Prevention is often better than cure when it comes to controlling duck diseases, as Dr Wiebke Oellrich, of Cherry Valley Farms, explains.
Ducks are a hardy species and most of the common diseases can usually be well dealt with through good management, biosecurity and vaccination.
But, while ducks are overall more disease-resistant than most other poultry, once there is a problem, treatment can be difficult as there are hardly any licensed veterinary products for ducks on the market.
Also, using products under the “cascade” system will lead to a withdrawal time of at least 28 days for meat, or seven days for eggs.
Duck producers, therefore, need to be even more aware of the common disease threats and take all reasonable precautions to keep them at bay.
Riemerella anatipestifer can cause serious problems in ducks between two and eight weeks of age and is often linked to poor hygiene and multi-age sites. Due to the bacteria being able to reach the brain, nervous symptoms like head shaking and mobility issues are common. Other symptoms are enlarged liver and spleen, pericarditis, perihepatitis, air sacculitis, arthritis and salpingitis.
Where R.a. is suspected, tests for the bacteria Coenonia anatine should also be performed.
Initial treatment with antibiotics can help, but on farms where the problem cannot be solved with good hygiene management, autogenous vaccines should be used.
Streptococci infections are also associated with poor hygiene, typically showing an increased mortality around 12-days of age. Enlarged, mottled spleens, enlarged livers, congested carcases, pericarditis, perihepatitis, airsacculitis and, in older animals, salpingitis and arthritis/tendovaginitis are some of the symptoms. Amoxicillin is often the first choice of treatment, but needs to be confirmed via an antibiogram.
Staphylococci infections are usually caused by Staphylococcus aureus, which are naturally occurring and can be found on clinically healthy birds. Some strains are highly virulent, particularly in young birds. After invasion of the body, the bacteria often cause secondary infections such as yolk sac or navel infection in ducklings, arthritis and/or skin lesions. Antibiotics are the choice for the immediate treatment, but in the long term, supporting factors such as poor management, intoxication or other infections need to be remedied, as resistance to antibiotics develops quickly.
E. coli infections are very common at all ages. Symptoms include navel infections, persistent yolk sacs, liver and spleen enlargement, congested lungs, pericarditis, perihepatitis, airsacculitis, salpingitis and peritonitis. Tendons and joints can be affected as well.
Antibiotic treatment should be done, based on a sensitivity test. If the problems persist despite good hygiene and management, the use of autogenous vaccines could be considered.
Pasteurellosis, or ‘fowl cholera’, is caused by the bacterium Pasteurella multocida. It can occur in several different forms and can cause, for example, septicaemia in a very short time, leading to sudden death with few symptoms, infections of the respiratory tract and eyes and chronic lesions include arthritis. Good sanitation practices, especially in and around standing water sources, go a long way toward preventing this disease and vermin control is very important. Medication can be difficult and autogenous vaccines are increasingly used.
Salmonellosis, the clinical form of a Salmonella infection, is quite rare in ducks. If it does occur, it usually affects very young birds, up to two weeks of age. Birds become depressed, dehydrated with acute enteritis and the caeca are often filled with a rather hard material instead of the usual fluid mass. Improved house hygiene with good rodent control and water sanitation are essential.
Duck viral hepatitis (DVH), affects young ducklings up to three weeks of age. Typically it leads to a very acute death, with the back arched and the head put far back. Very high mortality can occur, though surviving birds usually recover well, but carry the virus for up to eight weeks. An enlarged liver with haemorrhages is the typical post-mortem finding. Vaccines are available and various programmes possible.
Duck viral enteritis (DVE) is a herpes virus infection and affects birds above two weeks of age. It is often associated with access to swimming water and high morbidity and mortality can occur. Transmission is mainly by infected (wild) birds. Recovered birds may carry the virus for years. Sudden deaths, a drop in egg production, photophobia, thirst, severe diarrhoea, dehydration and ataxia are clinical symptoms. Post-mortem lesions include severe enteritis, crusty plaques from the oesophagus to the bursa, and haemorrhage in body cavities and various organs. No treatment is available, but preventative vaccines are used in various countries.
Avian influenza (AI) can be easily spread by ducks, as carriers are often symptomless. The route of infection is probably oral initially, but possibly by the conjunctival or respiratory route. The incubation period is three-to-five days and transmission is by direct contact with secretions from infected birds.
Newcastle Disease is very rarely diagnosed in ducks. It does not cause clinical signs in younger birds, but is a possible cause of production drops and fertility problems. Like AI, it is a notifiable disease
BYD virus is a new virus that has not been reported in Europe yet. Named after the area Bai Yang Dian where the virus was first isolated, it has been detected in China and South-east Asia. This virus causes severe egg drops and high mortality.
More so than chickens, ducks are particularly sensitive to fungi or the toxins they produce, and special care must be taken to source good-quality bedding material with a low mould count. Straw harvested under wet conditions is a particular risk. Otherwise ducks can easily develop aspergillosis, a condition which mainly affects the air sacs and lungs. The birds will gasp, lack performance and may even die when stressed. Good ventilation can help, otherwise there is no treatment.
Mycotoxins can be found in feed in temperate climates which can cause underlying disease problems, for example due to liver damage and a suppressed immune system. As there is no treatment available, prevention is the key element and good-quality raw ingredients and feed storage are essential.
The most common parasites are mites such as northern fowl mites, harvest mites and red mites. They can cause irritation of the birds, leading to reduced performance, and can carry over any existing disease problems into the next crop.
Affected sheds should be treated as soon as the last bird has left, and again when the shed is being warmed before the next arrivals.