Fly bite of an adult and a child

Dipterology, which studies flies, describes almost 120 thousand species of these insects, and some of them can bite humans. In most cases, a fly bite causes only mild skin irritation, but some species carry pathogens, including dangerous ones. It all depends on which fly bit you.

Although it is difficult to identify the type of insect, especially if you have not seen it. And then there may be complaints about the bite of a triangular fly or a striped fly...

Which flies can bite a person, and which cannot, and why?

Flies are assigned to the suborder Brachycera (short-mouthed) of the order Diptera (Diptera), numbering more than a hundred families. Some of its representatives parasitize in the larval stage, but adults - scavenger flies and blowflies of the families Calliphora and Coprosarcophaga (or Sarcophagidae) - are not parasites, but can be mechanical carriers of various pathogenic organisms. At the same time, the mechanical transmission of microbes by flies, whose diet does not include the blood of warm-blooded animals, is not associated with bites.

So, the housefly (Musca domestica) does not bite a person; the bites of a raspberry fly (long-wattled stem gall midge, Drosophila suzukii of the suborder Sophophora or a fruit fly belonging to the Tephritidae family) are not possible. [1],  [2],  [3] Sting flies, hoverflies (Episyrphus balteatus, Syrphus ribesii, Syrphus blandus or Musca ribesii L.), which has some resemblance to wasps - also entomological nonsense, since these insects bite simply nothing, and your food - nectar and pollen - Adult the insect extracts with the proboscis. [4], [5]

Similar to the reasons for which can not be a bite of a gray fly (Sarcophaga carnaria family Sarcophagidae)  [6],   and a bite of a green fly (Lucilia sericata or Phaenicia sericata family Calliphoridae): they necrophages, ie feed on decaying organic matter, for which an insect is enough available to them spongy mouthparts... Also in their "diet" includes food waste and excrement. [7],  [8], [9]

This also includes the bite of a wolfart fly (Wohlfahrtia magnifica or Sarcophila Wolfartii), which, feeding on plant juices, is not able to bite anyone. But its larvae, which emerge from eggs laid by females on mucous membranes or damaged skin, can cause  deep myiasis of the skin  and muscle tissues. [10],  [11], [12]

There has never been a bite from a landfly (Pollenia rudis or Musca familiaris of the Callflyhoridae family), which parasitizes earthworms and lays eggs in the soil. [13]

Of course, among the species of Diptera Brachycera, there are both predators (for other insects) and blood-sucking (hematophages). [14],  [15] The reasons for the flies of the Hippoboscoidea superfamily - of the families Glossinidae (tsetse fly), Tabanidae, Haematopota, Chrysops, Rhagionidae, genus Stomoxys (autumn flies) - to hunt and bite warm-blooded animals or a person caught in the field of view, lie in the peculiarities of their reproduction. [16]

Epidemiology

According to statistics, for every person on Earth there are more than 200 million insects, including 17 million flies. Of course, no one counts the number of their bites.

For example, in the summer of 2018, all British publications reported on the invasion of horse flies in the country - due to significant warming, but there was no information on the number of British people bitten by flies.

Tsetse flies, which carry sleeping sickness pathogens, are found in rural areas in 37 countries in Sub-Saharan Africa. Thanks to the efforts of local authorities, supported by special programs of the World Health Organization, from 2005 to 2015, the incidence of sleeping sickness was reduced from 15.6 thousand registered cases per year to 2.8 thousand. [17]

However, today 70-80 million people in 20 African countries are at different levels of risk of developing the disease, and only 3-4 million people live in endemic areas where epidemiological surveillance is carried out. [18]

Symptoms of the fly bite

Experts emphasize that in most of these species, only female flies feed on the blood, having sharp chitinous outgrowths (stilettos) with which they pierce the skin. Moreover, in many hematophagous flies, the need for blood occurs periodically - before laying eggs (to ensure their maturation and development).

Biting flies detect a suitable object (animals or people) by feeling the exhaled carbon dioxide and moisture, sweat and heat radiated from the body. After piercing the victim's skin, the insect releases saliva containing anticoagulant into the wound.

Tsetse fly bite

Since we are talking about the tsetse fly, let's start with it. The blood-sucking tsetse fly - Glossina morsitans, Glossina palpalis, Glossina tachinoides of the Glossinidae family - can be up to 1.5 cm in length. Reproduction is larval, and females need blood to support the development of the larva in her body. [19]

It is considered the intermediate host of the  trypanosoma  (Trypanosoma brucei or Trypanosoma gambiense).

