Published online by Cambridge University Press: 15 May 2009
In the course of salmonella epizootics in guinea-pigs due to Salm. enteritidis and Salm. typhi-murium, respectively, salmonella conjunctivitis was widespread, and conjunctival swabbing was found to be a more effective procedure for detecting the spread of infection than the examination of rectal swabs. Eye-swabbing with segregation of eye-positive guinea-pigs and their cage-mates was apparently successful in controlling two Salm. enteritidis epizootics.
Later experimental observations showed that the conjunctival route was a far more effective one for producing systemic salmonella infection in guinea-pigs than the oral route. The 50% spleen infecting dose by the conjunctival route was of the order of 100 organisms, while a dose of 100,000,000 organisms of the same strain of Salm. enteritidis was ineffective by mouth. Blood-borne invasion from the primary conjunctival lesion occurred by the lymphatic route. Gut infection of guinea-pigs infected experimentally throughout the eye was secondary to spleen infection and probably occurred by excretion of salmonellae through the gall-bladder.
The importance of the conjunctival route in natural salmonella infections of guinea-pigs was confirmed by goggling experiments, which showed that, except in animals with complicating conditions such as pregnancy, effectively goggled guinea-pigs were highly resistant to infection in environments heavily contaminated with Salm. enteritidis which produced high infection rates in ungoggled control animals.
I am very grateful to my technician, Mr G. Sandys, for his enthusiastic help, particularly with the goggling experiments.