Evaluation of the egg transmission and pathogenicity of Mycoplasma gallisepticum isolates genotyped as ts-11

Abstract

Live Mycoplasma gallisepticum vaccines are used for the control of respiratory disease, egg production losses and egg transmission associated with M. gallisepticum infection in long-lived poultry. The first field case of apparent increased virulence and vertical transmission of ts-11, a live M. gallisepticum vaccine, has been reported. In that study a M. gallisepticum isolate from the broiler progeny of ts-11-vaccinated breeders was genotyped as ts-11 by sequence analysis of four different genetic targets and Random Amplified Polymorphic DNA and found to be significantly more virulent than ts-11 vaccine. The objective of the current study was to evaluate the rate of egg transmission and pathogenicity of ts-11 vaccine and isolates recovered from ts-11-vaccinated breeders (K6222B) and their broiler progeny (K6216D) which had been genotyped as ts-11. Groups of 28-week-old specific pathogenfree chickens at 87% average weekly egg production were inoculated with sterile broth media (negative controls), ts-11 vaccine, K6222B, K6216D or R strain (positive controls) by eye-drop and aerosol. K6216D transmitted via the egg at an average rate of 4.0% in the third and fourth weeks post-infection, while egg transmission of K6222B and ts-11 vaccine was not detected. M. gallisepticum was isolated from the air sacs, ovaries and oviducts of hens infected with K6216D and K6222B, but not from those infected with ts-11 vaccine. K6216D and K6222B both induced respiratory signs and significantly more tracheal colonization and more severe tracheal and air sac lesions than ts-11 vaccine (P ≤ 0.05). There were no substantial differences in the egg production of ts-11, K6216D and K6222B infected groups. These results provide the first conclusive evidence of transovarian transmission of an isolate genotyped as ts-11 and indicate that isolates genotyed as ts-11 vary in their virulence and ability to transmit via the egg.

Identification of Strain-Specific Sequences That Distinguish a Mycoplasma gallisepticum Vaccine Strain from Field Isolates

“…The clinical picture was obtained from history at submission and/or interviews with field veterinarians. Bird trials confirmed the pathogenicity of two of the isolates (K6212D and K6222B) (9, 32). One reisolate (K5322C-13) was obtained from specific-pathogen-free layer-type chickens at 2 weeks postvaccination with ts-11.…”

“…gallisepticum isolates from the broilers and their parents were indistinguishable from the ts-11 vaccine strain by the genotyping methods used and were termed “ts-11-like” isolates (9). The epidemiology of the outbreaks, as well as genotyping and pathogenicity results, indicate that an increase in virulence and vertical transmission of ts-11 vaccine occurred and that the ts-11-like isolates were very likely revertants derived from ts-11 vaccine (9, 16, 32). …”

Isolation and Antimicrobial Sensitivity of Mycoplasma synoviae and Mycoplasma gallisepticum from Vaccinated Hens in Mexico

“…In our study, we found three MG strains whose DNA banding patterns matched those of the F strain, which was originally a vaccine strain; currently, the F strain can be considered a vaccine or field strain, with nine strains corresponding to untyped wild-type field strains. In the study by Armour and Ferguson-Noel [24], vaccine mycoplasmas failed to colonize bird tissues; however, under field conditions, as in our study, wild strains can compete for receptors of target cells with the vaccine strain TS-11. Most likely, this competition is one of the reasons why this strain was not isolated successfully.…”

“…Due to these disorders, it is essential to consider the possible risk of a reversal of pathogenicity when applying the ts+ MS-H strain or other live ts+ vaccines against Mycoplasma spp. In specific-pathogen-free hens vaccinated under laboratory conditions, Armour and Ferguson-Noel [24] and El Gazzar et al [25] demonstrated that the ts+ MG TS-11 strain could revert its thermosensitivity and pathogenicity, cause septicemia, and invade the ovary, thus infecting the eggs.…”

Immune-Endocrine Interactions in the Fish Gonad during Infection: An Open Door to Vertical Transmission

“…As mammalian pathogens are transplacental and transferred through breastfeeding, the transovarian pathway seems not to be highly relevant (see for review [87][88][89][90]). In birds, as in fish, however, gonadal infection of both sexes is used to evade the immune system and also to assist transmission to the next generation [91][92][93][94][95]. As regards fish, several pathogens have been found to infect gonads in a few species (see Table 2).…”