What is Giardiasis?
Giardiasis is a protozoal invasion that occurs mainly with lesions of the small intestine and is accompanied in some patients with allergic and neurological symptoms.
Giardiasis is widespread among rats, mice, rabbits, dogs, cats and other animal species. The source of infection for a person is a person who secretes Giardia cysts, and, possibly, some species of animals with which a person often contacts (dogs, cattle, pigs, etc.). The leading role as a source of invasion belongs to man. With feces, mature invasive Giardia cysts are secreted. Cyst excretion with giardiasis is intermittent and undulating, begins at 9-22 days after infection. The number of viable cysts secreted from the faeces can reach 23 million in 1 g, and an average of 1.8 million in 1 g. In experiments on volunteers, it was found that entering from 1 to 10 cyanths into the human digestive tract can lead to the development of invasion. 10 – 30% of people.
The mechanism of transmission of giardiasis is fecal-oral. Transmission factors are water, food, soil, hands contaminated with Giardia cysts; The mechanical carrier of cysts lamblia can be flies.
There is a significant contamination of environmental objects with viable lamblia cysts. IK Padchenko and I. M. Loktev found them in the water of open reservoirs (the Dnieper and Desna rivers) from 4 to 30 cysts in 1 m3, in the water of recreational zones – 2 to 10 cysts in 1 m3; in untreated wastewater – 359 -1091 cysts per 1 l; in wastewater that has undergone complete biological treatment at small-sized sewage treatment plants of the type of compact prefabricated plants before discharge into open water bodies, 10 to 35 cysts per liter; in 1 kg of sewage sludge – 2016 – 3322 cysts. The soil of preschool children’s institutions in non-canalized settlements in 11–22% of cases (of the number of samples studied) was seeded with Giardia cysts, in 1 kg it contained from 14 to 112 Giardia cysts. Significant contamination by cysts of lamblia of objects in preschool day-care institutions was revealed. So, in the washings from the door handles of playrooms and toilets Giardia cysts were found in 6% of cases, in washes from children’s hands in 3%, in pots from washes – in 2%, in washes from toys – in 0.2%. Indicates the detection of cyan Giardia in the washes from the hands of workers of the catering departments, vegetable farms. Various researchers have identified Giardia cysts in the intestinal contents and on the body surface of household insects (flies and cockroaches).
Trophozoites survive in faeces filled with saline, no more than 1–2 hours. Cysts are significantly resistant. Depending on the ambient temperature, they remain viable in the feces for 2-24 days, in water -15-70 days, in urine – 3-4 days. In the water of natural reservoirs (ponds, rivers, lakes) at a temperature of 2–22 ° C, they survive for 1-3 months, in tap water – from 28 days to 3 months, in wastewater – up to 130 days, in sea water in the south Ukraine – in the summer – 43 – 47 days, in the winter – 62 days. In soil, in natural conditions, depending on its type, degree of insolation and moisture, their viability lasts from 1 to 75 days, in mines in the absence of insolation – up to 4-5 months. Heating to 60 – 70 ° С causes the death of cysts in 5-10 minutes, and when boiling – immediately. On the surface of apples, lamblia cysts survive for 6 hours, on bread – 6 to 12 hours, in cabbage pickle – up to 24 hours, in dairy products at a temperature of 18 – 25 ° C – 12 days, and at 2 – 6 ° C – up to 112 days. On the surface of glass, metal, polymers, parchment at a temperature of 2 – 27 ° C and relative humidity of 40 – 100% of the cysts remain viable from 2 hours to 18 days. On telemuhs, cysts remained viable for 3 hours, and up to 48 hours in the intestinal contents.
In the USA, Great Britain, Sweden, Egypt, and Columbia, water flashes of giardiasis are described, in which the main factor of transmission was drinking water that did not undergo treatment and filtration in sewage treatment plants. Known cases of infection with Giardia through the water of open water bodies, pools. Water flashes can occur when surface water from the soil, animal excreta, and untreated sewage in case of accidents at sewage treatment plants gets into drinking water. During water outbreaks, a large number of people of all ages are infected, 30% of those infected with giardiasis manifestly manifest.
