Abstract

Haemorrhagic septicaemia (HS) is a severe septicemic disease affecting cattle and other ruminants, particularly in tropical and subtropical regions, causing significant economic losses. Vaccination remains the most effective control strategy, and several serological assays, including Indirect Haemagglutination Assay (IHA) are used to evaluate vaccine-induced antibody responses.
This study assessed rabbits as an alternative model for evaluating the potency of Pasteurella multocida vaccines using the IHA test and investigated its correlation with LD50 induced in mice. Ten vaccine batches were evaluated using calves, New Zealand rabbits and swiss mice. Post-vaccination antibody titers showed strong immune responses in both species, with higher titers associated with increased protection in the mouse challenge test. A positive correlation between IHA titers and LD50 values was observed.
These findings suggest that the IHA assay in rabbits may provide a reliable and ethical alternative way for vaccine potency testing, reducing dependence on traditional mouse challenge assays.

Key words: Pasteurella multocida, Haemorrhagic septicaemia, ruminant, vaccine evaluation, rabbit as alternative model