Global rates of Crohn's disease

Comparison of a mycobacterial phage assay to detect viable Mycobacterium avium subspecies paratuberculosis with standard diagnostic modalities in cattle with naturally infected Johne disease

Background

Mycobacterium avium subspecies paratuberculosis (MAP), the cause of Johne disease, is a slow growing mycobacterium. Viable MAP detection is difficult, inconstant and time-consuming. The purpose of this study was to compare a rapid phage/qPCR assay performed on peripheral blood mononuclear cells (PBMCs) with three standard methods of MAP detection: fecal MAP PCR; plasma antigen-specific IFN-γ & serum MAP ELISA hypothesizing that, if sensitive and specific, Johne animals would be positive and Control animals negative. We studied a well characterized herd of Holstein cattle that were naturally infected with MAP and their Controls.

Results

With phage/qPCR 72% (23/32) of Johne and 35% (6/17) of Controls were MAP positive. With fecal PCR 75% (24/32) of Johne and 0% (0/17) of Controls were MAP positive. With plasma antigen-specific IFN-γ 69% (22/32) of Johne and 12% (2/17) of Controls were MAP positive. With serum MAP ELISA, 31% (10/32) of Johne and 0% (0/17) of Controls were MAP positive. When phage / qPCR and fecal PCR results were combined, 100% (32/32) Johne and 35% (6/17) of Control animals were MAP positive. Younger Control animals (1–3 years) had significantly fewer plaques (25 ± 17 SEM) than older Controls (4–12 years) (309 ± 134 p = 0.04). The same trend was not observed in the Johne animals (p = 0.19).

Conclusions

In contrast to our hypothesis, using the phage/qPCR assay we find that viable circulating MAP can rapidly be detected from the blood of animals infected with, as well as those in the Control group evidently colonized by MAP. These data indicate that the presence of viable MAP in blood does not necessarily signify that an animal must of necessity be demonstrably ill or be MAP positive by standard diagnostic methods.

Timing, frequency and type of physician-diagnosed infections in childhood and risk for Crohn's disease in children and young adults

BACKGROUND

Recent experimental data show that exposure to microbes during early childhood can confer immunological tolerance and protect against Crohn's disease (CD). Epidemiological evidence for this link, however, remains controversial. Using prospective data, we examined the link between this hypothesis and risk for CD in children and young adults.

METHODS

A case-control study design was used. CD cases (diagnosed before age 20 years) were recruited from a tertiary-care pediatric hospital in Montreal, and population-based controls matched for age, gender and, geographical location were selected. Infection data were ascertained from physician-billing records. These records, which use International Classification of Diseases, Ninth Revision diagnostic codes, were consulted retrospectively but provide prospectively collected diagnostic information. Conditional logistic regression analysis was used to study potential associations. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated.

RESULTS

Four hundred nine cases and 1621 controls were included. Regression analysis adjusting for potential confounding variables suggested that any recorded infection before the diagnosis of CD was associated with reduced risk of CD (OR, 0.67; 95% CI, 0.48-0.93). The protective effect was restricted to infections occurring mainly before 5 years of age, with increasing number of infections resulting in greater protection (1-5 infections: OR, 0.74; ≥6 infections: OR, 0.61; P value for trend = 0.039). Infections affecting the oral and upper respiratory tracts, cellulitis, and, enteric infections seemed most protective.

CONCLUSIONS

Our study provides support for the hygiene hypothesis, whereby exposure to infections in early childhood could potentially reduce risks of CD.