Mycoplasma synoviae...do we take it for granted?

Producers’ interest and concern about the current devastating disease outbreak of Avian Influenza in Holland is understandable when millions of birds have died or been destroyed. Closer to home, we also only really seem to worry about diseases in our own flocks that cause us to lose birds, have obvious clinical signs, cause distinct drops in production and/or increases in seconds and rejects.

But that may be just the tip of the iceberg. We never really know what effects subclinical ’hidden’ disease may be having on performance and on your bank balance. Mycoplasma synoviae (MS) infection is a good example.

As we have discussed previously in the Ranger, Mycoplasmas are infectious organisms, smaller than bacteria, larger than viruses. They can spread by aerosols or on equipment, clothes, people etc.

The two most important Mycoplasmas for chickens are Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS).

MG tends to be easier to diagnose because when introduced to a flock, birds usually show respiratory signs such as puffy faces, runny eyes and head shaking. Coughing and sneezing may also be seen. Death is usually related to secondary coli infection, air sac damage and peritonitis. Egg production can be affected in proportion to how sick the birds are. Diagnosis is usually based on this clinical picture together with specific blood test results and /or PCR testing.

MS infection, on the other hand, may only be detected on the basis of a blood test, because infection is frequently ’silent’. There may be no clinical signs or distinct effects on production or egg quality when infection is introduced onto a site. Again, movement of birds, equipment or people are the usual culprits for introducing infection but you may never know it. Infection can probably also spread on the wind for over a kilometre between houses or farms.

So should you worry?

The answer to this probably depends on a number of factors which, when working together, may make infection the significant problem in your flocks. The first is probably the strain involved. There is evidence that MS behaves differently in different flocks. Once suddenly introduced to a flock, some strains seem capable of causing acute lameness or respiratory signs and adverse effects on egg numbers and quality. On other occasions, a flock can be blood sample positive at point of lay having never shown any obvious previous problems.

The second aspect is when the flock is affected. New infection appearing in a flock just at it approaches the stress of peak production can result in a dented or stuttering peak.

Thirdly, and probably most significantly, is whether there are other infections or ’stresses’ already present in the flock. MS can ’tickle up’ other respiratory disorders such as ART or IB infection. Similarly, if flocks are weakened by significant red mite or roundworm burden, then the birds’ defences are likely to be less able to resist an MS challenge.

All in all, the take home message is that a flock free of MS infection is likely to perform much better than one that has met the infection. So it is clear that we do take this infection for granted. Unfortunately, it is difficult to turn back the clock. MS infection is widespread in many geographical areas and is present in many multi age flocks. Horizontal transmission (ie flock to flock on a site) is fairly easy and seems to be more rapid and significant than for MG. Infection is only likely to be removed from a site if it is totally depleted of birds as unlike some viruses, mycoplasmas do not survive for long periods in the environment.

So farms that operate a single age, all in all out strategy, with a period of rest between flocks are far less likely to suffer the effects of MS infection. This obviously depends on ensuring that your pullet rearer supplies you with MS negative birds in the first place. However, the downside of an all in all out strategy may be the interruption to your egg cheque.

Whatever strategy you use, ongoing biosecurity to reduce the likelihood of introduction of infection onto your farm, or moving it between houses on site, is a must. We have covered the details of a sensible biosecurity strategy in several recent articles in the Ranger. Although the bug is relatively fragile outside the bird, it can survive long enough to be spread by people and equipment.

Forewarned is forearmed

The key to coping with MS is to know what you are dealing with. So in addition to checking the blood monitoring of your rearer, you should have a regular blood sampling routine for your laying flocks. Forewarned is forearmed. Submitting bloods for testing at about point of lay will let you know the status of your birds as they come into production. Sampling again in mid lay and just before depletion lets you know what has gone on in these flocks and also the risk that these flocks pose to the next lot of birds in. Armed with this knowledge, you and your vet can plan a strategy that enables you to get the most out of your flocks by tipping the balance in favour of your birds and not the bugs.

So the answer to my question is that we probably do take MS for granted. We suspect infection is causing far more problems than perhaps we realise. Even if we can’t turn the clock back, it shouldn’t stop us planning for the future. In the US, at least, strains that are capable of causing significant egg production losses have been identified recently and it is unlikely we will have a blood test that can differentiate between ’hot’ and current UK mild strains. Producers should regularly question whether multi age is best for them, especially with many sites becoming ’fowl sick’. There are cashflow considerations that have to be taken seriously into account but never forget that while subclinical disease may never catch the headlines, it can hit your pocket.

In summary...take Mycoplasma infection seriously and don’t underestimate the potential problems it can cause. For the future we may have vaccines available—a new vaccination against MG is due to be launched in the UK shortly. But in the meantime biosecurity and disease prevention strategies are essential.