Prevalence and sequence analysis of equid herpesviruses from the respiratory tract of Polish horses

Abstract

BackgroundEquid herpesviruses (EHVs) are widespread in equine populations worldwide. While the infection with equine α-herpesviruses (EHV-1 and EHV-4) has been linked to several clinical outcomes, the pathogenic potential for equine γ-herpesviruses (EHV-2 and EHV-5) is still unclear. The objective of the current study was to determine the prevalence of infection with EHVs among Polish horses, to investigate factors associated with EHV infections among horses sampled, and to determine genetic variability within Polish EHV-2 isolates.MethodsVirus-specific real-time PCR assays were used for detection of EHV-1, EHV-2, EHV-4 and EHV-5 in nasal swabs collected from 540 horses from 13 national horse studs located throughout Poland. A proportion of EHV-2/5 positive samples were subjected to virus isolation followed by amplification and analysis of partial glycoprotein B sequence.ResultsOverall, 448/540 (83.0%) horses sampled were positive for at least one virus. The most prevalent was infection with EHV-2 (77.2%), followed by EHV-5 (47.0%), and EHV-4 (0.4%). None of the horses was positive for EHV-1. Approximately half of the virus-infected horses were positive for both EHV-2 and EHV-5. The proportion of EHV-2/5 positive horses varied by age, breed, and season. Only 8.0% of horses sampled, mostly Arabians, showed clinical signs of respiratory disease at the time of sampling. The viral load of both EHV-2 and EHV-5 DNA was highest in swabs from young horses, which was particularly evident for EHV-2 infected foals. Mean viral loads in nasal swabs collected from diseased horses were higher than in swabs from healthy horses. That was also true for EHV-2 when only diseased Arabian foals were considered, but the levels of EHV-5 DNA were lower in swabs from diseased than from healthy foals. In agreement with other studies, there was a considerable variability between Polish EHV-2 sequences, with no clustering of sequences from horses with different health status. The level of EHV-2 variability seemed to differ between different studs/breeds.ConclusionsThe presence of foals and yearlings on a property is likely to increase the risk of active EHV-2/5 infection among in-contact horses. The existence of breed-specific differences in susceptibility to EHV-2/5 infections should be further investigated, as it may provide one variable that needs to be considered in attempts to associate EHV-2/5 infections with disease. Overall, the data presented add to the existing knowledge of the epidemiology and biology of equine γ-herpesviruses, with the long-term goal of better understanding of the pathogenesis and the impact of infections with these viruses on the well-being of the horse.

Molecular Detection and Genetic Characteristics of Equine Herpesvirus in Korea

“…More recently in other countries, prevalence observed in nasal swab samples from Poland were EHV-2 (77.2%, 417/540), EHV-4 (0.4%, 2/540), and EHV-5 (47%, 254/540) in horses [19], and in nasal swab and blood samples from Ethiopia they were EHV-1 (3.4%, 4/119), EHV-2 (25.2%, 30/119), EHV-4 (7.6%, 9/119), and EHV-5 (28.6%, 34/119) in horses with respiratory disease or EHV-2 (7.9%, 8/101) and EHV-5 (17.8%, 18/101) in healthy horses [20]. In a previous Korean study, EHV-1 (5.6%, 5/89) and -4 (7.9%, 7/89) by real-time PCR and EHV-5 (39%, 35/89) by conventional PCR were detected only from nasal swabs from horses suffering from respiratory diseases in 2008 [12], and EHV-2 (2.3%, 10/430) and -5 (2.6%, 11/430) by conventional PCR only were detected in genital swabs from healthy horses recently [13].…”

“…Results revealed a higher prevalence of EHV-2 (41.7%) than that of EHV-5 (21.7%) in the blood. Previous studies from Hungary, Sweden, the UK [21], New Zealand [16], Poland [19], and Iceland [22] have also reported that EHV-2 is more frequently detected than EHV-5. However, in this study, lung tissue and nasal swab samples presented with a higher prevalence of EHV-5 (18.7% and 11.2%, respectively) than that of EHV-2 (13.4% and 5.5%, respectively); this finding corresponds with reports from Australia [10], Ethiopia [20], Korea [13], and Turkey [18].…”

Outbreak of equid herpesvirus 1 abortions at the Arabian stud in Poland

“…All samples developed viral cytopathic effect within 2 to 6 days post inoculation. The identity of the viral isolates was confirmed by EHV-1 specific PCR [29,30].…”

“…Following a low-speed centrifugation, supernatants from tissues from the same fetus were pooled and stored at − 80°C. DNA was extracted from 200 μL of each pooled supernatant using QIAamp DNA Mini Kit (Qiagen, Germany) according to the manufacturer's recommendations and tested for the presence of EHV-1 and EHV-4 DNA using previously published primers from the conserved region of glycoprotein B [29,30]. Positive (EHV-1 438/77 and EHV-4 405/76, American Type Culture Collection) and negative (water) controls were included in each PCR run.…”

Detection of Equid gammaherpesvirus 2 and 5 DNA in the upper respiratory tract of asymptomatic horses from Southern Brazil

“…This is the first report of EHV-2 and EHV-5 DNA in the upper respiratory tracts of asymptomatic adult horses from Brazil. Gammaherpesviruses have been detected in horse populations in several countries worldwide [1,15,18,19]. In South America, EHV-2 was successfully isolated from cells cultured from symptomatic horses in Argentina [20,21].…”