White and red blood cell picture in rabbits experimentally infected with strains of the rabbit haemorrhagic disease (RHD) virus without or with variable haemagglutination capacity

The aim of the study was to establish if haemagglutination of rabbit haemorrhagic disease virus (RHDV) affects haematological picture of peripheral blood in rabbits and the pathogenicity of the virus. The study analyzed white and red blood cell picture in rabbits experimentally infected with two non-haemagglutinating (HA-) RHDV strains (Frankfurt and Asturias) and one strain with variable haemagglutination capacity (HA+/-) (Hagenow). Studies with HA- and HA +/- are rare and relate only to 4 HA- strains (2 RHDV: BLA and Rainham; 2 RHDVa: Pv97 and 9905) and 1 HA+/- RHDV strain: ŻD, where less changes in haematological indices and less pathogenicity were observed. We found that changes caused by HA- Frankfurt strain were related to the number of neutrophils and thrombocytes, while in HA- strain Asturias, in thrombocytes and leukocytes. Changes evoked by HA+/- Hagenow strain pertained to the number of eosinophils, thrombocytes, leukocytes, monocytes, and concentration of hemoglobin. Mortality caused by the Frankfurt strain was 100% between 36 and 48 h post infection (p.i.), while that caused by Asturias strain was 100% between 24 and 36 h p.i., and that observed in case of Hagenow strain was 90% between 36 and 48 h p.i. The changes in haematological picture caused by the HA- and HA+/- RHDV strains were less intensive than those found in case of the HA+ RHDV strains, which cannot be confirmed for pathogenicity, and is not in line with the existing hypothesis suggesting higher pathogenicity in HA+ viruses.