Detection of Fish Disease Caused by Iridovirus on Grouper (Epinephelus sp.) and Pomfret Star (Trachinotus blochii) with Co-agglutination Method in Tanjungpinang, Indonesia

Abstract

Iridovirus infection often causes death and considerable economic losses in the aquaculture industry. This research applies the co-agglutination method that is fast, cheap and accurate in confirming the diagnosis of the cause of an outbreak of illness caused by iridovirus in the field, so that remedial action can be taken quickly and appropriately to minimize the impact of wider losses. Samples were taken from the grouper and pomfret star farms that are experiencing outbreaks of infectious diseases in the months from May to August 2015, Tanjungpinang, Indonesia. The sick and allegedly attacked by iridovirus samples showed abnormal swimming clinical symptoms, weakness and the swollen spleen. The swollen spleen of sick fish created suspension in phosphate buffered saline (PBS) with pH 7.2, and then centrifuged at 8,000 rpm for 10 min. The supernatant after centrifuge was used as the test sample. On a clean object glass, 50 µL of the supernatant was treated with 50 µL kit co-agglutination pre-prepared. The positive results were shown by the agglutination reaction after 10-15 min, while as a negative control, PBS was reacted with co-agglutination kit that looked homogeneous (no agglutination). It was showed that the grouper (Epinephelus sp.) on four farms and pomfret star (Thracinotus blochii) on one farm that experienced an outbreak of infectious disease in Tanjungpinang showed positively infected iridovirus. The same positive iridovirus result was also demonstrated by examination using polymerase chain reaction (PCR) at 570 bp. So, the causative agent of plague on grouper and pomfret star was iridovirus. In addition, the co-agglutination test based on serology is more quick, cheap and accurate.