Shepherds use vaccines to boost immune system of flocks

URBANA, Ill. — Shepherds should consider what diseases are on their farms to develop a disease prevention strategy.

“Depending on what diseases we know are in the area, we can help fortify the immune system with vaccinations against the diseases they may be exposed to,” said Tessa Marshall, lecturer in the College of Veterinary Medicine at the University of Illinois.

“Just because we vaccinated an animal doesn’t mean we’re going to prevent disease,” said Marshall during a presentation at Illinois Sheep Day, hosted by Illinois Lamb and Wool Producers at the University of Illinois.

“Vaccines will aid in the prevention of disease, but it doesn’t mean the sheep are not going to get sick,” she said. “The goal for vaccinations is to boost the immune system, so if the sheep get exposed to the disease, it’s less severe.”

There are two types of immunity, adaptive and innate.

“Adaptive immunity comes from vaccines where we are trying to implement change or assist the immune system,” Marshall said. “Innate immunity is what we’re born with, like skin, which is our biggest barrier to prevent disease getting into us.”

White blood cells circulate to help fight infection and digestive enzymes help to stop bugs from getting through to the intestinal tract.

“If the insult gets past that, the adaptive immune system comes into play and the white blood cells help fight the infection,” Marshall said. “We’re going to try to booster the effect of the white blood cells by giving vaccines.”

When lambs are born, they have some innate immunity.

“We booster that with colostrum,” Marshall said. “Good quality colostrum is really important for the transfer of immunity.”

Checking the udders of ewes is important to make sure the lambs can get the colostrum.

“The colostrum will passively give some of the antibodies that the mom has already made before the lamb is able to make its own,” Marshall said. “The sooner the lamb gets up and nurses, the better.”

Shepherds can use a Brix refractometer to check the quality of colostrum.

“It has a color-coded screen and it shows the amount of antibodies in the colostrum,” Marshall said. “The higher the number, the better the colostrum.”

Immunity the lamb absorbs from the colostrum will last for the first month of so after the lamb is born.

“Then there will be bugs and things that the lamb picks up that will start to challenge its immune system,” Marshall said.

“Vaccinating the lambs at the 6- to 8-week mark is when you should start to get good responses to the vaccines,” she said. “If you know the lamb did not get good colostrum, you can vaccinate them in the first couple of weeks.”

It is important, the veterinarian said, to vaccinate healthy animals to get a good response.

“Check the label because there’s many products and you need to make sure you give the number of doses necessary,” Marshall said.

“There are lots of vaccines available and they may not all be necessary on your farm,” she said. “You should test what diseases are on your farm.”

Vaccinations may vary depending on the farm goals.

“People that are showing sheep are at risk for exposure to diseases from other farms,” Marshall said. “If you have a closed herd, then your risk for disease will be a lot less than someone who is taking animals off the farm or bringing in new animals.”

Shepherds should be using the appropriate size of needle for giving vaccines and making sure they are following quality assurance guidelines.

“All products under the skin should be given in the neck region,” Marshall said.

“In general, for farms around here the minimum vaccine is for clostridial diseases,” she said, “particularly tetanus and overeating because they are easy to protect against.”

Don’t vaccinate for orf, the veterinarian said, unless it is a problem in the flock.

“I only use it on farms that have issues to help reduce the severity of the lesions,” Marshall said.

“Instead of injecting the vaccine under the skin, you scratch the skin and put a drop of the vaccine on the scratch,” she said. “It is something that can infect people so be careful that you don’t scratch yourself and make sure you’re wearing gloves.”

Maintaining the cold chain for vaccines is vital.

“I recommend you get vaccines direct shipped to you or from your veterinarian to make sure they stay cold,” Marshall said. “If they warm up, they won’t work.”

Avoid shaking the vaccines too much, the veterinarian said, because that can damage the antigens.

“So, just gentle shaking or rocking is better,” she said.

Vaccines that come with two vials that must be mixed together are usually live vaccines.

“Once you mix those two together, they’re really only good for less than one hour,” Marshall said. “So, if you’re vaccinating a lot of sheep, mix up only what you can use during that timeframe.”

Cache Valley Virus was first found in the 1950s in Utah and it is spread by mosquitoes.

“We’re starting to see a few cases around here,” Marshall said.

All kinds of birth defects and abnormalities depending on when the female was exposed have been associated with this virus.

“Typically, they’ll have twisted legs, abnormal eye development or there will be abortions,” Marshall said.

“Most of the abnormalities happen early in gestation when the embryo is forming, somewhere between 28 to 48 days,” she said.

“Human health risk is rare from the virus,” Marshall said. “But a lot of diseases that cause abortions can affect us, so wear gloves and don’t get any birth fluids in your mouth or face.”

“There’s no substitute for good management like nutrition, ventilation and sanitation to prevent diseases,” she said. “Those will be as important or more important for protecting the animal.”

Biosecurity is another important factor.

“If you’re bringing in new animals, know their vaccination status and quarantine them until you can get them to the same vaccine status as your herd,” Marshall said.