ABSTRACT
Diagnosis of bovine viral diarrhea (BVD) relies on the detection of antibodies against its viral causing agent, bovine viral diarrhea virus (BVDV). Here, we designed a novel competitive ELISA (cELISA) using the most immunogenic part of BVDV nonstructural protein 3 (NS3), as a single ELISA recombinant antigen, along with a monoclonal antibody to detect antibodies against BVDV in sera of infected animals. Hence, 197 serum samples were tested by this cELISA and the results were compared to the results obtained from virus neutralization test (VNT) as the gold standard method for diagnosis of BVD. McNemar's test indicated that there was no significant difference between the results of this newly designed cELISA and VNT. Meanwhile, kappa coefficients showed that there was a high correlation between these two assays. The relative sensitivity and specificity of cELISA with respect to VNT were 93.90% and 100%, respectively, suggesting that this newly designed cELISA could be a useful diagnostic tool for detection of BVDV infection. Moreover, as NS3 is highly conserved among Pestiviruses and the developed ELISA is a competitive one, it could potentially be applied to detect BVDV infection in other domestic and wildlife species.
ABSTRACT
Aeromonas hydrophila is a bacterium associated with many diseases and disorders such as fin rot, skin ulcers and lethal hemorrhagic septicemia in fish. It bears several virulence factors including type III secretion system (T3SS), aerolysin, cytolytic enterotoxin and enzymes (e.g., hemolysins, lipase) that seem to play an important role in its pathogenesis. Detection of virulence markers by polymerase chain reaction (PCR) is a key procedure in defining the patho-genic ability of pathogenic bacteria and preparing a vaccine for its treatment. In this sense, this study was aimed to determine the frequency of virulence genes in isolates obtained from infected cultured carps in Khuzestan province. Out of 200 moribund carps with septicemic symptoms, 125 isolates were belonged to the motile aeromonads and 59 isolates were identified as A. hydrophila by biochemical methods. Finally, using PCR analysis, 31 isolates were identified as A. hydrophila. Five virulence genes were detected in these isolates including hemolysin, aerolysin, cytolytic enterotoxin and T3SS (aopB and ascV) by specific primers. Results showed that 23 (74.19%), 18 (58.06%), 16 (51.61%), 13 (41.63%) and 10 (32.25%) isolates possessed cytolytic enterotoxin, hemolysin, aerolysin, and T3SS genes, respectively. The results of the present study showed that among 31 isolates, only five isolates had all of dominant virulence genes. Thirteen other isolates had genotypes including hlyA +, aerA + , and act + . The remaining isolates had at least one virulence gene. This study showed that determination of the virulence genes by PCR can be a reliable method to identify a potential pathogenic Aeromonad strain.
