115. Bovine tuberculosis (aetiology, epidemiology, clinical signs, pathology, zoon.).

Question 1

Occurrence of bovine tuberculosis?

Answer 1

OCCURRENCE

• Tuberculosis-free countries
• reservoirs:
• wild living ruminants,
• wild boars,
• badgers
• Infected countries

Question 2

Ethiology and epidemiology of M. Bovis?

Answer 2

ETIOLOGY AND EPIDEMIOLOGY

• Caused by M. bovis (mainly) and M. caprae
• Carrier animals shed via tracheal discharge, milk and other discharges.
• Asymptomatic carriers ʹ can shed the bacterium without showing symptoms! Disease can be introduced into disease free herd
• Other species can spread the infection ʹ wild living animals (feces, organs of hunted animals), badgers, human
• Cattle are very susceptible! ʹ aerosol infection with 10 bacteria enough to cause infection & k

Question 3

Pathogenesis(Remember Patho)?

Answer 3

PATHOGENESIS

• Infection via inhalation (droplet, dust),
• per os (milk - calves, contaminated feed)
• Intrauterine/coital/per cutaneous/ascending infection along the teats
• In cattle ʹ primary complex in the respiratory tract in 90-95% of cases
• Nature of the lesion ʹ Influenced by agent (species, amount and virulence) and host (resistance - immunity)
• In the beginning tubercles will be formed
• Mainly proliferative lesions when cellular immunity of the host is working highly
• Mainly exudative lesions when the host is weak and the immune system is not strong enough
• M. bovis are phagocytosed by macrophages and dendritic cells, where fusion of phagosome and lysosome is inhibited, and therefore M. bovis survives and replicate inside the macrophage
• Mycobacteria are released from dead macrophages Æ cellular immune reaction
• tubercle formation
• Mycobacteria, along with J-IFN and TNF, are released from dead macrophages
• will attract macrophages, histiocytes, lymphocytes and giant cells (form several layers around the bact.) (7 days)
• Plasma infiltrates in the center and coagulation necrosis will occur (14 days)
• Around this tubercle, granulation tissue will be produced and a fibrous capsule will be formed (3 w), and later calcification occurs (50 days)
• Poor cellular immunity
• mainly exudative lesions
• host will flood the area with plasma and lymphocytes, this will result in caseous necrosis
• Good cellular immunity
• mainly proliferative lesions
• granulation tissue and lympho-proliferation, no necrosis
• Pathogenesis is influenced by the immune system of the host, and if it is the first or repeated infection
• Phases of tuberculosis
• Primary focus ʹ lesions at the site of entry, if also lesions in regional lymph node
• primary complex
• Cattle ʹ lungs, Pigs ʹ alimentary tract
• Outcome ʹ healing, inactive state, early generalization ʹ lymphogenous, hematogenous spread
• Early generalization ʹ mainly tubercle formation, sometimes mainly exudative
• Depending on the level of specific immunity
• Acute ʹ military tuberculosis; protracted tuberculosis ʹ fewer, different size
• Lesions in lymph node
• Outcome ʹ death or inactive state
• Post-primary phase
• Pathogen ʹ endogenous reinfection (release from a focus), reinfection/superinfection
• Allergic host
• Isolated chronic organic tuberculosis (lungs, gut, udder)
• Intra canalicular spreading, caseous necrosis, caverns
• Exhaust phase, late generalization ʹ resistance is exhausted
• Exudative lesions, extended caseous necrosis, lesions in lymph nodes, death

Question 4

Clinical signs?

Answer 4

CLINICAL SIGNS

• Long incubation period ʹ months, 1-2 years, no typical signs
• Primary focus ʹ no clinical signs
• Early generalization ʹ mild fever, demeanor, anorexia, enlarged lymph nodes, drop in milk prod., body mass
• Organic tuberculosis ʹ enlarged lymph nodes, organic clinical signs (in progressed state)
• Pulmonary tuberculosis ʹ cough (dry, later wet), respiratory noise, rubbing noise (pleuritis), tympany
• Intestinal tuberculosis ʹ diarrhea, enlarged mesenterial lymph nodes
• Tuberculosis of the udder ʹ enlarged lymph nodes, changed consistency of the milk
• Renal tuberculosis ʹ turbid urine, protein in the urine
• Epididymitis, orchitis ʹ nodules
• Female genitals ʹ vaginal discharge, irregular cycle, infertility
• Central nervous system ʹ spasm, lameness unable to move
• Bones, joint ʹ movement disorders, deformation

Question 5

Pathology?

Answer 5

PATHOLOGY

• Primary complex is the place of entry
• • Lungs
• Tuberculosis nodosa ʹ small tubercles, isolation, calcification, lesions in the lymph nodes
• Chronic organic tuberculosis ʹ acinous, acino-nodosal pneum., caverns, no fresh lesions in lymph n.
• Late generalization ʹ fresh military tubercles, caverns, caseous lesions, fresh lesions in lymph nodes
• Intestine ʹ erosions, ulcers from lymphoid tissue
• Liver, spleen and kidney ʹ tubercles ʹ caseous necrosis, calcification
• Genitals ʹ tubercles, Udder ʹ military, nodosus, indurations