NAME: Ancylostoma duodenale
SYNONYM OR CROSS REFERENCE: Hookworm; Old World Hookworm Footnote 1, Footnote 2, intestinal nematode Footnote 1, Footnote 2, ground itch Footnote 1, Footnote 2, pruritic erythematous rash Footnote 1, Footnote 2, Ankylostomiasis, anchylostomiasis, ancylostomiasis, helminthiasis Footnote 3, miners' anemia Footnote 4, tunnel disease Footnote 4, uncinariasis Footnote 4, brickmaker's anemia Footnote 5.
CHARACTERISTICS: A. duodenale belongs to the family Ancylostomatidae and subfamily of Ancylostomatinae Footnote 1. Adults are slightly larger and more robust than N. americanus. Adult male worm measures 8 to 11 by 0.4-0.5 mm, while the female is 10 to 13 mm long by 0.4-0.5 mm wide Footnote 1, Footnote 2. Their heads continue in the same direction as the curvature of their bodies Footnote 2, Footnote 6. Eggs are oval shaped with a thin shell and measure approximately 56-75 μm by 36-40 μm. They are characterized by a clear space between the developing embryo and the egg shell Footnote 1, Footnote 2. Eggs of N. americanus and A. duodenale are indistinguishable. Eggs are passed in feces and then embryonate and hatch within 1-2 days in soil as first stage rhabditoid larvae. First stage larvae develop to third stage, infectious, filariform larvae in approximately 1 week Footnote 1, Footnote 2, Footnote 7, Footnote 8.
PATHOGENICITY/TOXICITY: Like N. americanus, A. duodenale (third-stage) larvae follow thermal gradients and are guided by heat to human skin where they may irritate or invade the skin Footnote 9. Like N. americanus, a pruritic, erythematous, papular rash develops and produces what is known as “ground itch” around penetration sites of the infective larvae, usually on the hands and feet Footnote 1, Footnote 2. Invasive infection occurs when larvae enter the bloodstream and are carried to the lungs. A mild cough and pharyngeal irritation may occur during larval migration in the airways; however, passage through the lungs is usually asymptomatic Footnote 10. The larvae are swallowed down the oesophagus and migrate to the gastrointestinal tract. Larvae then hook onto the intestinal mucosa where they mature into adult hookworms by feeding on blood. The major-hookworm related injury occurs due to intestinal blood loss, which can lead to iron-deficiency anaemia in moderate to heavy infections. In the gut, adult worms may produce epigastric pain and abnormal peristalsis Footnote 2, Footnote 6. Clinical features are highly dependent on worm burden and dietary iron levels Footnote 1, Footnote 2, Footnote 6. In children this condition may precipitate heart failure or kwashiorkor Footnote 1. Retardation of mental, sexual, and physical development has also been noted in children Footnote 1, Footnote 2, Footnote 7. Intrauterine growth retardation, prematurity, and low birth weight among newborns born to infected mothers has been noted Footnote 1, Footnote 7. Acute/heavy infections may result in fatigue, weakness, abdominal pain, and diarrhea with blood loss Footnote 1. Adult’s lifespan in human intestine is 1-2 years but can be as long as 10-12 years Footnote 1, Footnote 2, Footnote 6, Footnote 11.
EPIDEMIOLOGY: Infections with A. duodenale frequently overlap N. americanus infections in areas of Africa, India and China. Estimated that approximately 740 million individuals are currently infected worldwide with A. duodenale and N. americanus Footnote 1, Footnote 2, Footnote 12, Footnote 13.
Mortality rate, worldwide, attributed to deaths occurring through direct hookworm infection, is estimated to be ~65,000 deaths annually Footnote 14. The majority of infected individuals have a small worm burden and are asymptomatic Footnote 1, Footnote 2. Hookworm infection is among the most important tropical diseases in humans Footnote 7. Hookworm infection is found worldwide between 45°N and 30°S latitudes. A. duodenale is seen in Mediterranean basin, Middle East, sub-Saharan Africa, northern India, China, and Japan Footnote 1, Footnote 2, Footnote 6, Footnote 7. A. duodenale is endemic in warm, moist tropical areas where people defecate in the soil Footnote 6. Infection levels intensify in closed, densely populated communities such as tea and coffee plantations Footnote 2.
