A guide to help you plan how to protect your flock from salmonella infections and monitor the effectiveness of your programme.
- Why are you keeping chickens?
- Background to Salmonella infections
- Salmonella infections in chickens
- How many chickens do you have laying eggs for human consumption?
- How may your chickens become infected with Salmonellae?
- What measures can be taken to reduce the risk of salmonella in or on the eggs you eat or sell?
- Monitoring for Salmonella
- Further Reading
- Summary Plan
Why are you keeping chickens?
This is the first and most important question. The answer will affect how much effort and money you are prepared to invest in a) controlling the likelihood of your chickens becoming infected and b) the true cost of minimising the risk of salmonella being associated with the egg that is consumed.
If we digress for a moment, in the commercial world poultry are either eaten or lay eggs for human consumption. The parents, grandparents and great grandparents have been selected and monitored to produce chicks that will provide the poultry and eggs that we eat. Millions of pounds are spent annually to ensure that the day old chick that becomes the broiler or layer is free of salmonella.
The breeding stock are housed and managed to minimise the risk of becoming infected There are several different approaches to achieve the same result but they all have to be monitored to meet with company, supermarket and government requirements to ensure that the meat and eggs we eat are free of contamination with salmonella.
Commercially, there are some advantages that you may not want or be able to utilise. The parent flocks will be of one age, there will be many thousands in a flock and they will be reared on one farm and lay eggs on another. The eggs are incubated and hatched in large hatcheries. This means that the farms will be free of chickens for a time and usually the farm will, at most, only be stocked for about a year.
In your situation, there could be poultry of different ages, years rather than months. They may be several breeds and from different suppliers. You may be breeding your own birds. Most likely, they will be housed in extensive systems exposed to many potential sources of salmonella infection.
You might wish to protect your flock by using products that have been developed for the commercial flocks. Unfortunately, many of these products are only available in pack or dose sizes of, 1,000, 2,000 or 5,000 birds. Some will be on general sale and others only available through a veterinary surgeon. If you only have half a dozen birds then buying a thousand doses may seem overly expensive.
In effect you have chosen, perhaps unwittingly, to keep chickens in the most challenging of husbandry environments. The following notes are intended to provide information on the possibilities available to you so that you continue to derive pleasure and enjoyment from keeping poultry.
Background to Salmonella infections
Salmonella infections are caused by the salmonella bacteria of which there are over 2,500 different strains. They can be divided into those that are host adapted of which there are only a few. For example, Salmonella Pullorum (Sp) and Salmonella Gallinarum (Sg)infect birds but not usually mammals whereas the majority are not host adapted infecting birds, mammals, reptiles and fish. These are known as the paratyphoid salmonella. Salmonella have also been found in insects.
Salmonella Pullorum and Salmonella Gallinarum have been eradicated from commercial poultry because Sp is associated with very high mortality, over 50%, in both young chicks and poults whilst Sg is associated with very high mortality in adults.
These two salmonellae like a few others e.g. Salmonella Enteritidis (Se) are capable of being transmitted inside the egg, the chick hatches infected, whereas the majority can be spread through faecal contamination of the egg shell.
The majority of salmonella infections in chickens over 4 weeks of age cause no clinical signs. However, should people pick up any of these salmonella from either eggs or meat then potentially a gastro-enteritis can occur which if it becomes blood borne may be fatal. Se and Salmonella Typhimurium (St) are the two commonest causes of salmonella food poisoning in man.
In an effort to control and reduce the salmonella associated food poisoning incidents, there is a great deal of monitoring by the industry and governments. In addition, there are now significant amounts of legislation at both EU and National level to ensure food safety and reduce the level of salmonella in poultry. We have been very successful in the UK in eradicating Sp and Sg from commercial poultry and Se and St infection occurs only sporadically.
Remember, should your chickens become infected with any salmonella but especially Se or St and subsequently an outbreak of food poisoning is associated with eggs from your flock. Then the flock may have to be slaughtered.
