A clustering of Crohn's disease in Mankato, Minnesota

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.

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.

Anaerobic adaptation of Mycobacterium avium subspecies paratuberculosis in vitro: similarities to M. tuberculosis and differential susceptibility to antibiotics

Background

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne’s disease in ruminants and is associated with Crohn’s disease (CD) in humans, although the latter remains controversial. In this study, we investigated the ability of MAP to adapt to anaerobic growth using the “Wayne” model of non-replicating persistence (NRP) developed for M. tuberculosis.

Results

All strains adapted to anaerobiosis over time in a manner similar to that seen with MTB. Susceptibility to 12 antibiotics varied widely between strains under aerobic conditions. Under anaerobic conditions, no drugs caused significant growth inhibition (>0.5 log) except metronidazole, resulting in an average decrease of ~2 logs.

Conclusions

These results demonstrate that MAP is capable of adaptation to NRP similar to that observed for MTB with differential susceptibility to antibiotics under aerobic versus anaerobic conditions. Such findings have significant implications for our understanding of the pathogenesis of MAP in vivo and the treatment of CD should this organism be established as the causative agent.

Identifying strains that contribute to complex diseases through the study of microbial inheritance

It has been 35 y since Carl Woese reported in PNAS how sequencing ribosomal RNA genes could be used to distinguish the three domains of life on Earth. During the past decade, 16S rDNA sequencing has enabled the now frequent enumeration of bacterial communities that populate the bodies of humans representing different ages, cultural traditions, and health states. A challenge going forward is to quantify the contributions of community members to wellness, disease risk, and disease pathogenesis. Here, we explore a theoretical framework for studies of the inheritance of bacterial strains and discuss the advantages and disadvantages of various study designs for assessing the contribution of strains to complex diseases.

Mycobacterium paratuberculosis as a cause of Crohn's disease

Crohn's disease is a chronic inflammatory bowel disease of unknown cause, affecting approximately 1.4 million North American people. Due to the similarities between Crohn's disease and Johne's disease, a chronic enteritis in ruminant animals caused by Mycobacterium avium paratuberculosis (MAP) infection, MAP has long been considered to be a potential cause of Crohn's disease. MAP is an obligate intracellular pathogen that cannot replicate outside of animal hosts. MAP is widespread in dairy cattle and because of environmental contamination and resistance to pasteurization and chlorination, humans are frequently exposed through contamination of food and water. MAP can be cultured from the peripheral mononuclear cells from 50-100% of patients with Crohn's disease, and less frequently from healthy individuals. Association does not prove causation. We discuss the current data regarding MAP as a potential cause of Crohn's disease and outline what data will be required to firmly prove or disprove the hypothesis.

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.

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

We report an ongoing outbreak of ulcerative colitis and Crohn's disease in Forest, Virginia involving 15 unrelated children and teenagers who resided in close proximity to dairy farms. Some of our cases demonstrated serologic evidence of Mycobacterium avium subspecies paratuberculosis infection, suggesting its potential role as an etiologic agent.

Ulcerative colitis and Crohn's disease: is Mycobacterium avium subspecies paratuberculosis the common villain?

Mycobacterium avium, subspecies paratuberculosis (MAP) causes a chronic disease of the intestines in dairy cows and a wide range of other animals, including nonhuman primates, called Johne's ("Yo-knee's") disease. MAP has been consistently identified by a variety of techniques in humans with Crohn's disease. The research investigating the presence of MAP in patients with Crohn's disease has often identified MAP in the "negative" ulcerative colitis controls as well, suggesting that ulcerative colitis is also caused by MAP. Like other infectious diseases, dose, route of infection, age, sex and genes influence whether an individual infected with MAP develops ulcerative colitis or Crohn's disease. The apparently opposite role of smoking, increasing the risk of Crohn's disease while decreasing the risk of ulcerative colitis, is explained by a more careful review of the literature that reveals smoking causes an increase in both diseases but switches the phenotype from ulcerative colitis to Crohn's disease. MAP as the sole etiologic agent of both ulcerative colitis and Crohn's disease explains their common epidemiology, geographic distribution and familial and sporadic clusters, providing a unified hypothesis for the prevention and cure of the no longer "idiopathic" inflammatory bowel diseases.

