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Zoonoses – epidemiology and virulence

Zoonoses – epidemiology and virulence

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Zoonoses – epidemiology and virulence

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  1. Zoonoses – epidemiology and virulence

  2. Some core activities • Surveillance • Operational Support • Research • Education • Production of guidance

  3. What is surveillance? ‘This process includes the forced completion of boring forms (that are difficult to find and really easy to lose) with banal details based on poor definitions that interferes with the effective management of patients and you never get to see the data!’ Courtesy of Dr A MacDonald, Consultant Microbiologist

  4. What is surveillance? ‘the ongoing systematic collection, analysis and interpretation of appropriate data, and the timely dissemination of the resultant information to those who need to know’ adapted from: Langmuir AD. The surveillance of communicable diseases of national importance. New England Journal of Medicine, 1963, vol 268, pp 182-192

  5. What are zoonoses? • Infectious agents transmitted from vertebrate animals to humans • 75% of emerging pathogens are zoonotic e.g. SARS, E. coli O157 • May be affected by man’s management of the environment – FMD, drivers of change • Include Campylobacter, Salmonella, Cryptosporidium, E. coli O157 and Q fever

  6. Cryptosporidium • Protozoan parasite • Profuse diarrhoea, bloating, abdominal pain, nausea • May lead to reactive arthritis • Potentially fatal in immuno-compromised • Confirm by isolation of oocysts in stool • Infection can be asymptomatic

  7. How is Cryptosporidium diagnosed? • Stool selection criteria • Microscopy – stained and concentrated • Identifies genus • Real-time PCR to LIB13 and ssu RNA genes • Identifies species/genotype/strain • Local vs national diagnosis • Do all local labs send stool?

  8. Laboratory reports of Cryptosporidium reported to HPS 2000 - 2009

  9. Epidemiology of Cryptosporidium • C. parvum and C. hominis predominate • C. parvum associated with zoonoses/pws • C. hominis associated with foreign travel/urban • Person-to-person • Cider but not whisky • Genus is resistant to disinfection • Swimming pools • Role of private water supplies • Role of public drinking water?

  10. C. parvum and C. hominis reports in Scotland by age group (2005-2007)

  11. Seasonality of Cryptosporidium in Scotland, 2005-2007

  12. Standardised incidence rate (SIR) for Cryptosporidium sp., 2003-2008

  13. PWS in Scotland

  14. Cryptosporidium in wild animals

  15. Auchengarrich wildlife centre outbreak

  16. Auchengarrich wildlife centre outbreak • 128 confirmed cases • 8.1% attack rate at peak of infection • Relative risk of 13.3 for visiting AWC • C. parvum isolated from 103 human cases • C. parvum isolated from lamb pen drain • Scouring lambs • No hand washing facilities (alcohol rub) • Mainly children affected

  17. What is the role of drinking water in transmission? 1997-2003 Period Incidence (cases/100,000) Pollock et al. EID (2008) 14:115-120

  18. Role of drinking water in ‘immunity’ • Floyd Frost studies • Low-level exposure to oocysts via unfiltered water might result in a higher background level of immunity to Cryptosporidium among Glasgow consumers • Exposure may stimulate a protective effect among people subsequently exposed to Cryptosporidium from other sources • Consequence of introducing filtration to Loch Katrine in 2007 might therefore reduce the level of ‘herd immunity’ to Cryptosporidium in the relevant population

  19. Sero-epidemiology - serological vs risk factors - univariate • Age – 0.35% per year of life • Donors with pets had a lower serological response to Crypto than those without pets • serological responses > for swimmers • serological responses > if on a private water supply • serological response < if drinking bottled water

  20. Results – serological – linear modelling

  21. Conclusions from study • Drinking water in GG contributed a proportion of immunity to the population • Estimated proportion is between 24-30% • Temporal reduction in immunity to 27-kDa • Implications for swimmers • Increase in outbreaks of crypto in swimming pools

  22. E. coli O157 and other VTECs • E. coli O157 (UK and ROI, North USA) • Non-O157 serotypes also important (Australia, Germany) • Usually non-sorbitol fermenting • Reservoir – cattle/livestock/humans • Abdominal cramps, bloody diarrhoea, afebrile • Develops into HUS in 10-15% of cases • Medications either neutral or contra-indicated

  23. O157 and the media • The good • Single cases reported • The bad • blame culture • The ugly • The ‘hygiene hypothesis’

  24. How are the VTECs being transmitted? • 50% of cases unknown transmission • Farm contact • Farm dwellers • Person-person spread • Food as source of infection (Central Scotland outbreak) • Private water supplies • Mannix et al. 2007 – OR, 11.5, p< 0.006 • 1 in 5 PWS in Scotland had faecal contamination (DWQR 2009)

  25. Standardised incidence rate 7,840 1,414 1,418

  26. What about other VTEC serotypes? • Rare • Sorbitol-fermenting E. coli O157 • Nursery outbreak in 2006 • 8 of 18 developed HUS • Source unknown • E. coli O26 • 3 sporadic cases in 2010 (kids <10) • Severe forms of HUS • Acquisition of verotoxin genes

  27. Farm exposure to microbes Children on farms Reference group Ege et al., Exposure to environmental microorganisms and childhood asthma (2011) NEJM vol. 364, pp.701-709

  28. Q fever • Coxiella burnetii – intracellular bacterium • Transmitted primarily by cattle, sheep and goats • Disease ranges from asymptomatic to fatal chronic endocarditis • Listed by CDC as a bio-terrorism agent • Several cases reported to HPS per year

  29. Scotbeef outbreak • Beef and lamb slaughter and meat packing plant • Bridge of Allan, nearest residences over 500m distant • Recent development: strict separation clean/dirty processes • Animals from Scotland and Northern England – ~2000 animals/day • ~250 staff from Scotland & beyond; 1/3 Eastern European - hauliers and farmers among regular visitors

  30. Company hypothesis Company hypothesis - contaminated air flow from lairage blowing over route from boning/packing area to car park; this area not used by workers from “dirty areas”

  31. Symptomatic Asymptomatic Unknown Total Confirmed 65 45 0 110 Probable 7 13 8 28 Possible 4 0 0 4 Total 76 58 8 142 Descriptive Epidemiology

  32. Descriptive Epidemiology

  33. Analytical epidemiology • Multi-variate (attack rate: confirmed only)- preliminary findings • Pass through stores - 3.1 times more likely to be case • Pass through walkway two - 2.6 times more likely to be case

  34. Why are zoonoses increasing? • Better surveillance/lab practices • Ready to eat foods – reduced salt content • Ownership of diverse pets • Ageing population • Proton pump inhibitors • Reluctance to throw out food • Immunologically naïve population • Improved hygiene • Monoblocking • Wii • PlayStation • Internet

  35. Is all dirt bad for us? • Citrobacter LPS confers protection vs pathogens • LPS • Reduces atopic-induced disease e.g. dog ownership confers protection vs eczema • Reduces incidence of lung cancer in certain occupational workers • Boosts anti-inflammatory immunity • Fun • Explicit recognition of trade-offs

  36. How do you prevent zoonotic transmission?