Hole in the Head Disease in Fish

What is hole in the head disease

Hole in the head, also known as head and lateral line erosion (HLLE), lateral line disease, and lateral line erosion, is a common disease occurring in both freshwater and saltwater fishes ^{[1, 3]}.

What does the hole in the head disease look like

It gives the appearance of a lesion or wound around the head and lateral lines that may initially be small, getting bigger as the disease progresses ^{[1, 2, 3]}.

Which fishes are more likely to get it

Freshwater fishes

• Oscar
• Koi carp
• Goldfish
• Betta fish
• Rainbow fish
• Discus
• Arowana
• Clownfish
• Piranha
• Blood parrot cichlid
• Flowerhorn cichlid
• Dwarf gourami
• Blue ram cichlid

Saltwater fishes

• Surgeonfish or Tang fish ( blue and yellow)
• Angelfish
• Parrotfish

Symptoms of hole in the head disease

Being a progressive disease, the symptoms differ according to the severity of the condition. Besides the small lesions that appear on the head and lateral lines, the following symptoms occur as the disease progresses ^{[3, 11]}.

• The lesions getting bigger and hollow, also spreading to the mouth, gills and the region around the eyes ^{[3, 11]}.
• Erosion of the lateral line ^[10].
• Lessened appetite along with a hollowed appearance of the abdominal area and stomach ^{[10, 11]}.
• Stringy mucus coming out of the wounds, often mistaken for worms ^[10].

The sensory pits of the Oscar fish are often mistaken for a hole in the head, but there should not be much confusion as they are small pin-pricked holes, while the latter results in pitting-type lesions ^{[3, 11]}.

What causes hole in the head disease in fish

Though no definite reason has been detected, there are certain factors that may be responsible for this condition ^[3].

Harmful parasites

Some issues like stress affect the immune system of the fish, leading to an increased numbers of certain protozoa like Spironucleus vorten, and those in the Hexamita genus. They affect the intestines first, gradually spreading to the abdominal cavity, gall bladder, kidney, and spleen, resulting in the formation of lesions ^{[3, 4, 6]}.

Presence of activated carbon in the aquarium

Most people prefer activated carbons for the filtration of their aquariums. A study conducted on aquarium fishes at the Toledo Zoo deduced that the dust produced by activated carbons might be responsible for triggering hole in the head in freshwater or marine fishes ^{[8, 9]}.

Mineral or vitamin imbalance

A diet lacking in adequate amounts of vitamins and minerals is also one of the key factors in triggering the disease since they make the immune system weaker, paving the way for the Hexamita parasites to infect their intestines ^[10].

Environmental conditions

Unhygienic water conditions, high levels of ammonia and nitrate in the aquarium water, overcrowded living space, as well as stray voltage, occurring because of an electricity leakage in the aquarium, are also responsible for causing the hole in the head disease ^[7,18].

Is hole in the head contagious

Hole in the head mostly occurs because of improper living conditions or when the dietary requirements of respective fishes are not adequately met. Hence, the disease does not usually spread from one fish to another. But the affected ones are still moved to a separate tank to keep the other inhabitants from getting stressed.

Is it painful

A hole in the middle of the head might look painful, but as research shows that fishes are not sensitive to pain like humans are, it might not hurt them to that extent ^[5].

How to treat hole in the head disease in Oscar, angelfish, cichlid, discus, and other fishes

In its mild form, correcting the living environment of the fish would bring in an improvement in its condition. Like in any other fish disease, move the sick fish to a quarantine tank and bring it back to its group only after recovery.

Home treatment for hole in the head disease

• Carefully monitor the water conditions by checking its ammonia and nitrate content using a liquid test kit, as well as changing it when the quality deteriorates. Also, avoid temperature fluctuation while doing so as it might even stress the fish further ^[10,11].
• Feed your sick fish with food rich in vitamin and minerals so it can recuperate at a faster rate ^[11]. The food type varies from one fish to the other. While cichlids can be given vegetables like broccoli, carrot or peas, Oscars are mostly carnivores preferring earthworms, shrimps, mealworms, mussels and prawns ^{[3, 10]}.

If the stray voltage in your aquarium is responsible for causing the condition, check the faulty equipment at once, and even install a grounding probe to reduce the instance of aquarium shock  ^{[3, 12]}.

Medicines for treating hole in the head disease

If your fish does not get any better after the above treatments, you might need to see a vet, who will prescribe certain medications.

The antibiotic metronidazole is considered useful in treating protozoan infections caused by Hexamita ^[3]. Add approximately one-quarter of a teaspoon for 75 liters of water. Do the treatment once every 24-hour, changing about 25% of the water.

You can alternately add two teaspoons of the medicine to one pound of the fish’s frozen food (after thawing). Mix the contents well, and store it back in the refrigerator. Give this mixture to the sick fish for ten days in a row ^[4] to see some positive changes.

Can you cure hole in the head disease

^{Following the home treatment measures from the onset of the disease, may help in curing the fish fast [10]}. However, if the lesions spread too much and infected the fish severely, it can even result in its death ^[3].

How to prevent hole in the head disease in fishes

providing a healthy and hygienic environment, by changing the aquarium water whenever it gets soiled, maintaining a stable temperature and providing your fish with a nutritious diet would help to minimize the chances of this disease.

Interestingly, a research conducted by the Institute of Vertebrate Paleontology and Paleoanthropology in China, suggested that the hole in head disease used to occur in humans during the ancient times. It was, in fact, a hereditary condition where a large hole naturally formed at the back of the skull ^[17].