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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
SOME NOTES ON AN OUTBREAK OF AVIAN TUBERCULOSIS
K. V. Byrne, B.V.Sc. Inspector of Stock, Narrandera.
In November, 1944, whilst investigating a mortality in turkeys, which subsequently was found to be due to Botulism, it was discovered that fowls also were dying on the same property. The symptoms were entirely different from those shown by the turkeys, the main ones being a general listlessness, diarrhoea, lameness and loss of condition. About 30 deaths had taken place in a flock of approximately 200 birds during the preceding five months. A post-mortem examination was carried out on a recently dead bird and this disclosed in the liver, spleen and on the intestinal walls large and numerous tubercles which were considered to be typical of Tuberculosis. This diagnosis was confirmed by laboratory investigations; smears from the lesions revealing large numbers of acid fast organisms.
The first point of immediate interest was how the disease was introduced on to the property, as at the moment, it is understood, it is considered that Tuberculosis in poultry is a rarity in this State. As far as is known the position in New South Wales at present is that there have been three outbreaks (the first in 1940) of Avian Tuberculosis in properties close to the Victorian Border; whilst this one in the Narrandera District is the only other mortality on record, and is therefore the furthest north that the disease has made its appearance in non-introduced poultry in this State. However, no very likely explanation of how the infection reached this property was forthcoming; the only introduction in the year of the outbreak had been two bantam brought from Woodstock, New South Wales, and these were, and still are, apparently quite healthy. No importation of any sort had at any time taken place from any other State or from the southern portion of New South Wales. A few birds had been introduced from time to time from other properties in the immediate vicinity of the subject one, but none of these introductions had been less than 18 months prior to the appearance of the first loss which the owner suspected as having been due to Tuberculosis. The fowls were not within a mile of any neighbouring poultry, and prior to this mortality nothing had been observed which would have suggested that the disease was present elsewhere in the Narrendera P.P. District. It appeared unlikely, also, that the infection could have been introduced in eggs, as none had been bought for many years and those which had been obtained then were the produce of local hens.
Susceptibility; It is stated that all types of domestic birds are susceptible to infection, and it is of interest, therefore, to note that in this case ducks and turkeys gave evidence of apparently resistance. The feathered population on this farm at the commencement of the mortality was approximately 300 fowls, 150 turkeys and 20 ducks. During the course of the Tuberculosis losses the turkey population was reduced in a space of three weeks by Botulism to one half of the above figure, but the numbers increased again, and fluctuated between 100 and 150 subsequently. For the whole of the time losses from Tuberculosis were taking place in the fowls, these ducks and turkeys wandered indiscriminately among them and used the same receptacles for eating and drinking, yet no duck nor turkey showed any symptom; nor evidence of the disease when they were killed (a frequent occurrence) for consumption by the owner. In regard to age incidence, the disease is considered to be one of adult birds mainly, and this was borne out in this particular loss. The owner stated that it was not until the mortality had been in progress for 12 months that evidence of infection was noted in any bird before she commenced to lay. Allowing also for difference in numbers it appeared that a higher proportion of hens than roosters became affected.
Symptoms: Two separate types of manifestations of the disease were reported by the owner. One was seen in association with loss of condition and the other not. In the former, death did not take place for two to three weeks after the first appearance of symptoms: such being, apart from loss of condition, listlessness, diarrhoea and lameness. The last mentioned was not constant, being present in only approximately 10% of the birds, but the other two symptoms were manifested by all. In the hens which died without marked loss of condition, and usually without loss of condition at all, death took place very much sooner after the first appearance of ill health; sometimes, according to the owner, within a few hours. The first symptom noted in such birds was a gaping beak. It was observed also that they showed more respiratory distress than normal birds after being forced to make any unusual exertion. The owner stated that about half the birds died in fat condition and half after marked loss of condition. Apparently, also, there were no intermediate stages; the birds either dying with marked loss of condition or with very little loss at all. In some affected birds an increased prominence of the third eyelid was noted and the owner stated that he had come to regard this as a definite indication of the presence of the disease, the majority of fowls dying having shown this appearance. Neither loss of appetite nor anaemia as indicated by comb pallor, were noted in any bird.
Post-mortem Appearances:
The most obvious lesion was the presence of tubercles in the liver, and no fowl which had died from the disease was found to have a liver which did not contain numerous tubercles. The tubercles were white or faintly creamy and cheesy. No calcification was seen. It is noted that W. J. B. Murphy (1944) states in his article on this subject that in the liver miliary lesions were commonest, whereas in the spleen it is common to see lesions the size of a pea. However, in this particular mortality the lesions in all livers were of varying sizes with the pea-size predominating, and lesions of similar size were also very common in the spleen. In these organs the tubercles to be seen on the external surfaces were usually only slightly raised above the line of the normal surface, although in the spleen large tubercles sometimes caused considerable undulation of that organ's outline. Frequently, also, the presence of several large tubercles caused a considerable increase in the size of the spleen. From post-mortem examination of birds in the early stages of the disease it appeared that, the first lesions to develop were most likely to do so in the liver or the spleen. On one occasion 40 fowls were killed by the owner, under personal supervision, for disposal; all of these fowls, of course, having been selected because of their general healthy appearance and fat condition. However, five of these birds were affected with generalised Tuberculosis, and four were in the early stages of the disease. In most post-mortems, also, lesions were present in the form of tubercles on the external walls of the intestine and caeca, and nodules were quite common in the mesenteric lymph glands and breast-bone. Most of the intestinal lesions gave the appearance of being attached to the wall at their bases only; the greater part of the tubercle projecting prominently above the serous coat. No tubercles were seen in the kidneys, nor were macroscopic changes noted in the joints of birds which had shown the symptoms of lameness.
Mortality Rate: The first losses in this mortality took place in June, 1944, but the rate had not become very startling up to the time of the visit in November; during which time, as has been said, 30 fowls were lost. These losses had taken place in single birds at a slightly increasing rate, the final rate being two or three per week. The mortality continued at about this level for several months, and then lightened off considerably; falling almost to nothing for a number of weeks, when it accelerated again and became faster than ever. This is the end of the story as far as the original owner is concerned, as the fowls were purchased by the Department and conveyed to Glenfield for the purpose of examining the efficiency of the single intradermal tuberculin test. No tuberculin testing was carried out on the property.
Susceptibility of Man and Other Animals: In this connection (after a lengthy review of literature on European experiences) some notes of Klimmer (1930) might be of interest. The points made by him include the following:—Avian Tuberculosis is transmissible to other domesticated mammals. It has been found that 20% of cases of Tuberculosis in pigs in Germany were of Avian origin. Horses, cattle and sheep also were susceptible. Avian Tuberculosis can be transmitted to human beings and there are three authentic cases recorded in literature. According to German Investigators, from 3% to 7% of commercial eggs, and about 11% of eggs produced by tuberculosis hens, are infected with tubercle bacilli. If such eggs are places in an incubator the chicks hatched out from them may produce the infection in a hitherto tuberculosis-free flock.
References:—
Klimmer. M. (1930)—Vet. Rec. II: 562.
Murphy. W. J. B. (1944)—Aust. Vet. J. 20: 291.