Haemorrhagic Septicaemia
Haemorrhagic Septicaemia
Haemorrhagic septicemia (HS) is an acute pasteurellosis manifested by an acute and highly fatal septicemia caused by 1 of 2 serotypes of P multocida , designated B:2 and E:2. Serotype E:2 has been recovered only in Africa; B:2 causes the disease elsewhere and also has been recovered from cases in Egypt and the Sudan. Serotypes closely related antigenically to serotype B:2 have been implicated in limited outbreaks of a disease indistinguishable from HS in deer and elk. P. multocida is an extracellular parasite, and immunity is primarily humoral. Although it may be seen at any time of year, the worst epidemics occur during the climatic conditions typical of monsoon (high humidity and high temperatures)
The mortality rate is high when the agent is introduced to virgin or nonendemic regions. Losses vary widely in endemic areas. The heaviest losses occur during the monsoon rains in Southeast Asia, and it is thought that the organisms, which can survive for hours and probably days in the moist soil and water, are transmitted widely at this time.
Epidemics of haemorrhagic septicemia occur mainly among cattle and water buffalo (Bubalus bubalus) characterized by an acute, highly fatal septicemia with high morbidity and mortality.
These two species are also the major reservoir hosts. Outbreaks have been reported occasionally among pigs in some Asian countries, and cases are seen infrequently in sheep and goats. Goats have been infected experimentally. Hemorrhagic septicemia has also been reported in bison (Bison bison), African buffalo (Syncerus caffer), camels, elephants, horses, donkeys and yaks. Systemic pasteurellosis has been reported in various species of deer including fallow deer (Dama dama), sika deer (Cervus nippon) and chital deer (Axis axis), as well as elk (Cervus elaphus canadensis), pronghorn (Antil ocapra americana) and other wild ruminants
P. multocida is transmitted by ingestion or inhalation, either during direct contact or via fomites, feed and water. The serotypes that cause hemorrhagic septicemia are probably shed into the oropharynx. Some animals become carriers, maintaining the organism in the lymphatic tissues associated with the upper respiratory tract, and periodically shedding it in nasal secretions. Excretion may be triggered by stress.
P. multocida does not remain viable for long periods in the environment, but it can survive for hours and possibly days in damp soil or water. Rainy conditions and high humidity facilitate transmission. Biting arthropods do not seem to be important in the epidemiology of this disease
The incubation period is usually few hours to days but some animals can carry the organism for varying periods without symptoms.
Most cases in cattle and water buffalo are acute or peracute. Although the disease is very similar in both species, buffalo tend to have more severe clinical signs and a shorter course of disease. A fever, dullness and reluctance to move may be the first signs. Salivation and a profuse serous nasal discharge develop, and edematous swellings become apparent in the submandibular region. These swellings spread to the neck and brisket. In calves, hemorrhagic gastroenteritis has also been reported. Respiratory distress occurs, with frothing at the mouth, and the animal usually collapses and dies 6 to 48 hours after the initial clinical signs. Either sudden death or a protracted course up to a few days is also possible. Animals with clinical signs, particularly buffalo, rarely recover. Chronic cases have not been reported.
Similar clinical signs including severe depression, profuse salivation, edema of the head, neck and brisket, and severe respiratory distress with foamy nasal discharge have been reported in some wild ruminants with systemic pasteurellosis.
Various sulfonamides, tetracyclines, penicillin, and chloramphenicol (where its use is permitted) are effective if administered early. Because of the rapid course of the disease and the frequent difficulty of access to animals, antimicrobial therapy often is not practicable. Although multiple antibiotic resistance has been reported for some strains of P multocida , it has not been described for the HS serotypes.
The principal means of prevention is by vaccination. Three kinds of vaccine are widely used: plain bacterin, alum-type precipitated bacterin, and oil-adjuvant bacterin. The most effective bacterin is the oil-adjuvant-one dose provides protection for 9-12 months; it should be administered annually. The alum-precipitated-type bacterin is given at 6-month intervals. Maternal antibody interferes with vaccine efficacy in calves. The oil-adjuvant vaccine has not been popular because of difficulty in syringing and occasional adverse tissue reactions. A live intranasal vaccine prepared from a B: 3, 4 serotype of deer origin is being used with reported success in Southeast Asia.
Formaldehyde inactivated culture of Pasteurella multocida adsorbed on aluminum hydroxide gel is available in India for prophylactic vaccination against HS in cows and buffaloes with the following vaccination regimen:
Primary vaccination: six months of age or above, followed by booster dose after one month.
Revaccination: Annually