Cysticercosis kills upwards of 50,000 people every year, nearly all in the developing world; those who are not killed suffer symptoms ranging from epileptic seizures to blindness, as the disease attacks the brain and nervous system. Millions of people suffer from the disease, which is caused by tapeworms. (Here's the fact sheet from the US Centers for Disease Control.) But the life-cycle of the parasite requires an intermediate host -- pigs -- and that turns out to be the ideal point of intervention.
New Scientist reports on the work of researchers at the University of Melbourne, Australia. The scientists have developed a vaccine that triggers the production of antibodies in pigs that cause the eggs of the tapeworm to burst before developing further. The work has been remarkably effective:
Small-scale trials, in which eggs isolated from adult tapeworms were fed to up to 30 pigs, have already been conducted in Mexico, Peru, Cameroon and Honduras. The vaccine provided between 99.5 and 100 per cent protection in every trial. The Melbourne researchers, together with collaborators in Lima, Peru, now have plans for larger field trials in which the pigs will be allowed to forage as normal, they reported at a conference on parasitology in Melbourne last week. At the moment, two vaccinations about one month apart provide several months of immunity. The team's aim is to provide lifelong immunity with one or two shots, though they say the vaccine will still be beneficial even it has to be given yearly.
Although the same type of vaccine could work in humans, it's less costly -- and much faster -- to develop and deploy animal vaccinations. Existing tapeworm infections in humans can be treated effectively (if caught soon enough); by breaking the cycle in pigs, the spread of the disease can be prevented.
Aside from being of enormous benefit in the developing world, this is a good example of the value of looking at the ecology of infection.