119. Paratuberculosis.

Question 1

Occurence of paratubeculosis?

Answer 1

Occurrence:

• worldwide;
• mainly Ru:
• cattle,
• sheep, goats,
• llamas, camels,
• farmed deer

Question 2

Aetiology of Paratubeculosis?

Answer 2

Aetiology

• M. avium susp. paratuberculosis (M. paratuberculosis)
• Fastidious (mycobactin – cell wall components of the bacterium),
• Long incubation
• Antigen relationship with other mycobacteria
• Ziehl-Neelsen positive, nests
• High resistance
• Obligate pathogen (can survive in the environment)

Question 3

Epidemiology of Paratuberculosis?

Answer 3

Epidemiology

• Shedding: faeces (3-5 months after infection), Milk; Lifelong shedding
• Infection: faeces, food, water, milk
• Long survival of the bacterium (6-9 months)
• Young animals are more susceptible to infection (no clinical signs in young)
• Clinical signs in adults (if infection happened at young age)
• Early infection (calf): long incubation, symptoms at 2-5 years of age
• Predisposing factors:
• pregnancy,
• deficiency,
• BVD,
• parasite infection

Question 4

Pathogenesis of Paratuberculosis?

Answer 4

• Pathogenesis

• 2 phases: 1st
• tuberculoid, 2nd
• lepromatous
• Infection: newborn (PO)
• Replication: intracellular; T-lymphocytes, macrophages engulf bacteria; replicate in small
• intestine & LNs
• Intra cellular bacterial replication (LST+, allergic tests+)
• Lysis of macrophages
• Released bacteria are phagocyted by macrophages
• Inflammation (histiocytes, Langhans giant cells, connective tissue) – thickening of the gut wall &
• nutrients cannot be absorbed
• Cytokin production of T-lymphocytes (TNF, gIF)
• Productive inflammation in the gut wall
• Atrophy of the intestinal follicles - Decreased absorption
• Protein-loss through the lumen of the microvilli
• Diarrhoea (no absorption – lots of watery faeces), Weight loss
• Humoral immune reaction (- LST, + AGP, CFT, ELISA)
• Shedding of the agent before the clinical signs
• NO tubercles & no necrosis!

Question 5

Clinical findings Paratubeculosis?

Answer 5

Clinical findings

• Long incubation, > 9 months
• Weight loss,
• decreased milk yield,
• severe diarrhoea: watery, smelly, squirt (jet-like),
• dark green/brown/black; oedema; arched back when defecating (pain)
• o Sheep, goat: milder

Question 6

PM lesions?

Answer 6

PM lesions

• Cattle
• Wall of the small intestine diffusely thickened, proximal large intestine
• Transverse folds, cannot be smoothed away (gyrus brain-like)
• Epitheloid cells, giant cells
• Enlargement of the LNs
• Sheep, goat: milder lesions

Question 7

Diagnosis?

Answer 7

Diagnosis

• differ to other mycobacteria – different tests in different phases
• Epidemiology – clinical findings – lesions
• Susceptibility of tests is changing
• Detection of the pathogen: early (asymptomatic): later: staining, IF, PCR
• Immunodiagnostics:
• Tuberculoid: LST, g-interferon test = cellular immune response
• Lepromatous: serology (CFT, AGD, iIF, ELISA) = humoral immune response (Abs)
• Allergic: johnin/paratuberculin PPD; avian tuberculin – susceptible at the beginning (cellular immune response)

Question 8

Treatment and control of paratubeculosis?

Answer 8

Treatment: none

Control

• In case of the disease: slaughter of infected animals, disinfection, not using infected pastures for a year
• Decreasing spread of the infection within the herd
• Prevention the infection of young calves
• Good hygiene (reducing faecal contamination)
• Clean water (no puddles, pools)
• Diseased animals should be culled
• Replacement animals from paratuberculosis-free herds
• Vaccination (1 month old 1x – prevent colonisation): attenuated and killed vaccines successful,
• problem = animals positive in tuberculin test so cannot use the tuberculin test

Question 9

Eradication of Paratubeculosis?

Answer 9

Eradication

• Test & slaughter (selection) – not feasible
• (difficult to recognise infected animals)
• Generation shift: separation of the calves after birth,
• after receiving the colostrum,
• milk replacers
• Herd replacement

Question 10

Public health aspects?

Answer 10

• Public health aspects:
• Crohn’s disease (?) – same CS in adults,
• PM lesions etc. as paratuberculosis (but not in all patients?)
• Can detect M. avium subsp paratuberculosis in the gut of some patients
• Appears to have some role in the disease