Antimicrobial Therapy and Antimicrobial Stewardship in Glässer's Disease

Article

Responsible Antibiotic Use Antimicrobial therapy Antimicrobial Resistance Herd health Veterinary Therapeutics Pig Health Swine Practice Swine Medicine Judicious Antibiotic Use Disease Management Glässer's Disease Glaesserella parasuis Antimicrobial Susceptibility MIC Testing

Antimicrobial Therapy and Antimicrobial Stewardship in Glässer's Disease

Antimicrobial therapy remains an important component of Glässer's disease management, particularly during acute outbreaks where early intervention can reduce morbidity and mortality. However, the increasing diversity of Glaesserella (Haemophilus) parasuis strains and the emergence of antimicrobial resistance highlight the importance of selecting therapy based on laboratory evidence whenever possible. Combining prompt treatment with responsible antimicrobial stewardship helps improve clinical outcomes while supporting long-term herd health.

Initiating Timely Treatment

The success of antimicrobial therapy depends largely on early recognition of disease and rapid initiation of treatment. Once systemic infection develops, affected pigs may deteriorate quickly, making timely intervention essential.

Because Glässer's disease frequently affects groups of pigs, treatment decisions should be based on the clinical status of the herd rather than individual animals alone. During acute outbreaks, clinically affected pigs require immediate therapy, while herd-level management measures should be implemented simultaneously to limit further disease spread.

Whenever possible, diagnostic samples should be collected before antimicrobial administration to maximise the likelihood of bacterial isolation and facilitate antimicrobial susceptibility testing¹.

Selecting Appropriate Antimicrobials

G. parasuis demonstrates variable susceptibility to different antimicrobial agents, making laboratory-guided treatment an important part of clinical decision-making. Isolation of the organism followed by minimum inhibitory concentration (MIC) testing provides valuable information for selecting the most appropriate antimicrobial for a particular outbreak.

Reliance on empirical treatment alone may be challenging because susceptibility patterns can differ among isolates. Therefore, antimicrobial selection should be based on susceptibility testing whenever bacterial isolates are available¹.

Regular monitoring of susceptibility profiles within a herd also supports more informed treatment protocols and allows veterinarians to detect changes in antimicrobial susceptibility over time.

Understanding Antimicrobial Resistance

Antimicrobial resistance has become an important consideration in the management of Glässer's disease. Resistance genes have been identified in G. parasuis, and resistance to several antimicrobial classes has been reported, emphasising the need for prudent antimicrobial use¹.

The presence of resistant isolates may reduce treatment success and limit therapeutic options during outbreaks. Consequently, routine susceptibility testing should be considered whenever possible, particularly in herds experiencing recurrent disease or reduced clinical response following antimicrobial therapy.

Monitoring resistance patterns also contributes to responsible antimicrobial use at both the herd and regional levels.

Integrating Antimicrobial Therapy with Herd Management

Although antimicrobial treatment plays an important role in controlling clinical disease, it should not be considered a standalone solution. Disease occurrence is influenced by multiple factors, including stress associated with weaning, mixing of pigs, transportation, environmental conditions and concurrent infections that facilitate systemic invasion by G. parasuis².

Addressing these predisposing factors alongside antimicrobial therapy can reduce disease pressure and improve overall treatment outcomes. Improvements in management, biosecurity and vaccination strategies complement antimicrobial use and contribute to long-term disease control.

Antimicrobial Stewardship in Daily Practice¹

Responsible antimicrobial stewardship involves using antimicrobials only when clinically indicated and selecting treatment based on laboratory evidence whenever feasible. Collecting samples before treatment, performing bacterial isolation and requesting susceptibility testing help ensure that antimicrobial therapy remains both effective and appropriate.

Periodic evaluation of herd treatment protocols and susceptibility data allows veterinarians to optimise therapeutic decisions while avoiding unnecessary antimicrobial exposure. This approach supports animal health, helps preserve antimicrobial efficacy and contributes to sustainable disease management.

Practical Clinical Insights

Successful antimicrobial therapy for Glässer's disease begins with early diagnosis and prompt intervention. Whenever possible, collect diagnostic samples before initiating treatment and request bacterial isolation with MIC testing to guide antimicrobial selection. Treatment decisions should always be interpreted alongside herd history, clinical presentation and susceptibility results rather than relying solely on empirical therapy. Combining responsible antimicrobial use with improved management and preventive measures provides the most effective approach to controlling Glässer's disease while supporting antimicrobial stewardship.

References

Costa-Hurtado M, Barba-Vidal E, Maldonado J, Aragon V. Update on Glässer’s disease: How to control the disease under restrictive use of antimicrobials. Veterinary microbiology. 2020 Mar 1;242:108595. https://www.sciencedirect.com/science/article/pii/S0378113519314713