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Mycobacter ium avium subsp. Paratuberculos is is
a wel l establ ished etiolog ical agent o f JD(also
know n as par tubercu los is)
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Importance
Paratuberculosis is a chronic mycobacterial disease characterized by :
1. i r revers ib le wast ing
2. diarrhea and3. death from cachexia (wast ing sy ndrome) in rum inants.
caused by the obligate pathogen Mycobacterium avium subsp.Paratuberculosis (MAP).
Subclinical carriers are estimated to produce 15-16% less milk
no effective treatment.
M. avium subsp.paratuberculosis has also been implicated as a possible
cause of Crohns disease in humans
Control programs for paratuberculosis have been established in somenations including Australia, Norway, Iceland, Japan, the Neth-erlands andthe United States. (not in india)
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Etiology
Paratuberculosis results from infection byMycobacterium avium subsp.paratuberculosis
acid-fast rod previously known asMycobacteriumparatuberculosis andM. johnei
Some strains ofM. avium subsp.paratuberculosispreferentially infect specific hosts
The two main types (distinguished by restriction
fragment length polymorphisms RFLP)1. are the Type II or C strains, found in cattle
2. type I or S strains, found in sheep
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Species Affected
Paratuberculosis affects domesticated and
wild ruminants including cattle, sheep, goats,llamas, alpaca, camels, moose, elk, bighorn
sheep, buffalo, deer and reindeer.
Disease has been reported in wild rabbits,
nonhuman primates and pigs also.
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Geographic Distribution
Paratuberculosis can be found worldwide
Only Sweden and some states in Australiaare proven to be free of this disease
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Transmission
In ruminants
1. transmitted by the fecaloral route.
2. from colostrum, milk, udder, and the male andfemale reproductive tracts
3. Transmission can occur on fomites, and insectsmay act as mechanical vectors
Young animals are most susceptible to infection1. Get infected when they drink milk or colostrum.
In utero infections may also be seen.
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M. avium subsp.paratuberculosis is resistant
to environmental conditions and can survive
on pastures for more than a year
Viable bacteria have also been found for up
to a week in bovine urine, and for up to 8-11months in bovine feces.
In one study, this organism survived for as
long as nine months in pond, tap or distilled
water;
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Clinical Signs
Three stages of Johnes disease in cattle:
STAGE 1- Infected but showing no clinical signs and
not shedding MAP. Typically this stage occurs in
calves, heifers and young stock less than two years
of age and many adult animals exposed to small
doses of the disease-causing organism. This stage
progresses slowly over many months or years to
Stage II.
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Stage 2- Infected, shedding MAPbut
showing no clinical signs. Typically this stageoccurs in older heifers or adults. These
animals pose a major, but often hidden,
threat for infection of other animals through
contamination of the environment.
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Stage 3- Shedding MAPand showing clinical signs.
The onset of Stage III is often associated with a
period of stress, such as recent calving.
Cattle at this stage have-
1. intermittent, watery manure.
2. Animals lose weight and gradually drop in milk production but
continue to have a good appetite.
3. Most of these animals are shedding billions of organisms
4. In the final and terminal aspects of Stage III of the fatal disease,
animals become emaciated with fluid diarrhea and developbottle jaw.
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Diarrhea: an early sign of Johne's disease
in cattle
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Signs of Johne's
disease include
diarrhea andrapid weight loss.
Typically,
affected animals
remain brightand alert, without
fever, and eating
well.
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"Bottle jaw", also calledsubmandibular edema,
is a sign very typical ofJohne's disease. Thecause of bottle jaw is alack of protein in theserum, particularly
albumin, due to thedecreased function ofthe intestine. Johne'sdisease is a protein-losing enteropathy.
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The last portion of the smallintestine, or ileum, shown inthe upper part of the photois thickened due to theinflammatory responsecaused by an M.
paratuberculosis infection.Normally the intestine is thin
and pliable as seen in thelower half of the photo.Such intestinal thickening isless pronounced in speciesother than cattle
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In sheep and goats, the wool is oftendamaged and easily shed, anddiarrhea is less common than in cattle.
