Vaccinations are an important part of a flock health management
program. They provide inexpensive "insurance" against
diseases that can commonly affect sheep and lambs.
On most farms, the only universally-recommended vaccine for sheep
and lambs is the CD-T toxoid. The CD-T toxid provides three-way
protection against enterotoxemia caused by Clostridium perfringens
types C and D and tetanus (lockjaw) caused by Clostridium tetani.
There are 7 and 8-way clostridal vaccines that provide protection against additional clostridial
diseases, such as blackleg and malignant edema, but the extra protection is often not necessary.
Enterotoxemia type C, also called hemorrhagic enteritis or "bloody
scours," affects lambs mostly during their first few weeks
of life, causing a bloody infection in the small intestine. Type
C enterotoxemia is often related to indigestion and is predisposed
by a change in feed, such as beginning creep feeding or a sudden
increase in the milk supply, perhaps caused by the loss of a littermate. The only way to protect lambs from type C enterotoxmia is to vaccinate their dams during late pregnancy.
Enterotoxemia type D, also called "classic" overeating disease or "pulpy
kidney disease," usually affects lambs over one month of
age. Usually it is the largest, fastest growing lamb(s) in the
flock that are affected. Type D overeating disease is usually
precipitated by a sudden change in feed that causes the bacteria,
already present in the lamb's gut, to proliferate, resulting
in a toxic, usually fatal reaction. Type D is most commonly
observed in lambs that are consuming high concentrate diets,
but can also occur in lambs nursing heavy milking dams.
To confer passive immunity to lambs through the colostrum (first
milk), ewes should be vaccinated with the CD-T toxoid approximately 4 weeks prior
to lambing. Ewes lambing for the first time should be vaccinated
twice in late pregnancy, four weeks apart. Maternal antibodies
will protect lambs for six to eight weeks so long as lambs
consume adequate amounts of colostrum. It is recommended that a lamb consume colostrum in the amount of 10 percent of its body weight.
Lambs should receive their first CD-T vaccination when they
are approximately 6 to 8 weeks of age, followed by a booster
4 weeks later. If pastured animals are later brought into
confinement or dry lot for concentrate feeding, a third vaccination should be given.
Lambs whose dams were not vaccinated for C and D can be vaccinated
with some success at two to three days of age and again in two
weeks. However, later vaccinations will likely be more effective, as
colostral antibodies usually interfere with vaccinations at very young
ages. The lamb's immature immune system may also not be able to respond to vaccination at such a young age.
A better alternative may be to vaccinate offspring from non-vaccinated
dams when they are approximately 4 weeks of age, followed by a booster 4 weeks
later. Anti-toxins can provide immediate short-term immunity
if dams were not vaccinated or in the event of disease outbreak
or vaccine failure.
Purchased feeder lambs should be vaccinated for type D enterotoxeia at
the time of purchase and 2 to 4 weeks later. Feeder lambs purchased
as 4-H or FFA projects should receive two type D vaccinations,
if they were not vaccinated at the farm of origin.
Lambs whose dams were not vaccinated for tetanus should be given
the tetanus anti-toxin at the time of docking and castrating,
especially if elastrator bands are used.
An antitoxin provides immediate short-term immunity. If a tetanus toxoid product is administered at the time of docking or castrating, it will not provide adequate immunity, as toxoids take 10 days to 2 weeks to provide immunity and require a booster for complete immunity.
Rams and pet sheep should be boostered annually with the CD-T toxoid. As with ewes, they require two vaccinations the first time they are vaccinated.
In addition to clostridial diseases, there are other diseases for which producers may wish to vaccinate. The use of additional vaccines depends upon the health status of the flock, the perceived disease risk of the flock, and prevalance of diseases in the geographic area where the flock is located. In the U.S. (for sheep), there are approved vaccines for sore mouth, foot rot, caseous lymphadenitis,
abortion, e. coli scours, parainfluenza-3 (PI-3), epididymitis,
and rabies. Vaccines that are not approved for sheep are also sometimes used.
There is an approved vaccine for soremouth (contagious ecthyma, orf),
a viral skin disease commonly affecting sheep and goats. The vaccine is live. It causes sore mouth infection (lesions) at a location
(on the animal) and time of the producers choosing. Ewes
should be vaccinated well in advance of lambing. Show animals
should be vaccinated well in advance of the first show.
To use the vaccine, a woolless area on the animal is scarified,
and the re-hydrated vaccine is applied to the spot with a brush
or similar applicator. Ewes can be vaccinated inside the ear
or under the tail. Lambs can be vaccinated inside the thigh.
Because the sore mouth vaccine is a live vaccine and sore mouth
is highly contagious to humans, care must be taken when applying
the vaccine. Gloves should be worn.
Flocks which are free from soremouth should probably not be
vaccinated because the soremouth vaccine will introduce the virus to the
flock/premises. Once soremouth vaccination is begun, it should
be continued annually.
