title: Age, geographic, and temporal distribution of fecal shedding of Cryptosporidium parvum oocysts in cow-calf herds.
abstract: OBJECTIVE
  To evaluate fecal shedding of Cryptosporidium parvum from California cow-calf herds with respect to age, geographic region, temporal effects, and association with watery feces.
  
  
  METHODS
  Cows and calves from 38 beef cow-calf operations.
  
  
  METHODS
  Fecal specimens were collected and examined for C parvum oocysts, using immunofluorescent microscopy. Associations between age, geographic region, month of collection, watery feces, and likelihood of shedding C parvum were evaluated.
  
  
  RESULTS
  3.9% of cattle were shedding C parvum oocysts. Prevalence of shedding among calves ranged from 0 to 13%, and was 0.6% among cattle > or = 12 months old. The odds of shedding C parvum among 2-month-old calves were 41 times greater than among cattle > 4 months old. The odds of shedding C parvum among cattle tested in May were 8.7 times greater than among cattle tested during June, July, or August. The odds of infected individuals having watery feces were 3 to 4 times greater than for noninfected individuals, but the etiologic fraction was only 8 to 9%.
  
  
  CONCLUSIONS
  Substantial fecal shedding of C parvum by cow-calf herds was limited to calves 1 to 4 months old, with low prevalence detected in older animals. Risk of contamination of watersheds with C parvum was limited to those periods when young calves were in the herd. Although the odds of having watery feces were greater for animals infected with C parvum than for noninfected animals, the low etiologic fraction suggests that most calves with watery feces were not infected with C parvum.
authors.affiliation: Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California-Davis, Tulare 93274, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Atwill
authors.forename: E
authors.initials: E
authors.lastname: Johnson
authors.forename: D J
authors.initials: DJ
authors.lastname: Klingborg
authors.forename: G M
authors.initials: GM
authors.lastname: Veserat
authors.forename: G
authors.initials: G
authors.lastname: Markegard
authors.forename: W A
authors.initials: WA
authors.lastname: Jensen
authors.forename: D W
authors.initials: DW
authors.lastname: Pratt
authors.forename: R E
authors.initials: RE
authors.lastname: Delmas
authors.forename: H A
authors.initials: HA
authors.lastname: George
authors.forename: L C
authors.initials: LC
authors.lastname: Forero
authors.forename: R L
authors.initials: RL
authors.lastname: Philips
authors.forename: S J
authors.initials: SJ
authors.lastname: Barry
authors.forename: N K
authors.initials: NK
authors.lastname: McDougald
authors.forename: R R
authors.initials: RR
authors.lastname: Gildersleeve
authors.forename: W E
authors.initials: WE
authors.lastname: Frost
mesh_terms: D000367:Age Factors; D000818:Animals; D002140:California / Q000453:epidemiology; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology*; D003457:Cryptosporidiosis / Q000453:epidemiology / Q000662:veterinary*; D016785:Cryptosporidium parvum / Q000302:isolation & purification*; D005243:Feces / Q000469:parasitology*; D005843:Geography; D010270:Parasite Egg Count; D013997:Time Factors