Hexamitiasis is an acute, catarrhal enteritis of turkeys, pheasants, quail, chukar partridges, and peafowl. The highest mortality occurs in birds 1-9 wk old. Natural infection has not been observed in chickens. Pigeons are susceptible to another species of Hexamita (H columbae) . Hexamitiasis is rare in North America.
The causative protozoan parasite in turkeys, Hexamita meleagridis , is spindle-shaped, averages 8 × 3 µm, and has 6 anterior and 2 posterior flagella. It has not yet been cultured in experimental media, although it has been grown in the allantoic cavity of developing chicken and turkey embryos. It is transmitted directly by ingestion of contaminated feces. Encysted hexamitids may be more important in transmission than free flagellates. Many survivors become carriers and shed parasites in their droppings.
Clinical Findings and Lesions.
The nonspecific signs include watery diarrhea, dry unkempt feathers, listlessness, and rapid weight loss despite the fact that the birds continue to eat. Birds may die in convulsions. Bulbous dilatations of the small intestine (especially duodenum and upper jejunum) filled with watery contents are characteristic. The crypts of Lieberkühn contain myriad H meleagridis , which attach to the epithelial cells by their posterior flagella.
Diagnosis depends on finding the flagellates by microscopic examination of scrapings of the duodenal and jejunal mucosa. Hexamita spp move with a rapid, darting motion (in contrast to the jerky motion of trichomonads). To avoid contamination of instruments with other cecal protozoa, the duodenum should be opened first. Hexamita spp may be demonstrated in poults that have been dead for several hours if the scrapings are placed in a drop of warm (104°F [40°C]), isotonic saline solution on the slide. Presence of a few Hexamita in birds >10 wk old may be unimportant.
Prevention and Treatment:
Because many birds remain carriers, breeder turkeys and 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.
There is no effective treatment for hexamitiasis, although oxytetracycline (0.22% in the feed for 2 wk) or chlortetracycline (0.022-0.044% in the feed for 2 wk) may be of some benefit.