title: Equine immune-mediated hemolytic anemia associated with Clostridium perfringens infection.
abstract: BACKGROUND
  Previous studies have suggested an association between equine immune-mediated hemolytic anemia and clostridial infections or neck abscesses.
  
  
  OBJECTIVE
  The purpose of this report was to describe and characterize the hematologic abnormalities in a horse with Clostridium-associated immune-mediated hemolytic anemia. We also retrospectively evaluated hematologic abnormalities in 8 horses with clostridial myositis or subcutaneous emphysema.
  
  
  METHODS
  A 7-year-old Foreign Warm-Blood gelding was evaluated for anemia and a cervical abscess. CBCs and reticulocyte counts were obtained using an Advia 120 analyzer and evaluation of Wright's-stained smears. All cases of equine Clostridium spp.myositis or subcutaneous emphysema over a 7-year period were identified in a retrospective search of the University of Minnesota Veterinary Teaching Hospital database. Clinical, hematologic, and microbiological findings were recorded.
  
  
  RESULTS
  Clostridium perfringens genotype A was isolated from the neck wound of the gelding. The CBC was characterized by severe regenerative anemia, intravascular hemolysis, and RBC agglutination. A direct Coombs' test was positive. Moderate numbers of spheroechinocytes were observed. The total automated reticulocyte count was 4.5% (56,700/microliter), with most reticulocytes having low absorbance (mature reticulocytes). The anemia responded to penicillin and steroidal and nonsteroidal immunosuppressive drugs. Of 8 horses with myositis, all of which involved the cervical region, 5 were anemic, 1 had a positive direct Coombs' test, and 2 had increased numbers of type III echinocytes and spheroechinocytes.
  
  
  CONCLUSIONS
  The presence of type III echinocytes or spheroechinocytes may be helpful in diagnosing immune-mediated hemolytic anemia associated with clostridial infections in horses. Automated reticulocyte counts may detect very low levels of reticulocytosis in hemolytic anemia in horses.
authors.affiliation: Department of Veterinary PathoBiology University of Minnesota, St. Paul, MN 55108, USA. weiss005@maroon.tc.umn.edu
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Weiss
authors.forename: Andreas
authors.initials: A
authors.lastname: Moritz
mesh_terms: D000038:Abscess / Q000150:complications / Q000382:microbiology / Q000662:veterinary; D000743:Anemia, Hemolytic / Q000150:complications* / Q000188:drug therapy / Q000276:immunology / Q000662:veterinary*; D000818:Animals; D003015:Clostridium Infections / Q000150:complications* / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D003016:Clostridium perfringens / Q000302:isolation & purification; D006734:Horse Diseases / Q000276:immunology / Q000382:microbiology* / Q000473:pathology*; D006736:Horses