Minimize Risk...Reduce Impact...Eliminate Johne's

Knowledge Gaps

Background
Process
	Animal Level Knowledge Gaps
	Bacterial and Cellular Level Knowledge Gaps
	Economic Knowledge Gaps
	National Policy Knowledge Gaps
	Transmission/Effectiveness of Control Knowledge Gaps
	Diagnostic Test Knowledge Gaps
Appendix 1
	Animal Level Knowledge Gaps
	Bacterial and Cellular Knowledge Gaps
	Economic Knowledge Gaps
	National Policy Knowledge Gaps
	Transmission/Effectiveness of Control Knowledge Gaps
	Diagnostic Test Knowledge Gaps

Background

The Johne’s disease Strategic Plan (USAHA-2004, Resolution 21) lists five Objectives in the Executive Summary as published in the Proceedings of USAHA. Objective 3: Close gaps in Knowledge about Johne’s Disease. The 2003 National Research Council’s report entitled “Diagnosis and Control of Johne’s Disease” under Conclusions and Recommendations, page 121 (Conclusion # 4) reported: “There are significant gaps in knowledge about some areas relevant to control.” The Knowledge Gaps group of the National Johne’s Working Group was formed in February 2005 to help define and prioritize the knowledge gaps that are perceived to impede the full development of the National Johne’s disease program in keeping with the recommendations of the NRC report and the Johne’s disease Strategic Plan.

This summary is based on the voting by members of the Johne’s Disease Knowledge Gaps sub-group of the National Johne’s Working Group and reflects those items deemed of highest priority by the group. The appendix outlines the topics and questions raised during the conference calls. Each call was hosted by USDA-VS and the first call was held on February 7, 2005. Approximately 25 calls (about one hr each) were held over the nearly six months of periodic phone calls. Members of the Ad hoc Knowledge Gaps group included:

Invited participants (32) for the Knowledge Gaps (KG) conference calls included:

Adaska, John	Banantine, John	Carter, Mike	Collins, Mike
Camacho, Mark	Davis, Bill	Gardner, Ian	Garry, Frank
Friendshuh, Keith	Harris, Beth	Honstead, John	Hoving, Ernest
Johnson, Todd	Kapur, Vivek	Leids, Pepi	Lombard, Jason
Moore, Dale	Patton, Beth	Payeur, Janet	Roussel, Allen
Robb-Austerman, Sue Lee	Schleicker, Heidi	Shulaw, Bill	Stabel, Judy
Stehman, Sue	Sweeney, Ray	Surber, Rachel	Talaat, Adel
Wells, Scott	Whitlock, Bob	Wu, Ching Ching

Process [Back to top]

Members of the KG group submitted specific topics about Johne’s disease that lacked full understanding to develop a comprehensive listing of those topics, they are shown in the appendix. Then, a group leader volunteered (shown below) to coordinate voting and prioritization of the gaps in each of the category areas. Each group leader then prepared a draft describing the knowledge gaps for that category. Knowledge gap categories were not prioritized. This summary document will be distributed to JDIP, USDA-ARS, USDA-NVSL, USDA-SEAH and USDA-VS for their review and response about how each organization has developed field studies and/or research projects to fill these knowledge gaps.

1. Animal Level Knowledge Gaps

Group Leader: Adel Taalat [Back to top]

The overall results of the animal level knowledge gaps survey indicates that shedding of M. paratuberculosis is a major problem for JD with little information is known so far on the animal level. More resources are needed to investigate issues related to bacterial shedding during different stages of infection. Issues related to the initial infection and the use of chemicals/antibiotics to control the disease are also important to define effective control measures against JD.

2. Bacterial and Cellular Level Knowledge Gaps

Group Leader: Ching Ching Wu [Back to top]

The most important questions to be addressed are the interaction/survival/ propagation of M. paratuberculosis (MAP) outside of the host. “What are the factors affecting the viability of MAP in specimens (fecal, tissues) or environmental and their impact on management applications?”, and “How does treatment of manure/environment/contaminated products by chemical/ composting/drying/irradiation affect the viability or survival of MAP?”, are considered very important factors for the control program and are questions asked frequently by farmers and veterinarians, yet very little research has been done so far. Identifying and understanding effective treatment methods for MAP outside animal will lead to successful control measures and provide good and immediate return. Sensitive and accurate direct fecal detection and quantitative assays are critical tools in accomplishing these goals.

