title: Serological survey of Toxoplasma gondii and Campylobacter fetus fetus in sheep from New Zealand.
abstract: OBJECTIVE
  To determine the prevalence of antibody titres to Toxoplasma gondii and Campylobacter fetus fetus in sheep from New Zealand.
  
  
  METHODS
  As part of a free screening service, unsolicited blood samples were supplied by veterinarians wishing to gauge the exposure of their clients' ewe flocks to T. gondii and C. fetus fetus. Blood samples were submitted from mixed-age ewes throughout New Zealand, from 2006 to 2009, that had not been vaccinated for T. gondii and C. fetus fetus. A total of 2,254 sera were serologically titrated for T. gondii and 3,429 for C. fetus fetus. A latex agglutination kit available commercially was used to quantify antibodies to T. gondii, and an agglutination test developed in-house was used for C. fetus fetus. For T. gondii, titres of ≥1:16 and ≥1:64 were used to define a positive response, and for C. fetus fetus a titre of ≥1:10 was defined as positive. A flock was defined as positive if ≥1 ewe had a positive titre.
  
  
  RESULTS
  Of the sera tested for T. gondii, 1,917/2,254 (85%) were positive, using a titre of ≥1:16, and 1,384/2,254 (61%) with a titre of ≥1:64. All 198 ewe flocks tested were seropositive to T. gondii, at a titre of ≥1:16, and all but three were at a titre of ≥1:64. A bimodal distribution was evident in the prevalence of titres to T. gondii suggesting that a percentage of titres ≤1:64 may have been non-specific. Of the sera tested for C. fetus fetus, 1,644/3,429 (48%) were positive to at least one of the four test antigens at titre of ≥1:10. Only 34/298 (11%) flocks tested for C. fetus fetus were completely seronegative. The percentage of seropositive ewes to both T. gondii and C. fetus fetus was significantly higher in the North Island than the South Island.
  
  
  CONCLUSIONS
  The study demonstrated that exposure to these two important infectious abortifacients was both considerable and widespread. Minimum titres were postulated to establish a 'cut-off' for a positive result and to allow comparison with past and future studies. The bimodal distribution evident for T. gondii suggested a titre of 1:64 may be an appropriate cut-off. The widespread on-farm exposure probably stimulates the immune response of vaccinated ewes.
  
  
  CONCLUSIONS
  Further studies are required to confirm the clinical significance of flock-based antibody responses, and to validate their use in identifying recently aborted ewes, especially where there are no aborted fetuses for examination.
authors.affiliation: Intervet/Schering-Plough Animal Health Ltd, Upper, New Zealand. robert.dempster@virbac.com.au
authors.forename: R P
authors.initials: RP
authors.lastname: Dempster
authors.forename: M
authors.initials: M
authors.lastname: Wilkins
authors.forename: R S
authors.initials: RS
authors.lastname: Green
authors.forename: G W
authors.initials: GW
authors.lastname: de Lisle
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000913:Antibodies, Protozoan / Q000097:blood; D002169:Campylobacter Infections / Q000097:blood / Q000453:epidemiology* / Q000662:veterinary; D002168:Campylobacter fetus / Q000276:immunology*; D005260:Female; D005843:Geography; D007841:Latex Fixation Tests / Q000662:veterinary; D009520:New Zealand / Q000453:epidemiology; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D012756:Sheep; D012757:Sheep Diseases / Q000097:blood / Q000453:epidemiology* / Q000382:microbiology; D014122:Toxoplasma / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000097:blood / Q000453:epidemiology*
chemical_list: D000907:Antibodies, Bacterial; D000913:Antibodies, Protozoan