Lawsonia intracellularis: getting inside the pathogenesis of proliferative enteropathy.

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.



Animals: 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%).



Conclusion: 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.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2008.0160.x

Lawsonia intracellularis infection in horses: 2005-2007.

Enteritis and colitis remain challenging and life-threatening diseases despite many recent advances. Successful treatment is largely dependent on early recognition and directed therapy, which is facilitated by obtaining a complete history and physical examination. A number of new therapies and methods of monitoring critically ill patients have become integral components of treatment success. The critical monitoring of equine foals and adults continues to be an exciting and emerging field.

Enteritis and Colitis in Horses

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2000.tb02289.x

Surgical and medical treatment of an Arabian filly with proliferative enteropathy caused by Lawsonia intracellularis

The focus of rapid diagnosis of infectious disease of horses in the last decade has shifted from the conventional laboratory techniques of antigen detection, microscopy, and culture to molecular diagnosis of infectious agents. Equine practitioners must be able to interpret the use, limitations, and results of molecular diagnostic techniques, as they are increasingly integrated into routine microbiology laboratory protocols. Polymerase chain reaction (PCR) is the best-known and most successfully implemented diagnostic molecular technology to date. It can detect slow-growing, difficult-to-cultivate, or uncultivatable microorganisms and can be used in situations in which clinical microbiology diagnostic procedures are inadequate, time-consuming, difficult, expensive, or hazardous to laboratory staff. Inherent technical limitations of PCR are present, but they are reduced in laboratories that use standardized protocols, conduct rigid validation protocols, and adhere to appropriate quality-control procedures. Improvements in PCR, especially probe-based real-time PCR, have broadened its diagnostic capabilities in clinical infectious diseases to complement and even surpass traditional methods in some situations. Furthermore, real-time PCR is capable of quantitation, allowing discrimination of clinically relevant infections characterized by pathogen replication and high pathogen loads from chronic latent infections. Automation of all components of PCR is now possible, which will decrease the risk of generating false-positive results due to contamination. The novel real-time PCR strategy and clinical applications in equine infectious diseases will be the subject of this review.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2006.tb02817.x

Real-time polymerase chain reaction: A novel molecular diagnostic tool for equine infectious diseases

Proliferative enteropathy (PE) is a transmissible enteric disease caused by Lawsonia intracellularis. An outbreak of equine PE was diagnosed in foals from 3 breeding farms. Most foals had been weaned prior to the appearance of clinical signs, which included depression, rapid and marked weight loss, subcutaneous oedema, diarrhoea and colic. Poor body condition with a rough haircoat and a potbellied appearance were common findings in affected foals. Respiratory tract infection, dermatitis and intestinal parasitism were also found in some foals. Haematological and plasma biochemical abnormalities included hypoproteinaemia, transient leucocytosis, anaemia and increased serum creatinine kinase concentration. Postmortem diagnosis of PE was confirmed on 4 foals based on the presence of characteristic intracellular bacteria within the apical cytoplasm of proliferating crypt epithelial cells of the intestinal mucosa, using silver stains, and by results of PCR analysis and immunohistochemistry. Antemortem diagnosis of equine PE was based on the clinical signs, hypoproteinaemia and the exclusion of common enteric infections. Faecal PCR analysis was positive for the presence of L. intracellularis in 6 of 18 foals tested while the serum of all 7 foals with PE serologically evaluated had antibodies against L. intracellularis. Most foals were treated with erythromycin estolate alone or combined with rifampin for a minimum of 21 days. Additional symptomatic treatments were administered when indicated. All but one foal treated with erythromycin survived the infection. This study indicates that equine PE should be included in the differential diagnosis of outbreaks of rapid weight loss, diarrhoea, colic and hypoproteinaemia in weanling foals.

J. Shapiro

Papers

Equine proliferative enteropathy: a cause of weight loss, colic, diarrhoea and hypoproteinaemia in foals on three breeding farms in Canada.