[An evaluation of the direct agglutination test for the diagnosis of “mal de caderas” in horses].

The research is about evaluating the efficacy of a Direct Agglutination (DA) test in diagnosing a disease in horses known as “Mal de Caderas”, which is caused by the T. evansi infection, and assessing the nature of the antibodies involved in its detection.

Background & Purpose of the Study

• The main aim of this study was to assess the effectiveness of the Direct Agglutination (DA) test as a means to diagnose “Mal de Caderas”, a disease caused by the T. evansi infection in horses.
• The researchers also sought to understand the nature of the antibodies that react to the disease.

Materials & Methods

• The researchers used 44 serum samples from two lots of horses naturally infected with T. evansi.
• In cases where parasites were isolated, the researchers conducted the DA test to observe the agglutination titres, which indicate the concentration of antibodies in the blood.
• Sera that tested positive in the DA test were treated with 2-mercaptoethanol, which assisted in identifying the IgM nature of the antibodies involved in the detection of T. evansi.
• Naganol (Bayer-Germany) was administered to 5 T. evansi infected horses to treat the disease and observe the effects on antibody levels.
• A control group of 50 horses free from T. evansi were also tested for comparison.

Results

• Among the 16 horses in which parasites were isolated, 13 (81.2%) provided positive agglutination titres in the DA test. It pinpointed high concentrations of antibodies effective in fighting T. evansi.
• Treatment with 2-mercaptoethanol reduced the agglutination titres in 12 samples, confirming the IgM nature of the antibodies, which is an early immune response.
• In 17 out of 28 horses, the DA test was positive even when no parasites were detected, suggesting that the body’s immune response had already begun.
• Post treatment with Naganol, IgM antibodies were not detectable after two months, but IgG antibodies (long-term immunity) were detectable, albeit at lower concentration, in three of the five horses, even 12 months later.
• All horses in the control group tested negative in the DA test, confirming the test’s specificity to T. evansi.

Conclusion

• The researchers concluded that the DA and DA+2-ME tests are reliable for diagnosing “Mal de Caderas” in horses when used in combination with parasitological diagnostic methods.
• They also found that the body’s immune response to T. evansi infection involved initially high levels of IgM antibodies, transitioning to IgG antibodies over time.