The response of turkey poults to experimental infection with strains ofM. gallisepticumof different virulence and withM. gallinarum

Abstract

SUMMARYIn turkey poults aged up to 28 days, a virulent S6 strain of Af. gallisepticum was recovered more frequently from more tissues for a longer time than were other strains. The virulent strain caused nervous signs and gross brain lesions in poults, and was often isolated from the brain, suggesting its neurotropism. All M. Gallisepticum strains were isolated from the synovial fluid of hocks, but swollen hocks and foot pads were seen only in poults infected with the A514 strain. It would seem, therefore, that although proclivity for joints was shown by all strains, only A514 produced grossly pathogenic effects in these young birds. All strains of Af. gallisepticum showed some proclivity for respiratory tissues. Signs, gross lesions and recoveries of mycoplasma frequently failed to correlate. Perosis was seen in only two poults; these were infected with M. gallinarum with which the condition may, or may not, be associated. Serological reactions to both the rapid serum agglutination and haemagglutination inhibition tests developed in the 3rd and 4th weeks of life in all poults infected with Af. gallisepticum strains although false positives and negatives were recorded.The main results of infection with the strains in turkey poults and in a similar study in chicks are summarised. INTRODUCTIONIn a previous paper, Power and Jordan (1976) used three strains of M. gallisepticum and one strain of M. gallinarum and showed they differed in virulence as assessed by mortality in chicks and turkey poults. This present paper describes a sequel experiment in which the same four strains of mycoplasma were used to infect turkey poults under similar conditions in order to examine effects other than mortality. Clinical signs, gross lesions and the distribution and persistence of mycoplasma in a wide variety of tissues, together with serological results, were recorded in turkey poults at specified intervals after infection.

Pathogenicity ofin vivo‐passagedMycoplasma imitansin turkey poults in single infection and in dual infection with rhinotracheitis virus

“…It has also been shown that an Mg isolate which had not undergone laboratory passage caused airsacculitis when inoculated into 11 week old turkeys whereas the same strain, after 100 in vitro passages, did not do so (Nutor, 1969). Differences in virulence of Mg of low (2) and high (152) in vitro passage level were also shown in tracheal organ culture (Power & Jordan, 1976), in SPF chicks (Varley & Jordan, 1978a) and in turkey poults (Varley & Jordan, 1978b). Our strain of Mim had undergone only 11 in vitro passages before it was used in this study, but it was not known if this had caused any loss of natural virulence.…”