DISEASE TRANSMISSION AT THE WILDLIFE-HUMAN INTERFACE

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1 DISEASE TRANSMISSION AT THE WILDLIFE-HUMAN INTERFACE STAN FENWICK REGIONAL TECHNICAL ADVISOR USAID-ONE HEALTH WORKFORCE TUFTS UNIVERSITY-UNIVERSITY OF MINNESOTA

2 Course Outline Ecosystems and human health Ecosystem change and increasing human wildlife contact Wildlife and disease emergence

3 Ecosystems, Ecosystem Health and Conservation Medicine General Concepts

4 Definitions An Ecosystem is a biological community of interacting organisms and their physical environment Ecology is the biological discipline that deals with the interaction of organisms with the environment, and impacts on all aspects of human and animal health Biodiversity is the variability among living organisms from all sources, including terrestrial, marine and other ecosystems and ecological complexes of which they are a part

5 Definitions Ecosystem health is a trans-disciplinary concept that bridges the natural, social and health sciences. It can incorporate human values and perceptions that are important in the management of disease A healthy ecosystem is defined as a socio-ecological unit that is stable and sustainable, maintaining its character in composition, organization and function over time while remaining economically viable and sustaining human communities

6 vet.tufts.edu Conservation medicine strives to understand health in an ecological context (identifying the environmental determinants of health) and uses that understanding to develop preventive or corrective approaches and to maintain the health of all species in a sustainable fashion

7 Central Hypothesis Climate change and vulnerable ecosystems are leading to an increase in emerging and re-emerging diseases Economic, social, political and behavioral factors can influence the environment and affect health

8 SIGNS OF ECOSYSTEM STRESS Appearance of emerging infectious diseases Loss of habitat and biodiversity Increase in generalist opportunist species over specialists e.g. seagulls, sparrows, pigeons, rats and mice versus more specialized animal species Decline in species necessary for plant pollination Decline in natural predators of pest organisms Proliferation of algal blooms along coastlines and waterways

9 Vietnam News, July 2015

10 IMPACT OF BIODIVERSITY ON HEALTH Biodiversity inhibits population explosions of pest species Reduction in biodiversity can lead to closer contact between animal diseases and people an example is Lyme Disease and white-footed mice, increasing due to a decrease in predators and habitat restructuring, efficient maintenance host for ticks

11 Human-Livestock-Wildlife Interface Land Use Change & Human Population Growth Livelihood Impacts & Economic Pressures Increased Contact Between Humans, Livestock, & Wildlife Health Risks to Humans, Livestock, & Wildlife Enhanced Flow of Pathogens

12 ENVIRONMENTAL CHANGES INFLUENCING HUMAN AND WILDLIFE CONTACT Deforestation: removes habitats, predisposes to floods and landslides, habitat fragmentation, changes in vector and reservoir habitats Changes in surface water availability: increased animal and vector ranges

13 Bangkok Post July 2015

14 ENVIRONMENTAL CHANGES INFLUENCING HUMAN AND WILDLIFE CONTACT Overpopulation: expansion into previously uninhabited areas, increased synanthropic animal species (those species ecologically associated with humans) Road building: allows access to wildlife and wilderness areas

15 ENVIRONMENTAL CHANGES INFLUENCING HUMAN AND WILDLIFE CONTACT Climate change Affects food production and population nutrition Can lead to an increase in range of pathogen reservoirs and vectors Contributes to a loss of biodiversity

16 Example of Hantavirus transmission in the US Local enzootic transmission; Sin Nombre reservoir is deer mice; many hantaviruses each has a single rodent host Mild winters and summer rain lead to large increases in rodent numbers; crowding leads to many infections; mice may enter homes; humans inhale virus or come into contact with urine, faeces or nests; cats, dogs, coyotes can be infected but do not transmit CDC

17 ENVIRONMENTAL CHANGES INFLUENCING HUMAN AND WILDLIFE CONTACT Intensive farming practices: result in monocultures, e.g. palm oil plantations impinging on orangutan habitats; impact on vector and reservoir species, e.g. bats and fruit trees

18 ENVIRONMENTAL CHANGES INFLUENCING HUMAN AND WILDLIFE CONTACT Increased temperatures Increase in natural disasters e.g. floods, rats and leptospirosis Flooding in Hanoi Flooding in Manila news.bbc.co.uk

19 OTHER EXAMPLES OF HUMAN AND WILDLIFE CONTACT Anthropogenic change, wildlife trade, tourism bushmeat consumption etc. all result in closer contact between humans and other animal species

20 WILDLIFE AND DISEASE EMERGENCE Emerging diseases are those caused by new agents or by previously known organisms appearing in places or in species in which the disease was previously unknown Includes new animal diseases with an unknown host spectrum, many are zoonotic Wildlife reservoirs represent a more frequent source of new agents WHO/FAO/OIE DEFINITION An emerging zoonosis is a zoonosis that is newly recognised or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range

21 So, emerging infectious diseases can be - A known agent appearing in a new geographic area (e.g. West Nile Virus) A known agent or its close relative occurring in a hitherto unsusceptible species (e.g. Avian influenza) A previously unknown agent detected for the first time (e.g. SARS coronavirus)

