RESEARCH ▶▶▶
pleuropneumoniae, a well-known bacteria causing respiratory disease in pigs. With genetic techniques increasingly becom- ing more sophisticated, strategies to breed (more) resistant pigs appear to come within reach as well. In the context of gene editing, Christine Burkard of the Roslin Institute and Royal (Dick) School of Veterinary Studies, Uni- versity of Edinburgh, UK, gave a very insightful presentation about the different degrees of reaction pigs can have towards a pathogen – from being susceptible to resistant. Delving deep into the porcine genome, she then touched on the gene ‘CD163’, which is associated with resistance to PRRS. In her keynote lecture, she said, “CD163 has been described as a fusion receptor for PRRSv.” Dr Burkard’s team aimed to figure out how to edit this gene – while making sure that the gene does not lose its biological function. They managed to do so, taking out domain 5 (SRCR5) of the gene. The team stated that in vitro, resistance to PRRSv-1 and PRRSv-2 has both been shown; in vivo, the resistance has been shown in PRRSv-1, subtype 2. Dr Burkard and her team, including researchers from Iowa State University, Genus and the Warsaw University of Life Sciences, stated that the pigs without ‘SRCR5’ are fully resist- ant to infection and there is no virus shedding. In addition, the pigs are non-transgenic, she said. She added, “This research shows that genome editing opens new opportunities for next-generation breeding for virus- resistance in livestock and eradication of disease.”
Dr Christine Burkard, Roslin Institute and University of Edinburgh, UK.
Dr Höltig concluded, “Within this study gene markers for a genetic selection of pigs less susceptible to porcine pleuro pneumonia have been developed and the genetic background for the host’s susceptibility was confirmed. As favourable gene variants are segregating in commercial populations further work is needed to investigate preva- lence of favourable and unfavourable gene variants in different breeds and populations and to verify the results of this study.”
4. Crows may help spread swine dysentery Crows may contribute in the spread of Brachyspira hyodys- enteriae, a bacteria causing swine dysentery in pigs has also been isolated from a crow. Researcher Friederike Zeeh from the University of Bern, Switzerland, explained in more detail how her team came to this discovery. She introduced Switzer- land’s swine business saying that about 50% of the herds have free access to outdoor areas. The team of Dr Zeeh was confronted with two neighbouring herds, both with outdoor areas but not having direct contact whatsoever – different owners, different vets, etc. The only thing the two herds had in common was the presence of a flock of carrion crows (Corvus corone). 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. Dr Zeeh described that four 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 two different isolates of B. hyodysenteriae: 1. ST196: found in eight samples of farm 1, in one sample of farm 2
PleuroRes: A solution to App? Not only with regard to PRRS, genetics may prove the way forward. Serious steps have also been made in this respect to overcome respiratory disease related to the bacteria Actinobacillus pleuropneumoniae. In an oral presentation, Dr Doris Höltig, of the University of Veterinary Medicine in Hanover, Germany, presented the most recent results of the project PleuroRes. This project aims to identify genetic markers for resistance to pleuropneumonia in a commercial German Landrace breed. In the study of the presentation, which also included re- searchers from the German Justus-Liebig-University and the Technical University Munich, 165 pigs were used. In total the team managed to find three candidate genes.
8 ▶ PIG PROGRESS | Volume 34, No. 6, 2018
2. ST66: found in five samples of farm 2 and in a crow Dr Zeeh conducted the research together with Suisag, and the University of Veterinary Medicine in Hanover, Germany. She concluded: “This is the first description of B. hyodysente- riae in crows, indicating that crows can potentially also contribute to the dissemination of B. hyodysenteriae.” Adding that more research is needed to elucidate the actual role corvids in this process, she added that biosecurity measures should be taken to keep birds away from pig herds.
Dr Friederike Zeeh, University of Bern, Switzer- land.
PHOTO: VINCENT TER BEEK
PHOTO: VINCENT TER BEEK
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