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AUTHOR AND EDITOR INFORMATION

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Author: Murat Hökelek, MD, PhD, Technical Consultant of Parasitology Laboratory, Associate Professor, Department of Clinical Microbiology, Ondokuz Mayis University Medical School, Turkey

Murat Hökelek is a member of the following medical societies: Turkish Society for Parasitology

Coauthor(s): Larry I Lutwick, MD, Professor of Medicine, State University of New York, Downstate Medical School; Director, Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Brooklyn Campus; Arnold C Cua, MD, Physician, Department of Infectious Diseases, Renown Medical Center

Editors: Joseph Richard Masci, MD, Chief of Infectious Diseases, Associate Director, Associate Professor, Department of Internal Medicine, Division of Infectious Diseases, Elmhurst Hospital Center, Mount Sinai School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Ronald A Greenfield, MD, Professor, Department of Internal Medicine, Section of Infectious Diseases, University of Oklahoma College of Medicine; Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital; Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Author and Editor Disclosure

Synonyms and related keywords: nematode infections, roundworms, helminths, helminthic infection, intestinal parasites, ascariasis, enterobiasis, trichuriasis, strongyloidiasis, filariasis, parasitic diseases, larva migrans, river blindness, dracunculiasis, whipworm, loiasis, Guinea worm, onchocerciasis, Strongyloides stercoralis, Enterobius vermicularis, Ascaris lumbricoides, Necator americanus, Ancylostoma duodenale, Dracunculus medinensis, Wuchereria bancrofti, Onchocerca volvulus, Loa loa, Brugia malayi, Brugia timori, Trichuris trichiura, Toxocara canis, Toxocara cati, Ancylostoma braziliense, S stercoralis, E vermicularis, A lumbricoides, N americanus, A duodenale, D medinensis, W bancrofti, B malayi, B timori, L Loa, O volvulus, T trichiura, T canis, T cati, A braziliense


INTRODUCTION

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Background

Nematode infections in humans include ascariasis, trichuriasis, hookworm, enterobiasis, strongyloidiasis, filariasis, and trichinosis, among others. The phylum Nematoda, also known as the roundworms, is the second largest phylum in the animal kingdom, encompassing up to 500,000 species. Members of Nematoda are elongated, with bilaterally symmetric bodies that contain an intestinal system and a large body cavity.

Many roundworm species are free living in nature. Recent data have demonstrated that approximately 60 species of roundworms parasitize humans. Intestinal roundworm infections constitute the largest group of helminthic diseases in humans. According to a 2005 report by the World Health Organization (WHO), approximately 0.807-1.221 billion humans have ascariasis, 604-795 million have trichuriasis, and 576-740 million have hookworm infections worldwide.1

Pathophysiology

The life cycle of parasitic nematodes is clinically important. Some nematode infections can be transmitted directly from infected to uninfected people; in others, the nematode eggs must undergo a process of maturation outside the host. In a third category, the parasites may spend a part of their life cycle in the soil before becoming infective to humans.

As with other parasitic infections, definitive diagnosis of nematode infections depends on demonstration of the stage of the life cycle in the host. Nematodes, as with most other worms infectious to humans, almost never complete their entire life cycle in the human host.

The life cycles of nematodes are complex and highly varied. Some species, including Enterobius vermicularis, can be transmitted directly from person to person, while others, such as Ascaris lumbricoides, Necator americanus, and Ancylostoma duodenale, require a soil phase for development. Because most helminthic parasites do not self-replicate, the acquisition of a heavy burden of adult worms requires repeated exposure to the parasite in its infectious stage, whether larva or egg. Hence, clinical disease, as opposed to asymptomatic infection, generally develops only with prolonged residence in an endemic region.

Unlike with protozoan infections, a casual or a low degree of exposure to infective stages of parasitic nematodes usually does not result in patent infection or pathologic findings. Repeated or intense exposure to a multitude of infective stage larvae is required for infection to be established and disease to arise.

Eosinophilia and elevated serum immunoglobulin E (IgE) levels are features of many nematode infections; when unexplained, these symptoms should always prompt a search for occult roundworm infection. Humans do not appear to develop significant protective immunity to intestinal nematodes, although the mechanisms of parasite immune evasion and host immune responses to these infections have not been elucidated in detail.

