NEWS

In March 2020, in response to the global pandemic brought about by the COVID-19 virus the Committee of the 15th International Association for Paratuberculosis Colloquium 2020 made the hard decision to postpone ICP 2020 until 2021. The event was originally scheduled for 14^th -18^th June, 2020 in Dublin Castle. The 15^th International Colloquium for Paratuberculosis was then re-scheduled for the 6^th – 9^th April 2021.

Last month the Local Organizing Committee (LOC) was faced with the decision of having to postpone again or to have a virtual conference next April. It was decided by the LOC to go for a live conference in June 2022. The committee was delighted that the organizers of the 16^th ICP in Jaipur, India agreed to this and have postponed their Colloquium until 2024.

The ICP Committee invites you to the 15^th IAP Colloquium in Dublin, Ireland in June 2022. Delegates attending the conference can be assured of a productive and memorable colloquium, discover Irish heritage, culture and music and of course, experience the world-renowned hospitality of Ireland.

Follow this website to stay informed about the 15-ICP being held in 2022.

Dr. Peter Windsor and Dr. Richard Whittington published a review article on ovine Johne’s disease (OJD) control in Australia. This excellent review article appears in the journal Animals and is Open Access. It nicely reviews the pathogenesis and control of paratuberculosis in sheep, but the most interesting part of the article addresses the top 10 subjects of misinformation about OJD in Australia.

Abstract

OJD is no longer the serious animal health issue that it was for many Australian rural communities a decade and a half ago. Despite declining OJD prevalence as determined by abattoir surveillance, the disease continues to spread, with OJD extension programs required to continually address the  misinformation promulgated by some disaffected producers as new areas have become affected. Improved regional and on-farm biosecurity, including the introduction of a risk-based trading system, may have contributed to improved attitudes to OJD control, although attitudinal differences between OJD endemic areas and where the disease is not well established remain. Declines in on-farm OJD prevalence are almost certainly attributable to the widespread uptake of vaccination programs, although encouraging the ongoing use of vaccination to prevent recrudescence and improved biosecurity when mortalities disappear, remains challenging. Vaccination has provided a robust strategy for managing OJD and contributed significantly to the health of Australian sheep and the lives of producers with affected properties. As vaccination offers a pathway to reduce the risk of MAP infection entering the human food chain from small ruminant products, it should be more widely adopted globally, accompanied by research efforts to improve efficacy and importantly, the safety of vaccination to both operators and livestock.

Comment: Not all countries, such as the U.S., have access to the vaccine for paratuberculosis that is used in Australia. For pictures of sheep before and after developing clinical Johne’s disease can be found here.

Claudio Pigoli and colleagues report on multiple cases of Johne’s disease in captive scimitar-horned oryx at a zoo in Italy. Their research article was published in the journal Animals and is Open Access. Genomic analysis shows that the MAP strains recovered from the Oryx are closely related to those isolated from cattle in Italy: evidence of ongoing spillover from domestic livestock to wildlife and animals in zoos.

Abstract

Paratuberculosis, a chronic disease caused by Mycobacterium avium subsp. paratuberculosis (MAP), in ten scimitar-horned oryxes (SHOs) hosted in an Italian zoological park and originating from a Slovakian flock, was documented by pathology, molecular, cultural, and serological testing. The infection origin in this threatened species was also investigated by genomic analyses. Following the death of six of the 10 SHOs, serial investigations of dead and alive animals were performed. Necropsy, carried out on five out of six animals, identified intestinal thickening and mesenteric lymphadenomegaly in one of the animals. Histopathology (5/6) revealed lepromatous (2/5) and tuberculoid (2/5) intestinal forms or lack of lesions (1/5). Ziehl-Neelsen and immunohistochemistry stains identified two multibacillary, two paucibacillary forms, and one negative case. MAP was identified by quantitative PCR (qPCR) in tissue samples in five out of five SHOs and was microbiologically isolated from two of the three animals whose fresh tissue samples were available. Fecal samples were collected in four of the six dead animals: all four resulted positive to qPCR and in MAP was isolated in three. ELISA identified MAP-specific antibodies in three of the five dead animals whose serum was available. qPCR identified MAP in the freshly deposited feces of two out of the four alive animals. From the feces of these two animals, MAP was microbiologically isolated in one case. All isolates were classified as MAP type C and profiled as INMV2 and MVS27 by molecular analysis. Genomic analysis of a field isolate revealed clustering with a European clade but was more similar to Italian than East European isolates. Our findings underline that paratuberculosis should always be considered in zoological parks in which endangered species are hosted. Infection can be subclinical, and multiple combined testing techniques may be necessary.