In children’s institutions, the dirty hands of children and, possibly, personnel, household objects and household items contaminated with parasite cysts (door handles, pots, toys, etc.) are often the main factor behind the transmission of giardiasis.
In rural areas, the factor of transmission of giardiasis can be the soil fertilized with non-disposed feces and polluted with human and animal excrement.
Food products can serve as a factor in the transfer of giardiasis when contact with the finished products of cysts Giardia from the hands of employees of food enterprises, food processing facilities if they do not comply with the sanitary and hygienic regime; when used unwashed fresh vegetables, fruits, table greens, contaminated feces of a person or animal infested with Giardia; contaminated products with flies and other household insects.
Causes of Giardiasis
The causative agent of giardiasis is the intestinal flagellate protozoan – Lamblia intestinalis (Lambl, 1859; Blanchard, 1888). In the foreign literature, the terms Giardia lamblia, Giardia intestinalis and Giardia duodenalis are used.
In the development cycle of lamblia, the vegetative (trophozoite) and cystic stages are distinguished. The vegetative stage of a pear-shaped form, symmetric, actively mobile, with a size of 10-18×6 – 12 microns, an average size of 9х12 microns. Lamblia has 2 cores and 4 pairs of harness that are organelles of motion. The front end of the body is wide, rounded, the rear (tail) is pointed. There is a suction disk on the ventral surface of the body, with which the Giardia is fixed to the epithelial cells of the intestinal wall. On the midline of the lamblia body, there are two supporting axiol threads, which divide the cell into two symmetrical halves of the same structure. Each of them has one core. The cytoplasm is transparent. The dorsal surface and the tail end of Giardia are covered with a single cytoplasmic membrane. Giardia lacks mitochondria, the Golgi apparatus, and there is an endoplasmic reticulum, where the synthesis of substances takes place in the cell most intensively.
Cysts are oval (size 8-14×7-11 microns, average 12×8 microns). Their cytoplasm contains 2 or 4 nuclei and a folded flagellate apparatus. In liquid or semi-liquid faeces, an intermediate stage in the development of Giardia, a predcist, is sometimes found.
Giardia reproduces in the places of their greatest accumulation by pair division. The division process takes 15-20 minutes, which contributes to the intensive colonization of the intestines by protozoa. In the external environment are excreted in feces mainly in the form of cysts. Trophozoites can be found only in liquid faeces in no more than 5% of persons infested with Giardia.
The place of parasitism lamblia – the upper sections of the small intestine. Giardia is attached to the mucous membrane of the front part of the body, and the back end is free. At one place trophozoites remain fixed for a short time. They are often detached from the villi and reattached to them, but in a different place or in a free state. With intensive invasion can penetrate into the tissue of the villi.
Trophozoites periodically detached from the mucosa are encysted or degenerated. Experimental studies on dogs found that 10-15 days after infection, the main mass of trophozoites is localized in the jejunum and occasionally in the duodenum. In the future, the population of lamblia moves from proximal to the middle or to the middle and distal parts of the small intestine. The formation of cysts (encystation) in the first 10–15 days occurs in the jejunum, rarely in the duodenal ulcer, and later in the middle and distal small intestine. It depends on the size of the population of lamblia, the severity of pathological changes in the place of parasitization and the duration of the invasive process. Cyst shedding with giardiasis is intermittent.
It was also found that the Giardia culture can withstand short-term freezing, without losing the ability to share. At the same time, the water temperature above + 50 ° С causes the instantaneous death of the simplest.
Giardia are the most common human parasites that inhabit the upper sections of the small intestines. Modern data on the morphological and biological features of Giardia indicate their exceptional adaptability to living in this particular area of the gastrointestinal tract.
Giardia inhabit the surface of the epithelium. Bringing individual specimens into the villus stroma, as established by Dehkan-Khodzhayeva (1960), is possible only with intensive colonization of intestinal Giardia. Indicators such as the absence of signs of reproduction of vegetative lamblia inside the villus, abrupt disturbances of their structure and lack of reaction of the surrounding tissue deny the possibility of adaptation of these protozoa to the interstitial parasitism.
