Breaking the cycle of the zoonotic disease Neurocysticercosis

Much is being discussed about zoonotic diseases currently as a result of the ongoing COVID-19 pandemic, which scientists predict likely emerged from wholesale food market in Wuhan City in China. Globally, it is estimated that 75 per cent of emerging human diseases in the last three decades have originated from animals, increasing the urgency to identify strategies and control tools that will prevent and control zoonotic diseases.

GALVmed has been working on neglected zoonotic diseases that have the most severe constraints on small-scale agriculture in sub-Saharan Africa and South Asia. Take the case of Porcine Cysticercosis (PC), which is almost exclusively transmitted between humans and pigs. Porcine Cysticercosis is caused by Taenia solium and humans are the definitive hosts for Taenia solium. People can also act as intermediate hosts and develop human cysticercosis or neurocysticercosis, which can cause severe headaches, blindness, convulsions, epileptic seizures and can be fatal. Taenia solium is the cause of 30% of epilepsy cases in many endemic areas where people and roaming pigs live in close proximity. In high risk communities it can be associated with as many as 70% of epilepsy cases.

Porcine cysticercosis also has a devastating effect on the economy. The farmers incur serious financial losses when their infected pigs cannot be sold, are sold at reduced prices, or are condemned without compensation upon slaughter.

Attempts to control this infection through increased public health education, sanitation, improved animal husbandry and meat inspection, have proven largely unsuccessful in eradication of the disease. Hence, GALVmed and partners set out to develop control tools (vaccine, diagnostics and therapeutics) for porcine cysticercosis in a bid to stop the cycle of infections from pigs to humans.

Since the early 2010s, GALVmed worked with University of Melbourne, Australia, and Indian Immunologicals Limited (IIL) to develop the TSOL18 vaccine and make it available for use in endemic countries. The CYSVAX™ vaccine for porcine cycticercosis was licensed for the first time in India in 2016.

As part of this collaboration, GALVmed conducted five field trials in smallholder pigs of different regional settings in Asia and Africa to evaluate how the TSOL18 vaccine and the benzimidazole drug Oxfendazole, a pig de-wormer, can be integrated into effective PC control programmes. All studies showed that the TSOL18 vaccine achieves complete elimination of transmission of the parasite by pigs, when concurrently administered with oxfendazole (Paranthic 10%™). This marked a major step towards the integrated control of this important human disease. In addition, GALVmed explored the status of knowledge, attitudes and practices among pig farmers in smallholder settings and farmers’ willingness to pay for Cysvax® and Paranthic 10%™. And while the ‘added value’ of the porcine cysticercosis vaccine will accrue more to the public health sector than the farmer, the concurrent deworming could potentially give economic benefits to farmers through improved pig weight which give the farmers premium prices when selling their pigs. This addresses both the human health and economic aspects of this zoonotic disease.

Written by Beatrice Ouma