows, whose larvae can also hospitally parasitize in humans); the corresponding form of myiasis is called subcutaneous myiasis with a moving swelling of the skin above the migrating larva; larvae of cutaneous human gadfly Dermatobia and Cordylobia flies. anthropophaga cause the development of furunculous myiasis.
– Subcutaneous myiasis can pass into the tissue, when the larvae of flies fall into ulcers or wounds and begin to corrode living tissue of the host body; ultimately, enormous destruction of the soft parts of the body can occur. Such forms of myiasis sometimes take a generalized character and can be the cause of the death of the host (for example, cases known from history of “jamming by worms” (ie, larvae of flies) of a person to death); tissue myiasis, in particular wound myiasis, is caused by both obligate (Wolfhart fly larvae) and optional parasites (carrion fly larvae (Lucilia), housefly (Musca domestica), meat fly (Calliphora), ochliomyia macellaria, Pycnosoma, etc.)
- Miaz cavity. Larvae can be found in:
– In a sheep gadfly (Oestrus ovis), or they cuddle in soft covers and destroy them (Wolfart’s fly).
– Oral cavities – in the gums, destroying their soft parts (for example, Wolfart’s fly); this phenomenon is apparently so frequent that among the people toothache is etiologically associated with the presence of “worms” in the mouth.
– The auditory meatus (otomyiasis) – Wolfart’s fly, etc .; Miaz here usually develops on the basis of any ear disease; larvae can destroy the tympanic membrane, middle ear, penetrate into the mastoid process, venous sinus and reach the meninges (consequences – even death).
– Urinary tract and bladder – larvae of Anthomyia (Fannia) canicularis, Musca domestica.
– The genitals – the larvae of the Wolfart fly (in the genital slit of sheep).
- Ophthalmic myiasis (osulomyiasis) – larvae in the conjunctival sac of the eye (Oestrus ovis, Rhinoestrus purpureus and Wolfhart fly in humans; the latter is especially dangerous, since its larvae can perforate the wall of the eyeball and completely destroy the eye).
In all these cases, infection of the host occurs passively. Some flies hatch their larvae in its cavity, in the eye, in ulcers or wounds, others lay eggs there, from which the larvae hatch already in the host. Larvae of some species (Cordylobia) are actively drilled into human skin. There are examples of even pupated stadiums in the host, so the concept of myiasis extends to all cases of any stages of metamorphosis of flies from an egg to puparium in the host or on it.
Intestinal myiasis refers to the cases of living flies larvae in the stomach or intestines of a person.
Infection of the digestive tract with larvae occurs as a result of swallowing them with food or with any other material. The larvae of the cheese fly (Piophila casei) live in salted fish, cheese and can be easily eaten; other flies can lay eggs in already cooked food (for example, boiled meat), and larvae also develop on the same substrate. There are frequent cases of obtaining larvae with vegetables, etc.
Symptoms of intestinal myiasis are different. With the localization of larvae in the stomach, there are nausea, vomiting and sharp pain in the epigastric region. When they are in the intestine, abdominal pain, hemorrhages and typhoid state come to the fore. With prolonged presence of larvae of flies in the intestine, colitis develops. Various types of flies can live in the human digestive tract: indoor fly, meat fly, carrion fly, cheese fly (Piophila casei), Anthomyia (Fannia) canicularis, Anthomyia scalaris, Eristalis, Philaematomyia, etc.
A diagnosis of intestinal myiasis must be made with caution in order to distinguish genuine cases of myiasis from imaginary ones. The latter include cases where patients deliberately mislead the doctor, bringing “parasites” that supposedly leave the intestines. Flies can lay eggs in the already excreted bowel movements, and larvae can hatch from the eggs before the feces get to the doctor for examination; in the latter case, all the larvae will be very small (about 1 mm), while adult larvae reach 1-1.5 cm in length, and sometimes more.
Symptoms of Miaz
Lesions with myiasis are usually acute. Larvae can eat away all soft tissue to the bones. Outside, the larval course is a reddish filiform thickening of the skin.
Clinically, lesions of internal organs resemble symptoms of intestinal perforation or abscesses of parenchymal organs.
The following types of myiasis are distinguished:
- Gastrophilosis is a variety of Larva migrans, the causative agent of which is the larva of the gadfly (Gastrophilus equi), which parasitizes in the stomach and intestines of horses. The larvae of the gastric gadfly migrate in the epidermis of the skin, making a move from 7-8 to 30 cm in a day.
- Dermatobiasis is a tropical myiasis caused by a larva of the gadfly (Dermatobia hominis), characterized by the formation of an abscessed node in the skin around the invading pathogen.
- Cordilobiosis (m. Africana; syn. Miaz African) is a tropical myiasis caused by the larva of the fly Cordylobia anthropophaga and characterized by the formation of an abscessed node in the skin around the invading pathogen.
Treatment of cutaneous myiasis consists in removing gadfly larvae from the moves they make, removing these larvae from wounds and ulcers, applying swabs with chloroform, and antiseptic treatment of ulcers and wounds; gadfly larvae are removed from the eye with tweezers or by washing, from the stomach by washing, from the intestines by various anthelmintic agents.
Treatment of ulcers on the body of domestic animals to destroy the larvae of flies in them, treatment of ulcers and wounds so that they do not attract flies to the purulent compartment ”protecting food from flies, eating well-washed and cleaned vegetables, especially if they are used fresh ; burning corpses and falling.