ICEH Resources Information Sheet

HOOKWORM

Pronunciation: Hook-worm

What causes Hookworm?

Hookworm is a common, chronic (long-term) parasitic infection that is caused by the worms Necator americanus (Ne-kay-tor a-mare-e-caan-us) and Ancylostoma duodenale (An-cy-clo-stoma duo-dean-al). Only A. duodenale occurs in Australia.

Humans are the main reservoir (source) of N. americanus and A. duodenale, and it is estimated that around 20% of the world population carries this parasite. Hookworm is not a Nationally Notifiable Disease.

What does it look like?

Adult females (A. duodenale) are 10-30mm long and 0.6mm wide, and males are 8-11mm long and 0.45mm wide. Eggs are 0.06mm x 0.04mm in size, and can only be seen with a microscope. The same is true with larvae (immature worms).

Hookworm in Australia

Where does it occur?

Hookworm is endemic (constantly occurs) in many tropical and subtropical areas, especially when human faeces (shit) is not disposed of in a sanitary manner.

Australian / Indigenous Significance

It has been reported that hookworm infections (A. duodenale) are still common in northern Australian communities, particularly amongst Indigenous Australians.

Hookworm infections are a common cause of anaemia and iron deficiency in Aboriginal women and children.

Symptoms: What to look out for?

Symptoms usually vary according to the severity of infection. It is common for people with light infections to be asymptomatic (not feel sick). Heavy infections may cause a person to become anaemic (pale and weak) due to worms feeding on the host’s blood. Other symptoms include fever, abdominal pain, weight loss, constipation (unable to pass faeces), or diarrhoea (runny tummy).

Chronic infections in children may slow growth and thinking ability, and may cause a potbelly appearance.

Occasionally coughing and upper respiratory tract infections may occur from the worms moving through the lungs. Death rarely occurs from infection.

How do you diagnose (confirm) a case?

Cases of hookworm are diagnosed by finding eggs in stool samples (faeces) using a microscope. However, no eggs may be present in the early stages of infection, and other tests like blood examination and endoscopy may need to be done to check for hookworm.

How does it spread?

People can become infected with hookworm by walking bare foot on soil that contains infective larvae. Other infection routes include drinking water or eating food contaminated with larvae. Cases of mother to baby transfer of the hookworm A. duodenale have also been reported.

How does it reproduce?

Hookworm eggs are deposited on the ground in faeces, and will hatch into non-infective larvae if the right soil type, water quantity, and temperature are present.

The larvae take 7-10 days to become infective, and can then penetrate human skin (usually the foot). Itchy skin or ground itch occurs where the larvae penetrate the skin.

On entry, the larvae make their way to the lungs by the blood and immune systems. Then they are coughed up and swallowed into the digestive system. The larvae attach to the small intestine wall by hooks, and develop into adults (6-7 weeks). Adults produce 15 000 to 20 000 eggs a day which exit in the faeces.

How infectious is it?

Hookworm is not transmitted from person to person. Infected people can contaminate soil for several years if the right conditions are present. Larvae can survive in dirt for several weeks but do not survive in clay, dry or hard packed soils, or in temperatures that are freezing or higher than 45ºC.

How long does it take for symptoms to appear?

Symptoms can take weeks or months to develop depending on the severity of infection, and the amount of iron in an infected person’s diet. Ancylostoma duodenale can stay dormant in the body for 8 months.

Who is most at risk?

Anyone can get hookworm. However, agricultural workers in endemic areas have a higher risk of being infected. The illness can be more serious in babies, children, pregnant women and people with poor diets.

How do we prevent it from occurring?

Public education on the dangers associated with dirt contaminated with human, dog or cat faeces can help reduce the number of cases of hookworm infection. Education programs should highlight the importance of:

• Disposing of human faeces in a sanitary way so it doesn’t contaminate soil.
• Wearing covered footwear in areas where the disease is endemic.
• Washing hands after going to the toilet, and before handling or eating food.
• Using safe food preparation practices.
• Keeping dogs and cats out of areas used for sleeping and eating.
• Checking dogs and cats in contact with people regularly for worms, and treating where necessary. Stray animals should be culled.
• Cleaning of animal living areas regularly, and hygienically collecting and disposing of faeces. Cats and dogs need to be kept out of areas where food is grown, and prevented from shitting in areas next to houses, or where children play.
• Checking sewage systems often to ensure they are not broken or faulty.

How can it be controlled?

Cases of hookworm should be reported to the local health clinic or authority. Faeces samples of household members and close contacts should be collected and tested to find out who has been infected. Potential sources of infection like pets should be checked and treated when required.

Medicines are available to get rid of hookworm in humans and in animals. Programs can be conducted in endemic areas to educate residents about hookworm, and to identify and treat infected people.