Clinical signs in other animals
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Post Mortem Lesions
In cattle
the carcass may be thin or emaciated
characteristic lesion is a thickened, often corrugated, wall in the distal
small intestine. more advanced cases, the lesions can extend from the duodenum to
the rectum.
mucosa is not ulcerated
mesenteric lymph nodes and other regional nodes are often enlargedand edematous.
Histologicaly , the lesions are characterized by diffuse granulomatousenteritis, with the accumulation of epithelioid macrophages and giantcells in the intestinal mucosa and submucosa
Acid-fast organisms may be found inside macrophages.
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Enlarged mesenteric
lymph nodes atnecropsy
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In other animals
Similar lesions occur in sheep and goats The mucosa is often only slightly thickened in
these species, but caseated or calcifiednodules are sometimes found in the
intestines and associated lymph nodes. In camelids--lymph node necrosis and
mineralization can also occur.
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Treatment
no satisfactory treatment
some combinations of antibiotics might besuccessful
long-term treatment would probably be
required and it is not likely to be
economically feasible
the chance of a complete cure is low
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Diagnosis
Labo ratory tests
variety of tests can be used . the choice of test varies with the stageof disease.
subclinical carriers can be identified with serology
delayedtype hypersensitivity (DTH) reactions,
polymerase chain reaction (PCR) assays or
fecal culture
Clinical cases can be diagnosed by culturing M. avium subsp.paratuberculosis from the feces or tissues
by demonstrating the organism with microscopy
DNA probes or PCR
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Microscopy
ZiehlNeelsen stains can be used to detect M. avium
subsp.paratuberculosis in the feces
clumps of small, strongly acid-fast bacilli are
diagnostic
Organisms may also be found in smears from the
intestinal mucosa or the cut surfaces of lymph nodes
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high power magnificationphotomicrograph of a Ziehl-
Neelsen acid-fast stained
histopathology section of
the bovine ileum
mycobacteria (red rod-
shaped bacteria) can be
seen
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Giant cells result fromfusion of several
macrophages. Suchcells are a hallmark ofgranulomatousinflammation and typicalof the host response toM. paratuberculosisinfection. The specifictype giant cells mostoften seen in Johne'sdisease are calledLanghans giant cells.
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The standard method fordiagnosis of Johne's disease is
isolation ofM. paratuberculosison standard bacteriologicalmedia. Shown here is one typeof such media, Herrold's eggyolk agar. Growth of slow-growing, small, white-yellow
colonies only on mediacontaining mycobactin (two lefttubes) is indicative ofM.
paratuberculosis. This test isusually done on fecal samplesand typically takes 12 to 16
weeks.
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Colonies ofM.paratuberculosis grown on
Middlebrook agar mediawithout Tween are rough inappearance. Tween 80 is asurfactant commonly used inculture media to accelerate thegrowth of mycobacteria. ForM.
paratuberculosis, Tween 80can alter the colonial andcellular morphology.
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Serology and tests
Humoral immu nity usu al ly develops 10 to 17 mo nths af ter infect ion
Serology can be used
1. for the presum pt ive ident i f icat ion of infected animals2. to est imate the prevalence of infect ion in a herd
3. conf irm p aratuberculosis in animals with cl in ic al signs
(Animals that have cleared the infect ion can be seropos it ive)
var iety of serologic al tests are
1. com plement f ixat ion
2. enzyme-l inked imm unos orbent assays (ELISAs)
3. agar gel immun odif fu-sion
4. Intradermal test in g
test ing with jo hnin or avian puri f ied prote in derivat ive tubercul in can detect delayed-typehypersensit iv- i ty (DTH) react ions to M. avium subs p. paratuberculosis ; how ever, th is testis insensit ive and nonspecif ic react ions are common DTH react ions m ay diminis h ordisappear as th e disease progresses.
Exposur e to other myc obacter ia, includin g environm ental saprophy tes, can result in fa lseposit ives
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A simple two-day test to confirm adiagnosis of Johne's disease incattle is the AGID serum from the
animal is place in one well, apositive control is place inanother, and soluble antigen isplace in the third (top well).Formation of a white line ofprecipitation between the sample
well and the antigen well (arrow)is considered a positive test.
This test is commercially knownas Rapid Johne's Test .
