Examination of the early infection stages of koi herpesvirus (KHV) in experimentally infected carp, Cyprinus carpio L. using in situ hybridization

Abstract

Koi herpesvirus (KHV) causes a highly infectious disease afflicting common carp and koi, Cyprinus carpio L. Various molecular and antibody-based detection methods have been used to elucidate the rapid attachment and dissemination of the virus throughout carp tissues, facilitating ongoing development of effective diagnostic approaches. In situ hybridization (ISH) was used here to determine the target tissues of KHV during very early infection, after infecting carp with a highly virulent KHV isolate. Analysis of paraffin-embedded tissues (i.e. gills, skin, spleen, kidney, gut, liver and brain) during the first 8 h and following 10 days post-infection (hpi; dpi) revealed positive signals in skin mucus, gills and gut sections after only 1 hpi. Respiratory epithelial cells were positive as early as 2 hpi. Viral DNA was also detected within blood vessels of various tissues early in the infection. Notable increases in signal abundance were observed in the gills and kidney between 5 and 10 dpi, and viral DNA was detected in all tissues except brain. This study suggests that the gills and gut play an important role in the early pathogenesis of this Alloherpesvirus, in addition to skin, and demonstrates ISH as a useful diagnostic tool for confirmation of acutely infected carp.

Cyprinid Herpesvirus 3

“…This mode of inoculation led to the dissemination of the infection to the various organs tested, inducing clinical signs and mortality rates comparable to the infection by immersion (Fournier et al, 2012). More recently, Monaghan, Thompson, Adams, Kempter, and Bergmann (2015) claimed that the gills and gut represent additional portals of entry by using ISH analysis. In this report, several organs were tested after infection by immersion and positive signal was detected as early as 1-2 hpi in gills, gut, and blood vessels of internal organs.…”

Antiviral activities of Clinacanthus nutans (Burm.f.) Lindau extract against Cyprinid herpesvirus 3 in koi (Cyprinus carpio koi)

“…These results were possibly due to the rapid spread of viral infection in fish. Work by Monaghan, Thompson, Adams, Kempter, and Bergmann () showed early detection of CyHV‐3 viral DNA from gill and skin as soon as 8 hr post‐infection. That virus was also detected in kidney and blood after 1 day post‐infection, indicating that viremia had been initiated (Pikarsky et al., ).…”

In situ localization and tissue distribution of ostreid herpesvirus 1 proteins in infected Pacific oyster, Crassostrea gigas

“…A system to score levels of IHC staining in tissues was established: -= no signal, + = low signal, ++ = moderate signal, and +++ = high signal. This approach was used by Monaghan et al (2015) to examine the early infection stages of koi herpesvirus (KHV) in carp Cyprinus carpio L. using ISH.…”