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This article was published in 1982
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Avian Tuberculosis

M.R. Barry, B.V.Sc., Veterinary Inspector, ALBURY

Avian tuberculosis has occurred in the Riverina district of New South Wales for at least 40 years. It has been found on farms where fowls are a sideline to other primary production. Its economic importance on these farms is not great but the disease must be controlled because it affects other more important animal enterprises on the farm.

CAUSE

The disease is caused by Mycobacterium avium. This strain of tubercule bacillus differs from those which normally affect cattle or humans.

SUSCEPTIBLE SPECIES

All species of birds are susceptible so all birds on the farm need to be taken into account. These include fowls, turkeys, ducks and geese, pheasants, pigeons, swans, guinea fowl, cage birds and wild birds which frequent the area where diseased fowls are kept.

It has been detected in pigs on farms where non-commercial farm poultry are allowed free range and where pigs and poultry run together or where fowls have access to pig pens and enter in search of feed.

Pigs are very susceptible to the disease and develop typical lesions.

Tattoo branding of pigs enables the farm of origin to be traced and control measures can then be adopted.

Cattle may be sensitised to tuberculosis following their exposure to the avian tuberculosis germs. Sensitised cattle may react to the intra-dermal test applied to them but show no visible lesions at slaughter. This may complicate testing for tuberculosis in cattle.

SOURCES OF INFECTION

An infected domestic bird brought on to the farm is a likely source of infection but infected wild birds may also introduce the disease from another farm where the disease is present.

Infected birds contaminate the ground with the tubercule bacilli which can live in the soil for up to 2 years in a protected position. Where the germs are exposed to sunlight they die more rapidly.

On a farm where the fowls have free range and the ground becomes infected then infection spreads gradually through the flock. Infected birds pass the bacilli with their droppings to further infect the soil and other fowls eating from the soil also become infected.

RECOGNITION

Some time after infection has gained entry to the farm an odd bird will be seen to become mopey and lose weight. Its comb shrivels and the bird may have white diarrhoea. There is progressive loss of weight even though it continues to eat. Some sick birds feel light if you pick them up.

Infected birds may be found sitting about the fowl shed, quite listless and languid. When disturbed they move off and some may show lameness. The affected fowls live for a week or more after becoming obviously sick.

Wasting and lameness gradually become more evident in the flock. Initially the owner sees only an occasional sick bird which later dies but after a year or so sick fowls are more common and at almost any time there will be unthrifty mopey birds sitting about the fowl shed.

POST-MORTEM FINDINGS

Infection appears to result from swallowing the bacilli while feeding and at autopsy it is common to find lesions in the intestine, liver and spleen. These lesions appear as small yellowish-white or greyish-white nodules from pin head to pea size but irregular in shape and located in the liver or spleen or along the intestine. The lesions consist of firm cheesy material. A nodule can be cut with scissors and slides prepared from the cheesy contents. Laboratory examination of the cheesy material can confirm a diagnosis of avian tuberculosis based on the history of progressive wasting and nodules seen at autopsy.

CONTROL

Once the disease has been confirmed all fowls and other domestic poultry should be slaughtered. The tuberculin test is not sufficiently reliable to eradicate the infection by testing and slaughtering reactors.

Quarantine is imposed until 2 years after the last of the infected flock is slaughtered to ensure that the disease is eradicated. It is necessary to spell the infected soil for 2 years from all fowls and domestic poultry. Cultivating the soil to expose the bacilli is an advantage.

HOUSEHOLD EGG SUPPLY

For owners who wish to have their own supply of farm eggs, some started pullets from a clean source can be installed in a cage clear of the ground after the infected flock is gone. The new birds must remain in their cage.

Alternately a shed can be constructed with a new concrete floor. Some started pullets can be installed in this shed and continuously confined for 2 years.

Either method ensures that the new flock has no contact with previously contaminated soil. Inspections are made to ensure that the fowls are not let out for 2 years.

The control method seems to be effective and several farmers have commented that they got more eggs with less trouble once the fowls are confined than they did when the flock was on free range.

Once the farm is rid of the infected fowls the disease has ceased to be a problem in pigs.

SUMMARY: Case History Cattle & Pigs (A.M.S., JINDERA)

23.7.61 1 barrow pig totally condemned at Albury abattoir - lesions in head mesenteric and mediastinal lymph nodes.

