The Epidemiology of Human-Animal Interactions Part III: Animals as Sentinels of Environmental Hazards

1. The Epidemiology of Human-Animal Interactions Part III:Animals as Sentinels of Environmental Hazards Larry Glickman, VMD, DrPH and Nita Glickman, MS, MPH Purdue University School of Veterinary Medicine

2. The Epidemiology of Human-Animal Interactions: Animals as Sentinels of Environmental Health Hazards • Larry Glickman and • Nita Glickman

3. Instructional Objectives • Describe the risk assessment process • Explain the ‘sentinel’ concept • Provide a rationale for using pet animals in risk assessment • Explain how pet animals can be used as sentinels for environmental causes of human disease

4. Risk Assessment • The process by which scientific evidence is accumulated and used to define the health effects resulting from the exposure of individuals or populations to hazardous chemicals or situations

5. Usual Sources of Data for Risk Assessment • Human epidemiological studies • Laboratory animal toxicological studies

6. Suggested Complementary Approach to Risk Assessment • Naturally occurring diseases in animals • Epidemiological studies of animal populations • In situ studies

7. Sentinel: • ‘Sentinel’ is derived from the French word ‘sentinelle’ meaning watch tower • Sentinels provideearly warning • A sentinel is like a guard dog on patrol

8. “Classical” Example of Animals as Sentinels • Canaries in the coal mines - 1916 • Canaries were taken into the coal mines to warn of noxious gases • Canaries are more sensitive to the effects of odorless coal gas than humans

9. “Modern” Example of Animals as Sentinels • Bioterrorism in Japan in 1995 • A Japanese cult released poisonous gas into the subway system • Japanese policeused canaries asdetectors forpoisonous gasduring a raid on the cult’s premises

10. An Example of a Potential Animal Sentinel That Was Overlooked • Mercury poisoning at Minamata, Japan (1956) & Niigata, Japan (1965) • Strange, erratic behavior of local cats that consumed mercury contaminated fish • This behavior in cats preceded similar changes in humans • Unfortunately, the valueof this animal sentinel was not recognized early enough to prevent significant human morbidity • Supercourse Lecture on Minamata disease

11. One Approach to Environmental Monitoring: Animal Sentinel Systems • Systems in which health information on animals exposed to environmental contaminants are regularly and systematically analyzed to identify potential hazards to other animals or humans.

12. Primary Objectives of Animal Sentinel Systems • Facilitate assessment of human exposures to environmental contaminants • Facilitate assessment of health hazards resulting from such exposures • Indicate relationships between exposure & hazard, eg., dose-response

13. Animal Sentinel Systems Can Be Classified By: • 1) What is being monitored, i.e., exposure or effect • 2) Species of animals used • 3) Environment in question • 4) Natural habitat (observational) vs. purposely placed (experimental orin situ)

14. Selection of an Animal Species: • An ideal animal sentinel species for human health risk assessment is one that is exposed to chemical contaminants in habitats shared with humans or comparable with human habitats and at similar concentrations(e.g., pet animals)

15. Desirable Features of Animal Sentinel Species • Abundance & availability • Example: pet animals

16. Selected Diseases in Household Dogs Associated with Environmental Hazards

17. Example of a Veterinary Sentinel Event: Lead Poisoning *BLC – blood lead concentration

18. Example of a Veterinary Sentinel Event: Lead Poisoning (con’t) • Family dogs can be sensitive sentinels of lead poisoning in children. • Veterinarians diagnosing lead poisoning in dogs have a responsibility to protect public health as well.

19. Example of a Veterinary Sentinel Event: Asbestos & Mesothelioma • Mesothelioma is a highly fatal cancer of humans and dogs caused by asbestos exposure • The latency period between asbestos exposure and mesothelioma may be >25 years in humans • Pet dogs with spontaneous mesothelioma were used to identify environmental exposures that might increase their owner’s risk of asbestos-related diseases

20. Example of a Veterinary Sentinel Event: Asbestos & Mesothelioma (con’t) • Dogs share their owner’s home environment but do not have occupational exposures that could confound interpretation of human epidemiologic studies

21. Summary of a Veterinary Sentinel Event : Asbestos & Mesothelioma Mesothelioma 5 years ALERT Preventive Action Asbestos Exposure Mesothelioma 25+ Years

22. Example of a Veterinary Sentinel Event: Insecticides & Bladder Cancer in Pet Dogs • Pet dogs were used to test for an association between spontaneous bladder cancer and commonly used insecticides for flea & tick control

23. Example of a Veterinary Sentinel Event: Insecticides & Bladder Cancer in Pet Dogs (con’t) • Risk of bladder cancer was significantly increased by topical insecticide use & followed a dose-response pattern

24. Further Implications of a Veterinary Sentinel Event: Insecticides & Bladder Cancer in Pet Dogs • Pet owners and dog groomers are often heavily exposed to topical insecticides during their application • The latent period for bladder cancer is < 10 years in dogs, but probably > 25 years in humans • Question: Is canine bladder cancer a sentinel health event?

25. Summary of a Veterinary Sentinel Event: Insecticides & Bladder Cancer Bladder Cancer 8 years ALERT Insecticide exposure- tick & flea dips, sprays Preventive Action Bladder Cancer 25+ Years

26. Conclusions • Pet animals can serve as valuable sentinels for hazards in the home environment • Diseases of animals only make useful sentinels if they are recognized & reported in a timely manner • Sentinel systems require cooperation between human and veterinary health specialists