Subgroup determination of group A rotaviruses recovered from piglets in Nigeria.

Subgroup analysis using subgroup-specific monoclonal ELISA revealed a preponderance of subgroup 2-specific antigens of group A porcine rotaviruses over subgroup 1. Of 113 polyacrylamide gel electrophoresis-positive test samples, obtained from 4 States of Nigeria, 31 (27.4%) and 45 (39.8%) were determined to have subgroup 1 and 2 specificities, respectively. However, 37 (32.7%) test samples could not be classified into any of the known group A rotavirus subgroups. These "unclassifiable" samples probably had neither subgroup 1 nor 2 specificities in ELISA or could belong to a third subgroup unknown or not investigated in this study. In all age groups investigated, subgroup 1 and 2 specific antigens were prevalent. This was also observed after yearly analysis of subgroup specificity; however, a higher prevalence of subgroup 2 specificity was observed in 1990 and 1991. Subgroup 1 rotaviruses were found in all the 4 States sampled (Plateau, Benue, Oyo, and Cross River), whereas subgroup 2 rotaviruses were detected only in Plateau State. All rotaviruses recovered in this study had long genome electrophoretic migration patterns, irrespective of subgroup. Thus genomic diversity of group A rotaviruses does not necessarily reflect antigenic diversity, as there is no mandatory correlation between genome electropherotype pattern and subgroup specificity.

Detection of rotavirus antigen in diarrhoeic and non-diarrhoeic piglets in Nigeria.

Faecal samples from 96 piglets with acute gastroenteritis and 41 samples from non-diarrhoeic piglets were investigated for porcine rotavirus (PRV) antigens by enzyme-linked immunosorbent assay (ELISA). PRV was detected in 43 of 96 (44.8%) in the diarrhoeic group whilst none of the samples in the non-diarrhoeic group was positive for PRV (P less than 0.01). Age distribution of infection showed a higher infection rate of 30.2% in piglets aged 1-3 weeks, which was significantly higher (P less than 0.05) than in piglets aged 4-6 weeks, where the infection rate was 14.6 per cent. No PRV antigen was detected in diarrhoeic piglets above 6 weeks of age. Titration of 10 randomly selected ELISA-positive samples showed titres ranging from 512 to greater than or equal to 4.096.