|Blood, K. Shawn|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/25/2009
Publication Date: 1/25/2009
Citation: Fulton, R.W., Ridpath, J.F., Hessman, B.E., Blood, K.S. 2009. Bovine Viral Diarrhea Virus Variability and Prevalence of BVDV Subtypes in Persistently Infected Cattle Entering Feedlots: BVDV1b as Predominant Subtype [abstract]. 4th U.S. BVDV Symposium. Paper No. 1-5. Interpretive Summary:
Technical Abstract: Aim: Bovine viral diarrhea viruses (BVDV) are a diverse group of viruses causing infections and disease in domestic and wild ruminants worldwide. BVDV biotypes are based on presence or absence of cytopathology in infected cultures: CP (cytopathic) or NCP (noncytopathic). BVDV are genetically diverse based on nucleic acid sequence differences and these are reflected by antigenic differences. In North America the BVDV subtypes include BVDV1a, BVDV1b, and BVDV2a. BVDV subtypes have been identified in diagnostic laboratory isolates from clinical and necropsy cases1. Persistently infected (PI) animals represent the major reservoir of infection to expose susceptible cattle. Commercial vaccines in the US contain BVDV1a and BVDV 2a subtypes. The purpose of this study was to determine distribution of BVDV subtypes in PI cattle entering two feedlots, and to examine over a four interval the distribution of the BVDV subtypes in PI cattle of one feedlot. Methods: Samples were collected from cattle in feedlot #1 located in southwest Kansas and had been identified as PI based on antigen capture ELISA (ACE). Samples were from the initial collection in 2004 and multiple collections were submitted yearly through the fall 2008. PI cattle were sampled subsequently with fresh and formalin notches collected for ACE and immunohistochemistry (IHC) and serums submitted for viral sequencing for subtype classification.2 During 2007 and 2008, samples were collected from a feedlot #2 in Oklahoma with PI status of the cattle determined by ACE and IHC. Serums were collected for viral subtyping. The viruses were subtyped based on the sequencing of a region of the 5'-UTR of the viral genome3. Results: PI animals from 2004 to 2008 from the southwest Kansas feedlot had seven groups of PI cattle and the subtype distribution for the 1155 cattle included 140 (12.1%) BVDV1a; 904 (78.3%) BVDV1b; and 111 (9.6%) BVDV2a. Individual groups in the 2004-2008 interval and distribution were : (1) 2004-2005, 86 PI cattle with 11.6% BVDV1a, 77.9% BVDV1b, and 10.5% BVDV2a; (2) 2005-2006, 318 PI with 11.6% BVDV 1a, 75.8% BVDV1b, and 12.6% BVDV2a; (3) 2007 Spring , 201 PI with 13.9% BVDV1a,80.1% BVDV1b, and 6.0% BVDV2a; (4) 2007 Summer, 184 PI , 7.1% BVDV1a, 82.6% BVDV1b, 10.3% BVDV2a; (5) 2007 Fall , 163 PI with 14.7% BVDV1a, 76.1% BVDV1b, 9.2% BVDV2a; (6) 2008 Spring, 179 PI , 15.1% BVDV1a, 76.0% BVDV1b, 8.9% BVDV2a; and (7) 2008 Fall, 24 PI , 4.2% BVDV1a and 95.8% BVDV1b with no BVDV2a. The Oklahoma feedlot in 2007-2008 had 30/7497 PI cattle (0.4%). The subtype distribution based on 19 available isolates was: BVDV 1b (68.4%), BVDV1a (21.1%) and BVDV2a (10.5%). Conclusions: BVDV1b is the predominant BVDV subtype in PI cattle entering two feedlots in Kansas and Oklahoma. BVDV1b predominance in the southwest Kansas feedlot is consistent from 2004 to 2008. Current vaccines contain the BVDV subtypes (BVDV 1a and BVDV2a) which are the lowest prevalence. Vaccines should be evaluated for their ability to induce protection against BVDV, or BVDV 1b vaccines should be developed. References: 1. R. W. Fulton et al., Veterinary Microbiology, 111, 35-40, 2005. 2. R. W. Fulton et al., JAVMA, 228, 578-584, 2006. 3. J.F. Ridpath et al., Veterinary Microbiology, 114, 196-204, 2006.