Parasites that cause swelling
Crooks are round worms, human parasites. Crinkles cause ankylostomiasis. They belong to the class of Rhabditea (Phasmidia), the Strongylida group.
A large detachment of nematodes having a hugeeconomic and medical significance. Nematodes with bursa - well developed and expressed copulatory bursa at the posterior end of the body of males of all species. Most (but not all) are a direct life cycle without an intermediate host + parasitization in the intestine.
Gluttonous nematodes - feed on blood and tissue fluid.
Two important parasites of man:
Ancylostoma duodenale - Africa, India, Chile and Southeast Asia.
Necator americanus - described in Brazil, then - Texas, but then found in Africa, India and Southeast Asia.
Other species: A.ceylanicum - Sri Lanka, A.braziliense - Brazil = sometimes marked in a person (mostly - in predators). A.caninum, A.tubeforme - parasites of cats - an important source of "migrating larvae" for humans.
The structure and morphology of the curved lines.
Great morphological similarity, and similaritybiology of many species within the family. Many species are rather thick, the anterior end is bent to the dorsal side - hence the name of the curve-head. Buccal cavity large and strongly sclerotized, usually armed. The pharynx works like a pump; there are strongly developed pharyngeal glands. Males have a characteristic copulatory bursa consisting of two broad lateral and one small dorsal lobes. The females are "smooth", with a conical tail. At the same time, about 5% of the daily eggs are stored in the uterus.
Differences between two genera: Ancylostoma - postpones up to 25,000 eggs per day, life expectancy - up to 5 years; Necator - up to 9,000 eggs / day for 15 years.
Both species have a similar direct life cycle, with insignificant differences.
Headlines develop and reachmaturity in the duodenum and upper parts of the small intestine of the host. Eggs are deposited in the lumen of the intestine, and at the time of exit from the host, develop only up to the stage of 4-8 cells.
In the external environment, depending on the temperature,eggs ripen and from them larvae of the 1st stage (rhabditoid) hatch out after 24-48 hours. The shell of the egg is relatively thin - moist and shaded conditions for embryogenesis are needed. Freezing or drying is detrimental to eggs; but for normal development requires oxygen - the best development occurs when the lungs enter the loamy soil.
The larva of stage 1 leaves - 2-3 days and molts inStage 2. These larvae live in feces, feeding on them. The second molt - after 5 days - infectious larva of the 3rd stage in the cover (filariform). This non-feeding stage - moves to the periphery of the faecal mass or to the soil, remaining in the capillary layer of water. They can stay alive and remain infected for up to 3 weeks (depending on climatic conditions - relatively cool temperatures are required - 17-30 degrees Celsius, at temperatures below 17 degrees, development stops) (other data - up to 18 months). Depends on the supply of nutrients. They can make vertical migrations up to 1 meter.
In wet conditions - The larva rises to the surface of the substrate and exhibits behavioral reactions - the "semaphore". rises on the tail and swingsthe anterior end is the increased likelihood of contact with the host. It remains in the shell of the previous larval stage - prevents from drying out - hides in it between the periods of rocking.
Sensitive to the presence of CO2 and temperature changes - in contact with a warm-blooded host, rapidlyleaves the larval membrane and penetrates into the covers, focusing on the temperature gradient. It is shown that lipids are also used as a stimulus for penetration. Larvae can penetrate through any epithelium, but more often attack the skin of the legs, arms, buttocks.
Necator americanus must penetrate the skin, in order to infect the host - has proteolytic enzymes in the glands of the pharynx.
Ancylostoma - penetration exclusivelymechanically; can penetrate through the skin and mucous membranes, enter the host's body with the mother's milk, and, quite possibly, can be transmitted transplacentally - however, these are rare ways of infection. If swallowed - remains in the intestines and does not migrate, finishes normal development.
