Enteric Nematodes Ascaris lumbricoides Enterobius vermicularis Trichuris trichiura Hookworms...

Enteric Nematodes

Ascaris lumbricoidesEnterobius vermicularisTrichuris trichiuraHookworms

Ancylostoma duodenaleNecator americanus

Strongyloides stercoralis

What you should know about the Enteric Nematodes

Name of organism and diseaseTransmission (how acquired?)Location and migration in humanMajor clinical manifestations including

presence/absence of eosinophiliaDiagnostic tests

Organism: Ascaris lumbricoidesDisease: Ascariasis

Geographical Distribution:Worldwide1.2 billion infected (20%); 20,000 deaths

Transmission:Ingestion of OvaFecal contamination of water, soil and hands

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Larvae hatch in GI tract, penetrate GI wall,

migrate via lungs & bronchi back to GI(Adult stage)

Ascaris lumbricoidesLocation of Parasite

Ascaris lumbricoidesMorphology: Adult, 20-35 cm

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Male

Female

Ascaris lumbricoidesMorphology: Ova

Unfertilized

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Fertilized

EmbryonatedInfective

Ascaris lumbricoidesClinical:

Larval migration in lungs usually asymptomatic, but may be transient eosinophilia

Intestinal stage may produce abdominal pain, diarrhea & non-specific gastrointestinal complaints

Intestinal obstruction

Ascaris lumbricoidesClinical:

Ascaris lumbricoides

Diagnosis:O&P Test

Control & Treatment: Mebendazole, albendazole

Ascaris lumbricoides

Organism: Enterobius vermicularis PINWORM

Disease: Enterobiasis

Geographical Distribution:Worldwide, 20-60% school age children

Transmission:Ingestion (and inhalation) of eggs

Location of Parasite:Adults in proximal intestine, cecum & appendixnocturnal deposition of eggs on perianal area

Morphology:Adults are 1 cm

Clinical:Asymptomatic, vaginal pruritisNo migration, No eosinophiliaReinfection common

Enterobius vermicularis

Diagnosis: “Scotch” Tape test for eggs

Control & Treatment: Mebendazole


Organism: Trichuris trichiuraWHIPWORM

Disease: Trichuriasis

Geographical Distribution:Worldwide

Transmission:Ingestion of eggs

Location of Parasite:Adult embedded in mucosa of cecum,

colon, & rectum

Morphology: Adult 3-5 cmAnterior (digestive) end is thinPosterior (reproductive) end is thick

Trichuris trichuria

Trichuris trichuria

Trichuris trichuria

Clinical:Light infections - asymptomaticHeavy infections - diarrhea

bloody diarrhea, rectal prolapse

Diagnosis:O&P Test

Control & Treatment: Mebendazole & Albendazole

Trichuris trichuria

Organism: Ancylostoma duodenale & Necator americanus HOOKWORMS

Disease: Hookworm anemia

Geographical Distribution:Humid areas with poor sanitation

Transmission:Direct penetration of unbroken skin by larva

Location of Parasite:Adults attached to mucosa of duodenum and proximal small intestine

Morphology:Adults are 1 cm

Ancylostoma duodenale& Necator americanus

Ancylostoma duodenale

Necator americanus

Clinical:Red pruritic lesions at site of larval penetrationEosinophilia possibleAsymptomaticGastric pain & diarrheaAnemia (due to blood loss)

Diagnosis: O&P Test

Control & Treatment: Mebendazole & Albendazole


Organism: Strongyloides stercoralisDisease: Strongyloidiasis

Geographical Distribution:WorldwideHumid areas with poor sanitation

Transmission:Direct penetration of unbroken skin by larvaAutoinfection - internal (larva becomes infectious in intestinal tract) & external

Location of Parasite:Larva migrates via blood system to lungs,penetrates alveoli,coughed up and swallowed

Adult in mucosa of duodenum & jejunum

Eggs hatch in intestine

Larvae (non-infective) in stooldevelops into infective larva in soil(Free living cycle in soil)



Clinical:Pruritic rash associated with larval entryCoughing & wheezing, High eosinophiliaAbdominal pain, diarrhea

Hyperinfection - large numbers of larvae

Disseminated strongyloidiasis - in other organs (in immunocompromized patients - but not AIDS)

Control & Treatment: Ivermectin, thiabendazole

Strongyloides stercoralisMorphology:

Adult females 2-3 mm

Strongyloides stercoralisMorphology:

Larvae 0.2-0.3 nm

Diagnosis:String Test Baermann concentration

Serology & Bacterial agar plate


Organism:Disease:

Geographical Distribution:Transmission:Location of Parasite:Morphology:Clinical:Diagnosis:Control & Treatment:

Enteric Nematodes Ascaris lumbricoides Enterobius vermicularis Trichuris trichiura Hookworms...

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