Investigation into the practice of vaccination in equine livestock in Germany

Abstract

The availability of vaccines and horse vaccinations should fulfill the targets for effective immune prophylaxis. These consist in individual prevention of clinical manifestation, immunological neutralization of the pathogens used in the vaccine with stop of their replication and shedding out of the immunized horse. With guarantee of this fundamental requirements for effective vaccination and with a synchronized vaccination program of the actual stock an epidemiological contribution can be made by means of interruption of the infection chain. This is possible with vaccines against influenza viruses to some extent, it is not possible with vaccines against the equine herpes viruses. For tetanus and rabies other epidemiological prerequisites apply. For the optimal use of vaccines the following premisses have to be considered: age of the young horse at the time of the first vaccination (priming), different immunogenity and immunoinduction of the antigens administered, their capability of protection as well as the duration of postvaccinal, protective immunity, timing of revaccination, appropriate vaccination antigens for this and so on. Proven scientific conditions exist for these determinating factors of successful vaccination, which should be found in recent corresponding prescript information and beyond that in statements about vaccination in so called guidelines for vaccination, which is not the case currently. Institutions responsible and acting on behalf of this issues - e.g. science, producers of vaccines, registering authorities, permanent commissions on vaccination, German association for Equine medicine-should exercise remarkably more influence to recognition of the above mentioned factors and their recent internationally scientifically proven basics as a means to optimize the current situation. Equine passports of 151 horses, out of three different populations (D, M, K) with a total of 1495 documented vaccinations were evaluated with regard to verification of the fundamental requirements mentioned above for a successful vaccination on the basis the vaccines applied. These were vaccines against tetanus, influenza and equine herpes viruses, rabies, dermatophytes. The evaluation was based on the following criteria: age of the horses at the beginning of the priming vaccination (Gl) and the following vaccinations (G2, G3) vaccines used for these; age of the horses at the revaccinations W1 to W10, vaccines used for these; accines and their antigens, tetanus toxoid, influenza H7|N7, H3|N8, Equine herpes viruses EHV1, EHV4, dermatophytes, rabies and their kind of use; differences between three groups of horses; frequency of the different antigens applied with regard to the total number of 1495 vaccinations; analyses of all vaccinations with regard to the application of EHV-antigens. The different influence of the veterinarians was shown within the different groups of horses looked at it with regard of vaccinations applied referring to the criteria mentioned above. Furthermore - as a consequence of prescriptions and guidelines not corresponding to the current state of scientific knowledge - applications of tetanus vaccines occurred too frequently and vaccinations against EHV not justified occurred of all ages and use. These results will be discussed in the light of the controversial situation: current state of science versus vaccination practice and the problems resulting for the vaccinating veterinarians. This especially applies for EHV vaccines and their lacking efficiency, individually and epidemiologically. Overvaccination without indication with these vaccines is shown in the population looked at, 65% of all revaccinations were done with inactivated combined EHV1/EHV4 vaccines, modified live attenuated EHV1 vaccine was used only in 2% of the vaccinations and only for revaccinations. Vaccinations against influenza viruses were mainly applied according to the directives of the German Equestrian Federation (LPO), although remarkable differences between the different horse groups exist especially for basic vaccinations. It will be pointed out, that for optimization of prophylaxis against influenza virus infection both, improved internationally standardized diagnostics to test the immune status of horses and their virus shedding and the improvement of the current vaccines, which only induce a haemaglutinin associated, strain specific H31N8 immune response, is necessary. The vaccinations against rabies, even though only applied in a small percentage of foals in the disease free Germany is not indicated, neither is the vaccination against dermatophytes, which occurred in 2% of the healthy young horses of the investigated population.