Salmonella infections in chickens
I do not intend to go into detail about Salmonella Pullorum, previously known as Bacillary White Diarrhoea and now as Pullorum disease or Salmonella Gallinarum, known as Fowl typhoid. Suffice to say they can still be found as causes of disease as shown below.
Salmonella Pullorum was isolated from Chickens in 2005, Partridge in 2007 and Pheasants in 2011 and 2012 by the AHVLA in the South of England.
Further information can be found on the PHC Library Website – www.poultryhealthcentre.com
How many chickens do you have laying eggs for human consumption?
Note, not how many chickens do you have, chicks, juveniles, cockerels and hens, but how many do you have laying for human consumption? Of course, some times the eggs will be for hatching and at other times perhaps for eating. Then who eats them? Just your family or do you give them away or sell them to friends and relatives, perhaps supply local butchers and farm markets. It can make a difference as to whether you sell your eggs yourself or through a third party.
Using and selling wholesome fresh eggs would be everyone’s ideal. If challenged how would you demonstrate that you had taken appropriate measures to ensure that the eggs were not contaminated by salmonella? The following is a guide to the legislation that you will need to be familiar with.
- I have less than 50 chickens, all ages and sexes.
- You may be included in The Registration of Establishments (Laying Hens) Regulations 2003*.
“If you have fewer than 50 birds and sell at a public market you do not have to mark your eggs with a producer code. However, you must display your name, address, the best before date and advice on how to keep eggs chilled after purchase. You should also be aware that individual markets still may have their own rules which require the stamping of a producer code on hen eggs.”*
- I have more than 50 chickens or poultry of any kind or mix but less than 350 chickens
- You will need to register with the Great Britain Poultry Register. This is primarily to enable DEFRA identify where susceptible poultry flocks may be in the event of an Avian Influenza outbreak. However, it may also be used if there was a significant salmonella outbreak.
- If you market any eggs through a third party then you may have to be registered with Egg Marketing Inspectorate. The Registration of Establishments (Laying Hens) Regulations 2003*.
“If you have 50 or more hens and sell at a public market you will need to be registered and stamp eggs with your producer code along with the best before date and advice to keep eggs chilled after purchase.”*
- I have more than 350 chickens laying eggs for human consumption.
- Again you will need to register with the Great Britain Poultry register
- You will need to be registered with DEFRA’s Egg Marketing Inspectorate under The Registration of Establishments (Laying Hens) Regulations 2003
- You will also be working to the Eggs and Chicks (England) Regulations 2009.
“These Regulations implement directly applicable European Community marketing standards relating to:
- eggs for hatching and farmyard poultry chicks
- eggs in shell for human consumption
- Salmonella controls under the related National Control Programme (NCP)
These regulations cover most aspects of egg production, marking, transport, grading, packing and their onward marketing, including eggs intended for human consumption as Class A eggs.
The Regulations include requirements for the marketing of eggs for human consumption. It is an offence to market eggs as Class A if they are produced by laying flocks infected with Salmonella or which are of unknown health status (due to failure to test for Salmonella). Such eggs must be marketed as Class B and treated to guarantee that all Salmonella serotypes of significance to public health have been eliminated (i.e. heat treated or pasteurised).”
For more detail go to Business Link – the following address worked October 2012:-
How may your chickens become infected with Salmonellae?
There are two routes:-
- Vertical transmission. A few strains of salmonella are capable of being passed in the egg. These include Sp, Sg (the two avian salmonella), and Se.
- The majority of salmonella, including those above, are mainly excreted with the faeces.
Consequently, your chickens can become infected by inadvertently ingesting feed or potential feed and water that has been contaminated with faeces, ingesting insects and flies that are associated with infected animal droppings, by pecking at infected dead birds or animals, by being handled after an infected bird has been handled, by dust or dirt that has been dropped off boots or clothing. Remember, the 1 gram of faeces that has become trapped in the cleat of your boots may contain hundreds of millions of bacteria. It does not take a lot to introduce infection into the flock.
