Document Type : Case Study
Authors
1
department of clinical science.university of tehran
2
Department of clinical Sciences, school of veterinary medicine,shiraz university,shiraz,iran
3
Doctor of Veterinary Mediciene Student, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
4
school of veterinary medicine, Islamic Azad University, Karaj, Iran
10.66224/ari.2026.372324.4066
Abstract
Tick-borne diseases like Theileria equi and Anaplasma phagocytophilum pose a major threat to horses. Although both are present in Iran, confirmed co-infections are rarely documented, even though they can synergistically complicate clinical diagnosis. This report describes a rare, molecularly confirmed co-infection in a 4-year-old Thoroughbred mare from Aq-Qala, Golestan province, Northern Iran. The mare had a history of tick exposure in an endemic area during peak tick activity. Clinically, she presented with acute fever (39.3°C), tachycardia (45 beats/min), tachypnea (26 breaths/min), and pale mucous membranes, indicating hemolytic compromise. Despite clinical signs of anemia, automated hematological analysis revealed severe hemoconcentration (hematocrit: 63.4%; red blood cell count: 14.8×106/μL ) — a "masked anemia" phenomenon where dehydration and splenic contraction obscure the underlying hemolytic state — along with marked leukocytosis (23.6×103/μL) with a regenerative left shift (4% band neutrophils). Serum biochemical profiling further demonstrated severe hypoglycemia (33 mg/dl), hyperbilirubinemia (5.70 mg/dl), and significantly elevated activities of lactate dehydrogenase (953 U/l) and gamma-glutamyl transferase (186 U/l). Definitive diagnosis was achieved through conventional polymerase chain reaction (PCR) targeting the 18S and 16S rRNA genes, confirming simultaneous infection with T. equi and A. phagocytophilum. These findings highlight a "masked anemia" phenomenon, where severe dehydration and splenic contraction in response to acute infection and stress artificially inflated the circulating red cell mass, obscuring the underlying hemolytic stateThis case shows that in febrile horses from endemic areas, automated hematology alone is insufficient, and clinical examination should be supported by molecular diagnostics for accurate detection of co-infections.
Keywords
Main Subjects
)