2.8.61 Owner traced by brand - pigs and cattle quarantined - practitioner to test cattle and pigs over 3 months of age.

7.8.61 Practitioner reported 8 cattle and 5 pigs positive TB.

14.8.61 All cattle NVL at slaughter, 2 pigs totally condemned - greyish calcified nodules in submandibular and mesenteric lymph nodes and free lesions in liver. The 5th pig, a sow, in isolation with 2 week old litter. Owner questioned about fowls - some killed for house had 'spotty' livers. Fowls were kept in a yard and shed adjoining the farrowing shed. Fowl manure was carted to paddocks - the only contact with cattle.

17.8.61 Property visited again to inspect fowls - no 'spotty' livers for past 2 years since old shed was pulled down, old flock disposed of and new shed erected for new flock.

24.8.61 Laboratory confirmation received - acid fast bacilli in pig tissue - typing was not successful.

9.10.61 5th sow sent to Albury abattoir - NVL at slaughter.

26.10.61 Comparative test cattle and pigs cattle all negative to bovine but 1 showed slight reaction to avian tuberculin a stud Landrace sow and boar reacted slightly to avian tuberculin - one barrow pig had a 6mm diameter swelling right ear (mammalian) but a 25 x 18 x 12mm oedematous left ear (avian).

30.10.61 Barrow pig reactor sent for slaughter.

31.10.61 4mm caseous yellow grey nodule in lower mesenteric lymph node.

7.11.61 Acid fast bacilli on smear of pig lymph node - culture unsuccessful.

19.2.62 Retest of sow and boar - sow negative - boar had a 4mm hardening at site of injection.

March 1982 No further problem with tuberculosis in cattle or pigs on this farm.

SUMMARY: Case History Fowls A.M.S. (JINDERA)

24.10.61 One sick fowl detected - destroyed - autopsy revealed yellow nodules up to 5mm diameter through liver and 1 nodule 1 cm diameter on intestinal wall - flock quarantined.

1.11.61 Laboratory examination of smears and tissue positive for Avian Tuberculosis.

19.12.61 Eighty two fowls post-mortemed at poultry abattoir - 46 showed nodules and those carcases were condemned. The few remaining fowls and ducks to be slaughtered for household use.

26.2.62 Last duck slaughtered - 2 year period of quarantine began - inspections at intervals.

11.2.64 Final inspection - no fowls present - fowlyard had been cleaned and cultivated during the 2 years and used as a vegetable garden.

Property released from quarantine on 26.2.64.

March 1982 No further problem with tuberculosis on this farm.

SUMMARY: Case History Fowls (E.R.. GEROGERY - Sister of above)

29.8.61 Property visited to inspect 2 cows which had reacted to TB test. Flock of 80 fowls on free range.

Autopsy of 1 fowl showing lameness and loss of condition - yellow nodules in liver, spleen and intestines - smears sent to laboratory.

7.9.61 Smears positive for avian tuberculosis. Property quarantined.

27.9.61 96 fowls sent to abattoir for slaughter - 22 infected at post-mortem examination. 4 ducks remained on farm - slaughtered that week.

24.9.62 Inspected started pullets placed in a cage the previous week. Inspections at intervals.

14.10.63 Caged birds appeared healthy - quarantine removed.

March 1982 No further problem with tuberculosis on this farm.

SUMMARY: Case History (A.B.S., GEROGERY)

18.8.61 2 reactors ex 14 cattle tested by private practitioner for tuberculosis (Lilly and Brindle) - placed in isolation.

29.8.61 Cattle inspected - tuberculosis found in a fowl of owners daughter (E.R.S.). Fowls run where the cattle grazed.

Discussed avian tuberculosis with owners - suggested comparative test of cattle after 60 days - both reactor cattle to be kept in isolation.

30.10.61 Comparative test - all cattle negative to mammalian tuberculin but Lilly, Nancy, Peggy, Darkie and Bessie had 6mm oedematous swellings at site of avian tuberculin injection

Conclusion - avian sensitivity - isolation discontinued.

23.2.62 Re test of 5 Cows with avian tuberculin each showed some swelling, 6mm - 12mm, (diffuse or firm) but in the case of Lilly 25mm x 12mm and diffuse.

5.6.62 Retest of 5 cows with avian tuberculin - each showed reaction but the largest was 7mm diameter.

28.9.62 Comparative retest of all 12 milkers showed 8 to have 6min swelling to avian but only Brindle to react to mammalian (3mm).

This cow Brindle had reacted on 18.8.61 became negative on 30.10.61.

2.1.63 Comparative test - Only Nancy and Brindle reacted both showing 3mm oedematous swelling on both caudal folds.

This sensitivity of cattle due to grazing on contaminated pasture appeared to have been lost.

March 1982 No further problem with TB on this farm.