The Broad Street pump revisited: dairy farms and an ongoing outbreak of inflammatory bowel disease in Forest, Virginia

Pathogenic mechanisms and etiologic aspects of Mycobacterium avium subspecies paratuberculosis as an infectious cause of cutaneous melanoma

Infectious etiologies have previously been proposed as causes of both melanoma and non-melanoma skin cancer. This exploratory overview explains and presents the evidence for the hypothesis that a microorganism excreted in infected ruminant animal feces, Mycobacterium avium subspecies paratuberculosis (MAP), is the cause of some cases of cutaneous melanoma (CM). Occupational, residential, and recreational contact with MAP-contaminated feces, soil, sand, and natural bodies of water may confer a higher rate of CM. Included in our hypothesis are possible reasons for the differing rates and locations of CM in persons with white versus nonwhite skin, why CM develops underneath nails and in vulvar skin, why canine melanoma is an excellent model for human melanoma, and why the Bacille Calmette-Guérin (BCG) vaccine has demonstrated efficacy in the prevention and treatment of CM. The pathogenic mechanisms and etiologic aspects of MAP, as a transmittable agent underlying CM risk, are carefully deliberated in this paper. Imbalances in gut and skin bacteria, genetic risk factors, and vaccine prevention/therapy are also discussed, while acknowledging that the evidence for a causal association between MAP exposure and CM remains circumstantial.

The evidence for Mycobacterium avium subspecies paratuberculosis (MAP) as a cause of nonsolar uveal melanoma: a narrative review

Background and Objective

Animal microorganisms have been proposed as a cause of human cancers associated with farming, agricultural occupation or residence, and related downstream exposures. Several studies have described uveal melanoma (UvM) as a farming-associated cancer. A possible suspect is the animal microorganism Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of paratuberculosis in dairy cows. This microbe is transmitted to humans through various means, including contact with animal faeces, contaminated dust and soil, organic fertilizers, and as workers in slaughterhouses/animal processing facilities. The objective of the current manuscript was to examine the putative association between Mycobacterium avium sub-species paratuberculosis and non-solar UvM.

Methods

Online data sources (PubMed, Scopus, Cochrane Library, and Google) published in English between 1980 to present were searched for key words pertaining to MAP exposure, farming-related occupations and activities, and locations with or in the vicinity of dairy cattle.

Key Content and Findings

While higher than expected rates of eye cancer have been suggested among dairy farmers, with MAP being ubiquitous in their environment, the involvement of MAP in the aetiology of non-solar UvMs (which account for ~97% of UvM cases) remains uncertain.

Conclusions

Alternative explanations exist and future cause-and-effect research is needed to answer this hypothesis. A precautionary approach to exposure continues to be a prudent strategy.

The epidemiology of inflammatory bowel disease: Clues to pathogenesis?

Historically, inflammatory bowel disease (IBD) was most common in North America and Europe and more common with a north-south gradient. Over the past century, there has been a marked increase in IBD in general and in childhood IBD in particular and over the past 50 years IBD has spread into the developing world. The greatest risk factor of developing IBD is an affected family member. Concordance rates between dizygotic twins is ∼4% and ∼50% in monozygotic twins, and more than half of pairs are diagnosed within 2 years of each other. Nevertheless, most patients with IBD do not have an affected family member. More than 200 genes are associated with an increased risk for IBD, but most associations are weak with odds ratios between 1.2 and 2.0 suggesting the environment plays a role. IBD is more common in urban than rural regions and is associated with "good standards" of domestic hygiene during childhood. People who migrate from areas with a low incidence to areas with a high incidence of IBD have an increased risk of developing IBD and the younger they are when they migrate, the greater their risk of developing IBD. Moreover, people who migrate from regions with a high incidence to areas with a low incidence of IBD have a decreased risk of developing IBD. Together, these findings strongly suggest particular environmental exposures occurring early in life may trigger inflammatory bowel disease in genetically susceptible individuals. The key is figuring out what those exposures might be.

The Gut Microbiome and the Triple Environmental Hit Concept of Inflammatory Bowel Disease Pathogenesis

The incidence of chronic inflammatory bowel diseases (IBDs), such as Crohn's disease (CD) and ulcerative colitis (UC) have significantly increased in recent decades implicating environmental effects. The developmental origin of disease concept provides a theoretical framework by which the complex interplay between environmental factors and host cells, particularly during vulnerable time periods, ultimately cause disease, such as IBD. Epigenetics has been proposed as the underlying mechanism within this concept, turning environmental triggers into stable changes of cellular function. Adding further to the complexity of IBD is the gut microbiome, which is equally responsive to the environment, and can impact host cell function, where recent findings underscore the stochastic and individualized nature of such effects. We review the microbiome literature through a novel triple environmental hit concept (priming, modulation, and trigger) of IBD pathogenesis. We propose that there are at least 3 distinct stages during an individual's lifespan where random/stochastic events driven by environmental influences are necessary for ultimately developing IBD. By this means, we speculate that microbiome-directed therapeutics carry potential for individualized prevention and dynamic treatment of IBD.

