Prevalence of anti-red blood cel antibodies in the serum and colostrum of mares and its relationship to neonatal isoerythrolysis.

The study investigated the occurrence of antibodies against red blood cells in pregnant Standardbred and Thoroughbred horse breeds and their association with the condition known as neonatal isoerythrolysis in their foals.

Research Objectives

The study set out to:

• Investigate the prevalence of anti-red blood cell (RBC) antibodies in the blood serum of two breeds of pregnant mares; Standardbreds and Thoroughbreds.
• Determine the kind of blood-group antigens these anti-RBC antibodies are specific to.
• Analyze the relationship between the presence of these antibodies in the mare’s serum and colostrum.
• Explore the potential risk of neonatal isoerythrolysis in foals if the mares have these antibodies in their serum and colostrum.

Methodology and Findings

The sudy found that:

• The sera of a total of 799 pregnant mares were tested, with 20% of the Standardbred mares and 10% of the Thoroughbred mares showing detectable anti-RBC antibodies through hemolytic or saline agglutination tests.
• Most of these antibodies were specific to the CA blood-group antigen of horses, while others were specific to other blood-group antigens such as Aa, Ab, Da, Df, Ka, Ua, or Qa.
• In the 268 mares where both serum and colostrum samples were compared, it was found that anti-RBC antibodies were present in both the serum and colostrum, with only 3 exceptions.

Implications and Conclusion

The study’s findings revealed that:

• In cases where mares had antibodies reactive at serum dilutions of 1:16 or greater to the specific blood-group antigens Aa or Qa, the colostrum was withheld from their respective foals and this step proved beneficial.
• As per the results of the study, a foal that inadvertently received colostrum containing anti-Aa antibodies developed neonatal isoerythrolysis – a potentially life-threatening blood disorder.
• However, the researchers observed that the other foals, who were allowed to nurse from their mares, didn’t develop neonatal isoerythrolysis even when anti-RBC antibodies were detected for blood-group antigens other than Aa and Qa which in theory, could react with the foals’ RBCs.
• This implies that the potential risk for neonatal isoerythrolysis in foals seems to be significantly related to anti-RBC antibodies specific to the Aa or Qa blood-group antigens, and less correlated with other detected antigens.