Hole in the head lesions between the eyes in fish are caused by which disease?

• A. Enteric septicemia
• B. Enteric redmouth
• C. Ulcer disease
• D. Chilodonelliasis

Answer: (A)

Hole-in-the-head disease is caused by a protozoan parasite, most commonly Hexamita species (and related Spironucleus). The organisms invade the head region and surrounding tissues, leading to pit-like lesions between the eyes and along the skull. This condition is strongly linked to stressors such as poor water quality, nutritional deficiencies (especially vitamins and minerals), and crowded or suboptimal husbandry. Improving water quality, providing a balanced diet, and reducing stress often help fish recover, while specific anti-protozoal treatment may be used under veterinary guidance.

The other diseases listed are different types of problems: bacterial infections like enteric septicemia and enteric redmouth cause systemic illness or distinct lesions (red areas around the mouth or body); ulcer disease refers to skin ulcers that don’t specifically produce the characteristic holes between the eyes; and chilodonelliasis is caused by a different protozoan that mainly affects skin and gills, not the classic head lesions described here.