The Horse

MAR 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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YOUR GUIDE TO THE 2018 AAEP CONVENTION A10 March 2019 The Horse | AAEP Wrap-Up TheHorse.com/AAEP2018 EPM or wobbler syndrome (the latter not caused by an infection), the team found, as expected, that significantly more EPM cases were positive for S. neurona than wobbler cases. However, instances of N. hughesi and T. gondii were not significant- ly higher in EPM cases than in wobbler cases. The results "do not support a role for polyparasitism in EPM," MacKay said. Vaccine for IBH A Swiss research group tested an immunotherapy vaccine for insect bite hy- persensitivity (IBH, aka "sweet itch") us- ing Icelandic horses, which are genetically predisposed to the condition. Results from the two-year study, which used a skin lesion scoring system, showed 47% and 21% of horses getting an IL-5 (an immune system protein responsible for releasing white blood cells) vaccine improved by at least 50% and 75%, respectively. The second year of vaccination offered even better protection, said MacKay. Horses in the placebo-treated group showed mark- edly less improvement. MacKay noted that this vaccine could offer an inexpensive and easy way to make IBH horses more comfortable. Ceftiofur Sodium and Pregnancy Turner reported that researchers from Florida, Georgia, and Kentucky evalu- ated the pharmacokinetics (how the body processes and maintains drugs) of the broad-spectrum antibiotic ceftiofur sodium (Naxcel) in pregnant mares to see if it might be an effective placentitis (placental inflammation) treatment. They administered intramuscular ceft- iofur sodium to 11 pregnant study ponies daily, measured drug levels in their blood plasma, and took placental fluid samples. They found that plasma levels were the same in the pregnant mares and non- pregnant horses but detected no ceftiofur sodium in placental fluid during gestation or in placental fluid or tissues immedi- ately after foaling. Their take-home? Ceftiofur sodium does not cross the fetal membranes and is not a good option for treating placentitis. Two Noninvasive Treatments for Oviduct Blockage in Mares Turner compared two studies in which researchers evaluated noninvasive treatments for subfertile mares suspected of having blocked oviducts. In the first study Japanese researchers evaluated the efficacy of hysteroscopic hydrotubation of the oviduct (passing an endoscope into the uterus, catheterizing the uterine tube, and flushing it with saline) and found that 26 of the 28 (93%) study mares be- came pregnant after treatment. In the second study researchers in Brazil tested topical administration of the drug misoprostol (a form of prostaglan- din E that can cause the oviduct to dilate and increase contractions) through the cervix into the uterus. They reported a 73% pregnancy rate in 22 treated mares. "Now we have two noninvasive, less ex- pensive, apparently effective treatments," said Turner. Length of Estrus Affects Recipient Mare Pregnancy Rates Researchers have previously shown that longer estrous periods are associated with increased pregnancy rates, but it was unclear whether this was due to an effect on the oocyte, the oviduct, the uterus, or some combination of these. Dutch scientists wanted to find the mechanism by which estrous duration affects pregnancy rates and early embry- onic loss. They went about this by de- termining whether a longer estrus has a positive effect on the ability of the uterus, specifically, to support early pregnancy. They looked at pregnancy rates in embryo transfer recipient mares, so they could eliminate the oocyte and oviduct from the equation (the recipient mare only provides the uterine environment). Endometrial edema (an increase in fluid in the tissues lining the uterus) is a hallmark of estrus and a normal response to high levels of circulating estrogen and low levels of progesterone. The researchers found that recipient mares with significant uterine edema for at least three days prior to ovulating had an 83% pregnancy rate following embryo transfer. Mares with fewer than three days of edema had a 64% pregnancy rate, and those with none had a 50% rate. The authors concluded that adequate estrogen priming during estrus is key to uterine receptivity and embryo survival. "Mares that ovulate quickly and show the development of little to no uterine edema prior to ovulation are less likely to become pregnant, and this is due, at least in part, to an effect on the uterine environment," said Turner. Colic Surgery & Broodmare Careers Large colon volvulus (twisting) is one of the most common postpartum problems in mares and is a surgical emergency, said Turner. To measure its fu- ture impact, researchers from Colorado, Kentucky, and Michigan looked at the long-term reproductive careers of brood- mares that underwent surgery to correct this type of colic. In their retrospective study they found that 82% of mares bred post-surgery produced at least one foal. Forty-seven percent foaled in the year fol- lowing volvulus surgery. Younger mares (ages 3 to 11) produced more foals after surgery than did older mares. The authors concluded that large colon volvulus surgery does not affect brood- mare careers. h ISTOCK.COM Researchers studied an IBH vaccine's efficacy in genetically predisposed Icelandic horses. ONLINE extras Visit TheHorse.com/AAEP2018 ■ Top Medicine Studies of 2018, TheHorse.com/166182 ■ Top Surgery and Lameness Studies of 2018, TheHorse.com/165082 ■ Top Reproduction Studies of 2018, TheHorse.com/166184

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