Disinsection

DISINSECTION, the extermination of ectoparasites on humans and in their environment. However, disinsection as a science is understood more broadly; it is the study of measures to combat arthropods, especially insects, that are directly or indirectly harmful to humans and their property. The harm caused directly to humans consists in the fact that these living creatures can transmit various infectious diseases to humans (typhus and relapsing fever, malaria, plague, anthrax, sleeping sickness, typhoid fever, dysentery, cholera, and other diseases). Indirect harm is caused by insects that destroy grain, flour, and bread supplies, rendering them completely unusable or turning them into a product harmful to health. The same harm can be caused by insects that damage dwellings, fabrics, clothing, household items, and finally, those that parasitize domestic animals. In sanitary practice, disinsection covers mainly the group of measures that are of interest from an epidemiological point of view. The correct implementation of disinsection is based primarily on knowledge of the biological properties of pests; this knowledge is borrowed from the fields of zoology, parasitology, and entomology, and utilizes information from climatology, botany, agriculture, microbiology, epidemiology, and hygiene. Along with this, disinsection uses information from physics, chemistry, technology, and commodity science. Measures to combat pests fall into two categories: preventive (prophylactic) measures and extermination measures. Preventive measures can include: 1) widespread dissemination among the population of knowledge about the sanitary harm of arthropods, especially insects; 2) impeccable observance of cleanliness and tidiness among people and animals and their surrounding environment; 3) proper supply of the population with items that contribute to maintaining both personal and public cleanliness (soap, water, especially hot water, as well as clothing, linen, bathhouses, laundries, etc.); 4) proper design, expedient equipment, and proper use of dwellings and buildings intended for habitation by people and animals. Extermination measures include: 1) mechanical, 2) physical, 3) biological, 4) chemical, and 5) combined methods. Mechanical methods. The simplest method of destroying insects consists of shaking and beating out suspicious things and objects, sweeping, wiping, vacuuming, thorough washing with soap, a brush with hot water, etc. These techniques, together with physical and chemical means, carried out carefully, persistently, and systematically, often yield good results; they are sometimes the only ones possible for the destruction of certain insects. Mechanical methods also include the use of various kinds of traps, sticky compositions applied to paper or fabric, followed by the destruction of the pests. Mechanical protection of premises and products from the penetration of insects is also of enormous importance, for which nets on windows, doors, and ventilation openings, covers, and storage of products in a well-closed space are used. In order to combat the reproduction of insects, it is also necessary to pay attention to the timely removal of garbage, waste, and manure, which serve as either food or a breeding ground for pests (closed bins, etc.). Physical methods. This includes the use of high or very low temperatures, air pressure, and the radiant energy of sunlight. - Action of temperature. Insects tolerate low temperatures quite well. Cooling insects to 0° and even lower shows that they retain viability, and many of them retain movement under these conditions. Only the transition to a state of complete torpor causes the death of insects, and the temperature at which this state occurs is different for different insects. The onset of complete torpor occurs: in larvae of stinging mosquitoes at -4°, in caterpillars of the clothes moth at -8°, in house flies and stinging mosquitoes at -8°, in bedbugs at -21°. Low temperature is of little use as a means of disinsection, but its use is expedient as a means of stopping their development. Insects tolerate increased temperatures worse. A temperature of 50-55°, and for practical purposes better 60-70°, is already sufficient to cause the fairly rapid death of various insects. The degree of death is influenced not only by the height of the temperature but also by the humidity conditions of the environment, the degree of nourishment of the insects, etc. Depending on the degree of satiety, lice die at the following temperatures: Temperature; Satiety unknown; Sated; Hungry. 40°; After 3 hours; After 6 hours; After 2 1/2-3 hours. 45°; After 1 1/2 hours; After 2 1/2-3 hours; After 1-1 1/2 hours. 