An infection with Ehrlichia phagocytophila, the agent of tickborne fever, can cause abortion or stillbirth in cows in late pregnancy but, to the authors' knowledge, there have been no reports of intrauterine infection in cows followed by clinical signs in the calf. To study the effect of E phagocytophila on the fetus, a cow was infected experimentally after 270 days of pregnancy. It developed the clinical and haematological signs characteristic of tickborne fever six days after infection. At 287 days of pregnancy the cow gave birth to a live calf, which became ill at 13 days of age. The general condition and behaviour of the calf were only mildly affected but it had a high temperature and swollen prescapular lymph nodes. Its appetite and suck reflex remained normal. E phagocytophila inclusion bodies were visible, predominantly in neutrophils and eosinophils, for seven days. The calf seroconverted, as detected by indirect immunofluorescence, 14 days after it became ill.
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