Footrot is one of the most ubiquitous and economically devastating
diseases in the sheep industry. It causes considerable economic
loss due to the costs associated with treating it and the premature
culling of carrier animals. There are two vaccines for footrot
and foot scald in sheep: Footvax® 10 Strain and Volar
Neither vaccine prevents the diseases from occurring, but when
used in conjunction with other management practices such as
selection/culling, regular foot trimming, foot soaking/bathing,
etc., vaccinations can help reduce infection levels. Footrot
vaccines should be administered every 3 to 6 months,
prior to anticipated outbreaks of hoof problems (i.e. prior
to the wet/rainy season).
Abscesses (at the injection site) are not uncommon with the
foot rot vaccines. The limitation of foot rot vaccines is that they might not include the strain of foot rot that is present in a particular flock.
Caseous lymphadenitis (CL)
There is a vaccine for caseous lymphadenitis in sheep. CL affects
primarily the lymphatic system and results in the formation of
abscesses in the lymph nodes. It is highly contagious. When it
affects the internal organs, it evolves into a chronic wasting
The cost of CL to the sheep industry is probably grossly underestimated.
The CLA vaccine is convenient to use because it is combined with
CD-T. Vaccination will reduce the number of abscesses in the flock, but it will not prevent the disease from occuring.
Abortion is when a female loses her offspring during pregnancy
or gives birth to stillborn, weak, or deformed lambs. There
are vaccines (individual and combination) for several of the
infectious causes of abortion in sheep: enzootic (EAE/Chlamydia
sp.) and vibriosis (Campylobacter fetus).
Abortion vaccines should be administered prior to breeding.
Ewes being vaccinated for the first time should receive a second
vaccination (booster) in mid-pregnancy. Producers with problem
flocks may consider giving a booster as well. Risk factors for
abortion include an open flock and/or a history of abortions
in the flock.
Unfortunately, there is no vaccine (available in the U.S.) for
toxoplasmosis, another common cause of abortion in sheep. Since
the disease-causing organism is carried by domestic cats, the
best protection is to control the farm's cat population by spaying/neutering
and keeping cats from contaminating feed sources.
Epididymitis is a major cause of reduced fertility in rams from
western range states. There are vaccines for epididymitis (Brucella
ovis), but none are deemed fully effective. In addition, vaccination
interferes with the ability to eliminate infected rams from the
flock, as vaccinated rams will test positive for B. ovis.
Scours in baby lambs can be caused by E. coli. There
is a vaccine that can be administered to ewes at the same time
as CD-T to pass immunity to lambs through the colostrum. An
alternative to vaccination is to give newborn lambs oral E.
coli antibody at birth.
Though the risk to sheep is usually minimal, rabies vaccination
may be advised if the flock is located in a rabies-infected
area, the animals are valuable, and livestock have access to
wooded areas or areas frequented by raccoons, skunks, foxes,
or other known carriers of rabies. Frequent interaction with
livestock may be another reason to consider vaccinating.
The cost of the rabies vaccine relative to the value of the
animals should be considered. The large animal rabies vaccine
is approved for use in sheep. Producers should consult their
veterinarian regarding rabies vaccination. Some states require
rabies vaccination for exhibition at fairs and shows. All dogs
and cats on the farm should be vaccinated against rabies.
When no commercial vaccine is available, autogenous or custom
vaccines can be made. They are usually made from bacteria or
viruses that have been isolated on a farm in conjunction with
a disease. Autogenous vaccines are usually not as effective
as commercial vaccines.
Most vaccines are given subcutaneously (sub-Q), i.e. under the
skin. Some vaccines are given intramuscularly (IM). Occasionally,
some are given topically (e.g. sore mouth) or intranasally (e.g.
Nasalgen®). For subcutaneous vaccines, use a 1/2 or 3/4
inch, 18- or 20-gauge needle. Subcutaneous vaccinations can
be given over the ribs, behind the armpit, or high up on the
neck. The needle used to withdraw vaccine from the bottle should
not be the same needle used to inject the animal.
In order for vaccination programs to be successful, label directions
should be carefully followed. Vaccines should be stored, handled,
and administered properly. Only healthy sheep and lambs should
be vaccinated. It is also important to note that vaccines have
limitations and that the immunity imparted by vaccines can sometimes
by inadequate or overwhelmed by disease challenge.
With the increasing role of small ruminants in small farms and
sustainable farming systems, hopefully animal health companies
will develop and license more vaccines for sheep.
Scientists are currently working to develop vaccines to protect
small ruminants against Haemonchus contortus and other
gastro-intestinal and blood-sucking parasites. The research is
promising. Thus far, the challenge has been developing effective vaccines using
recombinant DNA technology, as other methods of vaccine generation are not economically feasible.
Many sheep producers will tell you that they never vaccinate. Other producers vaccinate for diseases which are not a high risk. Vaccination is a form of risk management. Each producer must weights the pros and cons of vaccinating for a specific disease. If the cost of vaccination excees the expected losses, then vaccination is probably not cost-effective. Conversely, if expected losses exceed the cost of vaccination, they vaccination is a good risk management tool.
At the same time, it is not advisable to wait until you have a disease outbreak before instituting a vaccination program. The risk of a diseaes outbreak should be the criteria that is used to determine the need for vaccination. A producer's tolerence for risk will also come into play.
<== SHEEP 201 INDEX