22 WHY IS THE RATE of ZOONOTIC DISEASE EMERGENCE INCREASING?..because the number of high-risk interfaces for disease transmission is increasing, especially in developing countries

23 Emerging zoonoses Approximately 60% of human EIDs are zoonoses (868/1415) Approximately 72% originate in wildlife 54.3% caused by bacteria (includes rickettsiae) 25.4% by viruses or prions 10.7% by protozoa 6.3% by fungi 3.3% by helminths

24 IMPORTANCE OF ZOONOSES Public health Economic impact Impact on vulnerable communities Political impact 24

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26 Principles: Disease Ecology Pathogen flow and drivers at the humanlivestock-wildlife interface The arrows indicate direct, indirect or vector-borne pathogen flow. Each box represents a driver Jones et al, 2013

27 The spillover theory and drivers of spillover Spillover theory humans constantly challenged with pathogens from animals, only a small proportion invade and fewer still succeed in causing disease Can also be used for spillover from wildlife to domestic animals, or from humans and domestic animals to wildlife Environmental and climate change Socio-economic, demographic and political drivers Agricultural intensification Livestock keeping Bushmeat hunting

28 Spillover and Disease Emergence C A S E S Human Cases Wild Animal Domestic Animal Animal Amplification TIME N.B. spillback to wildlife can also occur

29 # of shared pathogens # of shared pathogens Is relatedness more important than contact for spillover (or spillback)? Phylogenetic distance from humans Probability of contact with humans

30 Contact rate and spillover risk Henipaviruses Lyssaviruses Flaviviruses Bunyaviruses

31 Many ways (direct and indirect) to be exposed to wildlife diseases. Handling contaminated materials Ingesting infected meat, water Bites or scratches from infected wildlife Inhaling contaminated air, materials Bites from infected insects which have bitten wildlife

32 Viral diversity in the host and disease emergence SIV/HIV Hepatitis viruses.a pool of pathogens

33 Known viruses, corrected for number of species & sampling effort per Order Viruses identified per species RODENTIA PERISSODACTYLA NON-HUMAN PRIMATES LAGOMORPHA CHIROPTERA CARNIVORA ARTIODACTYLA

34 Host diversity exposure and disease emergence

35 Human Metapneumov Respiratory syncitial vir Pandemic Human Viruses Cause Decline of Endangered Great Apes (HMPV, RSV) oto: C. Gomes Köndgen et. al. Current Biolog

36 Pandemic Human Viruses Cause Decline of Endangered Great Apes (HMPV, RSV) Date Community Symptoms Morbidity Mortality Causative pathogen March 1999 March December 2001 March 2004 North Respiratory 32 (all) 8/32 Middle Streptococcus pneumoniae (a), RSV B Chronic respiratory 1/12 1/12 Non detected South Respiratory 41 (all) 9/41 S. pneumoniae (b), Pasteurella multocida, HMPV Haemophilus influenzae August 2005 February 2006 February 2006 South Respiratory 32 (all) 2/32 RSV B South Respiratory 34 (all) 1/34 S. pneumoniae (b) RSV B East Respiratory? 3/? S. pneumoniae (a) RSV B Chi et al. 2007, J. Bact.; Köndgen et al. 2008, Curr. Biol.

37 Zoonotic Agent Families in Wildlife Rhabdoviridae (Rabies, ABL) Paramyxoviridae (Nipah, Hendra) Retroviridae (SIV/HIV) Flaviviridae (West Nile) Togaviridae (WEV/EEV/VEV) Herpesviridae (Herpes B) Filoviridae (Ebola, Marburg) Coronaviridae (SARS) Bunyaviridae (Hantaviruses, RVFV) Orthomyxoviridae (H1N1, H5N1 influenza) Others????????????? J. Epstein copyright

38 Estimated global mortality from selected wildlife zoonoses Log scale Kock 2014

39 EVOLUTION OF INFECTIOUS DISEASES Five stages have been proposed for the evolutionary transformation of an animal pathogen Stage 1: Stage 2: Pathogen only in animals Pathogen moves occasionally from animals to humans ( primary infection ) Stages 3/4: Secondary infections increasing transmission from animal to humans and humans to humans Stage 5: Pathogen exclusive to humans

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41 Action, events or circumstances which may trigger a wildlife disease event Humanwildlife interactions Livestockwildlife interactions Wildlife management actions Climatic events Can result in the introduction of disease or alters the manner in which an existing disease occurs Individual effect Population effect Ecosystem effect

42 Daszak et al., Science; 287 Canine distemper Lyme disease Rabies Taeniasis Host-parasite ecological continuum and disease emergence Few diseases affect only one group Complex relationships set scene for disease emergence Arrows show factors driving disease emergence

43 Emerging Infectious Diseases Some factors contributing to infectious disease emergence Population growth and urbanisation Technology and industry Travel and trade Wars and social disruption Ecological changes due to economic development and land use Microbial adaptation Human vulnerability (drugs, alcohol, immunosuppression) Climate and weather Changing ecosystems Poverty and social inequality Breakdown of public health measures Lack of political will Intent to harm Increases in numbers of unregulated companion animals, synanthropic animals and birds and arthropod vectors Concentrated populations of wild and domestic animals outside cities expose people to zoonotic agents by direct or indirect contact Growing population of drug and alcohol impaired and immuno-suppressed people worldwide are at higher risk of zoonoses

