Disease Alert in North Yorkshire: Swine Dysentery
As you may have heard there have been several cases of swine dysentery (SD) diagnosed in North Yorkshire in recent weeks. This serious disease appears to be spreading and is a major cause for concern. BPEX (through PHIP) are issuing updates with as much information as possible. Information-sharing and early diagnosis of new cases is needed to limit further spread.
Vigilance is needed to limit further spread and a
review of biosecurity for all units is important.
Swine dysentery can be a severe disease with a profound economic impact. Although mortality is generally not high, FCR and evenness of growth are severely affected. The cost of this together with medication to limit clinical signs can easily be in the range of £10 - £15 per pig produced.
The classic sign of SD is bloody, mucus-filled diarrhoea. However, signs can vary depending on unit, diet, other disease status etc. and the blood and mucus are not always present.
Even farms showing mild signs still pose a risk of spreading infection to other farms. The difference in virulence of strains is not yet well understood, and the difference in severity of SD between two farms may be due to differences in strain virulence or could relate to other farm factors, such as interaction with other infections. It is also unclear how much strains may adapt or become more virulent, so having a mild form of the disease on a unit does not necessarily make it a lower risk than a farm with more classical disease.
Some key features of SD:
· Caused by a spirochaete, Brachyspira hyodysenteriae
· Can cause bloody mucoid diarrhoea
· Varying signs depending on unit, diet etc.
· Usually in growing pigs
· Sows can become carriers
· Can survive 61 days in faeces or water
· Dies in 2-3 days in warm, dry conditions
· Infection is by ingestion of the organism
Consequences and control of disease
Generally it is uneconomic to farm with classical SD and an eradication programme should be undertaken after initial stabilisation. This involves an intense environmental clean-up and is usually best carried out in summer months when the organism will survive for a shorter period outside the pig. With a less severe or less persistent syndrome the economic decision may not be quite so clear-cut although an economic effect will be present. The farm is unlikely to ever be clear of the infection without undertaking an active and comprehensive eradication programme, so clinical disease may recur.
Although for the last 20 years or more there has been a very effective medication to aid in the treatment and eradication of SD, strains of B hyodysenteriae with multiple drug resistance have developed in the last few years making control increasingly difficult.
The good news is that this is an infection generally spread by pigs and pig muck, so entry of the organism onto farms can be prevented with good biosecurity. Over short distances between neighbouring units vermin and wildlife may act as mechanical vectors.
SD can be spread by:
Pig movement - carrier pigs can shed for up to 90 days with no clinical signs
Transport - especially pig wagons but also any other vehicles travelling between farms
Fomites - wellies, machinery, other animals/birds, tools, equipment (shovels, brushes etc)
A careful review of unit biosecurity is now critical
Abattoirs are a major crossover point and contamination of boots and vehicles can occur, even when taking other livestock to a mixed abattoir. Entry of vehicles into units should be prevented and a perimeter loading bay is required for good security. Purchase of your own bulk blower pipes is advised to avoid the need to use pipes that will have been used on other (often less clean) farms. Check that your visitor policy is enforced and only allow essential visitors onto the unit. Each site should have its own dedicated boots and overalls provided for staff and visitors alike. Restricted entry signs are helpful but a buzzer or contact phone number is needed to be effective in all cases.
As with an insurance premium the costs of maintaining good biosecurity may sometimes seem unnecessary, but the cost of prevention is a lot less than the cost of treatment and control.
If you wish to discuss your biosecurity further please do not hesitate to contact the practice, or visit our website www.garthvet.co.uk where there are published articles and standard advice sheets on biosecurity under the “downloads” heading.
If you see any looseness or diarrhoea in your stock that concerns you please ring the practice or your herd vet immediately. Early sampling of fresh faeces (before any treatment) is required for early identification of infection. This allows the most effective and immediate control, and helps to limit further spread.
CURRENTLY THIS DISEASE IS SPREADING!
INCREASE ALL BIOSECURITY SAFEGUARDS TO
PREVENT YOUR UNIT BECOMING INFECTED
Please see published articles in our download section for additional biosecurity information "Biosecurity: Keeping The Bugs Out".