title: Efficacy of a Neospora caninum killed tachyzoite vaccine in preventing abortion and vertical transmission in dairy cattle.
abstract: A clinical trial was undertaken to assess the efficacy of Bovilis(®) Neoguard, a killed Neospora caninum tachyzoite vaccine on 5 commercial dairy farms in New Zealand with a history of Neospora-associated abortion. Cattle were enrolled in the trial at 30-60 days of gestation and randomly allocated to treatment or control groups. Treatment consisted of 5 mL doses of Bovilis Neoguard administered subcutaneously at enrolment then 4 weeks later. Isotonic saline was administered to the control group. Of 2246 cattle enrolled in the trial, 10.7% of cows and 12.6% of heifers were seropositive to N. caninum. Sampling of a randomly selected proportion of enrolled animals 6 weeks after the second treatment showed that 188/232 (81.0%) vaccinated with Bovilis(®) Neoguard had seroconverted, while 11/130 (8.5%) cows and 10/36 (27.8%) heifers in the control group had seroconverted. Forty-eight vaccinated and 63 control animals aborted. On one farm 12.5% of control animals and 6.1% of vaccinated animals aborted (vaccine efficacy 0.61; p=0.03). On another farm with a high level of abortion 8.4% of control animals and 8.7% of vaccinates aborted. On the remaining 3 farms fewer abortions occurred than expected. A modified Poisson regression approach was used to calculate relative risks for abortion and vertical transmission. Overall vaccine efficacy was 0.25 (p=0.12). Heifer replacement calves from the animals enrolled in the trial were sampled for antibodies to N. caninum at 6-9 months of age. Fourteen of 17 calves from vaccinated, seropositive cows were seropositive as were 13/23 calves from seropositive cows in the control group. The interaction between dam serostatus and treatment group was significant (p=0.05) with vaccination increasing the risk of vertical transmission. It was concluded that vaccination after conception prevented 61% abortions in one of five herds and that vaccination may have increased the risk of early embryonic death.
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand. J.F.Weston@massey.ac.nz
authors.forename: J F
authors.initials: JF
authors.lastname: Weston
authors.forename: C
authors.initials: C
authors.lastname: Heuer
authors.forename: N B
authors.initials: NB
authors.lastname: Williamson
mesh_terms: D000034:Abortion, Veterinary / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control*; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control*; D003048:Coccidiosis / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D003612:Dairying; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D015994:Incidence; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control / Q000662:veterinary*; D018688:Neospora / Q000276:immunology*; D009520:New Zealand; D011247:Pregnancy; D016052:Protozoan Vaccines / Q000276:immunology / Q000627:therapeutic use*; D014611:Vaccination / Q000662:veterinary; D015164:Vaccines, Inactivated / Q000276:immunology / Q000627:therapeutic use
chemical_list: D016052:Protozoan Vaccines; D015164:Vaccines, Inactivated