Pathogen test The PCR test detects the genome (DNA) of the Rhodococcus equi, the pathogen responsible for Pneumonia. Sample 1 nasopharyngeal swab - dry swab Turnaround time 2 to 5 working days What is Pneumonia? Rhodococcus equi, a Gram‐positive facultative intracellular pathogen, is one of the most common causes of pneumonia in foals. Rhodococcus equi is a very well recognized pathogen in horses – it is a common cause of pneumonia in foalsbetween the ages of 1-6 months, and infection is also sometimes associated with other problems such as diarrheas, swollen joints and abscesses in other parts of the body. The infection can be very difficult to treat because the bacteria are able to live inside white blood cells, which helps protect them from the body’s immune system, and because they often cause abscesses to form, which are difficult for antibiotics to penetrate. Rhodococcus equi infection in foals has been studied extensively, but there’s still a lot we don’t know how the body defends itself against this organism. Clinical signs The most common clinical manifestation of R. equi infections in foals is bronchopneumonia. Early clinical signs may only include a slight increase in respiratory rate and a mild fever. These subtle clinical signs are often either missed or ignored, allowing the condition to progress. As the disease progresses, clinical signs might include: • Decreased appetite • Lethargy • Fever • Tachypnea • Increased effort of breathing characterised by nostril flaring and increased abdominal effort Cough and bilateral nasal discharge are inconsistent finding. Because ultrasonographic screening for early detection has become routine practice at some farms endemic for pneumonia caused by R. equi (see below), the most frequently recognised form of R. equi infection at those farms is a subclinical form in which foals develop sonographic evidence of peripheral pulmonary consolidation or abscessation without necessarily manifesting clinical signs. Extrapulmonary manifestations of rhodococcal infections are common. Extrapulmonary disorders might occur concurrent with or independent of pneumonia. Abdominal lesions (see necropsy below) are present in approximately 50% of foals that die from infections caused by R. equi. However, the majority of foals with abdominal lesions do not show clinical signs of abdominal disease. Polysynovitis is present in approximately 25–30% of cases with clinical R. equi infections. In some foals, lameness might be the result of septic arthritis or, more commonly, osteomyelitis caused by R. equi. Uveitis is not uncommon and might result in blepharospasm, ocular discharge, and blindness in severely affected foals. Occasionally, R. equi can cause infections of a variety of other extrapulmonary tissues or organs. Although rare, clinical signs resulting from abdominal infection with R. equi might include fever, diarrhoea, weight loss or failure to thrive, and colic. Transmission Inhalation of virulent R. equi is the major route of pulmonary infection in foals. Ingestion of the organism is an important route of exposure, and likely of immunisation, but rarely leads to hematogenously acquired pneumonia unless a foal has multiple exposures to extremely large numbers of bacteria. Prevention In the absence of an effective vaccine, control and prevention of the disease at farms endemic for infections caused by R. equi have relied on passive immunisation and screening to promote earlier recognition of the disease. There are no isolation requirements for foals with this disease. Foals with pneumonia caused by R. equi shed higher numbers of R. equi in their feces than healthy foals or foals with subclinical lesions. Therefore, pneumonic foals might be an important source of contamination of the environment with virulent R. equi but there is no evidence that R. equi infection is contagious among foals and exposure to virulent R. equi is widespread in the environment of foals. Thus, currently no environmental management practice or biosecurity measure has sufficient evidence on which to base recommendations for controlling and preventing R. equi pneumonia. Zoonotic Potential R. equi can occasionally cause severe pulmonary or systemic infections in immunosuppressed people. Infections with R. equi are extremely rare and typically less severe in immunocompetent individuals.
