Evaluation of the virulence of two recent Dutch Mycoplasma synoviae isolates in commercial broilers
H. Bataille1, J. Wiegel1, N.D. de Bruijn1, & A. Feberwee1
1Royal GD, P.O. Box 9, 7400 AA Deventer, The Netherlands
Introduction
Next to subclinical Mycoplasma synoviae (Ms) infections also pathogenic Ms strains have been described which can cause airsacculitis, infectious synovitis or egg shell apex abnormalities. Also the synergism between Ms infection and other respiratory pathogens has been demonstrated. Prevalence of Ms is high in commercial broilers and the effect of recent Ms field strains on the technical performance of commercial broilers is not clear. In the present study the virulence of two recent Dutch Ms isolates was evaluated in 5 day old Ms free commercial broilers in the presence and absence of IB vaccine strain. One Ms strain was previously isolated from rearing layers (Ms joint) with infectious synovitis and the other Ms strain was isolated from broiler breeders with airsacculitis (Ms air sac).
Methods
• The study consisted of six groups with each 15 day old Ms free commercial broilers housed in HEPA filtered isolators.
• The virulence of a recent Ms joint and Ms air sac isolate was evaluated in presence and absence of IBH120 eyedrop vaccination (IBvacH210) (Table).
• Mortality, clinical signs, growth, serology (Ms antibody ELISA, Synbiotics) and Ms PCR (In-house) were evaluated (Table).
• At post mortem the percentage of birds with air sac lesions (ASL) (Figure 1) was determined and mean ASL score.
• Histological examination (HE) and Ms in situ hybridization (ISH) test to investigate the role of Ms in ASL (Table).
Results
• Respiratory signs: mild, in all groups except NC and Ms air sac.
• Mortality: low, no significant difference between groups.
• Serology and PCR: high percentage positives in all Ms groups.
• Mean ASL score: high percentage ASL in all Ms groups, mean ASL score of 0.7- 1.7 with a synergistic effect of IBvacH120 (Figure 2 and 3).
• Mean Growth: Up to 15% reduced growth in all Ms groups (Figure 4).
• Hydrops ascites: observed only in all Ms groups (Figure 1B).
• Joint disorders: not observed during the experimental period.
• HE and Ms ISH test results: a mild tracheitis in all Ms groups (Figure 1C), with an infiltrate of heterophils, macrophages and lymphocytes. Ms was present between the cilia of the epithelium (Figure 1E). ASL (Figure 1D) with a variable amount of necrotic debris, degenerated heterophils and macrophages. Scattered, macrophages had phagocytosed Ms organisms (figure 1G). Hyperplastic air sac epithelium with stromal fibrosis, edema and lymphoplasmacytic infiltrates. Sporadically, Ms was present in the air sac epithelium (figure 1F).
is significantly different (p<0.05). Fishers exact test.
Conclusion & Discussion
• Both Ms isolates:
- colonized well in commercial broilers;
Figure 3. D35 mean ASL score: a different superscript is significantly different (p<0.05). Kruskall Wallis, post hoc Dunn’s test & Bonferroni correction.
Figure 4. Mean growth: a different superscript is significantly different (p<0.05). One-way ANOVA & Bonferroni correction.
Mean growth Ms air sac + IBvacH120 was significantly lower than NC (p<0.05) and NC + IBvacH120 (p<0.01). Mean growth Ms joint + IBvacH120 was significantly lower than NC + IBvacH120.
- caused a low mortality rate and mild respiratory signs in commercial broilers;
- did not induce joint disorders during the experimental period;
- resulted in hydrops ascites and high percentage of birds with ASL in the presence and absence of IBvacH120.
• The effect on growth and ASL was increased by the IBvacH120 (synergistic effect)
• ASL and hydrops ascites result in increased condemnation rates at slaughter.
Acknowledgements
This research was funded by a grant from the Dutch poultry sector AVINED.
References
1. Landman, W.J.M. 2014. Is Mycoplasma synoviae outrunning M. gallisepticum? A viewpoint from the Netherlands. Avian Pathology, 43(1):2-8.
2. Kleven, S.H., Anderson, D.P. 1972. Airsacculitis in broilers from Mycoplasma synoviae: effect on air-sac lesions of vaccinating with infectious bronchitis and Newcastle virus. Avian Diseases, 16: 915-924.