An investigation of group and subtype diversity and distribution of porcine rotaviruses in Canadian suckling piglets with diarrhea, 2019-2023

Objective: To determine the frequency of detection and group diversity of rotavirus (RV) A, B, and C, and G (glycoprotein antigen) serotype (based on viral protein 7 [VP7] gene analysis) infecting suckling piglets with diarrhea in Canadian farms. Materials and methods: Canadian swine veterinarians submitted 1117 enteric samples from suckling piglets between July 2019 and December 2023 to the University of Guelph Animal Health Laboratory for RV group identification and VP7 sequencing for subtyping. Analysis of the VP7 sequence from 837 samples was performed using the Animal Health Sequivity Dashboard (Merck & Co, Inc) and descriptive statistics. Results: Rotavirus A, B, and C were present in 40.7%, 12.5%, and 46.8% of samples, respectively. The most common RV identified was RVC G6, present in 296 samples, followed by RVA G9 in 205 samples. A single RV group was involved in 444 cases (72.3%), while in 170 cases (27.7%), more than one RV group/subtype was detected. Eighteen subtypes were identified by sequencing the VP7 protein (5 RVA, 9 RVB, and 4 RVC). Implications: Rotavirus protection for suckling piglets comes from colostrum and milk. Knowing which RV group is causing diarrhea is important since vaccination does not generate cross-protection among groups. Using molecular diagnostic testing, it is possible to identify the specific group and subtype of RV circulating on the premises and decide the best treatment strategy for the disease.