The present project was planned to characterize Pasteurella multocida isolates from apparently healthy carrier and infected cattle. A total of 500 animals (live 250 and slaughtered 250) of different age groups and both sexes were examined for the evidence of harbouring Pasteurella multocida in their respiratory tracts. The samples were collected from the live animals through a sterilized cotton swab passed in their nasal cavity. In slaughtered animals the cotton swabs were smeared directly to laryngeo-tracheal region approached from the cut part of the trachea. In infected animals citerated blood of live animals was processed for isolation of the organisms; whereas a long-bone was collected and processed for bacteriological examination in slaughtered/dead animals. The primary isolation of the organism was attempted in tryptic soya broth/tryptic soya agar: The identification of the isolated strains was carried out on the basis of their cultural characteristics on arious media, morphology and staining reaction, sugar fermentation and other biochemical tests.

Of the 500 healthy animals examined for their carrier status, none proved positive for the Pasteurella multocida organism in their respiratory tracts. Of the 10 outbreaks investigated, only 6 cases yielded Pasteurella multocida strains which proved highly virulent both for rabbits and mice. All the six strains were quite uniform in their various characteristics. All fermented glucose, fructose, mannose, mannitol, sorbitol and sacharose, producing acid only and n gas. None of them fermented arabinose dulcitol maltose, lactose, raffinose and salicin.

All the six strains gave a positive reaction for catalase, oxidase indole production, nitrate reduction and H2S production tests, and negative reaction for methyle red, voges prausker, urease activity and gelatin liquefaction tests. None of the strains exhibited motility examined through hanging drop technique.

All the 10 outbreaks occurred during the rainy months of August and November. All the infected animals were in the age group of 1 to ½ years. The course of the disease was 1-2 days. The clinical signs observed included dullness, depression, inappetance, tympany and a high rise of temperature upto 106°F. The swelling of the throat, which of course developed at an advanced stage of the disease was also observed. In this study conducted on limited number of animals the role of carriers in epidemiology of haemorrhagic septicaemia was observed to be quite insignificant. The outbreaks of the disease occurred during summer/winter rainy seasons necessitating the prophylactic vaccination of our cattle and buffaloes before these period of the year