Helminth infections

Helminths, i.e., parasitic worms, are a group of macroparasites encompassing a variety of species that can infect their hosts in three different ways: ingestion of eggs or larvae (e.g., via contaminated food and water or fecal-oral route), direct penetration of the skin, and via the bite of vectors (e.g., certain species of flies and mosquitoes). Helminths are classified based on their macroscopic appearance as nematodes (i.e., roundworms; genera include Toxocara, Enterobius, Trichuris, Ascaris, Trichinella, Strongyloides, Ancylostoma, Necator, and Dracunculus), cestodes (i.e., tapeworms; genera include Taenia, Dibothriocephalus, and Echinococcus), or trematodes (i.e., flukes; genera include Schistosoma, Metorchis, and Fasciola). Most helminth species colonize the gastrointestinal tract of their hosts, causing symptoms such as abdominal pain, nausea, and diarrhea. The larvae of certain helminth species, such as those of the Ascaris and Ancylostoma genus, migrate from the intestines via the portal vein to the lungs, potentially causing asthma-like symptoms (e.g., dry cough, wheezing). Other species, such as Taenia solium, can colonize other human tissue, such as the brain or liver, which can lead to life-threatening complications (e.g., neurocysticercosis). Diagnosis of helminth infection is primarily based on evidence of eosinophilia in the blood and direct detection of worms, eggs, or larvae in stool samples. Serum IgE levels are often elevated. Treatment consists of anthelmintic agents, such as albendazole or praziquantel.

See also “Echinococcosis,” “Schistosomiasis,” and “Strongyloidiasis.” See “General parasitology” for an overview of all parasites.

Nematodes (roundworms) are long, thin, unsegmented, tube-like worms with a longitudinal digestive tract opening at both ends. Adult worms form separate sexes, with the males usually being smaller than the females. Filarial Nematodes are thread-like nematodes. They are transmitted by arthropod vectors.

eating a Toxic TrEAT: Toxocara, Trichiniella, Enterobius, Ascaris, and Trichiuris are transmitted by ingestion.

SANd on your Shins, Ancles, and Neck: Strongyloides, Ancylostoma, and Necator penetrate the skin while walking on sand.

The OWL bites: Onchocerca, Wuchereria, and Loa loa are transmitted by bites.

• Pathogen
  • Ascaris lumbricoides (giant roundworm)
  • Ascaris are nematodes.
• Epidemiology: : most common helminth infection worldwide (mainly affects children in tropical countries with low standards of hygiene)
• Mode of transmission: : fecal-oral (infection occurs in the larval state following the consumption of contaminated food, especially raw vegetables that have been contaminated by human waste used as a fertilizer)
• Life cycle: Host ingests eggs → Eggs hatch and release larvae → Larvae invade intestinal walls → Larvae migrate to lungs via portal vein → Larvae migrate into alveoli, trachea (“tracheal migration”), and larynx → Larvae are expectorated into the mouth and swallowed back into the intestine → Larvae return to the intestine → Larvae mature into adult worms, which then lay new eggs.
• Clinical features
  • Most patients are asymptomatic.
  • Early symptoms
    • Dry cough, blood-tinged sputum, wheezing
    • Loeffler syndrome: a transient respiratory disorder characterized by accumulation of eosinophils in the lungs due to certain infections (usually parasites) or allergic reactions to drugs. Symptoms are usually mild and resolve spontaneously
  • Late symptoms; : anorexia, abdominal discomfort, nausea, vomiting, and diarrhea
  • Additional symptoms due to blockage by adult worms depend on the location of the obstruction:
    • Bowel obstruction, especially at ileocecal valve (may lead to intestinal perforation)
    • Obstruction of the appendix → features of appendicitis
    • Obstruction of biliary and pancreatic ducts → features of cholestasis, pancreatitis
• Diagnostics ^[1]
  • CBC shows eosinophilia. ^[3]
  • Confirmatory test: Stool samples show worms or visible oval eggs with a knobby appearance under the microscope.
• Treatment ^[2]
  • Preferred
    • Albendazole (off-label) ^[2]
    • OR mebendazole ^[2]
  • Alternative (all off-label): pyrantel pamoate, ivermectin, nitazoxanide
• Prevention ^[2]
  • Proper disposal of human feces
  • Thoroughly wash and cook vegetables.
  • In high-prevalence areas, chemoprophylaxis for high-risk individuals ^[4]

