Experimental infection of castrated lambs with Mycoplasma agalactiae.

The course of experimental infection in groups of 6-month-old castrated lambs with field isolates of Mycoplasma agalactiae from France was followed culturally and serologically for 7 months. Infection with an ovine field isolate following inoculation by different routes and contact exposure was compared with that caused similarly by a caprine field isolate. The prolonged infections produced were symptomless apart from limited arthritis in one animal inoculated with the isolate from sheep and increased lachrymation in another associated with the goat isolate. The ovine isolate was more virulent in that ante- and post-mortem recoveries of the organism were more consistent and the serological responses more pronounced. Serological responses varied between animals and between strain infections, and the results of the film inhibition test were more consistent than those of the complement fixation test. The limitations of both these tests for detecting carrier infections are discussed.

Egg transmission of a respiratory isolate of Mycoplasma synoviae and infection of the chicken embryo.

Egg transmission of Mycoplasma synoviae (Ms) was demonstrated in broiler breeder birds of over 40 weeks of age from a commercial flock that had been infected during rearing and in birds experimentally inoculated before onset of lay. Infection of growing birds with Ms did not prevent egg transmission in adult life. The embryonated eggs of experimentally infected hens were less susceptible to infection by inoculation than those of specific pathogen-free birds. Some chicks with maternal antibody were found to be infected at hatching and in these maternal antibody was not mycoplasmacidal. Indeed by protecting the embryo maternal antibody may have promoted hatching of infected chicks.

Maternal antibody to a respiratory isolate of Mycoplasma synoviae and contagious infection of chicks after hatching.

In chicks infected with Mycoplasma synoviae after hatching agglutinins were not detected for between 27 and 42 days. By this age the largely asymptomatic infection had spread extensively by contact. Detection of maternal agglutinins from hatching to 9 days in chicks from infected hens indicated that this should be considered as a diagnostic technique particularly where access to parent stock is limited.

Cloacal infection with Mycoplasma gallisepticum and the effect of inoculation with H120 infectious bronchitis vaccine virus.

Infectivity of an isolate of Mycoplasma gallisepticum of low virulence was studied in specific pathogen free chickens from 1 day old until after the onset of lay. Widespread cloacal infection developed and it was discussed in relation to the low serological response. The effects produced by inoculation of H120 infectious bronchitis vaccine virus and coming into lay were associated with changes in serological response and increased cloacal cultural recovery. The possibility of ascending cloacal infection giving rise to egg transmission was considered and compared with other routes whereby ovules may become infected.

Association of Mycoplasma synoviae with respiratory disease of broilers.

Serological and cultural investigation of broilers with respiratory disease implicated Mycoplasma synoviae infection in the syndrome which was characterised by variable mortality up to 20% at 6-8 weeks of age in association with Escherichia coli septicaemia. Preliminary experimental studies using specific-pathogen-free birds confirmed that the Mycoplasma synoviae concerned was of the respiratory type, first described in the USA as causing a rapidly spreading, persistent upper respiratory tract infection associated with production losses and in some flocks condemnations due to air sacculitis.