Quality biological sampling is a fundamental requirement for all kinds of work on diagnosing diseases and screening for pathogens. Fish sampling requires specific techniques and skills to collect good biological samples for accurate disease diagnosis. This package of practices developed by WorldFish and partners provides advice on fish sampling protocols for routine disease diagnostics and outbreak investigations in tilapia, carp and catfish production systems. These sampling protocols provide guidance and training to project team members, researchers, resident veterinarians, extension officers and farmers tasked with collecting quality biological samples for laboratory diagnosis whenever disease outbreaks occur on farms or hatcheries. A free online introductory course on fish sampling for disease diagnostics is also available via Learn.ink.

To assist shrimp pathologists worldwide we are providing here photomicrographs of unique basophilic inclusions that are produced by Wenzhou shrimp virus 8 (WZV8),  discovered in 2015 by Li et. al. We designed PCR primers and in situ hybridization probes for detection of WZV8. Subsequent ISH assays with shrimp RT-PCR positive for WZV8 samples indicate unique inclusions described herein as linked to WZV8 in H&E stained tissues. Going back over our previous histological reports and archived slides, we have found the unique WZV8 inclusions in E-cells of normal shrimp samples from several shrimp farming countries in Austral-Asia since at least 2008, and more recently in samples of P. vannamei from the Americas. We urge shrimp pathologists to review their records and specimens for the presence of WZV8 E-cell inclusions described herein to provide data on the global prevalence and impact of WZV8-like infections.

In 2015, a bacterium called Streptococcus agalactiae, also referred to as Group B Streptococcus (GBS), caused a foodborne disease outbreak involving at least 146 people in Singapore, associated with the consumption of raw freshwater fish. The specific strain responsible for the outbreak was later identified as sequence type 283 (ST283). Invasive GBS ST283 disease is also found in other countries in and around Southeast Asia. FAO has published a fact sheet and a risk profile for GBS ST283, which are available for free download. These documents provide guidance on risk reduction, and practical recommendations for food safety competent authorities.

This disease advisory describes the history, known host range, clinical signs and PCR detection methods for viral covert mortality disease (VCMD). Crustaceans currently known to be susceptible to VCMD include Penaeus vannamei, P. chinensis, P. japonicus, P. monodon, Macrobrachium rosenbergii, Procambarus clarkii, Exopalaemon carinicauda, Ocypode cordimanus, Diogenes edwardsii, Corophium sinense, Parathemisto gaudichaud and Tubuca arcuate. Fish species including Mugilogobius abei, Carassius auratus, and Paralichthys olivaceus may also be susceptible to the virus.

Infection with DIV1 is an emerging disease in farmed Cherax quadricarinatus and Penaeus vannamei suffering a high mortality. This disease card provides information on signs of disease at pond and animal level (levels I - III diagnoses), the disease agent, known host range and distribution in the Asia-Pacific region, molecular diagnostic methods and provides key expert contact points.

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.