50°; After 45 min.; After 1-1 1/2 hours; After 15 min. 55°; After 20-30 min.; After 15 min.; After 2 hours. 60°; After 2 hours; After 2 hours; Immediately. Dry hot air is more destructive to insects than moist air at the same temperature. Air heated to 50-52° is used by Americans for the purpose of disinsecting mills instead of cyanization. For sanitary purposes during disinsection, higher temperatures are used—60°, 80°, 100°, 120°—depending on the nature of the material being disinsected, the duration of action, the resistance of the insect, and the surrounding environment. Disinsection with high temperature is carried out in chambers (stationary or mobile) operating with hot air at different air movement speeds (see Disinfection chambers). Moving hot air causes faster death of insects than stationary air. - Action of solar energy. Illuminating objects with the sun and consequently warming them usually frees them from certain pests (for example, clothing from moths, grain products from insect pests). - Moist heat. Boiling, especially with alkalis, or bucking is one of the most reliable methods of disinsection. Boiling water can be used for the disinsection of floors, wooden furniture, metal beds, etc., with insects dying within 1-2 minutes. Treatment with a jet of condensing steam, released under high pressure from a locomotive, is often practiced for the purposes of thermal disinsection against granary pests. - Flowing steam (temperature at 100° and above) is a powerful disinsectant. A jet of flowing steam is used to treat cracks infested with cockroaches and bedbugs. Steam disinfection chambers find wide application for the disinsection of clothing, dresses, louse-infested linen, beds, and a whole range of household items that are not damaged by steam. - Air pressure as a means of disinsection has been little studied. In disinsection work, a vacuum is used in combination with chemical gaseous substances—cyanogen, hydrocyanic acid, carbon disulfide, chloropicrin. Finally, it is necessary to point out the direct action of flame for burning insects out of cracks with the help of, for example, so-called Swedish blowtorches (see Disinfection apparatus). Biological methods of control. By the biological method of disinsection is understood the destruction of insects with the help of other living creatures. This method is usually combined with a number of other measures based on the biological properties of insects [such as, for example, the destruction of insects by depriving them of food; in this case, it must be borne in mind that many insects (bedbugs) tolerate starvation for quite a long time]. Methods that hinder the life of larvae in places favored by insects are often used (fighting mosquitoes, the house fly, etc.). Numerous enemies of insects are also used, among which one can name mammals, birds, amphibians, predatory arthropods, and parasitic insects. Of the mammals, pigs, moles, shrews, and hedgehogs provide services to humans in the fight against certain types of insects. Bats are known as active exterminators of mosquitoes. Of the birds, domestic chickens exterminate a large number of fly larvae; cuckoos, woodpeckers, and sparrow species also very actively destroy insects and their larvae. Predatory arthropods are also dangerous enemies of many insects: the house fly in the adult stage is exterminated by spiders and house centipedes, and its larvae are devoured by the larvae of the common earwig and the house fly. - Microbes and fungi can cause mass diseases among pests (e.g., disease of flour moth caterpillars due to their infection by the bacillus B. thuringiensis). The mycological method of control is better studied (e.g., the infection of autumn flies in various stages of development by the fungus Empusa muscae Cohn, belonging to the race Mucor racemosus). Chemical methods of disinsection are the most common. They can either repel the insect with their odor or kill it. Agents that repel insects usually do not yield reliable results. Lice move freely on clothing impregnated with 10% naphthalysol. Tobacco tar is the most active. Means that kill insects (insecticides) are of much greater importance in disinsection. These agents can be divided into 2 groups: internal (or intestinal) and external (or contact). The former act through the digestive organs, the latter through the respiratory system and skin integuments. The use of one or another agent is determined by a number of factors. Insects that willingly feed on poisoned food are exterminated by internal agents. Blood-sucking insects are poisoned primarily by contact agents. The latter can also be used for the destruction of the first type of insects.

