Prevention and Treatment of Pustule Disease in Abalone Farming

[Causes and epidemic situation] The disease is caused by Vibrio fluvialis infection, mainly infecting juvenile and young abalone of 3-5 cm. It occurs frequently during the continuous high-temperature season in summer, lasts for a long time, and has a high mortality rate, causing extremely serious economic losses.

[Clinical symptoms] Abalone affected by pustule disease show multiple slightly raised white pustules on the foot muscle, which generally remain unruptured for a period of time. When high temperatures persist in summer, the condition worsens and the course of the disease shortens, with the pustules rupturing within a relatively short time. The ruptured pustules discharge a large amount of white pus and leave deep holes ranging from 2-5 mm, causing varying degrees of ulceration on the foot muscle surface. Microscopic examination reveals rod-shaped bacteria moving in the pus. At this stage, the abalone's attachment ability decreases and appetite declines, until it falls off the corrugated plate into the water and dies of starvation.

[Prevention and treatment measures] Preventive measures: (1) Both juvenile and adult abalone can be infected with pustule disease, and especially after adult abalone are infected, the symptoms are visible to the naked eye. To prevent pathogenic bacteria from contaminating the water body and infecting healthy abalone, sick abalone should be kept separate from healthy abalone. (2) Pustule disease in juvenile abalone is not easily detected and has a high mortality rate. Therefore, healthy and disease-free parent abalone must be strictly selected for breeding. This avoids parent abalone carrying pathogenic bacteria, thereby reducing the chance of infection in abalone seedlings. (3) The growth temperature range of the pathogen causing pustule disease is 15-42°C, with the growth rate approaching its highest level at 30°C, and between 15-30°C, the growth rate nearly doubles for every 5°C increase in temperature. Accordingly, while ensuring the growth rate of abalone, appropriately maintaining a low-temperature environment, especially adopting this measure during the hot midsummer season, can control the massive reproduction of the pathogen to a certain extent. (4) To prevent outbreaks of pustule disease during the high-temperature season, drugs can be used preventively in a planned and reasonable manner just before the high-temperature season arrives. The specific method can be as follows: add 3.12 g of compound sulfamethoxazole per cubic meter of water, bathe for 3 hours, once a day for 3 consecutive days as one cycle, then wait 3-5 days before starting the next cycle.

Treatment method: During outbreaks of pustule disease, 6.25 g of compound sulfamethoxazole per cubic meter of water can be used to bathe the affected abalone. Generally, a bath of 3 hours per day for 3 consecutive days can be used as one course of treatment, then stop the drug for 3-5 days before starting the next course. When the condition is severe and the mortality rate remains high, each course can last 5 days. Bathe once a day for 3 hours each time. Alternatively, 1.56 g/cubic meter of compound sulfamethoxazole combined with 6.25 g/cubic meter of norfloxacin can be used for bathing, with the same method as above.