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Symptoms of giardiasis
Last reviewed: 07.07.2025

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Giardiasis symptoms are very diverse, as a rule, they are non-specific and are one of the ways to determine the form of the disease. Clinical forms of giardiasis are also variable - from intestinal to anemic, the diversity is associated with the high prevalence of this disease. Giardia (L. Intestinalis) parasitize in the small intestine, more precisely in its upper sections.
Symptoms of giardiasis appear when microscopic flagellate parasites, diplomonads Giardia Lamblia - intestinal lamblia, enter the body and settle in the human intestine. The parasites cannot penetrate the bloodstream, but their ability to inhabit the lumen of the upper part of the small intestine and feel comfortable there is quite enough for them. It is clear that the residence of such an "uninvited guest" in the intestine does not pass without a trace.
Previously, it was believed that protozoan parasites were able to penetrate the gallbladder and liver, later, through experimental studies, it was proven that bile is an uncomfortable and toxic environment for lamblia. Lambliasis, the symptoms of which directly depend on the number of infecting parasites, usually develops asymptomatically in the initial stages. Clinical manifestations correspond to the current state of the digestive tract and the activity of the immune system. However, even an insignificant number of parasites that have infected the body can quickly multiply due to provoking carbohydrate foods or low acidity in the gastrointestinal system. Statistics claim that the predominance of protein products in the diet significantly reduces the risk of contracting lambliasis.
Giardiasis is classified as follows:
- Asymptomatic form – carriage.
- The clinically manifested form is giardiasis itself as a disease.
Forms of giardiasis and their main symptoms
Giardia enter the intestines as immobile cysts protected from external influences, which then transform into a mobile and proliferating vegetative form of trophozoites. It is the trophozoites that attach to the intestinal mucosa (including the duodenum) and begin to feed intensively and multiply rapidly, forming valuable colonies. Then the cycle of their immobility begins again, during which some of the trophozoites transform into cysts and end up in the large intestine, from where they can “break free,” that is, leave the body with feces. And so on in a circle…
While trophozoites are in the human intestine, they manage to cause a lot of symptoms, although, as infectious disease doctors claim, in almost every fourth case of lamblia invasion, the disease is asymptomatic (the so-called latent lambliasis). According to WHO, the global scale of lamblia infection is up to 20% of the population, among children under 7 years old - almost 30%.
There are two main forms of giardiasis: acute and chronic.
Clinical forms of giardiasis
- Intestinal form – dyspepsia, bowel movement disorder (constipation or diarrhea), secondary malabsorption, flatulence, often nausea and general fatigue. Often intestinal giardiasis manifests symptoms as false appendicitis.
- Hepatobiliary form – decreased, insufficient secretion of bile (cholestasis), biliary dyskinesia (dyskinesia of the bile ducts) with all the accompanying symptoms – spastic pain, nausea up to vomiting, pain in the right side of the epigastrium, radiating to the scapula or shoulder. Often in this form, giardiasis manifests symptoms as typical gastroduodenitis or pancreatitis.
- Asthenoneurotic form – all neurological symptoms: signs similar to the manifestation of vegetative-vascular dystonia, headache, sleep disturbances, weight loss, fatigue.
- Allergic form (toxic-allergic) - rashes on the skin, urticaria, atopic dermatitis, all signs of an allergic reaction up to Quincke's edema.
Giardiasis, the symptoms of which are non-specific, is difficult to diagnose at the initial stage of infection, since the complaints presented by patients are extremely similar to the signs of classic intestinal, liver or neurological pathologies. The only relatively characteristic symptom of giardiasis may be chronic digestive disorders. Gastroenterologists specify suspicions of giardiasis using anamnestic information, laboratory diagnostics, including serological research methods, complete blood count, biochemical analysis of blood serum and coprological examination. Also, clinical signs of the disease are specified by the method and routes of invasion by giardia.
The mechanism of the invasive process and associated symptoms of giardiasis:
- If a healthy organism is infected by water or food, through contaminated food or water, cysts of the parasites penetrate the gastrointestinal tract, turning into trophosates (vegetative form) in the small intestine. Vegetative forms of lamblia attach to the walls of the small intestine and begin to develop. Lamblia feed on their entire surface, and also excrete waste products (protozoan excrement). Such lambliasis has weakly expressed symptoms, since the entire process occurs against the background of a relatively healthy organism.
- If a person with chronic gastrointestinal diseases gets infected, giardiasis symptoms are more pronounced. The intestinal wall, which is not healthy initially, is already affected by erosion of varying degrees of severity, giardia aggravate the erosive process, causing inflammation. Often, malabsorption syndrome develops - a decrease in the activity of absorption of lipids (fats), vitamins, which dissolve only in the lipid membrane, proteins and glucose.
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The most common symptoms of giardiasis
- Signs similar to avitaminosis, since the body stops receiving the required amount of vitamins A, E, D and the antihemorrhagic vitamin K.
- Symptoms of hypoglycemia due to glucose deficiency include fainting, dizziness, weakness, and tremors in the limbs.
- Anemia and general exhaustion up to cachexia due to poor absorption of proteins or its complete absence.
- A significant decrease in immune activity due to a disruption in the process of forming immune antibodies with the help of proteins.
- Dysbacteriosis and chronic diarrhea (up to five times a day).
- Symptoms of cholecystitis or pancreatitis. Often this stage is accompanied by radiating pain to the right side of the body, yellowing of the whites of the eyes, hepatomegaly (enlargement of the liver).
- Allergic reactions are explained by intoxication of the body with the waste products of parasites. This stage is accompanied by allergic rashes, urticaria, and Quincke's edema is possible.
