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Title: A study of the level and dynamics of Eimeria populations in naturally infected, grazing beef cattle at various stages of production in the mid-Atlantic U.S.A.

Author
item LUCAS, AARON - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item SWECKER, JR., WILLIAM - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item LINDSAY, DAVID - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item SCAGLIA, GUILLERMO - Louisiana State University Agcenter
item Neel, James
item ELVINGER, FRANCOIS - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item ZAJAC, ANNE - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2014
Publication Date: 3/27/2014
Citation: Lucas, A.S., Swecker Jr., W.S., Lindsay, D.S., Scaglia, G., Neel, J.P., Elvinger, F.C., Zajac, A.M. 2014. A study of the level and dynamics of Eimeria populations in naturally infected, grazing beef cattle at various stages of production in the mid-Atlantic U.S.A. Veterinary Parasitology. 202:201-206.

Interpretive Summary: Single celled Coccidian parasites occupy the gastrointestinal tract of cattle worldwide and calves are exposed in early life in all conventional management systems. The highest prevalence of infection and incidence of disease occurs in calves less than one year of age, although older cattle continue to exhibit infection. In most natural infections, regardless of animal age, mixed species infections are common, but only two species, Eimeria. bovis and E. zuernii, have been associated with clinical disease in the U.S.A. The Appalachian region of the U.S.A comprises portions of states from southern New York to northern Mississippi, Georgia, and Alabama. Interest in forage based beef production systems has increased in recent years. For grass-based systems with continuous use of pastures, internal parasitism by coccidia could be a factor limiting production in young animals. There is little information available on the species dynamics of eimerian parasites in grazing cattle in the central Appalachian region of the United States. Therefore, the objective of this study was to describe the level of infection and species dynamics of Eimeria spp. in grazing beef cattle of various age groups over the course of a year in the central Appalachian region. Despite the predominance of pathogenic Eimeria species and high numbers of reproductive oocysts in some animals, no evidence of clinical coccidiosis was seen in this study. The observed infections were omnipresent, but dynamic over time as the animals aged and progressed through the stages of production and seasons of the year. The high prevalence of infection in the absence of clinical disease demonstrates that coccidia infection need not present a significant constraint to beef cattle production on entirely forage-based diets in this region.

Technical Abstract: There is little information available on the species dynamics of eimerian parasites in grazing cattle in the central Appalachian region of the United States. Therefore, the objective of this study was to describe the level of infection and species dynamics of Eimeria spp. in grazing beef cattle of various age groups over the course of a year in the central Appalachian region. Rectal fecal samples were collected from male and female calves (n=72) monthly from May through October 2005, heifers only (n=36) monthly from November 2005 to April 2006, and cows (n=72) in May, July, and September, 2005. Eimeria spp. oocysts were seen in 399 of 414 (96%) fecal samples collected from the calves from May through October. Fecal oocysts counts (FOC) in the calves were lower (P<0.05) in May than all other months and no significant differences were detected from June through September. Eimeria spp. oocysts were detected in 198 of 213 (92%) fecal samples collected monthly from 36 replacement heifers during November to April and monthly mean FOC did not differ during this time period. The prevalence of oocyst shedding increased to 100% in calves in September and remained near 100% in the replacement heifers during the sampling period. Eimeria spp. oocysts were also detected in 150 of 200 (75%) samples collected in May, July, and September from the cows and mean FOC did not differ significantly over the sampling period. Eimeria spp. composition was dominated by E. bovis in fecal samples collected from calves, replacement heifers and cows. Mixed Eimeria spp. infections were, however, common in all groups and 13 Eimeria spp. oocysts were identified throughout the sampling period.