Antibodies in horses, mules and donkeys following monovalent vaccination against African horse sickness.

The research article evaluates the effect of a monovalent African horse sickness virus vaccine on three types of domesticated equids (horses, mules, and donkeys) in Spain and notes that a small percentage did not develop detectable antibodies; however, this may not imply complete lack of protection.

Research Context & Methodology

• The study was carried out in Spain on domesticated equidae, which includes horses, mules, and donkeys, to observe their immunological response to the monovalent serotype 4 African horse sickness virus (AHSV) vaccine.
• A total of 256 serum samples were collected from these species within 1-4 months after vaccination. The vaccine used was attenuated, meaning it contained live virus that had been weakened to prevent causing disease but still elicit an immune response.
• The serum samples were then tested using ELISA (Enzyme-Linked Immunosorbent Assay), virus neutralization, agar gel immuno-diffusion, and complement fixation tests to check for the presence of antibodies against AHSV.

Research Findings

• About 10% of the serum samples did not exhibit detectable antibodies to the AHSV, a result that was observed across all four testing techniques. These horses were seemingly unresponsive to the vaccination.
• The research also noted similar negative reactions in sera from two ponies following a first vaccine dose.
• In these two ponies, a rapid increase in antibodies was observed following a second vaccine dose, implying that they may have developed immunity despite the initial lack of detectable antibodies.

Research Implications

• The findings suggest that the absence of detectable antibodies after primary vaccination does not necessarily indicate a lack of protection against the African horse sickness virus. This may be due to the “silence” of the immune system during its initial encounter with the vaccine, which could have subsequently activated upon receiving the second dose.
• This leads to the implication that immunization procedures might need to consider additional doses or boosters in order to assure a noticeably stronger immune response in such cases.