Frequency

United States

  • Trichuriasis: Recent estimates indicate that 2.2 million people in the United States are infected with Trichuris trichiura (whipworm), mainly in the rural Southeast.
  • Enterobiasis: This is the most common of all helminthic infections, with an estimated 42 million cases.
  • Ascariasis: An estimated 4 million people, mainly in the Southeast, are infected with Ascaris species.
  • Hookworm: This infection still has a low degree of prevalence in the Southeast.
  • Strongyloidiasis: A prevalence rate of 0.4-4% has been estimated in southern states.
  • Trichinosis: The prevalence rate is 4-20%.

International

  • Trichuriasis: Infection with T trichiura is one of the most prevalent nematode infections worldwide; approximately 800 million persons have trichuriasis worldwide, most abundantly in warm moist regions. Infection rates of up to 75% were found in young schoolchildren in Puerto Rico.
  • Enterobiasis: Pinworm is also highly prevalent throughout the world, particularly in countries of the temperate zone. Children are most commonly infected. Estimated prevalence rates among children in various world regions are 4–28%.
  • Ascariasis: Ascaris, or roundworm, infection is the common helminthic infection in humans, with an estimated worldwide prevalence of 1 billion. The causative organism, A lumbricoides, is cosmopolitan in distribution, being most abundant in tropical countries.
  • Hookworm: Human infection with the 2 species of hookworm, A duodenale and N americanus, is estimated to affect approximately 550-750 million people.
  • Strongyloidiasis: The infection is more common in tropical countries with poor sanitation, especially in countries of Southeast Asia and parts of Africa. Strongyloides stercoralis is also endemic in Jamaica and presumably elsewhere in the Caribbean. An estimated 30-100 million persons worldwide have strongyloidiasis.
  • Trichinosis: Trichinella species are distributed throughout the world and are spread widely in nature among a large number of carnivorous animals, with humans acting as an incidental host. Trichinosis has been a major public health problem and has been reported in many Asian countries, including China, Japan, Korea, and Thailand.
  • Dracunculiasis: Estimates of the number of people infected with Dracunculus medinensis in Africa, the Middle East, India, and other tropical areas range from 50-150 million. An aggressive eradication campaign has been underway to eliminate D medinensis, which is called the Guinea worm.
  • Filariasis: An estimated 120 million people are infected with Wuchereria bancrofti, Brugia malayi, and Brugia timori.
  • Loiasis: Loa loa is irregularly distributed in West and Central Africa.
  • Onchocerciasis: Onchocerca volvulus infects 20 million people in West, Central, and East Africa and another 1 million people in scattered foci in Central America and South America. The disease caused by this filarial worm is called river blindness.

Mortality/Morbidity

Nematode infections are usually asymptomatic or subclinical.

  • Strongyloidosis may be fatal in immunocompromised patients and in newborns.
  • Intestinal nematodes can cause some GI problems (eg, abdominal pain, diarrhea, anorexia, weight loss, malaise).
  • Hookworms can cause serious anemia.
  • Some of the more serious nematode infections result in symptoms from inflammatory responses in vital organs and nutritional deficiencies.

Race

  • Nematode infections have no known racial predilection.

Sex

  • Nematode infections have no known sexual predilection.

Age

  • E vermicularis infection (pinworm) is more common in children than in adults.


CLINICAL

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History

Several clinical signs and symptoms can occur in patients with nematode infections.