• Pathogen
  • Enterobius vermicularis (pinworm)
  • Pinworms are nematodes.
• Epidemiology ^[5]
  • Most common helminthic infection in the US
  • Prevalence in the US: ∼ 12%
  • Primarily affects children 5–10 years of age
• Mode of transmission
  • Initial infection: fecal-oral
  • Reinfection: digital-oral after scratching anal region
• Clinical features
  • Anal pruritus (especially at night)
  • Vulvovaginitis, especially in children
  • Occasionally, symptoms of intestinal infection (i.e., nausea, vomiting, and abdominal pain which may become severe enough to mimic appendicitis)
• Diagnostics ^[1]
  • Tape test: microscopic detection of oval eggs (ova) and/or pinworms on tape that has been pressed against the perianal region
  • Stool examination is not recommended because eggs and worms are rarely found in stool.
• Treatment ^[2]
  • Mebendazole (off-label) ^[2]
  • OR pyrantel pamoate (off-label) ^[2]
  • OR albendazole (off-label) ^[2]
• Prevention ^[2]
  • Consider treating the whole household to prevent reinfection.
  • Encourage
    • Daily hygiene (e.g., bathing, nail clipping, handwashing)
    • Frequent washing of bedding and underwear

Enterobius commonly manifests with perianal pruritus.

• Pathogen
  • Trichuris trichiura (whipworm)
  • Whipworms are nematodes.
• Mode of transmission: : fecal-oral
• Life cycle: Host ingests eggs → Eggs hatch and release larvae in the small intestine → Larvae mature into adult worms in colon → Adult worms lay eggs, which are shed in feces.
• Clinical features
  • Mostly asymptomatic
  • In children: severe infection causes diarrhea, iron deficiency anemia, growth retardation, rectal prolapse
• Diagnostics ^[1]
  • Microscopic examination of stool for eggs ^[1]
  • Proctoscopy or colonoscopy may reveal adult worms.
• Treatment ^[2]
  • Mebendazole ^[2]
  • OR albendazole (off-label) with or without ivermectin (off-label) ^[2]
• Prevention ^[2]
  • Proper hygiene and disposal of human waste
  • In high-prevalence areas, chemoprophylaxis for high-risk individuals ^[4]

• Pathogen
  • Toxocara canis (dog roundworm), Toxocara mystax/Toxocara cati (cat roundworm)
  • Toxocara are nematodes.
• Mode of transmission: : fecal-oral (ingestion of Toxocara eggs from an infected dog or cat feces, e.g., in contaminated playground sand or garden soil) ^[6]
• Incubation period: 2–4 weeks
• Clinical features
  • Visceral toxocariasis (also called visceral larva migrans): caused by larvae migrating through the intestinal wall into the blood and reaching other organs
    • Fever and flu-like symptoms
    • Additional symptoms depend on the affected organs
      • Liver: hepatomegaly and abdominal pain
      • Lungs
        • Dyspnea, wheezing, cough, pneumonia
        • Loeffler syndrome
      • Skin: rash
      • Heart: myocarditis
      • CNS (also called neural larva migrans): seizures, coma
  • Ocular toxocariasis (also called ocular larva migrans): caused by larvae migrating into the eye
    • Unilateral impairment or loss of vision and resulting strabismus
    • Leukocoria
    • Inflammation, scarring, and possible detachment of the retina
• Diagnostics ^[1]
  • CBC: leukocytosis with eosinophilia, anemia
  • Hypergammaglobulinemia (↑ serum total IgE)
  • Serology: ELISA for Toxocara antibodies in serum or vitreous fluid
  • Advanced imaging (e.g., ultrasound, CT, MRI) may show diffuse nodular lesions on the liver.
• Treatment ^[2]
  • Albendazole (off-label) ^[2]
  • OR mebendazole (off-label) ^[2]
  • Specialist consult (e.g., ophthalmology) depending on affected organs
• Prevention ^[2]
  • Proper disposal of animal feces
  • Deworm animals regularly.

