By Stephen Lister, veterinarian
For those of you with hair as grey as mine you can probably remember the crisis that afflicted our industry in November 1988 (especially initially for commercial egg layers) when the infamous Edwina Currie announced to the world that “most of the egg production in this country, sadly, is now affected with salmonella”.
In the fall out, Edwina lost her ministerial post at the Department of Health a couple of weeks later, but the egg industry suffered much more with a catastrophic drop in egg consumption and millions of birds were slaughtered in the aftermath.
From that time the extent of livestock contamination across Europe and beyond, predominantly initially with Salmonella Enteritidis, and its relationship to an upsurge in human food poisoning cases with the same strain concentrated the minds of all involved in the poultry industry. It was only when effective monitoring of the status of all levels of the production chain was introduced that everyone was able to truly ‘know their enemy’.
It was a testament to the resilience of our industry that we addressed this head on through a combination of removing contaminated flocks, embracing the philosophy and practical aspects of biosecurity to break the cycle of infection, and coupling this with strategic use of vaccination and ongoing biosecurity to avoid new cases.
In the wake of this initial hysteria there have been National Control Plans (NCP) set up in all the major poultry sectors, combined with voluntary schemes elsewhere, which has enabled the industry and officials to assess those successes, identify any areas for concern and offer Government, retailers and consumers reassurances about the healthy, clean and safe status of our flocks.
The last 30 years has been a bumpy road to ride but it means that the UK poultry industry has had some of the lowest incidence of salmonella contamination in all sectors, easily meeting annual EU targets for all salmonella types in all areas, and especially those most frequently blamed on human food poisoning. That is great news and has been a cornerstone of the continued success of our industry in the marketplace. However, that success could leave us at risk from the worst potential disease of all – complacency!
I remain impressed and reassured that our industry continues to take these responsibilities seriously – but we can only control the things we can control!
In an industry that monitors every site, every flock and every crop of poultry for the presence of salmonella then we have a very sensitive method of detecting any contamination and can quickly respond to this. Through this monitoring we have been able to detect an increase in isolations of so-called exotic strains over the last few years including strains such as S kedougou, S mbandaka, S agona and S agama. The source of these seems to be contamination via feed, wild birds or wild animals. Such exotic strains are seldom of public health significance and do not cause disease in affected flocks. However, they can suggest some “holes” in site biosecurity procedures and can act as pointers to concentrate our minds on further areas to consider in our site risk assessments.
Of more significance has been a slight increase in flocks unexpectedly contaminated with Salmonella Typhimurium over the last year or so, even in high health status flocks. Again, wild animals may be a source but often typing suggests probable horizontal spread from other livestock, especially pigs, but also on occasion cattle and sheep especially on farms where there has been a close association with such livestock.
As a result, in geographical areas where flocks and herds are in close proximity to other livestock or through co-grazing land used by poultry we must be mindful of this further source of infection. Again, these potential sources of contamination can serve as triggers to further review our procedures.
So what more can we do? In enterprises where there may be co-grazing of range areas by sheep or close association with cattle then it would be advisable to test such flocks or herds to confirm that these are not harbouring salmonella that may spill over into monitored poultry flocks.
Where there are pig herds in close proximity, especially if free range herds, then this must be considered a strong potential risk either from direct spread (shared equipment, vehicles or people) or indirect windborne or physical spread through contaminated manure. In situations where physical separation cannot be guaranteed then consideration of vaccination of at-risk poultry must be considered.
Clearly, poultry producers must continue to control what they can control and to treat biosecurity and prevention of bug entry onto premises as the highest priority at all times. However, there is also a need to consider some of these extra risks and there is real potential for proactive cooperation between different enterprises to try and avoid inadvertent spill-over from one to the other.
Producers should dust off their site risk assessments and realise that where wild migrating birds might concentrate our minds about avian influenza risks, we also need to look closer to home for other risks to our business. If your enterprise is existing cheek by jowl with other livestock farms, especially extensive systems such as pigs, then consider them within your risk assessment.
Engage with these other farmers to ensure that their activities are not putting your livelihood at risk by trying to limit contact or spread from contaminated vehicles, manure, wild animals or people. Encourage them to test and identify their weak points to help everyone. It is clearly important for our industry to share our experiences of the last 30 years with other livestock groups to everyone’s mutual benefit.
We both have something to lose but even more to gain from ongoing coordinated action and cooperation.