Possible transmission of Mycobacterium avium subspecies paratuberculosis through potable water: lessons from an urban cluster of Crohn's disease

A "cluster" of patients refers to the geographic proximity of unrelated patients with the same disease and suggests a common environmental cause for that disease. Clusters of patients with Crohn's disease have been linked to the presence of an infectious microorganism in unpasteurized milk and cheese, untreated water supplied by wells or springs, animal manure used as fertilizer for family vegetable gardens, and bodies of water contaminated by agricultural runoff.

Mycobacterium avium subspecies paratuberculosis (MAP) is the suspected cause of Crohn's disease. MAP causes a disease in dairy cows and other animals that is similar to Crohn's disease, called Johne's ('Yo-knees') disease or paratuberculosis. Dairy cows with Johne's disease secrete MAP into their milk and excrete MAP into their feces. MAP is present in untreated water such as well water, in bodies of water contaminated by agricultural runoff, and in unpasteurized milk and cheese.

The "treatment" of "tap" water to make it "drinkable" or "potable" by the processes of sedimentation, filtration and chlorination has little to no effect on MAP. MAP is so resistant to chlorine disinfection that such disinfection actually selects for its growth. Other subspecies of Mycobacterium avium grow in biofilms present on tap water pipes. Despite the documented presence of MAP in tap water and its probable growth on tap water pipes, clusters of Crohn's disease have not previously been described in relationship to tap water pipes supplying patients' homes.

This report describes three unrelated individuals who lived on the same block along a street in a midwestern American city and developed Crohn's disease within four years of each other in the 1960's. A common tap water pipe supplied their homes.

This is the first reported cluster of Crohn's disease possibly linked to fully treated drinking water, and is consistent with previously reported clusters of Crohn's disease linked to an infectious microorganism in water.

New global map of Crohn's disease: Genetic, environmental, and socioeconomic correlations

Seventy-five years after the initial characterization of Crohn's disease (CD), much remains obscure about its etiology. The authors sought to evaluate the incidence trends of the last 25 years worldwide, and the existence of potential correlations with genetic, environmental, and socioeconomic factors that could be etiologically implicated in the pathogenesis of CD. Relevant medical literature for individual countries on the incidence of CD, on the incidence of associated genetic mutations, and on the incidence of suggested etiologic infectious agents such as Mycobacterium avium paratuberculosis were retrieved from published medical literature, reports from relevant international congresses, and through official reports from national health authorities. Increasing trends have been observed almost worldwide, with a broad north-south gradient still prevailing in Europe. Distinct regions of New Zealand, Canada, Scotland, France, the Netherlands, and Scandinavia represent the highest incidence areas. Industrialized status and affluence are the common denominators between endemic areas, but are too broad as terms to strongly indicate any particular etiological role. The increasing trends observed in Asia still account for a low prevalence of the disease and may represent increased detection and diagnostic ability of local health systems. Genetic associations are variably reproduced worldwide, in a manner inconsistent with a strong etiologic relationship. Data on paratuberculosis incidence are scarce, and the existing ones are ambivalent regarding an even indirect correlation between CD and an infectious trigger.

