116. Diagnosis of bovine tuberculosis, praeallergy, anergy, parallergy and their diagnosis in practice. Risk of reinfection (Zoon).

Question 1

Diagnosis of the disease?

Answer 1

DIAGNOSIS

Diagnosis of the disease

• Epidemiology, clinical findings and lesions, histology
• Detection of bacterium ʹ microscopy, isolation, (lab animal infection), PCR, IF, IP
• Irregular shedding, species identification by examination of the genome

Diagnosis of infection

• Allergic tests ʹ tuberculin tests
• Cellular immune response
• Gamma interferon test ʹ avian and bovine tuberculin results different production of J-interferon
• Need lymphocytes from animal
• Lymphocyte proliferation test ʹ not easy to carry out
• Humoral immune response ʹ ELISA: Antibodies against certain proteins are detected
• Examination of wild living animals (deer, badger), low susceptibility, complementary test

Question 2

Tuberculin tests?

Answer 2

Tuberculin tests

• Tuberculin
• Old tuberculin (Koch) ʹ extracted from broth culture of M. bovis
• Wanted to make vaccine, but found side effects.
• Those side effects appeared in those who had previously been infected with mycobacteria
• A mixture of different antigens
• PPD (purified protein derivate): tuberculoproteins ʹ dose 0.1 ml
• M. bovis ʹ 20.000 IU, M avium subsp. Avium ʹ 25.000 IU
• Thermal test ʹ elevation of temperature & general and organic reaction
• Injection of diluted PPD s.c. or i.v.,
• Before test ʹ measure basic temperature 3x Æ make an average
• Measure the temperature after 6h, then every 2nd hour (until 22h)
• Positive ʹ 1.5°C increase, general (fever, depression) and organic reaction
• (stronger where lesions are located pulmonary: coughing or dyspnea increased, enteral: diarrhea incr.)
• Skin intradermal test (SID) ʹ type IV hypersensitivity reaction, 90-95% sensitivity
• high specificity only on genus level
• 0.1 ml into clipped skin, on neck, shoulder or caudal fold
• Reading after 72h (older animals: 96h), repeating of test after 42 (60/90) days
• Positive reaction
• Increased thickness of skin fold
• Local reaction: edema, appearance of serum, scab, enlarged lymph vessels and lymph nodes, necrosis and pain
• Comparative tuberculin test ʹ mammal and avian tuberculin injected at the same time
• Transient desensibilization ʹ Important with precise test and measurement, and documentation
• Positive ʹ thickness of skin fold t 4 mm or local reactions
• Inconclusive ʹ 2- <4 mm and no local reactions
• Negative ʹ <2 mm
• False negative
• pre-allergy (1-3 weeks) ʹ fresh infection
• immune reaction need time to develop
• old, isolated infection ʹ no immune reaction any more!
• anergy, immunosuppression
• False positive ʹ M. bovis is not present, but reaction is positive
• Parallergy (other mycobacteria ʹ m. tuberc. Complex = same reaction, other = weaker react.)
• Heteroallergy ʹ Corynebacterium spp., Actinomyces spp.
• Antigen relationship

Question 3

Preallergy?

Answer 3

Question 4

Positive Bovine tuberculin reaction, tuberculosis free herd, treatment and prevention?

Answer 4

IN CASE OF POSITIVE BOVINE TUBERCULIN REACTIONS

• Close the herd,
• movement restrictions,
• isolation of reacting and inconclusive animals
• Diagnostics: comparative SIT,
• slaughterhouse control, J-interferon test
• Elimination of repeated reactors or stamping out the whole herd

TUBERCULOSIS FREE HERD

• Free state: all animals above 6 weeks of age,
• twice 4-12 months apart, SID negative
• Tuberculin test every year (every 3rd year),
• <1% positive, positive reactors are eliminated

TREATMENT

• Farm animals: antibiotics are not allowed (cannot prevent colonization) and long treatment with high dose
• would be necessary
• risk of antibiotic resistance, limited number of anti-mycobacterial drugs
• Eradication is the aim
• Zoo animals ʹ large doses, temporary improvement can be reached

PREVENTION

• General epidemiological rules
• Prevention of infection:
• quarantine, test with tuberculin test in introduced animals,
• isolation from wild anim.
• Vaccines ʹ M. tuberculosis, M. microti, BCG, Valle-P, atypical strains
• Short term protection, mycobacteria will colonize, generalization
• Farm animals are not vaccinated
• Per os vaccination with BCG (in some countries) ʹ wild living animals, reduction of infection

Question 5

Eradication and Control?

Answer 5

ERADICATION AND CONTROL

• Principles ʹ fetuses generally not infected, infected animals shed bacterium any time, tuberculin test is sensitive
• and specific, isolation of calves can prevent the infection
• Methods
• Selection ʹ test and slaughter ʹ tuberculin test ever 3-6 months, mainly small herds, older animals can
• give false negative reaction
• Generation shift ʹ isolated keeping of calves of asymptomatic cows, weaning at 3 days of age, tuberculin
• test at age of 6 months
• Herd replacement
• Maintaining tubercolisis free state
• Tuberculin test ʹ above 6w of age (12m in case of long free state), every year (every 2nd or 3rd in LFS)
• Slaughterhouse control lesions have to be sent to diagnostic laboratory
• Isolation of animals, reservoir animals have to be excluded
• Health control of staff, reinfection can happen sporadically
• Tuberculosis free country at least for 6 years maximum 0.1% infection, individual identification of all animals
• Regular and documented tuberculin tests, meat inspection of all slaughtered animals