The second tier of importance centers on the concerns regarding the JD Control Program is the variability of protocols used by various diagnostic labs in the U.S. to isolate and identify M. paratuberculosis. Thus, to help ensure that lab results are comparable across the United States, we must agree on definition of organism (bacteriological and molecular; phenotypic and genotypic characterizations) so that there are scientifically based guidelines provided amongst labs in determining and confirming isolation and levels of infection. This common definition of the agent can be applied to all other studies and diagnostic reports.

The third tier of significance centers on how MAP invades the intestinal tissue after an oral infection, a problem that has no quick fix. Even though efforts to address these questions may take a longer time, the understanding of bacterial and host cell interactions is critical and essential in generating strategies to block uptake and provide a more efficient eradication means than by treating the contaminated environment after the uptake, propagation, and shedding of MAP in high numbers. Understanding the host- bacterial interactions could also aid in the development of better diagnostics and vaccines. The following areas are important and in need of investigation: What are the portals of entry other than M cells? What are the early molecular events between bacterial and host (FAP-fibronectin/integrins or virulence factors) that leads to the establishment of infection? Can one prevent infection by blocking the interactions? How does MAP invade the calf intestinal tissue, and evade host immune systems (i.e. survive in macrophage) and disseminate following the initial oral infection? How and why are the bacteria shedding intermittently from infected animals (host or bacterial factors)? What host or bacterial factors contribute to persistent infection and disease progression?

Two last items of importance centers on the silent phase of MAP infection. Due to the inability to diagnose infection at this stage, the silence phase remains a big challenge for our control program. We can only detect MAP from calves older than 1.5 to 2 years of age even though we know they have been exposed to MAP immediately after birth. For a nationwide JD control program to be effective, we need to know more about the silent phase. What are the roles of immune cell during the silent phase or mediating protection? Which antigen elicits protective immunity during the silent phase? This information is essential for the development of better diagnostics and vaccines.

3. Economic Knowledge Gaps

Group Leader: John Adaska [Back to top]

The most important questions to be addressed are concerned with the absolute and relative benefits or returns, costs and cost-effectiveness of the management strategies that are currently recommended in the VJDCP. Many of the current recommendations make good scientific sense but have not been tested against real world economics and against a variety of herd sizes and overall management objectives. We may find that, although not currently recommended, feeding pooled colostrum or using off-site heifer raisers may make good economic sense in some situations. Conversely, it may not make good economic sense to test individual animals in herds of low prevalence or in herds that cull animals at an early age.

The second tier of questions are less uniform but are concerned with the economics of vaccination and testing. The main point is whether there is some prevalence at which vaccination for JD is economically justifiable and also if there is some low prevalence point at which a shift in testing from individual animals to environmental testing or a discontinuation of testing altogether makes economic sense without allowing an increase in the JD prevalence. Included in this group of questions is what costs are associated with various JD prevalence levels. We assume that a 50% prevalence level is more costly than 10% prevalence and argues for a more aggressive approach to control but one with 5% prevalence level and one with 1% prevalence may have the same costs and should have the same degree of concern.

One of the last two items considered important concerns what motivates producers to install practices that control JD. This is a question of behavior and attitudes. For some herds it is almost entirely perceived economic return that drives the implementation of management changes while in other herds it is the pride of ownership and pride in “doing a good job”. For a nationwide voluntary JD control program to be effective we need to understand these motivations.

Lastly, there is a need for a comprehensive understanding of the costs of JD in all types of beef herds. Obviously the data from dairy cattle is cannot be extrapolated to beef cattle given that lost milk production is not an issue except as it affects weaning weights and given that the major management tool, keeping young stock away from adult cattle feces, is managed by stocking density and not by physical separation.

4. National Policy Knowledge Gaps

Group Leader: Mike Carter [Back to top]

Foremost on the list by an overwhelming majority is the question, “Is MAP a Zoonosis?”. As evident from the comments this is a key issue in determining 1) the direction of the national JD control program and 2) the level of involvement USDA should maintain and 3) what level industry should manage the disease problem themselves. Once this question is answered, the program priorities and the questions needing answers to address those priorities can shift dramatically. Other questions among the food safety items did not rank high presumably because this question must be answered first before significant resources should be devoted towards the other questions of public health.

