Stool examination in a patient reveals the following finding. What is the likely route of infection of this parasite?

Ans. a. Ingestion of food contaminated with egg of larva (Ref: Paniker's Parasitology 6/e p166;Jawetz 27/e p724;Harrison 19/e p1416)Elongated, barrel-shaped eggs with a polar 'plug' at each end shown here are characteristic of Trichuris egg, which causes trichuriasis via feco-oral transmission.NematodesFecal examinationTrichinella spiralisAdult wormQTrichuris trichiuraEggs (barrel shaped) QStrongyloidesRhabditiform larvaeQAncylostoma duodenale & Necator americanusEgg which may be hatched, so rhabditiform larvae can be seenEnterobius vermicularisUsually not usefulAscaris lumbricoidesEggs & adult wormQFilariasisNo roleDracunculus medinensisNo roleTrichuris trichiura (Whipworm)Adult female whipworms are approximately 30-50 mm in length; adult male worms are smaller.Anterior end of worms is slender & posterior end is thicker, giving it a "buggy whip" appearance, hence the name whipwormQ.Life cycle:Adult Trichuris worms reside in colon & cecum, the anterior portions threaded into superficial mucosaQ.Thousands of eggs laid daily by adult female worms pass with feces and mature in the soil.After ingestion, infective eggs hatch in the duodenum, releasing larvae that mature before migrating to the large bowelQ.The entire cycle takes ~3 months, and adult worms may live for several years.Clinical Features:Most infected individuals have no symptoms or eosinophilia.Heavy infections may result in anemia, abdominal pain, anorexia & bloody or mucoid diarrhea resembling inflammatory bowel disease.Rectal prolapse can result from massive infections in children, who often suffer from malnourishment & other diarrheal illnesses.Diagnosis:Characteristic 50-20-um lemon-shaped Trichuris eggs are readily detected on stool examinationQ.Barrel shaped structure seen with lightly stained mucus plugs at each poleQEgg-shell is stained brown & encloses light yellow stained unsegmented ovumQ