Page 107 - January 2017

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A A n n o o t t h h e e r r i i s s r r o o t t a a v v i i r r u u s s , , w w h h i i c c h h c c a a u u s s e e s s d d i i a a r r r r h h e e a a i i n n y y o ou u n n g g f f o o a a l l s s . . W W h he e t t h he e r r o or r n no ot t y y o ou u v v a a c c c c i i n n a a t t e e t t h he e m m a a r r e e w w i i l l l l d d e e p p e e n n d d o o n n p p o o t t e e n n t t i i a a l l e e x x p p o o s s u u r r e e o o f f t t h h e e f f o o a a l l a a n n d d t t h h e e d d i i s s e e a a s s e e h h i i s s t t o o r r y y o o n n t t h h e e f f a a r r m m . .” ”
There are some other diseases that foals may be at risk for that have no vaccines available, including salmonella and clostridia infections in the GI tract. “If necessary, a foal could be given plasma after it’s born and some of these products might contain antibodies that may help prevent salmonella or clostridia.”
The history of the mare is important. Vaccination strategy would be different for an orphan foal that didn’t receive colostrum or
a foal from a mare that didn’t get vaccinated. This is something buyers might not think about when buying a weanling foal. They often ask about medical history in terms of whether it has been ill or injured, but don’t always ask if it has been vaccinated yet or if the mother was vac- cinated or if it received good colostrum.
VACCINATING FOALS
For optimum protection against foalhood diseases, it is very important that foals get adequate colostrum. “Ideally it should be from
a mare that has been well vaccinated. This gives the foal protection for roughly 6 to 8 weeks or more, and then the foal needs to make his own antibodies,” says Wilson. A foal starts producing his own antibodies from birth, but the immature immune system doesn’t work very well at first, needing several weeks to get up to speed.
The antibodies from colostrum generally last longer—to keep the foal protected during that start-up time for his own immune system—but are not as effective past 4 to 6 weeks. “Since they are still present in his body, however, they can actually interfere with vaccination if you vaccinate the foal too early. With a vaccine,
we are giving an antigen, which is usually an inactivated portion of the disease pathogen we are vaccinating against,” says Wilson.
To build immunity, the body must be able to recognize the antigen as a foreign invader and create antibodies against it. If the foal already
h h a a s s a a n n t t i i b b o o d d i i e e s s ( (o o b b t t a a i i n n e e d d f f r r o o m m c c o o l l o o s s t t r r u u m m ) ), , t t h h e e
i i n n t t h h a a t t t t h h e e m m a a t t e e r r n n a a l l a a n n t t i i b b o o d d i i e e s s f f o o r r t t h h a a t t v v i i r r a a l l
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h o o t t h h e e r r d d i i s s e e a a s s e e s s . . F F o o r r t t h h e e i i n n f f l l u u e e n n z z a a v v a a c c c c i i n n a a t t i i o o n n , ,
w w e e r r e e a a l l l l y y p p r r e e f f e e r r t t o o n n o o t t v v a a c c c c i i n n a a t t e e f f o o a a l l s s a a h h e e a a d d o o f f 6 6 months of age (preferably 7 to 8 months of age for their first dose) if the dam was vaccinated. Recommendations for foal vaccinations do keep changing, as we learn more about their immune systems and responses to vaccine,” she explains.
It’s always a good idea to talk to your vet- erinarian about vaccination schedules for foals. “There is not really a set protocol for all situa- tions and all foals. A foal vaccination program really needs to be tailored to your own farm and circumstances and exposure to diseases. This would include any previous outbreaks of certain diseases. It’s wise to work with your veterinarian to figure out what’s best for the foals on your farm.”
Tetanus is always a concern since this disease can crop up any time, and the bacterial spores can be dormant for years in the soil. The tetanus vaccine is very reliable, creates a good immunity, and foals can be successfully vaccinated at a fairly young age.
“If the mare has unknown vaccination his- tory, or has not been vaccinated in the last 4 to 6 weeks of pregnancy, we generally move up our foal vaccinations to 3 to 4 months of age for the initial series, especially the diseases they would be at high risk for at an early age. For tetanus or botulism, you can give these vaccines to foals at 1 month of age. In a high risk situation, tetanus antitoxin can be given at birth,” says Wilson.
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c c i i n n e e a a n n d d e e l l i i m m i i n n a a t t e e i i t t a a n n d d w w o o n n ’ ’t t m m o o u u n n t t e e n n o o u u g g h h
i i m m m m u u n n e e r r e e s s p p o o n n s s e e t t o o c c r r e e a a t t e e m m o o r r e e a a n n t t i i b b o o d d i i e e s s . . T T h h e e foal won’t build his own protection. “This is called maternal antibody interference,” she says.
“Most foals, if they received enough colostrum from a vaccinated mare, generally don’t need to be vaccinated until they are 4 to 6 months of age. The actual age you start vaccinating a foal will depend on the vaccine, the foal’s circumstances, and risk of exposure to that disease—and perhaps when (or if) the mare was vaccinated,” she says.
There is no exact ideal time, but it’s important to avoid vaccinating during a time
of stress, such as right at weaning, or when being castrated. A stressed animal is less able to mount a good immune response to the vaccina- tion. “If you are going to castrate a young colt, it’s wise to start him on his tetanus vaccinations beforehand, for instance. Yet often people want to vaccinate, castrate and wean at the same time. It’s better to not do that,” says Wilson.
“It’s ideal to vaccinate before weaning to start the immune process ahead of that stressful time. Most vaccines require one or two boosters after the initial vaccination,” she says. The rec- ommended schedule for boosters (how far apart they should be) will be on the vaccine label and is also listed on the AAEP website under vac- cine guidelines and the chart for foals.
“Recommendations for influenza are a little bit different than for the other vaccines
Before castration, start the colt on tetanus vaccinations. Most people want to vaccinate, castrate and wean at the same time. It’s better to vaccinate ahead of that stressful time, however, as a stressed animal is less able to mount a good immune response to the vaccination.
SPEEDHORSE, January 2017 105
EQUINE HEALTH