Giardiasis is a protozoal invasion caused by intestinal giardia and occurring with signs of a functional digestive disorder. Gastrointestinal syndrome (nausea, abdominal pain, unstable stools, flatulence) is the leading one in the giardiasis clinic; intoxication, allergic, astheno-neurotic, hepatolienal syndromes may also develop. For laboratory confirmation of giardiasis, microscopic examination of feces and duodenal contents, ELISA, PCR, analysis of biopsy material is carried out. For the purpose of specific therapy for giardiasis, antiprotozoal drugs (metronidazole, tinidazole, ornidazole, etc.) are prescribed; additionally, choleretic drugs, enzymes, enterosorbents.
Giardiasis is an intestinal infection caused by pathogenic protozoa – giardia living in the lumen of the small intestine. The causative agent of infection was first described by the Russian doctor D.F. Lamb in 1859, after whom the parasite itself was named, and the disease caused by it – giardiasis. However, in Western countries it is considered that the primacy of the discovery of the causative agent of protozoal infection belongs to the French researcher A. Giard, which is why another name of the disease is adopted in the international nosological classification – giardiasis or giardiasis (giardiasis). Giardiasis is widespread everywhere: infestation with giardia of the adult population of developed countries is 3-5%, developing countries – 10-15%; children in organized groups – 30-40%. Giardiasis in children and adults is studied in the framework of pediatrics, gastroenterology, parasitology.
From the point of view of morphology, lamblia (Lamblia intestinalis, Giardia intestinalis or Giardia lamblia) are microscopic unicellular parasites belonging to the protozoan type, the class of flagellates. In the intestine, giardia can parasitize in vegetative (in the form of trophozoites) and spore (in the form of cysts) form. Trophozoites have a pear-shaped shape, a length of 18-21 microns and a width of 5-15 microns, a shell and a suction disk. Giardia nutrition is carried out osmotically, due to the absorption of products of parietal digestion by the entire surface of the body. Due to the available four pairs of flagella, trophozoites are able to perform circular or oscillatory movements. Giardia reproduce by division; every 10-12 hours the parasites are able to double. The habitat of vegetative forms of giardia is the upper parts of the small intestine. Giardia cysts are immobile; they have an oval shape, a two-contour capsule; length is 8-14 microns, width is 5-8 microns. In the form of cysts, giardia exist in the colon and outside the body, in the external environment, where they can maintain their viability for a long time.
The source of the spread of the causative agents of giardiasis is an invaded person who secretes mature giardia cysts with feces into the environment. The epidemiological role of animals that are carriers of giardia (dogs, cats, guinea pigs, rabbits, etc.) is not excluded. Mechanical carriers of pathogens can be flies, cockroaches and other insects. Infection with giardiasis occurs by the fecal-oral mechanism; by water, food, contact and household ways. The leading factors of infection transmission are unboiled water, food, hands, common items, soil contaminated with giardia cysts. The infestation of the population with giardiasis is facilitated by fecal pollution of the environment, poor water supply, crowding of people, low level of sanitary and hygienic skills of the population. Predisposing factors are age up to 10 years, hypotrophy and dystrophy, congenital anomalies of the biliary tract, gastrointestinal diseases with a decrease in acidity and enzymatic activity, gastric resection, protein starvation, etc. A surge in the incidence of giardiasis is registered in the spring-summer season.
Getting into the digestive tract, giardia cysts reach the 12th duodenum, where they turn into vegetative forms. Here, as well as in the proximal jejunum, giardia attach to the epithelial villi, causing mechanical damage to enterocytes, irritation of the nerve endings of the small intestine wall, disruption of the absorption process. The consequence of these processes is the development of gastrointestinal inflammation (duodenitis, enteritis), malabsorption syndrome, secondary fermentopathy, dysbiosis, chronic endogenous intoxication syndrome. Giardiasis can contribute to the chronization of helminthiasis and other intestinal infections (salmonellosis, dysentery, yersiniosis). It is proved that in the process of vital activity giardia secrete a toxin that has a tropicity to the nervous tissue, which explains the depressing effect on the nervous system. Due to the sensitization of the body with protozoal antigens, various allergic manifestations may develop in giardiasis, especially characteristic of children with lymphatic-hypoplastic diathesis.
Giardiasis can occur in the form of asymptomatic giardiasis (25%), subclinical (50%) and manifest form (25%). Depending on the leading clinical manifestations of manifest giardiasis , there are:
- intestinal form, including functional disorder of the intestine, duodenitis, duodenoastric reflux, gastroenteritis, enteritis;
- biliary-pancreatic form, occurring with the phenomena of biliary dyskinesia, cholangitis, cholecystitis, reactive pancreatitis;
- extra-intestinal form, accompanied by astheno-neurotic syndrome, neurocirculatory dystonia, toxic-allergic manifestations;
- mixed Thomas.
