Pork infected with pig tapeworm cysts (photo credit: ILRI/Fahrion).
An article in this month’s Discover Magazine reports on infection with pig tapeworm, or cysticercosis, a target disease of the International Livestock Research Institute (ILRI) that is rare in the industrialized world but unfortunately not at all rare in poor countries.
‘. . . Before they become adults, tapeworms spend time as larvae in large cysts. And those cysts can end up in people’s brains, causing a disease known as neurocysticercosis.
‘“Nobody knows exactly how many people there are with it in the United States,” says Nash, who is the chief of the Gastrointestinal Parasites Section at NIH. His best estimate is 1,500 to 2,000. Worldwide, the numbers are vastly higher, though estimates on a global scale are even harder to make because neurocysticercosis is most common in poor places that lack good public-health systems. “Minimally there are 5 million cases of epilepsy from neurocysticercosis,” Nash says. . . .
‘The closer scientists look at the epidemiology of the disease, the worse it becomes. . . . Earlier this spring, Nash and colleagues published a review of the scientific literature and concluded that somewhere between 11 million and 29 million people have neurocysticercosis in Latin America alone. Tapeworms are also common in other regions of the world, such as Africa and Asia. “Neurocysticercosis is a very important disease worldwide,” Nash says.
‘The alarming illness occurs when tapeworm larvae lose their way. Normally, Taenia solium has a life cycle that takes it from pigs to humans and back to pigs again. . . . But sometimes tapeworms take a wrong turn. Instead of going into a pig, the eggs end up in a human. This can occur if someone shedding tapeworm eggs contaminates food that other people then eat. When the egg hatches, the confused larva does not develop into an adult in the human’s intestines. Instead, it acts as it would inside a pig. It burrows into the person’s bloodstream and gets swept through the body. Often those parasites end up in the brain, where they form cysts. . . .
‘Although finding a better cure is important, Nash is more interested in preventing tapeworms from getting into human brains in the first place by breaking their life cycle. A favored strategy is identifying people who have adult tapeworms in their bodies and giving them drugs to kill the parasites. It is also possible to vaccinate pigs so that they destroy tapeworm eggs as soon as they ingest them.
‘None of this is rocket science—which makes Nash all the more frustrated that so little is being done. “I see this as a disease that can be treated and prevented,” he says. But there are precious few resources available for treatment and little recognition of the problem. “All of this seems to be very feasible, but nobody wants to do anything about it.”’
Read the whole article at Discover Magazine: Hidden epidemic: Tapeworms living inside people’s brains, 15 May 2012 (June 2012 issue).
Read about an ILRI Sep 2011 workshop on cysticercosis: Market incentives–not top-down regulation–needed to help poor farmers take advantage of East Africa’s burgeoning pig industry, 17 Jan 2012.
Read more about a People, Animals and their Zoonoses (PAZ) project of the University of Edinburgh and ILRI, which is taking a close look at the health of people and livestock in a densely populated region of western Kenya. One of the health issues project members are investigating is the role played by pigs in transmitting zoonotic diseases and the risk factors for human infection in western Kenya. PAZ is funded by the Wellcome Trust and led by Eric Fevre.
ILRI Clippings Blog: Forestalling the next plague: Building a first picture of all diseases afflicting people and animals in Africa, 11 Apr 2011.
See also ILRI photofilm: The connection between animal disease and human health, Jan 2012, duration: 01:55. This brief film describes the work and expected impact of the ILRI-Welcome Trust ‘People Animals and Their Zoonoses Project’ that is investigating the impact of disease pathogens in people and animals in Busia District, in western Kenya.
And the ILRI photofilm: Dying for meat, Feb 2012, duration: 2:56. This short film features small-scale butchers and consumers from Nairobi, Kenya, and a commentary by Delia Grace, an ILRI veterinary epidemiologist who is leading multi-institutional research on agriculture-associated diseases, on issues that connect animal and human health.