CRYPTOSPORIDIUM-PARVUM INFECTION IN BOVINE NEONATES - DYNAMIC CLINICAL, PARASITIC AND IMMUNOLOGICAL PATTERNS

Twenty-six experimentally infected calves were monitored daily for ooc yst excretion. All began excreting oocysts 3-6 days p.i. Most calves ( n = 23) excreted oocysts for 6-9 days, with a daily range from 4 x 10( 2) to 4.15 x 10(7) oocysts g(-1) of faeces. Over half the calves excre ted peak numbers of oocysts 6-8 days p.i. Diarrhoea, observed intermit tently beginning as early as day 3 p.i., lasted 4-16 days and varied g reatly in severity from calf to calf. In a second study, nine of 18 ca lves were orally inoculated with 5 x 10(6) oocysts between birth and 2 days of age and nine remained uninfected. Monoclonal antibodies for c ell surface markers indicated substantial increases in CD4+ and CD8+ T cells in the intraepithelial lymphocyte population of the ilea of inf ected calves at 7-9 days of age. RT-PCR demonstrated increases in mRNA for interleukin-12 and interferon-gamma that correlated with increase s in both CD4+ and CD8+ intraepithelial lymphocyte cells. Increased mR NA for interleukin-12 and interferon-gamma from lamina propria lymphoc ytes correlated with increased numbers of CD8 + cells. No changes were found in interleukin-2, interleukin-4 or interleukin-10 mRNA levels. However, interleukin-15 mRNA, possibly from epithelial cells contamina ting intraepithelial lymphocytes, was decreased in infected calves and had a negative correlation with increases in CD4+ and CD8+ cells. No differences were detected in mRNA levels for cytokines from lymph node lymphocytes. Published by Elsevier Science Ltd on behalf of the Austr alian Society for Parasitology.