Trichuris suis

Trichuris suis is a species of whipworm that is classified within the Nematoda phylum. It can be found in warm tropical regions throughout the world but is rare in arid regions. Males reach an average body length between 1.1 and 1.5 inches, while females reach an average length between 2.3 and 3.1 inches. This species, and other members of the Trichuris genus, was given its common name because of its whip like appearance. The original definitive hosts of this species are pigs, but it is able to infect other species including humans.

Unlike other parasitic worms, Trichuris suis is directly infective and does not require an intermediate or secondary host to mature and breed. Its life cycle begins when eggs are deposited within feces. The larvae within the eggs develop for three weeks to two months after being released from an infected animal. If the eggs are in an unsuitable environment, they may not hatch, but the stage one larvae within them are resilient and can live for several years within their protective shell. Once the eggs are consumed, the eggs move through the stomach and into the small intestine, where they will hatch as stage on larvae. The larvae then penetrate through the mucosa of many areas including the cecum, distal ileum, colon, and crypts of Lieberkühn in the distal ileum. In these areas, the larvae molt four times until they have developed into adult worms. Once maturity is reached, the worm’s thicker front ends will protrude from many areas in the digestive system, but most commonly the proximal colon and cecum.

Pigs that are infected with Trichuris suis display symptoms like anorexia, diarrhea, anemia, emaciation, dehydration, and poor growth. Juvenile pigs may experience anemia, dysentery, and death. In humans, infection is rare and is not long lasting. Diagnosing pigs with an infection can be difficult and requires a series of fecal floatation tests. In many cases, a diagnosis cannot confirm an infection until the host has died and an expert has conducted a necropsy. There is no cure for infections in pigs, although the drug Piperazine can be used to minimize the symptoms. Medicines like Ivermectin, Febantel, and Doramectin can be used to treat human infections. In order to prevent infections in the hosts of this species public education, good hygiene practices, and removal of infected feces are needed.

Although Trichuris suis infections are dangerous to pigs, a study conducted at the University of Iowa has shown that the worm could be used to effectively treat Crohn’s disease in humans. After only twenty-four hours of infection, patients showed a positive response rate of almost eighty percent and a remission rate of almost seventy-three percent. Crohn’s disease causes over reactive Th1 pathways, which can be calmed when the worms limit Th1-type inflammation. Because of this, and other findings, the FDA has approved the use of Trichuris suis as an Investigational New Drug, which can be tested on humans.

Image Caption: Trichuris Suis. Credit: Universidad de Córdoba/Wikipedia  (CC BY-SA 3.0)