Lawsonia intracellularis infection in horses: 2005-2007.
BACKGROUND
Lawsonia intracellularis is an emerging equine pathogen that is a cause of equine proliferative enteropathy (EPE).


OBJECTIVE
To describe the signalment, month of presentation, common clinical signs, clinicopathologic values, diagnostic tests used, antimicrobial use, and survival status in horses affected with EPE; to evaluate how affected horses sold at public auction as yearlings; and to determine results of fecal polymerase chain reaction (PCR) and serum immunoperoxidase monolayer assay (IPMA) results in age matched, clinically normal herdmates.


METHODS
The study group was 57 horses treated for disease associated with L. intracellularis infection between August 2005 and January 2007.


METHODS
Retrospective study examined horses exhibiting evidence of infection with L. intracellularis and testing positive for fecal PCR or serum IPMA.


RESULTS
Horses ranged in age from 2 to 8 months with a median age of 6 months, and all were examined between August and January. Ventral edema was present in 81% of horses and hypoalbuminemia occurred in all horses. Only 50% of horses tested positive on both PCR and IPMA. Ninety-three percent of horses survived, and survival was unrelated to antimicrobial administered. Affected horses sold as yearlings an average of 68% less than other yearlings by the same sire. Age matched, clinically normal herdmates also tested positive for L. intracellularis on fecal PCR (6%) and IPMA (33%).


CONCLUSIONS
L. intracellularis infection should be considered in young horses with ventral edema and hypoalbuminemia that are examined between August and January. Both fecal PCR and serum IPMA are needed to help determine disease status. Treated animals usually survive, although they do not sell for as high a price at public auction as other yearlings by the same sire. Age matched, clinically normal herdmates also test positive for L. intracellularis on fecal PCR and serum IPMA.
Frazer
M L
ML
Hagyard Equine Medical Institute, Lexington, KY, USA. mfrazer@hagyard.com
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001803:Blood Transfusion / Q000662:veterinary; D002701:Chloramphenicol / Q000627:therapeutic use; D017291:Clarithromycin / Q000627:therapeutic use; D003102:Colloids / Q000627:therapeutic use; D045824:Desulfovibrionaceae Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy / Q000382:microbiology*; D006736:Horses; D006895:Hydroxyethyl Starch Derivatives / Q000627:therapeutic use; D020639:Lawsonia Bacteria; D008297:Male; D008795:Metronidazole / Q000627:therapeutic use; D010118:Oxytetracycline / Q000627:therapeutic use; D012189:Retrospective Studies
D000900:Anti-Bacterial Agents; D003102:Colloids; D006895:Hydroxyethyl Starch Derivatives; D008795:Metronidazole; D002701:Chloramphenicol; D017291:Clarithromycin; D010118:Oxytetracycline