  • Lung invasion - Löeffler or Löefflerlike syndrome (ascariasis, hookworm infections, strongyloidiasis)
    • Fever
    • Cough
    • Blood-tinged sputum
    • Wheezing
    • Rales
    • Dyspnea
    • Substernal pain
    • Pulmonary consolidations
    • Eosinophilia
    • Urticaria
    • Asthma
    • Angioneurotic edema
  • Intestinal invasion
    • May be asymptomatic (small number)
    • Abdominal pain (usually vague)
    • Abdominal cramps/colic
    • Diarrhea
    • Vomiting (rarely)
    • Constipation (occasionally)
  • Muscle and other tissue invasion - Trichinosis
    • Myalgias
    • Fever
    • Edema and spasm
    • Periorbital and facial edema
    • Photophobia
    • Sweating
    • Conjunctivitis
    • Weakness or prostration
    • Pain upon swallowing
    • Subconjunctival, retinal, and ungual hemorrhages
    • Rashes and formication
    • Encephalitis, myocarditis, nephritis
    • Pneumonia, meningitis, neuropathy
  • Lymphatic filariasis - W bancrofti, B malayi, B timori
    • Inflammatory signs (pain, tenderness, swelling, erythema)
    • Lymphadenitis/lymphangitis
    • Orchitis
    • Fever
    • Abscesses
    • Obstructive signs (lymphatic varices, hydrocele)
    • Lymphedema and elephantiasis
    • Chyluria
    • Hypereosinophilia
  • Loiasis - Loa loa
    • Calabar swellings (recurrent subcutaneous inflammation/swelling)
    • Eye worm (adults or larvae migrating under conjunctiva)
    • Eosinophilia (may exceed 70%)
    • Fever, irritability, urticaria, and pruritus
  • Onchocerciasis - O volvulus
    • Dermatitis
    • Nodules
    • Lymphadenitis
    • Ocular changes
      • Intraocular microfilariae
      • Punctate keratitis
      • Sclerosing keratitis
      • Anterior uveitis chorioretinitis
      • Optic neuritis
      • Optic atrophy
      • Glaucoma
      • Blindness (river blindness)
  • Dracunculiasis - D medinensis, Guinea worm disease
    • Allergic manifestations
      • Erythema
      • Urticaria
      • Pruritus
      • Nausea
      • Vomiting
      • Giddiness
      • Syncope
      • Fever (occasionally)
    • Local lesions
      • Papule
      • Sterile blister
      • Ulceration
      • Abscesses
    • Worm protrusion from skin
  • Toxocariasis - Toxocara canis/Toxocara cati, visceral or ocular larva migrans
  • Cutaneous larva migrans - Ancylostoma braziliense, creeping eruption
    • Itching and red papules
    • Serpiginous track
    • Edema and acute inflammation
    • Scars
    • Secondary infection

Physical

  • T trichiura infections: In heavily infected people, trichuriasis appears to manifest as mild anemia, eosinophilia, bloody diarrhea (classic trichuris dysentery syndrome), growth retardation (chronic trichuris colitis with growth retardation), abdominal pain, finger clubbing, and rectal prolapse (especially in children).
  • E vermicularis infection (pinworm): The most common symptom of pinworm infection is nocturnal perianal pruritus. Occasionally, the migration of the parasite produces ectopic disease (eg, appendicitis, chronic salpingitis, ulcerative lesions in the small or large bowel). Enuresis has been blamed on the pinworm.
  • A lumbricoides infection
    • A more serious complication of ascariasis is encountered when a mass of worms obstructs the lumen of the small bowel. This acute abdominal condition is commonly observed in children with heavy infections. The presentation is similar to that of acute intestinal obstruction, with vomiting, abdominal distention, and cramps.
    • Another obstructive syndrome is encountered when Ascaris worms invade the biliary duct and cause pancreatic-biliary ascariasis. The most common presenting feature is abdominal pain, observed in 98% of patients. Less common features include ascending cholangitis, acute pancreatitis, and, rarely, obstructive jaundice.
    • Ascariasis in pregnant women results in intrauterine growth retardation.
  • Hookworms
    • The major manifestations of hookworm disease include iron deficiency anemia and chronic protein energy malnutrition. The development of these clinical features depends not only on the worm burden but also on the amount of absorbable dietary iron.
    • During the phase of worm attachment to small intestine mucosa, abdominal pain, diarrhea, and weight loss may be noted. In addition, malabsorption has been reported in children and, less commonly, in adults.
  • S stercoralis infection
    • Burning or colicky abdominal pain, often epigastric, occurs and is associated with diarrhea and the passage of mucus.
    • Some patients with strongyloidiasis report nausea, vomiting, and weight loss, with evidence of malabsorption or of protein-losing enteropathy.
    • Massive larval invasion of the lungs and other tissues may occur with hyperinfection, usually in immunocompromised hosts. In this syndrome, the worm is able to complete its entire life cycle in the human, and the symptoms are related to the large burden of larvae migrating in the host.
    • Severe generalized abdominal pain, diffuse pulmonary infiltrates, ileus, shock, and meningitis or sepsis due to gram-negative bacilli may occur.
  • T spiralis infection: Myositis with pain, swelling, and weakness is common; it usually first develops in the extraocular muscles and then involves the masseters, neck muscles, limb flexors, and lumbar muscles. Some patients report headache, cough, shortness of breath, hoarseness, and dysphagia.