HOST RANGE:Humans Footnote 15.
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: Direct contact of soil containing filariform larvae with unprotected skin Footnote 1, Footnote 2, Footnote 6, Footnote 7. Infection can also be oral with direct maturation in the intestine to adult stage Footnote 1, Footnote 7. Infection can be transplacental or transmammary from mother to fetus/infant via infected placental/mammary tissue Footnote 16-Footnote 18.
INCUBATION PERIOD: Following penetration, A. duodenale migrates to the lungs within about 10 days Footnote 19. After 3 to 5 weeks, it passes through the gastrointestinal tract and attaches to the intestinal mucosa, where it matures into an adult worm and may stay for up to 1 year. Patent infections develop in 5-8 weeks following exposure Footnote 1, Footnote 2, Footnote 6. However, A. duodenale have the ability to arrest development in the host, this phenomenon can extend the prepatent period Footnote 20.
RESERVOIR: Humans are the only known reservoir of A.duodenale and N. americanus. The majority of infected individuals are asymptomatic due to low worm burden; however, eggs can be passed in feces Footnote 1, Footnote 2, Footnote 6, Footnote 7.
ZOONOSIS: None. However, transfer of adult A. duodenale from infected dogs to a 3 year old child afflicted with congenital polycythemia has been reported Footnote 21.
SUSCEPTIBILITY TO DISINFECTANTS: Infective larvae of A. duodenale are susceptible to 70% ethanol for 10 minutes, 0.5 % Dettol® for 20 minutes, chlorinated hydrocarbons (tetrachloroethylene) Footnote 22. Sodium hypochlorite (1%) and glutaraldehyde (2%) are not effective Footnote 22, Footnote 23.
PHYSICAL INACTIVATION: Infective larvae are inactivated by the application of heat through water above 80°C (practical recommendation is to use water that is close to boiling point) Footnote 22. Ancylostoma spp. larvae can not survive drying, or direct sunlight, and they cannot survive below 0 ºC or above 45 ºC Footnote 24. The larvae are also sensitive to high salt concentrations Footnote 25.
SURVIVAL OUTSIDE HOST: Eggs hatch, releasing first stage rhabditiform larvae in soil, which develop into infectious, filariform larvae in 5-8 days Footnote 1, Footnote 2, Footnote 6, Footnote 7. Infectious, filariform larvae do not feed and if they fail to infect a host they die within a few weeks Footnote 2, Footnote 6. The infective filariform larvae remain viable in the soil for several weeks Footnote 1.
SURVEILLANCE: Monitor for symptoms. Infection is demonstrated by direct observation of characteristic eggs in feces Footnote 1, Footnote 7. Quantitative egg counts include Kato-Katz test, concentration test, Beaver direct egg count, Stoll dilutional egg count, and McMaster techniques Footnote 26; and PCR-based tests, with PCR-based tests being the most sensitive Footnote 26.
FIRST AID/TREATMENT: Widely used antihelmintic agents pyrantel pamoate, mebendazole, and albendazole are highly effective in treating A. duodenale infection Footnote 1, Footnote 2, Footnote 6, Footnote 7. When anaemia is mild or moderate, iron replacement is often adequate treatment Footnote 1, Footnote 2, Footnote 6. More severe anaemia may require blood transfusions Footnote 1, Footnote 2.
PROPHYLAXIS: Hygiene measures such as hand washing, drinking safe water, properly cleaning and cooking food, and wearing shoes Footnote 10.
LABORATORY-ACQUIRED INFECTIONS: None reported for A. duodenale. One case of ground itch reported in an animal caretaker treating cat infected with Ancylostoma braziliense and Ancylostoma caninum – Close relatives of A. duodenale Footnote 28, Footnote 29.
SPECIAL HAZARDS: None.
RISK GROUP CLASSIFICATION: Risk Group 2.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 30.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 30.
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 30.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up Footnote 30, Footnote 31.
DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism by autoclave, chemical disinfection, gamma irradiation, or incineration before disposing Footnote 30.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled Footnote 30.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen 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.
Public Health Agency of Canada, 2011