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Information

Editors

SakariJokiranta
HeliSiikamäki
AnuKantele

Introduction to Intestinal Helminthiasis

Distribution

  • Intestinal helminths are very common parasites found worldwide (about 3 billion carriers in total).
  • Enterobiasis (pinworm/threadworm infection) Pinworm (Enterobiasis) is a common condition in children but can also affect adults. It appears that the incidence of pinworm infection has increased particularly in the industrialized countries, where other helminthic diseases are relatively rare.
  • Toxocara worms are roundworms of cats and dogs, and they are also found in industrialized countries.
  • The causal agents of soil-transmitted helminthiasis (roundworms Ascariasis, hookworms Hookworm Disease, whipworms Trichuriasis, Strongyloides Strongyloidiasis) are mainly encountered in the warm climate zones. Ascaris lumbricoides (human roundworm) is mainly encountered in Southeast Asia and China, and the other soil-transmitted helminths are encountered mainly in Africa and South America.

Transmission

Significance worldwide

  • In addition to the possible gastrointestinal symptoms, protein-energy malnutrition is the most significant health concern precipitated by the three most common helminthic diseases, i.e. ascariasis (Ascaris lumbricoides), trichuriasis (Trichuris trichiura) and hookworm infection. Trichuriasis and hookworm infection are also associated with the development of anaemia. In addition, annually over 60 000 people, mainly children, die of bowel obstruction or perforation, or biliary tract complications caused by ascariasis.

Diagnosis

  • Intestinal helminths do not cause acute diarrhoea, and their symptoms often appear weeks or months after the infection. Consequently, intestinal helminths should not be sought as the cause of acute traveller's diarrhoea. Instead, intestinal protozoans may cause diarrhoea (see Introduction to intestinal protozoal diseases Introduction to Intestinal Protozoal Diseases).
  • The basic examination in the diagnosis of intestinal helminthiasis consists of the detection of parasitic eggs and larvae, or active parasites, in the faeces (stool ova and parasites, O&P, three samples on different days).
  • Antibody assays can be considered if strongyloidiasis or toxocariasis (Toxocara) is suspected.
  • Eosinophilia is seen in some cases of intestinal helminthiasis, mainly in strongyloidiasis and toxocariasis as well as during the lung migration phase of the round worm and hookworm lifecycle. If intestinal helminthiasis is suspected to be the underlying condition behind eosinophilia, the stool is always examined for parasites; if needed, serum anti-helminth antibodies may be determined as an additional test.

Prevention

  • The following measures are available for the prevention of helminthiases in endemic areas: improvement of general hygiene, avoidance of the consumption of certain types of raw fish and uninspected raw meat, wearing of closed shoes in damp regions and avoidance of using human faeces as a fertiliser.

Intestinal helminthiasis

Disease and causative agentMode of transmissionSymptomsSuggestive findingsDiagnosisTreatment
Diphyllobothriasis Tapeworm Disease (Diphyllobothrium latum, broad or fish tapeworm)Raw freshwater fish (cod, perch, ruff, burbot)Usually no symptoms, occasionally abdominal complaints, rarely pernicious anaemiaMegaloblastic anaemia, low blood vitamin B12 levelStool ova and parasites (O&P)Niclosamide or praziquantel1)
Taeniasis Tapeworm Disease (Taenia solium, pork tapeworm and T. saginata, beef tapeworm)Faeces-intestineUsually no symptoms, but T. solium infection may result in cysticercosis with accompanying symptoms (epilepsy, other CNS symptoms; see Extra-intestinal helminthiasis Introduction to Extra-Intestinal Helminthiasis)Stool ova and parasites (O&P)Niclosamide or praziquantel1)
Dwarf tapeworm infection Tapeworm Disease (Hymenolepis nana, rat tapeworm)Faeces-soil-intestineUsually no symptoms, but may cause abdominal symptoms, particularly in autoinfectionStool ova and parasites (O&P)Praziquantel1) or niclosamide1)
Ascariasis Ascariasis (Ascaris lumbricoides, human roundworm)Faeces-soil-intestineUsually no symptoms, but may cause abdominal pain and nausea as well as respiratory tract symptoms during the lung migration phase of the roundwormEosinophilia during the lung migration phaseStool ova and parasites (O&P)Mebendazole2) , albendazole1) or ivermectin
Enterobiasis Pinworm (Enterobiasis) (Enterobius vermicularis, pinworm, threadworm )Perianal skin-mouthPerianal itch, disturbed sleep in children; the majority of infections are asymptomaticDetection of live worms with the unaided eye; detection of eggs under a microscope; examining a sample taken from the perianal areaPyrvinium or mebendazole2) , albendazole1)
Strongyloidiasis Strongyloidiasis (Strongyloides stercoralis)Soil-skinOften no symptoms. In the lung phase, there may be cough, dyspnoea. In the intestinal phase, diarrhoea, constipation, vomiting. Occasionally, particularly in hyperinfection, upper abdominal pain, diarrhoea, weight lossEosinophilia common, rash (larva currens)Stool ova and parasites (O&P), serology or Strongyloides culture.Ivermectin or albendazole1) ; screening of close contacts
Hookworm disease Hookworm Disease (Ancylostoma duodenale and Necator americanus)Soil-skinUsually no symptoms, but may cause burning upper abdominal pain, diarrhoea, anaemiaAnaemiaStool ova and parasites (O&P)Mebendazole2) or albendazole1)
Trichuriasis Trichuriasis (Trichuris trichiura, whipworm)Faeces-soil-intestineUsually no symptoms, but may cause abdominal complaints, weight loss, anaemiaAnaemiaStool ova and parasites (O&P)Mebendazole2) or albendazole1) or ivermectin
Toxocariasis (Toxocara canis and T. cati)Dog/cat faeces- intestineAbdominal painEosinophiliaAntibody assays from bloodNo well documented pharmacotherapy available
1) In some countries only under special licence
2)Mebendazole (100 mg tablets) is available only under special licence in some countries