The Malacological Society of London

afternoon scientific meeting entitled:

“Are snail-borne diseases still a threat to global health?”

From 2pm on Thursday 28th April 2005, at the Linnean Society of London,
Burlington House, London W1J OBF

Throughout the world there are many control programmes waged against snail-borne diseases; of particular note is schistosomiasis, however, there are also several other diseases of global importance. This meeting hopes to draw together common themes of these fascinating, yet devastating diseases, uniting both their epidemiology and natural history.

Time	Scientific programme	Speakers
2.00 pm	Welcome and introduction	Russell Stothard Natural History Museum
2.10 pm	Clinical features of snail-borne diseases	Peter Chiodini The Hospital for Tropical Diseases
2.40 pm	Overview and global burden of schistosomiasis	Alan Fenwick Imperial College London
3.10 pm	Overview and global burden of food-borne trematodes and search for novel treatment options	Juerg Utzinger & Jennifer Keiser Swiss Tropical Institute
3.40 pm	Tea & viewing a selection of posters
4.10 pm	Recent advances in snail DNA research	David Rollinson Natural History Museum
4.40 pm	Field ecology of snails and schistosomes in Africa	Bertrand Sellin RISEAL, France
5.10 pm	Molecular ecology of snails and schistosomes in Asia	Joanne Webster Imperial College London
5.40 pm	The significance of gastropod diversity upon snail-borne diseases	Thomas Kristensen Danish Bilharziasis Laboratory
6.10 pm	Questions & concluding remarks	Vaughan Southgate Natural History Museum
An evening reception with drinks in The Linnean Society Library, an admission charge of £5

The meeting is held in conjunction with

The Linnean Society of London & The Royal Society of Tropical Medicine and Hygiene.

Organizer: Russell Stothard (r.stothard@nhm.ac.uk)

Abstracts

Clinical features of snail-borne diseases

Peter Chiodini (peter.chiodini@uclh.org)

The infection process of snail-borne trematodes can be broadly divided into oral and(or) trans-dermal routes of larval stages with the resultant adult worms residing within the blood vasculature system or internal body cavities of the human host. These worms like many other helminth infections are unusual in that they do not directly replicate inside their human host but rather produce copious amounts of eggs that, depending upon the species concerned, may be voided to the environment via sputum, urine or faeces. Those eggs that fail to exit the body, becoming trapped in host tissues and organs, ultimately trigger the pathology associated with infection. The methods of diagnosis and clinical signs and symptoms of these snail-borne diseases will be reviewed with particular focus placed upon schistosomiasis.

Overview and global burden of schistosomiasis

Alan Fenwick (a.fenwick@imperial.ac.uk)

The global burden of schistosomiasis is considerable with an estimated 200 million people thought to be infected, with some 600 million people living at risk of infection. In sub-Saharan Africa both urinary and intestinal forms of the disease occur and in certain areas prevalence can be universal amongst school-aged children. The primary focus of control of schistosomiasis is increasing access to praziquantel and as part of a major initiative funded by the Bill & Melinda Gates Foundation, a 30 million USD donation helped to kick-start the drug delivery component within the national control programmes of several sub-Saharan countries. The ongoing progress of this initiative and demonstrable steps towards morbidity reduction will be highlighted with examples from both East and West Africa.

Overview and global burden of food-borne trematodes and search for novel treatment options

Juerg Utzinger & Jennifer Keiser (juerg.utzinger@unibas.ch)

Food-borne trematode infections are (re)emerging diseases of increasing global public health importance, particularly so in Southeast Asia and Western Pacific regions. The changing epidemiology of major food-borne trematodes will be discussed in the context of increasing freshwater aquaculture development. While chemotherapy remains the mainstay of control with inexpensive oral anthelmintics (praziquantel and tricalbendazole) looking to the future very few alternative drugs are undergoing evaluation. Here we present some preliminary results with promising artemisinin derivatives using our Echinostoma caproni-murine model.

Recent advances in snail DNA research

David Rollinson (d.rollinson@nhm.ac.uk)

Molecular approaches to the study of schistosome and snail interactions have provided valuable insights into host-parasite associations and better illuminated the precise epidemiology and transmission of disease. Using examples from East and West Africa, molecular techniques will be shown to assist in the identification and differentiation of intermediate snail hosts and to determine aspects of their population biology useful for disease control interventions. The international initiative concerning the Biomphalaria genome project is rapidly gathering pace and allowing a more precise dissection of the molecular basis of the host-parasite relationship. Studies on gene expression in Biomphalaria will be highlighted using differential display and microarray methods to better determine the dynamics of genes associated with susceptibility and resistance.

Field ecology of snails and schistosomes in Africa

Bertrand Sellin (Bertrand.sellin@wanadoo.fr)

The intermediate snail hosts of schistosomes have successfully colonised many areas of Africa. Their general adaptability and high reproductive rates have allowed Bulinus and Biomphalaria to endure within many varied environments as well as withstand chemical methods of snail control with aquatic molluscicides. Medical malacologists have often become frustrated by the snail’s resilience to control, however, field studies of these molluscs are an essential part of a multidisciplinary approach to control. Better documentation of the snail population dynamics provides important information towards better water resource management and more sustainable actions against schistosomiasis.

Molecular ecology of snails and schistosomes in Asia

Joanne Webster (joanne.webster@imperial.ac.uk)

Schistosomiasis japonicum is one of the most important human parasitic diseases in the Far East, where an estimated two million people are infected. Schistosoma japonicum is unusual in that its intermediate host snail Oncomelania sp. is dioecious and amphibious and that animals such as water buffaloes are considered to be important zoonotic hosts. We present results from the first series of microsatellite investigations into the level of genetic variation among S. japonicum from China and within the Philippines. Samples were analyzed at the level of the country, the province, the village, the intermediate host and the definitive host species. Our results suggest that there may be different strains of S. japonicum circulating.

The significance of gastropod diversity upon snail-borne diseases

Thomas Kristensen (tkkristensen@dblnet.dk)

Owing to their complex lifecycle, the geographic distribution of several snail borne diseases is constrained by the presence of particular species of freshwater gastropods, with schistosomiasis being perhaps the most well known example. As often only a single snail species acts as a local intermediate host, it is important to identify snail populations precisely, differentiating intermediate host species from those that are not. Similarly the presence and diversity of non-host snail species can curtail parasite transmission by blocking the development of larval stages of the parasite. Changes in the environment associated with the diversity and density of freshwater gastropods can ensue associated changes in the parasite fauna sometimes giving rise to disease outbreaks. Based upon examples primarily from Africa, the significance of gastropod diversity will be demonstrated.