Abstract:
1. A record of the number of cases of tick-borne diseases in a herd of
adult cattle rather less than 1,000 in number over a period of four years is
given, viz., 8 cases of anaplasmosis of which 3 were fatal, 9 of redwater of
which 2 were fatal, and 79 of heartwater, of which 44 were fatal.
2. In a control group of 196 grade Angus animals under observation
from birth for a period of 3½ years there occurred 48 cases of heartwater
(37 fatal), 2 redwater (no deaths) and 2 gallsickness (1 death). The alarming
rate at which the animals were contracting heartwater compelled the Company
to deplete the herd after 3½ years for economic reasons by the sale of
125 oxen. Of the remaining 32 control animals 10 cases of heartwater (7
deaths), 2 redwater (no deaths) and 2 gallsickness (no deaths) occurred.
3. In a comparable group of 89 animals immunized against heartwater
the record shows 1 case of gallsickness which was fatal, no cases of redwater,
and 24 cases of heartwater of which only 11 were fatal.
4. In a grade herd 53 calves out of 1,374 = 3.9 per cent. ddied as a direct
result of immunization.
5: In the immunized herd (1,321 grades) there were 30 cases of redwater of which 15 were fatal, 18 cases of gallsickness of which 2 were fatal
and 121 cases of heartwater of which 66 were fatal.
7. There was no mortality amongst 27 adult purebred Aberdeen Angus
cattle varying from 1 months to 5 years and 9 months in age as a result of
immunization against heartwater and there was no subsequent mortality over
a period of three years.
8. Immunization of a mixed group of purebred Afrikaner cattle showed
that the Afrikaner is no more resistant to heartwater than the Aberdeen
Angus or Hereford.
9. Heartwater is the chief cause of mortality under ranching conditions
in the Northern Transvaal.
10. The control of tick-borne diseases is discussed and a system of animal
husbandry suggested.
