Emerging Infectious Disease, Zoonoses and the Human-Livestock-Wildlife Health Interface

1. Emerging Infectious Disease, Zoonoses and the Human-Livestock-Wildlife Health Interface A Primer for Conservationists College of African Wildlife Management Mweka, Tanzania July 2008

2. 19-year-old Egyptian Dies of Avian Flu (Bloomberg) Anthrax Claims 20 Cows, Cattle Market Closed (New Indian Express) Two Die in Spain from Human Form of Mad Cow Disease (Reuters)

3. Emerging Infectious Disease • Emerging Infectious Disease • An infectious disease that has newly appeared in a population or is rapidly increasing in incidence or geographic range • On average, 1 newly identified infectious disease every year for each of the last 30 years (WHO)

4. Zoonoses • Zoonotic Disease: • Disease entities readily transmissible between human and animal populations • Avian Influenza • Severe Acute Respiratory Syndrome (SARS) • Monkeypox virus • Rabies virus • Brucellosis • Ebola virus • West Nile virus • Nipah virus • Bovine tuberculosis (mycobacterium bovis)

5. Emerging Infectious Disease • Approximately 75% of recent emerging infectious diseases have been zoonoses Avian Influenza Virus Ebola Virus Anthrax

6. Nature Study • 335 emerging infectious diseases identified between 1940 and 2004 • Outbreaks were positively correlated with growing population densities • US/Europe had highest frequency of reported outbreaks… Why? • 60.3% were zoonoses • 71.8% of these originated in wildlife • Jones, Patel, Levy, et. al. Nature, 2008 Feb. 21; 451 (7181):990-3

7. Nature Study • EID events: 1940 - 2004

8. Nature Study • Regression analysis adjusted for: • Human population density and growth • Rainfall • Latitude • Wildlife host species richness Global Distribution of Relative Risk of an EID Event (a) zoonotic pathogens from wildlife, (b) zoonotic pathogens from non-wildlife, (c) drug-resistant pathogens, (d) vector borne pathogens

9. Human-Livestock-Wildlife Interface • Food Security • Public Health • Conservation

10. Human-Livestock-Wildlife Interface • Global Commerce in Livestock Products • Increased Demand for Animal Protein • Loss of Wildlife Habitat • Ecosystem Degradation • Cleared Land for Agricultural Use • Increased Opportunity for Human-Animal Interaction

11. Human-Livestock-Wildlife Interface • Bush Meat Trade N. Wolfe

12. Human-Livestock-Wildlife Interface • Logging, Agricultural Encroachment, and Wildlife Habitat Loss NGS

13. Human-Livestock-Wildlife Interface • Wet Markets

14. Public Health Challenges in Africa • Poverty/malnutrition • Lack of infrastructure • Inadequate water and sanitation • Difficulty accessing medical care • Weak public health services • +/- post-conflict • High degree of human/animal co-existence

15. Zoonotic DiseaseImpacts in Africa • 70% of continent’s rural poor are linked to livestock production (> 200 million people) • Population is exquisitely vulnerable: • Loss of livelihoods associated with livestock disease/disease control efforts (cull/quarantine) • Threats to human health • Contribute to entrenched cycles of illness, malnutrition and poverty

16. Non-Zoonotic Livestock Disease Impacts • Foot and Mouth Disease • Endemic in Tanzania • Costs: • Loss of livelihoods/poor productivity • Loss of export markets; movement restrictions • Direct threats to wildlife health • Others: Rinderpest, African Swine Fever • Threats to Domestic and International: • Food Security • Biodiversity • Economic Development

17. Threats to Biodiversity Conservation • Why should conservationists be concerned about zoonoses and emerging infectious disease? • Direct threats to wildlife health • Direct threats to human health (loss of conservation capacity) • Threats to food security (increased use of bush meat) • Threats to livelihoods (contributing to unsustainable land use practices) • Threats to ecotourism initiatives

18. ZoonosesCase Studies • Avian Influenza (H5N1) • West Nile Virus • Nipah Virus • Rift Valley Fever

19. Avian Influenza • 20th century pandemics: • 1918 (~50 million deaths globally) • 1957 (~1 million) • 1968 (~750,000) • 1997: currently circulating H5N1 strain

20. Avian Influenza • Influenza A, H5N1 • Extensive list of susceptible hosts • Currently Bird  Bird and Bird  human transmission • No demonstrated, sustained human to human transmission to date

21. Avian Influenza • Pandemic potential: • Rapid viral mutation rates • Recombination event between HPAI and seasonal flu • Pandemic influenza poses significant public health risk • No pre-existing immunity to H5N1 in human population • Isolates have demonstrated some anti-viral resistance • Vaccine has been developed, but may not cover pandemic strain • Difficulty of containment • Projected Pandemic Costs: • 10-180 million deaths worldwide • Economic Impact: 2-3.1 % of global GDP (>2 trillion USD) (World Bank)

22. Vaccination (FAO) Cull (FAO)

23. West Nile • August 1999, New York City • Case clusters of human meningoencephalitis • 59 patients presented with clinical signs of muscle weakness, encephalitis, paralysis • Case fatality rate of 12%

24. West Nile • June, unusual crow die-off observed at Bronx Zoo • July, veterinarians examined birds with neurologic signs • September, tissue samples positive for WN-like virus • Subsequent months: bird die-offs in adjacent states (CT, NJ, NY) • Both human cases and bird-die offs were linked to West Nile via identical WN viral genomic sequences isolated from bird and human cases