• Pathogen
  • Trichinella spiralis and other Trichinella spp.
  • Trichinella are nematodes.
• Mode of transmission
  • Consumption of undercooked meat (especially pork) containing encysted larvae
  • Fecal-oral (rarely)
• Life cycle: Host ingests meat that contains cysts → Larvae invade the small bowel mucosa → Larvae develop into adult worms → Adult worms release larvae, which then migrate to muscles, where they encyst.
• Incubation period: 7–30 days ^[7]
• Clinical features
  • Intestinal phase : abdominal pain, diarrhea, nausea, and vomiting
  • Muscle phase
    • Myositis: myalgia, muscle swelling, weakness
    • Periorbital edema
    • Other symptoms include: fever, rash, splinter hemorrhages, retinal and conjunctival hemorrhages, chemosis
• Diagnostics ^[1]
  • CBC: eosinophilia
  • Elevated muscle enzymes (e.g., ↑ creatine kinase, ↑ lactate dehydrogenase)
  • Serologic testing for antibodies
  • Rarely: muscle biopsy
• Treatment ^[2]
  • Albendazole (off-label) ^[2]
  • OR mebendazole (off-label) ^[2]
  • Consider corticosteroids if symptoms are severe.
• Complications
  • Cardiac: ECG changes (e.g., arrhythmias)
  • CNS: meningitis, encephalitis
  • Pulmonary: myositis involving respiratory muscles, pneumonia
• Prevention ^[2]
  • Cook food thoroughly.
  • Known exposure in the previous 6 days: prophylactic treatment

Consider trichinella infection in patients with myositis, periorbital edema, and eosinophilia.

• Pathogen ^[8]
  • Human hookworms: Ancylostoma duodenale and Necator americanus
  • Zoonotic hookworms, i.e., cat and dog hookworms ; (Ancylostoma braziliense; and Ancylostoma caninum) can also infect humans.
  • Hookworms are nematodes.
• Mode of transmission: percutaneous penetration of larvae (primarily via the feet, e.g., while walking on a beach)
• Life cycle
  • Human hookworm: Soil is contaminated with human feces containing hookworm eggs → Eggs hatch and release larvae → Larvae penetrate skin (usually the feet) → Larvae migrate to lungs via blood and lymphatic vessels → Larvae migrate via bronchi and trachea to the larynx → Larvae are expectorated and swallowed back into the intestine → Larvae mature into adult worms that colonize the intestinal tract → Female hookworms lay eggs in the intestine → Eggs are eliminated with the feces.
  • Zoonotic hookworms are usually unable to break through the basement membrane; after entering the human epidermis (humans are accidental intermediate hosts) → Migration through the epidermis for several weeks.
• Clinical features
  • Cutaneous symptoms
    • At entry site: pruritus, erythema, maculopapular rash
    • Cutaneous larva migrans (CLM): serpiginous marks (cutaneous lesion with a progressive, creeping, snake-like border) representing larval tracks
  • In zoonotic hookworm infections, only cutaneous symptoms are present.
  • Respiratory tract: dry cough, wheezing, Loeffler syndrome
  • Intestine: abdominal pain, weight loss, nausea, vomiting, diarrhea
  • Microcytic anemia (hookworms ingest blood from the intestinal wall)
• Diagnostics ^[1]
  • Human hookworms
    • CBC may show eosinophilia and microcytic anemia. ^[9]
    • Microscopic examination of stool for eggs ^[10]
  • Zoonotic hookworms: clinical diagnosis based on visualization of cutaneous larva migrans
• Treatment ^[2]
  • Human hookworm
    • Albendazole (off-label) ^[2]
    • OR mebendazole (off-label) ^[2]
    • OR pyrantel pamoate (off-label) ^[2]
  • Zoonotic hookworms (cutaneous lava migrans)
    • Albendazole (off-label) ^[2]
    • OR ivermectin (off-label) ^[2]
• Prevention ^[2]
  • Proper disposal of human and animal waste
  • Wear shoes to protect feet from exposure to soil.
  • In high-prevalence areas, chemoprophylaxis for high-risk individuals ^[4]

