Paediatrics: Intestinal parasites

2021-04-15 02:32 PM

Infection is usually via the faecal-oral route. Pets and livestock can be hosts.

Intestinal parasites

Infection is usually via the faecal-oral route. Pets and livestock can be hosts. Parasitic infection can mimic IBD, hepatitis, sclerosing cholangitis, peptic ulcer disease, and coeliac disease.

Presentation

  • Abdominal pain.
  • Diarrhoea; dysentery; flatulence.
  • Malabsorption and FTT.
  • Abdominal distension.
  • Intestinal obstruction.
  • Biliary obstruction; liver disease.
  • Pancreatitis.
  • Fever.

Investigations

  • Stool M,C&S for ova, cysts, parasites, and leukocytes.
  • Specific stool staining for cryptosporidiosis.
  • Stool ELISA for giardiasis and cryptosporidiosis.
  • Blood specific serology, e.g. Entamoeba histolytica.
  • Duodenal fluid aspiration for M,C&S.
  • Duodenal villus biopsy, e.g. giardiasis.

Protozoa

Giardia lamblia

  • Very common.
  • Swallowed cysts develop into trophozoites that attach to the small intestinal villi, causing mucosal damage.

Presentation

  • Diarrhoea, flatulence, abdominal discomfort.
  • Sometimes FTT.

Treatment 

Metronidazole.

Entamoeba histolytica

Symptoms are usually mild, but may cause:

  • Fulminating colitis (amoebic dysentery can mimic ulcerative colitis).
  • Intestinal obstruction due to chronic localized lesion (an ‘amoeboma’).
  • Amoebic hepatitis.
  • A liver abscess (right upper quadrant pain, fever, hepatomegaly).

Treatment 

Metronidazole.

Cryptosporidium

This organism causes a mild self-limiting illness except in immune-compromised patients, where it can cause:

  • Severe chronic watery diarrhoea, flatulence.
  • Malaise.
  • Abdominal pain.
  • Weight loss.

Treatment 

Erythromycin, metronidazole, or spiramycin.

Nematodes

Ascaris lumbricoides

The most common parasitic worm infection in humans, with up to 25% of the world’s population infected (rare in industrialized countries). They look like earthworms and can cause Loeffler’s syndrome (eosinophilic pneumonia, which can mimic asthma, also caused by the parasites Strongyloides stercoralis, and the hookworms Ancylostoma duodenale and Necator americanus. A heavy infestation can cause specific nutritional deficiencies or bowel obstruction. Infection occurs by faecal-oral transmission of eggs.

Treatment 

Mebendazole, albendazole, pyrantel pamoate.

Trichuris trichiura (whip worm) 

Lives in the colon and causes diarrhoea, abdominal pain, and weight loss.

Treatment 

Mebendazole or albendazole.

Hookworms (Necator americanus, Ancylostoma duodenale)

Infection is by larvae penetrating the skin, e.g. bare feet. The adult worms live in the intestine voraciously sucking blood leading to anaemia and hypoproteinemia.

Treatment 

Mebendazole.

Strongyloides stercoralis

  • Penetrates the skin and migrates to the lungs. Then coughed up and ingested into the gut.
  • Causes bloating, heartburn, and malabsorption.

Treatment 

Mebendazole, albendazole, or thiabendazole.

Enterobius vermicularis (thread or pinworm)

  • Very common and causes anal pruritis as females emerge and lay eggs in the perianal region.
  • Infection: occurs by faecal-oral transmission of eggs.
  • Diagnosis: is confirmed by direct visualization of worms on the perianal area or in stool, or microscopy of sellotape previously applied to the anus.

Treatment 

Mebendazole.

Cestodes (tapeworms)

  • Infection: results from ingesting undercooked contaminated pork (Taenia solium), beef (Taenia saginata), or fish (Diphyllobothrium latum).
  • Diagnosis: is by microscopy of eggs or proglottides in the stool.

Treatment 

Praziquantel.