Streptococcosis in red hybrid tilapia (Oreochromis ...

Aquaculture Research, 2009, 40, 630^632

doi:10.1111/j.1365-2109.2008.02142.x

SHORT COMMUNICATION Streptococcosis in red hybrid tilapia (Oreochromis

niloticus) commercial farms in Malaysia Najiah Musa1, Lee Seong Wei1, Nadirah Musa1, Ruhil H Hamdan1, Lee Kok Leong2,Wendy Wee1, Mohd Nur Amal1, Basiriah M Kutty1 & Siti Zahrah Abdullah3 1

Department of Fisheries and Aquaculture, Faculty of Agrotechnology and Food Science, Universiti Malaysia Terengganu,

Terengganu, Malaysia 2

Genensis Biotechnology Sdn Bhd, Selangor, Malaysia

3

Department of Fisheries Malaysia, Fisheries Research Institute, Pulau Pinang, Malaysia

Correspondence: N Musa, Department of Fisheries and Aquaculture, Faculty of Agrotechnology and Food Science, Universiti Malaysia Terengganu, 21030 Mengabang Telipot,Terengganu, Malaysia. E-mail: [email protected]

Streptococcosis is one of the ¢sh diseases that is reported in intensive aquaculture systems and causes high economic loss to ¢sh farmers. This disease may yield high mortality rates of more than 50% over a period of 3^7 days (Yanong & FrancisFloyd 2006). Streptococcus spp. reported to cause disease in ¢sh include Streptococcus inae (Shoemaker, Evans & Klesius 2000), Streptococcus agalactiae (Suanyuk, Kanghear, Khongpradit & Supamattaya 2005) and Streptococcus di⁄cile (Berridge, Bercovier & Frelier 2001). Meanwhile, Toranzo, Magarin›os and Romalde (2005) reported ‘warm water’ streptococcosis due to Lactococcus garvieae, S. iniae, S. agalactiae and S. parauberis. The occurrence of streptococcosis outbreak increases when ¢sh are stressed due to non-optimal water temperature, low dissolved oxygen, high nitrite levels, (Bunch & Bajerano 1997; Perera, Johnson & Lewis 1997) and high culture densities (Shoemaker et al. 2000). Erythromycin, £orfenicol and amoxicillin have been commonly used for the treatment of streptococcosis (TrevesBrown 2000; Darwish & Hobbs 2005;Yanong, Curtis, Simmons, Bharattaram, Gopalakrishnan, Ketabi, Nagaraja & Derendorf 2005). In Malaysia, farmers tend to use erythromycin and oxytetracycline to treat streptococcosis in tilapia as well as a prophylactic agent in subclinically healthy ¢sh. These antibiotics are usually sprayed onto ¢sh pellets and given orally to ¢sh for approximately 7 days. To date, several vaccines have been developed against streptococcosis

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(Eldar, Horovitcz & Bercovier1997; Klesius, Shoemaker & Evans 2000). Streptococcosis is also zoonotic in nature, a¡ecting immunocompromised patients (Lau,Woo,Tse, Leung, Wong & Yuen 2003). Through rapidly expanding aquaculture in Malaysia, diseases have increased and ¢sh farms have su¡ered substantial economic losses. This paper reports the occurrence of streptococcosis in red hybrid tilapia, the main cultured freshwater ¢sh in Malaysia. To the best of our knowledge, there have been no reports on streptococcosis in cultured red hybrid tilapia in Malaysia. Hence, this study aims to isolate and identify the Streptococcocus spp. a¡ecting red hybrid tilapia in commercial farms. In September 2007, a total of 187 red hybrid tilapia Oreochromis niloticus were collected from commercial tilapia farms in four states in Malaysia namely Terengganu (40 ¢sh), Kedah (47 ¢sh), Perlis (40 ¢sh) and Selangor (60 ¢sh). The water temperatures recorded during sampling ranged from 26 to 28 1C. The farms involved have histories of high mortalities in red hybrid tilapia (15^30%). Fish with clinical signs such as darkened skin, lethargy and erratic swimming were collected and examined for spine displacement, unilateral or bilateral exophthalmia and abdominal distension. The ¢sh were euthanized with 85 ppm Tricaine Methane Sulphonate (MS-222) (Syndel, Vancouver, Canada) and dissected. Then the brain, liver, kidney, ascites £uid, skin scrapping and eye were aseptically sampled for bacterial isolation

