Hexamitiasis is a protozoal infection of turkeys, pheasants, and related species that leads to acute enteritis. Diagnosis is based on identification of the organism microscopically in intestinal scrapings. There is no effective treatment or vaccine.
Hexamitiasis, brought about by the protozoan Spironucleus meleagridis (formerly Hexamita meleagridis), is an acute, infectious, catarrhal enteritis of turkeys, pheasants, quail, chukar partridges, and peafowl. Natural infection has not been observed in chickens.
Pigeons are susceptible to infection by Spironucleus columbae.
Hexamitiasis is rare in North America. The highest mortality rate occurs in birds 1–9 weeks old.
Etiology of Hexamitiasis in Poultry
The protozoal parasite that causes hexamitiasis in turkeys, S meleagridis, is related to Giardia. It is spindle shaped, measures ~8 × 3 mcm, and has four anterior, two anterolateral, and two posterior flagella. It has not yet been cultured in experimental media; however, it has been grown in the allantoic cavity of developing chicken and turkey embryos.
S meleagridis is transmitted directly by ingestion of contaminated feces and water. Encysted hexamitids are resistant to environmental conditions outside the bird and are infective. Up to one-third of recovering birds become carriers and shed parasites in their droppings.
Clinical Findings and Lesions of Hexamitiasis in Poultry
Clinical signs of hexamitiasis are nonspecific and include the following:
watery diarrhea that may be yellowish later in the disease
dry, unkempt feathers
listlessness
rapid weight loss despite continuing to eat
Birds with hexamitiasis may die in coma or seizures. Bulbous dilatations of the small intestine (especially duodenum and upper jejunum) filled with watery contents are characteristic. The crypts of Lieberkühn contain myriad S meleagridis individuals, which attach to the epithelial cells by their posterior flagella.
Diagnosis of Hexamitiasis in Poultry
Microscopic identification of the parasite in scrapings from intestinal mucosa
Diagnosis of hexamitiasis depends on finding the flagellates by microscopic examination of scrapings of the duodenal and jejunal mucosa. Spironucleus spp move with a rapid, darting motion (in contrast to the jerky motion of trichomonads). To avoid the contamination of instruments with other cecal protozoa, the duodenum should be opened first.
Spironucleus spp may be demonstrated in poults that have been dead for several hours, if the scrapings are placed in a drop of warm (40°C [104°F]) saline solution (0.9% NaCl) on a microscope slide. The presence of a few Spironucleus individuals in birds > 10 weeks old may be unimportant in terms of hexamitiasis; however, these organisms still act as a reservoir of infection for the flock.
Prevention and Treatment of Hexamitiasis in Poultry
Restriction of flocks to a single age or single species
Decontamination of all equipment and personnel entering a facility
Thorough cleaning to prevent infection of new flocks by parasitic cysts
Because many birds are carriers of Spironucleus, breeder turkeys and young poults should be raised on separate premises if possible, preferably with separate attendants. Wire platforms should be used under feeders and waterers. Pheasants and quail may also be carriers and should not be raised in the same location as poults.
Spironucleus parasites can be transmitted indirectly, if affected fecal material is transferred to another location by contaminated equipment or clothing.
The infective form of Spironucleus is a cyst. Therefore, if a flock is positive for this parasite, the litter must be removed, and before the next flock is placed, the farm and all equipment must be disinfected with heat (45°C [113°F] for 30 minutes) or with standard cleaning products.
There is no effective treatment or vaccine for hexamitiasis. However, oxytetracycline (0.011% [110 g/tonne, or 100 g/ton], in the feed for 2 weeks) or chlortetracycline (0.022%–0.044% [220–440 g/tonne, or 200–400 g/ton], in the feed for 2 weeks) may help control secondary infections.
Key Points
Hexamitiasis is caused by the protozoan Spironucleus meleagridis.
Diagnosis is made through microscopic examination of intestinal scrapings.
Spironucleus forms infective cysts that persist in the environment, so the litter must be removed if a flock is positive.
There is no treatment for hexamitiasis.
For More Information
Beckstead R. Miscellaneous and sporadic protozoal infections. In: Swayne D, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Vol. 2. Wiley Blackwell; 2020: 1231-1254.