Penetrating into the skin, the larvae make their way into the blood capillaries, from which they are transferred to the lungs. Having reached the lungs, the larvae break through and fall out into the pulmonary alveoli, where they undergo molting in stage 4.
After a period of development in the lungs,the stage 4 larva migrates up the trachea and is swallowed by the host, getting through the esophagus, the stomach into the small intestine or entering the air space of the alveoli - the cilia move along the respiratory vessels up to the glottis. Next - swallowing ...
In the intestine - the last molt - the adult stage. It is attached to the intestinal mucosa by a powerful buccal cavity, gnawing through the mucous membrane until blood capillary is reached - blood can suck.
In case of severe infection, the patient may lose up to 200 ml of blood / day.
From the moment of infection until the beginning of egg laying - not less than 5 weeks.
Usually infection - when walking with bare feet on infected soil. The level of soil contamination can beextremely high, especially when using human stools as fertilizers. But eggs are sensitive to urine - mixing feces with urine leads to the destruction of eggs.
A combination of low levels of sanitation and appropriate environmental conditions. Has the meaning:
• external conditions;
• life expectancy and survival of larvae and adults;
• level of soil contamination;
• soil contact with skin;
• racial affiliation of a person - white people are about 10 times more susceptible to bends;
• Hosts-there is an assumption thatThe larvae, having got into an unsuitable host, can survive in the muscles and resume normal development by eating contaminated raw meat with the appropriate host.
1. Stage of invasion or cutaneous. The penetration of larvae causes irritationskin; if the blood capillaries are not immediately found - skin migratory larvae (earth itch) can "wander" in the skin. Additionally - the probability of a secondary infection.
2. Pulmonary phase. local bleeding in the lungs. Rarely accompanied by obvious symptoms (only with severe infections - pneumonia, cough and throat disease).
3. Intestinal phase. adult parasites are usually confined to the anteriora third of the small intestine, but with severe infections can be distributed throughout the small intestine. Different levels of anemia. Depends on the patient's diet. Possible complications due to iron deficiency.
4. Severe infections. problems due to a lack of proteins- dry hair, skin and edema (edema)), decreased immunocompetence and decreased ability to produce gamma globulins (antibodies). The disease is especially difficult for children - the formation of a "hanging belly" as a result of pulmonary edema. The lack of proteins is a significant delay in the physical development of children. In the most severe cases - a fatal outcome. Complication of the disease - with a combination of malnutrition and infection with other helminths.
Pathology depends on the level of infection. For N.americanum, the correspondence is approximately the same:
• 25 parasites are asymptomatic;
• 25-100 - mean unclear symptoms, anemia;
• 100-500 - significant damage, moderate symptoms;
• 500-1000 parasites - severe symptoms with severe pathology, often fatal.
A.duodenale is a much more pathogenic parasite - 100 parasites are sufficient for serious pathology.
Presence of eggs or larvae in feces. Use of methods of concentration of eggs. There is no need to distinguish between species, especially since eggs and larvae are morphologically similar.
Differences - in the structure of oral parts of adult parasites.
Mebendazole - effective against both species (and against ascarids). Efficiency is high - enough one dose (+ inexpensive).
In addition, sufficient food is needed, providing iron ions.
Migratory larvae can also be acquired from other animals. It is possible to treat migrating larvae with thiabendazole ointment.
Basic - reduction of environmental contamination. Treatment of patients with a high level of infection. Sanitation.
So far - up to 50-60 thousand deaths per year in tropical regions.
Hypobiosis - suspended development. Larvae, priniknuv in the owner, can suspend their development, fall into a "dormant state" with the subsequent resumption of development. It is often associated with the "necessity" of preventing the next generation or eggs from entering into unfavorable environmental conditions, or providing a greater probability of meeting a potential suitable host.
Curved lines - synchronization with the seasonality of external conditions - the production of eggs in the wet season.
With hypobiosis - a decrease in the level of metabolism; can last up to 8 months. During this period, the larvae are less sensitive to the effects of drugs.