2000, Number 2
Vet Mex 2000; 31 (2)
García OMA, Aboytes TR, Hernández SG, Cantó AGJ, Rodríguez CSD
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ABSTRACTThe present work was designed to evaluate the virulence of Mexican Anaplasma marginale isolates MEX-15-099 (MEX15) and MEX-31-096 (MEX31). Two groups of four steers were inoculated with a dose of 1 × 106 infected erythrocytes of either of the isolates per animal. Experimental animals were monitored for 65 days from the inoculation date. Rectal temperature, packed cell volume (PCV), rickettsemia (PIE) and presence of specific antibodies detected by the ELISA, were registered. MEX15-infected steers reached maximal rickettsemia between 8.8% and 34.7%, while MEX31 steers only maximal values between 0.1% and 16.3%. Only MEX15 steers suffered fever › 40ºC coincidential with the amplification of the rickettsemia. A PCV loss of 68.2 ± 8.9% was registered for the MEX15 steers, which was statistically different (P‹ 0.05) to the 50.1 ± 8.9% loss registered for the MEX31 steers. Except for one MEX31 animal, all other animals developed O.D. readings between 0.355 and 0.829. Only the MEX15-infected animals presented clinical signs of anaplasmosis, whereas only one of the infected with the MEX31 isolate did. Under the conditions of this study, isolate MEX15 appeared more virulent than isolate MEX31.