1. Mycobacteriosis

What is Mycobacteriosis?

Mycobacteriosis is a contagious disease of domestic and wildlife animals and humans (zoonotic) with worldwide distribution, caused by some pathogenic strains of the genus Mycobacterium.

How are Mycobacteria classified based on their pathogenicity?

non-pathogenic or facultative pathogenic.

How long does it take for colonies of fast-growing bacteria to become visible under aerobic conditions?

In aerobic conditions, colonies of fast-growing bacteria can become visible in 2-7 days.

How long does it take for colonies of slow-growing bacteria to become visible under aerobic conditions?

In aerobic conditions, colonies of slow-growing bacteria can become visible in 7-60 days.

Why is the diagnosis of Mycobacteriosis complicated for certain species?

M. paratuberculosis is hard to cultivate, and M. leprae are uncultivable, making their diagnosis complicated.

What are the three complexes of Mycobacteria based on their characteristics?

1. M. bovis complex (M. bovis, BCG, M. africanum)
2. M. avium complex (M. avium, M. intracellulare)
3. M. terrae complex (M. terrae, M. nonchromogenicum, M. triviale)

How are Mycobacterium species divided based on changes post-infection?

1. tuberculous species (M. tuberculosis, M. bovis, M. microti),
2. lepromatous species (M. leprae, M. lepraemurium)
3. nontuberculous species (M. kansasii, M. avium intracellulare, paratuberculosis)

What is tuberculosis?

chronic contagious disease of domestic animals, wildlife, animals, and humans. During infection there is **inflammatory changes, granulating tissue and formation of nodules and granulomatous tubercules**. Zoonotic both ways.

What are some clinical signs of tuberculosis (tuberculous species) in different body systems?

1. In the CNS, signs include appetite loss and fatigue
2. In the lungs, signs include chest pain, coughing up blood, and a productive/prolonged cough
3. In the skin, signs include night sweats and pallor

What is the aetiology of tuberculosis?

***Mycobacterium tuberculosis****:* the most host specific. It causes respiratory tuberculosis of humans and non- human primates. Occasionally it also infects pigs, dogs, and birds.

***Mycobacterium bovis*****:** low host specificity. It causes chronic disease in most warm-blooded animals. Typical nodules and granulation tissue

What is the epizootiology of tuberculosis?

Bovine TB is OIE listed and is a problem in many countries (Germany, Czech and Slovakia are TB free), many of which have eradication programs. 

Source of bovine TBC generally is **infected cattle**. Source of M. tuberculosis – people suffering of TBC or animals infected by M. tuberculosis. 

Source of avian TBC – wildlife animals, poultry, swine. TBC in poultry mostly occur in older individuals.

What are the hosts of *M. tuberculosis*?

People, dogs, cats, pigs (mouse, guinea pig, hamster)

What are the hosts of *M. bovis*?

**people dogs, cats, pig, cow, buffalo, zoo species** (guinea pig, mouse, rabbit)

What are the hosts of *M. microti*?

people cat, mice, llama, ferret

Describe the transmission of tuberculosis

**aerogenic way by aerosol** (90% of cattle, humans), alimentary way (GIT, mostly calves, pigs, horses and birds), both (dogs and cats), in utero infection (mainly cattle). 

\
Tropism is based on the way of infection – lungs or liver. It is possible generalization of the infection. Could be in lungs, intestine, mammary gland, reproduction organs, CNS

Describe the pathogenesis of tuberculosis

Aerosol droplets inhaled to lung → phagocytosis of bacteria → Primary affection (granuloma) → primary complex forms in lungs or regional lymph nodes → necrotic centre → calcification of necrotic centre and surrounding by granulation tissue and fibrous capsule forming of tubercules → dissemination of through vascular and lymphatic systems (generalised & fatal - military TB; chronic & local)

What is the incubation period of tuberculosis?

weeks to months

What are the clinical signs of tuberculosis?

