Avian intestinal spirochaetosis (AIS) is an enteric disease caused by the Gram-negative spiral-shaped bacteria of the genus Brachyspira. In chicken, B. intermedia, B. pilosicoli and B. alvinipulli are considered the pathogenic species that cause AIS in adult breeders and laying hens.

The present study investigated the prevalence of Brachyspira spp., in the leading Italian regions for egg production, in relation to disease association, production problems and housing system.

Material and Methods

Sampling

Pooled faecal samples (50g) were collected in 74 sheds on 32 laying hen farms in the north of Italy. Brachyspira spp. presence was investigated by PCR and bacteriological isolation procedures.

Information on the age of the chickens, housing, problems with egg production and wet faeces were collected at the time of sampling.

Brachyspira spp. isolation and identification

Samples were plated onto selective medium BAM-and cultured as previously described (1). Spirochaetal cultures and faeces were subjected to genus and species-specific PCR and/or to 16S rDNA sequencing (2,3,4,5).

Statistical analysis

The Fisher's exact test was used to evaluate the correlation between Brachyspira infection and number of birds per shed or housing system. The χ2 test was applied to study possible relatedness between spirochaetal infection and age, enteric disorders, and production problems.

Results

Intestinal spirochaetes were isolated from 22 of the 32 layer farms (68.7 per cent) and in 31 of the 74 sheds (41.9 per cent). Twenty flocks (27 per cent) on 15 farms (48.3 per cent) were colonised with the known chicken pathogenic spirochaetes. Seventy-five per cent and 58 per cent of tested farms and sheds, respectively, tested positive for Brachyspira spp. with at least one of the two tests.

Among the 47 isolates from the 31 positive samples, 17 were identified (36.3 per cent) as B. innocens, 1 (2.1 per cent) as B. murdochii, 11 (23.4 per cent) as B. intermedia, 14 (29.8 per cent) as B. pilosicoli, 2 (4.2 per cent) as B. alvinipulli and 2 (4.2 per cent) were not unidentifiable. The prevalence of spirochaetes was higher in sheds of chickens > 40 weeks of age than in those ≤ 40 weeks of age (p= 0.042). A significant association has been observed also between colonization with spirochaetes and freerange flock and flocks hosted on slatted floors (p=0.006) and between colonization with intestinal spirochaetes and the presence of enteric disorders consistent with AIS (p=0.022). Moreover, there was a significant association between the presence of spirochaetes and reduced egg production (p=0.014) quantified as a percentage of between 3 per cent and 9 per cent. On the contrary no statistical significance between the flock size and infection was observed (P=0.057).

Discussion

Colonisation of laying hen flocks with intestinal spirochaetes is common in Italy. The results concerning egg production and spirochaetal infection help confirm the potential economic importance of AIS.

Enteric disorders were significantly more frequent in flocks colonised by intestinal spirochaetes but no significant association was found with these conditions and pathogenic spirochaetes. This could be explained by a lack of knowledge concerning the pathogenic potential of the so-called ‘‘commensal’’ Brachyspira spp.

The size of the flock had no statistically significant influence on colonisation, even if small flocks showed to be more frequently infected than large ones. This result could be explained by the fact that small flocks are usually kept in potential risky farming conditions such as free-range or “on litter”. This observation indicates that the longer lifespan and, therefore, the longer productive career of laying hens increase their risk of exposure to infection.

References

1. Bano et al., 2008. Avian Pathology. 37:281-287
2. Weissenbock et al., 2005. Vet. Microbiol. 111, 67-75
3. La et al., 2003. J. Clin. Microbiol. 41, 3372-3375
4. Rohde et al., 2002 J. Clin. Microbiol. 40, 2598-2600
5. Phillips et al., 2005. Vet. Microbiol. 105, 189-198.

The paper was presented by L. Bano¹, U. Klein², S. Gianazza³, B. Marcon¹, I. Drigo¹, K. Tevisiol⁴, F. Agnoletti¹, D. Burch⁵.

Istituto Zooprofilattico Sperimentale delle Venezie, Villorba di Treviso, Italy¹, Novartis Animal Health Inc., Basel, Switzerland², Novartis Animal Health S.p.A., Origgio, Italy³, Istituto Zooprofilattico Sperimentale delle Venezie, Bolzano, Italy⁴, Octagon Services Ltd, Old Windsor, UK⁵

at the 6th International Conference on Colonic Spirochaetes in Animals and Humans 2013, University of Surrey, UK. 5-6 September 2013.

September 2013