A chemical disinsection agent must 1) act in the smallest possible quantities, concentrations, and in the shortest possible time, 2) kill pests without exerting a harmful effect on other living beings, 3) not damage objects and the surrounding environment, 4) vigorously diffuse and be evenly distributed in enclosed spaces, 5) act at high and low temperatures and penetrate into the thickness of objects to a significant depth, 6) be quickly removed from objects during ventilation, 7) not leave a bad odor for a long time in disinsected objects and premises, 8) not impart poisonous properties to the disinsected objects and food products. Not all disinsection agents meet the stated requirements; among them there is a significant number of highly poisonous, flammable, and explosive substances, which require very careful handling, thorough execution of work, and proper storage. Internal chemical insecticides are used in the form of baits made from substances favored by insects. The poisonous substance is either mixed into the bait or applied to its surface with the help of sprayers. In some cases, these substances are blown in the form of powders into the places where insects are located. Among internal insecticides, one can name: phosphorus, white arsenic, sodium arsenite, Paris (Schweinfurt) green, potash, corrosive sublimate, sodium fluoride, salicylic acid, borax, boric acid, paraform. Some powdery substances, in addition to acting on the gastrointestinal tract, also release poisonous vapors or gases that can act through the respiratory system as well. External chemical agents are used in the form of liquids, or in a vaporous or gaseous state. In a liquid state, they are used for soaking (impregnation) of objects, fabrics, goods, for irrigating surfaces infested with insects, and for distribution in a thin layer on the surface of water or other liquids in order to prevent and poison insects and their larvae. For protection against damage by insects to construction timber materials and wooden parts of buildings, impregnation with chemical agents called antiseptics (see) is used. The method of impregnation is also used for the protection of museum and household items from moths and other insects (impregnation of fabrics with Eulan). For the disinsection of manure, the following are used: lime milk, bleaching powder, ferrous sulfate, cresols, resins. For the disinsection of parts of buildings and surfaces infested with insects (walls, bunks), cresol preparations (naphthalysol, nasekomoyad) are often used; sometimes Malinin's liquid, Deminsky's liquid, Panama liquid, turpentine, kerosene, xylene, acetic acid, oxalic acid, phenol, and others are also used. To combat mosquitoes and some horseflies, water surfaces are covered with petroleum, kerosene, cresols, and saprols. Agents used in a gaseous and vaporous state can be subdivided into 2 groups: 1) agents intended mainly for the individual treatment of people, animals, and objects infested with insects, and 2) agents intended for the mass treatment of objects and for ridding various premises (dwellings, barracks, lodging houses, granaries, warehouses, mills, train cars, steamships) of insects. To the first group can be assigned xylene, gasoline, ether, kerosene, turpentine, and their mixtures. To the second group can be assigned chlorine, sulfur dioxide, carbon disulfide, cyanide, chloropicrin, and others (see Disinfection agents). For the application of highly poisonous gaseous substances, special chambers must be set up (see Disinfection chambers). A special group of substances used for disinsection consists of substances serving for the coating of cracks and holes in walls, beams, ceilings, floors, tree trunks, etc. Here, the following are used: lime milk, soap emulsion, soap-alum emulsion, soap-tobacco emulsion, resins, linseed oil, aniline oil, paraffin, etc. Work with aniline oil must be performed by specially trained people with the observance of precautions. Combined methods of control. These include: 1) the use of steam together with formaldehyde at a temperature of 58-60° in Japanese chambers; 2) the Rubner vacuum-steam-formalin method at a temperature of 50-60°; and 3) vacuum in combination with other vaporous or gaseous substances (see Disinfection chambers).

Ya. Okunevsky. Grain disinsection has as its goal the destruction of pests that live in or on grain, feeding on it. This includes beetles: Calandra granaria L., Calandra oryzae L., Sitodrepa panicea L., Rhizopertha dominica Fabr., Tenebrio molitor L., Tribolium confusum Duv. and some others; moths: Tinea granella L., Sitotroga cerealella Oliv., Ephestia kuehniella Zell, Pyralis farinalis and some others, as well as mites from the family Thyroglyphidae. Some of them spend their entire life in barns, warehouses, mills, others spend the greater part of their life in premises, and the lesser part in the field. All of them cause enormous harm to the national economy, estimated at approximately 5% of all grain production. Therefore, they have received the name of granary pests (see). They not only destroy the grain but also spoil it, contaminating it with their excrement (uric acid compounds) and worsening its sanitary evaluation. In grains infested with mites, a very large quantity of Bac. mesentericus has been found; grain infested with the granary weevil leads to catarrhal diseases of the intestinal tract in horses; mealworms, entering the stomach along with bread, cause vomiting, etc. For a long time, various methods of destroying granary pests have been used, changing depending on the knowledge of the biology of