Assessment of Mycoplasma gallisepticum vaccine efficacy in a co-infection challenge model with QX-like infectious bronchitis virus

Abstract

Mycoplasma gallisepticum (MG) is the primary cause of chronic respiratory disease in poultry. We investigated the protective efficacy of the live-attenuated ts-11 and 6/85 MG vaccines against a local MG strain and, in order to enhance signs and mimic a typical field situation, we co-infected birds with a virulent strain of QX-like infectious bronchitis virus (IBV). Both vaccines showed similar ability to protect infected chickens from clinical signs, although ts-11 performed slightly better. Despite the lower protection against clinical disease, 6/85-vaccinated birds had significantly (P ≤ 0.05) lower tracheal lesion scores and mucosal thickness at day 28 post-vaccination (7 days post-challenge [dpc] with MG, 2 dpc IBV) and day 31 post-vaccination (10 dpc MG challenge, 5 dpc IBV) compared to ts-11 vaccinated birds, but these difference was not significant at day 33 (12 dpc MG, 7 dpc IBV). Pathogen infection and replication was assessed by qPCR, and the 6/85 vaccine produced a more significant (P ≤ 0.05) reduction in MG replication in the lungs, kidneys and livers but enhanced late replication in bursae and caecal tonsils. In contrast, the ts-11 vaccine had a more pronounced reductive effect on replication in tracheas, air sacs, bursae and heart at days 28 and 31, yet increased replication in lungs. Interestingly, both vaccines provided non-specific protection against IBV challenge. The co-challenge model provided useful data on vaccine efficacy, especially on days 31 and 33, and tracheas, lungs, air sacs, kidneys, liver and caecal tonsils were the best organs to assess.

Prevalence and molecular characterization of infectious bronchitis virus isolated from chicken in Bangladesh

“…One of the most economical important diseases of poultry is infectious bronchitis virus (IBV) [5]. It is highly contagious and causing devastating economic losses to chickens [6,7]. The virus causes respiratory disease characterized by tracheal rales, coughing, and sneezing along with excess accumulation of mucus in bronchi and reduced growth rate in broilers, nephritis, urolithiasis, and irreparable damage to oviduct, leading to abnormal eggs production with high mortality rates in affected poultry flocks [8,9].…”

Current status of vaccine research, development, and challenges of vaccines for Mycoplasma gallisepticum

“…The interaction and modulation of host immune responses is of major importance in the preparation of effective vaccine against MG infection. More importantly, infection by other respiratory pathogens must be taken into account in preparation of vaccine against MG. For instance, several studies reported co-infection of MG with influenza virus, Escherichia coli and infectious bronchitis virus ( Stipkovits et al., 2012 ; Sid et al., 2016 ; Bwala et al., 2018 ; Awad et al., 2019 ; Canter et al., 2019 ; Wu et al., 2019 ). A previous report assessed the efficacy of MG vaccine in a co-infection model and suggested that ts-11 and 6/85 provided protection up to some extent against virulent MG strain.…”

“…The 2 vaccines provided nonspecific protection. Whereas, the ts-11 proved to be more effective than 6/85 vaccine in trachea, bursa, and air sacs but not in lungs ( Bwala et al., 2018 ). In addition, a recombinant adenovirus-based vaccine candidate was developed and evaluated for co-infection against infectious bronchitis virus and MG in chickens.…”

Common Respiratory Diseases of Poultry in Bangladesh: A Review

“…Infectious bronchitis is the most economic disease in poultry all over the world including Bangladesh caused by the Infectious bronchitis virus (IBV). It is highly contagious and causes increase mortality, low egg production, hatchability and egg quality, and increase medication cost (Bwala et al, 2018). The virus can be transmitted through aerosols and mortality could be varied from 40-90%, and can affect chickens of all ages.…”