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From a survey of wild, adult Penaeus monodon of potential broodstock size from the Indian Ocean in April 2018, we obtained positive nested RT-PCR test results for infectious myonecrosis virus (IMNV) and positive nested PCR test results for DIV1. As a confirmatory step, a second round of nested PCR tests was carried out using new, in-house primers designed from regions of the respective viral genomes distant from the target regions used in the first round of tests. These results suggested the possibility that the grossly normal, PCR-positive captured P. monodon specimens might be infected with the respective viruses at the carrier level. If so, they might serve as potential vehicles for introduction of IMNV and/or DIV1 into crustacean culture systems, especially if they were used in hatcheries for production of PL for distribution to shrimp farmers without proper precautions in place.
We carried out laboratory injection challenges that employed extracts prepared from shrimp naturally-infected with decapod iridovirus 1 (DIV1). We found that diseased shrimp from the injection trials showed pathognomonic lesions for DIV1 in the hematopoietic tissue that matched those reported for DIV1 in P. vannamei from China (Qiu et al. 2017. Scientific Reports. 7). In addition, we also found distinctive lesions in the lymphoid organ that could be used as an additional indicator in confirming diagnosis of DIV1 disease. Also, the lesions from shrimp challenged with the 10x dilution were more severe than those from 100x dilution, and for some shrimp in the 100x dilution, the lesions were very clear in the LO but absent in the HPT. Altogether, the results suggested that histology of the HPT and LO could be used together to help in the diagnosis of DIV1 in conjunction with RT-PCR, amplicon sequencing and in situ hybridization (ISH) analysis. This is particularly important in confirming the presence of virulent isolates of DIV1 in new geographical locations.
EHP or Enterocytozoon hepatopenaei is a fungal microsporidian parasite that infects the hepatopancreas (hp) of tiger shrimp (Penaeus monodon) and whiteleg shrimp (P. vannamei) in Thailand and results in slow growth and, in chronic infections, mortalities. EHP is also known from Brunei, China, India, Indonesia, Malaysia, Philippines, Venezuela and Vietnam. This fact sheet provides information on the EHP life cycle, signs of infection, diagnosis and management in both hatcheries and growout, as well technical contacts for further information.
The World Health Organization (WHO) is recommending that farmers and the food industry stop using antibiotics routinely to promote growth and prevent disease in healthy animals. The new WHO recommendations aim to help preserve the effectiveness of antibiotics that are important for human medicine by reducing their unnecessary use in animals. In some countries, approximately 80% of total consumption of medically important antibiotics is in the animal sector, largely for growth promotion in healthy animals.
Tilapia lake virus (TiLV) is an emerging infectious agent that has recently been identified on three continents. While the link between TiLV and disease outbreaks in Israel and Thailand are well documented, further investigations are being undertaken to determine the significance of TiLV in the other countries. This report summarises the available scientific information on TiLV, including clinical signs, diagnostics and epidemiology. Infection with TiLV in tilapia populations may result in socio economic losses and impacts on food security.
Tilapia lake virus is a newly emerging virus that is associated with significant mortalities in farmed tilapia. This fact sheet describes the threat to industry, clinical signs, diagnosis, risk factors, prevention and control options and actions that must be taken to minimise the impact of this disease on the global tilapia aquaculture industry. All countries with a tilapia industry must be vigilant and act quickly to investigate cases of mortalities in farms.
Recently, we released a warning of TiLV in Thailand and an improved RT-PCR detection methodology. The Fish Health Platform in Centex, BIOTEC/Mahidol University has also obtained positive test results for TiLV in other Asian countries where it has not yet been reported. Many countries have been translocating tilapia fry/fingerlings prior to and even after the description of TiLV. We have prepared a map listing countries with confirmed reports of TiLV infections and 43 other countries that we believe have imported infected fish.
This disease card published by the World Organisation for Animal Health (OIE) provides information about tilapia lake virus (TiLV), a recently observed pathogen causing significant mortalities in cultured tilapia. The disease card provides details of the pathogen, modes of transmission, host range, geographical distribution, clinical signs, diagnostic methods, socio-economic significance, transmission risk and a list of available references. We urge laboratories to test for TiLV when abnormal tilapia mortalities occur.
Tilapia lake virus (TiLV) is an emerging disease of cultured tilapia in the Asia-Pacific region. Originally observed and reported in Israel, Ecuador, Colombia and Egypt, TiLV is now confirmed in cultured tilapia in Thailand causing mass mortalities. At risk is here is the US$7.5 billion global industry per annum, especially among the top tilapia-producing countries in the region including China, the Philippines, Thailand, Indonesia, Lao PDR and Bangladesh. This advisory describes signs of the disease and PCR detection methods.
Tilapia lake virus (TiLV) is an emerging virus that causes syncytial hepatitis of tilapia with mortalities of up to 90%. Recent disease outbreaks in Thai tilapia farms have been associated with high cumulative mortalities and histopathological features typical of SHT. Infection has now been confirmed. The semi-nested RT-PCR protocol described here may be used freely for non-commercial applications to detect TiLV. The authors urge laboratories in Asia to test for TiLV when abnormal tilapia mortality occurs.