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2 Posts tagged with the schistosomiasis tag
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The Parasites and Vectors division in Life Sciences  has been re-designated as the World Health Organisation Collaborating Centre for Identification & Characterization of Schistosome Strains & their Snail Intermediate Hosts until December 2016.  This is in recognition of the importance of their work and expertise on Schistosoma species, the parasitic blood flukes that cause  the debilitating disease schistosomiasis, and is a good example of how the NHM contributes to the solution of global problems of health and wellbeing.

 

The group has had a  long-standing research focus on Schistosoma parasites, initially born from research on the molluscan (snail) intermediate  hosts and host-parasite interactions. Schistosomes have a two-host life cycle  involving an intermediate snail host and a definitive vertebrate host. The  relationship between the schistosomes and the snail is such that precise  identifications of both are required in order to understand the transmission  and the epidemiology of the disease. By researching the factors involved in Schistosoma parasite - snail host infection dynamics, the  team can provide expert advice to countries affected by schistosomiasis.

 

What is schistosomiasis?  A staggering number of people are infected by  schistosomes, over 200 million people worldwide with over 700 million people at  risk of infection. It is a disease of low socio-economic status, affecting the  poorest communities and most neglected, vulnerable people; it is therefore  classified as a neglected tropical disease (NTD). Infants and children are  especially prone to infection and the damage caused by schistosomes can lead to  blood in urine, painful urination, diarrhoea, bloody stool, anaemia, stunted  growth, enlarged liver and spleen, bladder and liver damage. In certain cases  early childhood infections can lead to bladder cancer and liver fibrosis in  adulthood. Over 90% of infected  people live in sub-Saharan Africa, and the NHM team concentrates its research  efforts in areas such as Tanzania, Niger and Senegal, working with teams in  country to help find better solutions to reduce the impact of this debilitating  disease.

 

Research at the NHM - The group at the Museum  is involved in a number of collaborations with research organisations here and  overseas:

 

  • SCORE -  The Schistosomiasis  Consortium for Operational Research and Evaluation (SCORE), funded by the Bill and Melinda Gates  Foundation aims to aid national control programs by defining the best intervention  methods and cost effective strategies for schistosomiasis control in  sub-Saharan Africa. Part of the research undertaken at the NHM monitors the  impact of Praziquantel (the only oral drug effective in treating all forms of schistosomiasis  in sub-Saharan Africa), on parasite populations, in order to monitor for the  potential development of drug resistance.
  • SCAN -  The Museum, with funding from the Wellcome Trust, has set up a rapidly  expanding schistosome repository called SCAN (Schistosomiasis Collection at the  NHM) which preserves and documents schistosome samples collected from Africa in  order to provide material for researchers both within and outside the Museum.  
  • ZEST -  ZEST (Zanzibar  Elimination of Schistosomiasis Transmission) is being led collaboratively by  the Zanzibar Ministry of Health and the Museum’s David Rollinson (funded by  SCORE), director of the NHM -WHO collaborating Centre. This ambitious programme  is attempting to eliminate schistosomiasis – the first time in a sub-Saharan  African country.

 

London Centre for  Neglected Tropical Disease Research - The Museum is also a  founding member of the new London Centre for Neglected Tropical Disease  Research, launched on the 30 January 2013 in collaboration with the London School  of Hygiene and Tropical Medicine and Imperial College. This important new  initiative is a valuable step forward as it brings together world-class skills  and expertise to answer important research questions concerning the biology and  control of neglected tropical diseases in partnership with governments, the  private sector, academic institutions and other key NTD centres.

 

 

Ian Owens
Director of Science

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Intestinal schistosomiasis, caused by Schistosoma mansoni, is endemic to Lake Victoria, with high prevalence of the disease in human lakeshore communities.  Schistosomiasis caused by S. mansoni and a number of other species affects over 200 million people worldwide and is classified by the World Health Organisation as a Neglected Tropical Disease, associated with poverty and limited access to public health services.

 

Schistosoma mansoni is a trematode worm, related to flukes, and is the focus of research by a number of NHM research scientists.  Understanding the life-cycle (part of which takes place in a snail vector, Biomphalaria) and evolution of the parasite is essential to enable effective disease control to be put in place.  Intestinal schistosomiasis causes a range of debilitating chronic health problems, including organ damage, which contribute to a low quality of life for those affected.

 

parasitic-worm_30542_1.jpg

A scanning electron microscope image of male and female Schistosoma mansoni

 

Although research has led to much better understanding of the life-cycle, nonhuman primates have until recently been overlooked as potential hosts of the disease, despite known susceptibility. NHM PhD student Claire Standley is lead author on a new study, with Russell Stothard and Richard Kane (Zoology) and other co-authors, that has looked at transfer of the parasite between chimps and humans.

 

They examined 39 semi-captive wild-born chimpanzees being cared for at Ngamba Island Chimpanzee Sanctuary, Lake Victoria, Uganda, together with 37 staff members for S. mansoni infection. Miracidia (a life stage of the parasite) recovered from faeces were analysed for DNA to investigate cross-over between humans and chimpanzees.The island was also surveyed for Biomphalaria intermediate host snails, which were examined for infection with S. mansoni.

 

Chimpanzees were unequivocally shown to be infected with intestinal schistosomiasis. Miracidia hatched from chimpanzee faeces revealed three S. mansoni DNA profiles (haplotypes) commonly found in humans living throughout Lake Victoria, including staff on Ngamba  Island, as well as two previously undescribed haplotypes. At one site, a snail was observed shedding schistosome cercariae (another life stage of the parasite that is released into water and that enters humans through the skin).

 

The scientists concluded that the potential for transfer of intestinal schistosomiasis between humans and animals on Ngamba  Island is greater than previously thought. In addition, chimpanzees were excreting schistosome eggs that were capable of hatching into viable miracidia.  This suggests that these nonhuman primates may be capable of maintaining a local reservoir of schistosomiasis independently of humans - which in turn means that control strategies focused only on treating the parasite in humans may not be successful: account needs to be taken of possible persistence of schistosomes in animal populations.

 

 

Claire J. Standley, Lawrence Mugisha, Jaco J. Verweij, Moses Adriko, Moses Arinaitwe, Candia Rowell, Aaron Atuhaire, Martha Betson, Emma Hobbs, Christoffer R. van Tulleken, Richard A. Kane, Lisette van Lieshout, Lilly Ajarova, Narcis B. Kabatereine, J. Russell Stothard. Confirmed Infection with Intestinal Schistosomiasis in Semi-Captive Wild-Born Chimpanzees on Ngamba  Island, Uganda.Vector-Borne and Zoonotic Diseases. February 2011, 11(2): 169-176. doi:10.1089/vbz.2010.0156.