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The present ELISA uses PPA antigen from
the Map Bison type bacilli infecting domestic
livestock population of Northern India.
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Samples to col lect
Although the link is speculative, veterinarianscollecting samples should keep in mind that this
organism may be linked to Crohns disease(achronic enteritis of humans)
M. avium subsp.paratuberculosis can be isolatedfrom the feces, mesenteric, ileal and ileocecal lymphnodes, and thickened areas of the intestinal wall
Serum samples may be taken for serology.
Fresh, frozen or preserved milk samples can betested with the milk ELISA.
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The Iceberg Phenomenon infection in
the herd
In the typical herd, for every animal showing
clinical signs (Stage III), many other cattle
are present in the earlier stages of the
disease. For every obvious clinical case
(Stage III) of Johnes disease on the farm,
15-25 other animals are likely infected. Theclinical case represents only the tip of the
iceberg of the Johnes infection.
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For every stage III cow expect-
1-2 more cows in Stage III (clinicallydiseased)
6-8 cows in Stage II (unapparent carrier
adults)
10-15 cows in Stage I (infected calves &
young stock)
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Although test and removal procedures can reduce
the prevalence of infection, good management
practices are needed to reduce transmission withinthe herd
There is no satisfactory treatment for the disease
the trend toward intensive livestock production
practices has made control more difficult
Disease control is via implementing a variety of
production practices described below
Present scenario
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Management Recommendations for
Farm
A. Calving area-
Consider individual calving pens. Properly managed calving
pens are ideal. Keep clean and put one cow in at a time. Focus on keeping other adult manure away from the calves.
If individual calving pens are not available, be sure to keepthe calving area as clean and dry as possible.
Do not use calving pens for sick cows, Johnes diseasepositive cows or cows sick with Johnes disease.
Remove calves from cows and cow area as soon after birthas possible. The sooner the better.
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B. Pre-weaned heifer calves-
Do not feed pooled colostrum or milk.Consider pasteurization if you must feedwhole milk.
Limit or avoid any contact with adult cows orcow manure.
Wear clean overalls & boots and use cleanequipment when working with or feedingcalves.
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C. Post-weaned heifers-
Minimize any contact with adult cows or cowmanure (including any manure run off that
may go into heifer pens).
Avoid & minimize cow manure on buckets,
skid loaders, tractors, tires and otherequipment.
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Bred heifers-
Keep bred heifers separate from cows for aslong as possible.
Avoid feeding heifers refused (weigh back)
feed from cows.
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E. Cows & bulls-
Avoid spreading manure on hay ground orpastures, especially in the same season.
Identify and manage any test-positive cows
until they can be sold. Dont feed their
colostrum to heifer calves.
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F. Replacements & Additions-
Be sure to purchase replacements fromherds where the Johnes status is known.
Be aware of management practices and
manure exposure when using a heifer raiser.
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Hidden costs associated with Johnes
disease include...
Premature culling of clinical or infected animals.
Increased veterinary costs.
Increased replacement costs.
Increased susceptibility to other disease and possible breedingproblems.
Increase in overall cull rate.
Decreased milk production in infected but normal-looking animals.(Production effect depends on parity, stage of disease and stageof lactation.)
Decreased slaughter value of 20% to 30%. Decreased pool of available replacements, thereby limiting genetic
pool.
Decreased feed efficiency.
Loss of marketing animals for sale.
Loss of investment in young stock that have been infected or exposedsince birth.
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Job of a veterinarian
Because Johnes disease is a hidden disease, testing should be a partof a management plan. Testing for Johnes disease can help you:
1. Determine if an animal exhibiting defi nite clinical signs is Johnes
disease positive and should be culled.2. Identify infected animals with suspicious clinical signs early before
they further contaminate facilities and lose salvage value.
3. Evaluate the extent of infection in your herd.
4. Monitor progress of control efforts.
5. Know if you are marketing infected or low-risk cattle and, as a result,know if you are contributing to the spread of the disease to producersherds or helping producers prevent Johnes disease from entering theirherd.
6. Know if you are about to purchase a Johnes disease test-positive orlow-risk animal before its brought into the herd.
Following table contents can be
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Following table contents can befollowed by the veterinarian to controlJD in a herd
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