Is Kobuvirus the Causative Agent of a Pig Enteric Disease?

Porcine kobuvirus with single-stranded RNA genome, also known as Aichivirus C, belongs to the family Picornaviridae. This virus was identified for the first time in Hungary in 2008. The virus was also identified in pigs of several countries with prevalence variation from 3.9 up to 100%. Virus was detected in healthy and diarrheic pigs, often with higher prevalence in diarrheic piglets. In our work we describe the detection of porcine kobuvirus in pigs of different health status and age categories. In addition, the virus 3D gene was also analysed.

Total RNA was isolated using TRIzol from 262 rectal swabs and stool samples collected from diarrheic and healthy pigs of different age on 7 farms in Slovakia in the period 2013 to 2015. Viral RNA was detected using single RT-PCR with primers flanking 495 bp fragment of 3D gene. Twenty PCR products were sequenced. The phylogenetic tree was constructed by the neighbor-joining method of MEGA6.

Of 262 samples originating from the pigs of different age categories, the virus was detected in 63.1% of healthy and 62.7% of diarrheic animals. Kobuvirus RNA was slightly more often detected in piglets (70.8%) than in weaning (60.2%) and finishing (62.3%) pigs. No big differences and strong consistency in age groups were recorded in healthy versus diarrheic suckling piglets (68.6% vs 76.9%) weaning (68.8 vs 53.3%) or finishing (57.1 vs 75.9%) pigs. The analyses of 404 bp long fragment of the 3D gene revealed high genetic similarity of viral isolates (89 – 100%). Virus from healthy and diarrheic pigs was identical when it originated from the same farm. On the other hand, several viral sequences originating from the same farm were variable independently if they originated from healthy or diseased animals but this variability was in the range of phylogenetic cluster.The kobuvirus isolates originating from Slovakia were located in different phylogenetic clusters than viral isolates from Hungary or the Czech Republic. The isolates from Slovakia were rather clustered with Asian isolates than together with isolates originating from Europe.

The analysis of results in this study and results published by other authors did not clearly confirm that kobuvirus is a causative agent of some pig enteric disease since virus was detected in many healthy and diarrheic animals. The suckling piglets are probably more sensitive for kobuvirus infection than older pigs but more extensive study has to be carried out to draw clear conclusion. The phylogenetic analysis indicated that isolates from Slovakia were not closely related to the European isolates.

This work was supported by VEGA project No 1/0342/14 and by project ITMS 26229120002 from EU.

Disclosure of Interest: None Declared.