The study was performed in a Holstein–Friesian dairy
herd with a history of high Neospora-associated abortions
The herd was kept under an inten-
sive maintenance system with strict minimized access of
canids. The cows were automatically screened for general
signs of disease or distress by computerized monitoring
(SCR Heatime® HR System). All the animals were rou-
tinely bred by artificial insemination.On day 110–130 post
insemination, pregnancy examinations were performed by
fetal-membrane slip method.Blood samples for serolog-
ical examination were collected from all pregnant cows.
The presence of antibodies to N. caninum was examined by
indirect fluorescent antibody test (IFAT) according to
A tota lof 520 seropositive dams with titers of
1:400 or higher were included in the experiment.Dams
were randomly assigned to a vaccinated(n = 146)or a con-
trol (n = 374) groups in a ratio of 3:7 due to availability ofthe
amount ofvaccine.Inadditiontovaccinationofseroposi-
tive dams;fourhealthyuninfectedcalvesaging6–9months
and twoadditionalseronegativeto N. caninum pregnant
cows, werevaccinatedinordertoverifythesafetyofthe
vaccine. Vaccinationwasperformedsubcutaneouslyinthe
anterior neckbetween125and150daysofpregnancy.
The outcomeofthepregnancieswasrecordedandabort-
ing damswereexaminedforexclusionofotherpossible
abortifacient agents(as Leptospira sp, Chlamydia sp, Coxiella
burnetii (causing Qfever),and Brucella sp). Thevertical
transmission incidencewasestimatedfromthepropor-
tion ofseropositivecalvesat12–18monthsofage.When
possible, follow-upofthedamsforuptothreeconsecu-
tive pregnancieswasconductedtoexaminetheprolonged
effect ofthevaccination.Theexperimentswereper-
formed incompliancewiththerequirementsoftheAnimal