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Table 2. ECF reactons in Mal3: UnguJa ECF lmmunisadon
Group
I
Identity of
animal
Days to
uchlzont
Duration
schizont of
(days)
Day to
pyraxla
Duration of
pyrexla
Cause of
death
(days)
Immunised CB5 30
2
CB9 25
CB11 -
CB12 -
CB15 -
CB16 -
CB17 -
CB20 -
CB21 -
CB22 -
CB23 -
CB24 -,
T mutans
Control CB'7 28
Souroe: Raba (98).
C 8 43
CB13 -
CB14 -
CB18 -
(Aher experiences gained
Immunisation against ECF proved effective in
these trials and field immunisation was started
in 1990. Acceptancn by farmers was good, with
about 500 pure-bred Jerseys, Friesians and their
crosses having beeu immunised. However, the
trials have shown that when immunisation
against ECF has been completed other tickborne
diseases are being detected and are a cause
for concern. The most significant tick-borne
disease to surface is babesiosis.
Experience gained has also ohown that
anaemia and low packed cell volume (PCV) can
be a problem in cattle immunised against T
parva. Othey: researchers (Uilenberg, 1984;
Morzaria, 1988) have reported anaemia and
parasitaemia during exposure of ECFimmunised
cattle. The anaemia syndrome has
been associated with high T. mutans
parasitaemia (Rabia, 1989. Poor nutrition has
also been associated with the anaemia syndrome
and parasitaemia (Biw5, 1')91). From this
experience, it has been recommended that only
115
2 ­
3-
- - --
- 225
- 18
- -
- 32
- 17
- -
- - - -
- - - -
- 56
- 15
11 29
2 44
- 15
-
- -
- - - -
1
-
1 ­
1 ­
1 ­
2 ­
9 ECF (38)
1 ­
6 ­
well-nourished cattle should be immunised, with
further studies being conducted on the possible
pathogenicity of T mutans.
The age at which calves should be immunised
is still in debate. While Rabia (1991) rocommended
six months of age as being optimal,
this was in conflict with studies by de Boorder
(1989) who recommended immunisation of much
younger calves, at between one and two months
ofage. Immiunisation at a later age appears to be
more practical where zero-grazing is practised
and early contact with ticks can be controlled.
This situation is rat possible in natural grazing.
On the other hand, passive immunity from the
mother may interfere with immunisation at a
very early age; in addition, the calf may not be
able to develop an effective immune response
because of its immaturity.
Future prospects
Field ECF immunisation has so far been
successful (Dolan, 1992). Five hundred pure and
crossbred cattle have been vaccinated. Farmer
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