Author’s Conclusions

Our results underline the importance of considering paratuberculosis in zoological parks, where endangered species are often hosted. Paratuberculosis could represent a risk for the conservation of rare animals, and it is essential to include it in the panel of diagnostic tests to be performed on hosted animals. We also suggest testing dead animals, in which different diagnostic approaches are combined, with the final aim of fully elucidating the causes of death and defining their health status regarding paratuberculosis. WGA can help to trace the origin of infections, particularly in the case of moved animals. This study reports the first genome of an MAP strain isolated from SHOs and shows that the strain likely derived from the Italian cattle livestock, in which MAP is endemic.

For more on Johne’s disease in zoo animals check out this page of our website.

Two Related Research Publications

Two excellent articles about use of the ELISA diagnostic test on milk samples (milk ELISA) appeared in the past few weeks. The first, by Ozsvari and colleagues uses the milk ELISA to evaluate the impact of paratuberculosis on milk production, fertility, and culling in large commercial dairy herds in Hungary.  This article published in Frontiers in Veterinary Science is Open Access.

Abstract

Paratuberculosis (PTBC) is a chronic disease caused by Mycobacterium avium subsp. paratuberculosis (MAP), which is common in dairy herds worldwide, although the scale of its impact on herd productivity is unclear. The aim of our study was to determine the differences between MAP ELISA positive vs. negative cows in terms of milk production and quality, reproductive parameters, and culling. The data of five large dairy herds that participated in the voluntary PTBC testing program in Hungary were analyzed. Cows were tested by ELISA (IDEXX Paratuberculosis Screening Ab Test, IDEXX Laboratories, Inc., Westbrook, ME, USA) using milk samples collected during official performance testing. The outcome of the initial screening test involving all milking cows in the herds was used for the classification of the cows. The 305-day milk production, reproduction and culling data of 4,341 dairy cows, and their monthly performance testing results (n = 87,818) were analyzed. Multivariate linear and logistic models, and right censored tobit model were used for the statistical analysis. Test-day and 305-day milk production of ELISA positive cows decreased by 4.6 kg [95% CI: 3.5–5.6 kg, P < 0.0001 (−13.2%)] and 1,030 kg [95% CI: 708–1,352 kg, P < 0.0001 (−9.4%)], compared to their ELISA negative herdmates, respectively. Milk ELISA positive cows had 35.8% higher [95% CI: 17.9–56.4%, P < 0.0001] somatic cell count, on average. Test positive cows conceived 23.2 days later [95% CI: 9.2–37.3 days, P = 0.0012 (+16.5%)] and their calving interval was 33.8 days longer [95% CI: 13.2–54.4 days, P = 0.0013, (+9.7%)], compared to the negative cows, on average. Milk ELISA positive cows were less likely to conceive to first insemination (odds ratio: 0.49, 95% CI: 0.31–0.75, P = 0.0013), and required 0.42 more inseminations to conceive [95% CI: 0.07–0.77, P = 0.0192 (+13.7%)], on average. Milk ELISA positive cows were culled 160.5 days earlier after testing compared to their ELISA negative herdmates (95% CI: 117.5–203.5 days, P < 0.0001). Our results suggest that MAP ELISA positive cows experience decreased milk production, milk quality, fertility, and longevity, which supports the need to control the prevalence of PTBC in dairy herds.

______________

The second publication is by Barden and colleagues from the U.K. describes the effect of skin testing for bovine tuberculosis (TB) on milk ELISA results.  This article published in the journal Preventive Veterinary Medicine is available online only until November 29.

