Equine herpesvirus infections in yearlings in South-East Queensland

Abstract

SummaryTwelve nasal swabs were collected from yearling horses with respiratory distress and tested for Equid herpesvirus 1 (EHV-1) and Equid herpesvirus 4 (EHV-4) by realtime PCR targeting the glycoprotein B gene. All samples were negative for EHV-1; however 3 were positive for EHV-4. When these samples were tested for EHV-2 and EHV-5 by PCR all samples were negative for EHV-2 and 11 were positive for EHV-5. All three samples that were positive for EHV-4 were also positive for EHV-5.These three samples gave a limited CPE in ED cells reminiscent of EHV-4 CPE.EHV-4 CPE was obvious after 3 days and was characterised by syncytia. None of the samples produced cytopathic effect (CPE) on African green monkey kidney (Vero) cells or hamster kidney (BSR) cells. Four of the samples, which were positive in the EHV-5 PCR, produced CPE on rabbit kidney (RK13) cells and equine dermis (ED) cells. EHV-5 CPE on both cell lines was slow and was apparent after four 7-day passages. On RK13 cells the CPE was characteristic of equid herpesvirus with the formation of syncytia. However in ED cells, the CPE was characterised by ringshaped syncytia.For the first time a case of equine respiratory disease involving dual infection with EHV-4 and EHV-5 has been reported in Queensland. This was shown by simultaneously isolating EHV-4 and EHV-5 from clinical samples. EHV5 was recovered from all samples except one, suggesting that EHV5 was more prevalent in young horses than EHV2.

Molecular Detection and Genetic Characteristics of Equine Herpesvirus in Korea

“…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]. When measured in different sample types such as peripheral blood mononuclear cells, conjunctival swabs, nasal swabs, or blood, comparable results were discovered in other countries [8,21,23].…”

“…To identify EHV-1, -2, -4, and -5 in each specimen, we used sensitive one-step PCR targeting the conserved sequence of the glycoprotein B gene [20]. PCR amplifications were conducted with a validated pair of primers as described previously, in that individual amplicon size was 190 bp for EHV-1 [26], 444 bp for EHV-2 [10], 677 bp for EHV-4 [26], and 293 bp for EHV-5 [27], for glycoprotein B gene detection and nucleotide sequencing. For each PCR reaction, a sample without DNA was used as a negative control.…”

“…Their true pathogenic importance remains uncertain because of their frequent isolation from healthy horse populations and high seroprevalence globally [8]. However, some reports have linked these EHV strains with respiratory diseases [9,10].…”

Age-dependent prevalence of equid herpesvirus 5 infection

“…The different results between younger and older horses could be linked to the different viral phases, with a decreasing amount of virus in older horses, probably latently infected, in comparison to younger mainly acutely infected horses. The young age is more frequently associated with EHV-5 infection and it could represent a confounding factor, in the way that the detection of EHV-5 could be incorrectly considered in association with some pathological condition if an adequate control of healthy animals of the same age is not present in the study (Dynon et al 2007;Diallo et al 2008).…”

Detection and Sequence Analysis of Equine Gammaherpesviruses from Horses with Respiratory Tract Disease in Turkey

“…Isolation and genetic characterization of EHV‐2 and EHV‐5 viruses have been carried out worldwide (Browning and Studdert, 1987a; Holloway et al., 1999; Sharp et al., 2007; Wang et al., 2007; Diallo et al., 2008; Fortier et al., 2009; Richter et al., 2009). Previous studies (Murray et al., 1996; Borchers et al., 1997; Dunowska et al., 2002) report that EHV‐2 was an infectious agent in horses showing clinical signs of respiratory infections, but limited information on the role of EHV‐5 in equine respiratory disease exists.…”