Experimental investigations to the immune response of foals and adult horses to tetanus toxoid using the Fassisi TetaCheck®

Mistakes within vaccinating of horses are common and mainly based on misinstructions by the pharmaceutical companies as well as on limited knowledge of the practitioners. This concerns the vaccination against tetanus especially in foals, but also in adult horses. As a contribution to the immune response to tetanus toxoid we tested the transfer of post vaccination antibodies from vaccinated mares to their sukkling foals. 100% of the investigated 24 mares and their foals showed immediate transfer of colostral globulins into the foals within the investigated time frame from 10 hours to five days p.n..In all the investigations we used the horse side test "Fassisi TetaCheck((R))". In repeated investigations on 69 weaned foals we could demonstrate that the colostral tetanus antibodies persisted at least till 8,5 month p.n.. In 45% of the investigated foals maternal antibodies were present till mid of the 7th month of their live. The registered titers were in the immunprotective range between 0,1 and 1 i.E./ml serum. In order to investigate the influence of this maternally derived antibodies to the tetanus vaccination we immunized 24 foals, at age from 6 to 8 month, 50% with and 50% without antibodies. Two shots, 8 weeks apart (GI and GII) of a monovalent tetanus toxoid vaccine were given. The seropositive foals responded serologically clearly reduced to GI in comparison to the seronegative foals. This was not related to the different age of the weanlings in both groups. In 4 of the strong positive vaccinates at the time of GI we could observe an elimination of the maternal antibodies despite GI. In contrast, 100% of seronegative foals had responded with seroconversion to GI. 4 weeks past GII all foals under investigation reacted with immunprotective levels of antibodies. In another trial we investigated the half life time of antitoxin titers in 8 horses at age from 8 to 21 years. These horses had the last tetanus vaccination between 4 to 11 years ago. All of them responded with immunprotective levels of antibodies. One 25 years old mare that never had been vaccinated against tetanus toxoid reacted negative. This confirms the half life time of 8 to 15 years in horses - same as in human beings. The described results of our investigations in foals as well as in adult horses should stimulate to reflect on the practised vaccination programmes using tetanus vaccines: First vaccinations too early in the foals' life, time between GI and GII too short, too many vaccinations and redundant vaccinations in completely immune protected horses. The last point of our investigation was the question of clinically inapparent infections and the possibly resulting immune response. For this reason we investigated 10 donkeys out of a herd of 35 animals - never in their life vaccinated against anything. 2 of the 10 donkeys clearly responded positive in a double investigation 11 weeks later. We value this result as the consequence of an inapparent exposition with Clostridium tetani and the hereby stimulated humoral response. Anamnestic inquiries to the 2 donkeys concerning injuries etc. were negative. At last, recommendations and possibilities for improvement and new indications for the Fassisi TetaCheck((R)) were elaborated.