Abstract

Background: In the UK, quarterly Johne’s disease milk antibody ELISAs (JD-mELISAs) are commonly used to classify animals which are likely to be infectious, termed “red cows”. “Red cows” are classified following two positive results from the previous four tests (e.g. + - - +). All cattle are also regularly screened for bovine tuberculosis using intradermal avian and bovine tuberculin, and it is advised to maintain a 60 day interval between a tuberculosis test and JD-mELISA. Aims: To evaluate the impact of bovine tuberculosis testing on JD-mELISAs, and to quantify the impact of test specificity and “red cow” classification test pattern on the probability of infection.

Methods: Four years of individual cow milk records with JD-mELISA results were collated from 735 dairy farms and matched to tuberculosis testing records. A two-level multivariable logistic regression model quantified the effect of tuberculosis testing on JD-mELISA result. The specificity and age-dependent sensitivity of a single JD-mELISA were estimated and used to calculate likelihood ratios following each test. Using Bayes’ theorem, the posterior probability of infection with Johne’s disease was calculated for different specificities, ages of cow, and patterns of test results.

Results: There were increased odds of a positive JD-mELISA if it was ≤30 days (OR: 2.1) or 31− 60 days (OR: 1.2) after a tuberculosis test, compared to >90 days. A larger avian skin reaction at the tuberculosis test was also associated with increased odds of a positive JD-mELISA. The proportion of cows which tested exclusively negative after their first positive JD-mELISA was higher if that JD-mELISA was ≤30 days after a tuberculosis test compared to >90 days. The posterior probability of infection reduced substantially when the test specificity was slightly reduced. In “red cows” classified following two consecutive positive tests, if the test specificity was reduced to 0.95, then the posterior probability of infection was only >95 % if the prior probability was >13 %. If the “red cow” classification was due to two non-consecutive positive tests (+ - - +), the posterior probability of infection was only >95 % if the prior probability was >43 %.

Conclusions: Testing for Johne’s disease within 60 days of a tuberculosis test is associated with a higher chance of a positive JD-mELISA and this may reflect a reduction in the ELISA specificity. Relatively small reductions in JD-mELISA specificity can markedly reduce the posterior probability of infection which also depends on the pattern of test results which classifies “red cows”. [Red cows are those with 2 consecutive positive milk ELISA tests.]

____________

Comment: The milk ELISA is the most affordable testing option for commercial dairy cattle herds. It primarily identifies cows in the more advanced stages of a MAP infection. As the Ozsvari study shows, milk ELISA-positive cows are those that are less productive and likely to be culled sooner (160.5 days earlier) that their milk ELISA-negative herdmates. In countries with endemic bovine TB, where TB testing of cattle happens regularly, it is important to avoid use of the milk ELISA for at least 60 days after a whole herd TB skin test. TB skin testing seems to increase the rate of false-positive test results (decreases assay specificity).

Milk ELISA testing importantly makes JD control more affordable and thus increases producer participation in national programs like the one in the U.K. However, limitations in diagnostic sensitivity mean that while it is a useful tool for controlling MAP-infections in dairy cattle herds it is not sufficiently sensitive to drive eradication of the infection from herds. For that purpose, more sensitive tests, such as the fecal PCR, are required.

Medical gastroenterologists commonly raise five concerns that seem to argue against a role for MAP in Crohn’s disease.

They are:

1. Why is there variability in studies which aim to detect MAP in Crohn’s patients?
2. Has MAP fulfilled Koch’s postulates?
3. Why does immunosuppressive therapy not worsen Crohn’s Disease if it is caused by MAP, as is seen with MTB (the cause of tuberculosis)?
4. Why is the incidence of Crohn’s not higher in at‑risk subgroups, such as veterinarians or farmers?
5. If MAP causes Crohn’s, why doesn’t atypical mycobacterial antibiotic therapy (AMAT) cure Crohn’s, and related to that, have RCTs (randomized controlled clinical trials) shown that AMAT is ineffective?

Dr. Gurav Agrawal and colleagues (myself included) published and invited review in the journal Digestive Diseases and Sciences addressing these 5 questions. The article is Open Access (11 pages with 86 references).