The next highest priority is the need to determine the current prevalence in the US/States. Most felt that this is a necessary starting point to be able to measure the success of the national and State programs. A related item, “How can we best monitor changes in prevalence?” received a fair number of votes which may represent a split in potential votes for the question above since some voters viewed the question as where do we need to be (able of monitor success/failure) versus where are we starting.

A third key point is: “What would compel producers to control JD on their farm?”. Comments appeared to be based on the assumption that if MAP is not a zoonosis, then participation should not be driven by regulatory means but by voluntary participation of producers. Similar items ranked in the top ten; “What is industries role in JD control?”, “What are the benefits of the program?”, “Would industry support a mandatory program without MAP being a zoonosis?” These question support the idea that what drives producer participation in a voluntary program is a key concern to the national and State programs and needs to be determined if the program is going to succeed long term in the absence of public health concerns, regulatory requirements, and significant Federal or State dollars.

Similar to the voting of the producer participation questions is that of the use of vaccination to control JD. Ranking fourth was the question “Can vaccine be used as a tool to control or eradicate JD?” Related questions emphasize vaccination. “How would the widespread use of JD vaccine impact tuberculosis surveillance and eradication?”, “Can vaccinations with appropriate testing accelerate control of the disease?”, “Does vaccination control JD as attributed to the vaccine or is it concurrent management changes?”, and “Can a new candidate vaccine provide protection for bacterial shedding?” all indicates that the group feels much more work should be done in this area on JD control and could benefit the program.

5. Transmission/Effectiveness of Control Knowledge Gaps

Group Leader: John Adaska [Back to top]

Four major areas were brought up in regards to transmission and control of JD; 1) Effectiveness of Control, 2) In-Utero and Maternal Transmission, 3) Environmental Issues, 4) Susceptibility and Exposure Risks. All categories raise questions of equal priority and an ordered priority was not established.

Key items for effectiveness of control came up as; “Do the recommended management practices work?” and “Can we quantify the currently accepted risks for transmission of JD as well as the effectiveness of the management practices recommended to mitigate them? An additional need of the national control program is the need to validate model strategies or control programs that are cost effective and are design to meet specific farm needs and objectives.

Along the lines of maternal transmissions, key issues were determined to be identifying the risk of in-utero infection of neonates from infected dams and what is the implication for the onset and rate of progression? Another point of concern is the significance of feeding contaminated colostrum and milk on transmission and is it reasonable to restrict feeding based on shedding levels or serology results. Focusing on beef cattle, the question arose about is the role/importance of dam-to-calf in transmission in range cattle.

The issues that received the greatest share of votes involved the risks associated with spreading contaminated manure on forages/pasture to be grazed/harvested and what factors influence the ability of the organism to be passed on to uninfected animals? A related environmental question involved measuring the MAP environmental load and how does the MAP load relate to success of control interventions?

When looking at susceptibility and the progression of disease, age-dependent dose related response curves are needed to clarify the magnitude and significance of age related susceptibility or resistance to infection. A look at the degree to which horizontal transmission occurs in different age groups is also needed along with the risk of clean replacement heifers purchased into a herd with moderate to low prevalence of JD. With the increase use in calf ranches, what risks are there in heifer rearing operations where animals from different status herds are commingled?

Characterizing the natural transmission risk and determining what proportion of light infected cattle progress to increased shedding or clinical disease, what is shedding pattern over time and how does it correlate with serology needs to be addressed. And finally what is the risk of maintaining MAP shedders in the herd, low vs. high, when other management is in place to reduce exposure?

6. Diagnostic Tests Knowledge Gaps

Group leader: Ian Gardner [Back to top]

Seven questions scored in the top of 25 items. The top scorer was to improve the fecal PCR protocol to make it cheaper, faster, more sensitive and quantitative. This was follow closely by determining which diagnostic tests are best for specific questions/purposes and to provide explicit guidelines for using these tools. This also falls in line with evaluating the roles of new diagnostic tests such as CMI, FP, FASC cell sorters, standard and quantitative PCR and skin tests. Looking for methods to concentrate MAP in clinical samples such as feces, tissues, environment, milk and water was ranked high as was determining if CMI tests can detect infected animals at an early age.

