Zoonoses – epidemiology and virulence

Some core activities

• Surveillance• Operational

Support• Research• Education• Production of

guidance

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

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

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

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

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?

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Laboratory reports of Cryptosporidium reported to HPS 2000 - 2009

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?

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

Seasonality of Cryptosporidium

in Scotland, 2005-2007

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

2008

PWS in Scotland

Cryptosporidium in wild animals

Auchengarrich wildlife centre outbreak

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

What is the role of drinking water in transmission?

Source 1997-Nov 1999 Dec 1999-2003

Loch Lomond 12.8 6.5

Non-Loch Lomond

27.7 46.9

Rest of Scotland 39.1 66.1

Pollock et al. EID (2008) 14:115-120

1997-2003 Period Incidence (cases/100,000)

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

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

Results – serological – linear modelling

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

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

O157 and the media

• The good– Single cases reported

• The bad– blame culture

• The ugly– The ‘hygiene hypothesis’

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)

Standardised incidence rate

7,840

1,414

1,418

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

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

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

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

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”

Descriptive Epidemiology

Symptomatic Asymptomatic Unknown Total

 Confirmed

 65

 45

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 110

 Probable

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 13

 8

 28

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 4

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 4

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 76

 58

 8

 142

Descriptive Epidemiology

Epidemic curve showing symptomatic cases and dates of onset

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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

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

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

How do you prevent zoonotic transmission?