The key risk factors for being bitten by this fly are staying in endemic regions of the African continent. [20]

What does a tsetse fly bite look like? The bite is often painful and can cause redness and swelling of the area of the skin or small red sores on it - marks from the chipping that the insect's mouth is equipped with. Since the insect moves quietly, the first signs of a bite are noticed too late. After about a few weeks, the victim may develop symptoms such as headaches and muscle aches, swollen lymph nodes, fever, lack of coordination, and convulsions. As the disease progresses, those infected feel constant fatigue and sleepiness, and personality changes may occur, indicating damage to the brain and central nervous system. By the way, an infected person may not have any symptoms, but he becomes a carrier of trypanosomiasis. [21]

Trypanosoma brucei gambiense can develop in the human body over several years, and T. Brucei rhodesiense can be fatal within a few months. Sleep sickness is usually fatal without treatment with antitripanosomal drugs. Read more -  African trypanosomiasis (sleeping sickness) . [22]

Flame fly bite

In autumn, throughout Europe and North America, cattle, rabbits, dogs, rats, and sometimes humans can be bitten by synanthropic flies (Stomoxys calcitrans), and individuals of both sexes. These flies are obligate bloodsuckers with chitinous outgrowths for piercing the skin of victims, which, by the way, is very painful. So, in the first place, the sting of a flare fly causes acute pain. And the most characteristic localization of bites is the ankle. [23]

Through the resulting microscopic incision, the fly inserts the proboscis under the skin, simultaneously releasing saliva containing digestive enzymes (which help the insect get nutrients from the blood) and various isoforms of proteins that prevent blood clotting. So very quickly a swelling appears on the skin after a fly bite, and the bite begins to itch. [24]

It is clear that the pathogenesis of pruritus is due to the release of histamine from the mast cells of the damaged epidermis. And the development of an inflammatory reaction is the result of an increase in IgG antibodies in the blood. [25]

Fly bites in children, as well as in people with a weaker immune system or increased sensitization of the body, increases the risk of more serious symptoms: there may be a systemic allergy to a fly bite - with anaphylaxis that causes breathing problems, dizziness, and facial swelling. [26]

Moose fly bite

In everyday life, the bite of a moose fly Cephenemyia ulrichii (family Oestridae) or Haematobosca alcis (family Tabanidae), which resembles a bumblebee and is called by entomologists a moose gadfly, is usually defined as the bite of a striped fly. [27]

But the first variety, cephenemia, in the wild, attacks mainly the nostrils and the pharyngeal cavity of moose (as well as deer), but does not bite, but injects its larvae there. There are cases when flies of this species injected the larvae into the eyes of people, which, without timely medical assistance, can lead to the development of ophthalmomyosis. [28]

The bloodsucker (Lipoptena cervi or Hippoboscidae cervi) feeding on the blood of artiodactyls is also often called a moose fly, and it can also bite any warm-blooded animals, including humans. Her bites cause pain and itching of the skin with papules that disappear in two to three weeks. 

Black fly bite

The most common bite of a black fly is the bite of a female fly in the Simuliidae family (which includes about 1,800 species around the world). [29]

Simulids are small species (4-5 mm in length), live near running water, love hilly terrain, swarm in late spring and early summer - in the morning or in the evening, they are guided by smell. [30]

Their bites are more often localized to the head, neck and ears, and a small red spot is formed at the site of each bite, causing severe itching. The appearance of headache, nausea and edema of nearby lymph nodes is not excluded. [31]

Big fly bite

The largest flies are horseflies, the females of which attack warm-blooded animals. Read more -  Horsefly bite

The bite of the big fly Haematopota pluvialis, an ordinary horse fly-hematophage of the Tabanidae family, is hard not to feel: it is quite painful; almost immediately the bite site turns red and swollen, the skin becomes denser and hotter. [32]

In Europe, the large brown-yellow horse bloodsucker Hippobosca equina (superfamily Hippoboscoidea) is called forest flies. The fly is really big - up to 1.5-1.8 cm; active throughout the day. During the mating period, the female insect attack horses and cattle. [33]

Such a bite of a forest fly causes pain, irritation of the skin in the form of redness and itching, a rounded induration in the form of a papule appears. The irritation and swelling from the bites usually disappears after one to two days. But for some, the bite of this fly causes an allergic reaction. [34]

Yellow fly bite

A complaint about a yellow fly bite, although this description is appropriate for a dozen different species of flies of this color, may concern Diachlorus ferrugatus of the Tabanidae family (or Chrysops ferrugatus), which do not exceed 9-10 mm in size. Only females bite too, the food of males is pollen and nectar.

These flies usually disturb residents in late summer and early autumn; they avoid the bright sun and swarm in shady places under bushes and trees or overhead - in cloudy weather or in the late afternoon. Insect aggression is caused by moving objects of a dark color. 

