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Lamb dysentery can be controlled through vaccination against clostridial diseases. Before ewes enter the breeding flock, they should be given two vaccinations separated by an interval of 4-6 weeks. An annual booster should be given about six weeks before lambing to afford passive protection to lambs until around sixteen weeks of age. Lambs born to unvaccinated ewes should themselves be vaccinated at between 3 and 12 weeks old, with a second injection given at least four weeks later. Good husbandry is also critical to the control of lamb dysentery. Lambing is a particularly important period where supervision and hygiene should be maintainted and adequate colostrum intake should be ensured. Care should be taken when introducing animals to an improved plane of nutrition.
Lamb dysentery can be controlled through vaccination against clostridial diseases. Before ewes enter the breeding flock, they should be given two vaccinations separated by an interval of 4-6 weeks. An annual booster should be given about six weeks before lambing to afford passive protection to lambs until around sixteen weeks of age. Lambs born to unvaccinated ewes should themselves be vaccinated at between 3 and 12 weeks old, with a second injection given at least four weeks later. Good husbandry is also critical to the control of lamb dysentery. Lambing is a particularly important period where supervision and hygiene should be maintainted and adequate colostrum intake should be ensured. Care should be taken when introducing animals to an improved plane of nutrition.
lewis Treatment of individual cases of
clostridial disease is usually unrewarding
since the body systems have been
irreparably damaged by toxins by the
time signs are observed. Usually the
first indications of clostridial disease is
a dead animal. It is at this stage that a
definitive diagnosis should be sought
and every effort should be made to
persuade the farmer to submit the
carcase without delay to the local
veterinary investigation centre, before
further losses occur.
Control of an outbreak of clostridial
disease involves a dual approach of
management techniques and therapy.
In the case of the enterotoxaemias,
vaccination in the face of an outbreak
has proved effective (West 1993).
Alternatively, particularly for lamb
dysentery and tetanus, antisera can be
administered. Management measures
for some of the clostridial conditions
include the removal of the remainder
of the flock from a particular pasture
or a reduction in concentrate feeding.
The reduction of stress factors, as well
as the gradual introduction of any
new feeds or feeding regimens, also
reduces the likelihood of disease. The
cost of controls can be high in terms of
time, labour and possibly further losses
due to the stress of gathering the
animals for treatment. Of all the diseases
that afflict sheep, the clostridials
are the ideal candidates for control by
vaccination.
Vacdction
Before the advent of modern vaccines,
losses from clostridial diseases could
be cata-strophic, on occasion running
at over 30 per cent. By the mid-1970s,
efficient multicomponent vaccines
were widely available and in the mid-
1980s the clostridial components were
combined with multicomponent pasteurella
antigens. Clostridial vaccines
are, except for the C chauvoei component,
directed at the toxins produced
by the various pathogenic members of
the clostridial family. Referred to as
toxoids, they are inactivated and
require an adjuvant for better stimulation
of the immune system.
Whether a straight clostridial vaccine
or a combined vaccine is used, the principles
underlying efficacious vaccination
programmes are identical. For
effective protection of sheep, of whatever
age, a primary course of two
doses, administered four to six weeks
apart, is required. The first dose can be
considered a sensitising dose and, the
second, the confirming dose. Immunity
wanes over a period of a year and,
consequently, booster doses are
required annually.
* EWES. Vaccination should be performed
four to six weeks before lambing
is due. Where lambing is prolonged,
the late lambers should be
identified and boosted later, closer to
their lambing date.
* LAMBS. By virtue of the ewe's
enhanced ability to concentrate circulating
antibodies into the colostrum
(Cooper 1967), lambs ingesting sufficient
colostrum from adequately fed
ewes receive sufficient maternal antitoxins
to protect them for about 12
weeks. Such maternal protection is
essential to prevent lamb dysentery,
tetanus and early enterotoxaemia
caused by C perfringens type D.
Lambs from fully vaccinated ewes
can start their primary course from
eight weeks of age, as maternally
derived antitoxin does not appear to
interfere with the response to the vaccine.
The choice and combination of
antigens to be used depends on the
ultimate fate of the lamb. Those to be
retained for breeding require the full
complement of antigens. Those for
early slaughter may only require protection
against pulpy kidney disease
and tetanus, while lambs aimed at the
store market or autumn finishing
require a wider range of antigens to
give additional protection against
braxy, blackleg and malignant oedema.
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