Abstract

For decades, Mycobacterium avium subspecies paratuberculosis (MAP) has been linked to the pathogenesis of Crohn’s disease. Despite many investigations and research efforts, there remains no clear unifying explanation of its pathogenicity to humans. Proponents argue Crohn’s disease shares many identical features with a granulomatous infection in ruminants termed Johne’s disease and similarities with ileocecal tuberculosis. Both are caused by species within the Mycobacterium genus. Sceptics assert that since MAP is found in individuals diagnosed with Crohn’s disease as well as in healthy population controls, any association with CD is coincidental. This view is supported by the uncertain response of patients to antimicrobial therapy. This report aims to address the controversial aspects of this proposition with information and knowledge gathered from several disciplines, including microbiology and veterinary medicine. The authors hope that this discussion will stimulate further research aimed at confirming or refuting the contribution of MAP to the pathogenesis of Crohn’s disease and ultimately lead to advanced targeted clinical therapies.

Worth noting:

As evidence that some gastroenterologists think MAP is a cause of Crohn's disease, in the UK, a phase I clinical trial has started to investigate the safety and efficacy of two candidate MAP vaccines in patients with active Crohn's disease (ISRCTN - ISRCTN36126048).

Mary Garvey, Lecturer at the Institute of Technology Sligo, Sligo, Ireland published a review article titled:  Mycobacterium Avium Paratuberculosis: A Disease Burden on the Dairy Industry in the journal Animals (11 pages with 58 references).

Abstract

Mycobacterium avium paratuberculosis is responsible for paratuberculosis or Johne’s disease in cows, having economic impacts on the dairy industry and a prevalence rate exceeding 50% in dairy herds. The economic burden of Johne’s disease relates to decreased milk production and costs of disease prevention, treatment, and management, while having an economic impact on dairy producers, processors, consumers, and stakeholders of the dairy industry. Determining the true economic impact of the disease is difficult at regional and farm level as symptoms are not evident in subclinically infected animals. At present, the virulence, pathogenicity, persistence, and infectious dose of M. avium paratuberculosis are poorly understood, consequently effective paratuberculosis control measures remain obscure. M. avium paratuberculosis is potentially zoonotic with foodborne transmission a public health risk due to a possible causative link with inflammatory bowel disease in humans. A preventive approach is necessary to reduce the presence of this drug-resistant pathogen in dairy herds and subsequently dairy food. The use of inefficient diagnostic tests coupled with the long latency period of infection results in delayed animal culling and trade of asymptomatic animals, leading to regional transmission and increased disease prevalence. To date, there has been limited success at controlling and treating this terminal endemic disease, leading to significant prevalence rates. This study aims to outline the key factors associated with Johne’s disease while outlining its significant impact on the dairy sector.

Comment: The direct financial costs of Johne’s disease (JD) to dairy producers is small relative to diseases such as mastitis. Hence, without financial incentives most dairy producers conclude that the cost of JD control exceeds the cost of the disease. Therefore, few producers implement JD control programs allowing this chronic, infectious disease to continue spreading within and among dairy herds globally. For more on the epidemiology of JD in dairy cattle read this page of our site.

If, however, MAP is recognized as a zoonotic, food-borne pathogen, causing Crohn’s disease and triggering other so-called autoimmune disease like Type I Diabetes Mellitus, the impact on the dairy industry would be huge.

For more on the MAP as a zoonotic pathogen see this page of our website or for patients, visit the Human Para Foundation website.

Related News

Today, October 15, is the publication anniversary of the landmark paper defining Crohn’s disease (1932). As I do annually, I acknowledge this event in Johnes.org news.

Eighty-eight years ago, Burrill B. Crohn, Leon Ginzburg, and Gordon D. Oppenheimer published a paper titled Regional Ileitis – A Pathologic and Clinical Entity in the Journal of the American Medical Association (vol. 99, no. 16, pp 1323-1329, October 15, 1932).  Honoring the importance of this report, the article was later reprinted as a Landmark Article in The Mount Sinai Journal of Medicine (vol 67, no. 3, pp 263-268, May 2006).  We provide the original JAMA article here for users interested in reading this influential publication in its original form.  Note: the reprinted version in the Mount Sinai Journal of Medicine has better print quality.