Causes

  • Ingestion of mature eggs in fecally contaminated food or drink
  • Larval penetration of skin (hookworms and S stercoralis)
  • Larvae introduced into human host by arthropod vector (mosquitoes for filariasis and flies for O volvulus)


DIFFERENTIALS

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Anemia
Anthrax
Appendicitis
Asthma
Cholecystitis
Diverticulitis
Hodgkin Disease
Leprosy
Lymphedema
Lymphogranuloma Venereum (LGV)
Pancreatitis, Acute
Systemic Lupus Erythematosus
Tuberculosis

Other Problems to be Considered

Nonfilarial causes of lymphangitis include acute bacterial lymphangitis, phlebitis, and plague (unusual).

Nonfilarial causes of lymphedema, chyluria, and elephantiasis include the following:

  • Infiltrative or granulomatous processes (eg, tumor, fungus)
  • Chronic venostasis or phlebitis
  • Cardiac insufficiency
  • Nutritional deficiencies
  • Heredity (eg, Milroy disease)
  • Lateritious soil-obstructing lymphatics


WORKUP

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Lab Studies

  • Stool examination for intestinal nematodes using native, zinc sulfate flotation, or formalin-ethyl acetate sedimentation techniques
    • Based on characteristics of eggs or larvae in stool or adult worm, if passed
    • Cellophane-tape impression for pinworms
  • Examination of larvae or adult worms taken from the tissue, characteristic microfilariae on blood smear, eosinophilia
  • Filariasis - Membrane filtration technique, Knott technique, and thick blood smear (Giemsa stained)
  • Distinction of species by larval examination - Challenging and may require expert examination
  • Onchocerciasis - Identified by skin snip/biopsy showing larvae
  • Toxocariasis - Enzyme-linked immunosorbent assay (ELISA) and, occasionally, biopsy
  • Trichinosis - Muscle biopsy and ELISA

Imaging Studies

  • Larvae in sputum or adult worms observed on radiologic studies (uncommon)
  • Lung radiography for Löeffler syndrome
  • Ultrasonography - Useful in the diagnosis of ascariasis as a cause of biliary tract disease

Other Tests

  • Onchocerciasis: Skin snip, nodulectomy, slit-lamp examination, and Mazzotti test are helpful.

Histologic Findings

Characteristic eggs, worms, or larvae in tissue


TREATMENT

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Medical Care

  • Nematode infections need to be identified and treated accordingly.
  • In dracunculiasis, the best treatment is direct removal of worms from tissue, taking care not to break the worm.
  • Treat secondary infections.

Surgical Care

  • Acute intestinal obstruction and perforation in patients with ascariasis may require surgical treatment.
  • Long-standing lymphatic filariasis due to W bancrofti and B malayi infection may require surgical intervention to increase lymphatic drainage. This is unusual and likely observed in long-term residents of endemic areas who have been subjected to extensive exposure to the parasite.

Consultations

  • Gastroenterologists
  • Parasitologists
  • Radiologists
  • Dermatologists
  • Chest diseases specialists

Diet

No special diet is required.

Activity

No restrictions are necessary. In lymphatic filariasis, if edema is a problem, the patient may want to elevate legs while sitting.


MEDICATION

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The goals of pharmacotherapy are to eradicate the infestation, to reduce morbidity, and to prevent complications.

Drug Category: Anthelmintic agents

Parasite biochemical pathways are different from the human host; thus, toxicity is directed to the parasite, egg, or larvae. Mechanism of action varies within the drug class. Antiparasitic actions may include the following:

  • Inhibition of microtubules, causing irreversible block of glucose uptake
  • Tubulin polymerization inhibition
  • Depolarizing neuromuscular blockade
  • Cholinesterase inhibition
  • Increased cell membrane permeability, resulting in intracellular calcium loss
  • Vacuolization of the schistosome tegument
  • Increased cell membrane permeability to chloride ions via chloride channels alteration

Drug NameAlbendazole (Albenza)
DescriptionUsed for hookworm, pinworm, and roundworm. Decreases ATP production in worm, causing energy depletion, immobilization, and, finally, death.
Adult DoseAscariasis, enterobiasis, hookworm, or trichuriasis: 400 mg PO as single dose, may repeat in 3 wk if necessary
Strongyloidiasis: 400 mg PO qd for 3 d, may repeat regimen in 3 wk if necessary
Trichinosis: 400 mg PO bid for 15 d
Pediatric DoseAscariasis, enterobiasis, hookworm, or trichuriasis
<2 years: 200 mg PO as single dose, may repeat in 3 wk if necessary
>2 years: Administer as in adults
Strongyloidiasis
<2 years: 200 mg PO qd for 3 d, may repeat regimen in 3 wk if necessary
>2 years: Administer as in adults
ContraindicationsDocumented hypersensitivity
InteractionsCoadministration with carbamazepine may decrease efficacy; dexamethasone, cimetidine, and praziquantel may increase toxicity
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsTeratogenic in laboratory animals; avoid in pregnancy; may increase LFTs significantly (discontinue drug, may resume when at pretest values); abdominal pain, nausea, vomiting, diarrhea, dizziness, vertigo, fever, increased intracranial pressure, and alopecia may occur

