Causative agents: Emiria auburnesis, Eimeria bovis, Eimeria brasiliensis, Emiria canadensis, Emiria ellipsoidalis, Eimeria zurni
Although these 6 species of Eimeria have been isolated from the feces of bison, no associated disease has been reported. In cattle, coccidia species cause bloody diarrhea in calves. The disease is associated with overcrowding, fecal build up in pens, fecal contamination of water sources, weaning, transport and mixing of calves, and cold weather conditions. Coccidia oocysts will survive well in a wet environment. Dry, sunny conditions will dramatically reduce the survival of coccidia oocysts in the environment . The occurrence of disease is associated with the build up of coccidia oocysts in the environment and the consumption of large numbers of oocysts by calves (9).
(45,46).
Clinical signs:
There has been no clinical signs of disease reported in bison. In fecal examinations of bison and cattle that were free ranging on the same pasture in Utah, coccidia oocysts were identified in cattle feces, but not in bison feces. Bison ranged further from water sources and spent less time congregated around water sources than cattle. It is suggested that these behavioral characteristics were at least part of the reason why coccidia oocysts were not isolated in the feces of the bison (47).
In other studies, fecal samples obtained from bison maintained in confined or ranch conditions contained coccidia oocysts (45,46). Although clinical coccidiosis has not been reported in bison, it is possible that poor management conditions may precipitate the occurrence of disease. These conditions might include overcrowding of bison calves resulting in the build up of coccidia oocysts in the environment, wet conditions that allow the survival of oocysts, poor pen design allowing fecal contamination of feed and water, stress associated with weaning, and severe environmental conditions.
Diagnosis:
Coccidia oocysts may be easily identified by examining fecal samples from bison. It is important to note that the presence of coccidia oocysts in the feces of bison may not be an indication that coccidia is the cause of disease. Bison calves must have diarrhea that contains at least 5000 coccidia oocysts per gram of feces.
Treatment:
Medications for treating coccidiosis in cattle include: sulfamethazine, nitrofuazone and amprolium (9). None of these chemotherapeutic agents have been licenced for use in bison.
Control:
Preventative programs for bison should be centered on the management of weaned bison calves to avoid conditions that may predispose bison calves to coccidosis. These should include :
- Confine cows with calves at foot in pens prior to weaning. Then return the calves to the same pens after weaning. This will ensure that the calves are familiar with the pens and know where feed and water is located.
- Separate cows from calves with a secure fence that allows the cows and calves to have visual and muzzle to muzzle contact.
- Delay weaning until mid winter. This will allow the calves to become acclimatized to the weather. At this time the calves will be older and have a larger body mass, which should make them better able to withstand the stress of weaning when it is associated with cold weather.
- Weaned bison calves should have lots of space, to prevent fecal build up in the pens.
- Feed bunks and water sources should be well separated to prevent fecal build up around them.
- Remove feces when it builds up around water sources. If possible feed bunks should be moved when feces builds up around them, or the feces should be removed.
- Ensure that there is adequate feed bunk space for all the calves. Monitor the feeding behavior of calves closely. Weaned bison calves will quickly develop dominance relationships. If there is not enough feed bunk space, non-dominant calves will be forced to wait for an opportunity to feed. If the feed bunk space is severely restricted, non-dominant calves may not be allowed to access feed at all. This will be especially true for grain or supplements which are provided in small quantities that are only available to the calves for short periods of time.
- Don’t transport or mix calves until one to two months after weaning.
- In cattle, monensin and lasalocid have been fed to calves in feedlots to prevent the development of clinical coccidiosis, and to cows during the winter to reduce the shedding of coccidia oocysts onto winter feeding or bedding grounds. Although these products have been used in bison their efficacy and safety have not been established (19).