Comment:  I appreciate history as I grow older.  Also, it is important to read original published reports to avoid misquoting or perpetuating misunderstandings.  Interesting note: As described in Wikipedia, Crohn always preferred the medically descriptive terms "regional ileitis" and "regional enteritis" to "Crohn's disease", but he was not able to prevent the appropriation of his name for the disease. It’s worth noting that Johne's disease is also a regional ileitis affecting ruminants.

Without providing much detail, B.B. Crohn’s article mentions efforts to determine if Mycobacterium tuberculosis was involved in the regional ileitis cases he described including culture for M. tuberculosis, inoculation of lymph node homogenates from five patients into guinea pigs, rabbits, and chickens, and acid-fast staining of tissue sections.  He concludes that M. tuberculosis was not a cause of these cases of regional ileitis.  However, he never mentions the 1913 report by Dalziel or makes any mention of Mycobacterium paratuberculosis or the similarities of regional ileitis in humans to that of cattle, as described by H.A. Johne in 1895. Clearly, Dr. Crohn recognized how the pathology in his afflicted patients resembled that caused by a mycobacterial infection. How might history be different had Dr. Crohn considered the possibility M. a. paratuberculosis (MAP) was the cause?

The picture of B.B. Crohn is credited to Wikipedia.

The second edition of the book titled Paratuberculosis: Organism, Disease, Control has just been published. The editors, Behr, Stevenson and Kapur, have produced a timely follow up to the first book on Paratuberculosis (2010), this new edition is still the only comprehensive text providing both historical context and the latest developments in the field. Examining the epidemiology of paratuberculosis, the organism that causes the disease, and practical aspects of its diagnosis and control, it also addresses the link between paratuberculosis in the food chain and human health implications, including Crohn's disease. The 438 page book contains 23 chapters written by the leading world experts in paratuberculosis (Johne's disease). It is available from Amazon for e-readers for US$147.25 or from Google for US$124.00. The hard cover version has not yet been released for sale but can be pre-ordered from Amazon for US$155.00

Antonio Foddai and Irene Grant from the Institute for Global Food Security, School of Biological Sciences, Queen’s University Belfast, Belfast, Northern Ireland have created a novel assay to quantify viable MAP in milk (patent pending).  Their report, titled “A novel one-day phage-based test for rapid detection and enumeration of viable Mycobacterium avium subsp. paratuberculosis in cows’ milk” appeared September 24 in the journal Applied Microbiology and Biotechnology [Open Access].

In this assay phages (viruses that infect bacteria) are used to both concentrate MAP and to then infect and lyse MAP, allowing for final detection and quantification by qPCR. The total assay time is roughly 7 hours, faster than other phage-based assay systems. The key to the assay is the binding orientation of the phage. The head is bound to the paramagnetic bead allowing the tail to bind to MAP. After binding, the phage then lyses the MAP organism making its DNA available for detection by qPCR.

Diagram of a similar phage from ViralZone.

Abstract

Bacteriophage-based methods for the rapid detection of viable Mycobacterium avium subsp. paratuberculosis (MAP) in veterinary specimens are a recent addition to the Johne’s disease diagnostic toolbox. Here, we report the use of D29 mycobacteriophage-coated tosylactivated paramagnetic beads to capture and concentrate MAP cells from samples (termed phagomagnetic separation, PhMS) and then naturally lyse viable MAP cells (from the inside out) to provide DNA for IS900 qPCR purposes. Transmission electron microscopy confirmed that D29 phages had bound to beads in the correct orientation and that the phage-coated beads captured MAP cells from a suspension. During test optimization, conventional IS900 PCR results were used to subjectively assess the effect of different phage:bead coating ratios, differing amounts of coated beads during PhMS, optimal incubation time post-PhMS to obtain maximal MAP DNA, and the potential benefit of a brief heat shock (55 °C/1 min) prior to IS900 TaqMan qPCR. The limit of detection 50% (LOD50%) of the optimised PhMS-qPCR assay was 10.00MAP cells/50 ml milk (95% CI 1.20–82.83). Finally, in order to demonstrate the new assay’s ability to detect viable MAP in naturally contaminated milk, bulk tank milk samples from 100 dairy farms were tested. Forty-nine (49%) of these tested PhMS-qPCRpositive, with viable MAP numbers detected ranging from 3–126 MAP/50 ml. The novel PhMS-qPCR assay is a sensitive, specific and easy-to-apply phage-based assay for viable MAP, with potential application for milk surveillance or diagnosis of Johne’s disease.