Drug NameMebendazole (Vermox)
DescriptionIndicated for treating E vermicularis (pinworm), T trichiura (whipworm), A lumbricoides (common roundworm), A duodenale (common hookworm), N americanus (American hookworm) in single or mixed infections. Efficacy varies as a function of such factors as preexisting diarrhea and GI transit time, degree of infection, and helminth strains. Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine where helminths dwell.
Adult DoseAscariasis, hookworm, or trichuriasis: 100 mg PO qd for 3 d; alternatively, 500 mg PO once
Enterobiasis: 100 mg PO once, repeat dose in 2 wk
Trichinosis: 200-400 mg PO tid for 3 d initially; followed by 400-500 mg tid for 10 d
Pediatric Dose<2 years: Not established
>2 years: Administer as adults
ContraindicationsDocumented hypersensitivity
InteractionsCarbamazepine and phenytoin may decrease effects; cimetidine may increase levels
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsAvoid use in pregnancy, especially first trimester; adjust dose in hepatic impairment

Drug NameIvermectin (Mectizan)
DescriptionMember of avermectin class (broad-spectrum antiparasitic agents). Unique mode of action. Binds selectively with high affinity to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells. Increases permeability of cell membrane to chloride ions. Results in hyperpolarization of nerve or muscle cell, causing parasite paralysis and death. Also affects other ligand-gated chloride channels (eg, those gated by GABA). Active against various life-cycle stages of most nematodes. Active against O volvulus tissue microfilariae but not adult form. Activity against S stercoralis limited to intestinal stages.
Adult DoseStrongyloidiasis: 200 mcg/kg PO qd for 1-2 d
Cutaneous larva migrans (onchocerciasis): 150 mcg/kg PO as single dose; may repeat q6-12mo until asymptomatic
Pediatric Dose<5 years: Not established
>5 years: Administer as in adults
ContraindicationsDocumented hypersensitivity
InteractionsNone reported
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsCaution in breastfeeding women; repeat courses of therapy may be required in immunocompromised patients; may cause nausea, vomiting, drowsiness, and mild CNS depression; patients with hyperreactive onchodermatitis may develop a severe immune reaction (ie, Mazzotti reaction) consisting of optic neuritis, chorioretinitis, proteinuria, pruritus, rash, and edema

Drug NamePiperazine (Vermizine)
DescriptionReadily absorbed from GI tract, partially degraded in vivo, and excreted in urine. Paralyzes worm muscle; thus, worm expelled by normal intestinal peristalsis. Exhibits wide therapeutic index. Not available in the United States.
Adult DoseAscariasis: 3.5 g/d (hexahydrate equivalent) PO as single dose for 2 d
Enterobiasis: 65 mg/d (hexahydrate equivalent) PO for 7 d; not to exceed 2.5 g/d
Pediatric DoseAscariasis: 75 mg/kg/d (hexahydrate equivalent) PO for 2 d; not to exceed 3.5 g/d
Enterobiasis: Administer as in adults
ContraindicationsDocumented hypersensitivity; hepatic or renal dysfunction; seizure disorder
InteractionsPhenothiazines may increase risk of seizures; antagonizes pyrantel pamoate activity
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
PrecautionsMost commonly reported reactions include GI and CNS effects, discontinue drug if adverse effects become significant; avoid prolonged, repeated, and excessive therapy due to potential neurotoxicity; caution in severe malnutrition and anemia

