by Poulpharm

Practical advice to reduce Glässer’s disease impact

Glaesserella parasuis has a high genetic variability and can generate complex co-infections. This article describes some practical steps to reduce Glässer’s disease impact.

Glaesserella (Haemophilus) parasuis is responsible for Glässer’s disease and it remains a key pathogen in the swine health landscape, particularly around weaning and other stress-related periods. Although commonly present in the upper respiratory tract, disease arises when virulent strains coincide with stress or co-infections.

Why it still matters?

Clinically, G. parasuis infection leads to fever, lameness, dyspnea, and neurological signs, often accompanied by fibrinous polyserositis and arthritis. These lesions contribute to mortality and impaired performance.
While G. parasuis is part of the normal upper respiratory flora, it behaves opportunistically, with disease frequently triggered by stress events such as weaning, transport, or mixing. Co-infections with PRRSV, SIV, Mycoplasma hyopneumoniae, or Streptococcus suis further increase disease risk.
Incidence peaks around weaning, when piglets experience waning maternal immunity and heightened environmental or infectious stressors.

The diversity challenge

A major challenge with G. parasuis is its genetic diversity. Numerous serotypes and non-typeable strains circulate in the field, with distributions that can shift over time. Genetic variability among isolates, particularly in capsular types and virulence-associated genes, limits cross-protection when field strains differ from vaccine components. In some cases, more than one serotype or genetic variant can be present within the same herd or even within a single animal, further complicating diagnosis and prevention. Each production system tends to harbor its own local or regional strain profile, making the disease dynamics and outcomes highly site-specific.

The diagnostic challenge

Sample smart:

• Prioritize very fresh, clinically affected (untreated) piglets.
• Collect fibrin or serosal swabs, meninges, and joint material.
• Ensure rapid refrigerated transport.
• G. parasuis is highly sensitive to temperature changes, making sample freshness and rapid transport critical for successful culture and detection.

Laboratory workflow:

• Culture and in parallel PCR confirmation.
• Serotyping via PCR or sequencing (NGS).
• NGS can also detect virulence markers and support vaccine/autovaccine strain selection.

Interpretation in context:

• Always integrate strain data with age, movement, and stressor information to better understand disease dynamics.