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This article was published in 1950
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Poultry Diseases

SOME IMPORTANT POINTS — WITH SPECIAL REFERENCE TO AVIAN TUBERCULOSIS AND ITS DIFFERENTIAL DIAGNOSIS

L. HART, B.V.Sc., "Cloudlands," Avoca, via Moss Vale

Avian Tuberculosis is an infectious disease of birds caused by the Avian strain of M. tuberculosis. It has a long incubation period and usually birds are several months old before they develop any lesions.

SYMPTOMS. The main symptom is emaciation, although some fowls remain in good condition even though severely affected. There is usually a steady drain in an infected adult flock, birds wasting and dying almost continually. Occasionally fowls become lame, usually in one leg, due to bone involvement; this lameness being intermittent in the early stages.

There rarely is any trouble in a flock until the fowl is at least a year old.

LESIONS. The main method of infection is by ingestion, and the primary lesion almost invariably is in the intestinal tract; often in the "caecal tonsils," patches of lymphoid tissue in the mucous membrane of the caeca and just inside the entrance. The lesion commences as an ulceration of the mucous membrane, a protuberance develops on the serous surface of the intestine and the ulcer perforates the bowel wall, into the centre of the protuberance. These nodules show considerable variation in size, ranging up to about 2 cm. diameter, and are yellowish-white and firm, but with a centre filled with caseous material. If these lesions are well developed, almost invariably other lesions of firm consistency, creamy white and of varying size, will be found in the liver and spleen. Lung lesions are uncommon, but lesions sometimes are seen in the bone-marrow of long bones, these latter manifestations being soft and caseous.

DIFFERENTIAL DIAGNOSIS.

Avian Tuberculosis may be confused with Leucosis, neoplasms, intestinal coccidiosis, Raillietina echinobothrida infestation, chronic peritonitis and heavy red mite and/or tick infestations.

1. LEUCOSIS. May be manifested in several different forms, viz.; neural, molar, visceral or leucaemic; the designations usually being Neural lymphomatosis, Ocular lymphomatosis, Visceral lymphomatosis (these three syndromes being caused by aggregations of lymphocytes in the appropriate tissues) and Leucaemia (large numbers of lymphoid cells—Lymphoid leucaemia —or immature erythrocytes—Erythroleucosis—in the circulation). a. Neural lymphomatosis. Paralysis of one or both legs and/or wings and marked loss of condition; particularly of the affected limb. When a leg is affected there is flaccid paralysis with loss of the "fanning" reflex (when the bird is dropped from a short height there is inability to "fan" or extend the digits and knuckling-over occurs); which differentiates this condition from tuberculosis of the bone.

b. Ocular lymphomatosis. Causes "grey eyes" (occlusion of the iris); practically never seen in tuberculosis.

c. Visceral lymphomatosis. Often manifested by wasting. The aggregations of lymphocytes occur in the viscera and may be diffuse, causing enlargement of the affected viscera—usually the liver and spleen, and often the ovary, is invaded, presenting a large fleshy mass; or discrete, appearing as creamy-white masses, readily confused with tuberculosis. However, if the lesions are those of tuberculosis typical nodules on the bowel wall, with ulceration of the adjacent mucous membrane, will be present almost invariably.

d. Leucaemia. Characterised by wasting and "watery" blood—but no lesions on post-mortem examination.

2. NEOPLASMS. These may occur in various viscera; simulating lesions of tuberculosis. It would be most unusual, however, for a neoplasm to produce such lesions in the solid viscera, and at the same time to produce nodules on the wall of the intestine. If the latter did occur they would not be associated with ulceration of the adjacent mucous membrane.

3. INTESTINAL COCCIDIOSIS. Causes diarrhoea and wasting, and there is oten a heavy death-roll. This disease attacks birds usually up to about six months of age; thus differentiating it from tuberculosis. Lesions are confined to the intestines. innumerable tiny whitish spots being visible through the serous surface, but there are no nodules.

