Vaccinations are an integral part of a flock health management program. They provide protection against diseases that can commonly affect sheep and lambs.
In many cases, the only recommended vaccine for sheep and lambs is CD-T. The CD-T vaccine provides three-way protection against enterotoxemia caused by Clostridium perfringins types C and D and tetanus (lockjaw) caused by Clostridium tetani. Combination vaccines that include additional clostridial diseases, such as blackleg and malignant edema are available, but generally not necessary for most sheep flocks.
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 milk supply, perhaps caused by the loss of a littermate.
Enterotoxemia type D, also called overeating disease, generally affects lambs over one month of age. Usually it is the largest, fastest growing lambs in the flock that are afflicted. 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.
Clostridium tetani (lock jaw)spores are distributed in the soil, intestine and feces. They enter the body through a wound, typically at castration or tail docking. In the presence of low oxygen conditions, the spores germinate, producing toxins. The toxins produced lead to muscle contraction and spasm.
To confer passive immunity to lambs through the colostrum (first milk), ewes should be vaccinated for CD-T two to four weeks prior to lambing. Ewes lambing for the first time should be vaccinated twice in late pregnancy, about four weeks apart. Maternal antibodies will protect lambs for six to eight weeks, assuming lambs have consumed enough colostrum.
Lambs should receive their first CD-T vaccination when they are approximately six to eight weeks of age, followed by a booster two to four weeks later. If pastured animals are later brought into confinement or dry lot for concentrate feeding, producers should consider re-vaccinating them for enterotoxemia type D.
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 be more successful since colostral antibodies interfere with vaccinations at very young ages.
A better alternative may be to vaccinate offspring from non-vaccinated dams at one to three weeks of age, followed by a booster three to four weeks later. Antitoxins 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 against type D at the time of purchase and 2 to 4 weeks later.
There is a live vaccine for soremouth (contagious ecthyma, orf), a viral skin disease commonly affecting sheep and lambs. 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 rehydrated 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 vaccine will introduce the virus to the flock/premises. Once soremouth vaccination is begun, it should be continued yearly.
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 affected animals.
Vaccination does not prevent the diseases from occurring, but when used in conjunction with other management practices such as selection/culling, regular foot trimming, foot soaking/bathing, etc., they may help reduce infection levels. Footrot typically responds well to antibiotic therapy.
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 disease.
The cost of CL to the sheep industry is probably grossly underestimated. Vaccination will reduce the number of abscesses in the flock.
Abortion is when a female loses her offspring during pregnancy or gives birth to stillborn, weak, or deformed lambs. There are vaccines for some 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 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.
Scours in baby lambs is frequently caused by E. coli. There is a vaccine that can be administered to ewes pre-breeding to pass immunity to lambs through the colostrum. An alternative to vaccination is to give newborn lambs an oral E. coli antibody product at birth.
Most vaccines are given subcutaneously. Some vaccines are given intramuscularly. Occasionally, some are given topically (e.g. sore mouth). 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 be inadequate or overwhelmed by disease challenge.