Paratuberculosis

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The paratuberculosis ( Johne's disease , according to Heinrich Albert Johne ) is a disease of ruminants caused by Mycobacterium avium ssp. paratuberculosis is triggered. The pathogen causes chronic inflammation of the small intestine with emaciation and diarrhea and is always fatal.

Due to the similarities in the clinical picture and supported by microbiological and molecular biological investigations, a possible involvement of this pathogen in the disease “ Crohn's disease ” in humans is being discussed. Raw milk , raw milk cheese and even pasteurized drinking milk are repeatedly cited as the vehicle for the transmission , as there are increasing references in the scientific literature to an occurrence in milk and a survival of M. avium ssp. paratuberculosis under the conditions of continuous and short-term heating there.

Paratuberculosis is a notifiable animal disease in Germany ; clinical cases of the disease are recorded via the animal disease message system (TSN) in the BFAV Wusterhausen (see also Friedrich-Loeffler-Institut , Federal Research Institute for Animal Health). In Austria it is notifiable , in Switzerland it is a Gr. 4 disease to be monitored (mandatory notification).

Cause and development of the disease

Mycobacterium avium ssp. paratuberculosis is an acid-fast short rod. It occurs worldwide. In addition to ruminants, camels, pigs, monkeys and rabbits are also susceptible. A pathogen can be detected in humans that cannot be infected by Mycobacterium avium ssp. paratuberculosis is to be distinguished. Also have individuals with handling cattle (veterinarians, farmers) significantly higher antibody - titers than the rest of the population.

In Austria the degree of contamination in cattle herds is estimated at 6 to 7%, in the Netherlands at 20%. In some US states, up to 70% of dairy cow herds are infested. Acid soils and high iron contents are said to increase the prevalence.

The incubation period is up to 10 years. Although the infection preferably occurs in the first 30 days of life, clinical diseases usually only become manifest in cattle over two years old (after the second to third calving). The calves usually become infected through feed and water contaminated with excrement from excretors. Infection through the milk is possible, but probably plays only a minor role. Although the pathogen does not multiply in contaminated soil, it remains infectious for up to a year.

After oral ingestion, the pathogen is absorbed by the M cells of the Peyer's plaques , released by them and distributed via macrophages . The pathogen can then be temporarily detected in the blood and other internal organs and antibodies are formed. As the disease progresses, granulomatous enteritis develops in the posterior section of the jejunum and in the ileum . If the body's immune system fails to control the infection, massive amounts of bacteria are released into the intestinal lumen and the bloodstream.

Clinical symptoms and course

Clinical outbreaks do not occur in every infected herd. Under certain circumstances, the disease only manifests itself in reduced performance in the three to six year old cows.

An outbreak in a single animal usually begins after birth and manifests itself in changing, sometimes watery diarrhea. The milk yield decreases sharply. The disease has no fever and leads to constant emaciation and even cachexia for weeks with an undiminished good appetite . The animals dry out and develop edema . The disease always leads to death after a few weeks or months.

The diagnosis is made by detecting pathogens in the faeces, by intracutaneous tests or by detecting antibodies in the blood. In the differential diagnosis, amyloid nephrosis , fasciolosis , copper deficiency, salmonellosis and idiopathic eosinophilic enteritis can be excluded.

therapy

Therapy does not lead to a cure. Antibiotics lead to a clinical improvement, but not to an elimination of the pathogen. In order to prevent further spread of the pathogen, the animal should be removed from the herd as soon as possible.

prophylaxis

Prevention primarily refers to removing cows with diagnosed and microbiologically proven paratuberculosis from the herd. Even with goat which is culling used to prevent further spread. It is also important to protect other animals from infections, especially calves. If possible, the calves should be separated from the suckler cows immediately after birth. The calves should then be given colostrum from unsuspecting cows. Calves from clinically ill cows should be housed separately. In some countries vaccines have been used for a long time. There is currently no vaccine available on the German market . Furthermore, after vaccination there is the possibility that vaccinated animals will react positively to the tuberculin test (bovine tuberculosis).

Mycobacterium avium ssp. paratuberculosis in milk and meat

In addition to vegetables, milk and dairy products are discussed as the most important sources of human exposure. In Great Britain, pathogens have been found in pasteurized milk samples from the trade using PCR . The pathogen can get into raw milk in two ways:

  • secretory: excretion directly via the mammary gland (only in clinically diseased animals, assumed germ count: 2–8 germs / 50 ml milk)
  • Faecal contamination: it is known that the pathogens in clinical paratuberculosis are excreted in extremely high numbers of germs with the faeces (107–109 CFU / g faeces) and can thus cause the milk to be contaminated in this way.

Compared to secretory contamination, the path of faecal contamination is definitely the more important one, as considerable amounts of germs are entered here and subclinically ill animals also excrete the pathogen with the faeces.

