Hexamitiosis is a disease caused by the flagellated protozoan Hexamita that infects freshwater fish. It commonly causes hole-in-the-head disease in salmonids, cyprinids, and ornamental fish. Hexamita is an opportunistic pathogen that typically infects fish when they are stressed or weakened. Clinical signs of infection include anorexia, emaciation, lesions on the skin or fins, and inflammation of internal organs. The parasite is transmitted orally or anally and spreads through water. Proper fish husbandry practices and treatments with drugs like dimetridazole, metronidazole, or furazolidone can help control hex

1. Presented by: Harapriya
Department of aquatic animal health manangement
Date1-11-2017

2.  Hexamitiosis is the one of the most important
disease caused by excessive parasitism of
flagellated protozoa called Hexamita(Spironucleus)
 Fresh water hole-in-the-head syndrome or fresh
waster head and lateral line erosion (FHLLE)
generally occurred in salmonid group of fishes ,
cyprinids and ornamental fishes.
 It is an opportunistic pathogen and attacks the fish
when it is weak rarely found in wild habitat more
in farmed fish

4. 1. Hexamitiosis was transmitted by oral route.
2. The parasites may be transmitted by water to healthy farm.
3. Anal route plays role in transmission of the disease in the case of free swimming
flagellated forms of the parasites.
4. Parasites found in the intestinal tract & under stress, the reproduction of
parasites increase and lead to disease.
5. Lesions on skin (especially the head), or at the base of the fins and near
the lateral line act as route of infection especially in tropical aquarium fishes

5.  1. Malnutrition (especially vitamin B deficiency).
 2. Over crowding , improper handling and shipping.
 3. Physiological disturbance of healthy fish for any reasons
.

6.  . Clinical signs of the disease in natural
infections include anorexia, emaciation,
weight loss, weakness, whirling, listlessness,
abdominal distension, anaemia, faecal
pseudocasts, pale stringy faeces, a red vent,
exophthalmia and dark coloration Fish
 In angel fish and cichlids they are found to be
pitting in the head.

7.  Infected aquarium tropical fish may have yellow mucus in their intestines,
enteritis and enlarged and inflamed gall bladder. In systemic infections, the
stomach of fish may be perforated, with chronic inflammations in internal organs,
atrophy of renal tubules and necrosis of the kidney.
 Fish with hole-in-the-head disease have small hole-like lesions on the body surface
which produce yellow, cheesy strings of mucus. In some fish (e.g. angelfish), these
lesions may be confined to the head region, occasionally extending posteriorly
along the lateral line. Gross pathologies include haemorrhaging in internal
organs, splenomegaly, nodules in the liver deformed (globulated) spleen and
granulomatous lesions in the spleen.
 Systemic infection may occurred lead to swollen of liver with petechial
haemorrhages, ascites with blood clots in the visceral cavity. Also enlarged kidney
& gall bladder reported in infected fishes.

8. Hole in the head by Hexamita sp
Hexamita ( spironucleus )Infection at head
Enlargement of kidney,
spleen, gall bladder

9.  : Trophozoites are commonly found in the lumen of the intestine, while cysts are
often not seen. Trophozoites of H. salmonis are usually in the upper intestine and
pyloric region, and they are also sometimes in the gall bladder and rectum .In
heavy infections they may occur throughout the intestinal tract trophozoites and
in the blood, gallbladder ,heart ,kidney, liver ,spleen, eye, brain, muscles,
mesentery and abdominal cavity. There are also reports of hexamitids in cranial
skeletal tissues and in pustules on the skin of infected cichlids.
 pathogenic hexamitids secrete a histolytic enzyme(s) which is an important
contributing factor to the development of clinical symptoms in systemic
infection(e.g. anaemia, lesions) and fish mortality.
 The secreted protease will allow the hexamitid to cause the anaemia, and will
produce lesions in internal organs and large ulcers on the body surface (of infected
fish

10. Hexamita (Spironucleus) [Zoomastigophorea, Diplomonadida] is 7–12 × 4–9 μm,
pear shaped or round, flagellate with 3 pairs of anterior flagellae and one pair of
posteriorly pointed flagellae. The taxonomic relationships (at the generic and
species levels) between parasites found in different hosts ar
 Members of the order Diplomonadida have a double set of organelles and bilateral
symmetry and those that are known to cause disease in vertebrates include
Hexamita, Spironucleus, Octomitus and Giardia. There are three species of the
genus Hexamita have been described as pathogenic
 protozoa to fishes. H. salmonis , H. truttae and H. intestinalis
 Hexamita can live in rich organic waters or as intestinal parasites, while the
remaining three genera are all parasitic.
 Hexamita has an elongated to spherical body and spherical nuclei, while a
pyriform body and elongated nuclei are characteristic of Spironucleus

12. Hexamita spp Hexamita spp

13.  :Live trophozoites of Hexamita and Spironucleus vary from elongated to nearly
spherical and the two genera are usually difficult to separate. The pyriform
trophozoites become more spherical before they divide. The lengths of live
organisms may reach 20 µm and the organisms have bilateral symmetry. Each
side has a nucleus and four flagella and this is the karyomastigont. Reproduce by
binary fission.
 Trophozoites of hexamitids are usually found extracellularly in the lumen of the
intestine, in internal organs or in lesions on the body surface. The parasite is in
host cells in capillaries and sinusoids of the liver, spleen and head kidneys.
Infection is generally believed to occur via the ingestion of cysts or trophozoites;
however, the rectal route of infection.
 In intestinal infections, cysts and trophozoites are normally voided with the faeces

15.  Hexamita salmonis has been reported in fishes in North America, Europe and
Asia. Hexamitids are presumed to have a very wide host range and geographical
distribution.
 These parasites cause disease in wild, farmed and aquarium fishes in cold,
temperate and warm waters. They have been reported in Acipenseridae,
Anguillidae, Cyprinidae, Cyprinodontidae, Gadidae, Gasterosteidae, Mugilidae,
Percidae, Salmonidae, Siganidae and Sparidae.
 H. salmonis or Spironucleus salmonis has been found in salmonids H. truttae has
been reported universal species of trout and ornamental fishes.
 H. intestinalis infested many species of fish & other aquatic animals. Young fish
are more susceptible to disease.

16.  Dimetridazole and metronidazole may be added to the feed and they are less
commonly delivered as bath treatments .
 An antibacterial treatment (furazolidone), usually added to the feed, has been
used successfully to control hexamitids in the intestine and reduce fish mortality .
 The nitroimidazoles (metronidazole 5mg/li for 3 hour , benzidazole, ronidazole
and secnidazole) completely eliminate intestinal H. salmonis infections in rainbow
trout, and some non-nitroimidazoles (albendazole, aminosidine,
diethylcarbamazine and nitroscanate) are just as effective.
 Magnesium sulfate 0.2-0.3% in feed for 3 days proven effective.
 Carbasone 0.2% for 3 days in feed effective kill the parasite.
 Good management of fish farm and disinfet the bottom soil using lime.

17. Thank you…..