Transmission routes and treatment of brown ring disease affecting manila clams (Tapes philippinarum)

The potential transmission routes of Vibrio tapetis, the causative agent of the brown ring disease affecting manila clams, Tapes philippinarum, have b een studied under laboratory conditions. The results obtained indicate that the most probable transmission route is by means of direct contact with in fected clams. The main factors affecting the incidence of brown ring diseas e in cultured manila clams were evaluated in normal aquaculture conditions. No significant differences were obtained in regard to clam seed density, b ut the type of substrate in clam beds significantly affected the disease. C hemotherapeutic treatment of infected clams is proposed, on the basis on th e antimicrobial susceptibility of V. tapetis, antibiotic solubility in seaw ater, differential clam toxicity and cost, as being the most adequate treat ment the contact of the clams for 1 to 2 h previously to their seeding with nitrofurantoin (10 mg/L seawater for 3 days), flumequine (1.5 mg/L seawate r for 3 days), or oxolinic acid (1 mg/L seawater, only one bath treatment).