Disease

 

Although mallard are easily reared they can be subject to many of the diseases of game birds, but it must be noted that the course of a disease may be different. Also, life in a watery habitat increases the importance of such diseases as those caused by the parasitic worms.

Healthy young ducklings grow rapidly on balanced poultry foods, but on poor diets deficiencies soon show themselves. It is surprising how often one meets the philosophy: 'Oh, ducks will eat anything.' Rations containing irritant materials can produce a form of enteritis whose symptoms may be similar to those of duck cholera and salmonellosis. Losses from this cause can be heavy. Poor diets are often deficient in vitamins, for example vitamin A. This lack results in a staggering gait, partial paralysis and whitish-yellow exudes in the eyes, and losses can be high. Too little vitamin A often predisposes birds to other diseases, including one known as 'white-eye' where the cornea of the eye becomes opaque simulating this condition.

Newcastle disease is not the killer that it is in game birds, but care should be taken if it is rife in an area, since mallard can act as carriers of the virus. Salmonellosis is not especially common but where it does occur mortality may be high and since transmission can be via the eggs, the danger of incubating mixed species or batches from different origins is emphasised. While treatment with furazolidone in the mash is suggested, survivors may remain carriers of the disease.

Given the correct conditions, such as high temperatures and dirty stagnant water, poisons are produced by the bacterium Clostridium botulinum which cause muscular weakness and ultimate death. Clean water will prevent this problem.

Cyathostoma, a worm similar to Syngamus, is found in the trachea of ducks and causes respiratory disease but without the 'gaping' associated with the latter. Mortality can be considerable in feathering birds and treatment with tetramisole is suggested. Another worm condition is acuariasis (due to Acuaria, a parasite which invades the wall of the proventriculus causing the formation of capsules and a partial breakdown of the digestion). It reaches another duck while living inside the water flea, Daphnia, which when eaten by a new host releases the larval stage to begin invasion of the gut. Treatment is not practical, but the cycle can be broken by increasing the flow of water through the rearing pens to 'wash' out the Daphnia.

A parasitic fungus, Aspergillus fumigatus, can attack the respiratory system of ducklings, but since there is no treatment, prevention is of primary importance. Mouldy straw, hay and grain are frequent sources of infection. Dampness and warmth are paramount in the development of this fungus.

Prevention is almost synonymous with 'cleanliness'. If good-quality food is provided, and overcrowding, chilling, bad ventilation and the generally dirty conditions so often seen with ducklings can be avoided, diseases should present few problems.

 

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