Avian intestinal spirochaetosis (AIS) is a gut infection, mainly involving the hen’s caeca, which causes a chronic drop in egg production of usually 5-12%.
The disease is caused by a variety of spirochaete bacteria, now called Brachyspira(formerly known as Serpulina, Treponema and even Vibrio).
These organisms colonise the epithelial surface of the caeca and cause a variable
degree of damage that results in low grade diarrhoea, often reported as a higher incidence of brown, soft, caecal droppings. It has been found in replacement pullets, but this is relatively uncommon, and is more
often observed later as the birds are coming up to peak production and like a number of poultry infections causes them not to reach peak or have only a short peak production period and then a drop below standard production. This drop can last the whole laying period, if not diagnosed or treated.
A new review by David Burch of Octagon Services is now available online:
www.octagon-services.co.uk/articles/poultry/AIS.pdf

Had a chronic 15% drop in egg production @54 weeks last crop identified brachyspira pilosicoli as the probable cause have been advised to use Deniguard this crop but would like the opportunity to talk it through with as many people as possible. For some reason we had a big fly problem as well never had it before,  cured flys with neporex but I think damage was already done and didn't know about spirochaetes until joined this forum!!!!! unfortunatly by the time we had it confirmed birds to old to be economically viable to treat. So want to be ready for my next crop birds now 25weeks old .

I've sent copies of these two contributions to a friend of mine who has about twenty layers and advised him to look at the site.