title: Modelling climate change impact on the spatial distribution of fresh water snails hosting trematodes in Zimbabwe.
abstract: BACKGROUND
  Freshwater snails are intermediate hosts for a number of trematodes of which some are of medical and veterinary importance. The trematodes rely on specific species of snails to complete their life cycle; hence the ecology of the snails is a key element in transmission of the parasites. More than 200 million people are infected with schistosomes of which 95% live in sub-Saharan Africa and many more are living in areas where transmission is on-going. Human infection with the Fasciola parasite, usually considered more of veterinary concern, has recently been recognised as a human health problem. Many countries have implemented health programmes to reduce morbidity and prevalence of schistosomiasis, and control programmes to mitigate food-borne fascioliasis. As these programmes are resource demanding, baseline information on disease prevalence and distribution becomes of great importance. Such information can be made available and put into practice through maps depicting spatial distribution of the intermediate snail hosts.
  
  
  METHODS
  A biology driven model for the freshwater snails Bulinus globosus, Biomphalaria pfeifferi and Lymnaea natalensis was used to make predictions of snail habitat suitability by including potential underlying environmental and climatic drivers. The snail observation data originated from a nationwide survey in Zimbabwe and the prediction model was parameterised with a high resolution Regional Climate Model. Georeferenced prevalence data on urinary and intestinal schistosomiasis and fascioliasis was used to calibrate the snail habitat suitability predictions to produce binary maps of snail presence and absence.
  
  
  RESULTS
  Predicted snail habitat suitability across Zimbabwe, as well as the spatial distribution of snails, is reported for three time slices representative for present (1980-1999) and future climate (2046-2065 and 2080-2099).
  
  
  CONCLUSIONS
  It is shown from the current study that snail habitat suitability is highly variable in Zimbabwe, with distinct high- and low- suitability areas and that temperature may be the main driving factor. It is concluded that future climate change in Zimbabwe may cause a reduced spatial distribution of suitable habitat of host snails with a probable exception of Bi. pfeifferi, the intermediate host for intestinal schistosomiasis that may increase around 2055 before declining towards 2100.
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 100, 1870, Frederiksberg C, Denmark. ubpedersen@hotmail.com.
authors.forename: Ulrik B
authors.initials: UB
authors.lastname: Pedersen
authors.affiliation: Danish Meteorological Institute, Copenhagen, Denmark. mas@dmi.dk.
authors.forename: Martin
authors.initials: M
authors.lastname: Stendel
authors.affiliation: Department of Medical Microbiology, University of Zimbabwe, College of Health Sciences, Harare, Zimbabwe. midzinicholas@gmail.com.|National Institute of Health Research, Ministry of Health and Child Care, Causeway, Harare, Zimbabwe. midzinicholas@gmail.com.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Midzi
authors.affiliation: Department of Biochemistry, University of Zimbabwe, Harare, Zimbabwe. mduluza@medic.uz.ac.zw.|School of Laboratory Medicine and Medical Sciences, University of KwaZulu-Natal, KwaZulu-Natal, South Africa. mduluza@medic.uz.ac.zw.
authors.forename: Takafira
authors.initials: T
authors.lastname: Mduluza
authors.affiliation: National Institute of Health Research, Ministry of Health and Child Care, Causeway, Harare, Zimbabwe. whitesoko@yahoo.co.uk.|School of Laboratory Medicine and Medical Sciences, University of KwaZulu-Natal, KwaZulu-Natal, South Africa. whitesoko@yahoo.co.uk.
authors.forename: White
authors.initials: W
authors.lastname: Soko
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 100, 1870, Frederiksberg C, Denmark. asstensgaard@snm.ku.dk.|Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark. asstensgaard@snm.ku.dk.
authors.forename: Anna-Sofie
authors.initials: AS
authors.lastname: Stensgaard
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 100, 1870, Frederiksberg C, Denmark. bjv@sund.ku.dk.
authors.forename: Birgitte J
authors.initials: BJ
authors.lastname: Vennervald
authors.affiliation: School of Life Sciences, University of KwaZulu-Natal, KwaZulu-Natal, South Africa. Mukaratirwa@ukzn.ac.za.
authors.forename: Samson
authors.initials: S
authors.lastname: Mukaratirwa
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Dyrlægevej 100, 1870, Frederiksberg C, Denmark. tkk@sund.ku.dk.|Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark. tkk@sund.ku.dk.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Kristensen
mesh_terms: D063147:Animal Distribution; D000818:Animals; D057231:Climate Change; D017753:Ecosystem; D006790:Host-Parasite Interactions; D008954:Models, Biological; D012908:Snails / Q000469:parasitology* / Q000502:physiology; D014200:Trematoda / Q000502:physiology*; D015030:Zimbabwe; D015047:Zoonoses