Young Birds—Rickets, nutritional paralysis (chickens turkeys), perosis, worm infest. N.L.G. crazy chickens, pullorum disease (may cause squatting).
Old Bird—N.L.G., spirochaetosis, febrile conditions (septic. pull. and cholera), worms, neoplasms, oviduct and water bag, head lice.
In the diagnosis of poultry diseases an approach may be made from any one of several standpoints. From the scientific approach the disease condition affecting any particular flock will be classified with regard to its cause and perhaps with further reference to the secondary causes and effects.
From the practical standpoint a veterinarian or stock inspector may be more inclined to approach the disease from a symptomatic classification. Thus the well-known poultry diseases most commonly met with can, with a few exceptions be divided into:-
(1) Catarrhal or roup diseases.
(2) Wasting diseases.
(3) Leg weakness diseases.
(4) Diarrhoea diseases.
It will readily be seen that there is nothing to recommend this classification except that when one encounters an epizootic the problem is actually presented to him in terms of the symptoms exhibited and a symptomatic classification may facilitate differential diagnosis for one who is not constantly working in the field of avian pathology.
Many diseases could fit into one or more of these groups, thus in laryngo-tracheitis in the sub-acute form diarrhoea may be a prominent symptom and in the chronic form the bird may waste away.
At the moment leg weakness diseases are under consideration. This group is of main importance in chickens and young growing stock, as in older stock casts seen are mainly the result of some isolated non-epizootic condition.
(a) Chickens and Young Stock.
The conditions of leg weakness inco-ordinntion of gait, staggering and deformity are very common under commercial poultry farming conditions, and unless the cause can be promptly and correctly diagnosed, very heavy financial loss may result. For example, where an owner had 3,000 day-old pullets which become affected at the third week with a staggering gait, if this disease happens to be rickets and the deficiency of mineral or vitamin is not supplied, it would be possible for owner to lose 80% of the birds in the next 10 days. Such mortality has been seen.
If the condition were faultily diagnosed as Avitaminosis A. when calcium deficiency was the cause, the error of diagnosis might occasion the loss of perhnps £50 per 1000 birds. This will Illustrate the urgency of correct information when making a differential diagnosis of the conditions.
(1) Rickets—This diaease is due to deficiency of Vitamin D. or deficiency of phosphorus or calcium. It may be caused by deficiency of one or more of these three materials. The supply of the three components is to some extent inter-related. Where ample Vitamin D. is supplied, faulty proportions or partial deficiency of phosphorus or calcium are not so likely to have a harmful effect. Conversely, when a correct amount and proportion of phosphorus and calcium is supplied, less Vitamin D. will be necessary. The amount of the components needed will vary with the growth rate and with the species of bird concerned. Thus, speaking in the same units, chickens require 18 units of Vitamin D. in every 100 grammes of foodstuff, pheasant chicks require 50 to 60 units, and turkey poults require 60 to 70 units. Vitamin D may be supplied by the chickens having access to direct sunlight. If they are housed out of the sun, the vitamin must be supplied by some substance such as cod liver oil, which must be freshly mixed in the ration.
Phosphorus and calcium is usually supplied in the form of sterilised bone meal or bone flour. For turkeys and rapidly growing chicks, 3% may be necessary; less will be required if milk is included in the ration.
Symptoms—Symptoms seldom appear before the fourth week, though they have been seen as early as the eleventh day.
The chickens are first noticed to become lazy, squatting down at frequent intervals. When attempts to walk are made, they wobble as though intoxicated. Unthriftiness and diarrhoea is in evidence. On close examination, bony enlargement of the ribs, the ends of the long bones and deformity of the chest are found to be present. If a chicken is killed it is found that the long bones in some cases can be bent in any direetion without snapping. The beaks of the affected birds are very soft and may become crossed and grossly deformed so that the birds that recover from the disease are unable to feed.
Differential diagnosis—The plastic condition of the bones right throughout the body, together with the joint enlargements and beak deformity, clearly separate this condition from any other disease. It may, of course, occur in conjunction with other disease conditions.
(2) Nutritional Paralysis—The most important type is Avitaminosis A. When Chickens are kept on a ration markedly deficient in Vitamin A., i.e. a ration without green feed, cod liver oil, yellow maize, or any other Vitamin A.-containing material, symptoms of the condition develop in intervals varying from 11 to 43 days, usually about 25 days
The onset of symptoms is very variable in view of the fact that different chickens have a varying store of Vitamin A. in their yolk. The Vitamin A. content of the yolk in turn varies with the amount of vitamin supplied to the hen which laid the egg. Symptoms. The chickens appear to be drowsy, they stagger as they walk (leg weakness), become emaciated and huddle together, many of them may develop symptoms of "eye roup." On close examination yellow pimples will be found in the mouth, throat and gullet, and there will be small glistening spots throughout the kidneys and at times covering the liver, heart or spleen. The bursa of Fabricius (a pouch on the dorsal wall of the cloaca) in many cases will be filled with either cheesy material or a flaky mucoid exudate. In some of the birds retention cysts will be present in the kidney, due to obstruction by uric acid salts. Differential diagnosis: Symptoms of leg weakness are quite constant in this condition, but it can be differentiated in view of the fact that symptoms of catarrhal disease are present in many birds and the yellow pimples are seen in the gullet and the cheesy material is present in the bursa of Fabricius. In turkey chicks and ducklings the catarrhal condition and pimples in the gullet may not be such a constant symptom as the bursal lesions.
