Aids to stockowners / by J. Walker.

  • John Walker
Date:
1930
Catalogue details

Licence: In copyright

Credit: Aids to stockowners / by J. Walker. Source: Wellcome Collection.

    30/198 page 16
    The method can be made use of with the prospect ol conferring immunity in about 75 per cent of recovered red- vvater anaplasmosis cattle other than calves. Immunisation should be considered only as an emergency measure on infected farms where losses are occurring and dipping facilities do not exist. The only object is to save the greatest possible number of cattle under the worst conditions. Immunisation of young calves was found still less satis¬ factory owing to the difficulty of obtaining a reaction to East Coast fever by inoculation consequent on the partial resistance possessed by young calves. In addition, the coexistence of other tick-borne diseases or a recurrence of such was found to be an adverse factor in the immunisation of calves. Inocu¬ lation of cattle susceptible to redwater and anaplasmosis and other tick-borne diseases is not recommended owing to the risk of transmission of these infections by the material (spleen, etc.) used for inoculation. It was hoped that advantage could be taken of the partial resistance possessed by some unweaned calves of immunising them by infecting them by hand with infected ticks; it was found, however, that the immunity in young calves is in some cases at least built up by more than one attack, and that calves which reacted to infestation by hand and survived were not necessarily immune against reinfection. Immunity in East Coast Enver. Careful observations show that the immunity conferred in cattle which reccover from natural infection is, in the majority of cases, complete; but, exceptionally, a beast which has recovered from an original attack again contracts East Coast lever from the bites of infected ticks; in such the reaction is not severe. In calves, the percentage of recovered animals which again contiai t natural infection would appear to be greater in comparison with weaned cattle. In the case of inoculated cattle, as stated above, a percentage of those which react to inoculation and a still larger percentage of those which do not ii act lo inoculation contract East Coast fever when exposed to natural inlection, and some again react on re-exposure In East Coast fever there are thus limitations to immunity in natuie, but the limitations are greater in artificially im¬ munised cattle.
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