Search for evidence of recurring or persistent viruses in Crohn's disease

New-onset Crohn's disease and acute flares are often associated with viral infections. The aim of this study was to search for evidence of persistent or recurrent viruses in patients. Tissue blocks were obtained from surgical specimens from patients and a control population. 111 samples were tested by PCR or RT-PCR, for EBV, CMV, HSV 1, HSV 2, HHV 8, pestiviruses, and enteroviruses. Additionally, seven sets of serum samples, including pre-operative and post-operative samples, from CD patients were analyzed serologically for antibodies to EBV. The tests revealed evidence of EBV nucleic acid in tissues of 11 patients from a total of 70 tested (15.7%) and in tissues of 3 of 41 control subjects (7.3%). Evidence of pestivirus was found in one CD patient, while one patient and one control were positive for CMV. No HSV 1 or 2, HHV 8 or enteroviruses were found. The serologic tests revealed that five of seven CD patients had antibodies against the early protein, the capsid protein and the EBV nuclear antigen (EBNA). The titers were not significantly altered post-surgically. None of the patients had antibodies of the IgM isotype. Our findings vary from those of Ruther et al. who demonstrated evidence of EBV in tissues from 7 of 11 (64%) German CD patients. Antibodies to early EBV viral antigen and to nuclear antigen in five of seven Belgian patients suggest persistent active viral infection.

Incidence of Crohn’s disease and CARD15 mutation in a small township in Sicily

BACKGROUND

The incidence of Crohn's disease (CD) has been shown to be lower in Southern than in Northern Europe. Data on the frequency of the NOD2/CARD15 mutations for Mediterranean area are very scant.

AIM

To determine the incidence of CD from 1979 to 2002 in a township in Sicily together with the allele frequency of NOD2/CARD15 mutations in patients, family members and controls, and to determine the allele frequency of these mutations in sporadic CD from other areas of Sicily in comparison with a control population.

METHODS

Casteltermini is a small town close to Agrigento (Sicily) with a population of 9,130 inhabitants. All the diagnoses of inflammatory bowel disease (IBD) made from 1979 to 2002 were obtained through the local health authority. NOD2/CARD15 mutations were studied in 23 out of the 29 patients with CD in Casteltermini, in 60 family members and in 64 controls. NOD2/CARD15 was also studied in 80 sporadic cases of CD disease among Sicilians outside Casteltermini and 118 healthy controls.

RESULTS

From 1979 to 2002, 29 patients with CD and 13 patients with ulcerative colitis (UC) were registered. The 6-year mean incidence of CD ranged from 8.0 to 17 new cases for every 100,000 inhabitants, whereas the mean incidence of UC ranged from five new cases to 7.8 for every 100,000 inhabitants. The allele frequencies of NOD2/CARD15 mutations (L1007finsC, G908R, R702W) were 8.7, 4.3 and 8.7%, respectively, in CD cases; 5.0, 4.2 and 3.1% in family members; 1.6, 2.3 and 3.1% in controls. In sporadic Sicilian CD patients outside Casteltermini the allele frequency was 7.5, 8.1, 6.2% whereas in control population it was 3.3, 1.6, 1.6%.

CONCLUSIONS

A high incidence of CD compared with UC was observed in this small town in Southern Italy. The frequency of NOD2/CARD15 mutations in CD is similar to other Caucasian population studied so far.

[Environmental risk factors in Crohn's disease and ulcerative colitis (excluding tobacco and appendicectomy)]

A rapid increase in the incidence of Crohn's disease and ulcerative colitis in developed countries, the occurrence of Crohn's disease in spouses, and a lack of complete concordance in monozygotic twins are strong arguments for the role of environmental factors in inflammatory bowel disease (IBD). Research in the field of environmental factors in IBD is based upon epidemiological (geographical and case-control), clinical and experimental studies. The role of two environmental factors has clearly been established in IBD. Smoking is a risk factor for Crohn's disease and a protective factor for ulcerative colitis; appendectomy is a protective factor for ulcerative colitis. Many other environmental factors for IBD have been investigated, including infectious agents, diet, drugs, stress and social status. They are detailed in the present review. Among them, atypical Mycobacteria, oral contraceptives and antibiotics could play a role in Crohn's disease. To date, three hypotheses associate environmental factors with the pathophysiology of IBD (loss of tolerance of intestinal immune system towards commensal bacterial flora): the hygiene, infection and cold chain hypotheses. Much work remains to be done to identify risk factors for IBD. Research identifying environmental factors that might cause a predisposition to IBD is useful. It may lead to disease prevention in subjects who are genetically predisposed and disease improvement in patients.