Rounding out the top items selected by the group included validation of optimal testing and sampling protocols (incl. pooled testing and use of environmental samples) to facilitate screening and monitoring of large cattle herds and how to differentiate passive shedders from primary infections.

One last item that score high is to look as what panel of M. paratuberculosis antigens is best for detection of the maximum number of infected dairy cattle with a specificity >99% and are these same antigens the best for beef cattle or other animal species?

Appendix 1

Items discussed (not ranked) [Back to top]

Animal Level Knowledge Gaps [Back to top]

Resistance

What is the infectious dose for cattle and various other species?
What is the potential for cross species transmission for the more host adapted strains?
How does the infectious dose change with age (ie. age-related resistance)?
Within the bovine species, is there a familial (genetic) resistance to infection?

Progression of infection

What proportion of animals become; recovered, asymptomatic shedders, “super shedders”, clinical?
What determines the rate and extent of progression? (dose, age of exposure, host genetics, nutrition, vaccination, antibiotic intervention such as monensin, strain of MAP, climate)

Bacterial and Cellular Level Knowledge Gaps [Back to top]

Interactions/survival/propagation of M. paratuberculosis (Map) outside of the host

What are the factors affecting the viability of Map in specimens (fecal, tissue) or environment and their impact on management applications?
How does treatment (of manure, of environment, of contaminated product) (by chemicals, by composting, by drying, by irradiation) affect viability (survival) of the agent?
How many forms does Map take? (Vegetative? Dormant? Viable but non-culturable? Protease-resistant? Spheroplastic?) How are each defined or measured?
Does Map exist in a viable but uncultivable or marginally cultivable state as suggested by Whittington? If present, can this state exist in the host as well as in the environment?
What is the role (if any) of cell wall deficient variants of Map in JD?
Does Map replicate outside of the host?

Parameters for identifiying an unknown bacterial isolate as M. paratuberculosis (Map)

What are the Map-phenotypic or genotypic characteristics that define this species?

How does Map invade intestinal tissue after oral infection?

How do the Map bacilli evade the host immune system for long periods of time after infection?
How (and why) is the bacterial shedding from infected animals intermittent? Are there host factors, bacterial factors or both that control shedding?
What host factors contribute to bacillary entry into the persistent infection state?
Which receptors are used to enter M cells, gut epithelial cells, macrophages and dendritic cells? e.g. CD209 (DC-sign), CD206 (mannose receptor)
What are the bacterial and host cell interactions? (FAP-Fibronectin/intgrins or ?
What are the early molecular events that lead to establishing infection during the first few weeks post-infection?

How does Map survive in macrophages and dendritic cells?

Modulation of cytokine/chemokine gene activation? Block in phagosome lysosome fusion?

What host factors contribute to persistence and disease progression?

Do IL-10 and TGF-ß, secreted by infected macrophages and dendritic cells, down-regulate immune control of Map?
What are the virulence factors contributing to the persistence of Map in animal tissues?
What are the mediators that contribute to the granulomatous inflammation that occurs during JD?
Is weight loss in JD due to disruption of the absorptive epithelial surface, or release of mediators (e.g. TNF-α or others) that alter host physiology and energy balance?

How does the immune system control infection during the silent phase?

What roles do dendritic cells and macrophages play in sustaining a type 1 immune response dominated by secretion of IFN-γ?
What are the roles of CD4, CD8, γδ T cells and NK cells in mediating protection?
Which antigens elicit protective immunity during the silent phase of disease?

Can blocking the binding of Map to intestinal cells prevent and reduce infection?

What bacterial-cellular interactions provide this potential?
How can Map invade the calf intestinal tissue and disseminate following the initial oral infection? What are the portals of entry other than M cells, if any?

Application of genotyping to molecular epidemiology and disease transmission

Which region of the genome is the most appropriate to use for genotyping (e.g. various genotyping methods not exist for Map-AFLP, Multi-locus short sequence repeats, IS900 integration loci, RFLP, etc.?)
Are there other regions that would be better to use for molecular epidemiology studies?
How can genotyping/molecular epidemiology be applied to study disease transmission between/within herds?

Economic Knowledge Gaps [Back to top]

Individual-cow Assessment

At what age does the average JD infected cow start to show decreased value (production, cull value, etc) relative to negative herd mates?
What is the magnitude of the reductions in milk production and reproductive performance etc for a range of herd production types?
Will someone who culls cows more aggressively and therefore at a younger age be able to minimize the economic impact of JD?

