Mycoplasma gallisepticum is the most pathogenic mycoplasma species affecting commercial poultry, and it spreads quickly once introduced to a flock (El-Gazzar, 2025). Producers often know the disease by its clinical names, chronic respiratory disease and infectious sinusitis in chickens, both describing the same underlying infection. Because clinical signs range from mild to severe, early recognition shapes how much the disease affects flock performance.
What Are the Symptoms of Mycoplasma in Chickens?
Affected birds show a range of respiratory symptoms, including sneezing, coughing, rales and nasal discharge (El-Gazzar, 2025). Feed efficiency and weight gain both decline once infection sets in, and in broilers this reduction is measurable within weeks (Chen et al., 2024). Morbidity is high but mortality is typically low, so subtle symptoms can persist for days before a supervisor notices anything wrong. Flock weight data gathered through automated daily weighing can flag that early growth dip before visual signs become obvious.
Mycoplasma Eye Infection in Chickens
The eye infection associated with mycoplasma typically starts as conjunctivitis, with frothy discharge and swelling around the eyelids (El-Gazzar, 2025). In one documented outbreak among layer pullets, birds with closed or swollen eyes ate less because they struggled to find feed, and roughly ten percent died as a result (Nunoya et al., 1995). This link between impaired vision and reduced intake means eye infection cases carry a real weight cost, not just a welfare concern. Hands-on checks with the BAT1 manual poultry scale let supervisors catch birds that are underweight for their age during routine handling, even before eye symptoms become visually obvious.
How to Treat Mycoplasma Gallisepticum in Chickens
Most M gallisepticum strains respond to tylosin or tetracyclines, both commonly used to reduce clinical signs and limit egg transmission (El-Gazzar, 2025). Antimicrobials ease symptoms but do not clear the infection, so treated birds remain lifelong carriers. Prevention relies on sourcing chicks from mycoplasma-free breeder flocks, maintaining strict biosecurity and, in high-challenge regions, vaccinating during the growing phase (El-Gazzar, 2025). Because eradication is not achievable with medication alone, ongoing monitoring matters more than a single round of treatment.
Protecting Growth Performance in Flocks with Mycoplasma
Because feed efficiency and weight gain both suffer once mycoplasma takes hold, tracking flock weight trends gives an early warning that clinical signs alone may miss. The BAT2 Connect automatic scale logs daily flock averages as birds step on voluntarily, without adding handling stress to already compromised birds.
Manual checks remain valuable alongside automatic data. Bird-by-bird weight checks let supervisors confirm which individuals are falling behind and need closer veterinary attention, something flock averages alone cannot show.
Once treatment starts, comparing weight trends before and after through the BAT Cloud data platform helps confirm whether a flock is recovering as expected or whether secondary infection has complicated the picture (El-Gazzar, 2025).
References
Chen, X., Cui, J., Wang, Y., Han, K., Huo, N., & Wang, J. (2024). Dietary supplementation with Bacillus subtilis KC1 alleviates the negative effects of Mycoplasma gallisepticum on growth performance and amino acid metabolism of broiler chickens. Frontiers in Veterinary Science, 11. https://pmc.ncbi.nlm.nih.gov/articles/PMC11538993/
El-Gazzar, M. (2025). Mycoplasma gallisepticum infection in poultry. Merck Veterinary Manual. https://www.merckvetmanual.com/poultry/mycoplasmosis/mycoplasma-gallisepticum-infection-in-poultry
Nunoya, T., Yagihashi, T., Tajima, M., & Nagasawa, Y. (1995). Occurrence of keratoconjunctivitis apparently caused by Mycoplasma gallisepticum in layer chickens. Veterinary Pathology, 32(1), 11-18. https://pubmed.ncbi.nlm.nih.gov/7725593/