Theileria-free waterbuck (Kobus defassa) born in captivity were succes
sfully infected with Theileria parva sporozoites derived from ticks in
fected by feeding on African buffalo (Syncerus caffer). All waterbuck
underwent mild infections with the development of sporadic schizont an
d piroplasm parasitosis when inoculated with sporozoite doses lethal t
o cattle. A carrier state of T. parva was demonstrated by feeding clea
n R. appendiculatus nymphs on two of these infected waterbuck. Tick ba
tches from these waterbuck on 2 of 5 occasions transmitted lethal Thei
leria infections to cattle. In a separate experiment, waterbuck cells
were infected and transformed in vitro by T. parva sporozoites derived
from buffalo but not by cattle-derived T. parva (Muguga) sporozoites.
Waterbuck cells infected in vitro with T. parva isolated from buffalo
were inoculated into autologous waterbuck but no infections developed
. Theileria parva isolates generated in this study from various source
s were characterized using anti-T. parva schizont monoclonal antibodie
s (MAbs), and it was found that buffalo-derived and waterbuck-passaged
isolates had different profiles. Species-specific synthetic oligonucl
eotide probes, restriction fragment length polymorphism (RFLP) analysi
s with cloned T. parva DNA probes, and DNA sequence analysis of the p6
7 sporozoite antigen gene confirmed that the waterbuck-passaged parasi
te was T. parva. The Tpr repetitive probe hybridization patterns from
the waterbuck-passaged parasites were different from the other samples
tested. The ribosomal genotype of the waterbuck-passaged T. parva was
similar to that of cattle-derived T. parva Muguga. Analyses with both
probes and MAbs suggested that a minor parasite population present wi
thin the T. parva 7014 buffalo-derived stock had been selected during
waterbuck passage. A variable region of the p67 sporozoite antigen gen
e of the waterbuck-passaged T. parva was similar to that of cattle-der
ived T. parva stocks and different from that of buffalo-derived parasi
tes. Based on these results, methods were suggested to confirm and qua
ntitate the involvement of waterbuck in the epidemiology of cattle the
ileriosis.