25. West Nile • Flavivirus • Initially identified West Nile district of Uganda 1937 • Transmission via infected mosquito • Primary reservoir in birds • Dead end hosts: humans, horses

26. West Nile ERAP/Cornell

27. West Nile • First documented incidence of West Nile virus in the Western Hemisphere • Within 3 years, had become endemic throughout all 48 contiguous states, Canada and Mexico • Role of migrating birds

28. West Nile • National Cumulative 2007 Human Disease Cases: 3623 USGS/CDC

29. The Nipah Story • Nipah virus • Malaysia 1999 • Paramyxovirus • 265 people exposed on pig farms and at slaughterhouses • Case fatality rate of 40%

30. The Nipah Story • Pigs showed mild clinical signs of neurologic and respiratory disease • Human cases presented with fever, headache, signs consistent with encephalitis • 93% of human cases had occupational exposure to infected pigs suggesting transmission was via direct contact with pigs

31. The Nipah Story • Pork production recently had expanded in Malaysia • Land had been cleared and farms established in close proximity to rainforest • Prime bat habitat • Farm on which Nipah outbreak occurred had fruit orchards adjacent to the pens • Increased transmission opportunities between bats and pigs

32. The Nipah Story • Suspected that excreta (saliva/feces/urine) of bats overhanging pens exposed pigs • Pigs were present at such high stocking densities on the farm that they served as amplifiers of the virus • Humans infected from close contact with pigs • Social, environmental factors framed the outbreak • Outbreak cost the Malaysian government > 450 million USD

33. The Nipah Story • Fruit bats subsequently identified as the reservoir of Nipah in Malaysia • Bats are silent carriers of the virus • Bats --> Pigs --> Humans CCM

34. CCM

35. Wildlife Reservoirs • Bats potential or proven reservoirs for: • Rabies virus - Nipah virus • Ebola virus - Rift Valley fever • Lassavirus - West Nile virus • Rodents (hantaviruses, coronaviruses) • Japanese wild boars (hepatitis E virus) • Non-human primates (SFV, SIV)

36. Rift Valley Fever • Virus (Phlebovirus) • First identified in Kenya, 1930 • Domestic livestock (cattle, small ruminants, camels) and humans susceptible • Transmitted by: • Mosquitoes • Direct exposure to infected tissues • Outbreaks typically follow heavy rainfall

37. Rift Valley Fever CDC Countries with endemic disease and substantial outbreaks of RVF Countries known to have some cases, periodic isolation of virus, or serologic evidence of RVF

38. Rift Valley Fever • Livestock Clinical Signs: • Fever • Abortion • Death (lambs/kids/calves) • Human Clinical Signs: • Fever • Headache • Bleeding • Malaise USDA CDC

39. Rift Valley Fever • Prior outbreak: Kenya 1997-1998 • Associated with heavy rains/flooding • ~89,000 people infected (seroprevalence survey) • 478 deaths • Kenya outbreak: November 2006-January 2007 • Followed unusually heavy rains (3x national average) • Human cases: 404 • Deaths: 118 • Case fatality rate: 29% • Greatest risk factor for human infection was interaction with livestock

40. Rift Valley Fever CDC

41. Rift Valley Fever CDC

42. Rift Valley Fever • Control Measures: • Movement restrictions/quarantine • Slaughter ban/meat inspection • Livestock vaccination • Public outreach/education/radio • Impacts: • Loss of livelihoods/income (markets closed) • Nutritional/dietary (slaughter ban/ meat price leading to  bush meat consumption) • Broader Economy (trade restrictions/control costs) • Wildlife health (impacts on wild ruminants unknown) BBC

43. Rift Valley Fever • Proactive Solutions: • Climate forecasting to predict where heavy rains may predispose to RVF outbreak • Rainfall predictions coupled with livestock disease surveillance may provide a functional early warning system • Education of high risk populations • Use of mosquito nets/repellent • Avoiding contact with suspect animals/animal tissues • Thorough cooking of meat/dairy products

44. Rift Valley Fever • Interdisciplinary coordination for surveillance and response NGO/CBO Government/Ministries

45. Tools:Community Based Surveillance • Train community members to detect and report cases using standard diagnostic criteria • Strengths: • Improves diagnostic sensitivity • Allows real-time ongoing monitoring with minimal resources at minimal cost • Fosters community education and awareness • Weaknesses: • First stage in outbreak detection: laboratory or health worker confirmation needed • Requires good communication/chain-of-command

46. Tools:Outbreak Control and Response • Confirmatory Diagnosis • Case Identification • Quarantine and perimeter control • Livestock culls and destruction of contaminated livestock products • Compensation • Disinfection of premises • Vaccination Decisions

47. The Way Forward • Understanding the complex factors that lead to disease emergence • Social (poverty & instability) • Economic (livestock & wildlife trade) • Environmental (ecosystem degradation & climate change) • Improve data collection/analysis/sharing • Empower communities to proactively monitor and rapidly respond • Multi-disciplinary approach

48. Additional Resources • ProMED Mail www.promedmail.org • World Organization for Animal Health (OIE) www.oie.int • Centers for Disease Control and Prevention www.cdc.gov • Google: Predict and Prevent Initiative www.google.org • HealthMap www.healthmap.org/en • Consortium for Conservation Medicine www.conservationmedicine.org