Glaesserella (Haemophilus) parasuis, is the bacterial cause of fibrinous polyserositis that we refer to as Glässer’s disease. This common bacteria is normally an early colonizer of the nasal cavity in piglets. Piglets are initially colonized with the strains that are shed by the sow and their littermates. At weaning, the growing pig can be exposed to an even wider variety of strains that come from other pen mates or the nursery environment itself. The spectrum of strains of Glaesserella parasuis is quite diverse and ranges from relatively non-pathogenic strains that are primarily commensal organisms that colonize the pigs respiratory track. More pathogenic strains possess additional virulence factors that allow them to colonize and then further invade multiple body systems. These pesky strains get up to a lot more mischief and the cost of lost of productivity and death in nonimmune pigs can be quite high.
Fortunately, the pig has a very elegant strategy with it’s immune system that allows for early exposure to these problem bacteria while they are still protected by an “umbrella” of maternally derived colostral immunity. While still under this umbrella of maternal protection the piglet’s immune system matures and responds to the organism by producing it own antibodies and cellular immunity. Without the passive protection provided by sow colostrum a first encounter with a more virulent strain of Glasser’s can be like getting hit by a Mac Truck. No time to react and sudden nasty consequences. Unfortunately, not all sows have been exposed to all of the strains that exist with a pig flow. In order to even out the broadness of G. parasuis coverage sows can be vaccinated prior to farrowing with a variety strains so that the passive protection can cover off on strains that the sow has never actually been exposed to.
These Spanish researchers wanted to do a deep dive on how this passive protection offered by colostral immunity actually works. Sow vaccination was performed with a protein fragment, F4, from the outer membrane trimeric autotransporters VtaAs that is exclusively found in virulent G. parasuis. Piglets were allowed to suckle for 3 weeks (including colostrum), following which a challenge with one of two virulent strains of G. parasuis was performed. A group of nonvaccinated sows and their piglets were included as a control.
The researchers found the following:
- Antibodies against F4 were confirmed using ELISA in the vaccinated sows and their offspring before the G. parasuis challenge.
- After the challenge, a lower body temperature and a higher weight were observed in the group of piglets from vaccinated sows.
- Only 1 piglet from the non-vaccinated control group died due the G parasuis infection challenge. In this study there were no other statistically significant differences in clinical signs.
- At necropsy, performed 2 weeks after the virulent challenge, the level of surfactant protein D (SP-D) in bronchoalveolar lavage fluid was higher in the piglets from vaccinated sows.
- Prefarrowing vaccination of the sow did not inhibit the nasal colonization of the piglets by the challenge strains.
Take Home Messages:
- Piglets that came from vaccinated sows were heavier at the end of the study.
- The antibodies produced by this very specific subunit vaccine could be detected in high levels in bronchoalveolar lavage fluid from the respiratory system of the growing pig. This places the antibodies in a location where can meet ant invading bacteria. Right where the rubber meets the road!
- Even with all of this improved immunity that protects against disease the piglets were still colonized with the bacteria. This is important, in that passive protection does not last forever and the growing pig needs to be exposed to the bacteria if it is to develop it’s own active immunity.
- This study supports the use of prefarrowing vaccination of the sow in order to provide passive protection to the growing pig until it’s own immune system can kick into gear and mount its own immune response.
Reference: Sergi López-Serrano , Carlos Neila-Ibáñez , Mar Costa-Hurtado , Yasser Mahmmod , Jorge Martínez-Martínez , Iván José Galindo-Cardiel, Ayub Darji , Fernando Rodríguez , Marina Sibila , Virginia Aragon Sow Vaccination with a Protein Fragment against Virulent Glaesserella (Haemophilus) parasuis Modulates Immunity Traits in Their Offspring Vaccines (Basel) . 2021 May 20;9(5):534. doi: 10.3390/vaccines9050534.