Pathogenesis during Giardiosis
Swallowed cysts of L. intestinalis are exported to the initial sections of the small intestine. Giardia adapted to parasitize on the brush border of the microvilli of the small intestines, where intensive processes of enzymatic digestion of nutrients take place and most of carbohydrates, proteins, fats, vitamins, mineral salts and microelements are absorbed, from where they pump out nutrients using a central pair of strands. The consumption of nutrients by trophozoite, split in the process of abdominal and parietal digestion to monomers, occurs in pinocytic vacuoles. The final products of hydrolysis of proteins, fats and carbohydrates, accumulating in the area of the brush border in the process of parietal digestion, are inaccessible to the intestinal microflora due to the tight fit of the villi to each other. Giardia able to pump nutrients and enzymes directly from the brush border, interfering with the process of membrane digestion. Synthesis and secretion of enzymes (invertase, lactase, amylase, enterase, phosphatase, etc.) are disturbed, pathological fluctuations of their concentration in blood serum are noted. Absorption of fats, carbohydrates, proteins and vitamins, especially fat soluble, decreases, the metabolism of folic acid, riboflavin, thiamine and cyanocobalamin changes, the concentration in serum of ascorbic acid, vitamin A and carotene decreases.
Giardia mechanically block the suction surface of the villi, damage the enterocytes, repeatedly attaching to them and detaching, irritate the nerve endings of the intestinal wall, destroy glycocalyx. On 1 cm2 of the intestinal mucosa may be more than 1 million Giardia.
In the acute course of giardiasis, there is marked swelling of the stroma of the villi, melting of the basement membrane, pathological changes in the villous cover of the crypts, the mitotic division of enterocytes is activated, and areas of destroyed glycocalyx are detected. After 2 or more months after infection, edema, moderate or severe inflammatory reaction, degenerative, atrophic or motor changes are observed in the places of lamblia localization. On the surface of the brush border of the villi, C-shaped grooves are found, the shape and size of which correspond to the shape and size of the suction disk of the trophozoite.
At 10 – 12-day course of the process in the stroma of the villi and the submucosal layer of the mucous membrane an abundant productive infiltrate is found with a high content of histiocytes, plasma cells, and eosinophils. Pathological changes in other parts of the digestive tract are the result of neuro-humoral influence from the place of parasitic lamblia and absorption of the products of their metabolism and decay. Dyskinesia of the biliary tract, reactive pancreatitis, changes in the liver, stomach, and appendix have a reflex origin, aggravated by the addition of a secondary infection.
Mechanical damage to the mucous membrane of the small intestine and the destruction of glycocalyx by Giardia contributes to the inoculation of conditionally pathogenic and pathogenic microflora with the development of dysbacteriosis. The latter is manifested by a variety of microflora species composition and an increase in the number of microbial associations.
Products of metabolism and death of lamblia are absorbed from the intestine, cause sensitization of the human body, which can manifest itself in various forms of allergic reaction. Only in 40-50% of patients with giardiasis an elevated blood eosinophil content is noted.
Parasitism lamblia aggravates the course of concomitant infectious diseases: viral hepatitis, typhoid fever, dysentery, contributes to the appearance of symptoms that are not peculiar to them and to the transition to protracted forms.
Colonization of the mucous membrane of the small intestine by lamblia is accompanied by the development of an immune response (AT, complement, sensitization of immunocompetent cells), with the help of which the parasites can be neutralized and eliminated from the body. A major role in the protection of the host is played by a local immune response, characterized by the formation of specific s-IgA. Anti-lamblia-specific antigens are also found in the sera of invasive people and animals. At present, more than 20 Giardia proteins have been studied and characterized, some of which are Giardia immunodominant antigens. Immunity after suffering giardiasis is loose and unstable.
Despite the active study of the pathogenesis of giardiasis, in scientific publications, the question of the pathogenicity of Giardia is still discussed.
In some cases, the pathogenicity of lamblia is beyond doubt when their detection is supported by a specific clinical picture, which is not supported by other reasons.
The pathogenic role of lamblia in other diseases of the gastrointestinal tract, which are aggravated with concomitant giardiasis, is also proven.
