Q Dear Practical Poultry, I'm a newcomer to poultry keeping and find your new magazine very helpful. I was particularly interested in the mycoplasma article published in the July 2004 issue. It's something that is sometimes mentioned but which, unfortunately, appears to be endemic in poultry flocks in this country.
Lindsay's article was very good. However, a number of things were implied, but not spelled out.
Experienced poultry keepers probably know the answers to these points but, for someone like myself and no doubt many other novices, it would be really useful if these things were clearly stated.
The points that I picked up from Lindsay's article were as follows:

1. M. gallisepticum can be spread by 'egg transmission.' Does this mean on the shell or inside the egg, or that the chick is infected?
2. Dipping or injecting the eggs...can reduce the number of positive chicks hatched. And later ifs advised that we 'buy in negative chicks, poults or hatching eggs.' Does this mean that eggs and chicks can be tested as carriers? I have seen stock advertised as vaccinated, salmonella-tested etc, but never as mycoplasma-tested. Surely dipping eggs can only destroy pathogens on the shell.
3. 'Treating will decrease the signs of infection but not eradicate it.' Then a reference is made to 'passing mycoplasma down through the generations.' Does this mean that if you have, or have had, one infected bird in the flock, even if it's treated or culled, the infection will be in the flock forever and cannot be eradicated (short of replacing the whole flock and disinfecting houses etc.)? If this is so, are you saying that only good management and stress-free conditions can prevent outbreaks of symptoms. Does this also mean that even if there are no clinical signs, most of the birds will be carriers?
4. In the same vein, 'measures for long term management.' were mentioned in the final paragraph. What sort of measures are these?
5. 'Quarantine new birds away from the rest of the flock', and, 'disinfectants can be used.' For how long should birds be quarantined and what should we use the disinfectant for?

I'd really appreciate it if you could answer these questions and tie up these few loose ends.

A Egg transmission: I left this vague as I could not find any description of how this works in the case of mycoplasma: some studies show that dipping the eggs reduces the infected chicks hatched - this would imply, as you say, that the mycoplasma is carried on the surface of the egg. But other studies show that dipping doesn't work - implying that the infection is within the egg. I could find nothing definitive. To buy in negative hatching eggs, chicks or poults, you would need to find a supplier (commercial breeders of commercial hybrids, you won't get pure breeds from small-scale breeders that are certified negative) of blood-tested negative breeding stock. If the flock is negative, then the hatching eggs, chicks and poults will also be negative. Treatment will not eradicate infection and, if you have a flock of breeding birds of several generations, the infection will be passed from generation to generation. The aim is to have birds that are healthy enough not to succumb to the infection, so weaker birds that do show signs should be culled - they increase the infective risk for the rest of the flock. The only way to eradicate mycoplasma is to depopulate (cull every bird), pressure-wash, disinfect thoroughly, fumigate if you can, and then re-populate with stock from blood-tested negative flocks. This is not usually an option for pure breed or pet keepers, so good management is the only tool we have.
Healthy birds will carry several different mycoplasmas without showing any clinical signs. Disease and clinical signs would result when a bird's resistance is lowered by stress (environmental - lack of water, high air ammonia due to lack of ventilation, mixing birds or adding a bird to an established group, coming into heavy moult, point-of-lay etc).

Quarantine: I would normally suggest a period of one month spent in a different air space to the other birds. This allows plenty of time for the stress caused by travelling, the whole sole/auction process, the shock of new surroundings and routine, different food etc., to take full effect and trigger anything that is lurking in the new bird. I would then suggest taking some litter or bedding from your own birds and introducing that to the pen of the new one (still in quarantine), so that it can get used to the infections in your own birds while it remains in the surroundings it has now got used to. I think ifs important to do this before subjecting it to the stresses of mixing with other birds, combined with yet more new surroundings etc.
The new bird's immunity will be high and hopefully (it can never be guaranteed), it will fight off and develop an immunity to whatever new bugs it has not met before. So, effectively, two months in quarantine is needed - the first month to get over its own infections, and the second to get used to yours.

Disinfectants: The dilution I quoted is actually 10 times stronger than would normally be used (the normal dilution is 1:1000), so this mixture should only be used on houses, boots etc. Remove the birds from the pen, clean it out thoroughly - including feed bowls and water containers -disinfect and allow time for everything to dry before putting new bedding back in. Rinse feed and water bowls thoroughly before re-using.
For us small-scale poultry keepers, long-term management is not an option - pure breeds are not available mycoplasma-free and there is no point being mycoplasma free if you are involved with showing or spend time with other poultry keepers. Long-term management essentially means eradication to produce a mycoplasma-negative flock. The big commercial boys are able to do this; they have the resources available to blood-test flocks, cull all positives and then guarantee a closed system to ensure that no mycoplasma can be carried in. The birds would be kept in a controlled environment with strict biosecurity methods in place. For those of us with birds in the back garden, running around the lawn, such measures just aren't feasible.