Herd-level Assessment

At what JD prevalence, is JD vaccine for the herd, economically justified?
What are the economic values/costs associated with various herd levels JD prevalence? Within this question there needs to be allowance for different disease stages within a given prevalence level e.g. 90% of infected cows seropositive but not clinical vs. 50% clinical.
What are the costs associated with JD in commercial beef herds? If most beef cattle are marketed for slaughter at a young age does JD have an economic impact on beef herds?

Interventions and Management

What are the most cost effective methods to reduce or prevent transmission of JD in a herd?
What are the real costs associated with recommended management changes? (Such as buying a pasteurizer, hiring more help in order to staff maternity pen 24/7, feed management, non-use of feed refusals, fresh water flush systems, etc).
What are the benefits of recommended management changes on reduction of JD incidence – individually and for the entire “best management practices” package?
What are the non-JD economic returns that occur when JD management changes are introduced?

VJDHSP

At what point (heifers sold per year) will a status level IV herd benefit economically?
How to better capture the economic benefits of becoming a status herd?
How to encourage milk cooperatives to pay premiums for milk from status herds?
How to enhance the sale value of replacement heifers from Status herds?

Testing

Is environmental JD testing followed by management changes of economic value in JD positive herds?
In herds with low prevalence is there a significant enough acceleration toward 0% prevalence to justify continued testing or should the owner rely solely on management at some point?
What are the economic risks of discontinuing testing in a low prevalence herd?
In herds with low prevalence does pooled testing make more/less economic sense than serology?
What are the costs of failing to identify “newly infected” animals or clusters of such animals vs. continuing to test in low prevalence herds?

Other Issues

Is economics the only thing that motivates producers to implement good management practices to control JD?

National Policy Knowledge Gaps [Back to top]

Vaccination

Can vaccine be use as a tool to control JD? Can vaccine be use as a tool to control JD?
Does vaccination with testing and appropriate management accelerate progress toward a low level status in fewer years?
With widespread use of JD vaccine, what would be the impact on TB surveillance? With widespread use of JD vaccine, what would be the impact on TB surveillance?

Current Vaccine

Does vaccination (Mycopar) control JD or is efficacy attributed to the vaccine by some people primarily due to concurrent management changes that are made in the herd?
Does vaccinating older animals with Mycopar have any effect on infection status/shedding? Does vaccinating older animals with Mycopar have any effect on infection status/shedding?

New Vaccines

Can new vaccine candidates provide protection from bacterial shedding?
Can we develop a genetic vaccine or vaccine adjuvants with higher protection levels than Mycopar?

Zoonosis

Is MAP a zoonosis? Does M. paratuberculosis cause Crohn’s or any other human disease?
Are humans susceptible to M. paratuberculosis infection? If so, at what dose and is there an age-dependence to susceptibility?
Can the level of susceptibility of humans to M. paratuberculosis be estimated using nonhuman primate challenge studies?

Food Quality/Safety

What level of raw food product contamination results from M. paratuberculosis infections on dairy or beef farms?
How many M. paratuberculosis per mL of milk is tolerable in the retail pasteurized milk supply of the USA?
What level of contamination with MAP exist in public waters? What is the fate of M. paratuberculosis that contaminate water destined for human consumption?
Will chlorination kill M. paratuberculosis or reduce viable numbers to a level below that capable of infecting humans?
If MAP can be found in raw meat products, how sensitive is MAP in raw meat to cooking temperature?
How effective is irradiation in neutralizing/killing MAP infectivity/viability?
How can we effectively stop the test and slaughter practice? Or, how much data is needed to conclude that this is not a wise food safety practice?

Regulatory Veterinary Medicine

Regulation

What is the justification for regulation of paratuberculosis?
Will the industry support mandatory control of JD if it's not a zoonosis? Will the industry support mandatory control of JD if it's not a zoonosis?
Will the industry tolerate mandatory tagging and removal of test-positive cattle from the food chain? If so, what tagging system is will be accepted by the industry and public?
What are the benefits of the national control program?

