Diagnosis of helminthiases

Helminthiases and protozoosis cause significant damage to human health. The disease can manifest abdominal, allergic, anemic syndrome, chronic toxicosis, worms and protozoa can affect the tissues of the liver, lungs, bile ducts, brain, eye.

Helminthiases do not have specific symptoms, therefore the presence of a parasite can be confirmed only by laboratory and instrumental methods. Diagnosis of helminthiases may include helminthoscopy, helminthoscopy, serological methods, as well as X-rays, endoscopy, ultrasound.

Methods of diagnostics of helminthiases

The research on helminthiases is prescribed at the appearance of characteristic clinical symptoms and on the basis of an epidemiological anamnesis (keeping animals in the house, visiting infected areas, possible consumption of contaminated meat or water). Laboratory diagnostics of helminthiases can be carried out for several hours or days, depending on the type of parasite that is supposed to trigger the onset of symptoms.

Parasitological methods can be direct, that is, they consist of the detection of a parasite, its fragment or larva, or the use of immunological methods that allow detection of the helminth in the larval stage of development, in the phase of migration, parasitizing only the male, non-invasive infestation, and also if the worm the reproductive function has died down or has not yet developed.

Examination of feces

In the diagnosis of helminths, great importance is given to coprological examination, since most worms parasitize in the intestine, and their eggs are excreted together with feces. The fecal masses are examined in a macroscopic and microscopic manner.

With the help of a macroscopic method, helminths or parts thereof are found in feces. In a Petri dish or a small flat capacity, the feces are mixed with water and examined through a magnifying glass. With sufficient light on a dark background, white worm fragments can be found. All suspicious inclusions are transferred onto a slide with glycerin for further consideration under magnification.

To detect the part of the helminth, the method of settling can also be used. Feces are mixed with water and allowed to stand, then drain the water. After several settling, when the water is already clear, the liquid is poured and the pellet is examined in a Petri dish. When microscopic excrement for the eggs of the worm, air bubbles, plant cells, spores and pollen of plants, particles of undigested food can be taken.

In case of doubt, repeated tests should be performed. The methodical guidelines developed in 2013 establish the order of application of the sampling method and describe the methods of laboratory studies of biomaterial that allows using the most modern methods for laboratory diagnostics of helminthiases and protozooses and correctly decipher their results.

The microscopic method helps to identify the larvae of parasites or their eggs. The most applicable and affordable is a native smear, which allows you to see eggs and larvae of all worms. A small amount of the stirred feces is applied to a slide, lubricated with glycerin, and examined with a slight magnification.

Enrichment methods

The methods use the fact that, having a different weight, the larvae of the parasites float to the surface of the physiological solution or, conversely, settle to the bottom. If the eggs are heavier than the liquid, they accumulate in the sediment (the method of sedimentation makes it possible to reveal the eggs of trematodes), and if it is easier, the eggs float (the flotation method allows you to see eggs of a whisker, a dwarf chain, ankylostomide).

The methods of sedimentation and flotation are effective, since it is possible to find even a small number of eggs

The Füleleborg method

In a glass jar, place 2-5 g of feces and pour in saline (400 grams of salt per liter of water), then stir and allow to settle. After 45 minutes, the resulting film is placed on a slide with glycerin. Another way to put the film on the glass: top up the water to the brim and cover with a glass slide.

In salt water, eggs pop up and they can be seen in a microscope, but in different helminth eggs the eggs rise to the surface of the liquid at different rates (dwarf chain after a quarter of an hour, ascaris after one and a half to two hours, and only after 2-3 hours). In addition to the surface film formed, it is also necessary to investigate the sediment, since the eggs of thiidides, trematodes, and ascarids drown at a given salt solution concentration.

Advantages of this method is its availability, low cost and high efficiency, so it is often combined with a native smear. Among the shortcomings of this method of diagnostics of helminthiosis, it is possible to distinguish the need for studying the surface layer and sediment, and also for a long time for settling.

The Kalantaryan Method

Also involves the use of a saturated solution of sodium, but only a lower relative density (kilogram of sodium nitrate salt per liter of water), which leads to the emergence of most helminth eggs, so it is not necessary to consider sediment.

The disadvantages of this method of diagnostics of helminthiases include the need to use a large amount of sodium and nitrous acid, in addition, oncospheres of thienid and the trematode eggs do not rise to the surface. If the solution lasts longer than 1-2 hours, then the eggs of some worms swell and precipitate.

Goryachev's method

Assumes the precipitation of eggs. The solution is isotonic in the container. In a separate jar, the faeces are mixed with water, filtered through gauze, and poured over saline so that two layers are obtained. After 2-3 hours, the layer with feces is removed with a pipette, and the second layer is left for another 12-20 hours or placed in a centrifuge.

The sediment is poured onto a slide and examined in a microscope. This method was proposed to search for the causative agent of opisthorchiasis and was more informative than microscopy of the native smear or the method of Füleleborn, however, it is almost not used because it is technically complex.

The Krasilnikov method

Surfactants, which are part of detergent powders, release the eggs of worms from feces, and thus contribute to their precipitation. Ten grams of detergent is dissolved in a liter of water. Pour the solution into a glass jar, add the stool and mix.

A solution of several layers is formed in a solution in a day. Large particles settle on the bottom, helminth eggs concentrate in the middle layer, grayish flakes rise up. For the study, 2-3 drops of liquid from the second layer are pipetted.

The Krasilnikov method makes it possible to diagnose any kind of helminthiasis, however, it takes a long time

Ether-vinegar method

It makes it possible to identify even small eggs of trematodes, intestinal worms and protozoan cysts, it is also used to determine the intensity of infestation. Feces are placed in a container with acetic acid and mixed until homogeneous, then filter, pour into a second test tube and add ether. All is shaken and placed in a centrifuge. The resulting upper layer is removed, and the precipitate is applied to the slide and examined under a microscope.

