NAME: Necator americanus
SYNONYM OR CROSS REFERENCE: Hookworm disease, necatoriasis
CHARACTERISTICS: Family Ancylostomatidae, subfamily Necatorinae; intestinal nematode parasite, adult male measures 5-9 X 0.30 mm, female 9-11 X 0.35 mm; eggs are 64-76 X 35-40 µm head curves opposite to curvature of body, giving a hooked appearance to the anterior end
PATHOGENICITY: Infective larvae penetrate skin and travel via the lymphatics to enter the bloodstream, the lungs and the small intestine; adult parasites attached to the villi of small intestines suck blood causing abdominal discomfort, diarrhea, cramps, anorexia, weight loss; clinical features correspond mainly to the intensity of infection; heavy infection leads to development of iron deficiency and hypochromic microcytic anemia;leading causes of iron-deficiency anemia in children resulting in physical and mental retardation in development; infection causes cutaneous larva migrans - a self-limiting condition characterized by skin eruption; fatality is rare; no evidence of immunity in the infected
EPIDEMIOLOGY: Widely in tropical and subtropical countries, where improper disposal of human feces is practiced; occurs in South East Asia, South Pacific and East Africa and South America - moisture and temperature conditions favour development of larvae; sporadic cases occurs in southeastern US; prevalence higher in rural areas; universal susceptibility
HOST RANGE: Humans
INFECTIOUS DOSE: Not known
MODE OF TRANSMISSION: Infective larvae, develop from eggs excreted in feces and penetrate the skin, usually by the dorsum of the bare feet or between the toes; vertical transmission from mother to child is possible
INCUBATION PERIOD: Variable; GI symptoms can appear 35-40 days after exposure to filariform larvae
COMMUNICABILITY: Not directly transmitted from person-to-person
RESERVOIR: Humans
ZOONOSIS: None
VECTORS: None
DRUG SUSCEPTIBILITY: Sensitive to abendazole, mebendazola, pyrantel pamoate, levamisole
DRUG RESISTANCE: Mebendazola resistant strains have been reported
SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to 1% sodium hypochlorite, 2% glutaraldehyde
PHYSICAL INACTIVATION: Larvae sensitive to desiccation and freezing
SURVIVAL OUTSIDE HOST: Larvae can survive up to 3-4 weeks in moist, optimal survival in moist, sandy or loamy soil with ambient temperatures of 24-32° C
SURVEILLANCE: Monitor for symptoms: confirm by microscopic demonstration of eggs in stools
FIRST AID/TREATMENT: Administer appropriate drug therapy; pregnant women should not be treated with drugs in the first trimester
IMMUNIZATION: None available
PROPHYLAXIS: None available
LABORATORY-ACQUIRED INFECTIONS: None reported to date
SOURCES/SPECIMENS: Feces
PRIMARY HAZARDS: Ingestion; droplet exposure of the mucous membranes
SPECIAL HAZARDS: None
CONTAINMENT REQUIREMENTS: Biosafety level 2 practices and containment equipment for all activities involving the parasite, infectious or potentially infectious body fluids or tissues
PROTECTIVE CLOTHING: Laboratory coat; gloves when skin contact with infectious materials is unavoidable
OTHER PRECAUTIONS: None
SPILLS: Allow aerosols to settle; wearing protective clothing, gently cover the spill with absorbent paper towel and apply 1% sodium hypochlorite, starting at the perimeter and working towards the centre; allow sufficient contact time (30 mins) before clean up
DISPOSAL: Decontaminate all wastes before disposal; steam sterilization, chemical disinfection, incineration
STORAGE: In sealed containers that are appropriately labelled
Date prepared: March, 2001
Prepared by: Office of Laboratory Security, PHAC
Although the information, opinions and recommendations contained in this Material Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Copyright ©
Health Canada, 2001
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