4. RAILLIETINA ECHINOBOTHRIDA INFESTATION. Nodules occur on the walls of the intestines and caeca, due to the burrowing of the young tapeworms, the heads of which are provided with a large number of hooks. Such infestations rarely, if ever, cause death but the lesions may be found on examination of a bird dead from other causes. The nodules are rather small, even in size, filled with caseous exudate, often containing the tapeworm, and with an opening into the intestine. Affected birds are usually young. Microscopic differentiation from tuberculosis is uncertain.

5. CHRONIC PERITONITIS. This is a common condition in laying fowls over one year old. Affected birds often become emaciated and usually develop ascites. Lesions consist of thickening of the mesentery; whitish nodules often being present on it and also scattered throughout the parietal and visceral peritoneum, often being strung along the intestines. Close examination will reveal that the nodules are actually in the peritoneum. and section of the solid viscera will fail to reveal any lesions. Moreover, there will not be, of course, any ulceration of the mucous membrane of the intestine, corresponding to the nodules. 6. HEAVY RED MITE (Dermanyssus gallinae) AND TICK (Argas persicus) INFESTATION. These can cause profound anaemia and death, but post-mortem examination will fail to reveal any lesions.

COCCIDIOSIS. a. Caecal Coccidiosis. (E. tenella infection). Usually attacks chickens up to 10 weeks of age. The attack is usually peracute, and although blood may be seen in the droppings, chickens often merely appear listless for a few hours. and then are found dead. Post-mortem examination will reveal blood in the caeca (blind guts); and if the disease has progressed for a time the caeca may contain cheesy cores. Microscopic differentiation from Blackhead then is difficult.

Treatment with Sulphamezathine produces dramatic results; deaths ceasing within 24 hours. Give 2 fluid ounces of a 16% solution of the Sodium salt to each gallon of drinking water for 5 days—in earthernware vessels, or iron coated with vaseline. However, a second attack often occurs a week after treatment ceases; often a third outbreak.

b. Intestinal Coccidiosis. About seven or eight species of Eimeria have been described, but only two or three are severe pathogens. Fowls up to six months, and even older, often are attacked; diarrhoea and severe wasting, with heavy mortality, resulting. Post-mortem examination reveals catarrhal enteritis, with grey slimy intestinal contents and sometimes blood, with innumerable whitish spots visible beneath the serous surface. Treatment with Sulphamezathine usually gives disappointing results. Flowers of Sulphur, 5% in dry mash (all-mash ration) continued for 4-6 weeks, often arrests the disease.

HEXAMITIASIS IN TURKEYS. Caused by infection with Hexamita meleagridis, a flagellated protozoan parasite. Although unable to prepare material for a detailed study of the causal organism. it is practically certain that this parasite (recorded from the U.S.A.) was seen by the author in 1949, while employed at Glenfleld.

The disease attacks turkey poults when only a few weeks old and is most severe in those about six weeks of age. Birds are depressed, pass frothy faeces and quickly succumb. Mortality in the New South Wales outbreaks was high.

Treatment consists of giving as drinking water a 1 in 2,000 solution of Copper Sulphate for 3 days; alternating with plain water for 3 days (that is, 3 Copper Sulphate treatments).

SPIROCHAETOSIS. (Fowl Tick Fever). Caused by infection with Treponema anserinum. It should be borne in mind that the disease may be spread by the Red Mite as well as by the Fowl Tick.

The most notable advance in the control of this disease has been the elaboration (by the author) of an egg-grown vaccine; which now is being produced on a commercial scale at "Avoca" at a cost of 2d. or less per dose. The vaccine is given by intramuseular injection into the leg or breast; the dose being 1.0 ml. A very solid immunity is produced within three days, and birds vaccinated with one-quarter of the dose of the vaccine as produced commercially have failed to show any spirochaetes in their bloodstreams when injected with blood containing at least 1,000 infecting doses (maximum dilution tested).

Vaccinated fowls kept in a disease-free environment have shown a solid immunity after 12 months; so that in practice it is necessary to vaccinate a bird only once during its life. Birds of any age may be vaccinated but it is desirable, if possible, to wait until they are at least 12 weeks old; as the older they are when vaccinated the longer the immunity may be expected to last.

 


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