Evaluation of a series of testing procedures to predict neonatal isoerythrolysis in the foal.

This research article investigates a range of modified field tests to predict whether foals could be at risk of neonatal isoerythrolysis (NI), using blood and colostrum from their mares. The study, based on eight foals born to experimentally alloimmunized mares, found mare’s serum combined with the foal’s erythrocytes was the most reliable predictor of impending NI compared to other field tests.

Objective of the Study

• The research aims to compare a series of modified field tests with a standard crossmatch (a lab blood test between mare and foal) in order to better predict neonatal isoerythrolysis (NI), a serious foal blood disorder, in newborn horses.

Methodology

• The study involved eight foals born to mares that had been alloimmunized or purposely exposed to foreign blood to produce an immune response.
• During the tests, different combinations of mare’s serum (the liquid fraction of whole blood), plasma, and colostrum (the first form of milk produced by the mammary glands of pregnant mares) were combined with washed erythrocytes (red blood cells) from the foal.
• The aim was to determine the combination that best predicts impending NI by looking at the reaction these combinations caused.
• A consistent system for grading the reactions – agglutination (clumping of cells) and hemolysis (rupturing of red blood cells), was used.

Findings

• The study found that the field tests using mare’s plasma showed less agglutination and hemolysis than tests with serum, making plasma a less accurate predictor of NI.
• Immediate assessment of agglutination did not demonstrate agglutinin (antibodies causing clumping) activity compared to tests allowing an incubation period.
• Rouleaux formation – a clustering of red blood cells which stick together – poses a challenge in interpreting minor agglutination.
• The grading of hemolysis was deemed easier, quicker, and more accurate than assessing agglutination.
• The most reliable field test was the combination of mare’s serum and foal’s erythrocytes, when compared with the standard crossmatch and presuckle anti-foal erythrocyte titers (levels of antibodies against foal erythrocytes in the mare’s blood before the foal nurses for the first time).
• The tests detecting hemolysin (molecules leading to the rupture of red blood cells) in serum and colostrum, which used rabbit sera as a complement source, were also deemed reliable.