Duration of Tetanus IgG Titres Following Basic Immunisation of Horses

Abstract

Reasons for performing studyRecommendations for prophylactic vaccination against tetanus in horses vary greatly between countries and have scarce scientific support in the peer‐reviewed literature. In human medicine, recommended booster vaccination intervals are also very variable, but are considerably longer than for horses.ObjectivesTo investigate if the duration of antibody titres previously determined to be protective against tetanus are likely to be longer than indicated by several recommended vaccination intervals for horses.Study designProspective clinical trial.MethodsThirty‐four horses were enrolled for basic immunisation with an ISCOM Matrix‐combination vaccine (Equilis® Prequenza TE). Horses received the first vaccination at 5–11 months of age, and the second dose 4 weeks later. A third vaccine dose was given 15–17 months after the second dose. Serum tetanus antibody titres were analysed by ToBi ELISA 2 weeks as well as 14–16 months after the second dose. After the third vaccine dose, titres were checked once yearly for 3 years.ResultsTwo weeks after the second dose all horses (34/34) had antibody levels that exceeded 0.03 iu/ml. After 16 months the levels were below 0.03 iu/ml in 5/33 horses. After the third vaccine dose antibody levels remained above 0.03 iu/ml in 25/26 horses for 1 year, 17/17 horses for 2 years, and 9/9 horses for 3 years.ConclusionsHorses that undergo basic immunisation with 3 doses of vaccine after the age of 6 months are likely to have serum antibody titres consistent with protection against tetanus for more than 3 years.Ethical animal research: This study was approved by the Uppsala Ethical Committee on Animal Experiments and informed owner's consent was obtained prior to enrolment of horses. Sources of funding: This study was funded by the Intervet Research Foundation. Competing interests: None.