4th Session of the European Commission for the control of Foot and Mouth Disease (EuFMD)

another. Thus, variation within a ty:pe cannot be considered as truo mutation. While it is generally believed that mutations havo taken place in tho field on some rare occasions, the whole question of mutation of tho virus of foot-and-mouth disease has so far not boon scientifically provedg in fact, very littlo is knovm about such mutation.

On the other hand, it is knom1 that strains of tho virus of recognized and proved immunological typos have been kept for many years in laboratories and have maintained their typo specificity, The Swiss exporienco led to tho suggestion that typo C virus had mutated to typo O and that this typo O virus had mutated to typo A, all within a short space of -time. It vms agrood that if this wore so, it must be quite exceptional.

Tho Committee felt that it would be very difficult to plan any ,research which would domonstrato mutation experimentally and that it would be bettor that the different laboratories work on the subject.

If any observations of value emerged from such work, consideration might bo given to a further mooting of this Committee, Dura.tin� of L"J::::1up.ity follo·,--;h-i..� Vo.ccinntio�n nga.in::::t Foct-a.r.J.-lfouth Disease At different sessions of tho Commission, discnnmiuno lravu �o.lr�n place on tho carrying out of experiments to demonstrate the duration of immunity following vaccination against foot-and-mouth disoa.so.

Sovoral plans for such oxperimonts havo b0on drawn up. Thus in 1956 an oxporimont ';,ras discussed. and somo details -,-rnre produced in vvhich groups of cattle in throe difforont European countries would be vac­ cinated with a trivalent culture virus vaccine and challenged at different intervals. It vras hoped that tho three countries concerned ·,-,,rould boar somo of tho costs of tho experiment and that some financial support vvould also be forthcoming from international organizations.

This type of oxporimont Yms suggested bocauso tho Italian Veterinary Authorities have strossed that thore is not yet enough information on tho value of culture. virus vaccine nnd that more experimental vvark should be carried out.

On further discussion at an informal mooting of somo members of the Commission's Standing Technical Committee in Paris in May 1956 ? it was agreed that an experimont using a considerable number of cattle should be undertaken at tho Virus Research Institute, Pirbrightg but, as tho results of such an oxporimont would not be available for some con!lidorablo time, it ,;ms further agreed that smallor-ecale experi­ ment� should also bo carried out at institutes in different countries in order that information could be accumulated, Tho latter oxporimonts would. follow tho design referred to in the above paragraph.

In ardor to como to a final decision on tho design and nature of tho experiments a group of workers on foot-and-mouth disease, roproscm­ ting tho Commission and OIE, mot in Paris on 3-4 December 1956. Tho