Intestinal parasitic infections: An overview

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Ramana K V. Intestinal parasitic infections: An overview. Ann Trop Med Public Health 2012;5:279-81
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Ramana K V. Intestinal parasitic infections: An overview. Ann Trop Med Public Health [serial online] 2012 [cited 2020 Aug 7];5:279-81. Available from:

Intestinal parasitic infections are responsible for considerable morbidity and occasional mortality among the infected population throughout the world. It is estimated that around 2 billion people are infected with intestinal parasites globally. [1] More than half of the infected individuals include school going age children. About 39 million disability adjusted life years (DALY’s) are linked to IPI’s which are responsible for huge financial burden. [2] Most of the parasitic infections are spread by faeco-oral route by consumption of contaminated food or water. Many parasitic infections are zoonotic, transmitted from domestic animals including cattle, sheep, cats, dog and rodents which act as reservoir. [3] Protozoan parasitic infections and intestinal helminthic infections are a common cause of parasitic manifestation in infants, children, adolescent, reproductive age and pregnant woman. Intestinal parasitic infections are a symbol of low socioeconomic status predominantly affecting poor people in underdeveloped and developing nations. The most important drawback of IPI’s is that about 90% of infected individuals remain asymptomatic. [4] The prevalence of intestinal parasitic infections varies with different geographical regions. An Indian study recently done, found higher prevalence rates (81.2%) of protozoan parasites compared to helminthes (18.8%) in contrast to studies in other parts of the world. [5],[6] Recent studies have reported Giardia lamblia to be the most prevalent protozoan followed by Entamoeba histolytica and Blastocystis hominis.[7] Among the helminthic parasites, the soil transmitted helminthes that include Ascaris lumbricoides, Trichuris trichuria and Ancylostoma duodenale are the most common. [8]Hymenolepis nana is considered the most frequent cause of tape worm infection. [7]

Poverty, illiteracy, lack of safe drinking water, poor hygiene, and malnutrition is responsible for repeated intestinal parasitic infections which lead to severe morbidity. [9] Environmental factors also play a role in the incidence of IPI as hot and humid tropical climate favor increased parasite prevalence. [10] Though age is not a factor, children are observed to be most affected by parasitic infestation. Micro and macronutrient deficiency, low birth weight, underweight can predispose to frequent IPI’s. [6] Parasitic infestation in pregnant and reproductive age population can be responsible for intrauterine growth retardation. IPI’s can be responsible for nausea, vomiting, diarrhea, malabsorption, malaise, fatigue, depression, weight loss, fever and gastrointestinal obstruction. Others including hypoprotenemia, wasting, pica and edema are observed in IPI. [7] Complications of intestinal parasitic infections include intestinal ulceration, abscesses, peritonitis and reactive arthritis or asymptomatic synovitis usually involving lower extremities. Hypersensitivity reactions seen as rashes and utricaria are common in parasitic manifestations. Parasite specific manifestations are seen in case of Ancylostoma duodenale, the hook worm aided by an organic anticoagulant can consume or suck about 0.25 mL of blood each day and be responsible for microcytic hypochromic anaemia. [11] Giardiasis can be responsible for severe malabsorption syndrome and Entamoeba histolytica infection if not treated can be responsible for intestinal and extra intestinal manifestations including amoeboma, toxic megacolon, pneumatosis coli (intramural air), peritonitis and liver abscess. [12] Large helminthic parasites can precipitate intestinal obstruction, intussusceptions and other related complications. [13] Lack of knowledge of prevalence of parasites in a particular geographical area may lead to misdiagnosis of IPI’s as appendicitis, and other inflammatory bowel diseases. [14] Treatment with steroids can exacerbate parasitic infestation. [15] Previous studies have observed the relation between micronutrient deficiencies and IPI’s in relation to Vitamin A, C, E, Riboflavin and Folic acid. [16]

Diagnosis plays an important role in IPI’s as suggested by the World Health Organization (WHO)’s 4 part strategy to control IPI’s in Diarrheal diseases control (CDD) programme. [17] Stool examination for parasitic ova, cysts, trophozoite and larvae remains the gold standard for the laboratory diagnosis for IPI’s. [18] Studies previously done have observed increased detection rates of parasites after use of concentration techniques. [19],[20] Others recommend screening of at least three stool samples for correct diagnosis. [21] Though serological tests including ELISA for the detection of antigen in stool, as well as antibody in blood/serum are available, their useful has been found to be limited except in case of extra intestinal manifestations. Usefulness of PCR in the diagnosis of parasitic infections is limited due to cost affordability in low income countries. [22]

The need of the hour is that we should have enough studies related to the epidemiology of various IPI’s in pediatric age group in different parts of the world. [23],[24],[25],[26],[27],[28],[29] Recent reports of infection with Diphyllobothrium spp and Dipylidium caninum from India highlights the need for pediatricians to make a thorough clinical evaluation taking in to consideration the prevalent parasitic infection in the particular geographical region, hygiene status, recent travel to endemic areas and other associated predisposing factors as suggested by the World Health Organization (WHO). [30] Clinical microbiologists must follow standard laboratory procedures when screening the stool samples and increase the chances of finding the parasites. The social and preventive medicine personnel should conduct visits to communities, evaluate their nutrition status (especially children and pregnant women), encourage hygiene practices, recommend consumption of safe drinking water, sensitize about the infections transmitted by domestic animals, disadvantages of illiteracy and defecation in open areas and prioritize primary health care and emphasize oral rehydration as the key and relatively inexpensive intervention for reduction of diarrhoeal disease mortality. Spread of IPI’s can be controlled by deworming and treating asymptomatic carriers. Prevention strategies include use of proper sewage disposal methods, consumption of clean and treated safe drinking water and proper hygiene (hand washing, cleaning fruits and vegetables before consumption). [31] In conclusion we reemphasize the need for a multifaceted approach considering role of epidemiological surveillance (parasitic prevalence in slum, rural and urban environments), evaluation of various factors associated with parasitic infections in respective geographical areas, formulating standard laboratory investigations to identify parasites and initiate control programmes in minimizing the morbidity and mortality caused by IPI’s.

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1755-6783.101988

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