Archives

  • 2018-07
  • 2018-10
  • 2018-11
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • 2021-07
  • 2021-08
  • 2021-09
  • 2021-10
  • 2021-11
  • 2021-12
  • 2022-01
  • 2022-02
  • 2022-03
  • 2022-04
  • 2022-05
  • 2022-06
  • 2022-07
  • 2022-08
  • 2022-09
  • 2022-10
  • 2022-11
  • 2022-12
  • 2023-01
  • 2023-02
  • 2023-03
  • 2023-04
  • 2023-05
  • 2023-06
  • 2023-08
  • 2023-09
  • 2023-10
  • 2023-11
  • 2023-12
  • 2024-01
  • 2024-02
  • 2024-03
  • 2024-04

    • Senexin B br Discussion Rapid detection of viral pathogens i

    2018-11-03


    Discussion Rapid detection of viral pathogens in post-larvae would be very essential for effective health management in aquaculture. Both one step methods and nested PCR methods have been described for detection of WSSV. The nested PCR amplification procedure is 103–104 fold more sensitive than the one step PCR method [21,20]. The carrier state of WSSV gives only nested PCR test results [33]. Introduction of stress to shrimp by environmental factors such as pH, salinity, temperature, water level [12] may convert the pre-patent carrier state to the patent infecting state within few days or even hours [13,18,32,33] there by giving a first step PCR positive reaction. The presence of WSSV has been reported in wild broodstock from Taiwan, Japan and India [19,30,39]. The prevalence of WSSV in post-larvae has been found to be much lower compared to the prevalence in broodstock [19,39]. The presence of WSSV has been reported in apparently healthy post-larvae by PCR [19,30,23,29,39]. In the present study, WSSV was detected in 2.9% of the post-larvae tested by first step PCR and 12.5% by nested PCR. WSSV has been found to be highly prevalent among post-larvae samples from hatcheries of India. The 12.5% prevalence of WSSV in post-larvae reported in this study is comparatively lower than 75% prevalence reported by Otta et al. [29] but was similar to 12.4% prevalence reported by Uma et al. [39]. The PCR primers used for the detection of MBV gave an amplified product of 533 bp for the first reaction and a 361 bp fragment in the nested reaction. Mortalities of shrimp larvae due to MBV have been reported in many countries [1,24]. MBV is reported to be well tolerated by P. monodon[5,17]. The prevalence of MBV in post-larvae ranged from 25% to 92% in various hatcheries in India [36,30,39]. MBV is transmitted by oral route from water contaminated with virus from fecal Senexin B of brood stock [4]. MBV was found to be prevalent in almost 40% of the wild shrimp seed in Vietnam by histological examination [11]. MBV has also been reported in female brood stock in Thailand with a prevalence of 33% in 1987 and 100% in 1989 [15]. The results of this study indicate a very low prevalence of MBV in post-larvae from hatcheries of India compared to 68–92% prevalence by a wet squash method [36] and 39–54% by PCR [29,39]. The low levels of infection the post-larvae in the present study may be due to improved hygiene practices in the hatchery. HPV was reported in wild P. monodon and hatchery reared larvae with prevalence ranging from 31% to 62% [41,25,40]. All the post-larval samples were negative for HPV with the primers described by Pantoja and Lightner [31]. The results of the present study indicate that the strains of HPV present in the post-larval samples are similar to that of HPVmon isolated from P. monodon from Thailand and not HPVchin isolated from P. monodon in China. Umesha et al. [40] also reported the presence of only HPVmon in P. monodon from shrimp ponds from India. P. monodon infected with HPV rarely show gross signs of disease [38]. However Umesha et al. [40] has noted no difference in production in HPV infected and HPV uninfected farms. Multiple virus infection with MBV, HPV and WSSV in P. monodon post-larvae in India has been implicated as cause for mortality [24]. In the present study, HPV was present in 62.5% of the post-larval samples. IHHNV is one of the highly pathogenic viruses of penaeid shrimp and has been studied since its discovery in 1983. IHHNV was found in 51.5% of penaeid shrimp culture in China [44]. The prevalence of IHHNV from wild caught L. vannamei broodstock captured off the Pacific coast of Panama was 20% by dot blot assay [27]. The virus can be transmitted horizontally through ingestion of infected and dead animals [3,22]. The virus can be transmitted vertically also from infected females to the embryos [26]. In the present study, IHHNV was present in 76% P. monodon post-larval samples. IHHNV infection is found to be well tolerated by P. monodon[16,8,9]. However there is a possibility of transmitting the virus to species that are susceptible.