Haemorrhagic septicaemia (Pasteurella multocida serotypes 6:b and 6:e)

After an incubation of about 3-5 days, the first signs are fever, dullness and reluctance to move, followed by salivation and a serous nasal discharge. Oedematous swellings appear in the throat region and spread down the neck to the brisket. Mucous membranes are congested and breathing becomes laboured, sometimes with froth at the mouth. Most animals collapse and die within 6-24 hours of the first signs, though the course may last up to 5 days, and sudden death also occurs. Necropsy shows gelatinous straw-coloured or bloody subcutaneous oedema, petechiae on serosal surfaces, blood-tinged fluid in body cavities, and swollen haemorrhagic pharyngeal and cervical lymph nodes.

Haemorrhagic septicaemia (HS) is caused by particular strains of Pasteurella multocida, a Gram-negative coccobacillus that normally lives as a commensal in the nasopharynx. The disease-causing types are the Asian B:2 and African E:2 serotypes, written 6:B and 6:E in the Namioka-Carter system. Cattle and buffalo pick the organism up by inhalation or ingestion; carriers hold it in upper respiratory lymphoid tissue such as the tonsils and shed it when stressed. The infection progresses to a terminal septicaemia, and the lesions reflect severe endotoxic shock with massive capillary damage: widespread haemorrhage, oedema and hyperaemia, with no microscopic change specific to the disease.

Cattle and water buffalo are the principal hosts and reservoirs, with buffalo the most susceptible; bison also act as reservoirs. Outbreaks occur less often in sheep, goats and pigs, and occasionally in camels, deer, horses and donkeys, and have killed large numbers of saiga antelope. HS is important in Asia, Africa and the Middle East; serotype B:2 occurs in Southern Europe, the Middle East, Southeast Asia, Egypt and Sudan, and E:2 in Egypt, Sudan and other African countries. Spread is by direct contact and via fomites such as contaminated feed and water. Up to 5% of cattle and buffalo in endemic areas can be carriers. The worst epidemics come in rainy, humid seasons, with crowding and poor condition. No human cases with B:2 or E:2 have been reported. It is WOAH-listed.

Shipping fever (often Mannheimia haemolytica) is frequently mistaken for HS but is not septicaemic and does not cause petechial haemorrhages across many organs. Blackleg and anthrax are hard to separate because of the peracute course and extensive oedema and haemorrhage, so laboratory culture is needed. Acute salmonellosis, mycoplasmosis, pneumonic pasteurellosis, lightning strike, snake bite and poisoning should also be considered.

Blood and vascular system (septicaemia), subcutaneous tissue of throat, neck and brisket, pharyngeal and cervical lymph nodes, respiratory tract and lungs, serosal surfaces, heart, gastrointestinal tract

Routine vaccination in endemic areas (bacterins protect roughly 4-12 months; maternal antibody limits efficacy in calves); avoid crowding, especially in wet weather; keep animals in good condition; stamping out in free countries.

Case fatality approaches 100% unless antibiotics are started very early, during the fever stage; animals with clinical signs, especially buffalo, rarely recover. Survivors of 6:B or 6:E infection are considered solidly immune.