The Potential Impact of Climate Change on the Emergence of Vector-borne and Zoonotic Diseases

1. The Potential Impact of Climate Change on the Emergence of Vector-borne and Zoonotic Diseases C. Ben Beard, Ph.D. Associate Director for Vector-borne Diseases CDC- National Center for Zoonotic, Vector-borne, and Enteric Diseases Fort Collins, CO

2. Outline • Introduction to vector-borne and zoonotic diseases • The impact of climate and weather patterns on VBZDs • Case study on the incidence and distribution tick-borne diseases in North America • The role of multiple complicated factors in driving disease emergence • Recommendations for future priorities

3. Definitions Vector-borne Disease: A disease transmitted by an infected arthropod (e.g. mosquito, tick, flea, etc.) Zoonotic Disease: A disease transmitted from animals to humans – directly or indirectly (e.g. Lyme disease, plague, rabies, etc.)

4. Example: Lyme disease Basic Transmission Cycle of a VBZD

5. Rift Valley Usutu Alkhumra Chikungunya TBE Avian Flu West Nile Sin Nombre SARS Ebola (Reston) KFD DHF VEE Lassa JE Guanarito Nipah Ebola Mayaro Chandipura Ross River Oropouche Rocio Barmah Forest Machupo Marburg Chikungunya Hendra Andes O’nyong nhong http://www.avma.org/onehealth/ http://www.nationsonline.org/oneworld/small_continents_map.htm Arthropod-borne Rodent-borne Other (including bat) Global Outbreaks of Vector-Borne and Zoonotic Viruses

6. Recent Outbreaks • Ebola • West Nile fever • E. coli 0157:H7 • Monkeypox • SARS • Chikungunya • Avian Influenza • H1N1 variant influenza

7. Tropical Disease Burden(Diseases transmitted by insects) – Data from the World Health Organization(2004) * Disability Adjusted Life Years - the number of healthy years of life lost due to premature death and disability. Numbers reflect an overall 12% increase in DALYs and 20% mortality increase since 2001.

8. The Impact of Climatic Factors on VBZDs • Climatic factors (e.g., temperature, moisture) affect the distribution and abundance of vectors and vector-borne pathogens • Climatic factors affect disease transmission efficiency (vector competence) • Climatic variables and perturbations can affect disease occurrence patterns

9. Ecological niche modeling of the U.S. Chagas disease vector Triatoma gerstaeckeri Ecological niche characterization of the Chagas disease vector Triatoma brasiliensis 260 240 220 200 180 160 140 120 100 Annual Mean Minimum Temperature Annual Mean Precipitation Climatic factors define the geographic limits of vector and reservoir species… 0 20 40 60 80 100 Beard et al. 2003. EID 9:103-5 Costa et al. 2002. AJTMH 67:516-520

10. Climatic factors play a key role in predicting disease occurrence Plague risk is variable at fine spatial scales • In West Nile region, plague risk was higher above 1,300 m than below • Remotely-sensed covariates included in the model implied that localities that were wetter, with less vegetation growth and more bare soil during January posed an elevated risk • Climatic predictors of spatial and temporal risk have not been identified due to lack of sufficient meteorological data from this plague-endemic region AUC: 81% Sensitivity: 89% PPV: 60% Specificity: 71% NPV: 93% Eisen et al. Am J Trop Med Hyg, ms submitted

11. Ma2 bpx VC = -lnp Climatic factors affect disease transmission efficiency Where… M = density with respect to human population a = feeding frequency b = competence p = daily survival rate x = extrinsic incubation period Vectorial Capacity Equation (average number of new infections generated by a single infected vector) Each of these variables can be affected by temperature, humidity, and/or precipitation

12. °C Increasing Temperature Reduces Blocking of Fleas by Yersinia pestis and Increases Mortality among Infected Fleas Engelthaler et al. 2000 Hinnebusch et al. 1998

13. Climatic perturbations can affect disease occurrence patterns ENSO and Rift Valley Fever

14. Increased soil moisture and available hosts Increased rodent food sources Effects of Increased Precipitation Feb. – March (Major effect) July – Aug (Minor effect) Feb. – March (Minor effect) Cool summer (15 – 18 months after first wet winter) (Major effect) Increased flea survival and reproduction Increased rodent survival and reproduction Widespread epizootics Cool temperatures favor survival of infected fleas High rodent densities favor epizootic spread Increased human plague risks Climatic perturbations can affect disease occurrence patterns Plague Trophic Cascade Model Enscore et al. 2002 AJTMH 66: 186-196

15. Summary • VBZD agents exist in an amplification cycle between vertebrate hosts and vectors • Cycle modulated by external factors that are influenced by weather and climate • Vectoral capacity is also significantly affected by temperature and precipitation • Cyclic weather patterns impact populations of vectors and reservoirs, driving disease epizootics

16. Case Study: The incidence and distribution of TBDs in North America

17. Lyme Disease – History and Emergence • 1st cases of juvenile rheumatoid arthritis in late 1970’s – Lyme, CT • The agent Borrelia burgdorferi was discovered and described in early 1980’s • The most common vector-borne disease in the U.S. Source: The Connecticut Digital Map Library http://www.rootsweb.com/~usgenweb/maps/connecticut/ Young & Delleker sc. -- Philadelphia : Anthony Finley.Scan courtesy of University of Connecticut, UConn Libraries

18. Top 10 Notifiable Diseases in the U.S., 2008 *Confirmed cases (35,198 probable + confirmed)

19. Confirmed cases Probablecases* Reported Cases of Lyme Disease by Year, United States, 1991-2008 *National Surveillance case definition revised in 2008 to include probable cases; details at http://www.cdc.gov/ncphi/disss/nndss/casedef/lyme_disease_2008.htm

20. 1997 2005 Cases per 100,000 population Lyme disease: High Incidence Counties, Northeastern U.S.

