Parasitic organisms: Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) Parasitic Organisms NEMATODESNematodes – roundworms – ROUNDWORMS Organism Description Epidemiology/Transmission Pathogenicity Symptoms Ancylostoma -Necator Hookworms Found in tropical and subtropical Necator can only be transmitted through penetration of the Some are asymptomatic, though a heavy burden is climates, as well as in areas where skin, whereas Ancylostoma can be transmitted through the associated with anemia, fever, diarrhea, nausea, Ancylostoma duodenale Soil-transmitted sanitation and hygiene are poor.1 skin and orally. vomiting, rash, and abdominal pain.2 nematodes Necator americanus Infection occurs when individuals come Necator attaches to the intestinal mucosa and feeds on host During the invasion stages, local skin irritation, elevated into contact with soil containing fecal mucosa and blood.2 ridges due to tunneling, and rash lesions are seen.3 matter of infected hosts.2 (P) Ancylostoma eggs pass from the host’s stool to soil. Larvae Ancylostoma and Necator are associated with iron can penetrate the skin, enter the lymphatics, and migrate to deficiency anemia.1,2 heart and lungs.3 Ascaris lumbricoides Soil-transmitted Common in Sub-Saharan Africa, South Ascaris eggs attach to the small intestinal mucosa. Larvae Most patients are asymptomatic or have only mild nematode America, Asia, and the Western Pacific. In migrate via the portal circulation into the pulmonary circuit, abdominal discomfort, nausea, dyspepsia, or loss of non-endemic areas, infection occurs in to the alveoli, causing a pneumonitis-like illness. They are appetite. Most common human immigrants and travelers. coughed up and enter back into the GI tract, causing worm infection obstructive symptoms.5 Complications include obstruction, appendicitis, right It is associated with poor personal upper quadrant pain, and biliary colic.4 (P) hygiene, crowding, poor sanitation, and places where human feces are used as Intestinal ascariasis can mimic intestinal obstruction, fertilizer. bowel infarction, intussusception, and volvulus. Hepatic and pancreatic ascariasis can mimic biliary colic, acute Transmission is via the fecal-oral route.4 acalculous cholecystitis, hepatic abscess, acute pancreatitis, and ascending cholangitis. Appendicular ascariasis can mimic appendicular colic, appendicitis, appendicular gangrene. Gastric ascariasis can mimic pyloric obstruction.6 Capillaria philippinensis Fish-borne nematode Although rare in the US, it is more Ingested larvae reside in the human small intestine, where Diarrhea, anorexia, malaise, and vomiting.4 common in Asia (Thailand and the the female deposits eggs, which then develop, causing (P) Philippines)4 autoinfection and hyperinfection.4 Capillariasis can mimic IBD and other causes of protein losing enteropathy.6 Infection occurs from eating raw or undercooked fish containing larvae. Enterobius vermicularis Pinworm Compared to other intestinal parasites, Eggs are deposited around the anus by the worm. Some infections are asymptomatic. the transmission of pinworm is limited Autoinfection occurs due to scratching the perineal area, The most common worm because their eggs are unable to survive then thumb-sucking or nail-biting. Pinworms reside in the Symptoms may include itching and irritation. Occasional infection in children ages in the environment. The main routes of intestine but can migrate to distant organs.4 migration of the worm to distant organs can cause 5-10 in the US infection are autoinfection from eggs or dysuria, vaginal discharge, enuresis, and peritoneal larvae deposited on the anus, granulomas.4 (P) contamination from bed sheets, clothing, door handles, and inhalation of eggs from Enterobiasis can mimic hemorrhoids and IBD.6 Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 1 Parasitic Organisms NEMATODES – ROUNDWORMS Organism Description Epidemiology/Transmission Pathogenicity Symptoms hands, bed mattresses, or dust. As a result, infections tend to be limited to families and individuals in close proximity, like nurseries and boarding schools.7 Spread by overcrowding and poor hygiene. Strongyloides stercoralis Soil-transmitted Endemic to the tropics and temperate Infection occurs from skin penetration where the organism Most patients have subclinical or asymptomatic nematode subtropics where poor sanitation then travels systemically (blood, lung, GI tract).8 infections. They are commonly chronic and longstanding facilitates fecal contamination. Also found due to the autoinfective lifecycle.4 (P) in poorer areas of the US: Appalachian Strongyloides stercoralis is unique among nematodes mountain communities, Kentucky, and infections in humans because larvae passing in the feces can Irritation, edema, and