As in many countries in South-East Asia, outbreaks of haemorrhagic septicaemia (HS) are common in Cambodia, with high morbidity and mortality rates reported. The Department of Animal Health and Production received reports of 82 outbreaks in 15 provinces in 2009, and 52 outbreaks in 10 provinces in 2010. Although buffaloes are generally considered to be more susceptible than cattle, both species are affected. In case studies of outbreaks conducted in Koh Pen and Kampong Reap in Kampong Cham province in 2010, morbidity in cattle was 59%, but 39% in buffaloes. Mortality rates were very high in both species (97% for cattle and 98% for buffaloes). Diagnostic investigations of these outbreaks led to isolation and confirmation by serology and polymerase chain reaction (PCR) that infections in both cattle and buffaloes were caused by Pasteurella multocida type B2. Widespread vaccination for HS occurs in Cambodia, with coverage currently considered to be approximately 50% of the large ruminant population, yet there is little information on the efficacy of the vaccine used. A post-vaccination serology study compared antibody titres of 60 cattle that had each been injected subcutaneously with 2 mL of killed HS vaccine in an aluminium hydroxide gel adjuvant with antibody titres from 20 control animals. Sera were collected at days 0,21 and 180, and results confirmed a very strong serological response to vaccination. Serology at day 21 identified 100% of vaccinated animals with a titre ＞ 1:320. At day 180, 100% of vaccinated animals had a titre ＞ 1:160, and 95% had a titre ＞ 1:320. This suggests that if post-vaccination antibody titres correlate with, or are a useful indicator of, protection against infection, HS vaccine efficacy as currently practised in this trial appears to be very good. This questions the recommendation of vaccinating against HS every 6 months. It is recommended that further work is done to determine if such high titres persist for longer than 180 days.
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