Drug NamePyrantel (Antiminth, Pin-Rid)
DescriptionDepolarizing neuromuscular blocking agent and cholinesterase inhibitor that results in spastic paralysis of worm. Active against E vermicularis (pinworm), A lumbricoides (roundworm), and A duodenale (hookworm).
Adult DoseHookworm: 11 mg/kg PO qd for 3 d; not to exceed 1 g/d
Ascariasis: 11 mg/kg PO as single dose; not to exceed 1 g/d
Enterobiasis: 11 mg/kg PO as single dose; not to exceed 1 g/d; repeat q2wk for 2 regimens
Pediatric Dose<2 years: Not established
>2 years: Administer as in adults
ContraindicationsDocumented hypersensitivity
InteractionsPyrantel and piperazine are mutually antagonistic in ascariasis; may increase theophylline serum levels
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsCaution in liver impairment, anemia, pregnancy, and malnutrition

Drug NameDiethylcarbamazine citrate (Hetrazan)
DescriptionEffective in treating filariasis specific for W bancrofti, B malayi, and L loa. Does not contain any toxic metallic elements. Not recommended as DOC because of severe adverse effects. Recommended if therapy with mebendazole fails or unavailable.
Adult Dose6 mg/kg/d PO divided tid for 14 d
Pediatric DoseAdminister as in adults
ContraindicationsDocumented hypersensitivity
InteractionsNone reported
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
PrecautionsCaution in renal dysfunction (reduce dose); gradual dose titration may be needed over first 3 d to reduce allergic reaction in patients with microfilariae in blood or skin; patients with hyperreactive onchodermatitis or L loa infection may develop a severe immune reaction (ie, Mazzotti reaction) consisting of optic neuritis, chorioretinitis, proteinuria, pruritus, rash, and edema


FOLLOW-UP

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Further Outpatient Care

  • Patients who have undergone treatment for nematode infections should undergo follow-up stool studies at 2 weeks and re-treatment, if necessary.

Deterrence/Prevention

  • Good hygiene and sanitation
  • Avoidance of sources of infection (eg, arthropod bites, rivers/streams, contaminated soils)
  • Public health activities such as vector control

Complications

  • Vomiting worms - Ascariasis
  • Worm migration
    • Cholangitis (migration to common bile duct)
    • Pancreatitis (migration to pancreatic duct)
    • Appendicitis (migration to appendix)
    • Diverticulitis (migration to diverticula)
  • Liver abscess
  • Intestinal obstruction, volvulus
  • Intussusception
  • Bowel penetration
  • Anemia, hypoproteinemia - Hookworm
  • CNS infection - Strongyloides infection
  • Onchocerciasis - Blindness
  • Filariasis - Lymphatic destruction leading to severe edema (elephantiasis)
  • Neurohelminthiasis - CNS migrations and infection
  • Visceral worms
    • Hepatitis
    • Splenomegaly
    • Pleuritis
    • Peritonitis
    • Eosinophilic granuloma
    • Other organ damage because larvae migrate for as long as 6 months

Prognosis

  • Light-to-moderate nematode infections carry a good prognosis. Prognosis depends on the organ infected and the extent of the infection.
    • Ascariasis should always be treated because of the risk of migrating adult worms.
    • Long-term diethylcarbamazine treatment and immunomonitoring of patients with filariae are essential in endemic areas to arrest and prevent pathology.

Patient Education

  • Avoid fecally contaminated food, water, and soil.
  • Avoid bites by arthropod vectors. Use insect repellants and other protective measures, eg, proper clothing.
  • Avoid rivers, streams, and soils known to be infected.


MISCELLANEOUS

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Special Concerns

  • Benzimidazoles (eg, mebendazole, albendazole) should not be used by pregnant women.
  • Ivermectin has shown little teratogenic potential and has provided an effective therapy, although benefits should clearly outweigh risks.


MULTIMEDIA

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Media file 1:  Strongyloides eggs in native examination from feces of a newborn.
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Media type:  Photo

Media file 2:  Ascaris lumbricoides egg in feces (formalin-ethyl acetate sedimentation method).
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Media type:  Photo

Media file 3:  A typical Trichuris trichiura egg in feces.
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Media type:  Photo


REFERENCES

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  3. Bennett A, Guyatt H. Reducing intestinal nematode infection: efficacy of albendazole and mebendazole. Parasitol Today. Feb 2000;16(2):71-4. [Medline].
  4. Bethony J, Brooker S, Albonico M, et al. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. Lancet. May 6 2006;367(9521):1521-32. [Medline]. [Full Text].
  5. Bradley JE, Jackson JA. Immunity, immunoregulation and the ecology of trichuriasis and ascariasis. Parasite Immunol. Nov-Dec 2004;26(11-12):429-41. [Medline]. [Full Text].
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Nematode Infections excerpt

Article Last Updated: Oct 23, 2008