What measures can be taken to reduce the risk of salmonella in or on the eggs you eat or sell?
You would be forgiven for thinking that there is no hope. This is not true. The following measures are in my view in reverse order of importance.
I keep hearing the phrase “fully vaccinated”. Just what is that supposed to mean? Well as far as UK licensed vaccines are concerned, this includes the following:-
- There are live and dead vaccines available which should be administered according to the manufacturer’s instructions during rear and before point of lay.
- They are not designed for use in hens that are laying eggs. Live vaccines should never be given to hens that are laying eggs
- These vaccines may provide protection against either Se or St or both.
- They will not provide complete protection against infection from all strains of salmonella.
- They will protect the chicken from clinical signs of disease if they are likely to be infected in the first four weeks of life.
- They will minimise the likelihood of spread of Se from the gut to the ovary.
- They will reduce the number of Se and St bacteria excreted in the faeces.
- They offer greatest protection against Se and St as appropriate for the vaccine.
- They will not provide complete protection from gut infections in the event of excessive challenges.
- They are designed to provide immunity for one laying cycle of about 52 weeks.
These vaccines are sold in minimum pack sizes of 1,000 doses. Consequently, you may be best advised to obtain replacement pullets from a rearer that vaccinates. Make sure you have documentation stating the brand of vaccine used, at what age it was given, the batch number and expiry date and who administered it. Alternatively, you must plan your rearing so that you keep replacement pullets separate from the laying flock and that you have a large enough number to make vaccination cost effective.
Competitive Exclusion Products
These products contain the normal bacteria, hundreds of different species that are found in the caecum or blind gut of the chicken. It does not contain salmonella which are not normal inhabitants of the gut. Many years ago it was observed that chickens that had a normal gut flora were more resistant to salmonella than those that did not.
These products contain a mix of many different bacteria which attach to and line the gut. Effectively, these “good” bacteria block the attachment sites for salmonella and also produce products that inhibit salmonella growth.
The advantage of these types of products is that they are effective against all salmonella.
Competitive exclusion products are not the same as probiotics. Probiotics only contain one or a few species of bacteria. In tests, they have been shown to be much less effective in preventing salmonella colonisation of the gut.
I would recommend using Aviguard. This is available from Microbial Developments Ltd (MDL). It comes in various pack sizes to suit the smallest and largest of flocks:
- Beryl’s Friendly Bacteria (6 – 12 hens) – www.berylsbackyard.co.uk· Flightpath (50 + hens) – http://www.microbialdevelopments.com/index.php· Aviguard (2000 + hens) – through your vet, animal health distributor or failing that contact MDL through their website.
You will need to adapt the administration programme to suit your circumstances but as a guide monthly treatments may be appropriate.
A combination of Aviguard treatment and vaccination of pullets in rear is particularly effective. It is not advised to give Aviguard immediately before a live drinking water vaccine because it can interfere with vaccine take.
This is a huge subject and an extremely important aspect of salmonella control. It brings together all aspects of disease control. This includes an appreciation of the sources of infection, how infection can spread, how infection can be recognised and what can be done to prevent or limit the risk of infection.
Vaccination and the use of Aviguard will help protect the individual chicken from infection. The most likely source of host adapted avian salmonella, Sp and Sg, will be other chickens or eggs. Freedom from infection will have to be checked by a combination of having written certification of freedom, purchasing from Poultry Health Scheme accredited flocks and testing the birds or eggs you purchase.
For the rest of the non-host adapted salmonella you have to rely on paper certification of freedom and testing of purchased stock. Then you have to find ways of minimising contact with other sources of infection e.g. wild birds, rodents, pets, cattle, pigs, sheep and people. I sometimes think that people are now a bigger risk to chickens than chickens are to people at least in the commercial poultry industry.
