Pigs and Rift Valley Fever

Abstract

ONE of the earliest papers¹ on Rift Valley fever included pigs in the list of refractory species because Daubney, Hudson and Garnham² had failed to elicit a clinical response in two pigs they had injected. Later, however, Weiss³ directed attention to the circumstantial field evidence that sows had aborted on farms in South Africa where sheep had died. Nevertheless, when Easterday, Murphy and Bennett⁴ injected three young pigs intraperitoneally with doses of 10^2.2 and 10^3.2 mouse LD₅₀ of Rift Valley fever virus there was no clinical response, no viræmia and no development of antibody. Preliminary findings, herein recorded, suggest that the innate resistance of pigs is not absolute, the dose of virus being critical.