Clinically pronounced giardiasis can have an acute and chronic course.
The symptomatology of the manifest form of giardiasis consists of gastrointestinal, intoxication, allergic-dermatological, astheno-neurotic, hepatolienal syndromes. In typical cases, the incubation period is 1-3 weeks. The main clinical manifestations of giardiasis are associated with a violation of the functioning of the gastrointestinal tract, since the intestines serve as a place of parasitization of giardiasis. In the acute stage, complaints of moderate pain in the umbilical region and the right hypochondrium, nausea, belching, poor appetite, a feeling of heaviness in the stomach, bloating prevail. The stool becomes frequent up to 3-5 times a day, liquid, foamy, watery, and later – greasy; diarrhea is often replaced by constipation. The acute phase of giardiasis lasts 5-7 days; then spontaneous healing or the transition of the infection into a subacute chronic course may occur. With chronic giardiasis, weight loss, asthenization, short-term exacerbations of intestinal manifestations in the form of gastroduodenitis, eunitis, dyskinesia of the duodenum are noted.
The intoxication syndrome in giardiasis directly depends on the massiveness of the invasion, the duration and severity of the course of the disease. It can manifest itself as peripheral lymphadenitis, an increase in adenoids, subfebrility. Signs of central nervous system depression in giardiasis are irritability, fatigue, decreased performance, emotional lability, bruxism. Children may have tics, hyperkinesis, hypotonic crises and fainting states. Dermatoallergic manifestations include dryness and peeling of the skin, follicular keratosis, urticaria with itchy skin, atopic dermatitis, etc. D. Patients with giardiasis often suffer from persistent blepharitis and conjunctivitis, cheilitis; asthmatic bronchitis and bronchial asthma.
Clinical recognition of giardiasis is difficult due to the wide variety and non-specificity of symptoms. Clinical manifestations of giardiasis are often explained by other reasons, and patients are treated by a gastroenterologist, neurologist, allergist, pulmonologist, dermatologist for certain syndromes.
An objective examination of patients with giardiasis reveals pallor of the skin, overlaid tongue, bloating, enlarged liver, soreness in the mesogastric region. With the help of ultrasound of the hepatobiliary system and cholecystography, biliary dyskinesia with signs of cholestasis is detected. Changes in the hemogram are represented by eosinophilia, monocytosis. In the biochemical analysis of blood, hypogammaglobulinemia, hypoalbuminemia, and an increase in the level of alkaline phosphatase are detected. Examination of feces for dysbiosis reveals a change in the intestinal microflora: a decrease in the number of lacto- and bifidobacteria, the appearance of pathogenic microorganisms (staphylococci and streptococci, Candida fungi, etc.).
The diagnosis of giardiasis must necessarily be confirmed by the data of a parasitological examination, namely, the detection of giardia cysts in feces or vegetative forms in duodenal contents. For this purpose, microscopic examination of freshly excreted feces and smears (native and stained), duodenal probing with subsequent examination of the resulting secretion is carried out. Given the cyclical nature of the release of trophozoites and cysts with feces, it is advisable to conduct repeated studies of feces (3-5 times a month). To confirm giardiasis, the determination of giardia antigens in faeces (PCR) or specific antibodies in blood serum (ELISA), examination of biopsy material obtained during endoscopy is also used.
Giardiasis therapy is carried out in stages and consists of a preparatory period (elimination of cholestasis, endotoxicosis, mechanical removal of giardia), proper antiparasitic treatment (elimination of trophozoites and giardia cysts) and a recovery period (restoration of intestinal microflora, strengthening immunity, etc.).
The preparatory stage includes rational diet therapy aimed at creating unfavorable conditions for the reproduction of giardia in the body. Such a diet involves the use of cereals, bran, vegetables and fruits, vegetable oil; restriction of carbohydrates, mainly sugars. It is useful to carry out fasting days; tubes with mineral water, xylitol, sorbitol; taking choleretic and antihistamines.
The medical stage of giardiasis treatment is carried out with special antiprotozoal drugs (metronidazole, tinidazole, ornidazole, nimorazole, albendazole, furazolidone, etc.) and usually consists of 2 courses. At the final, restorative stage, multivitamin preparations, enterosorbents, bacterial and enzymatic preparations, plant adaptogens, immunostimulants, phytotherapy are prescribed.
Prognosis and prevention
The effectiveness of giardiasis therapy is 92-95%, however, relapses of parasitic infection or reinfection may occur in the future. For complete liberation from parasites, persistent repeated treatment is often required. Dispensary observation of patients is carried out for 3-6 months with a 2-3-fold parasitological examination. To prevent giardiasis, it is necessary to protect reservoirs and soil from contamination by parasites, control the quality of drinking water, and sanitary and hygienic education of the population. In order to break the chain of transmission of giardiasis, it is important to timely identify asymptomatic carriers and sick persons by conducting a coprological examination of children and staff of children’s institutions.