Studies on the pathogenicity of Babesia bovis in water buffaloes after cryopreservation and resuscitation.

Packed erythrocytes infected with Babesia bovis were mixed with an equal 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 nitrogen (-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 splenectomised buffalo calves by injection via subcutaneous or intravenous or via intravenous and subcutaneous routes. The parasites, typical B. bovis, were discovered in red blood cells 5, 8 or 9 days after inoculation. The highest percentage of parasitised erythrocytes (PPE) was 15%. The babesiosis resulting from cryopreserved parasites was the same as that resulting from fresh parasites inoculated by ticks. Typical clinical signs were found, such as continuous fever (the highest temperature was 41.3 degrees C), anaemia, icterus and haemoglobinuria. Infected calves, which were not treated, died. Cryopreservation is a simple and reliable method for longterm preservation of B. bovis of water buffaloes.