Comment: No other assay system can claim the ability to quantify such low numbers of viable MAP in milk in such a short time. I predict that this assay will reveal that there is far more MAP in raw milk than previously recognized. Hopefully this novel technology also can be applied to other types of clinical samples, e.g. blood samples from Crohn’s disease patients. For more about D29 phages see this Wikipedia page.

In the second of two JD articles, veterinarians Pete Orpin, Dick Sibley and Karen Bond provide an excellent overview of UK’s national program to control Johne’s disease. The principles apply to all nationally coordinated efforts facilitated by specially qualified veterinarians.

The article appears in the UK magazine In Practice. The magazine publishers have generously provided readers of Johnes.org news exclusive free access to the full article.

As stated in the summary of their article:
Any JD management plan should meet the principles of any good herd health plan, in accordance with the VESPA acronym used in the British Cattle Veterinary Association’s health planning training:

• Valued – it must engage the farmer and all the staff;
• Effective – it must be robust and cover all components of the strategy;
• Specific – it has to be detailed to fit with the specific management and husbandry of the farm;
• Practical – it has to be deliverable by the farm and the staff, within the resource limitations;
• Agreed – it has to be agreed by all involved as a practical and deliverable plan.

Here's an example of the messaging in this important article:

About the authors:

Pete Orpin qualified from the University of Bristol in 1983 and worked as a farm vet within the Park Vet Group in Leicestershire for 35 years before retiring. He is a founding member of Action Group Johne’s and chair of its technical group, and is a director of Myhealthyherd.

Dick Sibley qualified from the University of Bristol in 1977 and is currently a practicing vet in Witheridge, Devon. A founding member of Action Group Johne’s and director of Myhealthyherd, he has had a long interest in the practical management and control of infectious diseases, including bovine viral diarrhea, tuberculosis and Johne’s disease.

Karen Bond qualified from the University of Glasgow in 2000 and works as a veterinary adviser for National Milk Records, where she has a special interest in the testing and management of infectious disease. She is currently undertaking a PhD in Johne’s disease transmission on dairy farms.

Comment: I wish to thank the publisher, BMJ, for granting access to these excellent articles on Johne’s disease published in In Practice, a publication of the British Cattle Veterinary Association.

Veterinarians Dr. Pete Orpin and Dr. Dick Sibley and Dr. Karen Bond (PhD student) provide an excellent overview of Johne’s disease, targeted at dairy farmers and veterinarians. The article appears in the UK magazine In Practice. The magazine publishers have generously provided readers of Johnes.org news free access to the full article. The article nicely describes the disease, its importance, and measures to control it with lovely graphics. It also briefly describes UK’s national Johne’s control program, which has many similarities to that of the US.

The second article of the series goes into more depth about on-farm control measures and the UK’s National Johne’s Management Plan. It will be featured in coming news stories on this website.

About the authors:

Dr. Pete Orpin qualified from the University of Bristol in 1983 and worked as a farm vet within the Park Vet Group in Leicestershire for 35 years before retiring. He is a founding member of Action Group Johne’s and chair of its technical group, and is a director of Myhealthyherd.

Dr. Dick Sibley qualified from the University of Bristol in 1977 and is currently a practicing vet in Witheridge, Devon. A founding member of Action Group Johne’s and director of Myhealthyherd, he has had a long interest in the practical management and control of infectious diseases, including bovine viral diarrhea, tuberculosis and Johne’s disease.

Dr. Karen Bond qualified from the University of Glasgow in 2000 and works as a veterinary adviser for National Milk Records, where she has a special interest in the testing and management of infectious disease. She is currently undertaking a PhD in Johne’s disease transmission on dairy farms.

Comment: I wish to thank the publisher, BMJ, for granting access to these excellent articles on Johne’s disease published in In Practice, a publication of the British Veterinary Association.