What can you do to keep feed and water clean? As far as the former is concerned provide feed in containers that cannot become contaminated with faeces from birds or rodents. Ensure that feed cannot be contaminated whilst in storage; a plastic dustbin may be suitable. Water needs to be supplied through drinkers that prevent contamination and can be easily cleaned. Using water sanitising agents, such as AviForte, a mixture of organic acids and bioflavanoids, can be beneficial – www.AviForte.co.uk .
Minimise the risk of walking infection from one flock to another with the use of foot dips and hand sanitisers.
Always have clean hand washing and toilet facilities. A changing area where you can take off overalls and footwear before going into your home.
Many of the areas to be covered can be incorporated into your Veterinary Health Plan.
Monitoring for Salmonella
Most salmonella infections are subclinical in chickens i.e. there are no clinical signs. I would recommend that as a minimum you should follow the testing regime of the National Control Programme for Salmonella in Laying Hens.
How often and what type of sample?
|Age||Sample as per the National control Programme|
|Chick||1 chick box liner per 500 chicks up to 10 chick box liners.|
Dead on arrival chicks
|Rearing Pullet||2 pairs of boot swabs or one large faeces sample 2 weeks before being moved to the laying houses.|
|Laying Hen||2 pairs of boot swabs or 2 x 150g faeces samples taken between 22 to 26 weeks of age. These should be repeated every 15 weeks thereafter. If you start at 22 weeks then the next 3 sets of samples will be at 37, 52 and 67 weeks of age or if you start at 26 weeks then it will be 41, 56 and 71 weeks of age.|
This sampling regime works because all other parts of the chain are also carefully monitored: the hatcheries, breeding flocks, rearing pullets and feed mills.
How frequently, you sample will depend on personal circumstances providing you do not have to comply with existing legislation. However, if eggs are used in your own bed and breakfast, cafe or the local Women’s Institute then you might wish to sample more frequently.
Where to get the testing done?
Only use DEFRA accredited laboratories for your testing. The laboratory can supply all the testing kit and instructions for use.
- Poultry Health Services Ltd. Tel. 01480 462816
- Sci-Tech Laboratory Ltd. Tel. 01588 672600
- Wincanton Laboratory Ltd. Tel. 01963 435605
Please note that these guides and recommendations may change. In case of doubt please refer to the original source – DEFRA or Business Link
- Poultry health | Business Link
- A Guide to the National Control Programme for Salmonella in laying flocks
- Code of Practice for the Prevention and Control of Salmonella in Commercial
- Egg Laying Flocks
- Eggs | Business Link
|Pre- Housing||Disinfection||Thorough cleaning of housing and equipment prior to arrival.|
|Pre- Purchase||Certification of Freedom from Salmonella||Could be part of a flock passport.|
|Day Old||Live Salmonella vaccines|
|At times of high risk and large flock size|
Low risk and small to large flocks
|Day Old||Salmonella sampling||Chick Box liners and Dead on Arrival|
|Alternate weeks||AviForte in the drinking water – 0.325ml /litre||Do not mix with live vaccines or any other treatments.|
|3 weeks plus||Live or dead salmonella vaccines used according to manufacturers instruction||To be given to birds in rear. This may be part of a planned programme which will include protection against other infections e.g. Infectious Bronchitis, Newcastle disease, Coccidosis, Infectious Laryngotracheitis, Mycoplasma gallisepticum|
|2 weeks before move to laying quarters||Salmonella sampling||2 pairs boot swabs. These are swabs placed on your boots. You then walk around the housing and any salmonella present in the littered on slatted areas will be collected.|
|Monthly||Aviguard in the drinking water or on food||Particularly in laying flocks where the smaller numbers mean that vaccination is uneconomic.|
|Monthly||Clean and disinfect Feeders and drinkers||More often if necessary|
|From 22 weeks – every 15 weeks||Salmonella sampling||2 pairs boot swabs.|