Haemophilus parasuis
Is It There Or Not?
Bac-T labs sometimes have problems finding Haemophilus parasuis (H. parasuis) by traditional bacteriology methods in samples from herds where the vet believes H. parasuis may be the causative agent. New methodology available from the University of Montreal in combination with traditional Bac-T may help to address this problem.
Isolating versus Identifying
It is not always possible to isolate H. parasuis from tissues of piglets dying of this infection because of its fastidious nature. That being said, carefully chosen and prepared samples really help with this issue. We suggest samples from untreated, euthanized animals that were showing disease symptoms. The full pluck (heart and lungs), spleen tissue and brain or spinal column swabs all can be productive samples. Careful packaging and rapid shipment are also important.
As well, the University of Montreal has developed two tests to assist with diagnosis. The first test is a monoclonal antibody based coagglutination test for detecting H. parasuis specific antigen directly in the tissues such as spleen, lungs and heart. They are satisfied with the results obtained regarding sensitivity and specificity. In most cases, spleen was found to be the most suitable organ for detecting the antigen.
The second option is detection by PCR. This test can also be coupled with identification of S. suis infection. Suggested samples include heart tissue and joint and brain swabs.
Of course, neither of these tests results in a culture for production of an autogenous bacterin, nor do they provide a serotype determination. However, they may aide in the development of a diagnosis.
If you would like to try either of these methods as a follow up to Bac-T, tissue samples such as spleen, heart and lung sent to us could be split upon arrival and a sub-sample frozen to be sent for further testing upon your request, if the bacteriology is negative for H. parasuis.
Does the breeding herd show a high titre to H. parasuis suggesting a latent reservoir?
OR
Do the surviving pigs from a barn that had losses believed to be caused by H. parasuis show a titre, suggesting exposure?
University of Montreal now has a serological test developed to detect antibodies against H. parasuis. The test is based on detection of species-specific antibodies using ELISA and a monoclonal antibody based Western-blot assay (Dot-ELISA). These tests are highly specific and sensitive. A minimum of 10 sera samples is required to carry out the serology.
Are Isolates of H. parasuis Genetically Identical?
This can be an important question when trying to trace disease origin or decide upon isolates to be included in an autogenous bacterin. The answer may be provided by a fourth molecular based technique. The test is called ERIC-PCR and it characterizes the genetic diversity of H. parasuis isolates if you require greater detail than that provided by the standard serotyping test.
H. parasuis Bacterins
Autogenous H. parasuis bacterins are being used to vaccinate both the breeding herd and weaned pigs and provide an alternative approach to control of disease symptoms and production losses caused by this organism. However, success depends on finding and characterizing the significant serotypes. We have 10 years of experience working with H. parasuis and can help with sampling plans for isolating and characterizing H. parasuis strains.
*Information regarding the tests available from the University of Montreal has been kindly provided by Dr. Mittal.