White spot syndrome virus (WSSV) transmission risk through infected cooked shrimp products assessed by polymerase chain reaction (PCR) and bio-inoculation studies

The aim of the study was to evaluate the resistance of white spot syndrome virus (WSSV) in shrimps (Penaeus monodon) to the process of cooking. The cooking was carried out at 1000C six different durations 5, 10, 15, 20, 25 and 30 min. The presence of WSSV was tested by single step and nested polymerase chain reaction (PCR). In the single step PCR, the primers 1s5 & 1a16 and IK1 & IK2 were used. While in the nested PCR, primers IK1 &IK2 – IK3 & IK4 were used for the detection of WSSV. WSSV was detected in the single step PCR with the primers 1s5 and 1a16 and the nested PCR with the primers IK1 and IK2 – IK3 & IK4 from the cooked shrimp samples. The cooked shrimps, which gave positive results for WSSV by PCR, were further confirmed for the viability of WSSV by conducting the bio-inoculation studies. Mortality (100%) was observed within 123 h of intra-muscular post injection (P.I) into the live healthy WSSV-free shrimps (P. monodon). These results show that the WSSV survive the cooking process and even infected cooked shrimp products may pose a transmission risk for WSSV to the native shrimp farming systems.

Pathogenicity of Aeromonas hydrophila artificially infected to Indian major carp (Cirrhinus mrigala Ham.)

Abrasion, feeding, injection and immersion methods were used to evaluate the pathogenicity of five different strains of Aeromonas hydrophila viz. RG (rui gill), ML (mrigal lesion), SG (sharpunti gill), F1K (mrigal kidney), GFL (gold fish lesion) and Ah-19 (Aeromonas hydrophila-19, Ref. Strain) against C. mrigala H. Bacterial suspension containing viable cells of 7.5x 10⁵ per ml was found to be very effective in intramuscular injection and feeding resulting 100% mortality after 96hr of inoculation. The strain RG, ML and F1K produced scale loss with erosion of the skin surface with/without hemorrhagic lesion after 48hr of inoculation following abrasion method. The strains SG and Ah-19 resulting scale loss with erosion of the skin surface with/without hemorrhagic lesion after 72hr of inoculation following abrasion and injection methods. SG and F1K caused reddening in mouth region after 72hr of feeding inoculation, whereas RG resulted frank ulcers from eroded dermal layer exposing underlying musculature which was hemorrhagic after 96hr of inoculation by abrasion method.

Major histocompatibility complex class I involvement in the rejection of allogeneic erythrocytes in rainbow trout (Oncorhynchus mykiss)

Major histocompatibility complex genes are thought to be involved in allogeneic graft rejection but not many reports are available on their functional analysis in fish. Analysis of available sequences of MHC genes suggests functions in antigen presentation similar to those found in higher vertebrates. In mammals, the MHC class I and class II molecules are major determinants of allogeneic graft rejection due to their polymorphism in conjunction with their antigen presenting function. In fish, MHC class H molecules are found to be involved in rejection of allogeneic scale grafts. The present study was designed to investigate the involvement of MHC class I molecules in allograft rejection. Erythrocytes were collected from donors of rainbow trout expressed different class MHC class I alleles, stained with two dyes, mixed and grafted to the recipients that were of the same sibling group as the donors. The grafts were rejected by allogeneic recipients and the MHC class I linkage group was the major determinant for the rejection.