Mass mortality associated with a Sphaerospora‐like myxosporidean infestation in juvenile cobia, Rachycentron canadum (L.), marine cage cultured in Taiwan

Abstract

Cultured cobia, Rachycentron canadum, of 45±80 g exhibited anaemia and ascites, and a mottled red and grey, extremely enlarged kidney with cream-coloured patches or spherical nodules. Cumulative mortality was about 90% within 1 month. Extrasporogonic or sporogonic stages of a myxosporean appeared in the blood, glomerulus, renal tubules and renal interstitium. The renal tubules were the main target tissue of the parasite and were completely occluded by sporogonic pseudoplasmodia at various degrees of maturity. Many sporogonic stages were attached to the brush border of the epithelium of the renal tubules. Mature spores were seen in the lumen of the tubules. They were elongated or spherical with numerous refractile granules in the cytoplasm. The polar ®lament formed 3±5 coils. No bacteria or viruses were isolated from the diseased ®sh. Based on the results of microbiological, histopathological and electron microscopical examinations, the cobia disease was believed to be caused by a Sphaerospora-like myxosporean. This is the ®rst report of a myxosporean in cobia in aquaculture.

Isolation and characterization of pathogenicVibrio alginolyticusfrom sea cage cultured cobia (Rachycentron canadum(Linnaeus 1766)) in India

“…Cobia is a newly farmed fish in mariculture, only a few pathological studies have been conducted in that species (Chen et al . ). The majority of marine fishes cultured in cages are susceptible to vibriosis, with some fish species more sensitive to the infection than others.…”

Advances in hatchery and grow-out technology of cobia Rachycentron canadum (Linnaeus)

“…Concurrently, a more proactive culture strategy for cobia was adopted, aimed at combating the vulnerability of practically all life stages of cobia to bacterial diseases and parasitic infections with prophylactic treatments (Chen, Kou, Wu, Wang & Su 2001; Rajan, Lopez, Lin & Yang 2001; Lopez, Rajan, Lin, Kuo & Yang 2002; Rajan, Lin, Ho & Yang 2003; Ho, Kim, Cruz‐Lacierda & Nagasawa 2004; Liu, Lin, Chuang & Lee 2004; Lin, Chen, Chen, Chen, Chou, Chen, Su & Yang 2006).…”

Neobenedenia girellae (Monogenea) Infection of Cultured Cobia Rachycentron canadum in Taiwan

“…Net cage culture of cobia started in Taiwan in 1995 and yielded 4,186 metric tons in 2003 according to the FAO statistics. Because of its short culture history, reports on the diseases of cobia are quite limited, including viral, bacterial and parasitic infections (Chen et al, 2001;Chi et al, 2003;Lopez et al, 2002;Rajan et al, 2001). A Sphaerospora-like myxozoan in the kidney and monogenean Neobenedenia sp.…”

“…A Sphaerospora-like myxozoan in the kidney and monogenean Neobenedenia sp. on the body surface have been known as parasitic agents (Chen et al, 2001;Lopez et al, 2002). Lopez et al (2002) reported that Neobenedenia sp.…”