Pathogen Safety Data Sheets: Infectious Substances – Ancylostoma duodenale
PATHOGEN SAFETY DATA SHEET - INFECTIOUS SUBSTANCES
SECTION I - INFECTIOUS AGENT
NAME: Ancylostoma duodenale
SYNONYM OR CROSS REFERENCE: Hookworm; Old World HookwormFootnote 1Footnote 2, intestinal nematodeFootnote 1Footnote 2, ground itch Footnote 1Footnote 2, pruritic erythematous rashFootnote 1Footnote 2, Ankylostomiasis, anchylostomiasis, ancylostomiasis, helminthiasisFootnote 3, miners' anemiaFootnote 4, tunnel diseaseFootnote 4, uncinariasisFootnote 4, brickmaker's anemiaFootnote 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 1Footnote 2. Their heads continue in the same direction as the curvature of their bodies Footnote 2Footnote 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 1Footnote 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 1Footnote 2Footnote 7Footnote 8.
SECTION II - HAZARD IDENTIFICATION
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 skinFootnote 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 feetFootnote 1Footnote 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 asymptomaticFootnote 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 peristalsisFootnote 2Footnote 6. Clinical features are highly dependent on worm burden and dietary iron levelsFootnote 1Footnote 2Footnote 6. In children this condition may precipitate heart failure or kwashiorkorFootnote 1. Retardation of mental, sexual, and physical development has also been noted in childrenFootnote 1Footnote 2Footnote 7. Intrauterine growth retardation, prematurity, and low birth weight among newborns born to infected mothers has been notedFootnote 1Footnote 7. Acute/heavy infections may result in fatigue, weakness, abdominal pain, and diarrhea with blood lossFootnote 1. Adult's lifespan in human intestine is 1-2 years but can be as long as 10-12 yearsFootnote 1Footnote 2Footnote 6Footnote 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 1Footnote 2Footnote 12Footnote 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 1Footnote 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 1Footnote 2Footnote 6Footnote 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 1Footnote 2Footnote 6Footnote 7. Infection can also be oral with direct maturation in the intestine to adult stage Footnote 1Footnote 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 1Footnote 2Footnote 6. However, A. duodenale have the ability to arrest development in the host, this phenomenon can extend the prepatent period Footnote 20.
COMMUNICABILITY: Human-to-human transmission: Mother to fetus/infant via infected placental/mammary tissue Footnote 11Footnote 16-Footnote 18.
SECTION III - DISSEMINATION
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 fecesFootnote 1Footnote 2Footnote 6Footnote 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.
SECTION IV - STABILITY AND VIABILITY
DRUG SUSCEPTIBILITY: A. duodenale is susceptible to pyrantel pamoate, mebendazole, nitrazoxanide, and albendazole Footnote 1Footnote 2.
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 22Footnote 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 1Footnote 2Footnote 6Footnote 7. Infectious, filariform larvae do not feed and if they fail to infect a host they die within a few weeks Footnote 2Footnote 6. The infective filariform larvae remain viable in the soil for several weeks Footnote 1.
SECTION V – FIRST AID / MEDICAL
SURVEILLANCE: Monitor for symptoms. Infection is demonstrated by direct observation of characteristic eggs in feces Footnote 1Footnote 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 6Footnote 7. When anaemia is mild or moderate, iron replacement is often adequate treatment Footnote 1Footnote 2Footnote 6. More severe anaemia may require blood transfusions Footnote 1Footnote 2.
IMMUNISATION: Several vaccines are under development based on injection of combinations of isolated recombinant antigenic proteins Footnote 12-Footnote 14Footnote 27.
PROPHYLAXIS: Hygiene measures such as hand washing, drinking safe water, properly cleaning and cooking food, and wearing shoes Footnote 10.
SECTION VI - LABORATORY HAZARDS
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 28Footnote 29.
SOURCES/SPECIMENS: Stool Footnote 1Footnote 2Footnote 6Footnote 7, infected tissue Footnote 20, infected soil Footnote 1Footnote 2Footnote 6Footnote 7.
PRIMARY HAZARDS: Direct contact via unprotected skin or oral mucosa with infected materials Footnote 1Footnote 2Footnote 6Footnote 7, accidental inoculation Footnote 28.
SPECIAL HAZARDS: None.
SECTION VII – EXPOSURE CONTROLS / PERSONAL PROTECTION
RISK GROUP CLASSIFICATION: Risk Group 2Footnote 30.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 31.
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 31.
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 31.
SECTION VIII – HANDLING AND STORAGE
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 31Footnote 32.
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 31.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled Footnote 31.
SECTION IX - REGULATORY AND OTHER INFORMATION
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
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- Footnote 20
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