In the third of our series of blogs around One Health, Sarah Evans, Lead Scientist for Bacterial Diseases and Food Safety at APHA, talks about the importance of detecting and controlling bacterial diseases across the animal-human interface.
I have had an interest in infectious disease prevention since training as a vet as feline leukaemia virus was a distressing disease in my early career, and led me to think about managing disease in the locality to reduce risk to individual cats. This led to a move to science and specialism in veterinary epidemiology.
I was fortunate to work with some excellent colleagues tackling control and eradication of diseases such as bovine spongiform encephalopathy (BSE). I have focused on the control of zoonoses, infectious diseases that spread between animals and people, in part due to concerns about Salmonella in eggs in the 1990s which was very high profile when I joined the agency.
I now lead a One Health science programme which aims to protect people from zoonoses and antibiotic resistance in food or through contact with animals.
The science of zoonoses control
Our main role as national veterinary surveillance authority is to monitor the situation in animals by testing samples from farms or other premises for infectious bacteria. Zoonotic bacteria rarely cause symptoms in animals so farmers may be unaware of infection. We develop diagnostic and strain typing tests that are cheap and accurate and enable results to be compared to similar tests for bacteria in people.
This is vital so that we can identify and investigate outbreaks of disease (as disease ‘detectives’) to reduce risk of further spread. Science has moved on hugely in this area in recent years with the advent of whole genome sequencing (DNA typing) which gives us an incredibly accurate ‘bar code’ of the bug to help us trace the source of infection and remove it.
Outbreak response is fast paced and interesting work and close working with partners such as Public Health England exemplifies One Health in action.
Using an old analogy, there is little point spending all our effort rescuing drowning people unless we also take steps to stop them falling in the river in the first place! Focusing our attention upstream to reduce the risk of infection by practical controls is another area that benefits from long term government investment in science. Sometimes this is as seemingly simple as using the right disinfectant or sourcing animals from disease free farms but infection may also be spread by wild birds or rodents, as zoonoses can infect a wide range of animals, and by contaminated feed or farm equipment.
Generally, a ‘tool box’ approach to disease control is needed. Farmers and their vets map out herd health risks and develop action plans to minimise risk of infectious disease. APHA supports this by assessing control options such as vaccines, disinfectants and biosecurity, often through trials on farms, as it is important to demonstrate their cost effectiveness, and by providing advice to the farming industry.
Pork can be a source of Salmonella food poisoning and effective measures are needed to reduce infection in pigs. We are currently trialing a vaccine strategy for Salmonella control in pig herds working in close collaboration with the industry. The results so far have been promising, particularly for strains linked to human illness. Full economic analysis will show whether the strategy is cost effective. Reducing infection in pigs will also reduce the risk of spread of Salmonella to other farms, such as neighbouring poultry units.
APHA is an international reference centre with world leading experts in zoonoses and antibiotic resistance in farmed animals. Our scientists provide advice to international bodies, such as the World Organisation for Animal Health (OIE) and the European Food Safety Authority (EFSA), and are involved in global strategies to protect health.
Salmonella is the second most common zoonotic disease in people causing symptoms of diarrhoea and fever (‘food poisoning’). The control of Salmonella in UK poultry flocks has resulted in a dramatic reduction in cases of this illness in people. This success was possible through immense efforts of the industry, researchers, farmers and policy makers working together to develop practical, cost effective and regulated controls. It was estimated that this saved three quarters of a million cases of Salmonella food poisoning and 2000 deaths between 1998 and 2012. Continued vigilance is needed as these adaptable bacteria can mutate (change) over time presenting new challenges to control.
Promoting One Health in action
Most zoonoses do not just spread in one direction and there is a cycle of infection between people, animals and the environment. To protect the health of people and animals we work with others across these boundaries.
The increasing global connectivity allows diseases to spread widely but also offers potential solutions though scientific collaboration and international cooperation to respond to emerging disease threats, such as Ebola virus.
