The immune response of horses to tetanus toxoid.

The study indicates that horses can be adequately protected from tetanus for extended periods of time through the use of tetanus toxoid injections. Adult horses, after receiving initial and then booster doses of the toxoid, were shielded against tetanus for approximately 128 weeks and an additional 3.5 years, respectively. Foals acquired initial immunity from colostrum for about ten weeks, but direct toxoid injections proved ineffective until a certain age and development level was reached.

Methodology

• The research involved administering an intramuscular injection of 8-16 Lf tetanus toxoid (in a water-in-oil emulsion) to adult horses.
• The performance of the injectable tetanus toxoid was evaluated over a period of 128 weeks to establish its protective duration against tetanus.
• Furthermore, a booster dose of 8 Lf toxoid in an aqueous solution was provided to the same cohort of horses to determine the length of protection extension it could offer.

Findings in Adult Horses

• The initial tetanus toxoid injection proved successful, effectively protecting the horses from tetanus for a minimum of 128 weeks.
• The booster dose extended this protective period by at least another 3.5 years, proving the efficacy of the intervention.

Colostral Immunity in Foals

• The research also delved into the natural defenses granted to foals through colostral immunity, which maintained fortification against tetanus for approximately 10 weeks.

Ineffectiveness of Tetanus Toxoid on Young Foals

• The study revealed that the tetanus toxoid was ineffective on foals born to immune dams between 10-18 weeks of age.
• These foals showed no antibody response to the toxoid, indicating the inefficacy of the treatment within their age group.

Successful Intervention after Certain Development Stage

• In contrast to the above finding, 12 weeks after the first ineffective dose, a booster injection of the toxoid in an aqueous solution triggered an antibody response in the previously non-responsive foals.
• This suggests that the development or aging of the foals may contribute to their ability to successfully respond to the tetanus toxoid.

Unresponsiveness of New-born Foals

• Interestingly, the research found that new-born foals are inherently unresponsive to tetanus toxoid injections.
• The reason behind this apparent immunity or lack of response needs further exploration.