Search for live larvae

Twisting by Shulman allows to detect in the feces of live larvae of worms (in particular, strongyloid). For analysis, only fresh feces are taken. He is lowered into a glass jar with saline solution, and stir in circular motions, without touching the walls. Eggs and larvae of parasites concentrate in the center. After mixing with a glass rod (which was interfered with), smears are made on the slide.

The Berman method

Uses that the larva moves towards the heat. With the help of this diagnostic method, it is possible to identify srongyloidosis. So, 20-50 grams of feces are put on a metal net and put it in a funnel into which warm water is poured (40-50 ⁰С). The larvae move from the stool into the water. They leave to settle for 3-4 hours. Stagnated liquid is placed in a centrifuge, and then examined.

Harada and Mori Method

This method is recommended by WHO for the detection of ankylostomiasis in humans and is carried out if necessary to differentiate ankylostomosis from non-carotenosis. A half-kilogram of feces is applied to the center of the filtered paper. Then the paper is lowered into a test tube in such a way that the clean end is in the water, and the upper part is fixed with a stopper, while the feces do not touch the water. The tube is placed in a thermostat for 5-6 days. During this time, the filariform larvae settle and can be seen through a magnifying glass.

Verification of perianal scrapings

This method is used to detect eggs of pinworms and bovine chain. It involves checking for perianal flushing or scraping. The material is collected in the morning before the act of defecation (in girls and before urination) or in the evening, 2-3 hours after the patient fell asleep. In children, the sample can be taken after a day's sleep.

For the scraping, a cotton swab or a stick can be used, as well as an adhesive tape. A cotton swab is carried out in the area of ​​perianal folds and near the anus. A stick with a tampon is lowered into a test tube and sent to a laboratory. The lab technician makes smears on slides and microscopes them.

The method of perianal scraping is widespread, because it is easy to use and allows you to assemble material for study at home

Graham's method or adhesive tape

It is also effective, because it allows to diagnose ascariasis and to detect oncospheres of decidia. To collect the material, a transparent adhesive tape 4-5 cm long is used. Its sticky side is touched to perianal folds, quickly removed and glued to a slide. The advantage of the method is that you can store the sample for a long time.

Additional ways

Laboratory diagnostics of helminthiases may include:

• examination of intestinal contents. Larvae and eggs of worms that colonize the liver, gall bladder, pancreas and duodenum can be seen in bile and intestinal contents. Samples for examination are taken during duodenal sounding. With the help of the obtained materials, it is possible to diagnose opisthorchiasis, fascioliasis, clonorchosis, dicrocelia, ankylostomidosis, strongyloidiasis;
• urinalysis. The method makes it possible to detect eggs with schistosomes. To conduct the test, you need 50 ml of urine collected in the middle of the day, pour into a conical glass and let stand for half an hour. Then the urine is drained and the pellet is placed in a centrifuge;
• sputum examination. When examining a sample of sputum through a microscope, you can see the eggs of the pulmonary fluke (paragonal), the grubs of the ascaris, the necator and strongyloid, fragments of the echinococcal bladder;
• blood test. When the biomaterial is colored according to Romanovskii, it is possible to identify larvae of nematodes parasitizing in the subcutaneous tissue. Blood should also be taken at night, since larvae are noticeable when certain tropical filariasis only when a person rests. The analysis of blood for helminthiases is also informative because it shows a reduced amount of eosinophils, which indirectly indicates the presence of worms in the body.

A urine test can detect a worm that causes urogenital schistosomiasis

Serological methods

Immunological examination is carried out with suspicion of severe tissue helminthiases and trematodes. With the help of ELISA, echinococcosis, trichinosis, alveococcosis, toxocarosis, cysticercosis, opisthorchiasis, fascioliasis, clonorchiasis are detected. With helminthiasis, the blood level first increases the IgM titer level, and then the IgG titer, which indicates active infection.

Differential diagnosis of helminthiases IgG (kach), is effective not only in the detection of ascarids, but also for the detection of protozooses (protozoa), which are equally capable of damaging the body. The method of the indirect hemagglutination reaction (RNGA) allows to detect opisthorchiasis, echinococcosis, alveococcosis, trichinosis.

Echinococcosis and alveococcosis can also be detected using the latex agglutination reaction (RLA), and cysticercosis and trichinosis will confirm the ring-precipitation reaction (PEP). These methods are used in the event that other more simple methods can not prove the presence of the worm in the body.

Instrumental methods

To identify some helminthiases in humans, affecting individual organs, instrumental studies are conducted:

• X-ray;
• Ultrasound;
• CT scan;
• Magnetic resonance imaging;
• endoscopy.

These diagnostic methods can also be used to assess the severity of helminth infection of internal organs. In rare cases, it is possible to see the worms themselves, more often the study is conducted to detect nonspecific signs of infection (an increase in the affected organ, a violation of the contraction of the gallbladder, the appearance of cysts).

With the help of laboratory diagnostics of helminthiases, it is possible to detect the parasites themselves fragments, eggs or larvae, which allows to establish an accurate diagnosis and to prescribe adequate treatment

The blood test for helminthiases is less informative, since it indicates only the development of the body's immune response, which means that the invasion was, but when exactly it is not known.

How to pass the analysis on the definition of a particular type of helminth, the treating doctor will tell.

As a rule, special training is not required (venous blood is given on an empty stomach, material for the study of feces is taken from three different places and stored no longer than 8 hours). If the worms are not detected worms, it does not mean that they are absent in the intestine and, most likely, repeated tests of feces will be carried out.