Avian Intestinal Spirochaetosis - Clearing the Confusion

David G S Burch BVetMed MRCVS
Veterinarian, Octagon Services Ltd
(Article published in "Poultry World" April 2005)

There has been much confusion over the significance of this condition, particularly in commercial layers. It has been recognised in the United Kingdom since the early eighties, as a cause of poor egg production, but many authorities were not convinced that it did cause a problem because they could find spirochaetes (spiral-shaped bacteria) in the caeca of clinically affected birds and in normal birds.

Additionally, the names kept on changing from Vibrio, to Treponema, to Serpulina and now, finally we hope, Brachyspira. It was not until the late nineties that matters became clearer as they classified the bacteria into different species or sub-groups, and not all will cause disease in chickens, although they may in other avian species (See Table 1).

Table 1. Main species of Brachyspira and their significance in chickens


Bird / Animal


Significance in chickens
(drop in egg production)

B. hyodysenteriae

Rhea / Pig



B. pilosicoli

Chicken / Duck / Man / Pig / Mouse


Mild-moderate (5-10%)

B. intermedia

Chicken / Pig


Mild-moderate (5-10%)

B. alvinipulli


N. America

Mild (5%)

B. innocens

Chicken / Pig



B. murdochii

Chicken / Pig



To a greater extent, this explains why you find some spirochaetes in normal birds, as they have no clinical effect and why some definitely do have an impact, and can reduce overall egg production by up to 10%.

Brachyspira are difficult and slow to grow and require specialised media and culturing over 3-5 days. Most laboratories do not routinely grow them, although the Veterinary Laboratory Agency (VLA) can, from very fresh pooled faecal samples, as they are looking for them routinely in pigs. They then have to be differentiated into the particular species, usually by cultural and biochemical means. Recently, with the development of DNA analysis (PCR technique) they can differentiate the major brachyspira just from a simple faeces sample. This work is done especially at Scottish Agricultural Colleges (SAC) Veterinary Services, Penicuik, near Edinburgh.

The brachyspira colonise the caeca of the birds and ones like B. pilosicoli, cause a mild to moderate diarrhoea, which is classically a soft to watery brown dropping in upto 25% of hens (See Photos 1 & 2). This causes pasty vents and dirty eggs and a drop in egg production of between 5-10%, depending on the pathogenicity of the strain and the severity of the challenge. Faecal contact is important, so may be more easily transmitted in free-range and barn kept hens but can be found in caged birds, possibly associated with poor fly control and hence, feed contamination.

Photo 1. Typical brown/fawn, soft to watery droppings

Avian Intestinal Spirochaetosis - Typical brown/fawn, soft to watery droppings


Photo 2. Typical brown, soft to watery dropping

Avian Intestinal Spirochaetosis - Typical brown, soft to watery dropping


In a recent field case, in a multi-aged caged-bird site, hens had been showing poor production over an 18month period without finding the cause, in spite of extensive serological diagnostic work and routine use of chlortetracycline in the feed. Finally, the condition was diagnosed after culturing B. pilosicoli from the caeca of some sacrificed hens.

The birds were treated with Tiamutin (tiamulin - Novartis), a new antibiotic approved for mycoplasmosis in chickens in the UK, but used extensively in pig medicine for spirochaete control. The birds were treated for 3 days in the drinking water and a steady improvement in production was observed. This was repeated 20 weeks later and a suitable fly control programme was introduced. A comparison of production performance between a flock, which was infected but untreated and a flock, which was treated with tiamulin at 25 and 45 weeks of age are shown (See Table 2 and Figure 1).

Table 2. Comparative production data for an infected untreated flock and tiamulin-treated flock
at 25 and 45 weeks of age


Infected flock

Tiamulin-treated flock

Improvement (%)

No of hens housed








Eggs/HH week 72




Total egg weight/HH (kg)




Ave egg weight (g)




Feed consumption/day (g)




Ave bodyweight (kg)




Mortality (%)




Extra eggs/HH





Figure 1. Comparative laying curves of an infected untreated and tiamulin treated flock

Comparative laying curves of an infected untreated and tiamulin treated flock

When extra egg production and reduced mortality are taken into account, there was a 28.58 extra eggs/hen housed production improvement, which could be valued at 0.56/hen housed after taking into account extra feed and treatment costs.

Brachyspiras are potentially a significant infection in laying hens and have been reported in broiler breeders as well. They should become part of the differential diagnosis, when flocks are not achieving expected performance and wet droppings are reported. Improved diagnostic techniques are now becoming more readily available to clarify any confusion.


Copyright © Octagon Services Ltd   2005

*More on Poultry Diseases & Medication:  Octagon Poultry Technical Papers

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