Prof Tony McMichael

Slide1: 

“Moving targets” – humans and microbes in a globalising world     Tony McMichael National Centre for Epidemiology & Population Health The Australian National University Email: tony.mcmichael@anu.edu.au

Slide2: 

Examples of Emerging and Re-Emerging Infectious Disease: past 10 years A Fauci, NIAID/NIH, 2005

Slide3: 

2 HIV Dengue H Papilloma v Ebola Hanta virus West Nile virus Tobacco Malaria Non- HIV tuberculosis Road accidents 3 5 6 Influenza Polio SARS vCJD Measles HBV + HCV 4 RSV, Rota virus 7 Hospital infection Suicide Major and minor killers: global impact viewed on a ‘Richter’ (logarithmic) scale Weiss & McMichael, 2004 1 Viruses Infant/child ARI & diarrhoeal dis

Outline of Talk: 

Outline of Talk Microbes, infectious diseases: recent trends Infectious diseases as result of major changes in human ecology and environmental – historical transitions; current conditions Examples of infectious disease risks Travel, trade Land use, agriculture Intensive animal husbandry Climate variability, climate change Needed: a more ecological perspective

Receding – then Resurging?: 

Receding – then Resurging? 1950s-60s: Infectious diseases apparently receding in developed countries Antibiotics and vaccines Pesticides to control mosquitoes Improved surveillance and control measures – internationally coordinated Early 1970s: Authorities proclaimed end of infectious disease era. Premature! >30 new or newly-discovered human IDs over past 30 yrs We overlooked the ecological/evolutionary dimensions

Slide6: 

South Korean health workers disinfecting a chicken farm in April, 2005. Though several hundred million birds have died or been killed as a preventive measure in Asia, the human epidemic risk remains unknown. Avian ’flu, H5N1 Mad Cow Disease (BSE)  vCJD Nipah viral encephalitis, Malaysia (1997-99) Previous ’flu epidemics (1918-19, ’57, ’68)

Human-Microbe Transitions over the Millennia: 

Human-Microbe Transitions over the Millennia Pre-historic: hunter-gatherers disperse into distant new environments 1. Local agrarianism/herding: 5-10,000 yrs ago 2. Trans-continental: 1,000-3,000 yrs ago 3. Inter-continental: From c. 1500 AD 4. Today, global: Fourth historical transition Successive increases in SCALE

Slide8: 

Microbial adaptation and change Human susceptibility to infection ageing, HIV, IV drugs, transplantation, transfusion Population growth and density Urbanization, crowding – social and sexual relations Globalization of travel and trade Live animal markets Intensified livestock production Misuse of antibiotics (humans & domestic animals) Changes to ecosystems (deforestation, biodiversity loss) Global climate change Factors in Emerging/Re-emerging Infectious Diseases

Slide9: 

Clearing forests for agriculture Viral haemorrhagic fevers in South America: peasant-farmers Guanarito, Sabia, Kunjin, etc. Eating infected animals New variant Creutzfeldt Jacob disease (from BSE) Cultivation of infected animals Nipah viral encephalitis (pig farms in Malaysia) West Nile virus (goose “fois gras” farms in Ramala, Israel) Collection and trade of wild game HIV (bush meat: primates) Ebola (bush meat?) SARS (civet cat?) Zoonotic Sources: Land-use, Livestock, Wild-life

Slide10: 

1988/9 bans: Sale of nervous tissue and offal for human consumption Eating cattle >30 months old Mammalian products in ruminant feed BUT: no ban on feed for swine or poultry Incidence of BSE in UK, 1987-99 (c.180K cases) Human vCJD (end 2003) -- 125 cases: UK-117, France-6, Ireland-1, Italy-1

Slide11: 

01/97 Farm worker hospitalized with viral encephalitis (VE). 10/97 First death (pig-farm worker) from VE. 02/98 3 farm workers develop VE. 11/98 Health Minister declares it ‘Japanese Encephalitis’  mosquito control and vaccine program. But outbreak spreads. 1-2/99 Pig farmers begin ‘fire sales’ of pigs. Outbreak recedes a little. 02/99 Laboratories receive first samples of infected human tissue. “New” virus? Mass pig culling begins. Villagers flee. 03/99 Virus isolated and identified with reagents used to characterize Hendra virus (a recently-identified horse virus, from Queensland). 04/99 ‘Nipah virus’ discovery announced. Culling continues. 05/99 WHO declares outbreak over (265 cases, 40% fatal). 02/00 Last death. Fruit bats (flying foxes) deemed the likely reservoir. Nipah Viral Encephalitis, in Malaysia

