CD&T Vaccine for Sheep: What It Covers and When to Give It

Author: Elliott Garber, DVM

The CD&T vaccine is the one shot almost every sheep should get. It protects against three clostridial diseases at once: enterotoxemia caused by Clostridium perfringens types C and D (the “overeating disease” that kills fast-growing and grain-fed lambs), plus tetanus caused by Clostridium tetani. The standard plan is to booster pregnant ewes a few weeks before lambing so protective antibodies pass to their lambs through colostrum, then vaccinate the lambs themselves with a primary dose plus a booster a few weeks later, followed by an annual booster for the whole flock. It is given as a small injection under the skin, and your veterinarian sets the exact product, dose, and timing.

What CD&T actually protects against

CD&T is a clostridial vaccine, meaning it targets diseases caused by Clostridium bacteria. These organisms live in soil and in the gut, produce potent toxins, and can kill a healthy-looking animal within hours. The vaccine works by exposing the immune system to inactivated versions of those toxins (a toxoid) so the animal builds antibodies before it is ever challenged.

The three letters stand for the three things it covers, according to the Merck Veterinary Manual and Mississippi State University Extension:

• C = Clostridium perfringens type C, which causes a bloody, often fatal enterotoxemia in very young lambs.
• D = Clostridium perfringens type D, the classic “overeating disease” or “pulpy kidney” that hits fast-growing lambs on rich feed. Type D is the most common and important form of enterotoxemia in sheep.
• T = tetanus, caused by Clostridium tetani, which enters through wounds and produces the muscle stiffness, spasms, and “lockjaw” that give the disease its name.

Enterotoxemia and tetanus are both largely preventable with vaccination and both are dangerous once they take hold, which is why CD&T is considered the core vaccine for a sheep flock rather than an optional extra.

Why “overeating disease” is a feeding problem

Type D enterotoxemia earns its nickname because it is triggered by feed, not by contagion. Clostridium perfringens type D normally lives quietly in the gut in small numbers. When an animal takes in a large, sudden load of readily fermentable carbohydrate, the bacteria bloom and flood the gut with epsilon toxin. Michigan State University Extension notes that this typically strikes fast-growing lambs eating large amounts of feed, grain especially, and nursing lambs on heavy-milking ewes.

The practical triggers are familiar to anyone who has kept sheep: a jump onto grain or creep feed, a broken gate that lets the flock into the feed room, or a move onto lush spring pasture. Vaccination does not replace careful feeding. It is your safety net for the day something goes wrong, so pair the shot with gradual feed changes and consistent rations. Our sheep feeding guide and minerals guide cover keeping the rumen on an even keel.

The vaccination program, in concept

There is no single universal schedule, and the exact timing depends on the product, your lambing setup, and your veterinarian’s advice. But the underlying logic is consistent across extension services, and it is worth understanding so the schedule your vet gives you makes sense.

Start with the pregnant ewe

A newborn lamb has almost no immune protection of its own. It gets its first defense entirely from colostrum, the antibody-rich first milk, in the first day of life. By boostering the ewe before she lambs, you load that colostrum with CD&T antibodies so the lamb is protected from birth.

The widely taught timing is to booster the ewe about 3 to 4 weeks before lambing, per Mississippi State Extension and the Ohio State University Small Ruminant Team. A ewe that has never been vaccinated needs an initial two-dose series to respond well, so first-time or unknown-history ewes are sometimes given two shots in the run-up to lambing rather than one. Your vet will tell you which situation you are in.

Then vaccinate the lambs

The antibodies a lamb receives through colostrum fade over the first weeks of life. Extension guidance from MSU describes lambs beginning to lose that passive immunity around six weeks of age, which is when their own vaccination needs to take over.

So lambs get their own primary dose, followed by a booster a few weeks later. Two doses matter: the first dose primes the immune system and the second dose is what actually builds durable protection. A single shot is not enough. Lambs born to ewes that were not boostered before lambing may need to start earlier, because they never received strong colostral protection to begin with. This is a judgment call for your veterinarian.

