Characteristics of SRLV genotypes circulating in Polish goat population : A. Moroz-Fik, K. Biernacka, M. Mickiewicz, Z. Nowek, G. Bertoni, C. Abril, S. Stuen, L. Ózsvári, S. Petkevičius, O. Szaluś-Jordanow, E. Bagnicka, I. Markowska-Daniel, J. Kaba, M. Czopowicz

Abstract

Introduction Caprine arthritis-encephalitis (CAE) in goats and maedi-visna disease in sheep are widespread infectious diseases caused by small ruminant lentivirus (SRLV). SRLV is classified into 5 genotypes (A-E) of which A and B are widespread. Both have been reported from Polish goat population, however only small-scale studies were carried out. We aimed to estimated herd-level prevalence of SRLV genotypes. Material and methods The study was carried out in years 2021–2022. Twenty goat herds were randomly selected from 100 herds known to be seropositive for SRLV infection. This sample size allowed herd-level prevalence estimation assuming expected prevalence of 50% and 20% precision. The herds were located in 10 provinces of Poland. They counted from 10 to 500 adult goats (median – 30 goats). All adult goats (>1 year-old) in these herds were blood sampled and screened using an indirect commercial ELISA coated with the panel of synthetic peptides from SRLV structural proteins (ID Screen MVV-CAEV Indirect Screening test, France). Then, the herds were revisited and blood was collected from seropositive goats – all if the number of seropositive goats was below 12, otherwise from 12 randomly selected. This sample size ensured detection of a given genotype if it was present in at least 25% infected goats in a herd. Blood was collected to 10-ml tubes with EDTA, centrifuged (10 min at 3000 rpm), buffy coat harvested and erythrocytes lysed using RBC Lysis Buffer. Then, leukocyte pellets were stored at -20°C until testing. DNA from leukocyte pellets was extracted and the material was tested using a two-stage real-time nested PCR (RT-nPCR) which distinguishes between SRLV genotype A and B. In total, blood samples from 145 seropositive goats were tested using RT-nPCR – from 2 to 12 goats (median – 7 goats) from a herd. Results and discussion The within-herd seroprevalence of SRLV infection ranged from 10% to 96% (median – 36%). Both genotypes were identified – genotype A in 18 herds (90%; CI 95%: 70% – 97%), genotype B in 8 herds (40%; CI 95%: 22% – 61%). Concomitant infection with 2 genotypes was detected in 6 herds (30%; CI 95%: 15% – 52%). Of 145 seropositive goats 123 were positive in RT-nPCR (85%; CI: 95%: 78% – 90%): 95 goats were infected with genotype A (77% of 123 goats), 20 goats with genotype B (16%), and 8 goats with both genotypes (7%).Conclusion and implications Both genotypes A and B of SRLV are responsible for CAE in Polish goats. Genotype A is more prevalent and concomitant infection with both genotypes is not uncommon both at the herd- and animal-level. Acknowledgements and funding The study was financed by the ICRAD CAE-RAPID grant no. ICRAD/I/CAE-RAPID/02/2021.