Glasserella parasuis: The Causal Agent of Glasser's Disease
Publish Date: 05/05/2022
Glässer’s disease is an important cause of post-weaning morbidity and mortality in swine populations worldwide. The disease was first described in 1910, but the etiological agent was not isolated until 1922. It is a gram-negative bacterium Glaesserella parasuis (G. parasuis), formerly known as Haemophilus parasuis, that belongs to the Pasteurellaceae family (Dickerman et al., 2019). G. parasuis is part of the normal microbiota of pigs and is an early colonizer of piglets. The bacterium can be detected in the trachea, nasal passages or tonsils of piglets as early as two days after birth. Pigs can be colonized by both virulent and non-virulent strains. Although it is normally found in the upper respiratory tract (URT) of pigs, upon disruption of pig’s immune system, it causes Glässer’s disease. The disease is normally observed in 4 through 8-week-old pigs (nursery pigs) but it can sporadically occur in older pigs (Aragon et al., 2019). Weaned piglets are more susceptible because of waning maternal antibodies. Proper diagnosis and typing of isolates is crucial to understand the molecular epidemiology of strains involved and to design better herd-specific autogenous vaccines to control the disease. Knowledge of the circulating strains within or between farms is crucial. Traditionally, serotyping has been the most common typing method, with 15 known serotypes (Kielstein and Rapp-Gabrielson, 1992).