Consider hookworm infection in patients who present with a history of recent travel to a tropical country and microcytic anemia.

• Pathogen: Loa loa, a filarial nematode ^[11][12]
• Mode of transmission: bite from Chrysops (deer fly), horse fly, mango fly
• Life cycle: Introduction of larvae into bite wound → Larvae mature into adult worms → Adult worms reside in subcutaneous tissue, migrating through the body and causing symptoms → Adult worms produce microfilariae and release them into the bloodstream, where they are ingested by a female fly during a blood meal → Microfilariae mature into larvae, thus completing the cycle.
• Incubation period: 3–5 months
• Clinical features
  • Most infected individuals are asymptomatic.
  • The two cardinal manifestations are:
    • Calabar swelling: transient, localized swellings found commonly on the arms, legs, and around joints, which can cause pruritus and local pain
    • Ocular manifestation (eye worm): Loa loa has a tendency to migrate to the subconjunctival tissue of the eye where it causes self-limiting congestion, pruritus, and pain.
• Diagnostics ^[13]
  • Initial test: CBC may show eosinophilia.
  • Confirmatory tests
    • Blood smear: detection of microfilariae
    • Visualization of adult worms in subcutaneous tissue or conjunctivae
• Treatment: diethylcarbamazine (off-label; prescribed by a specialist) ^[2]
• Complications
  • Encephalitis
  • Cardiomyopathy
  • Nephropathy
  • Arthritis
  • Lymphadenitis
• Prevention
  • Prevention of insect bites ^[14]
  • Weekly prophylactic diethylcarbamazine for long-term travelers in endemic areas ^[15]

• Pathogen: Onchocerca volvulus ^[11][16]
• Mode of transmission: bite of the female blackfly
• Life cycle: Host is bitten by blackfly → Larvae are introduced into bite wound → Larvae mature into adult worms that reside in subcutaneous or intramuscular tissue → Adult worms produce microfilariae → Microfilariae migrate through subcutaneous tissue, causing clinical symptoms → Female fly consumes microfilariae during a blood meal → Microfilariae mature into larvae, thus completing the cycle.
• Clinical features
  • Ocular onchocerciasis
    • Keratitis
    • Uveitis
    • Optic atrophy
    • Onchochorioretinitis
    • Ocular lesions can progress to blindness (hence the common name river blindness)
  • Onchocercal skin disease
    • Onchocercomata (subcutaneous nodules): deep, nonpalpable nodules containing adult worms that are found over various bony prominences
    • Generalized pruritic lesions
    • Hyperpigmented papules (sowda)
    • Skin atrophy (due to loss of skin elasticity)
    • Hanging groin
    • Depigmentation (leopard-skin appearance)
  • Systemic manifestations
    • Allergic reactions to microfilariae may occur
    • Weight loss
    • Generalized musculoskeletal complaints (e.g., back and joint pain)
    • Inguinal and femoral hernia
• Diagnostics ^[1][17]
  • Skin snips (gold standard): superficial skin biopsies are taken from an inflamed area and incubated in saline, causing microfilariae to leave the skin sample. Microfilarial load can be determined microscopically.
    • At least two specimens are sampled and examined for motile microfilariae.
    • Specimens of subcutaneous nodules can also be sampled and examined for adult worms.
  • Slit-lamp examination: investigation of choice for ocular onchocerciasis
  • Mazzotti test: a provocative test that involves administering diethylcarbamazine (DEC) to induce microfilarial death and exacerbate symptoms. A positive test is highly suggestive of onchocerciasis.
  • Serology: unreliable for diagnosis as it cannot distinguish between active and past infection
• Treatment ^[2]
  • Microfilariae: ivermectin ^[2]
  • Macrofilariae (adult worms): doxycycline (off-label) ^[2]
• Prevention ^[2]
  • Prevention of insect bites
  • Mass treatment programs in endemic areas

