Haemorrhagic Septicemia in Water Buffalo and Cattle

• Hemorrhagic septicemia (HS) is an acute, highly fatal form of pasteurellosis that affects mainly water buffalo, cattle, and bison.
• This vaccine has been associated with sporadic outbreaks and virulence in young animals.
• Attenuated or modified-live vaccines have been used with some success.
• Hemorrhagic septicemia is a World Organization for Animal Health (OIE)–listed animal disease and is considered the most economically important bacterial disease of water buffalo and cattle in tropical areas of Asia, particularly in India and other parts of southeast Asia where water buffalo populations are high.
• Classical hemorrhagic septicemia as defined by the OIE is caused by Pasteurella multocida serotypes B:2 and E:2 (Carter and Heddleston classification system).
• Serotype B:2 has been identified in most areas where the disease is endemic, whereas serotype E:2 has been found only in Africa.
• Up to 5% of healthy water buffalo and cattle are colonized by small numbers of P multocida serotype B:2 or E:2, which can be shed during periods of stress.
• Common stressors associated with outbreaks of hemorrhagic septicemia include high temperature and humidity, concurrent infection (blood parasites or foot and mouth disease), poor nutrition, or work stress.
• Although outbreaks can occur at any time, disease is most prevalent during the rainy season.
• Increased outbreaks associated with high rainfall are most likely due to the multiple stressors present during this time and the moist conditions, which prolong the survival time of the organism in the environment.
• Infection occurs by contact with infected oral or nasal secretions from either healthy carrier animals or animals with clinical disease, or by ingestion of contaminated feed or water.
• Infection begins in the tonsil and adjacent nasopharyngeal tissues.
• Subsequently, bacteremia leads to dissemination and rapid growth of bacteria in various locations, tissue injury, a host cytokine response, and release of lipopolysaccharides that results in a rapidly progressing endotoxemia.
• Clinical signs can appear 1–3 days after infection, and death can occur within 8–24 hours after the first clinical signs develop.
• In endemic areas, HS affects older calves and young adults, and morbidity and mortality are variable.
• In nonendemic areas, epizootics can occur with high morbidity and mortality that can reach 100%.
• Water buffalo tend to have higher morbidity with more severe clinical disease than cattle.
• Recovery can stimulate acquired immunity to homologous and often heterologous strains of P multocida, and some of these animals become healthy carriers that can be a source of infection for future outbreaks.
• In peracute cases of hemorrhagic septicemia that result in death within 8–24 hours, animals often have fever, hypersalivation, nasal discharge, and labored respiration; however, because of the short duration of disease, these clinical signs may easily be overlooked.
• Clinical diagnosis of hemorrhagic septicemia in endemic areas is based on history, lapses in vaccination, environmental conditions, and the characteristic clinical signs and lesions of disease.
• The commonly used alum-precipitated and aluminum hydroxide gel vaccines have shorter durations of immunity (approximately 4–5 months with variable protective efficacy), and twice yearly booster vaccinations are recommended.
• Maternal immunity can interfere with vaccine efficacy in calves.
• Sporadic cases of hemorrhagic septicemia are more difficult to diagnose clinically and could be confused with blackleg, lightning strike, or snakebite.
• A definitive diagnosis of Hemorrhagic Septicemia (HS) is based on isolation of P multocida serotype B:2 or E:2 from the blood and tissues of a patient with typical clinical signs.
• During outbreaks, any patient with a fever should be treated with intravenous antimicrobials as soon as possible to quickly obtain systemic bactericidal antimicrobial concentrations.
• The oil-adjuvant vaccine provides protection for 9–12 months and is administered annually.
• Antimicrobials administered early in the disease are effective against hemorrhagic septicemia if administered very early in the disease.
• Hemorrhages are often most prominent in the pharyngeal and cervical lymph nodes in cases of hemorrhagic septicemia.
• The characteristic lesion of hemorrhagic septicemia is swelling of the subcutis and muscle of the submandibular region, neck, and brisket by clear to blood-tinged edema fluid.
• Pulmonary congestion and edema, sometimes with interstitial pneumonia, and gastroenteritis may occur in some cases of hemorrhagic septicemia.
• Various sulfonamides, tetracyclines, penicillin, gentamicin, kanamycin, ceftiofur, enrofloxacin, tilmicosin, and chloramphenicol have been used effectively to treat Hemorrhagic Septicemia (HS).
• Serous to serofibrinous fluid may also be present in the thorax, pericardium, and abdominal cavity in cases of hemorrhagic septicemia.
• Subcutaneous swelling in the pharyngeal region that extends to the ventral neck and brisket (and sometimes the forelimbs), progressive respiratory distress, cyanosis, terminal recumbency, and sometimes abdominal pain with diarrhea are also seen in clinical cases of Hemorrhagic Septicemia (HS).
• There is typically widespread congestion with petechiae and ecchymoses in tissues and on serosal surfaces, particularly in the respiratory, GI, and urinary systems in cases of hemorrhagic septicemia.
• It is important that the vaccines are made from the strains of P multocida circulating in the regions of intended use to obtain maximal effectiveness.
• Acute disease can persist for up to 3 days, and less often up to 5 days, and is characterized by fever of 104°–106°F (40°–41.1°C), apathy or restlessness and reluctance to move, hypersalivation, lacrimation, nasal discharge that begins as serous and progresses to mucopurulent.