Experimental transmission of white spot syndrome virus (WSSV) from black tiger shrimp Penaeus monodon to the sand crab Portunus pelagicus, mud crab Scylla serrata and krill Acetes sp.

Abstract

Whlte spot syndrome virus (WSSV) is the cause of a widespread epizoot~c in cultured shrimp in Thailand and many other countries in Asia. A number of crustacean and other arthropod species have been proposed as reservoirs for the virus by feeding trials and PCR assays. Ho~vever, detailed histological studies are needed to confirm that suspected carriers have active viral infections. This study was carried out to determine whether 3 common crustacean residents of shrimp culture ponds (the sand crab Portunus pelagicus, the mud crab Scylla serrata, and krill Acetes sp.) could be experimentally infected with WSSV and, if so, what the effect of these infections would be. For krill, 3 routes of infection were tested (injection, ingestion and immersion) while for the crab species, only injection and ingestion were tested. WSSV preparations were made from naturally and experimentally infected Penaeus monodon as viral extracts from tissue homogenates (for injection and immersion) and as cut tissues (for ingestion). As determined by normal histology, electron microscopy and in situ DNA hybridization, all of the test species could be infected with M' SSV. For krill, injection was the most effective route (100% mortality in 3 d), followed by immersion (100% mortality in 5 d ) and ingestion (20% mortality in 9 d). For the crabs, injection was also the most effective route of infection. However, infection dld not necessarily lead to mortality. Mortality for injected sand crabs was 100% in 8 d but for mud crabs only 20% in 9 d . By ingestion exposure, there was no mortality for either species over the 9 d experimental period, even though infection was confirmed by histological examination. Based on the results of this study, the crab species and krill can be considered as viral reservoirs, since they are able to carry the infection and may persist for significant periods in the shrimp farming environment.

Experimental infection of white spot syndrome virus in freshwater crayfish Pacifastacus leniusculus

“…This latter possibility may be less likely now that WSSV is known to be only distantly related to the baculoviruses (Tsai et al 2000, Liu et al 2001, contrary to the conjecture in earlier publications that it is closely related (e.g., Wongteerasupaya et al 1995). In any case, further studies are necessary to determine the susceptible level to WSSV among haemocyte types, even though haemocytes have been reported to be targets of WSSV in penaeid shrimp (Durand et al 1996, Y. G. Wang et al 1999, C. H. Wang et al 2000 and crabs (Kanchanaphum et al 1998). …”

“…The virus can be detected by the use of polymerase chain reaction (PCR), in situ hybridisation or monoclonal antibody assays (Kanchanaphum et al 1998, Peng et al 1998, Poulos et al 2001. Thus, in recent years molecular probes have been developed as diagnostic tools and these are already being used for pathogen detection in commercial shrimp farms.…”

“…), palaemonidian pest shrimp, krill (Acetes sp. ), planktonic copepods and pupae of an ephydridian insect , Kanchanaphum et al 1998, Peng et al 1998, Supamattaya et al 1998, Y. C. Wang et al 1998, Q. Wang et al 2000.…”

Standardized white spot syndrome virus (WSSV) inoculation procedures for intramuscular or oral routes

“…In the sergestoid shrimp Acetes sp., individuals inoculated by i.m. route had 100% mortality by the 3rd day post inoculation (Supamattaya et al 1998). In contrast, mortality due to WSSV infection was reduced 5-fold when shrimp were inoculated with infected tissues per os, and shrimp mortality occurred over a period of 9 d post feeding.…”

Mud Crab Scylla Serrata (Forskal) as Carrier of White Spot Syndrome Virus (Wssv) in Coringa Mangroves, Andhra Pradesh.

“…After the WSSV outbreaks in India during late 1994, in the shrimp culture ponds, several instances of White spots on the exoskeleton of mud crab, S. serrata have been observed. Mud crab has been shown to be a carrier of WSSV in Taiwan and Thailand , Supamattaya et al, 1998. Otta et al (1999) have tested one mud crab with external symptoms and 20 healthy samples without white spots and reported that the one with external symptoms is positive in the 1 st step PCR whereas 3 out of 20 healthy specimens are positive in the 2 nd step PCR indicating that S. serrata is also a carrier of WSSV.…”