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Taenia solium (pork tapeworm) symptoms
Lifecycle of taenia solium
Taenia solium treatment
How do you prevent pork tapeworm infection?
Pork tapeworm research project in Uganda
Taenia solium infection – also known as pork tapeworm – is widely endemic across Central, South America, sub-Saharan Africa and Asia. The parasite causes neurocysticercosis (NCC), which has been identified as the leading preventable cause of epilepsy in low- and middle-income countries.
It is estimated that NCC accounts for approximately one third of epilepsy cases in countries where T. solium is endemic.
The parasite thrives in areas of unsafe sanitation, where the environment is contaminated with T. solium eggs as humans openly defecate in outdoor areas, allowing constant exposure to free-ranging pigs. Beyond the human health burden associated with NCC, smallholder pig farmers face a substantial economic burden. Pig cysticercosis reduces the value of pork in food-value chains and leads to infected carcasses being discarded.
One study in Tanzania showed that T. solium accounted for $USD 5 million spent due to NCC-associated epilepsy and $USD 2.8 million lost due to porcine cysticercosis in 2012.
Human taeniasis can be treated with taenicides including praziquantel and niclosamide. Symptomatic therapy, antiparasitic treatment and surgical intervention are options to manage/treat human neurocysticercosis. Porcine cysticercosis can be treated with oxfendazole (see figure).
The lifecycle of Taenia solium is complex, involving pigs which act as the intermediate host (porcine cysticercosis) harbouring the larval-stage after consuming T. solium eggs in the environment, and humans which can act as the definitive host (human taeniasis) after consuming the larval-stage from (undercooked or raw) pork meat.
Humans can also act as an accidental intermediate host (human (neuro) cysticercosis).
Opposite: Schematic representation of the transmission cycle of Taenia solium, epitomising a One Health approach. The human (blue), animal (orange), and environment (green) components are represented by inter-locking sections that intersect and form a whole entity whose parts cannot be tackled in isolation. The purple boxes indicate the parasite stages responsible for the main human health burden (associated with neurocysticercosis) and economic impact (due to both neurocysticercosis and porcine cysticercosis) of the disease. The grey boxes highlight the points in the parasite’s life-cycle upon which currently available intervention strategies operate: dark grey boxes indicate biomedical approaches (treatment, vaccination); light grey boxes indicate behaviour- and environment-focussed interventions. Modified from Dixon et al. (2019), and published in Dixon et al. (2021)
In humans, properly cooking pork meat is important. Strengthening meat inspection and veterinary capacity to inspect carcasses at slaughter points can limit the larval-stage infection entering the food chain. There is a highly effective vaccine (Tsol18: Cysvax™) that can be used to prevent larval-stage infection in pigs. Minimising or preventing pigs from freely roaming and scavenging for foodstuffs in a community prevents exposure, however many poor farmers rely on this low-cost approach for raising pigs. Improving hygiene and sanitation standards, including building latrines and encouraging use is critical to preventing the exposure of T. solium eggs in humans (therefore preventing human neurocysticercosis).
Implementing partners: Bayer, Merck
Timescale: Feb 2021 – Feb 2022
A collaboration between Bayer AG, Merck and Unlimit Health looked at the impact of large-scale distribution of the drug praziquantel (PZQ) and its impact on T. solium in Uganda.
Robust evidence confirms the long-term positive impact of deworming programmes on affected communities. However, there is little evidence on the additional benefits of treatment with PZQ on other parasitic worms such as T. solium, thus potentially underestimating the true impact. T. solium and schistosomiasis, both neglected tropical diseases (NTDs), are co-endemic across much of sub-Saharan Africa (Figure 1), indicating that there is the potential for impact of schistosomiasis control programmes on both infections across the region.
Uganda has the highest pork consumption per capita in East Africa (3.4 kg per capita), with smallholder pig farming common across much of the country. In addition, studies indicate a high prevalence of cysticercosis in Uganda among both humans and pigs.
Unlimit Health has been supporting the implementation of a national SCH control programme in Uganda, based on large-scale praziquantel administration since 2002, providing a detailed country focus for conducting a modelling-based assessment of the impact of such programme on T. solium.
Bayer AG have recently committed to donating praziquantel and niclosamide specifically for control of T. solium, and it is likely that treating adults alongside school-aged children will be needed to achieve targets in the World Health Organisation (WHO) NTD roadmap 2021-2030.
The project started in February 2021 to run for a 12 month period, and generated results for key stakeholders alongside submission of research to peer-reviewed journals over this timeframe.
Read the news piece about this project.
Read more about our approach to monitoring and evaluation.