Case Study

Towards the Eradication of Hookworm in an Isolated Australian Community
(Thompson et al, 2001)

In 1992, a survey was conducted in a remote coastal community (population around 350). The survey found that around 77% of the community was infected with A. duodenale, and around 93% of children aged 5 - 14 years were infected with the parasite. At first the medicine pyrantel and environmental and health strategies were used to try to eradicate hookworm in the community. Unfortunately the campaign was unsuccessful due to A. duodenale resistance to pyrantel.

A second campaign (1993 - 1999) used the drug albendazole to treat infected people, and continued on with health education and environmental management programs (improved housing and sewage systems, rubbish collection etc). This campaign also monitored hookworm infection in the population, which was important because lack of surveillance has been highlighted as a contributing factor to the failure of other hookworm eradication programs.

Firstly the infection status of the whole community was calculated, and then mass treatments were given. Regular checks were carried out to look for the parasites A. duodenale, Giardia and Hymenolepis nana. The original mass treatment (1993) reduced human hookworm infections from 80% to 0% of the population within 30 days. However, over a 3-year period the number of infected people increased to around 40% of the population when no further treatments were given.

Regular treatments were started, and currently hookworm infections occur only in around 2.6% of the population. Presently, hookworm is under control in the community, unless someone reintroduces it. However, any outbreaks could be quickly stopped by regular use of special drugs, although care is needed to ensure the parasite does not become resistant to these drugs.

Glossary

Resources

Community Education Flyer to print out
Available at: iceh.uws.edu.au/fact_sheets/hookworm_flyer.pdf
[1 page sheet for community information, 109KB PDF file]

Chin, J., 2000, Control of Communicable Disease Manual, 17th edn, American Public Health Association, Washington DC, pp. 497-499.
[Book on infectious diseases that is often referred to in health departments (technical language)]

Despommier, D.D., Gwadz, R.W., Hotez, P.J. 1995, Parasitic Diseases, 3rd edn, Springer-Verlag, New York, pp. 151-159.
[Book on diseases caused by parasites (technical language)]

Fact Sheet: Parasitic Roundworm Diseases, 2001. NIAID, United States. Available at: www.niaid.nih.gov/factsheets/roundwor.htm
[American fact sheet on worm diseases, good for general community]

Fact Sheet: Hookworm Infection, 1999. CDC, Atlanta. Available at: www.cdc.gov/ncidod/dpd/parasites/hookworm/factsht_hookworm.htm
[American fact sheet on hookworm, good for general community]

Fernando, R.L., Fernando, S.E. & Leong, A.S.Y. 2001, Tropical Infectious Diseases: Epidemiology, Investigation, Diagnosis and Management, Greenwich Medical Media Ltd, London, pp. 91-94.
[Book that focuses on infectious diseases in Australia (technical language)]

Griffiths, O. & Henderson, H. 1997, Environmental Health for Aboriginal Communities: A Training Manual for Environmental Health Workers, Office of Aboriginal Health, East Perth, pp. 16-28.
[Training manual for Environmental Health Workers in Western Australia]

Grove, D.I. 1993, ‘Worms in Australia’, Medical Journal of Australia, Vol 159, pp. 464-466.
[Article on worm related diseases that occur in Australia (technical language)]

McCarthy, J.A. & Garrow, S.C. 2002, ‘Parasite elimination programs: at home and away’, Medical Journal of Australia, Vol. 176, pp. 456-457.
[Journal article on parasite control programs in Australia (technical language)]

Porciv, P. 1998, ‘Zoonotic Hookworm Infections’, in Zoonoses, eds S.R. Palmer, Lord Soulsby & D.I.H. Simpson, Oxford University Press, New York.
[Book on diseases that spread from animals to humans (technical language)]

Reynoldson, J.A. et al, 1997, ‘Failure of pyrantel in treatment of human hookworm infections (Ancylostoma duodenale) in the Kimberly region of the north west Australia’, Act Tropica, Vol 68, Issue 3, pp. 301-312.
[Case study on use of a medicine to treat hookworm (technical language)]

Thielberger, N. & McGregor, W. 1994, Macquarie Aboriginal Words: a dictionary of words from Australian Aboriginal and Torres Strait Islander languages, Macquarie Library Pty Ltd, NSW.

Thompson, R.C.A. et al. 2001, ‘Towards the eradication of hookworm in an isolated Australian community’, The Lancet, Vol 357, pp. 770-771.
[Case study on hookworm control program in a community (technical language)]

WHO, 1994, Report of the WHO Informal Consultation on Hookworm Infection and Anaemia in Girls and Women, WHO, Geneva.
[In depth report on Hookworm infections in females (technical language)]

Created November 2003
by Margaret Davidson