Infested : living with parasites.

Dr Michael Mosley introduces us to the world of parasites through infecting himself; demonstrating through a ‘pill-cam’ lifecycles of parasites as well as the potential benefits of being infected. Mosley’s journey begins in Nairobi, the capital of Kenya in search of the tapeworm which Mosley describes as nature’s most successful parasite. Mosley, with help from Judy Mwangi, University of Salford, an expert on parasitology, finds some infected beef in order to investigate the cysts and deliberately infect himself. Through the pill-cam, Mosley demonstrates how the parasite has evolved to use our acidic stomach to its advantage; passing through to the intestines. Moreover, Mosley refers to the specialisation of parasites, affirming that a majority can only survive in very rigid conditions; such as in the gut of a human for the tapeworm to a mite that only lives in a moth’s ear. Travelling to the Horniman Museum in London, Joanne Hatton tells the story of the tongue-eating louse (cymthoa exigua) enters through the gills and attaches itself to the tongue of the fish; eventually replacing the tongue. Joanne Hatton asserts how this process outlines how parasites evolved to match the anatomy of their respective hosts. Lice are used as an example of how parasites have adapted and evolved to match human anatomy. Mosley visits a delousing clinic in North London where Alex Coulson infects Mosley with head lice. Mosley visits Dr James Logan, London School of Hygiene and Tropical Medicine where the head louse is studied using a handheld microscope. Also, Mosley and Dr Logan explore the pubic louse which is increasingly hard to find and are similar to a species that infest gorillas; insinuating that at some point in history the louse evolved. Finally, the body louse is investigated, which has even adapted to clothes but behaves very differently from the former two species. The feeling of ‘disgust’ originated to prevent humans from being infected by disease-causing organisms such as parasites; Dr Val Curtis, London School of Hygiene and Tropical Medicine assert that the disgust response is a very important part of our bodies natural defence system. To explore the progress of the tapeworm, Mosley meets with the UK’s leading tapeworm specialist Professor Phillip Craig, University of Salford. Tapeworms are shown to absorb food that has already been digested through villi. Parasites are also shown to be lethal, such as plasmodium which causes malaria. Visiting Professor Mike Blackman at the National Institute for Medical Research, the lethal parasites are shown binding to a red blood cell which then multiply and attach to a new cell; eventually becoming anaemic and blocking blood vessels. Discovering parasites within nature, Professor Joanne Webster, Imperial College London shows how parasites can change the behaviour of rats through toxoplasma which must be digested by a cat in order to complete its cycle. Infected rats are shown to be more attracted to cat smells as well as being much more fearless. Humans can also be infected by toxoplasma and some research has shown that blood samples taken from victims of crashes are twice as likely to be infected; there is, however, no direct evidence. The health aspects of parasites are exhibited through leeches which have been used for thousands of years to treat skin diseases and fevers. Professor Iain Whitaker, Swansea University College of Medicine shows how leeches can be helpful within modern medicine; the ability to remove blood can be very useful within surgery. Visiting the only leech farm in the UK, Carl Peters-Bond describes the growth in demand for medical leeches. Mosley meets with Dr Helena Helmby, London School of Hygiene and Tropical Medicine in order to find out how worms interact with humans’ immune system; showing how the worms immune system has developed alongside ours. However, Dr Helmby argues that the recent surge in allergies over the past century is caused by an increase in hygiene and the decrease of invasions by microorganisms. Mosley discovers how Daniel Heyman, a man with Crohn’s disease, turned to infesting himself with hook worm which lives in the intestines in order to repress his own immune system. Over the space of a year, Daniel Heyman began to feel better and makes a very compelling case for the health benefits of worms. However, Dr Helena Helmby puts forward the argument that scientists have worked for a century in order to eradicate these parasites and finds the idea of self-infliction discomforting. Taking a pill-cam, Professor Mike Rogan of the University of Salford outlines the features of Mosley’s tapeworm which can be viewed throughout his digestive tract. Mosley meets with Dr Mike Brown at the Hospital for Tropical Diseases in order to treat his tapeworm infection. Pills kill the worm which is then digested by the gut.