Determining the feasibility of developing an ovine salmonella vaccine.

Summary

This project was initiated to assess the economic feasibility of developing a Salmonella vaccine for use in Australian sheep, incorporating recent developments in vaccine technology and oral delivery via drinking water. 
The objectives of the project were to: 
1. Complete a literature review of salmonellosis in sheep with particular reference to the livestock export program. 
2. Complete a review of Salmonella vaccines. 
3. Complete a benefit-cost model relating to use of Salmonella vaccination in sheep intended for live export from Australia. 
4. Discuss the findings of the model including consideration of feasibility of developing a commercial vaccine for use in live export sheep and non-economic benefits that may be associated with the application of a Salmonella vaccine in live export sheep. 
This report describes current knowledge concerning salmonellosis in live export sheep and about vaccines that are either available or under development as options for reducing the occurrence and severity of salmonellosis. A DNA adenine methylase live attenuated vaccine has been identified that has genuine potential to offer rapid onset of effective heterologous and homologous immunity following oral administration to sheep in the assembly feedlot. A benefit-cost approach was used to assess losses caused by salmonellosis and the costs and effectiveness of vaccination. The findings of economic modelling indicate that vaccination is economically viable. This conclusion is based on the finding of a positive NPV meaning that the present value of returns over 10 years is greater than the present value of costs over the same time frame. 
The same output can be expressed as a benefit/cost ratio (BCR) which is simply the ratio of the present value of benefits to the present value of costs. The estimated BCR for Salmonella vaccination is 1:1.13 meaning that for every $1.00 invested in the program the expected return would be $1.13. Sensitivity and breakeven analyses were used to identify and characterise influential input parameters. 
Major intangibles associated with the impact of Salmonella vaccination were identified as: 
1) those relating to public perceptions about the livestock export trade and additional animal welfare benefits through reduced morbidity; and 
2) improved performance associated with a reduction in Salmonella exposure and infection. 
The impact of intangibles is considered to add weight to an already positive economic result and strengthen the case in favour of development of a Salmonella vaccination strategy. 
The major beneficiaries of an effective Salmonella program are: 
1. Those industry operators directly involved in the live export trade 
2. The broader Australian sheep industry through the impact of the live sheep trade on general domestic sheep prices and; 
3. The Australian public through the ongoing strength and sustainability of the sheep industry. 
The report supports a recommendation to proceed with research and development of a vaccine against Salmonella that can be delivered orally through drinking water.