Nodaviruses in Wild Fish Population Collected Around Aquaculture Cage Sites from Coastal Areas of Tunisia

Abstract

This report describes the viral epidemiology of wild fish adjacent to cage farms within the Tunisian coasts and is focused on viral nervous necrosis virus (VNNV). A total of 92 apparently healthy wild marine fish were collected near aquaculture facilities in five different coastal areas of Tunisia. The brains and eyes of fish were examined by quantitative real time reverse transcriptase-polymerase chain reaction (qRT-PCR) to detect the nodavirus coat protein gene of. A total of 57 out of 92 (61.9%) samples were positive for nodavirus by qRT-PCR. This finding indicates that carrier fish occur at a considerable level in populations of wild marine fish. Samples from 13 fish species were found to be positive to the virus genome: Sarpa salpa, Trachurs trachurus, Boobs boops, Sardinella aurita, Diplodus vulgaris, Diplodus puntazzo Liza aurata, Diplodue sargus, Sparus aurata, Sardina pilchardus, Spicara maena, Spondyliosoma cantharus, and Diplodus annularis. The partial sequences of the RNA2 coat protein gene of these strains were identical with RGNNV type previously identified within farmed sea bass and sea bream species in Tunisia, with a homology >97%. With respect to the proximity of the sampling sites to the coast and to rearing facilities, results analysis can suggest that these viruses may be indigenous to Tunisian coastal waters.

Betanodavirus and VER Disease: A 30-year Research Review

“…In recent The RGNNV genotype, which affects tropical and temperate fish species, is the most widely distributed ( Figure 2) and has the highest number of susceptible species (Tables 1, 2 and 4). In recent years, surveys conducted in different geographical areas have shown that RGNNV is widely distributed Pathogens 2020, 9, 106 6 of 46 not only in farmed but also among wild fish in the Mediterranean basin and along the coasts of Asia and Australia [46,[62][63][64][65][66][67][68][69][70][71][72]. It has also been isolated from farmed white seabass (Atractoscion nobilis) in California [73].…”

“…It is well documented that changes experienced by ecosystems will affect the epidemiology of infectious diseases in animals, in the wild and under intensive farming conditions, including aquaculture [152][153][154][155][156]. The high number of wild asymptomatic species infected with NNV, mainly in Asian and Mediterranean countries [62,64,[66][67][68]71,80,82] and the quick rise in the viral load and subsequent outbreak of mortalities observed in experimentally infected sole when water temperature increased from 16 to 22 • C [148], suggest that VER outbreaks could have dramatic effects on natural populations, as has already been reported for some endangered fish species in the Mediterranean [72,96,109]. On the other hand, it could be argued that ocean warming could decrease the pathologies associated with the BFNNV genotype.…”

“…Furthermore, the RGNNV genotype, as described above, has been isolated from asymptomatic farmed fish which have suffered clinical infection caused by a different genotype, i.e., turbot [132] and gilthead sea bream [63]. The RGNNV genotype has also been detected by PCR in other reared fish species in Asian countries which have not suffered VER outbreaks to date [65][66][67][68][69] (Table 2).…”

“…Mortalities associated to NNV have been recorded in wild grouper (E. costae and E. marginatus) inhabiting European and African Mediterranean waters [72,96,106,109], in European sea bass also in the Mediterranean basin [96], in mullet (Liza aurata and L. saliens) in the Caspian sea [82] and in milky fish (Chanos chanos) in the Indian ocean [80]. In addition, different surveys, mainly in Asian and European waters, have reported the detection of NNV in a wide variety of asymptomatic fish belonging to more than 120 different species, 54 families and 19 orders [50,58,[62][63][64][65][66][67][68][69]126,130,139,140] (Table 4). Around 90% of these detections have been genotyped and 86% have been clustered with the RGNNV genotype.…”

APLIKASI VAKSIN BIVALEN (VNN dan GSDIV) PADA PEMELIHARAAN LARVA Ikan Kerapu Sunu, Plectropomus leopardus

“…Pemutusan siklus hidup dari virus ini di perairan sudah tidak memungkinkan lagi untuk dilakukan. Beberapa ikan liar, plankton, dan krustasea kecil disinyalir dapat menjadi inang perantara bagi virus ini di samping faktor cuaca, lingkungan, dan stres yang membuat kondisi ikan lemah atau rentan terhadap infeksi penyakit (Cherif & Fatma, 2017;Yahunar et al, 2016).…”