Environmental factors in inflammatory bowel disease: a co-twin control study of a Swedish-Danish twin population

BACKGROUND

Genetics and environmental factors are implicated in the etiology of inflammatory bowel disease (IBD). We studied environmental factors in a population-based Swedish-Danish twin cohort using the co-twin control method.

SUBJECTS AND METHODS

A questionnaire was sent to 317 twin pairs regarding markers of exposures in the following areas: infections/colonization and diet as well as smoking, appendectomy, and oral contraceptives. Odds ratios (OR) were calculated by conditional logistic regression. When confounding appeared plausible, multivariate conditional logistic regression was added. The questions were also divided into topic groups, and adjustment was made for multiple testing within each of the groups.

RESULTS

The response rate to the questionnaire was 83%. In consideration of the study design, only discordant pairs were included (Crohn's disease [CD], n = 102; ulcerative colitis [UC], n = 125). Recurrent gastrointestinal infections were associated with both UC (OR, 8.0; 95% confidence interval [CI], 1.0-64) and CD (OR, 5.5; 95% CI, 1.2-25). Hospitalization for gastrointestinal infections was associated with CD (OR, 12; 95% CI, 1.6-92). Smoking was inversely associated with UC (OR, 0.4; 95% CI, 0.2-0.9) and associated with CD (OR, 2.9; 95% CI, 1.2-7.1).

CONCLUSIONS

The observed associations indicate that markers of possible infectious events may influence the risk of IBD. Some of these effects might be mediated by long-term changes in gut flora or alterations in reactivity to the flora. The influence of smoking in IBD was confirmed.

Haplotype of prostaglandin synthase 2/cyclooxygenase 2 is involved in the susceptibility to inflammatory bowel disease

AIM: Prostaglandin G/H synthase 2 (PTGS2 or COX2) is one of the key factors in the cellular response to inflammation. PTGS2 is expressed in the affected intestinal segments of patients with inflammatory bowel diseases (IBD). In IBD patients, non-steroidal anti-inflammatory drugs, which have been shown to reduce both the production and activity of PTGS2, may activate IBD and aggravate the symptoms. We aimed at examining genetic variants of PTGS2 that may be risk factors for IBD.

METHODS: We genotyped 291 individuals diagnosed with IBD and 367 controls from the Dutch population for the five most frequent polymorphisms of the PTGS2 gene. Clinical data were collected on all patients. DNA was extracted via normal laboratory methods. Genotyping was carried out using multiplex PCR followed by the Invader Assay and the 5 exonuclease assay (TaqMan). New polymorphism screening was performed by pre-screening with denaturing high-performance liquid chromatography, followed by fluorescent sequencing.

RESULTS: Allele 5209G was weakly associated with Crohn's disease (odds ratio [OR] 1.63, 95% confidence interval [CI] 1.03-2.57), and allele 8473T with ulcerative colitis (OR 1.50, 95%CI 1.00-2.27). The haplotype including both alleles showed a strong association with IBD (OR 13.15, 95%CI 3.17-116.15). This haplotype, while rare (-0.3%) in the general population, is found more frequently in patients (3.5%).

CONCLUSION: Our data suggest that this haplotype of PTGS2 contributes to the susceptibility of IBD.

Environmental factors in familial Crohn's disease in Belgium

BACKGROUND

Environmental factors are believed to trigger the onset of Crohn's disease (CD) in genetically susceptible individuals. The aim of this study was to assess environmental and familial factors that might be etiologically related to CD.

