HAHELLOSIS, A NOVEL RED EGG DISEASE IN TILAPIA (Oreochromis spp.) HATCHERIES CAUSED BY THE MARINE BACTERIUM Hahella chejuensis

Saengchan Senapin^*, Ha Thanh Dong, Watcharachai Meemetta, Akasit Siriphongphaew, Walaiporn Charoensapsri, Wanida Santimanawong, Warren A. Turner, Channarong Rodkhum, Boonsirm Withyachumnarnkul, and Rapeepun Vanichviriyakit

Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Faculty of Science, Mahidol University, Rama VI Rd., Bangkok, 10400, Thailand and National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathum Thani, 12120, Thailand
saengchan@biotec.or.th

The present study first reported a novel disease called Hahellosis or "red egg disease" that has been affecting tilapia (Oreochromis spp.) hatcheries in Thailand since year 2000. The disease was characterized by a change in the color of the eggs from normal yellowish to a reddish color and eventually the eggs failed to hatch. Cumulative loss of fry production was recorded to be 10% and increased to 50% during cold weather (<24°C) in Thailand. Hahella chejuensis, a red pigmented Gram negative marine bacterium, was subsequently recovered from samples of the red egg. Experimental infection of eggs indicated that H. chejuensis was able to cause red egg disease and also reduce the hatching rate. PCR protocol was developed for detection of H. chejuensis in tilapia samples including eggs and gonad tissues of tilapia broodstocks. In situ hybridization using H. chejuensis specific probe revealed positive signals in the ovaries and testes of tilapia broodstocks, suggesting a possible vertical transmission route of the red pigmented bacteria.