Treating patients with onchocerciasis and loiasis coinfection places patients at risk for fatal encephalopathy; consult infectious diseases to help guide management. ^[1]

Everything turns black in onchocerciasis: black flies, black skin nodules, black vision (blindness).

Treat rIVER blindness with IVERmectin.

• Pathogens
  • Wuchereria bancrofti: a nematode; responsible for most cases of lymphatic filariasis worldwide
  • Brugia malayi and Brugia timori: found in Asia
• Mode of transmission: female mosquito bite (Aedes, Mansonia, Anopheles, and Culex)
• Incubation period: 9–12 months
• Life cycle: Mosquito introduces filarial larvae into host via bite wound → Larvae mature into adult worms that reside in the lymphatic system → Adult worms produce microfilariae (the blood circulating stage of filariasis-causing roundworms) → microfilariae move throughout vascular and lymphatic system → microfilariae are consumed by a female mosquito during a blood meal → microfilariae mature into larvae, thus completing the cycle.
• Clinical features
  • Fever
  • Painful lymphadenopathy (due to worms invading lymph nodes, causing inflammation) ; and retrograde lymphangitis → lymphedema with disfiguration of the lower extremities (elephantiasis)
  • Hydrocele
• Diagnostics ^[1]
  • Blood smear obtained at night (with Giemsa stain or H&E stain): detection of microfilariae
  • Serology: elevated levels of antifilarial IgG4
• Treatment ^[2]
  • Diethylcarbamazine (off-label; prescribed by a specialist)
  • Diethylcarbamazine can worsen eye disease in onchocerciasis and/or loiasis coinfection.
• Complications ^[1]
  • Lymphedema
  • Hydrocele
• Prevention ^[2]
  • Prevention of insect bites
  • Mass treatment programs in endemic areas

• Definition: a parasitic infection caused by Dracunculus medinensis
• Epidemiology: endemic in West, Central, and East Africa
• Etiology: Dracunculus medinensis
• Hosts: copepods (intermediate host), humans (definitive host)
• Mode of transmission
  • Mainly consumption of water contaminated with infected copepods (water fleas)
  • Consumption of raw infected aquatic animals (e.g., fish, frogs) can also lead to infection.
• Pathophysiology: Ingestion of contaminated water or food → dissolution of infected copepods in stomach acid → release of D. medinensis larvae → penetration of stomach and intestinal wall → dissemination of larvae throughout the abdominal cavity and retroperitoneal space → maturation of larvae and copulation → migration of female worms to skin surface (approx. 1 year after infection; male worms die) → induction of painful blister by female worm (from which it emerges to release eggs upon contact with water)
• Clinical features: symptoms typically appear after 12 months ^[18]
  • Systemic: fever, generalized pruritus, urticaria
  • Gastrointestinal: nausea, vomiting, diarrhea
  • Dermatological: painful papule, edema, blistering and/or ulcer where the worm emerges (usually on the legs and feet)
• Diagnostics: clinical diagnosis based on skin blister and visualization of adult worm ^[13]
• Treatment: no effective medications available ^[13]
  • Worm extraction: slow traction of the worm by wrapping with a stick or gauze (may take several days to weeks)
  • Wound care and topical antibiotics
  • Pain management (NSAIDs)
• Complications: cellulitis, abscess, sepsis, anaphylaxis
• Prevention ^[19]
  • Avoid submerging the affected limb in water until the worm is removed.
  • Filter or treat drinking water with larvicide.
  • Thoroughly cook aquatic animals and dispose of entrails safely.