the pests, familiarity with their way of life, their ecology, as well as the development of the chemical and technical industry. The entomologist Müller, on the question of fighting the granary weevil, points out that up to the present time, up to 1,800 agents have been recommended for fighting it. At the present time, the fight against grain pests is reduced to two main measures: a) the disinfection of the premises intended for grain storage, b) the disinfection of the infested grain itself. The first measure is no less important than the second, since grain often arrives from the field completely healthy and becomes infested in the granaries. Therefore, elevators and grain warehouses, taking advantage of free summer time (July-August), intensively carry out disinsection of their empty premises, in view of the fact that disinsection of grain in infested elevators is often impossible. Disinsection of premises is usually carried out by the gas method—the only one that gives a guarantee of success. Most often, sulfur dioxide is used, by burning sulfur or releasing liquid sulfur dioxide from cylinders. Specifically for elevators, an apparatus by engineer Semanov appeared recently (1925), in which sulfur burns at the expense of the O₂ of the air located in a separate silo (bin) of the elevator. 60-80 g of sulfur is taken per 1 m³. The second most common insecticide is carbon disulfide, with which it is more dangerous to work than with sulfur dioxide, since its vapors explode in the presence of fire or metal heated to red heat. Carbon disulfide is used not only for the disinsection of premises but also for the disinsection of grain. CS₂ evaporates quickly even at temperatures significantly lower than its boiling point. Its production in the USSR is very small. It is still obtained from abroad (mainly from Germany). Its application is very simple. After the premises have been cleaned of debris and sealed by plugging holes, the liquid (CS₂) is poured into vessels (trays, cups, etc.) at a rate of 60-80 g per 1 m³. The doors are tightly sealed, and the premises remain in this state for 24-36 hours, after which thorough ventilation is performed. The work is performed in gas masks. Furthermore, hydrocyanic acid and chloropicrin are used for the disinsection of premises. Hydrocyanic acid is most widely used in Germany, where there are special societies for treating warehouses, mills, etc., with it. In the USSR, it began to be used relatively recently. Hydrocyanic acid is obtained here by the usual method—the action of sulfuric acid on sodium or potassium cyanide. Doses are usually calculated by the weight quantities of cyanide salts and are in the range of 9-15 g of sodium cyanide per 1 m³; 1.5 times more acid than salts is taken, and 2-3 times more water than acid. Due to the strong toxicity of hydrocyanic acid, the use of gas masks when applying it is even more mandatory than with carbon disulfide. Chloropicrin, which has recently been spreading more and more for disinsection purposes, has also begun to be used in the USSR in recent years. This is a colorless liquid with a sharp odor, boiling at 112° and possessing high toxicity. It evaporates slowly, and therefore it has to be either heated or sprayed in tiny droplets. 10-15 cm³ of it is taken per 1 m³. Although it is poisonous, it is safer to work with it, since its smallest concentration in the air (1:1,000,000) already makes itself felt, acting in an irritating manner on the mucous membranes of the eyes and nose. Its vapors do not explode, and they can be used to fumigate premises also where carbon disulfide cannot be used. These four insecticides exhaust the main arsenal of agents used in the disinsection of granaries. As for the disinsection of the grain itself, the arsenal of agents here is even smaller. Sulfur dioxide is not used in closed premises, since its prolonged action on grain affects the taste and nutritional properties of the latter, not to mention the reduction in germination. It is used mainly in two cases—in the disinsection of corn (by the Clayton apparatus) and in the bleaching of oats and barley in America (in special towers). Hydrocyanic acid is not used, since it penetrates the thickness of the grain very insignificantly and, moreover, is easily absorbed by moist grain and subsequently released, due to which accidents can occur. It is necessary to refrain from using chloropicrin in cases where the grain cannot for some reason be subjected to good ventilation. If the latter is ensured, as for example in elevators, then chloropicrin can be used with great success, whereby the methodology of its application differs sharply from the generally accepted one—first, the space designated for receiving grain is filled with chloropicrin vapors, and then the grain is introduced. Under this condition, the gas penetrates the grain and kills the pests living in it. To avoid loss of germination, grain is fumigated only in the case when it has a moisture content of no more than 16%. Carbon disulfide is most widely used in the disinsection of grain, which does not lower either the taste properties of the bread or the germination of the grain and can penetrate into grain piled in a heap to a significant depth (up to 2 m). Finally, in elevators, equipped grain warehouses, and well-maintained farms, grain drying in dryers, where the grain is brought by special conveyors (belts), is used for the purpose of disinsection. There are very many systems of dryers, and they are becoming more and more improved. Unfortunately, they are not widespread and are not available at all elevators.