Chronic process with initially general CS, **weakness, anorexia**, fever, dyspnoea, cough, **enlarged lymph nodes.**  

\
Granulomatous/ caseous, tuberculous lesions in lungs

What are the pathologies caused by tuberculosis?

Lobular caseous **pneumonia**, pearl like nodules on serosa, miliary disseminated nodules, infiltrating caseous lymphadenitis. 

What are the diagnostic methods for tuberculosis?

Clinical examination in advanced stages (early is general), **PM at slaughterhouse** (granuloma), PA (all meat for human consumption)

Confirmation based on microbiological investigation – isolation and identification (**staining ZN**), cultivation, ELISA, PCR 

**Typical histology**: necrotic centre, epithelioid cells, langhans cells 

**Allergenodiagnostics = FIELD DIAGNOSTIC 🡪 skin tuberculin test**

* Hypersentitivity reaction using purified protein derivative applied intradermally (avian and bovine), measure skin fold oedema 72 hours apart for surveillance and control

OIE prescribed: **immunodiffusion, complement fixation, ELISA**

What are differential diagnoses for tuberculosis?

Actinomycosis, lung worm, traumatic reticuloperitonitis

What are the preventions for tuberculosis?

Protection of herd, vet control during animal transfer, quarantine (including zoo animals), aldergenodiagnostics supported by government, slaughter inspection, **pasteurisation of milk**. Disinfection, radical method of eliminated of infected animals. Zoonosis – protect the people, veterinary protective methods, regular medical examination = professional infection

What is the aetiology for non-tuberculous forms?

***Mycobacterium avium (different subspecies****):* generally, infect **birds**. Occasionally it also affects ruminants and **pigs**. Most common one in swine.

What is the epizootiology for non-tuberculous forms?

Source of avian TBC – wildlife animals, poultry, swine. TBC in poultry mostly occur in older individuals. Avian TBC usually occurs in older individuals

\
Swine: occurrence depends on TBC in cattle, birds and contact with sources of avian TB. Sporadic occurrence

What are the hosts of *M. kansai*?

 people, dog, hamster

What are the hosts of *M avium intracellulare*?

birds, people dog, cat, rabbit, mouse, swine wo CS

What are the clinical signs of non-tuberculous forms?

Poultry - Cachexia, diarrhoea, limping when bones are affected, decreased lay, bad nutritional status, 

* **Generalised nodules in liver, lungs, GIT, spleen, bone marrow**

Swine – **no clinical signs, slaughter inspection** – swollen LN (submandibular, retropharyngeal, bronchial, mediastinal

What is the aetiology of Johnes disease?

***Mycobacterium avium subsp paratuberculosis*****:** a global chronic disease causing significant economic losses (survive in environment in soil 11 months, faeces 240 days)

What is the epizootiology of Johnes disease?

Johnes: environment **(faeces**, less by genital excretion and milk), introduction through breeding, wildlife and generally **per os infection** but can be vertical. Predisposing factors = stress, poor nutrition, transport, parturition

What are the hosts of *Mycobacterium avium subsp paratuberculosis*?

cattle, other domestic and wild Ru, usually >30 months

What is the pathogenesis of Johnes disease?

In mucous of small intestine and associated lymph nodes 🡪 primary site of multiplication is final part of small intestine and top of colon 🡪 phagocytosis by macrophages in mucosa but not killed 🡪 chemotaxis bring new macrophages which phagocytose these in submucosa 🡪 decreased absorption 🡪 diarrhoea 🡪 **mucosa of small intestine thickens and wrinkles**

How long is the incubation period for Johnes disease?

2 or more years

What are the clinical signs of Johnes disease?

Preclinical stage: hypersensitivity to avian tuberculin

hypertrophic enteritis, profuse diarrhoea (**pea soup, smelly, blood and mucus**), afebrile, **weight loss**, decrease milk production, high mortality with CS; only 2-5% show CS

What is the pathology of Johnes disease?

Distal jejunum and ileum, ileocecal valve affected

Mucosa is 4x thicker = corrugation

Regional lymph nodes enlarged, oedematous, may be necrotic or calcified