Scalable and sustainable models to control tapeworms through pig vaccination
Taenia solium, commonly known as the pork tapeworm, is a parasite transmitted to humans from pigs and vice versa. The adult form of T. solium causes taeniasis in humans, and the larval cyst causes cysticercosis in pigs. If humans ingest the eggs of T. solium, the larval cysts can lodge in the central nervous system, causing neurocysticercosis and lead to seizures, epilepsy, and other neurological disorders. These forms of the parasitic disease are neglected and predominantly affect poor communities due to lack of sanitary conditions. In endemic communities, up to 70% of cases of epilepsy have been associated with cysticercosis. Although anyone can be infected by the parasite, infection carries a greater stigma and risk of gender-based violence for women, as epilepsy is often associated with accusations of witchcraft. In many regions, pigs are a preferred species for women smallholder farmers and are an important source of livelihoods.
While pigs are responsible for maintaining the transmission cycle of the parasite, they do not get sick. In fact, they can harbour hundreds of the parasites and still look healthy. Because the transmission cycle involves deficient sanitation where pigs come into contact with human feces, the disease is endemic in the poorest and most vulnerable communities, in which pigs roam free and open defecation is common. The disease does not affect commercial pig-production systems that follow standard sanitary practices.
Although there is an effective livestock vaccine against T. solium, called Cysvax, vaccine-adoption rates remain low. An important factor that influences the demand for the vaccine is that porcine cysticercosis usually does not cause direct economic loss to the owners of the animals. As infected pigs do not show any outward signs of infection, owners are often unaware of the problem. In addition, livestock keepers are not always aware that infection in pigs is linked to neurocycticercosis in humans.
Testing a novel One Health approach
This project proposes to test a disease-control model that makes use of a One Health approach. It involves coordinated interventions to target and control the disease in both human and pig populations and eliminate the disease in targeted regions of Madagascar. This is important because the parasite’s cycle involves transmission between human and pig hosts, and it can survive for years in either host. The project will include vaccination and drug interventions to treat the cysts in pigs, as well as the treatment of human tapeworm carriers. Compared to previous control trials conducted in several parts of the world, which proved to be extremely expensive, costs will be kept low through a reduced frequency of interventions. The project will also include community engagement to increase awareness of the disease, as well as to promote public health measures and safer pig-rearing practices to reduce disease transmission between pigs and humans.
A key outcome of the project will be the sustainable reduction in the transmission of T. solium with a view to eventually eliminating it as public health problem in the targeted areas. If this is achieved, it will no longer be necessary to continue the Cysvax vaccinations in those regions. This would contribute to better health for at-risk populations, diminish the occurrence of gender-based violence attributed to epilepsy in women and girls, and reduce economic losses. If the model for the One Health approach proves successful and cost-effective, it could potentially be replicated in other regions where the disease is endemic, and contribute to a strategy for a global porcine cysticercosis and neurocysticercosis eradication campaign.
The project is a collaboration between the University of Melbourne in Australia and the Centre National de la Recherche Appliquée au Développement Rural in Madagascar.
- Duration: 30 months
- Budget: CA$1.8 million
The project is funded through the Livestock Vaccine Innovation Fund, a partnership of the Bill & Melinda Gates Foundation, Global Affairs Canada, and IDRC.