44 SOME RECENTLY EMERGED ZOONOSES Human immunodeficiency virus (HIV) Haemorrhagic fevers (Ebola, Marburg) Henipaviruses Highly Pathogenic Avian Influenza (HPAI) Severe Acute Respiratory Syndrome (SARS/MERS)

45 Bat Diseases Bats have become one of the most significant reservoirs for emerging zoonotic diseases over the past 2 decades Lyssavirus (Australia) Rabies (world wide distribution) Hendra (Australia) Nipah (Malaysia, S. Asia) Menangle (Australia) SARS (Asia & world wide spread) Ebola, Marburg (Africa) Fruit bats a major reservoir Paramyxoviruses (possibly mumps) (worldwide)

46 Family Filoviridae Genus Filovirus EBOLA VIRUS First recognised in 1976 in Sudan and DRC (near Ebola river) Average case fatality rate of ~50% First outbreaks in remote villages of Central Africa near rainforests, recent outbreak has spread to urban areas 5 species Zaire, Bundibugyo, Sudan, Tai Forest (all from Africa) and Reston (non-pathogenic, from Philippines) Pteropid bats thought to be the natural hosts although natural reservoir not confirmed Primates, antelope and porcupines can be infected and die

47 Suspected Ebola transmission in Africa Bat Wild primate Duiker humans handle or eat carcass of dead primate or duiker human infection occurs In 2003, 114/128 people infected with Ebola in Congo/Gabon died and an estimated gorillas!

48 In the recent Ebola outbreak, which started in 2014, there have been around 24,000 cases with 14,000 deaths, over 58% mortality Total cases in the 3 worst affected West African countries, (Sierra Leone, Liberia, Guinea)

49 Control of emerging diseases from wildlife or to wildlife requires a One Health approach

50 Some of the characters in One Health Field Epidemiologists Animal Amplification Behavioral Scientists C A S E S Veterinarians Conservationists Wildlife ecologists Diagnosticians Medical and Public Health Practitioners TIME

51 Many difficulties in dealing with wildlife diseases Hard to sample wildlife; hard to detect diseased animals and carcasses rarely found Few diagnostic tests for wild animals Knowledge of wildlife diseases, transmission and cycles lacking People very protective of wildlife Few interventions used for livestock can be used in wildlife, e.g. culling

52 Although when such interventions are used a lack of ecological understanding can lead to unforeseen problems

53 ..should have involved wildlife ecologists in the planning

54 SMART surveillance Strategic selection of geographic locations for surveillance Strategic selection of species for surveillance

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56 This enables interventions or surveillance to be targeted Human Cases Wild Animals Domestic Animals Animal Amplification C A S E S Wildlife Surveillance and Forecasting Early Detection and Control Opportunities TIME

57 CASES Current Outbreak Detection and Response First Case Detection & Reporting Laboratory Response Confirmation Opportunity for control DAY Adapted from J. Davis, Climate Adaptation Workshop, Nov. 2003

58 CASES However, if we have effective early warning systems in place Surveillance, Observations and Monitoring Information First Case Detection & Reporting Lab Confirmation Response Opportunity for control DAY Adapted from J. Davis, Climate Adaptation Workshop, Nov. 2003

59 What s Next? Recently a number of new avian influenza virus strains have infected humans, the most serious being H7N9 A new coronavirus, MERS, has been identified in the Middle East, closely related to SARS virus and reservoir probably bats; humans most likely infected via contact with camels Most recently an epidemic of Ebola virus has occurred in West Africa, probably linked to initial bush meat consumption (bats, primates)

60 From March 2013 May 2015 there have been 665 confirmed cases of human H7N9 infection, with 229 deaths = 34.4% mortality rate. Most cases in China, few in travellers (HK, Taiwan, Malaysia)

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62 Middle East Respiratory Syndrome (MERS) is a viral respiratory illness that is new to humans. It was first reported in Saudi Arabia in 2012 and has since spread to several other countries, including the United States. Most people infected with MERS-CoV developed severe acute respiratory illness, many of them have died. Camels and bats are believed to be linked to the epidemiology of the disease To June 2015 there have been 1329 cases, with 525 deaths (39% mortality)

63 MERS in South Korea An outbreak of MERS was reported in South Korea in May 2015, in a traveller returning from Saudi Arabia. The outbreak was poorly contained by hospitals Since June 29 th there have been 182 confirmed cases (1 in China) with 32 deaths, 17.6% mortality, considerably lower than in Saudi Arabia (44%)

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65 In Conclusion The occurrence of emerging zoonotic diseases is multifactorial, and is affected by many causal factors, including ecological conditions Overpopulation has stressed the environment and resulted in closer contact between people and wild animals Environmental stability and biodiversity are important for ecological, human and animal health Control of new emerging diseases needs to take into account related environmental factors

66 The Final Word From SEAOHUN (again)!!