Venomous insect bites are a complex of reactions that occur in contact with hornets, bees, wasps, bumblebees, some species of spiders, scorpions. The pathological effect is caused by the penetration of four types of toxic substances into the victim’s body: amines, beltides, proteins, animal enzymes. Local symptoms include burning pain, hyperemia, edema. The spectrum of systemic phenomena includes dizziness, weakness, headache, diarrhea, signs of allergic reactions, convulsions, paralysis of the respiratory center. The diagnosis is established on the basis of anamnesis and clinical picture. Treatment involves the removal of the sting, the introduction of hormones, specific serums.
T63.9 Toxic effect due to contact with a poisonous animal, unspecified
Venomous insect bites is widespread everywhere except for permafrost zones. It occurs in the warm season, mostly ends well – the patient shows local signs of poisoning with animal poisons, disappearing after a few days. In 5% of situations, venomous insect bites lead to allergic reactions, mainly urticaria and angioedema. About 1-2% of cases are accompanied by pronounced neurotoxic effects, the development of seizures and death of the victim. Risk group: children, mushroom pickers, hunters, people whose work takes place outdoors.
The absolute majority of cases are associated with the provocation of an insect by a person: a touch of the hand, an attempt to get into the nest, to catch an animal. A bite is a way of protection that allows you to scare off a much larger and physically strong opponent or kill him. Attacks also occur for the purpose of reproduction. Thus, the human skin gadfly, which lives in Central America, is able to lay larvae on the skin, which are subsequently introduced into the tissues.
Risk factors of venomous insect bites include staying in a suburban area in summer, spring and autumn. People who often make trips to the forest, lakes, ponds, swamps without using protective equipment (clothing made of thick fabric, mosquito nets) are particularly at risk. Injuries resulting from careless contact with insects are characteristic of beekeepers. They get up to 15-20 stings per year. Allergic reactions occur in people who use bees as a folk method of treating rheumatic pains.
The pathogenetic effect directly depends on the type of poison. Phospholipase A, contained in the secret of bees, hornets and wasps, has a hemolytic effect. There is a breakdown of red blood cells. Melittin helps to increase vascular permeability, the formation of edema, the development of seizures, coronary disorders. Neurotoxin apamine affects the bulbar centers and spinal cord, is able to depress breathing. With a single bite, the concentration of the toxicant is insufficient for the development of significant changes. They occur with a massive lesion (150-200 bees).
Individual bites of poisonous insects are dangerous because of the high risk of allergies. In case of injury, a massive release of reagins, histamine and other biologically active substances occurs. The reaction can occur by the type of anaphylactic shock (violation of central and peripheral blood flow under the action of inflammatory mediators), angioedema (binding of fluid in tissues in a separate area of the body) or urticaria (increased permeability of the microcirculatory bed, which is accompanied by blocking of sensory nerve endings).
Venomous insect bites are divided by the type of animal (bee, wasp, hornet, scorpion), by the type of reaction (truly toxic, allergic), by the prevailing syndrome for truly toxic phenomena (hemolytic, neurotoxic, local symptoms). The most common classification is considered to be according to the severity of the lesion:
- Easy. It manifests itself mainly by local signs, does not lead to significant general symptoms. Develops after the bite of one or more insects with venom with moderate poisoning ability. Usually does not require medical attention. The exception is children under 1 year old.
- Medium. There are local and moderate systemic phenomena associated mainly with the neurotoxic effect of the toxicant. Moderate allergic reactions include urticaria and Quincke edema, which does not affect the respiratory tract. Disorders of the nervous system function occur with the bites of several dozen bees. Hypersensitivity reactions can develop regardless of the number of animals.
- Heavy. There is anaphylactic shock, angioedema processes that violate the patency of the VDP, as well as severe toxic reactions. The latter are characterized by pronounced hemolysis of erythrocytes, damage to the central and peripheral nervous system. They are detected after being stung by 100-150 bees or 5-10 scorpions.
Single bites of poisonous insects are manifested by burning pain that occurs immediately after the incident. After 15-20 minutes, edema of the affected area develops, hyperemia. Then the pain is replaced by itching. Unpleasant sensations completely disappear after 24-48 hours, the formed papule can persist for a week or more. When the eyes are affected, conjunctivitis, blepharitis, lacrimation are noted. The penetration of the poison under the mucous membranes leads to their pronounced edema.
Signs of a systemic reaction are dizziness, headache, photophobia, a drop or a sharp rise in blood pressure. In severe poisoning, fibrillatory twitching of skeletal muscles, convulsions, vomiting, diarrhea, pain in the heart area are observed. Vascular collapse, depression of consciousness is possible. The most unfavorable option is disruption of the respiratory center, weakening of respiratory activity, massive hemolysis and associated nephropathy.
