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Crows may help spread swine dysentery

Crows may contribute in the spread of Brachyspira hyodysenteriae. A bacteria causing swine dysentery in pigs has also been isolated from a crow.

The discovery was made public at the most recent edition of the International Pig Veterinary Society (IPVS) Congress, held in Chongqing, China, from 11-14 June, 2018. Researcher Friederike Zeeh from the University of Bern, Switzerland, explained there in more detail how her team came to this discovery.

A carrion crow, photographed on a tree in the UK. Photo: Wikipedia
A carrion crow, photographed on a tree in the UK. Photo: Wikipedia

Pigs with free access to outdoor areas

She introduced Switzerland’s swine business saying that about 50% of the herds have free access to outdoor areas. The team of Dr Zeeh was confronted with 2 neighbouring herds, both with outdoor areas but not having direct contact whatsoever – different owners, different vets, etc. The only thing the 2 herds had in common was the presence of a flock of carrion crows (Corvus corone).

Dr Friederike Zeeh, speaking at the IPVS Congress.
Dr Friederike Zeeh, speaking at the IPVS Congress.

Dr Zeeh pointed out that in the past, B. hyodysenteriae has been found in rheas, geese, ducks and chickens – and that other types of Brachyspira have been found in corvids. The current combination, however, was not described before.

What bacteria did the crows carry?

Dr Zeeh described that 4 crows in the neighbourhood of the farms were shot by hunters to get a good idea as to what bacteria the birds carried in their intestines. In addition, the team sampled faeces from the pigs from both farms.

The team found 2 different isolates of B. hyodysenteriae :

 

  1. ST196: found in 8 samples of farm 1, in 1 sample of farm 2
  2. ST66: found in 5 samples of farm 2 and in a crow

 

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Dr Zeeh conducted the research together with Suisag, and the University of Veterinary Medicine in Hanover, Germany. She concluded: “This is the 1st description of B. hyodysenteriae in crows, indicating that crows can potentially also contribute to the dissemination of B. hyodysenteriae.”

She added that biosecurity measures should be taken to keep birds away from pig herds.

More research is needed to elucidate the actual role of corvids in the epidemiology of Brachyspira hyodysenteriae.

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