Foot and mouth disease (FMD) in adult sheep and goats is frequently mild or unapparent, but can cause high mortality in young animals. The recent outbreak of FMD in the United Kingdom has highlighted the importance of sheep in the epidemiology of the disease, although there have been numerous examples in the past where small ruminants have been responsible for the introduction of FMD into previously disease-free countries. The difficulty in making a clinical diagnosis should encourage the development of more rapid screening tests to assist in future control programmes.
SUMMARYWe have compared detailed physical maps of the genomes of four capripoxvirus isolates, representing four capripoxvirus genome types. The comparisons strongly suggest that the progenitor of one of these isolates arose by genetic recombination between members of two of the other three types.
Five Suffolk sheep, held in a high-security isolation room, were exposed for 2 hours to the aerosol of 3 mature pigs that had been infected with foot-and-mouth disease virus (FMDV), strain O1-BFS. The fleeces of 3 of the sheep were contaminated with FMDV at 2 days post exposure (dpe), while at 5 dpe the fleeces of all 5 sheep were more extensively, and more heavily, contaminated. The persistence of FMDV on contaminated wool was examined in vitro using multiple 0.5 g samples of Merino wool that were each contaminated with one of 3 strains of FMDV in tissue-cultured medium: O1-BFS, O-Morocco (O-MOR 9/91) or an Asia 1 strain (TAI 1/90). Wool samples were held at either 4 degrees C, 18 degrees C or 37 degrees C, and decay curves were established for each virus at each temperature. These curves predicted that O1-BFS, O-MOR 9/91 and TAI 1/90 would fall below detectable levels at 72, 70 and 48 days post contamination (pc), respectively, for wool stored at 4 degrees C; at 11, 12 and 12 days pc, respectively, for wool stored at 18 degrees C; and at 57, 68 and 33 hours pc, respectively, for wool stored at 37 degrees C. For wool contaminated with O1-BFS-infected sheep faeces, urine or blood, or with O1-BFS-infected cattle saliva, decay curves predicted virus to persist for 5 to 11 days pc at 18 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
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