A recent example of scientific collaboration, is the discovery of bacteria with a new type of antibiotic resistance to a ‘last resort’ antibiotic (colistin) for human health, with potential to spread to other bacteria. The resistant bacteria were first reported from a study in China. We were able to use this information to develop a test to search for this new resistance in our bacterial collection and any new samples examined. We quickly found that bacteria with the resistance gene were present in the UK as well as being found in many other countries. Intelligence from our surveillance showed the resistant bacteria were fortunately rare. Farms where the infection was found were investigated and advice was given on antibiotic use. This resulted in the rapid reduction in use of colistin in UK farming and no new cases of this antibiotic resistance have been identified. The effectiveness of this critical antibiotic for hospital use has been preserved by our prompt intervention.
Partnership is all
APHA works with a wide range of partners including vets, livestock keepers and the farming industry, other government agencies and universities to protect the health of animals and people. International partnership is vital to reduce the global threat as zoonoses have little regard to national boundaries. We have a close working relationship with similar veterinary institutes across Europe and elsewhere and harmonise our approaches to allow comparison globally.
A great example is the development of harmonised approaches for the detection and response to disease outbreaks through the use of new genome DNA sequencing technology. The goal is to reduce the impact and cost of disease outbreaks worldwide. The five year EU project is in its concluding stages and has done much to exploit the power of this new technology to transform our understanding of how infectious diseases are spread.
We are also part of a landmark One Health partnership (European Joint Programme) between 38 institutes (veterinary, medical, environment and food) in 19 countries to strengthen action on foodborne zoonoses, antibiotic resistance and emerging threats. This will strengthen inter-sector collaboration to improve disease prevention and control.
Basic hygiene is essential
And finally, if you spotted the media coverage, you may have seen that ‘poor toilet hygiene’ was reported as the likeliest route of transmission for a serious form of blood poisoning in people caused by a multi-drug resistant type of E. coli bacteria.
This genomic epidemiology study, involving APHA scientists, and published in The Lancet Infectious Diseases (Day MJ, Hopkins KL, Wareham DW et al. 2019), found that most bloodstream infections with ESBL-E.coli (a difficult to treat ‘superbug’ also causing urinary tract infections) involve human strain types and animal and food types made little contribution to invasive disease. The use of accurate genome sequencing helped to provide the high quality evidence needed to investigate the uncertain role of animal/food sources of infection. Handwashing and good infection control to prevent spread of human strain types is essential to tackle this serious bloodstream disease in people. Prevention of ESBL-E. coli in animals is important in ensuring veterinary infections remain treatable and reducing the risk of future strains becoming adapted at infecting people.
As mentioned in the accompanying Lancet editorial (Manges AR 2019), the original source of the human strain types is unknown and the analysis is limited by the sheer number of samples needed to examine the wide diversity of ESBL-E.coli strains. The commentator calls for better integrated surveillance across animal and human health and food systems.
This will only be achieved by connecting scientists across sectors and effective partnerships. APHA has an integral role in achieving this crucial One Health goal.
You may be interested in revisiting some of our previously published blogs in this area of work:
- Bringing home the bacon
- Colistin: an antibiotic of last resort
- Antimicrobial resistance: ‘Chance favours the prepared mind’
References
- Michaela J Day, Katie L Hopkins, David W Wareham, Mark A Toleman, Nicola Elviss, Luke Randall, Christopher Teale, Paul Cleary, Camilla Wiuff, Michel Doumith, Matthew J Ellington, Neil Woodford, David M Livermore.
Extended-spectrum β-lactamase-producing Escherichia coli in human-derived and foodchain-derived samples from England, Wales, and Scotland: an epidemiological surveillance and typing study.
The Lancet Infectious Diseases, Volume 19, Issue 12, 2019,Pages 1325-1335, ISSN 1473-3099, https://doi.org/10.1016/S1473-3099(19)30273-7.
- Amee R Manges.
Escherichia coli causing bloodstream and other extraintestinal infections: tracking the next pandemic.
The Lancet Infectious Diseases, Volume 19, Issue 12, 2019, Pages 1269-1270, ISSN 1473-3099, https://doi.org/10.1016/S1473-3099(19)30538-9.
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