The confirmation of the presence of Bovine Viral Diarrhea Type 2 in Belgium

Objectives

Bovine Viral Diarrhea Virus (BVDV) is often unexpectedly present in herds. Two genotypes exist: BVDV type 1 and BVDV type 2. In the USA and Canada about 45 % of the genotyped BVD strains belong to the BVDV type 2. In Europe the prevalence of type 2 is estimated at 5 %. Since the first of January 2015 an official BVD eradication program was started in Belgium. In a further evolution of BVD eradication cattle becomes more vulnerable in case of renewed virus contact. Protection on herd level by means of vaccination could proof to be a valuable tool. Therefore it is essential to know if BVDV type 2 is present.

Materials and Methods

In Belgium veterinary practitioners send in samples for diagnosis and monitoring to two official labs (DGZ - Diergezondheidszorg and ARSIA- Association regional de santé et identification d’animaux). In case of BVD analysis those labs mainly use two tests to look for BVD antigen, a BVD Ag ELISA test and a BVD Ag PCR. Analyses were carried out on different matrices. These tests however cannot make the difference between BVDV type 1 and BVDV type 2. The reference lab: CODA-Cerva, disposes of a BVD Ag PCR test which on the other hand can distinguish between BVD type 1 and BVD type 2. In order to obtain samples for further analysis two approaches were taken. First the veterinary practitioners were asked to send in samples when they had a suspicion of BVD, secondly the two official labs were asked to send all their positive BVD Ag samples to the reference lab for typing. Every matrix was analyzed except for ear notch samples. For the majority of these latter samples we don’t have any information on the motives for which these samples were analyzed in the first place. This search was performed in the period between August 2014 and April 2015.

Results

Following the first approach 21 samples were sent in by veterinary practitioners. In these cases there was clearly a suspicion of BVD infection, either by clinical symptoms or by a formal positive spot test i.e. antibody search in young stock to determine virus circulation. Four of these samples were positive for BVD type 2. Two samples originated from two different animals on the same farm; in this case it concerned two confirmed PI (persistently infected) animals. The lab of DGZ in the northern part of the country has sent 113 samples to the CODA-Cerva (the reference lab ). Three of those samples were positive for BVD type 2. The lab ARSIA in the southern part of the country has sent 104 samples to CODA-Cerva. Again three samples were positive for BVD type 2. In case there is already a suspicion by the vet of BVD infection up to 19 % of the samples reacted positive for BVD type 2. It concerns a limited number of samples in a limited period of time. On the other hand, samples sent by the labs DGZ and ARSIA to the lab of reference (CODA-Cerva) 2,76 % were found positive for BVD type 2. In the given period 9 samples were found positive on 8 different farms on a total of 221 samples. This results in 4 % of the samples being positive for BVD type 2. All analyzed samples originated from animals from over the country. Positive samples were traced back to different parts of the country but with a small concentration of some positive samples in the eastern part of the country.

Conclusions

The presence of BVDV type 2 is confirmed in Belgium and matches with the estimated presence of BVD type 2 in Europe. The second approach has shown that BVD type 2 is present without expecting it, since no motive was known for analyzing these samples. This unknown presence of the virus can cause hidden loss on farm level. If the vet has the suspicion of a BVD infection there is a substantial possibility BVD type 2 is present. Fourthly, when in a further evolution of an eradication program protection by vaccination is discussed one needs to be aware that it is necessary to include both types BVD in the protection.

Comments

The author was veterinary practitioner in a cattle practice for 20 years. Then he worked for three years at an Animal health service organization in Belgium. Since April 14, 2014 he joined Boehringer Ingelheim Animal Health as Technical Manager Cattle & Equine.