Paratuberculosis control: a review with a focus on vaccination

Abstract

Mycobacterium avium subsp. paratuberculosis (MAP) infection causes in ruminants a regional chronic enteritis that is increasingly being recognized as a significant problem affecting animal health, farming and the food industry due to the high prevalence of the disease and to recent research data strengthening the link between the pathogen and human inflammatory bowel disease (IBD). Control of the infection through hygiene-management measures and test and culling of positive animals has to date not produced the expected results and thus a new focus on vaccination against this pathogen is necessary. This review summarizes all vaccination studies of cattle, sheep or goats reporting production, epidemiological or pathogenetic effects of vaccination published before January 2010 and that provide data amenable to statistical analyses. The meta analysis run on the selected data, allowed us to conclude that most studies included in this review reported that vaccination against MAP is a valuable tool in reducing microbial contamination risks of this pathogen and reducing or delaying production losses and pathogenetic effects but also that it did not fully prevent infection. However, the majority of MAP vaccines were very similar and rudimentary and thus there is room for improvement in vaccine types and formulations.

Figure 1

Immunopathological model of paratuberculosis. Continuous exposure of animals to MAP results in a dynamic balance where infection never gets established or is controlled by an efficient innate immune response in about half of the farm population, while in the other half it progresses to subclinical delimited focal or multifocal forms and, in a smaller fraction, to diffuse lymphocytic (cellular or Th1 type) or non-lymphocytic (humoral or Th2 type) forms that will result in open clinical disease.

Figure 2

Types of MAP vaccination experiments used in the meta-analysis. Graphic representation of MAP vaccination experiments grouped by outcome according to animal species and category (production, epidemiological or pathogenetic effects). Experiments with a negative outcome: bars on the left part of the chart; experiments with a positive outcome: bars on the right hand of the chart. Numbers adjacent to the bars correspond to the number of experiments. *One experiment has a 0% reduction.