Description: Segment 1 Dr Gilliland introduces Professor Nelson, professor of Medical Helminthology at the London School of Hygiene and Tropical Medicine. Prof. Nelson begins the lecture by explaining what schistosomiasis (or bilharziasis) is. He details the three parasites that cause the disease and their distribution around the world. Time start: 00:00:00:00 Time end: 00:04:47:23 Length: 00:04:47:23 Segment 2 Footage of schistosome worms is seen, and Nelson explains the worms' life-cycle, also shown on a chart. Further footage of the parasites are seen, this time at the cercariae (larva) stage. He then discusses how manmade water structures such as irrigation and dams are in many ways responsible for increased schistosomiasis throughout the world. He discusses problematic sites such as the Aswan Dam in Egypt and the Volta Dam in Ghana. He mentions mummies dating back to 2000 BC that were found to contain the parasites' eggs. Time start: 00:04:47:23 Time end: 00:09:56:08 Length: 00:05:08:10 Segment 3 Nelson continues to discuss the history of schistosomiasis, including its prevalence in the First World War. He next talks about control of the disease in Asia. Footage of the spraying of snail infested water in Iran is seen. Time start: 00:09:56:08 Time end: 00:14:43:23 Length: 00:04:47:15 Segment 4 Nelson discusses the unfeasibility of preventing contact with infected water, saying that everyone from field workers to 'sophisticated and educated members of the community' come into contact with it. A photograph of people playing sports in the water is seen. He goes on to talk about immunisation against schistosomiasis, first discussing natural immunity. He describes research using animals that has looked at this area of immunisation. Time start: 00:14:43:23 Time end: 00:19:58:03 Length: 00:05:14:05 Segment 6 Nelson continues to discuss zooprophylaxis (the prevention of disease in man as a result to previous exposure to animal disease). He also talks about how contact with one species of schistosome provides some protection aginst other species. He describes such an experiment on baboons, and goes on to talk about the possibility of deliberate infection with a non-pathogenic parasite to act as immunisation. Illustrations of hybrid schistosomes are seen. Time start: 00:24:22:12 Time end: 00:30:48:00 Length: 00:06:24:13. Segment 7 Footage of an operation on a baboon is seen as Nelson talks. The number of worms that the baboon has developed are counted after they are removed during the operation. Nelson discusses cross-immunity some more, in relation to an experiment where calves were immunised with a human parasite. These calves survived a lethal dose of schistosomes. He goes on to talk about immunity experiments using attenuated irradiated cercariae. Photographs of sheep vaccinated with irrated schistosome larva are seen the sheep survive subsequent infection. Time start: 00:30:48:00 Time end: 00:35:01:18 Length: 00:04:13:18. Segment 8 Nelson discusses the problems of using cercariae in immunisation techniques. A picture of an infected cow is seen, and Nelson concludes the lecture by saying that a vaccine for cattle and sheep will hopefully soon be developed, followed by one for humans. Time start: 00:35:01:18 Time end: 00:37:52:14 Length: 00:02:50:21