However, cases of lamblia are recorded in the absence of a pathological process, in these cases they are regarded as conditionally pathogenic organisms, the degree of pathogenicity depends on a number of factors, in the presence of which asymptomatic carriage can turn into a disease – giardiasis. The factors determining the possibility of such a transition include, first of all, the presence of comorbidities weakening the carrier’s body, reduced immunoreactivity, the composition of the host intestinal parasitosis, vitamin deficiency, dietary patterns, as well as the massiveness of Giardia infection, and perhaps even the simplest virulence . The frequency of manifest giardiasis is 13-43%, subclinical – 49%, asymptomatic – 25-28% of the number infested with Giardia.
At the present stage, it should be concluded: from whatever point of view the question of the pathogenesis of giardiasis or the pathogenicity of giardia is not approached, it is necessary to carry out antimultiplication therapy when they are detected.
Symptoms of Giardiasis
Studying the clinical symptoms and functional status of the digestive system in children of different age groups on the background of Giardia infection, identified 4 main clinical syndromes: dyspeptic, pain, astheno-neurotic and allergic and dermatological. Leading in the clinical picture of the disease were dyspeptic (81.5%) and pain (76.9%) syndromes. Asteno-neurotic reactions in the form of irritability, fatigue, restless sleep, headache and dizziness were detected in 64.8% of patients.
In 31.5% of cases, clinical and laboratory signs of sensitization were detected – an increase in eosinophils in the peripheral blood to 5-7%.
Allergic dermatological syndrome in the form of atopic dermatitis was noted in 15.7% of cases.
Syndromic symptoms were recorded in various clinical forms of giardiasis.
The intestinal form of giardiasis naturally manifests itself in the form of duodenitis, duodenal dyskinesia and enteritis.
Patients complain of spilled pain in the right half of the epigastric region. There are sharp bouts of pain, accompanied by nausea. Frequent are complaints of loss of appetite, belching, heartburn, unstable chair, diarrhea, alternating with constipation.
Constant moderate pain in the navel, most often not associated with food, a feeling of fullness in the stomach, abdominal distension, liquid, sometimes foamy stools, up to 3-5 times a day, steatorrhea are characteristic of enteritis. On examination of the patient – the stomach is moderately swollen, with deep palpation painful in the navel.
In individuals infected with Giardia, hepatobiliary pathology is often detected, most often expressed by symptoms of cholecystitis.
Some authors deny the possibility of parasitism of Giardia in the gallbladder and liver ducts, however, they recognize the possibility of developing hepatobiliary and biliary-pancreatic pathology in case of Giardiasis. Such patients complain of pain in the right hypochondrium, bitter taste in the mouth, bitter eructations, and pain on palpation of the gallbladder. Positive gallbladder symptoms, the results of fractional duodunal sounding indicate dyskinetic disorders of the biliary system with spasms or atony of the sphincteropapillary region in the presence of Giardia.
The results of an ultrasound examination of the abdominal organs in children with giardiasis also indicate the pathology of the biliary-pancreatic system in the form of the hypotonia and hypertonus of the sphincter of the gallbladder, and effects of cholestasis. The principal differences of pathological changes in the digestive system in different age groups of children infected with Giardia are noted. So, in the younger group (age 2-3 years), dyspeptic and allergic dermatological syndromes prevailed, while pain and astheno-neurotic syndromes were extremely rare.
At the age of 4-7 years, dyspeptic syndrome also prevailed, however, in 75% of children pain syndrome was observed, in 50% – reactive changes of the pancreas, in 37.5% of patients the organic pathology of the gastroduodenal zone was formed.
At the age of 8-12 years, similarly to the previous groups, dyspeptic syndrome was leading, in 81.7% of patients pain was more pronounced, in 75% dyskinetic disorders of the biliary system were detected, in 70% of patients functional changes in the pancreas were observed. Organic changes in the gastroduodenal zone prevailed in 98.3%, including 4 patients with erosive and ulcerative defects of the duodenal mucosa.
