Equine GI / Diarrhea PCR Panel

Test code: P0015

Test name: Equine GI / diarrhea PCR panel

This panel includes qualitative detection and differentiation of:

Diarrhea in adult horses can be acute (<1 month) or chronic (>1 month). Causes of acute diarrhea in horses include Salmonella, Ehrlichia risticii, Clostridium difficile and Lawsonia intracellularis. An acute, fatal diarrheal disease of unknown etiology is known as colitis. Chronic diarrhea is often not due to microbial infection.

Salmonellosis is the most commonly diagnosed infectious cause of diarrhea in adult horses. Many infected horses are subclinical and become carriers of the pathogen. The disease most commonly occurs sporadically but may become epizootic depending on the virulence of the organism, level of exposure, and host factors. Infection usually occurs via contamination of feed or water or by contact with animals actively shedding the bacteria. Other factors such as stress due to surgery, transportation or change in feed can play an important role in pathogenesis. GI disorders (colic) and treatment with broad-spectrum antimicrobial drugs can also lead to diarrhea. Salmonella typhimurium (group B), S. agona (group B), S. anatum (group B), S. newport (group C), and S. krefeld (group E) are the most common serotypes associated with diarrhea in adult horses.

Potomac horse fever is an acute diarrheal syndrome caused by Ehrlichia risticii. Horses suffering from this disease may develop lethargy, anorexia, fever, mucous membrane injection, ileus, colic, diarrhea, and laminitis. Any combination of these signs may be present but only rarely will a horse develop all symptoms together. Colitis is present in all cases but diarrhea only develops in <60% of affected horses.

Clostridium difficile is a strictly anaerobic, spore-forming bacterium that is a frequent cause of gastrointestinal disease in humans, horses, and pigs. Nosocomial diarrhea due to C. difficile has been reported in humans and horses and is often associated with administration of antimicrobials, but non-antimicrobial associated cases also occur. In the past, diagnosis of C. difficile involvement in diarrhea relied on both anaerobic culture of the organism from feces and demonstration of the presence of toxins A and/or B in fecal material; with toxin production differentiating the pathogenic and non-pathogenic strains of the organism. However, culture is difficult due to the fastidious nature of C. difficile and frequent overgrowth by other enteric bacteria. The cell cytotoxin test was considered a "gold standard" for identification of C. difficile toxins, but its turnaround time is slow. PCR detection of the toxin-producing genes sidesteps both the slowness of direct cytotoxin detection and the difficulty of culturing C. difficile. Thus PCR is a specific, sensitive and fast technique for detection of this bacterium.

Lawsonia intracellularis is the causative agent of proliferative enteropathy (PE) or ileitis in horses, swine and other domestic animals. This agent causes proliferation of intestinal cells, resulting in enteric disease which is sometimes fatal. The disease is responsible for serious economic loss to animal production worldwide. L. intracellularis is an obligate intracellular bacterium. Animals suffering from chronic PE may have clinical or sub-clinical effects on weight gain, feed conversion and fecal consistency. Diarrhea is a common symptom. Besides culture detection, which is slow, insensitive and difficult, some immunofluorescence tests using a monoclonal antibody directly on feces have been described, but this method lacks sensitivity. Diagnosis can also be based on histological examination of clinically affected necropsy samples. Currently no serological test is available for detection of L. intracellularis. PCR is a useful detection technique for L. intracellularis in both tissue and fecal specimens.

Although the etiology of <50% of cases of diarrhea in horses can be determined, treatment of most horses and foals with diarrhea is similar. Thus therapeutic management is possible despite a lack of a definitive diagnosis. It is however important to identify the causes of diarrhea so as to prevent further outbreak.

PCR detection of pathogens included in this panel offers a useful technique for quick, sensitive and specific identification of the disease-causing agent. The ability to detect multiple pathogens from one specimen minimizes the inconvenience and cost of collecting, handling and shipping multiple specimens.

Utilities:

• Confirm the pathogen causing GI symptoms and diarrhea
• Selection of appropriate treatment regimen
• Shorten the time required to confirm a clinical diagnosis
• Ensure that horse populations are free of listed GI pathogens
• Early prevention of spread of listed GI pathogens
• Minimize personnel exposure to listed GI pathogens
• Safety monitoring of biological products that derive from horses

Specimen requirements: Rectal swab, 1 ml feces or bacterial culture, shipped overnight at room temperature.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 3 business days

Methodology: Qualitative PCR and qualitative real time PCR

Normal range: Nondetected