Trichuriasis is a nematode infestation caused by the whipworm Trichuris trichiura. It is mainly found in the soil of tropical and subtropical countries, especially in suburban or rural areas where sanitation practices are suboptimal. Trichuriasis also occurs in the southern United States.
According to the Centers for Disease Control and Prevention (CDC), there are approximately 800 million people infected with whipworm globally. Coinfection with two other common soil-transmitted helminths, roundworms (Ascaris lumbricoides) and hookworms (Necator americanus and Ancylostoma duodenale), is common. Children living in endemic regions are commonly infected with all three, which has a significant negative impact on their nutritional status and intellectual, cognitive, and educational development. At least one of these three soil-transmitted helminths infects more than one billion people currently, and hence they are responsible for a major disease burden worldwide.
Trichuriasis is spread person-to-person through ingestion of whipworm eggs. Infections are caused by contamination of soil with infected feces, as may occur where human feces is used as fertilizer or improper waste disposal systems exist. The absence of a safe water supply, consumption of improperly washed or cooked food, and poor hand hygiene practices also contribute to infection.
Following ingestion of eggs, T. trichiura larvae hatch and mature within 30 to 90 days and usually inhabit the cecum, although in heavy infections, worms may be present throughout the colon from the cecum to the rectum. Adult worms live one to two years with females laying 2000 to 30 000 eggs daily. Light infection of trichuriasis is usually asymptomatic. Slow bleeding from the worm attachment site may lead to anemia. In children with heavy Trichuris infection, symptoms of chronic colitis, including abdominal pain, mucoid diarrhea, iron deficiency anemia, growth retardation, and finger clubbing may be present. A distinct clinical syndrome known as Trichuris dysentery syndrome is a rare but more serious complication of heavy infection. It occurs more commonly in children and is manifested as tenesmus, chronic mucoid diarrhea, anemia, protein malnutrition, and rectal prolapse.
Ascariasis The presence of a large volume of adult Ascaris worms in the intestine causes abdominal distension and pain from intestinal obstruction, intussusception, and volvulus. In severe cases, bowel infarction and perforation ensues with the resultant peritonitis. Hepatobiliary and pancreatic ascariasis occurs if the adult worms block the ampullary orifice of the common bile duct. Severe nutritional deficiencies, especially protein, iron, and vitamin A, result from stealing of the human host's nutrition and impaired gastrointestinal absorption.
Of note, during the larval migration through the lungs, eosinophilic pneumonitis, known as Löffler syndrome, could be a presenting syndrome.
Hookworm infestation The main differentiating feature of hookworm (Ancylostoma braziliense and other animal hookworms) from other soil-transmitted helminths is that it is acquired by skin penetration from walking barefoot on contaminated soil. At the site of skin penetration, there is pruritic dermatitis (known as ground itch) or subcutaneous migration. Peripheral eosinophilia may be present. The hookworms attach to the intestinal mucosa and suck human blood through the mucosa. The most serious effects of hookworm infection are chronic blood loss leading to iron deficiency anemia and protein energy malnutrition.
Pinworm infestation Enterobiasis, known as pinworm infection, is caused by a small, thin, white roundworm known as Enterobius vermicularis. The cardinal symptom of enterobiasis is severe perianal itchiness (pruritus ani), especially during the night when the female worms are migrating toward the anus to lay eggs. Scratching causes eggs to be deposited under the fingernails, which could be a possible route of autoinfection or transmission to others. Diagnosis cannot be made by routine stool examination because pinworm eggs are not released into the feces. Instead, a clear cellulose tape is applied to the perianal region and then is transferred to a slide to look for eggs under a microscope, known as a Scotch tape test. Notably, autoinfection and reinfection are very common in patients with pinworm infection.