At the age of 13–15 years, dyspeptic disorders remained (77.8%), however pain was the leading syndrome, i.e., the author determined the weighting of clinical symptoms in older age groups and the formation of organic pathology of the digestive system.
Giardiasis in young people (19 years old – 24 years old) most often occurs with clinical manifestations mainly from the gastrointestinal tract (duodenitis, enteritis, enterocolitis).
Prolonged parasitism of lamblia is accompanied by neurotic symptoms: weakness, fatigue, irritability, tearfulness, headaches, dizziness, pain in the heart, especially in children. In some cases, these symptoms are predominant. Against the background of Giardia infestation, the development of neuroses, which do not have specific clinical features, is possible.
Clinical forms of giardiasis with a predominance of allergic manifestations are described: invincible pruritus, urticaria, skin erythema, bronchial asthma and asthmatic bronchitis, rhinitis, arthralgia, arthritis, conjunctivitis, persistent blepharitis, etc., which passed immediately or after 1 year. metronidazole).
A significant part of invasive giardiasis occurs without any clinical manifestations (carriage) or at the subclinical level, when the patient has no complaints, and the symptoms of the disease can be detected only by instrumental studies (impaired absorption in the small intestine, changes in the content of intestinal enzymes in the blood serum and others). The frequency of manifest giardiasis is 13-43%, subclinical – 49%, asymptomatic – 25-28% of the number infested with Giardia.
Experimental studies on volunteers have shown that with the same doses of cyn Giardia being administered with food, the clinical picture has developed in 60% of people. Diarrhea, abdominal syndrome, flatulence, fever and other symptoms developed 3-10 days after inoculation of cysts, while they were cyclical, appearing and disappearing at different time intervals in different individuals. The number of cysts in the feces of the infested people also varied. The appearance of symptoms of giardiasis could be ahead of the release of cysts by 1-2 weeks. The lamblia infestation could spontaneously disappear after 6 weeks, and could persist for years. At the same time, cyst secretion occurred at 10–20 day intervals.
Diagnosis of Giardiasis
The variety of clinical manifestations of giardiasis and the absence of pathognomonic symptoms require mandatory laboratory confirmation of the diagnosis. The material of ala research are feces and duodenal contents. In the duodenal contents, only lamblia trophozoites are found, only cysts in the decorated feces, and trophozoites and cysts in the liquid and semi-shaped feces.
Clinical indications for laboratory examination to exclude giardiasis are:
- the presence of diseases of the digestive tract, their tendency to chronic course with frequent exacerbations;
- neurocirculatory dysfunction, especially in combination with the pathology of the digestive tract;
- persistent blood eosinophilia;
- allergic manifestations;
- “travelers’ diarrhea”.
A classic method of laboratory diagnosis of giardiasis is protozoological research. A microscopic examination of native and Lugol-stained smears from freshly isolated feces is carried out. Considering the cyclical release of cysts and trophozoites with feces, the insignificant periods of life of vegetative forms in the environment, it is necessary to use preservative liquids to preserve the parasite in feces (Safaralieva, Turdyeva, Barrow) and conduct multiple studies (from 2-3 to 6-7 times at intervals 1-2 days), and also use the formalin-ether enrichment method, the floating method. In most cases, Giardia cysts in the feces are detected already at the first examination. Negative periods in the allocation of lamblia can vary from 2-3 days to 2-3 weeks. Therefore, in case of suspected giardiasis, it is also recommended to conduct a protozoological examination of feces within 4-5 weeks with an interval of one week.
In duodenal contents, lamblia trophozoites are detected with greater consistency than in feces. However, when parasitizing lamblia in the middle and distal small intestine, the results of the study of duodenal contents may be negative, so it is necessary to conduct a study of feces. The study of the secret of the duodenum, obtained using a three-channel probe under vacuum, is more effective for detecting the parasite than microscopy of duodenal contents, obtained using conventional probes.