21. Tick-borne Diseases in the United States, 2002-2008 *Babesiosis also appears to be increasing in incidence but is not currently nationally reportable

22. Chipman Hill, Middlebury, Vt., 1860s Chipman Hill, 1900s Chipman Hill, 1980s Lyme Disease Emergence and Changing Land Use Patterns (1860s – 1980s) Source: Bald hills: New England before the trees returned. From Thoreau's Country. American Scientist Online Http://www.amercanscientist.org Source: Henry Sheldon Museum - http://henrysheldonmuseum.org

23. Source: http://biology.usgs.gov/luhna/harvardforest.html Lyme Disease – Emergence Source: http://rockpiles.blogspot.com/2006_05_21_archive.html “In Connecticut, the number of deer has increased from about 12 in 1896 to 76,000 today.” [Kirby Stafford Connecticut Agriculture Experiment Station]

24. Tick-borne Disease Emergence – Re-emergence in the U.S. • Reforestation • Overabundant deer populations • Increased numbers of ticks • Expansion of suburbia into wooded areas • Increased exposure opportunities Source: Bald hills: New England before the trees returned. From Thoreau's Country. American Scientist Online Http://www.amercanscientist.org Source: K. Stafford, CT Agricultural Experiment Station

25. Lyme Disease Northward Expansion into Canada

26. Ogden et al. 2008 Int J Hlth Geograph v7p24 Lyme Disease Northward Expansion into Canada • Lyme disease is an emerging infectious disease in Canada • Increases in the numbers of tick vectors in Canada have been connected with two primary factors: • warmer temperatures • dispersion of ticks on hosts, primarily migratory birds Ogden et al. 2009. CMAJ 180:1221-24 Ogden et al. 2006. J Med Entomol 43:600-9

27. Lyme Disease Expansion – Southward!

28. <2% increase >2% increase Average annual increase in Lyme disease, selected U.S. counties, 1992-2006 *Counties reporting average of >5 cases annually

29. Summary • Over the last 10 years, TBDs have increased across the U.S. and in Canada, both in incidence and in distribution • A significant portion of the increase has an ecological basis • A number of other factors are likely to be involved, however, including… • Sociological factors • Individual behaviors • Disease reporting practices • ???

30. Physical Environmental Factors Genetic and Biological Factors Microbe Human Ecological Factors Social, Political, and Economic Factors Factors Influencing Disease Emergence (Institute of Medicine 2003 report – Microbial Threats to Health) • Microbial adaptation and change • Human susceptibility to infection • Climate and weather • Changing ecosystems • Economic development and land use • Human demographics and behavior • Technology and industry • International travel and commerce • Breakdown of public health measures • Poverty and social inequality • War and famine • Lack of political will • Intent to harm Convergence Model for Emerging Diseases

31. A One Health Understanding of Disease Emergence • Human Domain • Human Health Issues • Behavior, Attitudes, Preferences, Culture • Lifestyle, Economics, Technology • Movement, Transport, Trade Human-Environment Interface: “Built Environment” Pollution (Air, Water, Noise, Light, Solid Waste) Urban/ Periurban Development Non-animal Farming Practices (Crop Choice, Irrigation Human-Animal Interface: Companion Animal Ownership Animals as Food, Husbandry Practices Wildlife Management Practices Habitat Encroachment Disease Emergence Re-emergence Persistence • Animal Domain • Non-human Animal Health Issues • Behavior • Geographic Range • Habitat and Feeding Preferences or • Requirements • Environmental Domain • Long-term climatic change • Global Weather Influences (ENSO) • Local/Regional Weather Patterns • Altitude, Temperature, Humidity • Soil and Vegetation Type Animal-Environment Interface: Expansion/ loss of range Invasive Species Effect of Environmental Conditions on Lifespan and Reproduction (especially vectors)

32. Where do we go from here? Important Areas of Focus… • Emphasis on “smart surveillance” in EID “hotspots”, particularly in lower latitude developing countries and in climate-sensitive regions where disease risk is likely to change • Better integration of human and animal health with physical, environmental, and sociologic sciences • Greater investment in interdisciplinary approaches for studying disease emergence and for understanding basic ecology and how weather and climate affect density and distribution of disease vectors and reservoirs • Greater application of modeling to predict risk and to evaluate potential impact of climate change under different scenarios

33. Conclusion • Vector-borne and zoonotic diseases are significantly affected by climate and are at the forefront of concern over global emerging diseases • A One Health paradigm emphasizes the critical relationship between human health, animal health, and the environment in understanding the drivers of disease emergence • Complex weather patterns and global climate change directly impact the ecology of vector-borne and zoonotic diseases • A integrated understanding of climate, ecology, and epidemiology is critical for predicting and averting future epidemics of vector-borne and zoonotic diseases

34. Thank you for your time and attention! Acknowledgements: • Paul Mead • Becky Eisen • Ken Gage • Joe Piesman • Lyle Petersen Required agency disclaimer: The findings and conclusions in this report have not been formally disseminated by the Centers for Disease Control and Prevention and should not be construed to represent any agency determination or policy