308 VETERINARY HYGIENE 



exposure of healthy pigs, which have received serum, to contact 

 with affected pigs. Next in order of safety is feeding such serum- 

 ised pigs with virus, but unfortunately this requires rather a large 

 amount of virulent blood. Inoculation of the virus subcutaneously 

 is still more risky. 



Some vaccinated pigs, although not showing serious symptoms, 

 may nevertheless be found on subsequent slaughter to have had con- 

 siderable intestinal lesions. Only sound pigs should be vaccinated, 

 and during the process they should be protected from outside influ- 

 ences which are likely to have the effect of lowering their vitality. 

 In conclusion, it appears to be desirable to endeavour to find some 

 method of producing active immunity which is not attended with 

 the dangers and disadvantages met with under the present pro- 

 cedure. At any rate, it seems that the simultaneous use of serum 

 and virus should be restricted to centres where outbreaks are fre- 

 quently occurring and where losses from the disease are very high. 

 The results of the use of serum over a period of 12 months (Sept. 

 1915 to Sept. 1916) are discussed by the Chief Veterinary Officer, 

 Board of Agriculture, in his annual report for 1916, from which 

 we have quoted verbatim. Serum treatment was applied in 2100 

 outbreaks : " Of the 77,900 pigs included in the outbreaks treated 

 with serum the total death-rate from swine fever, which included 

 a large number of deaths in pigs which for various reasons were 

 not treated, amounted to 34-6 per cent. The number slaughtered 

 for food during the outbreaks amounted to 25-8 per cent. The 

 number freed at the end of the outbreaks amounted to 38-6 per 

 cent., which included a large proportion of the breeding stock, 

 most of the stores having been slaughtered in 'accordance with the 

 object for which they were intended. Deaths from other causes 

 than swine fever are omitted. 



" During the same period 38,229 pigs were involved in out- 

 breaks on premises upon which serum treatment was not adopted. 

 The total death-rate amounted approximately to 52 per cent. The 

 number slaughtered for food during the outbreaks, often at an 

 early stage, to save their commercial lives amounted approximately 

 to 33-2 per cent. The number freed at the end of the outbreaks 

 amounted to only 14-8 per cent. In both cases the death-rate is 

 calculated in relation to the total number involved. 



" The claim for serum treatment is that it saves pig life on in- 

 fected premises, and it would appear from the above figures that, 

 viewed from the death-rate alone and under the conditions obtain- 

 ing in practice, without taking into account special benefits, such 

 as conservation of breeding stock and business, there was a benefit 



