An Experimental Trial of Oxytetracycline as a Therapy for Black Spermatophore Disease in Penaeus vannamei

Abstract The efficacy of oxytetracycline was assessed as a potential therapy for male reproductive tract syndrome in a population of 160 previously affected, pond-reared, adult Penaeus vannamei. All animals were individually tagged, and the severity of disease was assessed grossly 2 weeks before, during, and 4 weeks after feed medicated with oxytetracycline hydrochloride was administered. Bacterial cultures indicated that more Vibrio sp. were isolated from animals with melanized spermatophores than from animals with normal spermatophores at the same site. Vibrio alginolyticus was the most common bacterial isolate, and the bacterial isolates were sensitive to oxytetracycline. A t-test analysis of the mean lesion severity scores showed no significant difference between the control animals and animals that received the medicated feed. A significant difference in severity scores among designated severity groups (low, medium, high; P < 0.01) was maintained throughout the experiment. Overall, the trend in all s...