METHODS

Twenty-one families with 3 or more affected first-degree relatives were studied, together with 10 matched control families. There were 74 patients with CD, 84 unaffected family members, and 59 controls. Family members were interviewed together at the parental home. A 176-item questionnaire delved into first symptoms, childhood vaccinations and diseases, food items, potable water supplies, social activities, travel, pets, and home and surrounding environment. Questions were directed specifically for 2 time-frames, childhood until age 20 and a 10-year epoch before the onset of first symptoms within a family. The possible factors linked to disease were evaluated using univariate and multivariate logistic regression.

RESULTS

There were significantly more smokers in the patients and their relatives than in controls. Patients had more appendicitis during adolescence, ate less oats, rye, and bran than controls, and consumed more unpasteurized cheese. Patients drank significantly less tap water and more well water than controls. Clustering of cases in time occurred in 13 of the 21 affected families.

CONCLUSIONS

The less frequent consumption of oats, rye, and bran and the more frequent eating of unpasteurized cheeses imitate potential dietary influences on gastrointestinal flora. More importantly, our data suggest that the drinking of well water represents an important risk factor for CD.

Is Crohn's disease caused by a mycobacterium? Comparisons with leprosy, tuberculosis, and Johne's disease

Although Crohn's disease is considered to be autoimmune in origin, there is increasing evidence that it may have an infectious cause. The most plausible candidate is Mycobacterium avium subspecies paratuberculosis (MAP). Intriguingly, Koch's postulates may have been fulfilled for MAP and Crohn's disease, even though they still have not been met for Mycobacterium leprae and leprosy. In animals MAP causes Johne's disease, a chronic wasting intestinal diarrhoeal disease evocative of Crohn's disease. Johne's disease occurs in wild and domesticated animals, including dairy herds. Viable MAP is found in human and cow milk, and is not reliably killed by standard pasteurisation. MAP is ubiquitous in the environment including in potable water. Since cell-wall-deficient MAP usually cannot be identified by Ziehl-Neelsen staining, identification of MAP in human beings requires culture or detection of MAP DNA or RNA. If infectious in origin, Crohn's disease should be curable with appropriate antibiotics. Many studies that argue against a causative role for MAP in Crohn's disease have used antibiotics that are inactive against MAP. However, trials that include macrolide antibiotics indicate that a cure for Crohn's disease is possible. The necessary length of therapy remains to be determined. Mycobacterial diseases have protean clinical manifestations, as does Crohn's disease. The necessity of stratifying Crohn's disease into two clinical manifestations (perforating and non-perforating) when interpreting the results of antibiotic therapy is discussed. Rational studies to evaluate appropriate therapies to cure Crohn's disease are proposed.

Familial Crohn's disease in single or multiple first-degree relatives

The strongest currently recognized risk factor for Crohn's disease (CD) development is having a relative with the disease. In this study, 1,000 patients with CD, seen directly by the investigator during a period of more than 20 years, were consecutively evaluated for a family history of CD. There were 140 patients who reported a relative with CD. Of these, all 87 first-degree relatives were confirmed to have CD (36 men and 51 women). Siblings, particularly women, were most commonly affected in comparison with parents or children. There were 65 with a single affected first-degree relative and 22 with multiple affected first-degree relatives. In this series, the tendency to have a female sibling with CD was further increased in those with multiple affected first-degree relatives. Although the age of diagnosis of children was less than the age of diagnosis in the respective parents, there were almost identical numbers of mother-child and father-child pairs. These findings in a population with prolonged follow-up by the same physician may reflect a bias toward case ascertainment rather than the previously reported phenomena in recruited populations of genetic anticipation and genomic imprinting. Patients with multiple first-degree relatives were older with more extensive disease in both ileal and colonic sites compared with those with only a single first-degree relative and more frequent colonic disease. Future studies are needed to further explore the role of both genetic and environmental factors in the pathogenesis and phenotypic expression of familial CD.