WildLife Group
of the SAVA
Laboratory tests
barrier by means of double fencing and possibly jackal
proofing. Ideally, to prevent fence line contact with
animals and contamination with abortion products
from adjacent farms, an exclusion zone of 3 – 5
meters should separate the two fences. This has the
added advantage that if cleared of woody vegetation,
this exclusion zone can be used as an access road for
patrolling the fences as well as a fire break. These
fence line interfaces with infected cattle farms have
already resulted in several transmission events which
resulted in the infection of adjacent “clean” buffalo
herds.
Control
In addition, the wildlife industry should be made
aware of the current Brucellosis -risks associated
with sable antelope and should push for compulsory
testing of all sable prior to sale or movement. Ideally,
this should also be expanded in the future to include
other “high value” species such as roan antelope,
eland, waterbuck and gemsbok.
The standard suite of brucellosis serological tests (RBT,
SAT & CFT) will detect infection / exposure with /to
either Brucella organism. With buffalo, in previously
negative herds, a positive RBT or RBT+SAT result
should be viewed with utmost suspicion, and retesting, especially post calving testing are mandatory.
A positive RBT or SAT in a Brucella positive herd
should be considered a positive reactor and should
not be left to calve in the herd. In positive herds
one needs to be ruthless if one is culling positive or
suspect animals to control and eradicate infection.
In cattle, bovine brucellosis outbreaks are generally
controlled by placing the farm under quarantine,
followed by regular testing of all cattle on a 2 – 3
month rotation. All positive animals are culled.
Vaccination of all cows with strain19 vaccine may
also be used with State Veterinary approval, but
vaccinated adult cows will sero-convert for varying
periods of time which complicates test interpretation.
Vaccination with RB51 vaccine is less problematic.
Prevention in cattle is by means of vaccinating all
heifer calves between the ages of 4 – 8 months. This
can be highly successful, if 90% + of the heifers are
vaccinated annually.
With regards to wildlife, the best control measure for
brucellosis is prevention, prevention, prevention !!!
Once Brucellosis has been introduced into a wildlife
population, control and eradication are very difficult
and costly. Exactly for these reasons, a negative test
for brucellosis is a legal requirement for all buffalo
movements in South Africa.
In addition, wildlife ranchers should be encouraged
to source their wildlife purchases from reputable
breeders /ranchers with a good track record of disease
screening and prevention. High risk animals such as
vagrant (dwaal) buffalo or illegally imported sable
antelope should be avoided at all costs.
Where a wildlife ranch has a common boundary
with a Brucella infected or suspect cattle or small
stock farm, it is advisable to strengthen the interface
16
Vaccination is currently not an option for wildlife
because the efficacy and safety of the available cattle
/small stock vaccines have not been validated in
buffalo or sable. In addition some vaccines may cause
sero-conversion which complicates the interpretation
of diagnostic tests. The use of RB-51 vaccine has been
suggested, because it is a gene-deleted vaccine and
should not interfere with diagnostic tests. However,
it has been tried in elk and bison in the USA and
was found to cause some abortions in bison, and
apparently did not protect elk from infection. For this
reason, National Veterinary Services (DAFF) are totally
opposed to Brucella vaccination of wild species.
Applied research is required before this option can be
re-evaluated.
VPH Considerations
Both Brucella abortus and Brucella melitensis
infections in animals are potentially zoonotic. Infected
cows milk, goats milk or camel milk and their products
(especially cheese) are the most common sources
of [