Cestodes (tapeworms) are long, flat, ribbon-like worms composed of numerous segments and a single scolex at the head with which they anchor themselves to the intestine. Since they do not have a digestive tract, all nutrients are absorbed through the tegument. Cestodes are hermaphroditic (they contain both male and female organs).

Cysticercosis can cause brain cysts and seizures.

• Pathogen ^[23]
  • Dibothriocephalus latus (fish tapeworm; formerly Diphyllobothrium latum)
  • Fish tapeworms are cestodes.
• Mode of transmission: consumption of raw or undercooked freshwater fish containing larvae
• Life cycle: Larvae develop into adult tapeworms in the small intestine → Adult worms produce proglottids, which can detach from the tapeworm and are passed in the feces.
• Clinical features
  • Usually asymptomatic
  • Chronic infection leads to vitamin B₁₂ deficiency: fish tapeworms compete with the host for dietary vitamin B₁₂ in the intestine → anemia and/or neurological symptoms
• Diagnostics ^[1]
  • Initial test: CBC may show eosinophilia and megaloblastic anemia. ^[24]
  • Confirmatory test: stool examination for eggs or proglottids (i.e., segments of adult tapeworms)
• Treatment: praziquantel (off-label) ^[2]
• Prevention: thoroughly cook fish ^[2]

Dibothriocephalus causes vitamin B₁₂ deficiency.

• Pathogen: Hymenolepis nana (dwarf tapeworm) ^[25]
• Mode of transmission
  • Ingestion of eggs from contaminated food or water
  • Ingestion of cysticercoids from infected arthropods
• Life cycle: Ingestion of eggs → Develop into cysticercoid larvae in the small intestine villus (alternatively cysticercoids can be consumed from infected arthropods) → Cysticercoids (released upon rupture of the intestinal villus) develop into an adult worm in the intestinal lumen → Eggs are passed through the stool
• Clinical features
  • Mostly asymptomatic
  • Severe infection with Hymenolepis nana manifests with:
    • Anorexia, abdominal pain, diarrhea
    • Weakness, headache
• Diagnostics: stool examination for eggs ^[1]
• Treatment ^[1]
  • Praziquantel (off-label) ^[2]
  • OR nitazoxanide (off-label) ^[2]
• Prevention: proper hygiene and disposal of human waste ^[2]

Trematodes (flukes) are small, flat, oval worms with two suckers (one located at the mouth and the other ventrally) and a blind-ending gut. Most species are hermaphroditic, but some also form separate male and female adults.

• Pathogen
  • Clonorchis sinensis (Chinese liver fluke)
  • Clonorchis are trematodes (flukes).
  • Endemic to certain parts of Asia
• Mode of transmission: consumption of raw/undercooked freshwater fish
• Incubation period: 10–26 days ^[26]
• Life cycle: Water is contaminated with human feces containing Clonorchis eggs → Eggs are ingested by freshwater snails and mature into larvae → Larvae are released to water and penetrate fish → Humans eat fish containing larvae → Larvae migrate to biliary tract and mature into adult worms → Eggs of adult worms are released into the bile ducts and carried to the intestinal tract → Eggs are eliminated with the feces, thus completing the cycle.
• Clinical features
  • Most infected individuals are asymptomatic.
  • Acute symptoms
    • Cholangitis
    • Unspecific symptoms (e.g., right upper quadrant pain, diarrhea, fatigue)
  • Chronic symptoms and complications
    • Cholelithiasis with pigmented gallstones
    • Hepatomegaly
    • Malnutrition, weight loss
    • Jaundice
    • Risk factor for cholangiocarcinoma
• Diagnostics ^[13]
  • CBC: eosinophilia ^[27]
  • Microscopic examination of stool for eggs
  • Identification of adult worms on ERCP or during surgery
• Treatment ^[2]
  • Praziquantel ^[2]
  • OR albendazole (off-label) ^[2]
• Prevention: thoroughly cook seafood ^[2]

