Using Nucleic Acid Detection And Its Effects On Sequencing And Availability Of Nucleotide Sequences Of Many Bvdv Strains

Using Nucleic Acid Detection And Its Effects On Sequencing And Availability Of Nucleotide Sequences Of Many Bvdv Strains

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2.7.1.3. Nucleic acid detection
There are a lot of improvement in BVDV molecular diagnostic due to enhancement in sequencing and availability of nucleotide sequences of many BVDV strains worldwide (Dubovi 2013). The BVDV belongs to RNA viruses that characterized by a high mutation rate. Therefore, Continuous sequencing and development of new diagnostics are very important to pick up any new strains (Liu et al. 2008). One of the obstacles in BVDV molecular diagnostic is an absence of laboratory to laboratory standardization. However, there a lot of improvement after USDA approval of BVDV RT-PCR diagnostic kit (Dubovi 2013).
The RT-PCR is commonly used as a routine for diagnosis of BVDV. Therefore, it is widely accepted that RT-PCR is the standard for BVDV diagnosis (Herting et al. 1991; Lanyon et al. 2014). The advantages of RT-PCR in comparison to viral isolation are less time consuming, less expensive, did not require cell culture facilities and high sensitivity (Kim and Dubovi, 2003; Houe et al., 2006). The RT-PCR test can detect PI animals, transiently infected animals and vaccinated animals with live attenuated vaccines. Therefore, retesting of positive animals after several weeks is required to know the infection status (Bhudevi and Weinstock 2003).
The higher sensitivity of RT-PCR assays enables pooling of clinical samples, it has been previously reported that testing of pooled bulk tank milk samples by RT-PCR can detect one PI animal in a herd of 132 animals or two PIs in a herd of 800 animals (Renshaw et al. 2000; Hill et al. 2010). Smith et al. (2008); Yan et al. (2011) reported that one PI animal can be detected by RT-PCR in a pool of 50 serum samples.
The 5´ UTR is highly conserved among different BVDV species. Theref...


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...een isolated from affected calves. It is speculated that the source of NCP strains may be MLV vaccines (Fulton 2005). In another study, pregnant heifers have been challenged only by CP BVDV strains, the results indicates occurrence of fetal infection and only NCP biotypes have been isolated (Done et al. 1980). All those studies enforce the speculation of contamination of MLV vaccines by NCP biotypes.
The major concern of using BVDV MLV is the postvaccinal disease. It has been previously reported that mucosal disease occurred after vaccination with MLV vaccine. The MD may be developed as a result of superinfection of vaccinated PI calves by homologous CP strains originated from vaccines (Bittle 1968; Lambert 1973). In addition, the cause of postvaccinal may be the contamination of fetal bovine serum by NCP biotypes of BVDV (Bolin and Ridpath 1998; Studer et al. 2002).

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