Testing

What is the current prevalence of JD in the US/ States?
How can we best monitor changes in prevalence?
Can DHI testing centers offer testing services for paratuberculosis, and if so, what requirements must they meet in reporting test-positive animals?
Why can MAP infection exist in some herds without much shedding, antibody response or clinical expression and yet when feeding or other herd Why can MAP infection exist in some herds without much shedding, antibody response or clinical expression and yet when feeding or other herd "stressors"

Trade

Should national/international regulations for animal testing for paratuberculosis be changed?
What are the USA's major 'bovine and bovine products' trading partners doing with JD in their countries that might lead to economically disadvantageous phyto-sanitary trade barriers being put in place against US cattle and cattle products in the near/mid future?

Producer Participation

What would compel producers to control JD on their farm?
What is the industry's role in driving JD control, vs. government, private vets, and university researchers, extension people, etc.?
What level of “producer incentives” is acceptable for a long term voluntary program? Should incentives be driven/handled by milk and meat processors? How much of a milk or meat “premium” would it take to be an adequate producer incentive?
Why do dairy producers not believe paratuberculosis experts who tell them that prevention and control of JD are cost-effective?
Do cattle health and quality assurance programs with herd status programs as models increase participation?
How many farms use best management practices conducive to JD control without official enrollment on the JD program?

Transmission/Effectiveness of Control Knowledge Gaps [Back to top]

Effectiveness of Control

Do we know if the management practices we are recommending actually work? Do we know if the management practices we are recommending actually work?

In-Utero, Maternal Transmission, Genetics

Is there any level of infection status of the dam, or of the herd, that would justify recommending culling offspring as an effective control measure? Are there increased risks associated with animals infected in utero compared to those infected by the fecal-oral route such as onset and level of shedding or rate of progression to clinical disease that may have implications for control?
Role/importance of dam-to-calf in transmission in beef (range) cattle.
Genetic resistance/susceptibility

Role of Colostrum and Milk in Transmission

What is the role and significance of feeding contaminated colostrum and/or milk in transmission and is it a reasonable and effective practice to restrict feeding based on the infection or serological status of the dam? What is the role and significance of feeding contaminated colostrum and/or milk in transmission and is it a reasonable and effective practice to restrict feeding based on the infection or serological status of the dam?

Environmental Issues/Sources for Transmission

Forages/Pasture

Transmission risk associated with spreading contaminated manure on forages/pasture to be grazed/harvested the same season and what factors influence e.g. timing of application relative to harvest/grazing, method and length of manure storage/treatment, climate/season of application, ensiling, drying, length of storage and prevalence of infection in the herd.

Wildlife

What role does wildlife play in the maintenance of M. paratuberculosis and what isthe exposure risk to domestic livestock from non-ruminant and ruminant wildlife.

Water

Determine the prevalence and exposure risk of viable M. paratuberculosis in potable-water supplies, streams, ponds, and other bodies of water with potential for contamination.

Facilities

Role of the maternity pen/environment in transmission?

Other

Role/importance of the bull in transmission in beef (range) cattle.
How to best measure and quantify the environmental MAP load in large and small dairies, how does it relate to the success of control interventions, and can it be used as a monitoring tool to identify trends.
Does composting kill MAP?

Susceptibility, Progression of Disease and Exposure Risk/Infectivity

Susceptibility

Age-dependent dose related response curves are needed to clarify the magnitude and significance of age related susceptibility or resistance to infection and the degree to which horizontal transmission occurs in different age groups: What risk is there for adult cow transmission to other adult cattle? Age-dependent dose related response curves are needed to clarify the magnitude and significance of age related susceptibility or resistance to infection and the degree to which horizontal transmission occurs in different age groups: What risk is there for adult cow transmission to other adult cattle? Will clean replacement heifers purchased into a herd with moderate to low prevalence of JD remain clean? What risks are there in heifer rearing operations where animals from different status herds are commingled?
Why are some calves able to resist/eliminate MAP infection even after oral exposure and how often does that happen?

Progression of Disease

Characterize the natural transmission risk and risk of progression of infection in light shedders: Characterize the natural transmission risk and risk of progression of infection in light shedders: What proportion of light infected cattle progress to increased shedding or clinical disease, what is shedding pattern over time and how does it correlate with serology?
Are there triggers/stressors that can cause the pattern of disease progression within a herd to change and can this have implications for control?