• Pathogen
  • Paragonimus westermani (responsible for most infections), less commonly P. mexicanus, P. kellicotti, P. heterotremus, P. africanus
  • Paragonimus is a genus of trematodes that commonly infest the lung (lung flukes).
  • Paragonimus species are endemic to Southeast Asia, Latin America, and Africa.
• Mode of transmission
  • Consumption of raw/undercooked crabs, crayfish, and contaminated seaweed
  • Utilization of contaminated cooking utensils
• Incubation period: 2–16 weeks ^[28]
• Life cycle: Larvae in fresh water penetrate crabs, crayfish, and other crustaceans → Larvae encyst to metalarvae → Humans consume infected crustaceans → Metalarvae excyst and penetrate the intestinal wall, then migrate to the lungs → Larvae develop into adults in the lungs and eggs are expectorated with the sputum → Eggs are swallowed and eliminated with the feces, thereby reaching fresh water again.
• Clinical features
  • Rare prodromal signs (e.g., abdominal pain, fever, diarrhea)
  • Possibly asymptomatic
  • Pulmonary form
    • Mild fever
    • Night sweats
    • Productive cough, hemoptysis
    • Pleural effusions
  • Extrapulmonary form
    • Cerebral paragonimiasis
      • Early symptoms resemble meningoencephalitis.
      • Chronic symptoms include headache, vomiting, seizures, and weakness
    • Possibly cyst, abscess, and granuloma formation in the intestine, spleen, peritoneum, and mesenteric lymph nodes
• Diagnostics ^[1]
  • CBC: eosinophilia
  • CXR: pleural effusion, multiple small cysts, irregular linear densities, and/or nodular opacities ^[29]
  • Microscopic examination of sputum, stool, pleural fluid, CSF, or other tissue specimens for eggs
  • Serologic testing (e.g., ELISA, western blot)
• Differential diagnoses: tuberculosis
• Treatment ^[2]
  • Praziquantel (off-label) ^[2]
  • OR triclabendazole (off-label) ^[2]
  • Consider addition of corticosteroids in CNS infections.
• Complications
  • Pulmonary: secondary infections, bronchiectasis, lung abscess, empyema
  • Cerebral: seizures, coma
  • Skin: migratory allergic skin lesions
• Prevention ^[2]
  • Avoid eating raw or undercooked crustaceans.
  • Cook pork thoroughly.

• Pathogen: Fasciola hepatica, Fasciola gigantica
• Mode of transmission
  • Consumption of contaminated freshwater plants (e.g., watercress)
  • Drinking contaminated freshwater
• Life cycle
  • Metacercariae on freshwater plants are ingested by herbivorous mammals, e.g., sheep, cattle (both definitive hosts), or humans (incidental hosts) → Migration of the organism through the intestinal wall, then liver parenchyma, and into the biliary ducts → Adult fluke release eggs into the biliary ducts, which are then passed in the stool of the host.
  • Snails serve as the intermediate hosts.
• Clinical features
  • Acute phase: fever, right upper quadrant pain, and hepatomegaly
  • Chronic biliary phase: abdominal pain, nausea, vomiting, and diarrhea
  • Features of biliary obstruction: biliary colic, cholangitis, cholelithiasis, and obstructive jaundice
• Diagnostics ^[13]
  • CBC: eosinophilia ^[30]
  • Microscopic examination of stool, bile, or duodenal aspirates for eggs
  • Serologic testing (e.g., ELISA, western blot)
  • Lesions seen on imaging (e.g., CT, MRI)
  • Endoscopy: adult flukes in the biliary tract
• Treatment ^[2]
  • Triclabendazole ^[2]
  • OR nitazoxanide (off-label) ^[2]
  • Biliary obstruction: GI consult and ERCP ^[31]
• Prevention ^[2]
  • Drink filtered water.
  • Avoid eating contaminated freshwater plants (e.g., bamboo shoots, watercress).