Keep it up every year

After the lamb’s initial two-dose series, protection is maintained with an annual booster. That yearly shot applies to the whole flock, ewes, rams, and wethers alike. For breeding ewes, timing the annual booster to fall a few weeks before lambing does double duty: it keeps the ewe protected and refreshes the colostrum for the next lamb crop. Our sheep gestation guide and lambing guide can help you line up the pre-lambing booster with the rest of your calendar.

How and where the shot is given

CD&T is given subcutaneously, meaning under the skin rather than into muscle. A common site is the loose skin behind the elbow (the axilla, or “armpit”) or over the ribs, where you can tent the skin up between your fingers and slide the needle into the pocket underneath. Extension guidance favors these loose-skin sites because they are easy to tent and keep the needle out of the valuable cuts of the carcass.

A few practical points that make the job cleaner:

• Inject into clean, dry skin. Vaccinating wet or muddy animals raises the risk of an abscess at the site.
• Expect a small lump. A temporary knot or swelling at the injection site is a normal reaction to a clostridial vaccine and usually resolves on its own. On show and market lambs, many producers choose the armpit specifically so any lump is hidden.
• Handle the vaccine correctly. Follow the product label for storage and use a fresh needle. Your veterinarian can walk you through dose and technique the first time.

This guide does not give doses on purpose. Clostridial products differ, and the correct volume, needle, and schedule belong to your veterinarian and the label, not a blog. Once you have vaccinated, log the product, date, and site so the next dose lands on time. You can keep that on your animal’s health and medical records in Creatures and set a reminder for the annual booster.

Tetanus cover at docking and castration

The “T” in CD&T matters most around the times you create a wound. Tail docking and castration, especially with elastrator bands, produce exactly the kind of low-oxygen, closed-off tissue where Clostridium tetani thrives. Ohio State Extension notes that banding creates the anaerobic conditions tetanus favors, and that infection risk from banding drops when animals are already protected by vaccine.

The cleanest approach is to time your program so lambs already carry protection before those procedures, either from colostrum (if the ewe was boostered before lambing) or from their own vaccination. When a lamb’s tetanus status is uncertain, veterinarians sometimes add tetanus antitoxin at the time of docking or castrating for immediate, short-term cover, which is different from the CD&T vaccine and something to discuss with your vet. Whichever route you take, do not band an unprotected lamb and hope for the best. See our tail docking guide for how the timing of docking fits alongside vaccination.

Keeping the schedule straight

The single biggest reason CD&T fails is not the vaccine. It is a missed booster: a lamb that got one dose but never the second, or an adult whose annual shot slipped a year. Because the protective response depends on those repeat doses landing on time, a written record beats memory every time.

If you keep your flock on Creatures, add each animal and log the vaccine under its health records, then set a reminder so the next dose shows up in your upcoming care before it is overdue. That is genuinely useful at lambing time, when you are boostering ewes on a tight window and juggling a new lamb crop. You can browse the rest of the sheep species page for the guides that pair with this one, and if you are still naming this year’s lambs, the sheep name generator is there when you need it.

Frequently asked questions

Is the CD&T vaccine really necessary for pet sheep?

Yes. Enterotoxemia and tetanus are just as fatal in a backyard wether as in a commercial flock, and both are largely preventable. CD&T is considered the core vaccine for sheep regardless of flock size or purpose. Talk to your veterinarian about the right schedule for a small group.

Can I give CD&T myself, or does it have to be a vet?

Many shepherds give routine CD&T themselves once a veterinarian has shown them the correct dose, site, and technique. The key is that your vet sets the product and schedule and confirms the plan for your flock. Store and handle the vaccine per the label, use clean needles, and log every dose.

What is the difference between CD&T vaccine and tetanus antitoxin?

The CD&T vaccine (a toxoid) trains the immune system over time and needs a primary series plus boosters to work. Tetanus antitoxin gives immediate but short-lived protection and is sometimes used at docking or castration when an animal is not yet vaccinated. They are different tools. Your veterinarian will tell you if and when antitoxin is warranted.

My sheep has a lump where I gave the shot. Is that a problem?

A small, firm lump at a subcutaneous injection site is a common and usually harmless reaction to clostridial vaccines that typically fades over time. A hot, painful, or draining swelling is different and may be an abscess, which is worth having your veterinarian look at. Injecting into clean, dry skin lowers the risk.

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