urticaria at the site of skin rural Tennessee.1 give rise to a free-living generation of worms. The potential penetration.8 for autoinfection exists if larvae attain infectivity while in the Transmission is from contaminated soil.8 host.4 Diarrhea, constipation, abdominal pain, anorexia. Dry cough, tracheal irritation, recurrent asthma.8 Strongyloidiasis can mimic IBD and eosinophilic enterocolitis.6 Trichuris trichiura Whipworm Found in areas where human feces is used A human host consumes eggs, sometimes in food. Once the Mild infections are usually asymptomatic. Heavy worm as fertilizer. Found in the tropics and eggs are ingested, the larvae hatch in the small intestine. burden causes painful defecation with mucus, water, and Soil-transmitted places with poor sanitation. From there they migrate to the large intestine, where the blood (Trichuris dysentery syndrome). Rectal prolapse is nematode anterior ends lodge within the mucosa. This leads to cell also seen.9 Transmitted via the fecal-oral route.4 destruction and activation of the host immune system, The third most common recruiting eosinophils, lymphocytes, and plasma cells. This Children develop iron deficiency anemia, growth roundworm in humans4 causes the typical symptoms of rectal bleeding and retardations, and impaired cognitive development.4 abdominal pain.9 (P) Trichuriasis can mimic IBD, bacillary dysentery and acute intestinal amebiasis.6 Pathogen (P), Potential pathogen (PP), Non-pathogen (NP)2 2 Parasitic Organisms CESTODESCestodes – tapeworms – TAPEWORMS Organism Description Epidemiology/Transmission Pathogenicity Symptoms Dipylidium caninum Dog (or cat) tapeworm Human infection is rare but can occur in Fleas ingest D. caninum eggs. Adult fleas are ingested by pets Most are asymptomatic. When present, symptoms include those who kiss or are licked by their and establish in the small intestine where the eggs develop weight loss, colic, and vomiting.11 (P) infected pets.10 into the adult tapeworm. The tapeworm sheds proglottids, which are found in the stool. Humans are infected by accidental ingestion of infected dog or cat fleas.10 Diphyllobothrium latum Fish tapeworm D. latum occurs in freshwater fish After ingestion, in humans the adult helminth can live up to Mostly asymptomatic, but signs and symptoms can include throughout much of the northern 20 years in the small intestine. It adheres to the mucosa and nausea, vomiting, diarrhea, abdominal pain, and weight (P) hemisphere; intermediate hosts include can eliminate millions of eggs each day. Diagnosis is made loss.11 bears, pigs, cats, dogs, foxes, and wolves. by the demonstration of eggs or proglottids in the stool.12 Can cause megaloblastic anemia.6 Humans become infected after eating raw or undercooked fish.11 Hymenolepis diminuta Rat tapeworm Human infection with H. diminuta is rare Once ingested, H. diminuta grows to adult form and sheds Infection is usually asymptomatic, though may cause with only a few hundred cases reported, eggs through the stool. It attaches to the mucosal surface of abdominal pain, diarrhea, and irritability.14 (P) mainly in children. the intestine and grows to approximately 20-50 cm. in H. diminuta is prevalent worldwide in length. temperate to tropical conditions with poor sanitation.13 H. diminuta infection requires an intermediate host (usually rodents, but also insects). Humans become infected by ingesting food contaminated with larvae, or by direct hand contact.14 Hymenolepis nana Dwarf tapeworm H. nana is one of the most common H. nana eggs are immediately infective when passed through Symptoms include abdominal pain, diarrhea, anorexia, parasitic tapeworm infections worldwide, the stool and cannot last more than 10 days in the weight loss, malnutrition, and anemia.18 (P) found mainly in children. environment. It does not require an intermediary host Once ingested, larvae penetrate intestinal villi and develop and can be transmitted human to human, into adults that measure 15-40 cm. in length. Eggs pass into though rodents can also carry H. nana.15 stool or can reside within the intestinal villi and cause continual autoinfection.17 It has fecal-oral transmission from food and water in areas of poor sanitation.16 Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 3 Parasitic Organisms CESTODESOrganism – TAPEWORMS Description Epidemiology/Transmission Pathogenicity Symptoms Taenia spp. Organism TapewormDescription ThisEpidemiology/Transmission tapeworm is found in people who Ingested parasite cystsPathogenicity reach the intestine and develop into The adult tapeworm stageSymptoms is relatively innocuous and does have traveled outside of the US where the adult tapeworms, releasing motile segments and/or eggs in not have human pathogenic effects.