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Impact of rodents

Impact of rodents. 4 nights’ catch, 1917 Lascelles, Victoria, Australia. Impact of rodents. Agriculture. Field damage/reduced yield of staple crops. Yield of vegetable crops, marketability. Loss, damage, contamination to stored crops. Health. Zoonosis – lassa fever, plague, leptospirosis.

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Impact of rodents

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  1. Impact of rodents

  2. 4 nights’ catch, 1917 Lascelles, Victoria, Australia

  3. Impact of rodents Agriculture • Field damage/reduced yield of staple crops • Yield of vegetable crops, marketability • Loss, damage, contamination to stored crops • Health • Zoonosis – lassa fever, plague, leptospirosis • Contamination – dysentery (Salmonella etc.) • Property • Buildings, furniture, utensils, roads, wires, clothes, blankets, fishing nets …..

  4. >750 million poor in rice-producing Asia! 70% of the world’s poor live in Asia

  5. Nutrition from rice (selected Asian countries, 1999) 80 70 60 50 Calories 40 Protein 30 20 10 0 Laos India Japan Korea China World Malaysia Thailand Vietnam Myanmar Indonesia Cambodia Philippines Bangladesh Sources: FAO online database (2001); World Development Report (2002); World Bank

  6. Rice field losses to rats

  7. Losses to rats in Bangladesh Field losses 10 – 20 % (up to 100% in some years)Storage losses 5 – 10 % (can be > 200kg per house)Foregone production ?Other crop losses

  8. Rats are the No. 1 pest affecting rice production in many Asian countries Damage crops, stored grain, clothes, houses Loss of production increases crop area Environmental risks from poisons Disease impacts

  9. Rodents and Disease Rodents are vectors and reservoirs for more than 60 different diseases. Hantavirus The Plague Leptospirosis Rat Typhus (rickettsia) Neuro-angiostrongyliasis (rat lungworm) are five of the major rodent-borne diseases that commonly affect human populations in Asia

  10. Why rodents? 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

  11. Morbidity rate of Leptospirosis by province, Northeastern region, Thailand 1996 - 2002 1999 1996 1997 1998 2002 2001 2000 Morbidity rate/100,000 2.41 -15 15.01 - 50 > 50 0- 2.4

  12. W. Tangkanakul et al. 2005. SE Asian J Trop Med Public Health 36,

  13. 7 to 9 times more males affected 71-84% farmers; most 25-54 years Peak incidence in Aug to Nov (rains) Serotypes: australis, sejroe, pyrogenes Higher incidence if villages had pot holes in roads Leptospirosis human epidemiology in Thailand

  14. Information on leptospirosis in Asian countries is extremely limited.   Little is known about: The status of rodent diseases in Asia that affect humans and/or their livestock Which rodents are key reservoir species The persistence of the infective parts of the disease life cycle in rice agro-ecosystems Leptospirosis human epidemiology in Thailand

  15. In 2001-2003 at Mahosot Hospital in Vientiane, of 427 adults with unexplained fever, from serological evidence: 10% leptospirosis 10% murine typhus 15% scrub typhus Leptospirosis & Typhus in Lao PDR

  16. Main risk factor – time spent in flooded paddies

  17. Epidemics of rodent-borne diseases can have a significant impact on a local rural economy. Zoonosis can cause disability at key times and lead to no crop, a late crop, or reduced crop yield. In poorer communities, disability for a month at a key time may lead to no crop, a late crop, or reduced crop yield. Health impacts of rodent diseases Rodent diseases can lead to a debt treadmill!

  18. The Plague Etiologic agent Yersinia pestis - bacillus Bubonic Plague: enlarged, tender lymph nodes, fever, chills and prostration. Septicemic Plague: fever, chills, prostration, abdominal pain, shock and bleeding into skin and other organs Pneumonic Plague: fever, chills, cough and difficulty breathing; rapid shock and death if not treated early Pharyngeal and Meningitic Plague also documented

  19. Importance of Plague in modern times

  20. Stenseth, N.C, Aikimbayev, A., Atshabar, B.B., Begon, M., Belmain, S.R., Bertherat, B., Carniel, E., Gage, K.L., Leirs, H. and Rahalison, L. (in press) Plague: Past, Present and Future. PLoS Medicine.

  21. Surat, Gujarat, India, 1994

  22. Surat Squalid high-density slum conditions and poor sanitation promote transmission Confusion fuelled by poor levels of information in government press statements Media reports unconfirmed/suspected cases, exaggerating death tolls Agricultural exports and cargo embargoed, export loss of more than $420 million Investor confidence plummets, $600 million to $3 billion loss to Indian economy 45,000 people cancelled flights to India International migrant workers stranded Divali [Festival of Lights] cancelled Official death toll was 56 Approx. 700 suspected cases Speculation that it was not plague continues to this day

  23. Economic non-disease costs can be very high Urban outbreaks of plague will happen again Can we learn from the past?

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