Recently, immunological methods of research are used for laboratory confirmation of giardiasis, based on detection of AH pathogen in feces or specific AT in blood serum. During reproduction of L. intestinalis in the intestine, specific GSA 65 hypertension is produced in large quantities. In feces, it is determined by the method of monoclonal AT. Specific IgM class AT can be detected in the patient’s serum by ELISA as early as 10–14 days from the beginning of the invasion, their presence in diagnostic titers indicates an acute giardiasis. The use of PCR for the detection of DNA lamblia in biological substrates is a highly effective diagnostic method, but is mainly used for scientific research.
The recognition of the correctness of the diagnosis of giardiasis in all cases of detection of giardia in feces or duodenal contents, both in cases of clinically severe and asymptomatic, determines a positive decision on the specific treatment.
However, in all cases when intestinal disorders or abnormal functions of the liver are observed in the presence of lamblia, for the timely detection of a possible primary and concomitant disease, it is necessary to conduct a thorough clinical and laboratory examination of the patient.
Tinidazool (fazizhin, amethine, tinogin). The course of treatment is 1-2 days. Preparation for treatment is the same as in the treatment with trichopol.
Daily intake: adult 2000 mg (4 tablets of 0.5 g); children – 50-60 mg per 1 kg of body weight. The daily dose is divided into 3-4 single doses and taken during or after meals.
Side effects in the form of nausea, dizziness, ataxia, leukopenia are rare.
Contraindications include: blood disorders, diseases of the central nervous system in the active phase, the first 3 months of pregnancy, lactation. Do not take with increased sensitivity.
Tiberal (ornidazole) is an antimicrobial and antiprotozoal drug.
Effective with trichomoniasis, amebiasis and giardiasis. One tablet contains 500 mg of ornidazole. Possible treatment regimens: one-day, three-day, 5-10-day courses. With a duration of treatment of 1-2-3 days, adults and children weighing more than 35 kg take 3 tablets once in the evening. Children weighing less than 40 mg / kg once a day. With a body weight of more than 60 kg, 4 tablets are prescribed per day (2 tablets each in the morning and evening).
With a 5-10-day course, adults and children weighing more than 35 kg receive 2 tablets per day, one in the morning and evening. For children weighing up to 35 kg, they are prescribed at the rate of 25 mg / kg body weight in a single dose.
Tiberal is always taken after meals.
Side effects are mild and manifest in the form of drowsiness, headache, nausea, in rare cases – disorders of the central nervous system, such as dizziness, tremor, impaired coordination, seizures, etc.
Contraindications – individual intolerance, early pregnancy, lactation period.
Effective – 90-92,5% at a one-day course.
Macmiror “Poliindustria chimica”. According to these authors, when a macromyror is prescribed in a daily dose of 30 mg / kg of body weight in 2 doses for 7 days, 96.8% of children are completely cured.
No adverse events were identified. The authors consider this drug on the effectiveness and tolerability of the drug of choice in the treatment of children.
Control parasitological examination is carried out immediately after the end of the course of treatment and after 1 month.
Prevention of Giardiasis
Preventive measures aimed at the source of infection include the identification of persons infected with lamblia among decreed contingents, children and attendants of children’s institutions, patients with pathology of the digestive tract and immunodeficiency of various origins. Identified patients and carriers are treated or sanitized.
In order to prevent the introduction and spread of giardiasis in food and similar enterprises, it is recommended that individuals who are registered for work be subjected to a protozoological examination. When the situation of intestinal infections deteriorates at the indicated enterprises, it is advisable to include a protozoological study in the complex of other ongoing clinical diagnostic examinations. Identified patients with giardiasis and healthy cyst-extractors are treated or sanitized.
Measures aimed at breaking the transmission mechanism consist in protecting the environmental objects (water bodies, soil) from contamination with invasive material, providing the settlements with good-quality drinking water and sewage facilities. In preschool, medical and preventive treatment institutions, food enterprises, strict compliance with the sanitary and hygienic regime is obligatory, as with other intestinal infections.
An important place in the prevention of giardiasis is health education. It should be carried out, first of all, in risk groups, which include, besides the listed, persons visiting endemic for parasitic diseases, including giardiasis, territories. The attention of tourists should be paid to the need to use only high-quality thermally processed food and boiled or filtered water. This will reduce the risk of infection not only giardiasis, but other infectious and parasitic diseases.