VLA & Public Health

Note: This is my interpretation of the lecture given by the VLA @ Liverpool Veterinary School. The logo is their own and is not endorsed in this article in any way. 

The VLA has three roles in public health:

• Surveillance- of endemic disease and new and emerging diseases/situations. 
• Zoonotic disease outbreak investigations.
• Chemical food safety. 

Scientific research is also carried out by the VLA side of AHVLA.

Animal Health side of AHVLA carries out a further three roles in public health:

• Regulation.
• Notifiable Disease Investigations.
• Welfare. 

AHVLA was created on the 1st April 2011. 

The central lab in Weybridge has specialist facilities for:

1. Research- virology, bacteriology & high risk pathogen facilities.
2. Lab Testing- large scale testing & international reference laboratories. 
3. Product and Reagent Manufacture. 

Regional Investigation centres form a national surveillance network. There are diagnostic submissions from private veterinary surgeons from which surveillance information is gained for submission to DEFRA. Collection and recording of disease information. 

Why is There a Need For Surveillance?

• Early detection of new and re-emerging threats in animals. This protects animal & public health, animal welfare, livestock productivity and the wider society. 
• International trade assurance of effectiveness of statutory control plans and assurance of disease freedom.
• Expert advice to inform government, policy and industry.
• Provision of material for research to protect animal & public health. 

You can only detect if a disease is new if there is a familiarity with what is already in the country.

New & Emerging Infections:

• 60% of human pathogens are zoonotic. 
• 75% of emerging infectious diseases have roots in zoonotic pathogens.
• Poorly defined, unclear epidemiology, zoonotic potential unclear e.g. H1N1 pandemic swine influenza 2009.

The Human Animal Infections and Risk Surveillance (HAIRS) Group is a UK based, multi-agency scanning group. It identifies and discusses infections with potential interspecies transfer (zoonosis). It requires hazard identification, risk assessment (risk to public health) & risk management. There is then risk communication to own organsations and other agencies. 

Zoonosis

• Diseases and infections naturally transmitted between animals and humans.
• Viral, bacterial etc.
• Notifiable- anthrax, brucellosis etc.
• Reportable- salmonella and brucella.
• Non-Statutory e.g. swine influenza, orf, erysipelas.

Control issues in zoonotic disease occur when the zoonotic disease is in healthy animals. It is hard to tell the disease is present, expensive to test for, economically insignificant to the livestock farmer, may just be harmless commensals in animals and there is less motivation to control such disease e.g. VTEC E.Coli O157. 

Public health risk of zoonosis commonly occurs via foodborne exposures. People are not significantly exposed to zoonosis in everyday life and there are small risks to leisure pursuits and from pets. There is also an occupational risk e.g. farmer compared to factory worker. This risk changes when people are invited into farms. 

People who visits farms:

• Immunologically naive.
• Vulnerable age groups.
• Unaware.
• No restrictions or legislation requirements.
• Large numbers of visitors.
• Zoonosis through direct/indirect contact.
• Risk management.

The VLA role in these instances is to assist OCT in preventing further human cases. This is through identifying the source of infection through faecal sampling and cultures, statistical approaches, and comparing human and animal isolates for a match via phage typing and molecular work. They can advise on farm practices within a veterinary remit for hygiene, husbandry, farming and disinfection practices to reduce the potential risk of infection. 

VTEC O157

• Verocytotoxigenic E.Coli.
• Causes serious illness in people through the production of verocytotoxin.
• Present in many animal species especially sheep & cattle.
• Present on 40% of farms and 4% of cattle.
• It is a commensal and does not cause disease in animals.
• It is shed in animal faeces either intermittently or 'super shedders.' It causes contamination of the environment, and can persist for weeks/months. 29% of cattle seen positive in VLA investigations.
• A study showed you can decrease levels by having a closed herd, avoiding contact with other cattle, having stable rearing groups, clean bedding, high level of hygiene and manure handling. Dependent on the diet, stress, disinfection and number of high risk species present. 
• Human infection is acquired directly or indirectly from animal faeces. Contaminated food or water, direct/environmental animal contact or person to person spread are all possible infection routes.
• Vets are only involved because of the significant zoonotic risk.
• Preliminary animal cultures performed at AHVLA labs, selected isolates forwarded to centre for infections at colindale and identified via phage typing, and molecular work (VNTR, PFGE).
• Human and animal isolates are indistinguishable and consistent with belonging within the same outbreak. Handwashing hygiene & avoid faecal contact. 

Cryptosporidium 

• C.Parvum is zoonotic.
• Common on farms and causes enteric infection.
• Clinical Disease- diarrhoea in young animals.
• Subclinical in 25% of calves & 40% of lamb pens. 
• Resistant environmental oocysts.
• Peak prevalence between 10 and 20 days of age.
• Medication ineffective.
• Stocking density, clean bedding, and steam clean of calf house as many disinfectants ineffective.
• Diagnosis- speciation to C.Parvum and molecular comparisons.