Head and Lateral Line Erosion

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Also known as: HLLE — Hole-in-the-head Syndrome


This is a common chronic disease that affects marine aquarium fish, especially tangs and angelfish.

The exact aetiology of the syndrome is unknown, but proposed agents include parasites, carbon dust, heavy metals, electrical voltage, UV radiation, nutrient deficiencies in vitamin A or C. There may not be one particular inciting cause, and the syndrome may simply be a clinical response to various stressors. These may include overcrowding, poor water quality and poor nutrition.

In one study, a reovirus was isolated from a moribund angelfish with HLLE lesions.

Secondary bacterial, fungal and parasitic infections may occur.

Clinical Signs

As the name suggests, the disease involves lesions of the head that sometimes extend down the lateral line.

They are usually progressive, often symmetrical, depigmented erosions and ulcerations that coalesce to produce large crateriform lesions and pits on the head, flanks and lateral line.

Fish may feed and behave normally, even when severely affected. Some fish may become anorexic, lethargic and thin.


Diagnosis is based on the history and clinical signs.

The husbandry and environment should be evaluated for potential stressors.

Wet mount examination of the skin should be performed to identify any secondary infections.

Faecal examination may be beneficial to check for intestinal parasitism.

Histopathology may reveal: an erosive to ulcerative dermatitis with epidermal spongiosis, vesicle formation or inflammatory cell exocytosis.


Treatment of HLLE is empirical and relies on the elimination of any potential stressors. Water quality should be improved if necessary, overcrowding reduced, and a balanced and varied diet should be fed.

A grounding device can be used to remove stray voltage from the system and changing the activated carbon in the filters may also be helpful.

If this is unsuccessful, an infectious cause should be suspected and should be treated with the appropriate antibacterial or antifungal agent.

0.01% becaplermin has been successfully used to treat HLLE in marine tropical fish by applying the product to the debrided skin lesions.

Fish can recover from HLLE but often have permanent scarring. The disease is rarely fatal.

Head and Lateral Line Erosion Learning Resources
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Ornamental Fish Q&A 26


Roberts, H. (2009) Fundamentals of Ornamental Fish Health John Wiley and Sons

Noga, E. (2010) Fish Disease: diagnosis and treatment Wiley-Blackwell

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