Persistence of the carrier status in haemorrhagic septicaemia (pasteurella multocida serotype 6:B infection) in Buffaloes

Abstract

Fifty-seven young buffaloes were experimentally infected or naturally exposed to haemorrhagic septicaemia (HS). Of these animals 32 became immune carriers. They were observed in groups for periods up to 360 days to monitor the appearance of pasteurellae in the nasopharynx and antibody status. In most animals pasteurellae appeared in the nasopharynx for a short period initially and disappeared. The organism reappeared intermittently and the longest observed period of reappearance was 215 days after exposure. All animals showed rising antibody titres with a peak lasting for 150 to 180 days and declining thereafter. Pasteurellae persisted in the tonsils and were isolated from 20 out of 27 carriers after slaughter. The longest period when isolation was made after slaughter was 229 days. The organism lodged in the tonsils was unaffected by antibacterial therapy using drugs to which the organism displayed in vitro sensitivity. It is concluded that in HS, carrier animals exist in an active as well as a latent state, the former appearing for short intermittent periods between long latent periods, when pasteurellae continue to remain in the tonsils which constitute a long-term reservoir.

Pasteurella

“…Apparently healthy animals may maintain oropharyngeal populations of P. multocida for long periods (De Alwis et al 1990 ;Muhairwa et al 2000 ), but the precise mechanisms by which bacteria can invade and colonize pulmonary or other tissue are not known. P. multocida does not normally cross healthy epithelium or the mucosa of the gastrointestinal tract of birds, yet it readily colonizes the lower respiratory tract if inoculated into the trachea and passes rapidly into the vascular system through the lower respiratory tract (Wilkie et al 2000 ).…”

“…For HS the natural route of infection appears to be via tonsillar tissue (De Alwis et al 1990 ), whereas for FC and bovine respiratory disease complex (BRDC) the respiratory tract appears to be the primary portal. Infection of birds via the lower respiratory tract is easy to achieve with relatively small doses of bacteria and may be facilitated by macrophages (Wilkie et al 2000 ).…”

Haemorrhagic septicaemia, its significance, prevention and control in Asia

“…However, import of animals from an area of unknown status vis-à-vis HS to a free area should comply with some practical procedures which should take into account the high percentage of carriers that occur in endemic areas than was earlier believed, and the persistence of the carrier status for long periods (De Alwis et al, 1990). Briefly, these are: (a) ensure that the animals originate from a region where no outbreaks of HS have occurred for a minimum period of one year; (b) carry out an indirect haemagglutination (IHA) testing (a test which can reveal recent infection) on the animals to be exported as well as on a random sample of incontacts in the country of origin whenever possible; (c) hold animals under observation for 2-3 weeks before transport (while carrying out the above testing); (d) quarantine them for the same period of time upon arrival to destination and; (e) vaccinate all animals at the end of the quarantine period.…”

Immunity against Pasteurella multocida in Animals Vaccinated with Inactivated Pasteurella multocida and Herbal Adjuvant 'DIP-HIP'

“…The acute disease can persist up to 3 -5 days, and is characterized by 104°-106°F (40°-41.1°C) fever, apathy or restlessness and reluctance to move, lacrimation, nasal discharge that begins as serous and progresses to mucopurulent, subcutaneous swelling in the pharyngeal region that can extend sometimes up to the forelegs, progressive respiratory difficulty, terminal recumbency, and possibly abdominal pain with diarrhea (The Merck Veterinary Manual). Despite treatment with antibiotics, the bacterium may persevere in the tonsils of carriers for several months and appear actively in the nasopharynx from where it may shed intermittently in the nasal secretions [18,19]. Hence, vaccination is the only approach to prevent HS at present [20].…”