STUDIES ON THE PATHOGENICITY OF BABESIA-BOVIS IN WATER-BUFFALOS AFTERCRYOPRESERVATION AND RESUSCITATION

Packed erythrocytes infected with Babesia bovis were mixed with an equ al volume of 16% dimethyl sulphoxide (DMSO) in Alsever's solution and dispensed into 1.5 or 5 ml cryotubes. The vials were kept in liquid ni trogen (-196 degrees C) for 26, 78, 142 or 149 days. The samples were removed from the liquid nitrogen container and rapidly thawed in a 40 degrees C water bath. The thawed blood successfully infected splenecto mised buffalo calves by injection via subcutaneous or intravenous or v ia intravenous and subcutaneous routes. The parasites, typical B. bovi s, were discovered in red blood cells 5, 8 or 9 days after inoculation . The highest percentage of parasitised erythrocytes (PPE) was 15%. Th e babesiosis resulting from cryopreserved parasites was the same as th at resulting from fresh parasites inoculated by ticks. Typical clinica l signs were found, such as continuous fever (the highest temperature was 41.3 degrees C), anaemia, icterus and haemoglobinuria. Infected ca lves, which were not treated, died. Cryopreservation is a simple and r eliable method for longterm preservation of B. bovis of water buffaloe s.