Title INVITED SPEAKER: Control of paratuberculosis by vaccination
Author(s) Juste RA*, Geijo MV, Sevilla I, Aduriz G, Garrido JM.
Institution(s) NEIKER (Instituto Vasco de Investigación y Desarrollo Agrario), Dpto. de Sanidad Animal. Berreaga 1, 48160 Derio. Bizkaia. Spain.
Source Seventh International Colloquium on Paratuberculosis
Section 7: Epidemiology and Control
Abstract
Control of paratuberculosis is a very complex issue that has prompted many different approaches. Vaccination is an old control method for paratuberculosis which has been used worlwide, but that has won rather little recognition. Its use on cattle in France by Valleé and Rinjard in the early years of the 20th century reportedly was very successful. In sheep, the epidemic of paratuberculosis in Iceland prompted the development of a vaccine that according to Sigurdson in 1957 led to total disappearance of clinical cases. In the sixties, the Moredun group carried out a series of experiments on sheep that laid the grounds for all subsequent knowledge on paratuberculosis vaccine performance. Later on, work on goats in Norway again proved vaccination to be a highly efficient practical control method. There are no reports on vaccine failure, except one referring to unconventional administration (oral), another of reduced efficacy due to vaccine composition (sonicated cells), and a recent one reporting no effects on fecal shedding compared to other control measures. In addition to the technical aspects of vaccination, it should be born in mind that paratuberculosis has been considered largely as an economic problem. In this sense, vaccination has proven to be a highly advantageous strategy over other control approaches that are more difficult to evaluate. Although vaccination is generally applied to 2-4 weeks old animals, the disease progression being very slow, it is now clear that, at least in sheep, vaccination can modify the immunopathogenesis of paratuberculosis and stop the progression from early subclinical infection to open disease. In spite of all this evidence vaccination is not widely accepted as a choice for paratuberculosis control. One reason is that there is a self-injection risk for practitioners. The risk of some minor local damage was around 1/4000 doses in one study. Other complaint about vaccination is that it can interfere with tuberculosis diagnosis. Although this can be circumvented by the comparative tuberculin testing, it might still represent a commercial concern where avian reactions are rare and commercial considerations make any tuberculin reaction undesirable. Both problems might be overcome with improved vaccines. However, the main drawback for vaccination is that it does not completely protects from infection, and therefore that by itself cannot lead to Map eradication. This point has become even more important since more evidence has been produced on the human exposure Map as a potential risk for Crohn's disease. The most recent evidence on the dimensions of Map spread in wildlife and clinically healthy herds, as well as failures to eradicate the infection and evident difficulties to widely implement other measures, open a way for vaccine use re-assesment as a readily available means for limiting paratuberculosis transmission and economic costs. In conclusion, vaccination is not as clean as test and cull strategies, but can advantageously compete with it in implementation and economic readiness. Depending on the species, epidemiological circumstances and socio-economic constraints it could be the only difference between doing nothing and beginning to win the war against paratuberculosis.

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