The tapeworm Taenia solium

Taenia solium, otherwise known as pork tapeworm, is a parasite with potentially serious health effects in humans. It infects millions of people worldwide, leading to severe brain diseases, blindness, epilepsy, and death. Countries where where pork production and consumption are coupled with poor hygiene are the worst affected, including large areas of Latin America, Sub-Saharan Africa, and South- and East-Asia, where over 14% of people have experienced an infection at some point [1].

The tapeworm Taenia solium

However, a clear picture of how many people are currently infected by T. solium does not exist, due to the current difficulty in making a diagnosis.

Diagnosis: difficult and expensive

One of the most common diagnostic methods currently available is called enzyme-linked immunoelectrotransfer blot (EITB rES33). It is not only relatively expensive and requires a specialised laboratory setup, but it can only determine whether someone has had the infection at some point in their life, not whether they are currently carrying the parasite. Another method available involves checking faeces for tapeworm eggs under a microscope, which on top of requiring expensive equipment is relatively unreliable [2].

This is why our goal is to develop a cheap, simple and accurate diagnostic test for T. solium infection. By reliably identifying carriers of T. solium, treatment can be directed to those who need it, saving resources and avoiding unnecessary side effects. In this way the most dangerous health effects can be averted. To find out the details of how we plan to achieve this, click here.

Tapeworms pick humans as hosts

The worm reproduces in the human lower intestine, growing up to 4 meters long, and as it releases its eggs they are transmitted into the environment in human faeces. This is where the tapeworm’s story gets more complicated. Two options are possible: one is that pigs come into contact with this faeces, through contaminated environments or foodstuffs, the worm eggs hatch in their gut and the larvae make their way into soft tissue, often settling in muscles or the brain. There they wait as dormant cysts, until humans eat undercooked pork meat containing the parasites, and the cycle continues. In this case, the parasite poses no serious health risk to humans.  However, the other possibility is that a human accidentally eats some tapeworm eggs, for example due to poor hygiene or contaminated food. In this case the worm will treat the human in the same way as a pig, with larvae burrowing into tissue and forming cysts there. When this occurs in the brain, it can have very serious health consequences.

Serious health consequences

Tapeworm cysts are essentially bubbles containing a larva, and they can be surprisingly large. Within the brain they are typically between 5-20 mm in diameter, while in regions surrounding the brain tissue they can reach a diameter of 6 cm. When such cysts form in the brain, the disease is called neurocysticercosis, and it is a major cause of epilepsy. One estimate states that in countries known to have many T. solium infections, 29% of epileptic cases are caused by such neural cysts [3]. Worldwide it is conservatively estimated that the number of people suffering such extreme effects are in the millions. Seizures are the most common symptom, but depending on the size and location of the cysts they may cause stroke symptoms, dementia, and other severe neurological impairments. In serious cases, this can even lead to the death of the infected person.

Therefore, it is essential that tapeworm infections can be reliably identified before such severe consequences occur, which is what we plan to achieve in our project. Click  here to find out more about our plans.

 

References:

[1] Coral-Almeida M, Gabriël S, Abatih EN, Praet N, Benitez W, et al. (2015). Taenia solium Human Cysticercosis: A Systematic Review of Sero-epidemiological Data from Endemic Zones around the World. PLoS Negl Trop Dis 9(7): e0003919. doi: 10.1371/journal.pntd.0003919

[2] O'Neal SE, Moyano LM, Ayvar V, Rodriguez S, Gavidia C, et al. (2014) Ring-Screening to Control Endemic Transmission of Taenia solium. PLoS Negl Trop Dis 8(9): e3125. doi: 10.1371/journal.pntd.0003125

[3] Nash TE, & Garcia HH (2011). Diagnosis and Treatment of Neurocysticercosis. Nature Reviews. Neurology, 7(10), 584–594. http://doi.org/10.1038/nrneurol.2011.135