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Can human incidence of leptospirosis be reduced through implementing ecologically-based rodent management?

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GRF 2nd One Health Summit 2013: Presentation by Steven Belmain, Natural Resources Institute University of Greenwich United Kingdom …

GRF 2nd One Health Summit 2013: Presentation by Steven Belmain, Natural Resources Institute University of Greenwich United Kingdom

Published in: Lifestyle, Technology

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  • 1. Can human incidence of leptospirosis be reduced through implementing ecologically-based rodent management? Dr Steven Belmain Natural Resources Institute University of Greenwich United Kingdom
  • 2. Rodent-borne diseases affecting people and livestock More than 60 diseases and counting... Bacteria, Rickettsiae Helminths Plague Capillariasis Leptospirosis Echinococcosis Bartonella Trichinellosis Lyme disease Viruses Relapsing fevers Lassa fever Scrub typhus Lujo fever Salmonella, E. coli Hantavirus CriCon HF Protozoa Tick-borne encephalitis Leishmaniasis Argentinian/Bolivian/Junin HF Toxoplasmosis Sarcocystis
  • 3. How do rodents spread disease? Direct contact Spoiling food Pathogens excreted in the environment Transmission through ectoparasites As intermediate hosts Infected rodent meat
  • 4. How is Leptospirosis spread? Direct contact Spoiling food Pathogens excreted in the environment Transmission through ectoparasites As intermediate hosts Infected rodent meat
  • 5. Why are rodents important reservoirs and vectors of human disease? Mammals with common physiology Commensality with long “co-evolution” living in close proximity to humans Generalist feeders exploiting waste and human/livestock food Rodents can pick up and transmit more than 60 different diseases
  • 6. Why are rodents a problem? Neglected research, inadequate capacity Growing problem globally, poor practice Multiple impacts, often severe, poorly quantified Ecological knowledge absent, what do we do? Socio-cultural context, anthropomorphism Unsustainable management with poisons
  • 7. Rodent control can be effective Understand local context and problems Raise awareness about technology and tools Empower communities and service providers Demonstrate good practice and show impact However, impact has never been demonstrated for any rodent-vectored disease !!
  • 8. Reducing vector populations is a well-established and effective method to reduce diseases Mosquitos and malaria Tsetse fly and sleeping sickness, nagana Midges and river blindness, blue tongue Ticks and borrelia, rickettsia Foxes, dogs and rabies Badgers and bovine TB Rats and ????
  • 9. Ecologically-based rodent management, a new paradigm Rodent biology and ecology Understand rat species behaviour, breeding rates, habitat utilisation, population dynamics Damage caused Holistic assessment – damage to agriculture, health, personal possessions and property Knowledge, Attitudes and Practice Talk to the people with the rat problem to understand what they know and what they do to control rats
  • 10. A rat is a rat is a rat ?
  • 11. One pregnant female rat in an Asian rice field can lead to 120 rats in 120 days Breeding begins prior to max tillering 45-50 d after sowing (DAS) 1 adult female 1st litter born 12 young 68-72 DAS 12 young 2nd litter born 12 young 90-95 DAS 3rd litter born 12 young 112-117 DAS 12 young 12 young Breeding usually ends, but if another rice crop is soon planted, 1st litter breeds (6 females) 36 rats 84 young 120 rats!!
  • 12. Population dynamics of rodents Rodent breeding influenced by rainfall & food production Food availability drives population density Population size Exponential: Extreme weather, unseasonal rainfall Constant: Urban, continuous food availability Seasonal: Cyclic agricultural production Time
  • 13. Rice field losses to rats Region and Rice population produced (tonne) Indonesia 50,000,000 210 million Loss to Rice eaten rodents (kg/year) (%) 17% 249 People fed per year if no rat losses 33 million (52% calories) Vietnam 80 million 31,000,000 30% 280 8 million (67% calories) Asia 3.6 billion 540,000,000 5% 150 180 million (32% calories) 10% 360 million
  • 14. What do people actually do to control rodents? Often nothing Previous uncoordinated individual actions fail Failure breeds apathy and acceptance Cheap, often illegal, acute poisons Fail due to neophobia, used when populations are already high, over too short a time and/or too small an area Other mostly uncoordinated activities such as electrocution, trapping, flooding burrows, hunting, bounty campaigns
  • 15. What people do not do when controlling rodents Work together to coordinate over appropriate scale Implement control when populations are low Use anti-coagulant poisons (due to cost and perceived low efficacy) Improve sanitation Reduce harbourage, i.e. nesting sites Reduce carrying capacity of environment Increase proofing of houses / food stores
  • 16. What can we do to improve rodent management? Community training programmes to increase knowledge and separate fact from fiction Intensive community-based rodent trapping Provide knowledge about rodent behaviour, how poisons work, population dynamics Access to tools to assess impact, surveillance and monitoring Access to ‘new’ technology to sustainably reduce rodent populations and their damage
  • 17. 50 Comparison of community intensive trapping vs. limited monitoring trapping in Swaziland 40 Intensive trapping Non-intervention monitoring 30 % trap success 20 Jun-09 May-… Apr-09 Mar-… Feb-09 Jan-09 Dec-08 Nov-08 Oct-08 Sep-08 Aug-08 Jul-08 Jun-08 Apr-08 0 May-… 10
  • 18. Motivation to control rats: Leptospirosis is not the only rodent problem for households Agriculture Field damage/reduced yield of staple crops Yield of vegetable crops, marketability Loss, damage, contamination to stored crops Loss of production increases crop area Health Zoonosis – Lassa fever, plague, leptospirosis Contamination – dysentery (Salmonella etc.) Environmental / health risks from poisons Property Buildings, furniture, utensils, road s, wires, clothes, blankets
  • 19. Can good quality rodent control reduce the incidence of diseases like leptospirosis? Carry out a case-control (intervention vs. nonintervention) trial that Reduces rodent populations Reduces rodent density Reduces rodent-human proximity Does the intervention Reduce prevalence of leptospires? Reduce number of human cases?
  • 20. Ecologically-based rodent Can EBRM work to reduce the management has been shown to burden of diseases such as be cost-beneficial in agricultural Leptospirosis? situations across the Tropics.
  • 21. Thank You For examples about implementing ecologically-based rodent management, go to In Africa: www.nri.org/ecorat In Asia: www.nri.org/bandicoot Dr Steven Belmain Natural Resources Institute s.r.belmain@gre.ac.uk