Allergic reactions manifest themselves differently. Urticaria leads to the formation of flat-raised pink blisters on the body, resembling the consequences of contact with nettles. A symptom of Quincke’s edema is an increase in individual areas rich in subcutaneous tissue. The most dangerous type of this condition is with damage to the upper respiratory tract. There is hoarseness of voice, shortness of breath, diffuse cyanosis, sweating, anxiety. Signs of anaphylactic shock are generalized itching of the skin, a drop in blood pressure to critical values, pain in the abdomen and behind the sternum, collapse, loss of consciousness.
The most common complication is a mechanical respiratory disorder caused by angioedema. It is noted in 2-5% of people who have suffered an insect bite. It is usually easily stopped by intravenous administration of therapeutic doses of glucocorticosteroids. Leads to death only in the absence of medical care. Anaphylactic shock occurs in 0.3-0.5% of victims. It has a mortality rate of about 50% without treatment and 10-25% during therapeutic measures.
A serious complication of multiple bites is multiple organ failure, more often provoked by hemolysis of red blood cells. The remains of destroyed red blood cells clog the renal tubules, causing intracanal necrosis. Disruption of the work of other organs is caused by electrolyte shifts, pH changes, deterioration of the activity of the enzymatic apparatus. With the defeat of one or two systems, the mortality rate is about 20%, three – about 60%.
The ambulance team is engaged in making the primary diagnosis against the background of severe reactions. People with mild lesions usually seek medical assistance on their own, so the specialist performing the initial examination is a therapist or general practitioner. Differential diagnosis with allergic phenomena of other origin, snake bites, endotoxicosis caused by internal diseases is required. Necessary examinations:
- Physical. Blood pressure is normal or elevated, severe forms of the condition are accompanied by hypotension. The pulse rate is higher than normal by 10-30 beats / minute. A papule or urticaria phenomenon characteristic of most bites is found on the skin. There is a history of contact with a poisonous insect. With auscultation of the lungs and bronchi, wheezing and wheezing can be heard.
- Laboratory. Non-specific signs of inflammation are determined: an increase in ESR, a shift of the formula to the left, leukocytosis, eosinophilia of an allergic nature. The defeat of internal organs leads to an increase in the activity of liver enzymes, the accumulation of creatinine, urea. Electrolyte shifts, pH shift to the acidic side are detected.
- Hardware. It is required only for pronounced systemic phenomena. Ultrasound detects areas of kidney necrosis, an increase in the size of the liver. The x-ray may show signs of respiratory tract stenosis or pulmonary edema (infiltrative shadows, butterfly symptom). On ECG — conduction blockages, atrial fibrillation, tachycardia.
Lesions accompanied by the appearance of only local symptoms do not require mandatory medical attention. It is enough to treat the affected area with prednisolone ointment or dimethinden maleate, which has an antipruritic and decongestant effect. After contact with bees, you should remove the sting with tweezers, it is not recommended to do this with a pinch of your fingers. If the victim has systemic manifestations, it is necessary to provide him with rest and plenty of drink, call the ambulance team.
At the prehospital stage, the introduction of antihistamines and hormones is indicated. The dose of hormonal drugs depends on the severity of the patient’s condition, varies widely enough. If the attack cannot be stopped, symptomatic therapy (bronchodilators, analgesics, sedatives) and hospitalization in a toxicological hospital are necessary. Serious non—canceling edema of the URT is an indication for emergency conicotomy.
The basis of treatment is the introduction of antitoxic serum. Since there is no specific composition intended to eliminate the effects of an insect bite, an anti-lacustrine or polyvalent anti-snake drug is used. Repeated injections of antihistamines and hormonal agents, bronchodilators are indicated. For accelerated elimination of the toxicant, the method of forced diuresis and copious drinking is used. The length of stay in the hospital usually does not exceed 2-5 days.
It is carried out with anaphylaxis, multiple organ failure, angioedema, weakly amenable to drug action. In case of respiratory disorders, artificial respiratory support is performed. In case of shock, it is performed through an intubation tube, with edema of the VDP, a tracheostomy is superimposed. Hemodynamic disorders are corrected with the help of pressor amines, coronary failures may require cardioversion, the installation of an external stimulator. Benzodiazepines, muscle relaxants are used to eliminate seizures. In some cases, hemodialysis is performed.
Prognosis and prevention
With a light and moderate course of venomous insect bites, the prognosis is favorable. A high risk of death occurs only with anaphylactic shock and the development of multiple organ failure. The number of such complications does not exceed 1% of the number of bitten. Timely assistance not only allows to normalize the patient’s condition within 10-30 minutes, but also in the absolute majority of cases eliminates the need for hospitalization. The possibility of a relapse of the reaction after the end of the action of the drugs should be taken into account.
Bites of poisonous insects can be prevented by using protective clothing when hiking to their habitats (forests, fields, reservoirs). To minimize the consequences of injury during travel, you should have several antihistamine tablets and an ampoule of dexamethasone with you. To quickly neutralize allergic phenomena, the drug must be dissolved in the mouth. The therapeutic effect is achieved after 5-10 minutes, which slightly exceeds the beginning of the action of this drug with intravenous infusion.