Travel and Trade: examples: 

Travel and Trade: examples Aedes albopictus mosquito eggs in shipments of used tyres  dengue fever Long-distance travel; wild animal trade HIV/AIDS West Nile Virus (New York City, 1999) SARS, 2003

Slide13: 

                 SARS Severe Acute Respiratory Syndrome     A genetic model for the Coronavirus family. (Photo: J Oxford, Retroscreen Virology Ltd)

Slide14: 

Key wildlife trade routes in SE Asia and China

Environmental Changes: 

Environmental Changes Land use, forest clearance Biodiversity losses, extinctions Dams, irrigation Climate change

Density of An. darlingi (malaria vector) in Peruvian Amazon: 

Density of An. darlingi (malaria vector) in Peruvian Amazon Patz et al, 2003 No. of survey sites = 2433 An. Darlingi abundance (log scale)

Slide17: 

Forest fragmentation, hunting (wolves, passenger pigeons) Less diversity of vertebrate predators and viral hosts High Lyme Disease risk Expanding mouse populations Poor inter-species regulation High tick density and high tick infection prevalence  infected deer Many competent reservoir species  less dilution by incompetent reservoir species Lyme Disease: Influences of Habitat Fragmentation & Biodiversity Loss Adapted from: R. Ostfeld Complex life- cycle of tick Woodland suburban housing (NE USA)

Climate Change and Infectious Disease: 

Climate Change and Infectious Disease Some recent changes in ID patterns may reflect the influence of climate change (debate continues) Tick-borne encephalitis (north spread in Sweden) Cholera in Bangladesh (strengthening relationship with El Niño events) Malaria ascent in east African highlands Time-trends in incidence of (reported) food poisoning, esp. Salmonellosis

Slide19: 

NCEPH/CSIRO/BoM/UnivOtago, 2003 Dengue Fever: Estimated geographic region suitable for maintenance of Ae. aegypti, under alternative climate scenarios for 2050 Darwin Katherine Cairns Mackay Rockhampton Townsville Port Headland Broome . . . . . . . . Brisbane . Current risk region for dengue

Baseline 2000 2025 2050 2075 2100: 

Baseline 2000 2025 2050 2075 2100 Source: Kris Ebi MALARIA IN ZIMBABWE, UNDER CLIMATE CHANGE

Baseline 2000 2025 2050 2075 2100: 

Baseline 2000 2025 2050 2075 2100 Source: Kris Ebi

Baseline 2000 2025 2050 2075 2100: 

Baseline 2000 2025 2050 2075 2100 Source: Kris Ebi

Slide23: 

Humans, domestic animals and wildlife are inextricably linked by epidemiology of infectious diseases (IDs). IDs will continue to emerge, re-emerge and spread. Human-induced environmental changes, inter-species contacts, altered social conditions, demography and medical technology affect microbes’ opportunities. Also: New research, technology and collaborative networks will also elucidate role of infection in diverse, mostly chronic, diseases of unknown cause . . . . Summary

Slide24: 

INFECTIOUS CAUSES OF CHRONIC DISEASE: Examples Disease Cervical cancer Chronic hepatitis, liver cancer Lyme disease (arthritis) Whipple’s disease Bladder cancer Stomach cancer Peptic ulcer disease Atherosclerosis (CHD) Diabetes mellitus, type 1 Multiple sclerosis Inflammatory bowel disease Cause Human papilloma virus Hepatitis B and C viruses Borrelia burgdorferi Tropheryma whippelii Schistosoma haematobium Helicobacter pylori Helicobacter pylori Chlamydiae pneumoniae Enteroviruses (esp. Coxsackie) Epstein-Barr v, herpes vv? Mycobacterium avium sub-spp. Paratuberculosis, Yersinia

Conclusion I: Understanding what promotes human-microbe contacts: 

Conclusion I: Understanding what promotes human-microbe contacts Intensified modification/exploitation of natural environments and food production. Disturbance of natural ecosystems and their various internal biotic controls. Poverty, crowding, social disorder, mobility and political instability.

Conclusion II: Microbes as Co-Habitants: 

Conclusion II: Microbes as Co-Habitants Microbes’ interest is in survival and reproduction. They have no malign intent; morally neutral! Their evolution-based drive to survive is as strong as ours (and draws on much longer experience).

Slide27: 

That’s all, folks

Cyclone Sid: Precursor to 1998 Japanese Encephalitis incursion? : 

Cyclone Sid: Precursor to 1998 Japanese Encephalitis incursion? 27 Dec 1997: Tropical Cyclone Sid Air trajectories @ 100 m altitude