Temporal detection of Lawsonia intracellularis using serology and real-time PCR in Thoroughbred horses residing on a farm endemic for equine proliferative enteropathy.

This study examined antibodies levels against Lawsonia intracellularis, a bacteria causing equine proliferative enteropathy (EPE), in broodmares and their foals on a farm known for EPE occurrence. The research showed that mares were regularly exposed to L. intracellularis and that they passed these antibodies to their offspring. However, despite this exposure, none of the foals exhibited EPE symptoms.

Introduction to the Research

• This study aimed to review L. intracellularis antibody levels in 68 broodmares from an EPE endemic farm and to assess maternal antibodies, seroconversion (the time period during which a specific antibody develops and becomes detectable in the blood), and fecal shedding in their foals.
• It involved collection and testing of serum samples from the mares and foals at different stages of birth and growth, and feces tests for L. intracellularis using real-time PCR.

Findings of the Study

• At the time of foaling, about 54.4% (37) of the mares had noticeable antibody titers against L. intracellularis. Antibody titer is the concentration of an antibody, as determined by finding the highest dilution at which it can still cause agglutination of the antigen.
• Passive transfer of L. intracellularis antibodies was documented in 37 foals, indicating that receiving antibodies from the mother’s milk is one of the ways these foals raised their defenses against the bacterial infection.
• The colostral antibodies (antibodies found in a mother’s milk) remained detectable in foals’ serum for 1 to 3 months.
• Overall, 22 foals showed indications of natural exposure to L. intracellularis throughout the study period. A natural exposure means the infection was not artificially induced, but happened due to the environment they were in or the contact they had with infected individuals.
• Despite the documented exposure, no foals developed signs consistent with EPE, which is a significant finding and warrants further research to understand why these foals do not develop the disease.

Conclusion of the Study

• The serological results provided evidence that mares on a farm with EPE endemic are consistently exposed to L. intracellularis.
• More importantly, it established that antibodies against L. intracellularis are passively transferred from mothers to foals, providing them some level of protection.
• The research, however, leaves some unanswered questions, particularly the mechanism that prevents the foals from developing EPE symptoms even after exposure to the bacteria.