r 2009 The Authors Journal Compilation r 2009 Blackwell Publishing Ltd


using blood agar containing 5% human blood. After inoculation, the agar plates were incubated at 28 1C for 24^48 h. A single colony was subcultured on the same medium to obtain pure isolates. Identi¢cation was carried out using conventional biochemical tests in combination with BBL Crystal Gram Positive ID Kits (BBL, Sparks, MD, USA). Physiological tests were also carried out on the isolates including a salt tolerance test (0%,1%,6% and 8%) and a temperature tolerance test (4, 28, 37 and 55 1C). A haemolysis test was conducted using pure bacterial isolates on blood agar. The isolates were analysed for susceptibility to 15 antimicrobials namely erythromycin (30 mg), amoxicillin (25 mg), spiramycin (100 mg), kanamycin (30 mg), nalidixic acid (30 mg), chloramphenicol (30 mg), ampicillin (10 mg), sulphamethoxazole (25 mg), £umequine (30 mg), fosfomycin (50 mg), lincomycin (15 mg), nitrofurantoin (50 mg), novobiocin (30 mg), oxolinic acid (30 mg) and oleandomycin (15 mg), according to the National Committee for Clinical Laboratory Standards. A total of 13 Gram-positive cocci isolates were identi¢ed as S. agalactiae. The colonies were greyish white coloured, translucent, circular, slightly convert, pin headed and b-haemolytic on blood agar. They showed positive reactions for L-valine, L-phenylalanine, 4MUa-D-glucoside, L-tryptophan, L-arginine, 4MU-phosphate, L-isoleucine, trehalose, methyl-a & b-glucoside, sucrose, maltotriose, fructose, p-n-p-b-D-glucoside, praline and leucine-p-nitroanilide, p-n-p-phosphate, ONPG and p-n-p-a-D-galactoside and arginine. They were negative for 4MU-b-D-glucoside, L-pyroglutamic acid, 4MU-N-acetyl-b-D-glucosaminide, 4MU-b-Dglucuronide, lactose, mannitol, arabinose, glycerol, p-n-p-b-D-cellobioside, p-n-p-a-D-maltoside, urea and esculin. Antibiograms showed that most of them were found to be resistant to spiramycin, oleandomycin, sulphamethoxazole, oxolinic acid, kanamycin and nalidixic acid. In terms of physiological characteristics, all isolates were similar, except that their growths were inhibited at 4 and 55 1C. They grew well on medium supplemented with 0% and 1% NaCl but failed to grow at 6% and 8% NaCl. All ¢sh sampled for the present study showed either erratic swimming, whirling, eye haemorrhage, cataract, exophthalmia, or skin haemorrhages around the anus or at the base of the ¢ns. Internally, a soft watery brain and enlarged pale liver were observed. Evans, Klesius, Glibert, Shoemaker, Al Sarawi, Landsberg, Duremdez, Al Marzouk and AlZekni (2002) reported clinical signs such as erratic swim-

Streptococcosis in tilapia N Musa et al.

ming, whirling, C-shaped body curvature, ocular opacity, periorbital and intraocular haemorrhage, purulence and exophthalmia in cultured seabream Sparus auratus (L.) and wild mullet Liza klunzingeri due to streptococcosis. In addition, skin haemorrhages were also observed especially around the mouth, snout, operculum and ¢ns. The clinical signs of streptococcosis in ¢sh seemed to be similar regardless of the streptococcosis species involved. In the present study, S. agalactiae isolates were found only in watery brain and haemorrhagic eye samples. The involvement of these two organs contributed to the abnormal behaviour (Evans et al. 2002). In addition, Shoemaker et al. (2000) suggested an oral and/or an olfactory route by waterborne S. iniae in tilapia. They also observed that horizontal transmission of S. iniae in tilapia occurred due to the high density of ¢sh in tank. In relation to this, they recommended a quick removal of dead and moribund ¢sh from the healthy population. According to Toranzo et al. (2005), di¡erent species, groups or strains of streptococci usually exhibit speci¢city for host ¢sh. More studies need to be carried out on the distribution of S. agalactiae in tilapia to allow selection of therapeutics that can act fast on the target organs, especially the brain and the eyes. Streptococcus agalactiae was reported to infect human, especially immunocompromised patients with diabetes mellitus (63%), malignancies (22%), liver cirrhosis (19%) and a history of previous surgery (12%) (Bolanos, HernaŁndez, Santana, Molina & SaŁnchez 2005). In the present study, the S. agalactiae were also observed to be resistant to spiramycin, oleandomycin, sulphamethoxazole, oxolinic acid, kanamycin and nalidixic acid, probably due to the previous overuse or misuse of these drugs to combat bacterial diseases in farms. In the present study, it is unknown whether S. agalactiae was an inhabitant of the cage culture environment or whether it was carried by the ¢sh fries from the hatchery. More studies need to be conducted in Malaysia as database for this disease is still lacking. The ¢ndings of the present study should alarm the ¢sh producers with regard to ¢sh health management in farms, as well as ¢sh processing plants and consumers in relation to the zoonotic nature of the bacterium. Acknowledgment This work was supported by Department of Fisheries and Aquaculture, Faculty of Agrotechnology and

r 2009 The Authors Journal Compilation r 2009 Blackwell Publishing Ltd, Aquaculture Research, 40, 630^632

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Streptococcosis in tilapia N Musa et al.


Food Science Universiti Malaysia Terengganu, 21030 Mengabang Telipot,Terengganu, Malaysia.

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Keywords: streptococcosis, red hybrid tilapia, commercial farms, Malaysia

r 2009 The Authors Journal Compilation r 2009 Blackwell Publishing Ltd, Aquaculture Research, 40, 630^632