At the Federal Institute for Dairy Research Kiel an experimental plate heating system was set up to investigate the thermal resistance of M. avium ssp. paratuberculosis when heated, simulating the practical conditions as precisely as possible. Different heating processes are used in the dairy industry. The most important are the HTST process ( short-term heating , 72–75 ° C, 15–30 s) with a market share of approx. 40% and the UHT process ( ultra high temperature , 135 ° C, 1 s) with a market share of approx. 60%. Dairy products are mainly made from HTST milk; heating above 75 ° C is not carried out for technological reasons. With the HTST method, living mycobacteria could be detected in approx. 1/3 of the samples after heating in Kiel. There was always a significant reduction in the number of bacteria, but not a complete inactivation. This is explained with an asymptotic killing process. The phenomenon was observed that surviving pathogens could be found even at higher heating temperatures (up to 90 ° C). An explanation for the special heat resistance of M. paratuberculosis is possibly the slow metabolic processes of these organisms. When using what is known as vital staining, it can be observed that a maximum of 10% of a culture is only metabolically active. The rest seems to be in a dormant state, in which the germs are then possibly more resistant to the effects of heat. Dairy products and cheese are discussed as further vehicles for transmission of M. paratuberculosis. There is data that the pathogen can be detected in aged cheese.

A survey of Cypriot milk producers in 2009 found MAP at a concentration of several dozen cells per milliliter in 29 percent of the samples.

In a study in 2009, MAP was searched for in the diaphragm muscle in 47 cows and found in seven infected animals.

Mycobacterium avium ssp. paratuberculosis and Crohn's disease

A human disease similar to paratuberculosis in ruminants is Crohn's disease . Parallels can be seen in the clinical picture as well as pathological-anatomical. Crohn's disease differs from John's disease in animals, however, in that the disease is chronic, but practically never fatal, and that all sections of the gastrointestinal tract can be affected.

Crohn's disease is a chronic inflammatory bowel disease (IBD) with a multifactorial etiology and pathogenesis. Hereditary, dietary, immunological and psychological factors can be considered as triggers . It is currently assumed that the intestinal barrier will be damaged by a “first hit” and that inflammation will develop in which the damaged mucous layer of the intestine and individual cells of the intestinal mucosa are packed with germs, which, however, predominantly belong to the normal intestinal flora. The question of what this “first hit” could be has not yet been answered. The involvement of M. paratuberculosis in Crohn's disease is controversial. The experts estimate a causal relationship as rather unlikely, but consider it quite conceivable that pathogens worsen the clinical picture of Crohn's disease and could possibly have been a contributing factor in some of the patients. A possible involvement of M. paratuberculosis in the emergence or development of Crohn's disease is indicated by the fact that the pathogen has been detected in some of the patients (but in some cases also in healthy people) and that successful treatments with antimycobacterial drugs have been described. Overall, however, the research results to date are contradictory. Due to a lack of data, based on current knowledge, a comprehensive risk assessment with regard to a connection between M. paratuberculosis and Crohn's disease cannot be carried out.

literature

  • Minutes of the expert discussion on the microbiological risk assessment of a connection between Mycobacterium paratuberculosis and Crohn's disease on September 19, 2001 in the BgVV, Berlin
  • The significance of the heat resistance of Mycobacterium paratuberculosis for pasteurized milk by Philipp Hammer, Christian Kiesner and Paul Teufel (Kiel)
  • Textbook of veterinary bacteriology by Hans-Joachim Selbitz
  • Wells JE, Bosilevac JM, Kalchayanand N, et al. : Prevalence of Mycobacterium avium subsp. paratuberculosis in ileocecal lymph nodes and on hides and carcasses from cull cows and fed cattle at commercial beef processing plants in the United States . In: J. Food Prot. . 72, No. 7, July 2009, pp. 1457-62. PMID 19681269 .

Individual evidence

  1. ↑ a b c Gerrit Dirksen: Internal medicine and surgery of the cattle . Georg Thieme, 2006, ISBN 9783830441694 , p. 586.
  2. ↑ Annex to Section 1 of the Ordinance on Notifiable Animal Diseases (TKrMeldpflV) in the version published on February 11, 2011 ( Federal Law Gazette I p. 252 ), last amended by Article 381 of the Ordinance of August 31, 2015 ( Federal Law Gazette I p. 1474 )
  3. ↑ a b c d e Gerrit Dirksen: Internal medicine and surgery of the cattle . Georg Thieme, 2006, ISBN 9783830441694 , p. 587.
  4. ↑ a b Gerrit Dirksen: Internal medicine and surgery of the cattle . Georg Thieme, 2006, ISBN 9783830441694 , p. 588.
  5. ↑ a b Gerrit Dirksen: Internal medicine and surgery of the cattle . Georg Thieme, 2006, ISBN 9783830441694 , p. 589.
  6. ↑ Illness in the goat farm - 145 goats killed. In: srf.ch . November 6, 2019, accessed November 10, 2019 .
  7. ↑ Slana I, Liapi M, Moravkova M, Kralova A, Pavlik I: Mycobacterium avium subsp. paratuberculosis in cow bulk tank milk in Cyprus detected by culture and quantitative IS900 and F57 real-time PCR . In: Prev. Vet. Med. . 89, No. 3-4, June 2009, pp. 223-6. doi : 10.1016 / j.prevetmed.2009.02.020 . PMID 19349086 .
  8. ↑ Alonso-Hearn M, Molina E, Geijo M, et al. : Isolation of Mycobacterium avium subsp. paratuberculosis from muscle tissue of naturally infected cattle . In: Foodborne Pathog. Dis. . 6, No. 4, May 2009, pp. 513-8. doi : 10.1089 / fpd.2008.0226 . PMID 19415976 .