Trichostrongyloidosis has been relatively recently considered a parasite that is extremely rare in humans. Until 1923, only a few cases were recorded in world literature in Africa, Japan and India. In 1923, the first case of trichostrongyloidosis in Europe was described.
In the following period, information on cases of registration of trichostrongylidosis in humans in different regions of the globe began to arrive systematically. In Japan, Indonesia, India, China, the index of population affliction with these helminthoses reaches 44.4%.The population in Iran, Egypt and the south of Iraq is very high. Trichostrongyloidosis is registered among the populations of many countries of America and Africa.
In the Russian Federation, trichostrongyloidoses are found almost throughout the country.
Trichostrongylus affinis, T. axei, T. brevis, T. calcaratus, T. colubriformis, T. orientalis, T. probolurus, T. skrjabini, T. virti-nus, T. species, T. lerouxi, T. capricola, T. extenuatus, Ostertagia circumcincta, O. ostertagia, Haemonchus contortus, Nematodirus spathiger, Mecistocirrus digitatus.
When washing the feces of patients treated for trichostrongylidosis, T. colubriformis was detected in 41.6% of cases;T. axei - at 12.3%;T. capricola and T. skrjabini - in 5.6%;other species - in less than 1% of cases.
Frequent registration of trichostrongylid, and in a number of regions and their wide distribution among the population, along with a whole complex of their negative influence on the human body, give grounds to believe that man is not an optional host of these helminths, as was commonly believed, but obligatory. One of the reasons to consider a person as an optional host was the rarity of cases of intense human invasion. However, studies conducted in the following years showed that intensive cases of trichostrongylid invasion occur quite often. So, in Iran, after de-worming in the feces of 124 patients, an average of 167 parasites per invasive was found. Therefore, the identification of a number of species of trichostrongylid ruminants in humans, intensive cases of invasion by them, and a pronounced clinical picture support VG Gagarin's view that gostal specificity is not a mandatory and invariable species characteristic of the parasite and can vary widely, depending on their hereditary and acquiredin the process of individual development of properties, as well as evidence of the ecological plasticity of trichostrongylid and human liability as their host.
Distribution of trichostrongylidoses - typical geogelmintoses - is limited by climatic conditions, as the embryonic development of their pathogens occurs in the external environment with the presence of oxygen, sufficient temperature and humidity. The optimal temperature for the development of eggs of many species of trichostrongylides is 20-30 ° C with a relative humidity of at least 75%. At 6 ° C or lower, eggs do not develop substantially, and in some species develop very slowly, at 10 ° C larvae hatch through 160h, at 20 ° C - after 40 h. After hatching, they must mature for a certain time before the invasive stage. Thus, at 23-25 ° C hatching of the larvae occurs after 24-40 h, and invasive they become at the end of 4 days. In general, the rate of development increases with increasing temperature. At a temperature above 32 °, the rate of development is maximal, but the percentage of death of eggs in the preinvasive stage is very high, a further increase in temperature inhibits the development of eggs. The temperature above 40 ° C is disastrous for eggs and larvae of all species of trichostrongylid;Thus, at a temperature of 55 ° C eggs and larvae die within 10 minutes.
In a laboratory experiment, a temperature of 10 ° C, the invasive larvae are maintained for 180 days. The optimum survival temperature for all eggs and larvae is 4 ° C.
Trichostrongylid eggs are very sensitive to drying, but invasive larvae are more resistant;they are in a dried state at room temperature and remain viable for several months.
At 20-35 ° C, T. colubriformis reach the invasive larva in 95-144 degree days.
The phenomenon of vertical migration of larvae along the plant stems is a biological adaptation of many species of helminths, providing a meeting with the hosts. Trichostrongylid larvae migrate up to a distance of 60 cm;It is possible for them to migrate horizontally to a distance of up to 30 cm, in the dry season the larvae on plants are not detected;With increasing precipitation, the number of larvae on plants is significantly increased. According to other data, invasive larvae may migrate to grasses, but remain in large numbers at the base of the vegetation. Only 0.8% of the total number of larvae migrate to a height of 12.5 cm from the ground, more migrates to wet leaves than to dry ones. Migration is weaker at a lower temperature, and more than 22 times less at 56% relative humidity compared to a humidity of 95%.Trichostrongylid larvae can migrate from the soil to the surface if the depth is less than 12.5 cm. Thus, larvae buried at this depth, even 10 weeks after the beginning of the experiment, were not found on the surface. Therefore, to protect the yield of larvae on the surface of pastures, it is recommended to instill feces of livestock by at least 15 cm.
In a significant defeat of the trichostrongyloidosis population in the mountain zone, along with the total infection of livestock with these helminths, factors such as favorable soil and climatic conditions fordevelopment and long-term survival of the pathogens of trichostrongyloidosis in the external environment and a significant exposure of the population with invasive material.
The highest extensive and intensive rates of invasion of trichostrongyloidosis( an average of 12.9% of the lesion and 1227 eggs in 1 g of feces) are noted in women who tend to do housework( cleaning the yard, harvesting the garden, caring forcattle, etc.) and therefore often come into contact with objects of the environment contaminated with invasive larvae of trichostrongylid( soil, vegetables, herbs).The higher invasion of women is also noted in other areas.
The coincidence of indicators of population invasion with the number of large and small cattle in households is also revealed. The least invaded trihostrongilidami residents of households, which contain one pet( 1.6% affection and 29 eggs in 1 g of faeces).With the increase in the livestock population, the invasion increases, and in households with 11 or more heads of large and small cattle, it reaches 16.9% and 306 eggs per 1 g of faeces. However, it has been established that the maintenance of livestock in households is not always the main reason for the invasion of the population by trichostrongylid. So, if households with livestock contain an average of 8.6% of invasiveness, and an average of 185 eggs per 1 g of invaders, then in households in which livestock is not kept these figures are 6% and 262 eggs, which is a consequence of soil contamination of the estate of its inhabitants, invaded trichostrongylids.
Infection of a person occurs when eating raw vegetables, greens, berries. Larvae can be introduced into the human body and hands that are contaminated by contact with the soil. Compliance with the rules of personal hygiene is a reliable way to prevent infection with trichostrongylid. Treatment of trichostrongylidosis .The fight against trichostrongylidosis and their prevention should be of a complex medical-veterinary character. The most effective in treating patients with trichostrongylidosis with anthelmintics are( as established by the authors) kombantinrin( once a day for 3 consecutive days), vermox( 2 times a day for 2 consecutive days), decaris( once a day for 2 consecutive days), with 98-98.6-87.9% respectively. Piperazine, naphthenone, diphenyl are not effective enough( 46.3-60.3%).Along with the treatment of invasive persons, it is necessary to carry out sanitary improvement of the households. Of great importance for the prevention of trichostrongyloidosis is the stabling of individual livestock in isolated premises, preventing it from entering the residential and household areas of households. When manure is used as fertilizer, it is necessary to dry it on well-packed sunny areas in summer for 2-3 weeks, and the height of the manure heap should not exceed 10-15 cm, which provides good warming up and rapid death of eggs and larvae, or manureto a soil depth of at least 15 cm, which prevents the larva from reaching the surface.