Common Names: Hexamita
Hexamita intestinalis
Hexamita salmonis
Hexamita truttae
Hole-in-the-head disease
Lateral line erosion
Salinity: Freshwater
Description: Hexamita is actually the group name for several species of flaggellate protozoan of which three are pathogens of freshwater fish. All are capable of causing gastrointestinal problems, but the main villian, and the scourge of cichlid keepers worldwide responsible for the "hole-in-the -head" syndrome, is Hexamita intestinalis. It is not exclusive to cichlids however and other fish such as goldfish,mosquitofish, various perches and even the sturgeon family can contract the illness. Amphibians too can contract and spread this illness.

The disease is usually ingested in the inert cyst form, although open wounds and anal entry are possible for later stages of protozoan.Hexamita are fully mobile in the flagellate stage and can freely swim and travel to new hosts.Infection is quick with the protozoan beginning an impact on the host in as little as 24 hours.Interestingly some fish with low level infections may never succumb, and as long as the numbers can be kept low a fish may not die, but will probably still suffer visible lesions and reduced health.In aquaria however , rapid cystic reproduction is the norm, and most fish are constantly reinfested until the infection reaches lethal levels. Resistance to the protozoans varies species by species, Angels are often resistant whereas Discus for example, are very susceptible. Hexamita is one of the main reasons that these fish should be kept seperate unless treated beforehand, and why cichlid owners should be careful about keeping untreated specimens from different type localities together.

Symptoms include anorexia and anaemia, necrotic holes that enlarge the sensory pits on the head of most cichlids (severe cases can be shockingly disfiguring), and the lateral line erosion which is basically another sensory pit area the protozoan will cause necrosis within. Fish affected will commonly be lethargic,some species will also become hypersensitised to light and heat and may retreat to warm dark areas in aquaria, often near heaters.
Symptoms: Spots
Treatment: This is another disease where treatment protocols and the nature of the parasite are completely misunderstood.Once infected a fish will remain infected for life or until treatment is administered. The disease does NOT fade away or pass on its own, even with the finest levels of care.

What leads people to the mistaken belief that good diet and care will cure hexamita is the fact that under good examples of husbandry, where water is cleaned and the use of UV sterilisers may be commonplace, hexamita symptoms may be reduced. I stress this does not mean that the fish is in any way cured, it simply means that infection levels are kept low and that the fish is given an opportunity to heal some of the damage caused. Hexamita infections kill based on the number of parasites in the body, and the subsequent burden on the fish's metabolism. A low level will not kill, but will always remain present , available to badly sicken the fish again should its condition drop for any other reason, and the fish will remain an active and contagious breeding ground from whom other fish may be exposed to infection.

In the confined conditions like aquaria ,and especially in cichlid communities of any type, treatment must be considered the only true solution.Under any other context a fishkeeper will simply be administering what amounts to palliative care.The fishkeepr cannot know if reinfection may be achieved at any time, and certainly cannot prevent it from happening.Simply vouching for good care over proper treatment is one of the reasons that hexamita is so prevalent in the hobby, and it is a myth that should be dispelled with the utmost persistance.

Successful treatments include. Oral adminitration by feeding or tube feedings of metronidazole medicated foods or the pure suspension in carefully administered doses will cure most cases of hexamita.
There is however a certain resilience against the drug in most cases, and for those instances a different variant of metro, namely "Metronidazole D" can be procured from a vet.This is one of the few known drugs truly effective for internal symptoms of this disease, and unless you confront the internal aspect, the disease cannot be cured.

Other cures include epsom salts which may have a limited purgative effect when applied internally, and low levels of aquarium salts may help reduce the swelling and infection in the sensory pits of the fish.
Numerous wonder cures are claimed for hexamita, but since this infection is both internal and external only internal treatments will really kill the problem. Other treatments simply help clear surface infection, and subdue visible symptoms.

Hexamita will cause wounds that allow other bacterial and fungal causes to take a toll on the fish's health, and as such those problems will also have to be diagnosed and treated as they occur.
Comments: The author has seen incidences of hexamita protozoan infections having been "debunked" as the major cause for hole-in-the -head. These claims are not scientifically proven, and are in fact utter, utter, rubbish, being as they are based on anecdotal evidence rather than real research carried out under controlled conditions.The author considers such rumours to be downright dangerous,especially since huge reams of internet based and authoratitive sounding information is available. Do not be misled. Although by it is a given that by treating the fish well ,and giving it an excellent diet, and clean water , you will significantly reduce the symptoms of hexamita, this is a way to reduce symptoms to acceptable levels.

Even so, hexamita should not be the almost omnipresent threat in aquaria that it has become, it is a directly ingested and flagellate parasite that can be eliminated. That people do not take its treatment seriously enough is the major reason via fish shops and breeders with no treatments and poor that so many aquaria have hexamita distributed to them. This is an infection that will make a laughing stock of quarantine. Fish may have the complaint for years without showing symptoms,and even the cysts survive for many weeks outside of a host.

Many more fish will suffer because of ignorant,inaccurate and irresponsible treatment, especially among the cichlid species. There is no reason any aquarist should have to accept that hexamita is unavoidable, or that is a condition that has to be lived with for the entirety of a fish's life. Given sufficiently long treatment periods to prevent reinfection, and by exercising correct hygeine , this disease can be eliminated completely. This among all other diseases has been made worse by unrealistic approaches to treatment.
Image Credit: ©
Submitted By: longhairedgit
Contributors: longhairedgit
History: View changes to this profile
Edit Profile: