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The worm that turned – parasitic worms in Kenya and Uganda

1 Nov, 2011

Mother and baby clinic, Entebbe, Uganda.

Parasitic worms are a major cause of malnutrition in Africa. Health researchers have made major strides in combatting these infections, but some treatments are also revealing a new wave of health concerns, as Meera Senthilingam reports.

As you drive through the region of Mwea in Kenya, rice fields span as far as the eye can see. The land is fertile and rich in agriculture with numerous farmers at work harvesting their grain. This is not a place where children go hungry. But, it is a place where many children are malnourished. The cause? Parasitic worms.

Worm infections have long been off the radar of high-income countries owing to increased sanitation and successful public health campaigns. The anaemia and vomiting caused by infection with worms such as the schistosomes or soil-transmitted helminths such as hookworms are not of big concern to the North. But the swamp-like conditions of rice fields and absence of pit latrines, combined with hot equatorial climates, make regions like Mwea perfect for parasitic worms to flourish, which they have for many years.

This is a situation the Kenya Medical Research Institute (KEMRI) is not taking lightly. With support from the Wellcome Trust, they’ve been developing ways to target infection at the source: schoolchildren.

DiFathers primary school in Mwea, Kenya.

Back to school

School-based deworming programmes are now commonplace throughout low-income countries, improving both child health and development. In Kenya, the introduction of free primary school education has seen school attendance figures rise dramatically, making school-based treatment ideal to reach the 8 million children at risk of infection.

Driving through the farmland of Mwea, Dr Charles Mwandawiro, Assistant Director of KEMRI, points out to me numerous schools along the way. These are where KEMRI have been running their pilot programme since 2004, providing drugs such as albendazole and praziquantel (against soil-transmitted helminths and schistosomiasis, respectively).

“Our project has worked with 92 schools, reaching up to 40 000 children,” says Mwandawiro. “Schistosomiasis infection fell from 80 per cent in 2003 to 10 per cent in 2009 and hookworm from 40-45 per cent to practically zero.”

The project’s success led to the introduction of a national deworming programme in 2009 reaching 3.6 million children. Regions at most risk were identified thanks to a Trust-funded project led by Dr Simon Brooker, who mapped regions of Africa (and since worldwide) according to the prevalence of infection. The maps identified three regions to target in Kenya: the Western and Nyanza Provinces by Lake Victoria and the central and coastal provinces, all of which have the hot, moist conditions conducive to infection.

At a cost of around 2 cents per tablet for drugs like albendazole, a national programme is extremely cost efficient, fitting comfortably into the disconcertingly low Kenyan health budget of $6 per person.

But the ease of reinfection, either by walking barefoot (allowing hookworm larvae to penetrate the skin) or by forgetting to wash your hands after a toilet break, means that simply providing drugs is not enough. Health education is crucial.

We arrive at DiFathers primary school in the Kirinyaga County of Mwea – home to 520 students, many of whom greet us alongside their parents.

“We have big water containers with taps on them outside each classroom for children to wash their hands…the latrines are properly cemented with PVC pipes inside,” says Alesious Munyui Kithiri, the school’s headmaster, clearly proud of how his school has changed. “The children now want to come to school as they feel comfortable and happy here.”

Studies have shown that treating worms in schoolchildren benefits their families and surrounding communities as well. Children are the main source of transmission, so treating them stops infection at its source. And the kids also teach their parents and relatives a thing or two – adults pick up good hygiene practices from their children, keeping infection at bay.

A clinician makes a home visit, Entebbe, Uganda.

New disease

In low-income countries, worm treatment programmes target vulnerable members of the population. Alongside children, pregnant women also receive complimentary deworming in countries such as Kenya and Uganda.

But new developments bring new, unexpected problems. Research at the Uganda Viral Research Institute (UVRI) has identified an increased risk of allergy in the children born to these women.

The hygiene hypothesis has long stated that a decrease in worm infections leads to increased prevalence of allergy. This is supported by the increased levels of allergy seen in high-income countries. Scientists suggest the presence of worms downregulates the heightened immune response seen in allergies such as eczema and asthma. But the interaction of worm infection and mother and baby was previously unknown.

A study led by Alison Elliott at UVRI and funded by the Trust sampled 2500 pregnant women in Entebbe, a Ugandan town on the shores of Lake Victoria.

“When we started our study, 68 per cent of women in Entebbe had at least one form of worm infection,” says Elliott. “We hoped we might see benefits treating worms in pregnancy – maybe helping the babies’ response to infection, improving birthweight or reducing perinatal mortality. But we didn’t see this. What we did see was the increased rate of eczema.”

Incidence of eczema doubled in mothers receiving albendazole against hookworm infection and more than doubled in in mothers receiving praziquantel against schistosomiasis infection.

Elliot’s research in no way calls for worm treatment to stop in pregnant women because there are numerous health benefits associated with deworming. But it highlights a problem that countries like Uganda and Kenya are facing: they don’t have the resources to handle conditions like eczema or asthma.

It’s easy to assume the residents of East Africa have more important diseases to worry about than allergies. But the skin irritation associated with eczema can lead to open wounds susceptible to infections such as septicaemia, and limited drug availability for asthmatics could result in severe wheezing attacks.

The resource-poor setting means a disease that is manageable in the North could be fatal in a low-income country. Moreover, as you travel through Entebbe – past the numerous company buildings, institutes and developments – you realise that these problems are going to become increasingly common as the population here, like that of many African cities, becomes increasingly middle-class.

“Africa is changing rapidly,” says Elliott. “About 30 per cent of Africans are now said to be middle class [and] rather little is known about allergy in this setting. Middle-class Africans may be less aware of the best ways to manage allergies than they are of how to manage malaria”.

Elliott’s group has new funding through which they hope to study allergy prevalence, and changes in this, as Entebbe continues its rapid urbanisation. They also hope to expand to study the more rural island communities nearby to compare the effects of intensive worm control.

As we prepared to depart on our drive home, I met Jennifer Tushemerirwe, a teacher with four children. Her home is spacious, with mosquito nets on each bed and a beautifully well-kept garden. She told me her concerns aren’t the worm infections or even malaria. It’s new conditions like the eczema suffered by one of her children; a fear of the unknown.

Meera Senthilingam

Meera is a freelance science journalist.

Image Credit: Uganda Virus Research Institute (top, bottom), KEMRI.
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