Quantitative analysis of infectious precocity virus load and stunted growth syndrome via an immunohistochemical assay and reverse transcriptase quantitative real-time PCR in Macrobrachium rosenbergii

• Published in: Aquaculture Vol. 583; p. 740577
• Main Authors: Chiang, Yun-Ru, Lu, Ya-Yun, Lin, Han-You
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.03.2024
• Subjects: Comparison diagnosis methods; Infectious precocity virus; iron prawn syndrome; Macrobrachium rosenbergii; Viral load in reverse transcriptase quantitative real-time PCR; iron prawn syndrome; Comparison diagnosis methods; Viral load in reverse transcriptase quantitative real-time PCR; Macrobrachium rosenbergii; Infectious precocity virus
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2024.740577

The giant freshwater prawn Macrobrachium rosenbergii (M. rosenbergii) is susceptible to a flavivirus known as the infectious precocity virus (IPV). The symptoms of infection, such as sexual precocity and stunted growth, collectively constitute what is referred to as iron prawn syndrome (IPS). IPV manifests as a persistent, long-term infection marked by subtle morphological changes that pose challenges for detection. Prawns suspected of early-stage infection do not necessarily present clear clinical signs. This study investigated IPV diagnostics based on clinical signs, immunohistochemistry (IHC), and reverse transcriptase quantitative real-time PCR (RT-qPCR) in prawns suspected of IPV-infection. We also explored the correlations among the three diagnostic approaches. Some clinical signs are easily observable, such as shorter body length, mature gonads, elongated blue claws, blue tailfins, and darker body coloration; however, they are not absolute signs of infection. Additionally, many infected prawns do not exhibit clear clinical signs during the early stages. We produced anti-IPV serum and then applied it via IHC staining to highlight the location of the virus. Positive signals were observed in the perinuclear cytoplasm of haemocytes in the hepatopancreas, gills, and pereiopods. IPV-positive signals were also detected in support cells within the lamina ganglionaris as well as in neurosecretory cells within the bellonci organ, sinus glands, and the X organ. The detection of IPV-positive signals in prawns without clinical signs demonstrates the value of this diagnostic method. IHC analysis was used to distinguish between IPV-positive and IPV-negative prawns, and also used in conjunction with RT-qPCR to quantify viral loads in these two groups. The IPV viral loads were as follows: IHC-positive prawns (> 103.5 copies/ μg) and IHC-negative prawns (< 103.5 copies/ μg). Note that the highest numbers of viral copies were observed in pleopods, which are easily obtained and do not necessitate sacrificing the animal. In conclusion, the correlation between viral load and IHC pathological diagnosis could be used to identify cases of IPV infection, while providing valuable insights into disease prevention and prognosis. •Offering an advanced diagnostic tool using infectious precocity virus (IPV) antiserum to highlight virus location and enhance iron prawn syndrome (IPS) diagnosis.•IPV positive signals are identifiable in eyestalk neurosecretory cells, and the perinuclear cytoplasm of haemocytes in the hepatopancreas, gills, and pereiopods during IHC analysis.•Pleopods serve as effective, non-lethal sampling specimens for IPS diagnosis.