The bite of these flies is painful, in its place there is redness and intense itching swelling.

Sand fly bites

Typically, bites from sandflies Phlebotominae of the Psychodinae subfamily, which are no more than 3.5 mm in size (and range in color from gray to yellow and brown), lead to redness and swelling of the skin with blistering. In addition, severe itching appears at the site of the bite. [35]

These insects are inhabitants of the subtropics and tropics, so the bites go to the inhabitants of these latitudes, as well as travelers going to hot countries. [36]

According to entomologists, the Phlebotominae family contains about 700 different species of sand flies, and two dozen of them, belonging to the genus Phlebotomus, Sergentomyia and Lutzomyia, carry pathogens. For example, phlebotomins, the largest population of which is located in the Amazon basin, carry the Leishmania sps promastigotes, which cause parasitic leishmaniasis in humans  . [37]

Sand flies are endemic in 90 countries on all continents except Australia. It should be borne in mind that, for example, in the tropical regions of Asia, the number of sand flies increases significantly during the monsoon season, and their hunting time is twilight and night. [38]

 

Complications and consequences

The possible consequence of a tsetse fly bite (sleeping sickness) was mentioned at the beginning of the article; you now also know what the threat of bites of sand flies is. But these are far from all the consequences and complications that fly bites can cause.

First, it is an allergic reaction: the bites of black and horse flies and sting flies can cause  anaphylaxis .

Secondly, intoxication and parasitic invasions, and with scratching - secondary infection of a bacterial nature.

Flay flies can cause infestation, defined as stomoxosis; they also carry the bacilli Francisella tularensis - the causative agent of  tularemia , rickettsia (Anaplasma, Coxiella), the West Nile and Rift Valley vector-borne viral fevers, as well as the  parasitic worms Onchocerca volvulus that cause  onchocerciasis . These nematodes can be "delivered" to humans by black flies, and tularemia pathogens - by deer and horse bloodsuckers.

In addition, deer flies are carriers of the bacterium Bartonella schoenbuchensis, which can cause inflammatory skin lesions in humans.

 

Diagnostics of the fly bite

It is impossible to determine exactly which fly has bitten the patient, diagnostics carried out in an ordinary clinic cannot: fly bites are identified using a stereomicroscope and taxonomic keys.

Therefore, it is important to examine the site of the bite and anamnesis, taking into account where, when and under what circumstances a person was bitten by an insect.

In cases of a systemic allergic reaction, a test for specific antibodies, including insect venom, may be performed.

Differential diagnosis

Differential diagnosis is carried out to exclude possible exposure to exogenous toxins, the presence of infectious diseases with skin manifestations and a false allergic reaction.

Treatment of the fly bite

First of all, wash the bite site with soap and water. Treatment of bites is carried out with the help of external agents.

How to smear a fly bite? The simplest antiseptics are suitable for disinfection: an alcoholic solution of iodine, a solution of hydrogen peroxide or fucorcin, ethyl alcohol, alcoholic tinctures of calendula or St. John's wort.

Cold compresses or ice packs are applied to relieve swelling and reduce itching.

You can also use Betadin, Sanitas, Calendula antiseptic ointments. Redness and itching help relieve: hydrocortisone ointment, Polcortolone cream (with triamcinolone), Belogent or Diprogent (with betamethasone and gentamicin), Ultralan, etc. More information in the article -  Ointment for itching  and material -  Ointment for irritation on the skin

With severe itching, use Crotamiton cream (not used for children under 12 years old).

An allergic reaction involves a mandatory visit to a doctor, who will prescribe the appropriate medications for oral administration -  antihistamines .

An alternative treatment is to use a soda solution (in the form of lotions); lubricating the bite with aloe juice, propolis tincture, tea tree essential oil, a mixture of lemon juice with salt and turmeric powder. A thin slice of raw potatoes applied to the bite very well relieves swelling.

It is advised to treat with herbs: plantain juice, lotions and compresses with water infusions of St. John's wort, yarrow, Potentilla, sweet clover, calendula or chamomile flowers.

Prevention

Sticky paper traps are ineffective because they are not as attractive to flies as warm-blooded animals. Smoky fumigators help more.

The use of pesticides has limitations in the fight against flies, since these agents only act on contact and quickly decompose after application. But repellents containing diethyltoluamide are effective for repelling most biting flies, that is, for preventing their bites. Also, these insects are repelled by the smell of essential oils of geranium and citronella.

The better the body is protected by clothing — long trousers and a long-sleeved shirt — the less chance flies flying in the forest, by the river, near the farmhouse, or in the pasture have to get to the skin and bite.