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CHAPTER 23

Parasitic Infestations of

Surgical Importance in Children

Iftikhar Ahmad Jan
Usang E. Usang
Kokila Lakhoo

Introduction Aetiology/Pathophysiology
The term “parasitic infestation” is used to refer to those infections Amoebiasis is caused by the pathogenic Entamoeba histolytica, com-
caused by protozoa, helminthes, and arthropods. They are a major monly transmitted via the faeco-oral route when water or food contami-
cause of morbidity and mortality in infants and children. However, nated by faeces are consumed. Humans are the only reservoir and there
parasitic infestations have received relatively little attention compared are no intermediate hosts.
with infections due to viral, bacterial, and fungal agents. Upon ingestion of contaminated food or water, the cysts travel to
Parasitic infestations are a worldwide problem in children, the the small intestine, where trophozoites are released (encystation). In
prevalence and variety of organisms being greatest in areas with a 90% of patients, the trophozoites re-encyst and produce asymptomatic
warm, moist climate and in communities where standards of hygiene infection, which usually spontaneously resolves within 12 months. In
are low. But parasitic diseases are now occurring more frequently in the remaining 10% of patients who are infected, the parasite causes
developed countries due to immigration and increased foreign travel. symptomatic amoebiasis.
This cosmopolitan distribution, in addition to the complications E. histolytica causes its primary lesion in the colon, where the
that often attend these infestations, make this subject an important caecum and rectosigmoid are areas of predilection. The incubation
surgical problem. period varies from 2 days to 4 months. Invasive disease begins with
Of the parasitic diseases, those of surgical interest in children are: the adherence of E histolytica to colonic mucins, epithelial cells,
and leukocytes mediated by a galactose-inhibitable adherence lectin.
1. Protozoan infections
Following adherence, trophozoites invade the colonic epithelium to
• Amoebiasis
produce the ulcerative lesions typical of intestinal amoebiasis. The
2. Helminthic infections trophozoites of E. histolytica lyse the target cells by using lectin to
• Ascaris lumbricoides – Intestinal nematode bind to the target cells’ membranes and the parasite’s ionophore-
2+
+
like protein to induce a leak of ions (i.e., Na , K , Ca ) from the
+
• Dracontiasis (Dracunculiasis) – Tissue nematode
target cells’ cytoplasm. Numerous haemolysins, encoded by plasmid
• Malayan and Bancroftian filariae – Tissue nematode (ribosomal) DNA (rDNA) and cytotoxic to the intestinal mucosal cells,
have been described in E. histolytica. An extracellular cysteine kinase
• Schistosomiasis (Blood fluke) – Trematode
causes proteolytic destruction of tissue, producing flask-shaped ulcers.
3. Arthropodal infections Phorbol esters and protein kinase C activators augment the cytolytic
• Myiasis – Tissue-invading arthropods activity of the parasite.
Liver abscesses due to amoebiasis are 10 times more frequent in
• Chigoe (jigger) – Tunga penetrans adults than in children. Amoebic liver abscess, however, is equally
4. Hydatid disease common in both sexes among prepubertal children, probably, in
agreement with the equal distribution of intestinal disease in both sexes
Amoebiasis in children. Spread of amoebiasis to the liver occurs via the portal
Amoebiasis is a human intestinal infectious disease caused by the blood, after the pathogenic organisms have evaded the complement-
protozoan parasite Entamoeba histolytica. It is a ubiquitous parasitic mediated lysis in the bloodstream. Trophozoites ascend the portal
infection affecting approximately 10% of the world’s population and veins to produce liver abscesses filled with acellular proteinaceous
is the third most common cause of death from parasitic infections, the debris (so-called anchovy paste). The trophozoites of E. histolytica
first two being malaria and schistosomiasis. lyse the hepatocytes and the neutrophils. This explains the paucity of
Demographics inflammatory cells within the liver abscesses. The neutrophil toxins
Amoebic infections were previously reported as uncommon among may contribute to hepatocyte necrosis.
children by the World Health Organization (WHO), which described Clinical Presentation
shigella species as the most common and most important cause of The clinical presentation of amoebiasis is variable. It ranges from
dysentery in this age group. However, recent studies from Africa have asymptomatic cyst passage to amoebic colitis, amoebic dysentery,
shown that this condition is endemic, both in its invasive and nonin- amoeboma, and extraintestinal disease. E. histolytica infection is
vasive (carrier) states; it may affect any age group and has no gender asymptomatic in about 90% of cases; invasive disease occurs in the
preference in children. The reasons thought to be responsible for the remaining 10%. Severe disease is more common in children, especially
endemism include poverty, malnutrition, and poor sanitation, among if malnourished. Extraintestinal disease usually involves only the liver,
others. Amoebiasis is not uncommon even in some Western countries, but rare extraintestinal manifestations include amoebic brain abscess,
however, as a result of immigration and increased foreign travel. pleuropulmonary disease, ulcerative skin, and genitourinary lesions.