Avian Intestinal Spirochaetosis in UK Layers

Originally from: Mike
                        
Brachyspira pilosicoli infection (a form of Avian Intestinal Spirochaetosis or AIS) of caged hens causes chronic soft to watery brown droppings, a 10% drop in egg production and 8% increase in mortality over the laying period. Newly published research by three UK vets records just how widespread spirochaetosis may be in the UK laying flock, both in caged and free-range birds.

In a small survey of six caged-hen flocks with depressed production, one flock had pale eggs, thought to be associated with high avian pneumovirus (ART/TRT) titres and only B. innocens was isolated. In the other 5 flocks, B. pilosicoli were cultured and only one of these flocks, with the most severe performance drop, showed rising IB titres as well. It is important to carry out a number of tests to obtain a correct diagnosis, as it may involve more than one causal agent.

Avian intestinal spirochaetosis may be more widespread than previously thought, especially in free-range flocks where B. intermedia appears to dominate. Caged flocks can be infected but B. pilosicoli appears to be more common. Calculations of the potential losses to the UK laying industry if 30% of laying flocks are affected could amount to over £4.1 million/year.

Treatment of laying hens is limited to two antibiotics in the UK, because of the necessity for a zero withdrawal period in eggs. Both tiamulin and chlortetracycline have been used separately and in combination to control these spirochaete infections and tiamulin has been shown to be effective where chlortetracycline resistance occurs. Both are antibiotics and must be used under veterinary supervision. It is important to treat early on in the infection to obtain the best results, before chronic caecal damage occurs and production is adversely affected.

The full report is online at: www.octagon-services.co.uk/articles/poultry/AIS.htm

it includes…

Photo: B. pilosicoli bacteria sticking to caecal cells.

Table: Comparison of Brachyspira infections in free-range and caged flocks with sub-optimal performance.

Graph: Treatment of a caged flock infected with B. pilosicoli with tiamulin and chlortetracycline.