Research into three new emerging pathogens


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Research into three new emerging pathogens


Monitoring data from recent years shows an increase in a number of bacterial diseases. More insight into the incidence, spread, genetic variation and pathogenic potential is an important step in tackling these bacteria. GD was commissioned by the poultry sector to study three bacteria: Gallibacterium anatis, the erysipelas bacterium (Erysipelothrix rhusiopathiae) and the ORT bacterium (Ornithobacterium rhinotracheale).

Gallibacterium anatis

Gallibacterium anatis (GBA) is a relatively new emerging bacterium in commercial poultry farming, both nationally and internationally. Just like Escherichia coli (E. coli) and Enterococcus cecorum (E. cecorum), this bacterium is part of the normal flora of a chicken’s trachea and intestines. However, under certain circumstances (due to stress or in combination with other infections, for example), GBA can result in issues such as laying problems, fertilisation problems and increased losses.

What is the significance of this bacterium for the poultry sector and should preventative measures be taken? In 2021, a first step was taken towards answering these questions. What became apparent?

• There is a high incidence of GBA carrier status in Dutch poultry;
• GBA is regularly found in disease processes in combination with E. coli;
• There is a lot of variation between flocks and within flocks;
• In terms of manifestation and genetic variation, GBA somewhat resembles E. coli and E. cecorum.

Further research in 2022 is important, for instance to determine whether there is a relationship between GBA and abnormalities found in the disease processes. Why? If certain GBA genotypes are associated with disease, this may be of importance to the approach taken, by improving the composition of autovaccines for example.

Erysipelas (Erysipelothrix rhusiopathiae)

Erysipelas is caused by the bacterium Erysipelothrix rhusiopathiae (ERH). In poultry, erysipelas causes skin abnormalities and increased losses due to peritonitis and sepsis. If an infection has been diagnosed in a previous flock, newly established flocks are often vaccinated against erysipelas in order to prevent new outbreaks. However, a previous practical study (2019) showed a continued risk of losses caused by erysipelas, even after vaccination. The effectiveness of a vaccine is potentially linked to the difference between the surface molecules of the bacterium used in the vaccine and the surface molecules of the bacterium causing the new outbreak. The gene responsible for expression of an important surface molecule is the Spa gene.

A practical study in 2021 showed among other things:

• Isolates from various animals are identical within an outbreak;
• There is no clear distinction between swine/poultry, country of origin, region in the Netherlands, or years of isolation;
• Based on the Spa gene, three different clusters can be distinguished that could potentially be used to improve the composition of autovaccines.

Further research will focus on monitoring and a more detailed study of the differences in the Spa gene, under the hypothesis that the Spa gene is important for the composition of autovaccines and other vaccines.

ORT bacterium (Ornithobacterium rhinotracheale)

The difference in pathogenic potential of the various Dutch ORT strains in this study was examined in an embryo lethality test, from which the following conclusions can be drawn:

• Based on these results, embryo lethality tests do not seem to be of added value to research into the pathogenic potential of ORT strains.
• ORT strains isolated from clinical conditions seem to be related. However it is not known which strains are currently circulating in the Netherlands, nor whether strains from the ‘cluster’ have a higher pathogenic potential than other ORT strains (not genetically related to the cluster). This follow-up step will be taken in 2022.

More information

This practical veterinary study is part of the 2021 research and innovation programme of the poultry sector. This programme is coordinated by AVINED and financed by the poultry sector. Read more here about practical veterinary studies pertaining to the poultry sector.

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