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The economic benefit of a disinfection programme in the control of a salmonella outbreak

by 5m Editor
30 October 2004, at 12:00am

By DuPont Animal Health Solutions - This paper outlines the economic benefits of controlling a clinical Salmonella outbreak and shows a cost:benefit ratio of 1:11.

Abstract

Much attention has been paid to the control of Salmonella infections in pig farms for food safety and quality assurance reasons. However clinical Salmonellosis can be a major economic drain on pig units. Tubbs stated that during a Salmonella outbreak Average Daily Gain (ADG) can be reduced by 7-44% and Feed Efficiency (FE) can be reduced by 1-22%.

A Salmonella typhimurium outbreak occurred in weaners on a UK pig farm despite the use of disinfection incorporating a 5% peracetic acid disinfectant. Medication was being used and was only being partially successful. A DuPont Animal Health Solutions terminal disinfection programme was introduced in the weaner accommodation. Medication was terminated at the onset of the programme.

Three weeks after the programme was introduced the pigs had totally recovered infection and Salmonella typhimurium had been eliminated from the water system. A total cost of mortality of pigs and increased feed consumption during the Salmonella outbreak gave a cost of #9608. This work shows that this outbreak was stopped effectively and economically.

Introduction

The 400 sow farm located in East Anglia, England reared pigs to 40 kg. as a part of a traditional 2-site system. Following poor performance in the weaners, with post weaning mortality rising sharply, salmonella was isolated from affected pigs at autopsy . Investigation into the outbreak showed contamination of the unsealed water system with Salmonella typhimurium, and this was the immediate cause of infection to the pigs. In view of this, a comprehensive biosecurity programme was suggested to control the outbreak and reduce environmental challenge to the pigs.

As a follow-up to the water system sampling, a comprehensive survey was carried out of the entire farm. Surface areas of grower kennels and buildings were swabbed with large sterile gauze swabs which had been autoclaved within 250 ml glass jars of Buffered Peptone Water. Samples of faeces were also assayed. The report highlighted an alarming occurrence of Salmonella typhimurium throughout the entire farm.

At this stage, DuPont Animal Health Solutions provided a terminal disinfection programme which was incorporated into the weaning accommodation.

Method

The water system was thoroughly cleaned and sanitized using DAHS Virkon® S at a concentration of 2%.

A terminal disinfection programme of the weaning areas was adopted. The previous disinfection programme was replaced by the DuPont Animal Health Solutions Terminal Disinfection Programme using a heavy duty detergent during the cleaning process followed by a broad spectrum bactericidal and virucidal disinfectant.

In order to prevent recontamination of clean areas, a full biosecurity programme was implemented. A continuous biosecurity programme was instituted using DuPont Animal Health Solutions products. A rodent control programme was also established.

Results

Within 3 weeks of the implementation of the water sanitation programme using DAHS Virkon® S, independent water screening had proved that Salmonella had been eradicated. The clinical morbidity and mortality quickly reduced and performance improved.

The costs of the Salmonella Outbreak

Mortality had increased in the herd from 119 pigs to 213 pigs (an increase of 4.71%). Of this 65 pigs were lost during the quarter due to the Salmonella outbreak. Therefore the outbreak had caused an increase in mortality in the rearing herd of 3.3%.

Initially 43 pigs had been lost but the use of medication had brought this figure down to 20 pigs. This water soluble medication was terminated at the onset of the DAHS Virkon® S programme. Within the following month the mortality of 20 pigs had been reduced to 2. The biosecurity measures therefore reduced mortality by 18 pigs per month in addition to that achieved by medication

Problems caused from the salmonella outbreak would have continued for the quarter and therefore the cost in mortality of the disease outbreak, if not controlled by biosecurity would be 54 pigs. Assuming a then current price of #30 per pig, the Salmonella outbreak had cost #1620 in pig mortality.

The cost of the Salmonella outbreak is not only expressed in the mortality of pigs. For the quarter that the pigs had been affected by the disease growth rates were severely suppressed as shown below:

FLAT DECK (5-14.5 kg) FOLLOW ON (14.5-29.98kg)
Daily Growth rate /grams Av. stay (days) Daily Growth rate /grams Av. stay (days)
3 months to June 95 384.21 23.39 337.01 46.36
Salmonella
outbreak
3 months to Sept 95 309.92 31.98 257.99 58.14
3 months to Dec 95 323.78 27.50 327.65 45.72

In the 3 months when salmonella was diagnosed, daily growth rates had decreased but exit weights from each department were unchanged. Therefore the time the pigs spent in each department had increased. During this time there was an average of 2300 pigs in each department. The weaners had spent an extra 8.5 days in the flat decks. In one quarter, 4.5 tonnes of extra feed was used. (2300 pigs x 8.5 days x 0.23 kg feed/pig/day). At the then current prices of creep feeds of #450/tonne, a cost of # 2025 was incurred for extra feed to produce the same weight of pig.

Pigs spent an extra 12 days in the follow on department. In one quarter, an extra 31.7 tonnes of follow-on feed was used (2300 pigs x 12 days x 1.15 kg feed/pig/day). At the then current prices of grower feeds of #190/tonne, we can extrapolate that a further cost of #6023 had been incurred for feed to produce the same weight of pig.

In total the cost to the farm of the salmonella outbreak was:

Mortality of 54 pigs @ #30 each #1620
tonnage of creep feed of 4.5 tonnes #2025
tonnage of grower feed of 31.7 tonne #6023
Total cost #9668

Neither the effects the outbreak had on pig flow through the farm nor the saving on medication costs are accounted for in this calculation.

Cost benefit analysis

If we factor in the cost of product and services provided by DAHS:

Cost Per Quarter
DAHS Product Cost #401.78
Labour Charge #390.00
TOTAL #791.78
Cost Per Quarter
Salmonella disease outbreak #8048 (increased feed consumption)
#1620 (pig mortality)
TOTAL #9668
Overall Benefit #8876.22

Conclusion

The Salmonella typhimurium outbreak was effectively controlled by the adoption of The DuPont Animal Health Solutions Biosecurity Programme.

The #9668 cost of the salmonella outbreak on this farm would not have been incurred had the disinfection programme been already in place. Controls cost #791.78 giving a Cost: Benefit ratio of 1:11.2.

The resultant healthier stock will have knock-on effects on the reduction of medication and staff management problems, further increasing the economic benefits to the farmer.

Reference

Tubbs R, Deen J. Economics of respiratory and enteric diseases in Proc Am Assoc Swine Pract 1997, Quebec City Quebec, pp 361-364.

Source: DuPont Animal Health Solutions - September 2004