How vaccinating a pig can save a child from epilepsy
A tapeworm larva that infects millions of people across the developing world can cause epilepsy and death. Cysvax is a vaccine that stops the larva infecting pigs, in turn protecting humans.
A pig vaccine stops the spread of a tapeworm and prevents a form of human epilepsy in the developing world. The vaccine, Cysvax®, was based on research from the University of Melbourne.
The World Health Organization (WHO) recommends a combination of the vaccine and anti-parasitic drugs to stop the spread of the pork tapeworm, Taenia solium. The tapeworm passes from pigs to humans, where it can lead to epilepsy and death.
Use of Cysvax also protects the income of farmers, as tapeworm-infected pig meat is less valuable.
Cysvax was first registered for sale in India in 2016.
The WHO has identified the pig tapeworm T. solium as a leading cause of death from food-borne diseases. Around 50 million people are infected worldwide.
In humans, infection with the larval form causes cysts throughout the body. This is called cysticercosis. Cysts in the brain or spinal cord can lead to confusion, headaches, blindness, seizures and death. This form of the disease, called neurocysticercosis, causes around 30 per cent of cases of human epilepsy in areas where the tapeworm is found.
As many as 8.3 million people worldwide have neurocysticercosis.
When pigs and humans live in close quarters with poor hygiene, the tapeworm cycles between the two species. Pigs are infected when they eat human faeces containing tapeworm eggs. Humans become infected when they eat pork containing tapeworm eggs.
Cysticercosis is common in subsistence farming communities across Latin America, Southeast Asia and Africa. The tapeworm is rare in developed countries, although there are around 1000 cases of cysticercosis in the USA each year.
The vaccine was developed by a research team led by Professor Marshall Lightowlers from the Faculty of Veterinary and Agricultural Sciences at the University of Melbourne. As animal vaccines are easier and cheaper to develop than human vaccines, the researchers targeted pigs infected with T. solium.
In 2006, they extracted a gene from the tapeworm that encodes a protein called TSOL18. They used the gene to develop a recombinant vaccine based on this protein. The vaccine triggers an immune response in pigs that attacks tapeworm embryos.
The vaccine was tested in trials in Mexico, Cameroon, Honduras and Peru. It protected 99–100 per cent of vaccinated pigs from tapeworm infection.
In a mass treatment trial in Northern Peru, the vaccine was administered in combination with antiparasitic drugs to more than 50 000 pigs. More than 80 000 people in the region were treated with antiparasitic drugs. The intervention eliminated transmission of the disease in the communities involved in the trial.
In 2011, the University of Melbourne collaborated with the Global Alliance for Livestock Veterinary Medicines (GALVmed), a UK-based charity, to develop the vaccine for commercialisation. The University of Melbourne chose not to patent the vaccine technology, to reduce the costs of vaccination and enable widespread use of the vaccine. GALVmed entered into a non-exclusive agreement with Indian Immunologicals Limited to produce and sell the vaccine.
In 2016, Cysvax became the first vaccine licensed for cysticercosis.
In field trials of Cysvax and antiparasitic medication for pigs in Nepal, Uganda, Tanzania and Zambia, the combined treatment has eliminated any potential for treated animals to transmit the disease to humans.
NHMRC Project Grant (1043327)
NHMRC Research Fellowship (1105448)
Poudel I et al. (2019) Implementation of a practical and effective pilot intervention against transmission of Taenia solium by pigs in the Banke district of Nepal. PLoS Neglected Tropical Diseases 13: e0006838. doi: 10.1371/journal.pntd.0006838
Assana E et al. (2010) Elimination of Taenia solium transmission to pigs in a field trial of the TSOL18 vaccine in Cameroon. International Journal for Parasitology 40(5): 515-519. doi: 10.1016/j.ijpara.2010.01.006
Lightowlers MW (1999) Eradication of Taenia solium cysticercosis: a role for vaccination of pigs. International Journal for Parasitology 29(6): 811-817. doi: 10.1016/S0020-7519(99)00051-X
Image: Marshall Lightowlers
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