Salmonella control in breeding flocks.

Different Salmonella serotypes become dominant in different countries at different times. This is due to the principle of Competitive Exclusion. For example the control of serotypes such as Salmonella gallinarum resulted in the dominance of Salmonella enteritidis in Europe and Salmonella typhimurium in the USA.

A new serotype Salmonella heidelberg is now becoming more significant with a seven-fold increase in 4 years in UK flocks. In raw materials used by the UK feed industry Salmonella heidelberg has only been found in soya during 2000 and 2001. It has not been isolated from poultry feed in 2000 or 2001. This serotype is systemic and colonises animal tissues.

The use of Competitive Exclusion products against such strains has identified that Competitive Exclusion could not avoid salmonella colonisation of the caeca in any trial and liver infections could only be reduced by 55% to 78%. Competitive Exclusion products used in conjunction with a Salmonella typhimurium live vaccine did not improve efficacy but sterilisation of drinking water did tend to improve efficacy.

To help counter this problem SALKIL should be used in flocks at 2kg/Te in all breeder feeds This will protect feed from contamination problems and, due to its unique carrier matrix, will minimise the threat of Salmonella colonisation of the chicken intestine.

If the serology of Salmonella positive flocks does not always occur at the same age and not all houses are affected this indicates that neither the feed nor the water is the source of the infection and a local vector for Salmonella must be suspected. The most common Salmonella vectors are rodents. If individual houses become Salmonella positive, rather than entire breeder units, this generally indicates a rodent problem.

Rodent-vectored Salmonellae can enter the bird through feed contamination, water contamination or direct faecal-oral routes. Again it is therefore essential that feed on breeder units be protected with SALKIL to help prevent colonisation in the intestine of the birds. Drinking water should also be treated with SALKIL LIQUID.

Wild birds may also act as Salmonella vectors and the spread of infection may differ. Rats would normally have defined runs and would only affect individual houses on the farm. Birds tend to be more ubiquitous and the number of houses affected could be higher.

There is increasing evidence in some countries that genetic material (GGP flocks) may be Salmonella carriers. If birds have been vertically infected with a systemic serotype then infection may only manifest itself during stress periods such as hormonal stress, point of lay, vaccination, or changes of anticoccidial drugs. If the problem is systemic the possibility of antibiotics being effective is greatly reduced as some Salmonellae become intracellular in host animals, which makes them highly resistant to antibiotics. In this case SALKIL will help prevent horizontal transmission of Salmonella and will help to contain the infection to birds infected in-ovo.

Slaughter policy is used to eradicate Salmonella enteritidis positives from breeder flocks. It is a slow process and requires a great degree of biosecurity in terms of disinfection, rodent control, insect control and wild bird control. Visitors to farms must be restricted; visitors to breeder units and hatcheries should be excluded.

Vaccination policies have also proved beneficial as a means of breaking a vertically transferred Salmonella problem and (except with live vaccines) these work well with SALKIL in the feed.

The use of SALKIL in breeder feed will not control vertically transmitted or systemic Salmonellae. Neither will antibiotics control systemic Salmonellae. The only options are slaughter policies or vaccination policies in conjunction with SALKIL.

Murray J Hyden, Managing Director November 2003