Subclinical Infections with Coccidia in Cattle and Their Transmission to Susceptible Calves

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Abstract
Experimental evidence is presented that the type of coccidiosis which occurs during the fall and winter in beef calves in the northern range states has its origin in some condition other than exposure of the host to large numbers of infective oocysts. In 5 newly weaned beef calves studied during fall and winter, the causative agent, Eimeria zurnii, ranked 4th in percentage of total oocyst production and in percentage incidence. E. bovis, E. canadensis and E. ellipsoidalis comprised 78% all oocysts produced. In 2 experiments the transmission of coccidial infections was studied by observing oocyst production in young, coccidia-free dairy calves which were placed in the same corral with weaned beef calves. In one experiment relatively large numbers of E. zurnii oocysts were produced by the beef calves, but no infection was detected in the younger calves. In the other experiment 2 dairy calves remained nearly coccidia-free for a period of 79 days after being placed in contact with the older, beef calves.