How to Effectively Treat Nocardia Disease in Largemouth Bass

In recent years, the occurrence of Nocardia disease has shown an increasingly worsening trend; the size of affected fish is getting smaller and smaller, the condition is becoming more and more serious, and the mortality rate is also getting higher and higher. It is understood that Nocardia is mainly saprophytic, especially abundant in decaying chilled fresh fish, so Nocardia disease is mostly seen in aquaculture species fed with chilled fresh fish. So how do you treat Nocardia disease in largemouth bass? What are the symptoms?

I. Symptoms of Nocardia Disease

Sick fish with Nocardia swim slowly on the pond surface; affected individuals respond sluggishly, swim alone away from the group, and have reduced appetite. Some fish have white nodules on the gills. Fish infected with Nocardia show two types of manifestations on the body surface: the gill nodule type and the trunk nodule type.

① Gill nodule type: large milky-white nodules form at the base of the gill filaments, and the gills are noticeably faded.

② Trunk nodule type: ulcers occur in the subcutaneous fat tissue and muscles of the trunk, appearing externally as nodules of varying sizes and irregular shapes. White or pale yellow nodules appear on the fish body surface, usually 0.5-2.0 cm in diameter.Another main symptom is that the liver often has white or pale yellow nodules, 0.1-0.3 cm in diameter, with liver damage, bleeding, and the gallbladder becomingdiscolored and atrophied. Nodules can also be observed in the spleen and kidney of some fish. Because there are nodules inside the body, be careful to distinguish this from visceral sporozoa.

II. How to Treat Nocardia Disease in Largemouth Bass

Because this disease is caused by infection with Gram-positive bacteria, commonly used oral aquatic medicines have poor therapeutic effects on it.

① Oral medicine: For 40 kg of feed, use: 1 bottle of “Florfenicol” or 1 packet of “Duowei Nikao” + 1 packet of “Like 101” + 1 packet of “Zhixue Kuai” + 1 packet of “Vitamin C Sodium” + synergist; it must be fed simultaneously for more than 5 days, once a day is sufficient.

② External disinfection: “Junxiao” or “Povidone Iodine” or “Jundu Shaxing” or “Quansha 2008” or “BAIDUQING” or “Youdian” and others are all acceptable; splash it externally for disinfection at the dosage stated in the instructions on the 3rd day of feeding the oral medicine.