Motile Aeromonas Septicemia (MAS), caused by Aeromonas hydrophila, is the most widespread bacterial disease in Nigerian catfish farming. It kills rapidly and is frequently misdiagnosed as a water quality problem until ulcers appear.
Aeromonas hydrophila is a gram-negative bacterium found naturally in all freshwater environments in Nigeria. In healthy fish with good immunity, it causes no harm. However, when fish are stressed by poor water quality, overcrowding, poor nutrition, or temperature shock, A. hydrophila becomes pathogenic — invading the bloodstream and causing systemic disease.
The disease is called Motile Aeromonas Septicemia (MAS) or colloquially "ulcer disease" in Nigerian fish farming circles.
Replace 40–50% of pond water immediately. Aeromonas thrives in organically polluted water. Without water quality improvement, antibiotic treatment will fail. Increase aeration to maximum.
Apply iodine-free salt at 3g/L immediately while sourcing antibiotics. Salt reduces osmotic stress, slows bacterial proliferation, and buys 24–48 hours.
Mix Oxytetracycline powder into feed at 50–75mg per kilogram of fish body weight. Feed medicated feed for 5–7 days. If fish are not eating, use Oxytetracycline as a pond bath at 10–20mg/L for 24 hours with aeration running.
Apply KMnO₄ at 2mg/L as a pond treatment on Day 2 to kill free-living bacteria in the water column. Do not combine with salt treatment — apply 24 hours apart.
Remove dead fish twice daily. Bury them deep or burn — do not throw in open drains as this spreads infection to neighbouring ponds and water sources.
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