title: Oriental theileriosis in dairy cows causes a significant milk production loss.
abstract: BACKGROUND
  Oriental theileriosis is a tick-borne, protozoan disease of cattle caused by members of the Theileria orientalis-complex. Recent outbreaks of this disease in eastern Australia have caused major concerns to the dairy and beef farming communities, but there are no published studies of the economic impact of this disease. On a farm in Victoria, Australia, we assessed whether oriental theileriosis has an impact on milk production and reproductive performance in dairy cows.
  
  
  METHODS
  Blood samples collected from all 662 cows on the farm were tested using an established molecular test. For individual cows, milk production and reproductive performance data were collected. A clinical assessment of individual cows was performed. Based on clinical findings and molecular test results, the following groups of cows were classified: group 1, with cardinal clinical signs of oriental theileriosis and molecular test-positive for T. orientalis; group 2, with mild or suspected signs of theileriosis and test-positive; group 3, with no clinical signs and test-positive; and group 4, with no clinical signs and test-negative. Milk production and reproductive performance data for groups 1, 2 and 3 were each compared with those for group 4 using linear and logistic regression analyses, respectively.
  
  
  RESULTS
  At 100 days of lactation, group 1 cows produced significantly less milk (288 l; P = 0.001), milk fat (16.8 kg; P < 0.001) and milk protein (12.6 kg; P < 0.001) compared with group 4. At this lactation point, group 2 also produced significantly less milk fat (13.6 kg; P = 0.002) and milk protein (8.6 kg; P = 0.005) than group 4. At 305 days of lactation, group 1 cows produced significantly less milk (624 l; P = 0.004), milk fat (42.9 kg; P < 0.001) and milk protein (26.0 kg; P < 0.001) compared with group 4 cows. Group 2 cows also produced significantly less milk fat (21.2 kg; P = 0.033) at this lactation point. No statistically significant difference in reproductive performance was found upon pairwise comparisons of groups 1-3 with group 4 cows.
  
  
  CONCLUSIONS
  The present findings demonstrate that clinical oriental theileriosis can cause significant milk production losses in dairy cattle.
authors.forename: Piyumali K
authors.initials: PK
authors.lastname: Perera
authors.affiliation: Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia. robinbg@unimelb.edu.au.
authors.forename: Robin B
authors.initials: RB
authors.lastname: Gasser
authors.forename: Simon M
authors.initials: SM
authors.lastname: Firestone
authors.forename: Garry A
authors.initials: GA
authors.lastname: Anderson
authors.forename: Jakob
authors.initials: J
authors.lastname: Malmo
authors.forename: Gerry
authors.initials: G
authors.lastname: Davis
authors.forename: David S
authors.initials: DS
authors.lastname: Beggs
authors.forename: Abdul
authors.initials: A
authors.lastname: Jabbar
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis* / Q000469:parasitology; D016054:DNA, Protozoan / Q000097:blood*; D004196:Disease Outbreaks; D005260:Female; D007774:Lactation; D008892:Milk; D012098:Reproduction; D016794:Theileria / Q000235:genetics / Q000302:isolation & purification*; D013801:Theileriasis / Q000175:diagnosis* / Q000469:parasitology; D014739:Victoria / Q000453:epidemiology
chemical_list: D016054:DNA, Protozoan