Rapid Detection of the Philippine Isolate of Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) in Shrimp, Penaeus monodon Using Loop- Mediated Isothermal Amplification (LAMP)

Abstract: The aim of this study was to standardize a Loop-Mediated isothermal Amplification (LAMP) assay for the detection of the Philippine isolate of Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) in postlarvae of shrimp, Penaeus monodon. The assay was optimized at an incubation time of 1 h at 63 o C. The assay was highly specific for IHHNV and did not cross-react with other shrimp viruses including Hepatopancreatic Parvovirus (HPV), Monodon Baculovirus (MBV) and White Spot Syndrome Virus (WSSV). The limit of detection of the IHHNV using the LAMP assay was 10 pg of DNA/mL or 10 fg of the genomic DNA per LAMP reaction and was 10 times more sensitive than conventional PCR in detecting the viral pathogen from infected samples. These results demonstrated that LAMP is a simple and sensitive diagnostic technique that has potential application for routine detection of IHHNV infections in shrimp hatcheries in the Philippines

Histological Changes in the Hepatopancreas and Stomach of Litopenaeus vannamei Experimentally Induced with White Spot Syndrome Virus Infection

Litopenaeus vannamei is an important aquaculture species in the Philippines and in the world. Its production continues to increase due to its fast growth and lower protein requirement, making it a favorable species to culture. However, sustainability of the this industry is hampered by the occurrence of viral diseases. White spot syndrome virus (WSSV) is considered the most devastating shrimp viral pathogen which can cause up to 100% mortality few days upon the onset of the infection. To understand the rapid mortality of the infected shrimps, this study examined histological changes in the stomach and hepatopancreas of Litopenaeus vannamei induced with WSSV infection. Results showed that cells in the stomach of infected L. vannamei undergo cellular abnormalities including hypertrophied nucleus, chromatin margination and basophilic inclusion bodies. The hepatopancreas was also observed to present basophilic inclusion bodies and chromatin margination. Disruption of the tubular epithelium in the hepatopancreas were further observed. These cellular damages that result to tissue and organ destruction as the infection progresses lead to the loss of the functions of these organs which probably contributed to the rapid mortality of shrimp infected with WSSV