Human disease caused by parasites

• Predominant intestinal parasitesIntestinal entry and maturation

• Intestinal entry, disease elsewhereLarval stage leaves the gut

• Skin entry, gut manifestationsMature stage enters the gut

• Skin entry, disease elsewhereDisseminationFailure to complete life cycle

Predominant intestinal parasites

Intestinal worms:

ascaris lumbricoides

trichuris trichiuria taenia saginata

enterobius vermicularis

Intestinal protozoans

giardia lamblia

cryptosporidium parvumentamoeba histolytica

Human disease caused by parasites

• Intestinal entry, disease elsewhereacquired toxoplasmosishydatid disease (echinococcus)cysticercosis (taenia solium)visceral larva migrans (Toxocara canis) trichinosis (trichinella spiralis)

• Skin entry, intestinal manifestationsHookwormStrongyloidesSchistosoma mansoni

Human disease caused by parasites

• Skin entry, localized disease

Leishmaniasis

Filariasis

• Skin entry, disease by dissemination

Malaria

Trypanosomiasis

Schistosomiasis

Intestinal Parasites : mode of infection

Ingestion of cysts, oocysts or ova

Entry of larvae or oncospheres

Site of adult stage or disease

Cryptosporidium

Giardia

Amoebiasis

Intestine

Toxoplasmosis Visceral larva migrans

Trichinella Ingested Disseminated

Ascaris

Trichuris

Enterobius

Hookworm Strongyloides

through skin

Intestine

Symptoms Parasite

Abdominal pain and distension Giardia

Cryptosporidium

Amoebiasis

Ascaris, hookworm, taenia

Diarrhoea +/- malabsorption Giardia

Cryptosporidium

Strongyloides

Diarrhoea with blood loss Amoebiasis

Trichuris

Hookworm

Tenesmus, prolapsed rectum Trichuris

Intestinal parasites: Symptoms

Symptom Mechanism Parasite

Anaemia Blood loss Malabsorption Malnutrition

Amoebiasis Hookworm Trichuris S mansoni Giardia Diphyllobothrium Heavy infestation

Symptom Mechanism Parasites

Skin rash Papulovesicular Creeping eruption Peri-anal rash and pruritus

Hookworm Strongyloides Enterobius

Respiratory symptoms

Pulmonary migration

Ascaris Hookworm Strongyloides Toxocara

Intestinal Parasites : Symptoms

Intestinal Parasites : Surgical Symptoms

Symptom Mechanism Parasite

Intestinal obstruction Appendicitis Jaundice, biliary colic Prolapsed rectum Intestinal perforation and peritonitis

Worm bolus Obstruction Biliary obstruction Tenesmus, weight loss Transmural necrosis

Ascaris Ascaris Ascaris Trichuris Amoebiasis