Giardiasis is a parasitic infestation caused by Giardia lamblia (Giardia intestinalis) that occurs in the form of latent and manifest forms (dysfunction of the intestine). Human giardiasis has (...)
Giardiasis is a parasitic infestation caused by Giardia lamblia (Giardia intestinalis) that occurs in the form of latent and manifest forms (dysfunction of the intestine). Human giardiasis has been reported from all five continents and most countries in the world. Prevalence rates of infection vary between <1 and 50 %. In many developing regions where basic sanitation is lacking, Giardia infections are almost universal by two years of age. On the contrary, in developed countries the prevalence of giardiasis is only 3–7%. The disease is distributed among all age groups but mainly among pre-school children.
The main route of transmission G. Lamblia is faecal-oral. Giardia has a simple, two-stage life-cycle. After the host ingests cysts the trophozoites emerge from the cysts in the duodenum and attach themselves to the small intestinal mucosa. Since trophozoites can only localize onto the duodenal mucosa they mechanically block the mucous membrane and disturb the digestion and motor activity of the small intestine. Giardias cause absorption deterioration of fat, carbohydrates, vitamins C and B12 and secondary bacterial infection. Symptoms of giardiasis include: diarrhea, fatigue, edema, lethargy, weight loss, decreased appetite, paleness, and muscle twitching. Gastro-intestinal giardiasis manifests mainly in the form of enterocolitis with catarrhal symptoms.
Multiple facts suggest the involvement of humoral immune responses in elimination of G.lamblia. As it was shown on the human experimental infection model, the level of IgM was increased significantly by days 14-21 after infection; levels tended to fall after therapy. However, the levels of IgG remained elevated after successful treatment. IgA response was more similar to that of IgM.
The diagnosis of giardiasis is traditionally based upon clinical history, symptoms, presence of cysts in faeces or trophozoites in material retrieved from the small intestine by duodenal aspiration or duodenal biopsy. Alternative methods to the routine microscopic examination are detection of G.lamblia antigen in faeces and the measurement of levels of specific anti-Giardia antibodies in patients’ serum. Serologic testing is now regarded as a useful complement in the diagnosis of giardiasis. Besides contributing to the aid of clinical diagnosis, it could help in understanding of the status of immune responses for each individual and for epidemiological purposes.