ABSTRACT. Primary culture of bovine brain cells was examined for its susceptibility to Neospora caninum infections, and this model was used to investigate the effects of bovine interferon gamma (IFN-γ) and tumor necrosis factors alpha (TNF-α) on tachyzoite growth. Tachyzoites of N. caninum grew well in this culture, and tachyzoite growth in astroglia and microglia were confirmed by immunocytochemical staining. IFN-γ inhibited the tachyzoite growth, and this inhibition was not reversed by the addition of nitric oxide antagonist. TNF-α, to a lesser extent, also inhibited the tachyzoite growth. Th-1 type cytokines may play an important role in host defense mechanisms in N. caninum infection.-KEY WORDS: brain culture, cytokine, Neospora caninum.

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ABSTRACT. A retrospective cohort study was conducted to clarify the association between seropositive reactions to Neospora caninum and subsequent reproductive disorders among dairy cattle in Japan. A statistically significant association between Neospora seropositive reactions and abortions was observed (P=0.016), and seropositive cattle were 6.1 times more likely to abort compared to seronegative cows. No significant differences were observed between seropositive reactions and other reproductive disorders such as conception failure, perinatal death and calf mortality. As indicated by estimation of the attributable fraction, 83.6% of abortions in Neospora seropositive animals may be attributed to N. caninum. Considering seroprevalence of N. caninum in the cattle which aborted in Japan, 21.8% of abortions were estimated to be caused by neosporosis in Japan.

Up to October 2004, dogs and cats imported into Japan were subjected to a quarantine regimen which consisted of vaccination and a 30- to 365-day waiting period in the country of origin and a 14-day quarantine period upon arrival in Japan. This regimen was replaced by a new one, consisting of vaccination, antibody level titration and a 180-day waiting period in the country of origin, in November 2004. To evaluate the effect of this policy change, a quantitative risk assessment was undertaken. The risk of rabies entering Japan through the importation of dogs and cats from the USA under the old - and new - regimens was quantitatively assessed and compared. Under the new regimen, rabies will enter Japan once every 4932 years (90% confidence interval 1812-13 412 years) through the importation of dogs and cats from the USA. Under the old regimen, rabies would enter Japan once every 70 years (39-205 years), 83 years (45-267 years) or 190 years (104-609 years) assuming that the animal departs the country of origin 30 days, 180 days or 365 days after vaccination, respectively. This indicates the policy change would reduce the risk by a factor of 1/25-1/70.

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