Red seabream iridovirus associated with cultured Florida pompano Trachinotus carolinus mortality in Central America

Abstract

Mariculture of Florida pompano Trachinotus carolinus in Central America has increased over the last few decades and it is now a highly valued food fish. High feed costs and infectious diseases are significant impediments to the expansion of mariculture. Members of the genus Megalocytivirus (MCV), subfamily Alphairidovirinae, within the family Iridoviridae, are emerging pathogens that negatively impact Asian mariculture. A significant mortality event in Florida pompano fingerlings cultured in Central America occurred in October 2014. Affected fish presented with abdominal distension, darkening of the skin, and periocular hemorrhages. Microscopic lesions included cytomegalic 'inclusion body-bearing cells' characterized by basophilic granular cytoplasmic inclusions in multiple organs. Transmission electron microscopy revealed arrays of hexagonal virions (155-180 nm in diameter) with electron-dense cores within the cytoplasm of cytomegalic cells. Pathological findings were suggestive of an MCV infection, and the diagnosis was later confirmed by partial PCR amplification and sequencing of the viral gene encoding the myristylated membrane protein. The viral sequence revealed that the fingerlings were infected with an MCV genotype, red seabream iridovirus (RSIV), previously reported only from epizootics in Asian mariculture. This case underscores the threat RSIV poses to global mariculture, including the production of Florida pompano in Central America.

The status of Florida pompano, Trachinotus carolinus, as a commercially ready species for U.S. marine aquaculture

“…Viruses such as RSIV (L opez-Porras et al, 2018) and the aforementioned RSGNNV, which affects the culture of T. blochii in Southeast Asia (Pakingking et al, 2011;Ransangan et al, 2011), are of major concern. At the cellular level, viruses disrupt fish physiology leading to anorexia, anemia, and abnormal behavior (L opez-Porras et al, 2018;Nakai et al, 2009;Roberts, 2012). In tropical and subtropical areas of the American continent, the bacteria causing red pest (V. anguillarum) (Hawke, 1976) and fish tuberculosis (M. marinum) (Yanong et al, 2010), and the trophonts or feeding stages of the ectoparasites C. irritans (white spot disease) (Gomez, 1987) and A. ocellatum (velvet disease) (E. Williams, 1974) also affect fish health at different levels.…”

“…With respect to parasites, early detection may be achieved by Klein's silver impregnation or protargol impregnation for Trichodina spp. (Lom & Dykova, 1992), together with electron microscopy, histopathology, serological (Baxa, Kawai, & Kusuda, 1988), and molecular techniques such as amplification and sequencing of specific fragments of the pathogen's DNA/RNA (Chakroun, Grimont, Urdaci, & Bernadet, 1998;L opez-Porras et al, 2018;Oshima et al, 1998; Yanong, Pouder, & Falkinham, 2010Aronson, 1926Giavenni & Finazzi, 1980 Protozoan parasites…”

Application of Environmental DNA for Monitoring Red Sea Bream Iridovirus at a Fish Farm

“…RSIVD, caused by the RSIV and ISKNV genotypes, is listed by the World Organization for Animal Health (OIE) because it could have a significant impact on more than 30 fish species in the aquaculture industry if the virus is brought into RSIVD-free countries ( 31 , 32 ). The distribution of the virus appears to be spreading, as outbreaks of RSIVD have been documented in the United States and the Caribbean Sea ( 33 , 34 ).…”

Genetic characterization of infectious spleen and kidney necrosis virus in Banggai cardinalfish Pterapogon kauderni identified from eight separate cases between 2000 and 2017

“…All eight samples tested positive by conventional PCR using the previously described MCV‐F/R primers (Koda et al, 2018) that amplifies a 173 bp region (primers included) of the viral myristylated membrane protein (Figure S2). Amplified products were visualized, purified, sequenced, primers removed and analysed by BLASTN (https://blast.ncbi.nlm.nih.gov/) as previously described (Lopez‐Porras et al, 2018). Hereafter, MCV‐infected Banggai cardinalfish samples will be referred to as BCIV followed by the year of the mortality event (Table 1).…”