Familial and herd-level associations with paratuberculosis enzyme-linked immunosorbent assay status in beef cattle

Prevalence of bovine paratuberculosis in Chinese cattle populations: a meta-analysis

Background

Bovine paratuberculosis is a chronic infectious disease of ruminants primarily caused by Mycobacterium avium subsp. paratuberculosis (MAP). It is essentially a chronic granulomatous enteritis characterized by intractable diarrhea, progressive lethargy, and thickening of the intestinal mucosa with the formation of crumpled pouches. Bovine paratuberculosis not only adversely affects milk production and the quality of dairy products but also poses a significant threat to the economic development of dairy farming and human food security. This systematic review and meta-analysis was conducted to assess the prevalence of MAP infection among cattle herds in mainland China.

Results

A total of 62 studies with data from 102,340 cattle in 24 provinces in China were selected after matching the assessment criteria. In China, the overall estimated prevalence of MAP infection in cattle was 8%(7727/102340). Interestingly, the MAP infection rate in cattle in southern China was estimated to be 2% (6/281), which was significantly lower compared with other regions of China, and the highest infection rate was 12% (1914/16008) in eastern China. MAP infection rates were related to age, average herd size, type of use, season, detection method, and sample type. Moreover, the MAP infection rate in cattle did not correlate with the publication date of the studies.

Conclusion

The analysis identified age, average herd size, type of use, and season as significant potential risk factors associated with PTB pool positivity. In addition, the detection method and sample type can also potentially affect the incidence of detected PTB.

Control of paratuberculosis in beef cattle

As with any susceptible livestock species, the key to control of paratuberculosis in beef cattle is to reduce exposure of the susceptible calves to Mycobacterium avium subsp. paratuberculosis (MAP)–contaminated feces. Because beef calves remain with mature, potentially shedding cattle until weaning, control strategies are aimed at providing an environment with the least possible fecal burden and removing MAP shedders as soon as possible. Testing and culling or separation may be more important in beef cattle than in dairy cattle. Seedstock owners have greater potential for economic loss from paratuberculosis, making control program more financially attractive to them than to commercial beef cattle producers.

Immunogenicity and reactivity of novel Mycobacterium avium subsp. paratuberculosis PPE MAP1152 and conserved MAP1156 proteins with sera from experimentally and naturally infected animals

Mycobacterium avium subsp. paratuberculosis causes Johne's disease (JD) in ruminants. Development of genetic tools and completion of the M. avium subsp. paratuberculosis genome sequencing project have expanded the opportunities for antigen discovery. In this study, we determined the seroreactivities of two proteins encoded at the 5' and 3' regions of the MAP1152-MAP1156 gene cluster. MAP1152 encodes a PPE protein, and MAP1156 encodes a diacylglycerol acyltransferase involved in triglyceride metabolism and classified in the uncharacterized protein family UPF0089. Recombinant MAP proteins were overproduced and purified from Escherichia coli as maltose-binding protein (MBP) fusions. Immunoblotting analysis indicated that both MAP1152 and MAP1156 displayed reactivity against sera of mice and rabbits immunized with live M. avium subsp. paratuberculosis cells and against samples from naturally infected cattle. In immunoblot assays, MAP1156 yielded a stronger positive signal than MAP1152 against sera from cattle with JD. An enzyme-linked immunosorbent assay for the recombinant proteins was developed and used to test preclassified positive and negative serum samples from naturally infected and noninfected cattle. Samples, with one exception, displayed no seroreactivity against the MBP-LacZ fusion protein (P > 0.05), the negative-control antigen. MAP1152 displayed seroreactivity against all positive sera but no seroreactivity to the negative sera (P < 0.01). MAP1156 displayed stronger and more variable reactivity than MAP1152, but significant differences were observed between noninfected and infected cattle (P < 0.05). Otherwise, degrees of reactivity followed the same trend as the positive reference antigen. In conclusion, both proteins are immunogenic in mice and rabbits, and M. avium subsp. paratuberculosis-infected cattle mount a humoral response to both MAP1152 and MAP1156 cross-reactive epitopes. These findings have potential applications to diagnostics, vaccine production, and elucidation of the immunopathogenesis of JD.