Giardiasis, the symptoms of which may become more obvious as the disease progresses, can last for years. Clinical manifestations are not characteristic and specific for this disease.
Acute giardiasis
Acute giardiasis usually manifests itself 7-10 days after infection, but the incubation period can last for a whole month. Diagnostically significant symptoms of giardiasis include:
- diarrhea (loose stools);
- abdominal cramps and bloating;
- nausea;
- vomiting;
- increase in temperature;
- pain in the epigastric region;
- increased fatigue and general malaise;
- decreased appetite and weight loss.
It should be borne in mind that diarrhea with giardiasis is abundant, watery, foul-smelling, has a yellowish color, and may contain mucus. And feces with giardiasis have a pale color, a sharp odor, and are oily. All this is a typical sign of steatorrhea, that is, increased excretion of fats from the body, caused by a violation of their absorption in the intestine (malabsorption).
Not everyone experiences a rise in temperature with giardiasis, and if it does, it does not last long and, as a rule, does not exceed +37.8-38°C.
Pain in giardiasis - in the epigastric region, closer to the right hypochondrium - can be nagging or sharp, but always cramping. Often they can even be mistaken for pain in appendicitis. In addition, increased pain in giardiasis is provoked by food with a high fat content.
Chronic giardiasis
Chronic giardiasis develops from an untreated acute form, which could be asymptomatic. The symptoms of giardiasis in the chronic form of the disease are as follows:
- periodic diarrhea alternating with constipation;
- flatulence;
- belching of something rotten or bitter;
- nausea;
- pain in the epigastric region;
- yellow coating on the tongue;
- poor appetite;
- decreased hemoglobin levels in the blood (anemia);
- paleness of the skin;
- headaches and dizziness;
- increased irritability, feeling of fatigue, restless sleep.
Infectious disease specialists and gastroenterologists also differentiate intestinal, hepatic and biliary-pancreatic forms of giardiasis. In intestinal giardiasis, the symptoms are similar to inflammation of the duodenum (duodenitis) or inflammation of the small and large intestines (enterocolitis). The hepatic form of giardiasis has a clinical picture of inflammation of the gallbladder (cholecystitis) and inflammation of the bile ducts (cholangitis). And for the biliary-pancreatic form, manifestations of signs of inflammation of the pancreas (pancreatitis) are characteristic.
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Giardiasis and allergies
The ability of Giardia to cause an allergic reaction in the body should be considered separately. And here's why.
In addition to the already listed symptoms, in almost 40% of cases of the chronic form of this parasitic disease, symptoms of giardiasis on the skin may appear. In addition, there is often a cough with giardiasis, almost similar to asthmatic bronchitis.
Doctors deal with intestinal manifestations using stool tests (and, if necessary, the contents of the duodenum) for the presence of trophozoites and cysts of lamblia - to confirm the suspected invasion. But when, against the background of all intestinal symptoms, rashes with lambliasis or acne with lambliasis occur, it is necessary to conduct a serological study with intradermal tests, that is, to determine the presence of IgM and IgG antibodies in the blood serum. If antibodies are detected, then patients can call their disease serological lambliasis, although doctors do not have such a term.
Why does a rash appear with giardiasis, reminiscent of a rash with rubella and representing atopic dermatitis? Accompanied by severe itching of the skin, urticaria with giardiasis is an allergy. And increased sensitivity of the body (sensitization) links giardiasis and hair loss, and peeling of the skin, and inflammation of the ciliary edge of the eyelids (blepharitis).
The products of lamblia's vital activity, the destroyed shells of cysts resembling the chitin of arthropods, the iron-sulfur proteins produced by mitosomes, as well as the protein substances of lamblia cell membranes create a powerful "springboard" for the response of the human immune system to foreign protein components. And then we see the external manifestations of this reaction: a rash with lambliasis and a cough with lambliasis.
Consequences and complications of giardiasis
The consequences of giardiasis occur in the absence of treatment. And if the disease is detected and adequate therapeutic measures are taken (taking drugs such as Metronidazole, Tinidazole, Albendazole or Nitazoxanide), then in a week the person will be completely healthy.
But the complications of giardiasis, which has become a chronic disease, are very serious. Colonization of the intestines - especially with weakened immunity - leads to inflammation of the intestinal mucosa and atrophy of their villi, which causes a violation of intestinal absorption. Because of this, weight loss occurs and well-being worsens.
Some studies have shown that giardiasis should be considered as a cause of vitamin B12 deficiency due to problems caused in the intestinal nutrient absorption system. And deficiency of this vitamin is known to cause persistent iron deficiency anemia.
Therefore, if an adult or a child has symptoms of giardiasis, or signs resembling it without pronounced symptoms, it is necessary to undergo an examination and free the body from parasites.
According to statistics, subclinical giardiasis is detected randomly in 45-49% of patients during a comprehensive examination of the abdominal organs and instrumental methods of examining the intestine. Giardiasis, the symptoms of which are clearly manifested, is diagnosed in 15-35% of the total estimated number of infected patients. Symptoms of dyspepsia are typical for children under 12-15 years old, in older groups, typical signs of giardiasis are pain syndromes in the epigastric region. In middle-aged and elderly people, giardiasis symptoms are allergic and neurological in nature. There are frequent cases of self-healing without drug exposure aimed at the invasion. In addition, activation of immunity in the complex treatment of the main or concomitant diagnosed disease can contribute to the cure of undetected giardiasis. Also, independent neutralization of giardiasis invasion can occur due to the restoration of normal acidity of the stomach and intestinal microflora.
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