MILKY HEMOLYMPH DISEASE OF SPINY LOBSTER (MHD-SL) AND ITS EXPERIMENTAL INFECTION IN Panulirus homarus

Milky Hemolymph Disease of Spiny Lobster (MHD-SL) was reported as the most devastating disease in farming of spiny lobster. Outbreaks of the disease were recorded almost year round in Lombok from 2012 to 2016, and in Pegametan Bay, North Bali in 2016. It was stated that economic losses due to the outbreaks were considerably high. Therefore, this study was conducted first, to investigate milky disease occurrence in wild and farmed spiny lobster Panulirus homarus from different locations, second, to identify and to compare the causative agent of milky disease from other countries, and lastly, to perform experimental infection of milky disease in P. homarus.

Wild lobsters were captured from Banyuwangi, Lombok, and Jembrana coastal areas, while farmed lobsters were collected from net cages in Pegametan, Pangandaran, and Lombok. MHD-SL was detected by Polymerase Chain Reaction (PCR) analysis using 254F and 254R primers. Milky disease agent was identified by nucleotide sequence analysis, and a phylogenetic tree was built using MEGA6. Experimental infection study was done by several modes of infection: injection with undiluted and diluted infected hemolymph, water immersion, per os exposure, and two control groups as comparisons.

Three lobsters out of 35 samples were found to be infected with MHD-SL (Figure 1). Milky disease agent in this study was similar to milky disease agent from Vietnam. The phylogenetic tree showed strength relationship between our sample and other milky disease agent in some Crustacean from Vietnam, Tanzania, Madagascar, and Mozambique. All the experimentally affected lobsters exhibited disease symptom and pattern of mortality as naturally infected lobsters. The mortality pattern of the experimentally infected lobsters was found to be varies with the modes of infection.

In summary, milky disease was found only in the farmed lobster P. homarus, and no milky disease was detected in the wild lobsters. Milky disease agent in this study was classified as group of uncultured bacteria that cannot be cultured using various types of agar-based media. Experimental infection study indicated that milky disease could be transmitted horizontally from the diseased lobsters to the healthy lobsters by injection of undiluted and diluted affected hemolymph, by water immersion, as well as by per os exposure.