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Veterinarian gives deworming, vaccination recommendations for horse health

by Wyoming Livestock Roundup

“From the moment a horse is four to six weeks old, you should start deworming for ascarids.”
That’s according to Riverton veterinarian Gunda Gamble of G Bar G Veterinary Clinic.
She says it’s so important to deworm for ascarids, or roundworms, from early in a foal’s life because they eat any manure available to them.
“That’s supposed to happen, because that’s how they get bacteria in their gut,” she says of a foal’s establishment of gut flora from its dam. She adds that if a horse owner ends up with a bucket-fed foal, it’s important to add manure to the replacer to make sure they ingest enough.
According to Gamble, roundworms reach six to 12 inches long and cause blockage in the intestines, stretching them, and they also migrate from the intestines to the lungs.
“From there they travel up the trachea and are coughed out as larvae and re-swallowed back into the intestines,” she explains, cautioning that a horse that coughs may have an ascarid infection. “They can also cause liver problems as they travel through the system.”
However, she says ascarids are easily killed with ivermectin or Quest dewormer, adding that it should be used before a Panacur five-day treatment because ivermectin induces a slow kill.
“It will kill over a three to 12 hour period, so the roundworms will die and get passed out slowly,” she notes.
She says Panacur, which can be found in Safeguard blocks market for cattle, and ivermectin need to both be used to create a complete deworming program, because Panacur won’t kill bots or tapeworms.
Of bots, Gamble says they’re the yellow eggs laid on horses’ legs by big, slow-moving flies. Although they’re hard to remove, she says vinegar can work.
“From the eggs, they either hatch and crawl to the horse’s mouth, or a horse touching his legs will pick them up in his mouth,” she explains. “From there they penetrate through the gums and tongue and sit for a month, which is very irritating. Some blisters in the mouth aren’t always from hay.”
After that month, they emerge looking like a beetle and are swallowed into the stomach. “They attach with hooks to the lining in the stomach, and some horses can colic because of them,” she says. “But you can give the horse just two or three cc’s of ivermectin and they’ll die. You can breathe ivermectin at them and they die.”
Gamble says when she was in vet school in the mid-1990s tapeworms weren’t considered a problem. Now, because so many horse owners have been diligent in using ivermectin to deworm their horses, tapeworms are on the rise.
“If you have a certain balance of roundworms, you won’t have a lot of tapeworms. But, ivermectin has taken care of roundworms so now tapeworms are on the rise, which can cause impactions,” she explains, noting that the only thing that kills tapeworms is proziquanto, which is readily available for dogs, but Zimectrin Gold also contains it, as well as Quest. Gamble recommends using Zimectrin, because a horse can’t be overdosed, while Quest can kill young horses.
Making a note about dogs, she says in Wyoming dog owners don’t need to worry about heartworms, but should treat for roundworms and tapeworms. “I deworm four times a year, because I know my dogs eat carcasses,” she says, noting that carcasses are the primary way dogs get infected with worms, and that they can’t be infected through eating horse manure.
If giving wormer through an injection, Gamble says not to give it in the muscle of the neck, but rather in the chest in front of the shoulder.
“If you give a horse ivermectin in the neck they’ll develop a shot reaction 10 inches across and slough that skin,” she says, adding that a horse owner also should not give shots where the mane falls. “The neck has the ligaments that hold the head up, and has poor blood flow.”
She adds banamine injections should be given in the mouth or in the vein, but not in the muscle in the neck. She also says that bute does almost nothing for a horse, except in cases of chronic pain. “Banamine is a strong, profound painkiller. Horse owners should give banamine, then call a vet if they have a program,” she adds.
Moving on to annual vaccinations, Gamble says there are core vaccines and risk-based vaccines.
“One of the core vaccines is tetanus, as well as Eastern and Western encephalitis,” she says, adding that with encephalitis horses generally reach a temperature of 108 degrees and die.
Gamble recommends spring vaccinations that include encephalitis, West Nile and tetanus. In the fall she recommends vaccinating for influenza, through either a straight influenza shot or an influenza/rhinopneumonitis combination. She says the rhino shot is only good for 60 days and is not very effective, but she says it should be considered for foals, which can have problems with the disease.
“The most important vaccine next to tetanus is strangles,” says Gamble, recommending Pinnacle N, a vaccine administered through the nose. “They get a snotty nose, fever and are dumpy, and an adult horse should never be dumpy.”
Regarding vaccine combinations, Gamble’s opinion is that four- or five-way shots combine too many vaccines into one cc.
“That’s a lot of stress on one lymph node, and it’s best to split them up, with a shot on each side of the neck,” she says.
Of rabies and West Nile vaccination, she says rabies isn’t a big deal in horses, and in the last year there were only two cases of West Nile in horses in Wyoming. “The incidents have plummeted, and that’s probably due to vaccine history and horses getting tough,” she says.
Riverton veterinarian Gunda Gamble presented her horse health information at Fremont County Farm and Ranch Days in Riverton in early February. Christy Hemken is managing editor of the Wyoming Livestock Roundup and can be reached at

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