Exposure Risk/Infectivity

What is the risk of maintaining MAP shedders in the herd, low vs. high, when other management is in place to reduce exposure?
Characterize and quantify the ‘natural’ infective dose/exposure through epidemiologic modeling – e.g. determine relative risk or proportion of animals that develop detectable infection as a consequence of 'measured' early exposure. Characterize and quantify the ‘natural’ infective dose/exposure through epidemiologic modeling – e.g. determine relative risk or proportion of animals that develop detectable infection as a consequence of 'measured' early exposure. For example, calves born in contact with infected cow (low vs. high shedders) for 12 hrs and fed her colostrum/milk.
Determine the effects of chronic, low-level exposure on infectivity and the outcome of infection.
What is the most important source of exposure (manure, colostrum, milk, in utero) that leads to new infections and when does it occur (age)?

Prophylactic Interventions

Addition of antimycobacterial antibiotics to MAP contaminated colostrum or prophylactic treatment of calves at some strategic age.
Prevention of MAP uptake in the gut i.e. Biomos, competitive exclusion, oral antibody
Improve local/mucosal immunity in the neonatal calf e.g. Improve local/mucosal immunity in the neonatal calf e.g.
Role of monensin in clinical signs, shedding, infection, diagnostic sensitivity of culture

Control of JD

Identify and validate several model strategies or control programs for JD that are cost effective and are tailored to specific farm needs/goals/objectives.
Identify and evaluate model test strategies that are most cost effective and meet specific herd needs/objectives.

Diagnostic Test Knowledge Gaps [Back to top]

Organism Based Diagnostic Tests

Solid culture media: factors affecting sensitivity of culture (role of monensin, effects of freezing and storage of fecal samples, faster growth in culture and improve decontamination protocols)
Liquid culture - which liquid culture medium is most sensitive?
How to enhance recovery of Map from shelf milk?
Methods for concentration of Map in clinical samples (feces, tissues, environmental, milk Methods for concentration of Map in clinical samples (feces, tissues, environmental, milk &
How to differentiate passive shedders from primary infections
Classification of fecal shedding levels in an animal, how reflected in our testing criteria and quantitative test needed to reflect shedding level
Improve the PCR fecal protocol -- make it cheaper, faster, more sensitive and quantitative

Antibody Based Diagnostic Tests

What panel of M. paratuberculosis antigens is best for detection of the maximum number of infected dairy cattle with a specificity >99%? Are these same antigens the best for beef cattle or other animal species?
How to best detect ELISA negative, heavy fecal shedders?
Correlation of ELISA and culture results at the individual animal level and to use of ELISA to rule in or rule out animals for culture
Are cell wall antigens vs. secreted protein antigens better targets for detection of infected animals?

CMI Based Tests

Are animals that demonstrate a CMI response those that are infected or those that have controlled the infection? To manage JD infection, should they be culled or kept?
Can infected animals be detected by CMI tests at an early age (ie. 6 months)?

Herd Diagnostics

What is the most cost-effective method to determine herd infection?
Validation of optimal testing and sampling protocols (incl. pooled testing and use of environmental samples) to facilitate screening and monitoring of large cattle herds.
What testing protocol best assesses the herd bio-burden on MAP in large and small dairies?
How best to estimate JD prevalence in low, mid and high or unknown prevalence herds?
Better tests to detect JD in low prevalence herds

Diagnostic Tests (General):

What are the “best” diagnostic tests for specific questions/purposes? Provide explicit guidelines for how to best use these tools
Role of new diagnostic tests: CMI, FP, FASC cell sorters, quantitative PCR, std PCR, skin tests
How to identify infected cows earlier in their infection and to detect disseminated infection?
Which tests will differentiate cattle resistant to MAP infections (or clinical disease) compared to susceptible cattle?
What testing methods should be used to test cull cattle for JD?

Identification of Unknown Bacterial Isolate as M. paratuberculosis

What is the definition of M. paratuberculosis - phenotypic characteristics or genotypic characteristics? If the latter, then what are the markers that define this species?

Ovine and Caprine Paratuberculosis

Develop and validate sensitive and specific serologic and fecal culture protocols for use in sheep & goats.

November 2, 2005

A cooperative effort of the National Institute for Animal Agriculture and USDA, APHIS, Veterinary Services,
in association with the National Johne's Working Group & United States Animal Health Association