Veterinary research into parasite control in pigs through vaccination has the potential to reduce a serious brain disease in humans in developing nations. Nerissa Hannink reports.
A vaccine developed by University of Melbourne researchers has been found to totally eliminate the spread of a fatal form of brain disease.
A recent pilot trial was undertaken in Cameroon against the parasite Taenia solium which causes 50 million tapeworm infections and 50 000 deaths from brain disease in the developing world each year.
Professor Marshall Lightowlers from the Faculty of Veterinary Science at the University of Melbourne, who led the study, has been striving towards the parasite’s eradication for almost 30 years.
“The trial resulted in the total elimination of transmission of the disease,” he says.
Tapeworms can grow many metres long and live in humans for years without health implications but their eggs can hatch in the intestine and the parasite travels to the brain where it causes the often fatal condition of neurocysticercosis.
The disease results in cysts on the brain and spinal column, which is the most common cause of acquired epilepsy in the developing world and more than half the world’s population living in countries where the parasite is endemic.
“Because the vaccination procedure used was relatively simple and sustainable, it has a genuine potential to form the basis for widespread control of the parasite’s transmission and a reduction, or elimination, of the human brain disease known as neurocysticercosis,” says Professor Lightowlers.
“This disease has been identified as one that could be eradicated from the globe, so this is a very significant hurdle which means the end is well and truly in sight.”
In countries without proper sanitation, and where pigs and humans live in close quarters, there is a constant cycle of re-infection from the parasite. An area in Cameroon was chosen as a trial location because 90 per cent of its pigs are free-roaming and more than 40 per cent of houses that keep pigs do not have a latrine.
Pigs contract the larval form of the parasite from contact with human faeces, it is then passed on to humans who eat improperly cooked pig meat, and then more seriously, from human to human via exposure to tapeworm eggs in human faeces.
The researchers treated 240 three-month-old piglets with a drug to kill off any parasites present before the study. They then vaccinated half of the animals in the hope of preventing any re-infection by the parasite, and distributed the piglets in pairs of vaccinated and unvaccinated animals to households rearing pigs.
After 12 to 14 months, they found live parasites in 20 of the control pigs and none in the vaccinated animals.
The next step for Professor Lightowlers and his team is to determine the optimum vaccine schedule for protection against the Taenia solium parasite.
Further development of the vaccine is receiving support from the Global Alliance for Livestock Veterinary Medicines (GALVmed).
Professor Lightowlers says the vaccination could ultimately be delivered directly in humans, but developing it to that point would be a vastly more expensive process and one that would become irrelevant if the disease could be eradicated in pigs.
The University’s development and testing of the vaccine has been funded by the National Health and Medical Research Council and the Wellcome Trust. The trial results will be published in the next issue of the International Journal for Parasitology.
Editor's Note: Original news release can be found here.