Low Platelet Counts and Sick Foals: An Unlucky Combination

Low Platelet Counts and Sick Foals: An Unlucky Combination

Photo: Anne M. Eberhardt/The Horse

If only predicting survival in sick foals were as easy as shaking the Magic 8 Ball for an answer. Researchers have evaluated various measures to help owners make difficult decisions when caring for sick foals, including white blood cell counts, fibrinogen levels, and glucose and lactate concentrations, among others, but none have been as effective as practitioners would like. Most recently, a Colorado State University (CSU) team investigated the impact of platelet counts on foal survival.

Elsbeth Swain, DVM, Dipl. ACVIM, of CSU’s College of Veterinary Medicine & Biological Sciences, presented her research data at the 2016 American Association of Equine Practitioners Convention, held Dec. 3-7 in Orlando, Florida.

Swain explained that many hospitalized foals have low platelet counts, referred to as thrombocytopenia, associated with their illnesses. When this occurs, the foal’s blood doesn’t clot normally. This condition’s impact on overall survival, however, has historically been unclear.

Photo: Courtesy Dr. Emily Berryhill

Foals can show signs of thrombocytopenia and abnormal clotting ability, shown in both images.

Photo: Courtesy Dr. Diane Rhodes

To better understand the effects of thrombocytopenia’s, Swain and Gary Magdesian, DVM, Dipl. ACVIM, Dipl. ACVECC, ACVCP, of the University of California, Davis, School of Veterinary Medicine, reviewed data collected on 1,414 foals 14 days of age or younger at the university’s Veterinary Medical Teaching Hospital.

One hundred thirty-three (9.4%) of those foals were diagnosed with thrombocytopenia (platelet counts <100,000/microliter of blood). Only 64.7% of foals with thrombocytopenia survived, whereas 86.1% of the control foals (those not diagnosed with thrombocytopenia) survived.

“Despite the overall decreased survival rate within the thrombocytopenia population, the outcome was not associated with the severity of thrombocytopenia,” Swain said. “This is important because the foals with the lowest platelet counts were actually associated with a good prognosis relative to the other groups (mild, moderate, and moderate-severe thrombocytopenia). This appears counterintuitive, but these foals that had dramatically low platelet counts were less affected by sepsis compared to the other groups and more affected by a condition called alloimmune thrombocytopenia, which can be managed with treatment.”

Foals with thrombocytopenia suffered from a number of conditions, including septicemia (bacteria in the bloodstream), gastrointestinal disease, equine herpesvirus-1, and Tyzzer’s disease. The researchers suspected alloimmune destruction of the platelets in 9.8% of the 133 thrombocytopenic foals.

“These findings are important as a clinician, because a foal can appear markedly critical if it is unable to clot its blood normally, but if a diagnosis can be reached, even the most severely affected foals may be treated successfully,” Swain said. “Thrombocytopenia detection can be easily tested in a foal using routine bloodwork at the time an IgG is tested.”

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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