Bovis ISSN 2398-2993

Johne's disease

Synonym(s): Mycobacterium avium subspecies paratuberculosis (MAP).

Contributor(s): Dick Sibley , James Breen

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Introduction

  • Cause: infection with Mycobacterium avium subspecies paratuberculosis (MAP).
  • Signs: severe clinical cases show as weight loss and scour, but subclinical cases are more common.
  • Diagnosis: clinical signs, laboratory confirmation with serology, PCR and culture.
  • Treatment: there is no treatment available.
  • Prognosis: once clinical, prognosis is poor.
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Pathogenesis

Etiology

  • Mycobacterium avium subspecies paratuberculosis (MAP) Mycobacterium paratuberculosis is a resilient organism that infects the susceptible host either orally or nasally and invades the intestine wall and creates a latent infection.
  • The MAP organism lives in the macrophages and induces a poor, often negligible and undetectable immune response.
  • The latent phase of infection can be as short as 18 months, or can be for the lifetime of the cow - some infected cows never show clinical signs of any sort.
  • If the organism undergoes a reproductive phase, stimulated by some stress on the host, and possibly immuno-stimulation from another infection or similar, clinical signs may result.

Pathophysiology

  • Latent infection becomes clinical when the MAP reproduce and leave the macrophages and invade the wall of the small ingesting, causing an inflammation including edema of the gut wall.
  • The thickened intestinal wall loses function, and nutrients are not properly digested and pass through the gut.
  • The result is a protein losing enteropathy, with consequent weight loss and the effects of hypoproteinaemia such as ascites Ascites, submandibular edema and anemia.

Timecourse

  • Most infections are contracted at, or around, birth.
  • However, there is some evidence to suggest horizontal transmission may occur, with infected calves able to transmit infection to other calves. 
  • Many infections stay latent for the lifetime of the animal and never become clinical.
  • The incubation period from infection to clinical signs is generally 2-5 years, and is thought to be dependent upon the original infective dose and the stress on the immune system of the infected animal.

Epidemiology

  • Infected cattle become infectious towards the end of the incubation period and shed large amounts of MAP in their feces.
  • Some MAP is also shed in the milk and colostrum, but the density of the organism in milk may not be enough to be infectious for a suckling calf.
  • Most new infections are caused by the ingestion (or possibly inhalation) of the organism.
  • There is a natural resilience to infection once there is a functional rumen, and older animals require a much higher infective dose to become infected.
  • Young calves less than a month old are very susceptible to infection, and 80% of cases were probably infected in the first month of life.
  • Vertical transmission does occur, with heavily shedding cows being intermittently bacteremic and infection transferring across the placenta to the unborn calf. It is estimated that 10% of calves born to a heavily shedding cow will be infected at birth.
  • Most infections are environmental, with young calves ingesting the organism for feces that have contaminated the underbelly, teats and general environment of the calf.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMed Resource.
  • McNees et al (2015) Mycobacterium paratuberculosis as a cause of Crohn's disease. Expert review of gastroenterology & hepatology 9 (12) pp 1-12 PubMed.
  • Verdugo, Toft & Nielsen (2015) Within- and between-herd prevalence variation of Mycobacterium avium subsp. paratuberculosis infection among control programme herds in Denmark (2011-2013). Prev Vet Med 121 (3-4) pp 282-7 PubMed.
  • Nielsen S S & Toft N (2012) Effect of days in milk and milk yield on testing positive in milk antibody ELISA to Mycobacterium avium subsp. paratuberculosis in dairy cattle. Vet Immunol Immunopathol 149 (1-2) pp 6-10 PubMed.
  • Stevenson K (2010) Diagnosis of Johnes diseases; current limitations and prospects. Cattle Practice 18 pp 104.
  • Whittingdon & Windsor (2009) In utero infection of cattle with Mycobacterium avium subsp. paratuberculosis: a critical review and meta-analysis. Veterinary Journal 179 pp 60-69 PubMed.
  • Roermund et al (2007) Horizontal transmission of Mycobacterium avium subsp. paratuberculosis in cattle in an experimental setting: calves can transmit the infection to other calves. Vet Microbiol 122 (3-4) pp 270-9.
  • Groenendaal H, Nielen M, Jalvingh A W, Horst S H et al (2002) Johne's disease control: a simulation approach. Prev Vet Med 54 pp 225-245.

Other sources of information

  • Behr M A & Collins D M (2010) Paratuberculosi: Organism, Disease, Control. CABI. 
  • Smith R (2016) Tesco Sustainable Dairy Group Johne’s Disease Policy. [online] Available at: www.actionjohnesuk.org.
  • Farmers Weekly (2017) Milk buyers ditch farmers not tackling Johne’s disease. [online] Available at: www.fwi.co.uk.
  • Villarano M A & Jordan E R (2005) Production effects of MAP in dairy cows. Proceedings of International Johne's conference.

Organisation(s)


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