Apart from leg weakness due to green feed deficiency disease (Avitaminosis A.), there is a condition in turkeys in which the toes become hardened, cornified and deformed, resulting in marked lameness. It would appear that this condition is a deficiency disease. It is very common in this country and has been reported in America. Little work has been done on the condition at present.
(3) Perosis. This condition occurs both on the coast and inland and is seen in both chickens and poults, though the latter (particularly in the case of quick growing poults) are the more commonly affected. The cause of this condition has been a matter for international scientific argument for some time. Many authorities have claimed that it is due to improper balance between calcium and phosphorus in the diet, or a relative excess or tendency of either one or both of these minerals. It has been shown that the feeding of rice bran 2O%, oat bran 20%, wheat embryo, whole oats or oat hulls and embryo or soya bean meal will prevent the disease.
Recently two groups of workers in America have shown that the condition is probably due to the deficiency of manganese in the diet. This latter explanation could adequately account for the fact why the above materials prevent the disease, as their ash is relatively rich in manganese.
Other minerals in small amounts are under suspicion as having some bearing upon the condition.
Symptoms. The Tendon Achilles slips laterally and the legs become bowed or twisted and the hock joint is enlarged or flattened, having quite a characteristic appearance.
The appearance of symptoms is usually in this order: Enlargement of the hock joint (tibia-metatarsal joint) first occurs, then a twisting of the distal end of the tibia and the proximal end of the metatarsus is noted. This leads to the lateral deviation of the gastrocnemious tendon. The shafts of the affected bones become shortened and thickened, and the chick becomes lame. The feet may be turned directly outwards and chickens affected in both legs may die within 12 days, due to inability to feed and move about. Faster growing birds of the heavier breeds, and particularly turkey chickens, seem to be most susceptible, and it usually occurs after the third or fourth week.
Differential diagnosis. In nearly all cases the bones are well calcified and will snap on bending, This clearly marks off the disease from rickets and there are no characteristic lesions in the throat and bursa of Fabricius as in Avitaminosis A.
Prevention is by supplying good balanced diet or, if the condition occurs, by the addition of oat or rice bran to the ration. Solutions of manganese sulphate are on trial at the present time, as to their efficacy in preventing the disease.
(4) Worm Infestation—Infestation by round worms may be severe when chickens are three weeks old. Tapeworm infestation may also occur at an early age and heavy infestation may lead to leg weakness. In the affected birds diagnosis is by post mortem examination. Heavy worm infestation may actually lead to symptoms of Avitaminosis A. or Rickets where these conditions would not occur if the worm infestation were not also present.
(5) Neuro lymponatosis gallinarium. This condition may occur in chickens as early as 5 weeks old. It may produce leg weakness, paralysis of the wings, twisting of head and neck, and quite a range of other symptoms.
Differential features are that there is no actual structural deformity in the leg nor any of the above lesions described in other conditions. (6) Crazy Chickens. This is a condition described in America by Bethke. The chickens may stagger about, lose control over their legs and may turn somersaults. It is not known whether this condition occurs here.
Miscellaneous. Most of the conditions affecting adult birds may at times affect the young birds. In particular, head lice infestation, heavy body lice infestation and extensive worry by red mites may lead to leg weakness.
(b) ADULT BIRDS.
In the case of adults, leg weakness is often referable to other well recognised disease groups, and economically serious outbreaks of leg weakness are not common in adults.
(1) Neuro lymphonatosis gallinarium. This disease is very common in New South Wales, occurring widespread in all country farming districts. Its symptoms are characteristic, both ante and post mortem. Separate Departmental pamphlet is available.
(2) Spirochaetosis. In fowl tick fever a true paralysis of the legs or wings may occur. This disease is spread by fowl tick and may actually be transmitted by red mites if the latter become affected by feeding on a diseased bird. Prevention by eradication of the fowl tick and red mite in the house or environs of the bird. Diagnosis of condition is well known. A separate Departmental pamphlet is available on this disease.
(3) Febrile conditions. In such diseases as septicaemic pullorum disease and cholera the bird may squat down on the ground and refuse to stand up or move unless vigorously disturbed. In such cases generally the symptom is referable to lethargy and weakness consequent upon the febrile state.
(4) Worm infestation. Heavy round worm and tape worm infestation will cause leg weakness and paralysis.
Diagnosis of these conditions is by post mortem and treatment is recommended in separate departmental pamphlet.
(5) Neoplasms. Cancerous conditions are extremely common in birds, and growths in the abdominal cavity may easily cause pressure upon the sciatic nerve or upon the blood vessels which supply the hind limbs and result in leg weakness or paralysis.
(5) Ruptured oviduct and abdominal cysts. When a rupture of the oviduct takes place, numerous yolks may be passed into the abdominal cavity and this may result in a large mass of inspissated material which results in pressure on the sciatic nerves followed by paralysis. Abdominal cysts (water bag) are very common and at times cause leg weakness. (7) Heavy infestation from head lice may cause symptoms of leg weakness.
Discussion. It will be seen from the above that when trouble is being experienced in a flock of young birds becoming weak in the legs or paralysed, diagnosis is a relatively simple matter and treatment in most cases quite effective.
It is pointed out that apart from the cases which develop so far as to produce definite disease, there are many more cases of partial deficiency which remain unrecognised. Such cases of partial deficiency cause lowering of the birds' resistance to other infectious diseases. e.g., it has been shown that a deficiency of Vitamin A. lowers the resistance of adult hens to colds, of ducklings to paratyphoid infection, and of all birds to various secondary bacterial invaders.