Crohn's disease and environmental contamination: Current challenges and perspectives in exposure evaluation

Although the incidence of Crohn's disease has increased worldwide over the past 30 years, the disorder's exact causes and physiological mechanisms have yet to be determined. Given that genetic determinants alone do not explain the development of Crohn's disease, there is growing interest in "environmental" determinants. In medical science, the term "environment" refers to both the ecological and social surroundings; however, most published studies have focused on the latter. In environmental and exposure sciences, the term "environment" mostly relates to contamination of the biotope. There are many unanswered questions on how environmental hazards might contribute to the pathogenesis of Crohn's disease. Which pollutants should be considered? Which mechanisms are involved? And how should environmental contamination and exposure be evaluated? The objective was to perform a systematic review of the literature on Crohn's disease and environmental contamination. We searched the PubMed, Google Scholar, Scopus, ISI Web of Science and Prospero databases. We considered all field studies previous to April 2019 conducted on human health indicators, and evaluating exposure to all type of physical, biological and chemical contamination of the environment. The lack of clear answers to date can be ascribed to the small total number of field studies (n = 16 of 39 publications, most of which were conducted by pioneering medical scientists), methodological differences, and the small number of contaminants evaluated. This make it impossible to conduct a coherent and efficient meta-analysis. Based on individual analysis of available studies, we formulated five recommendations on improving future research: (i) follow up the currently identified leads - especially metals and endocrine disruptors; (ii) explore soil contamination; (iii) gain a better knowledge of exposure mechanisms by developing transdisciplinary studies; (iv) identify the most plausible contaminants by developing approaches based on the source-to-target distance; and (v) develop registries and cohort-based analyses.

Increasing Incidence of Crohn's Disease with Familial Clustering in the Kingdom of Bahrain: A 25-Year Population-based Study

BACKGROUND

The incidence of Crohn's disease has been increasing in developed countries; whether this trend has extended to countries in Middle East, especially in the Arab world, remains unclear. Our aim was to study the epidemiology, incidence, time trends and clustering of Crohn's disease within the population of the Kingdom of Bahrain.

METHODS

A retrospective case-cohort study was conducted on patients diagnosed with Crohn's disease at Bahrain Specialist Hospital between 1990 and 2015. The diagnosis was based on clinical, radiological, endoscopic, and histological examinations.

RESULTS

Five hundred twenty-two cases were eligible for analysis; 14.5% were below the age of 19 with a male-to-female ratio of 1.1:1. The overall incidence was 4.8/100,000 person-years and significantly increased from 5.5/100,000 person-years during the 1990's to 8.0/100,000 person-years during the last study period [incidence rate ratio (IRR) 0.32, 95% CI = 0.26-0.42]. This trend was persistent for adults, children, men and women. There were 129 patients with at least one family member diagnosed with Crohn's disease consisting of 40 families. Three clusters were identified based on first or second degree relationship of the family member. The mean interval for diagnosis between family members was significantly shorter between siblings than second degree relatives; (2.0 ± 1.2 years) versus (5.0 ± 2.8 years), respectively; (P = 0.04).

CONCLUSIONS

The incidence rate of Crohn's disease in Bahrain is comparable to the U.S.A and has increased for men and women in all age groups. Crohn's disease clusters were common among families and included up to 3 generations consistent with presence of a common source or common genetic factors.

Environmental triggers for IBD

The fundamental elucidation of how environmental influences provoke the initiation of disease as well as flares of inflammatory bowel disease (IBD) remains incomplete. The current understanding of these diseases suggests that ulcerative colitis (UC) and Crohn's disease (CD) result from poorly defined interactions between genetic and environmental factors which culminate in the pathologic effects and clinical manifestations of these diseases. The genetic variant appears not sufficient itself to lead to the development of the clinical disease, but likely must combine with the environmental factors. The intestinal microbiome is pivotal to IBD development. A greater understanding of the contribution of these factors to dysbiosis is critical, and we aspire to restoring a healthy microbiome to treat flares and ideally prevent the development of IBD and its complications. This article aims to place the environmental influences in the context of their potential contribution to the development of the pathophysiology of IBD.

Free-ranging Rocky Mountain bighorn sheep and an outbreak of inflammatory bowel disease along the Clark Fork River in Plains, Montana

Nine individuals with ulcerative colitis or Crohn disease grew up or lived in Plains, Montana, a 1,200-person community adjacent to the Clark Fork River near herds of free ranging Rocky Mountain bighorn sheep. This inflammatory bowel disease outbreak is similar to others that have occurred along rivers contaminated by animal feces.

Mycobacterium avium ss paratuberculosis-associated diseases: piecing the Crohn's puzzle together

The relation of Mycobacterium avium ss paratuberculosis (MAP) to Crohn's Disease (CD) and other MAP-associated conditions remains controversial. New data, coupled with the analogous Helicobacter pylori (H. pylori) story, has permitted us to piece together the MAP puzzle and move forward with a more scientific way of treating inflammatory bowel disease, particularly CD. As infection moves centre stage in inflammatory bowel disease, the dated "aberrant reaction" etiology has lost scientific credibility. Now, our growing understanding of MAP-associated diseases demands review and articulation. We focus here on (1) the concept of MAP-associated diseases; (2) causality, Johne Disease, the "aberrant reaction" hypothesis; and (3) responses to published misconceptions questioning MAP as a pathogen in CD.