Hookworm infection: symptoms, how it is caught and how it is treated

Hookworms are parasitic worms that live in the small intestine. WHO groups them with roundworm and whipworm as soil-transmitted helminths, naming the main hookworm species as Necator americanus and Ancylostoma duodenale. These infections are among the most common in the world, with WHO estimating about 1.5 billion people, or 24% of the world population, infected with soil-transmitted helminths.

The burden falls on communities with poor access to clean water, sanitation and hygiene in tropical and subtropical areas. In the UK, hookworm is uncommon and is mostly seen in people returning from travel or residence in affected regions, which is why the NHS asks about travel in the last two years.

Eggs pass out of an infected person in faeces. In places without adequate sanitation, they contaminate soil. WHO explains that hookworm eggs need about 3 weeks to mature in soil before they become infective, hatch into larvae and can then penetrate the skin, so infection happens primarily from walking barefoot on contaminated soil.

There is no direct person-to-person transmission, or infection from fresh faeces, because eggs need that time in the soil. WHO also notes that hookworms do not multiply in the human body, so re-infection happens only through contact with infective stages in the environment.

The NHS lists similar routes for worms in general: touching soil or swallowing water or food with worm eggs in it, and walking barefoot on soil containing worms, which it says is only a risk in parts of the world without modern toilets or sewage systems.

Many people have no symptoms. WHO says that infections of light intensity usually do not cause illness, while heavier infections can cause diarrhoea and abdominal pain, malnutrition, general malaise and weakness, and impaired growth and physical development in children. A red, itchy, worm-shaped rash on the skin, which the NHS shows as a sign of hookworm, is one of the visible signs of larvae under the skin.

The most important complication is anaemia. WHO explains that worms feed on host tissues including blood, leading to a loss of iron and protein, and that hookworms cause chronic intestinal blood loss that can lead to anaemia, especially in adolescent girls and women of reproductive age. Tiredness, pallor and breathlessness can therefore be the main features.

The NHS says you might be asked to provide a sample of poo so it can be tested for worm eggs. All worm infections are treated in a similar way: if you have worms, a GP will prescribe medicine to kill them, taken for 1 to 3 days. Worms in the gut eventually pass out in the poo, which you may not notice.

The NHS advises going back to the GP if symptoms do not get better in 2 weeks or you keep passing live worms.

To avoid re-infection or passing worms to others, it is important in the weeks after starting treatment to wash your hands after using the toilet, before eating or preparing food, and regularly during the day. The people you live with may also need treatment.

WHO lists control measures as periodic deworming, health and hygiene education, and improved sanitation. For travellers, the NHS advises washing hands before eating or preparing food and after touching soil or using the toilet, drinking only bottled or boiled water in high-risk areas, and not walking barefoot in high-risk areas.

It also recommends thoroughly washing garden-grown fruit and vegetables, avoiding raw fruit and vegetables in high-risk areas, deworming pet dogs and cats regularly and disposing of their poo promptly, and not eating raw or undercooked pork, beef or freshwater fish.