rhodococcus equi in foals

14
James Montgomery, DVM September 8, 2008

Upload: keiki

Post on 18-Jan-2016

105 views

Category:

Documents


2 download

DESCRIPTION

Rhodococcus equi in foals. James Montgomery, DVM September 8, 2008. Rhodococcus equi. Gram-positive aerobic rod Facultative intracellular pathogen Helps it hide from the immune system Foals have an immature immune system Opportunistic pathogen in immunocompromised humans - HIV. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Rhodococcus equi  in foals

James Montgomery, DVMSeptember 8, 2008

Page 2: Rhodococcus equi  in foals

Gram-positive aerobic rod

Facultative intracellular pathogen• Helps it hide from the

immune system• Foals have an immature

immune system Opportunistic

pathogen in immunocompromised humans - HIV http://www.cvm.tamu.edu/acvp/Rhodococcus/Rhodococcus.htm

Page 3: Rhodococcus equi  in foals

Saprophytic inhabitant of soil Widespread in the environment of

most horse farms Clinical disease ranges from

unrecognized or sporadic on some farms to enzootic and devastating on others• Morbidity rates as high as 40%

Page 4: Rhodococcus equi  in foals

Methods for control and prevention not well understood

No effective vaccines available presently

Administration of R. equi hyperimmune plasma has been shown to be effective prophylactically

Page 5: Rhodococcus equi  in foals

Foals between 3 weeks and 5 months of age

http://www.ca.uky.edu/gluck/ResearchDVS.asp

Page 6: Rhodococcus equi  in foals

Most common: chronic suppurative bronchopneumonia with extensive abscessation• Early clinical diagnosis difficult – slow progression

and foals able to compensate well

Early clinical signs: • Mild fever• Slight increase in respiratory rate

With progression:• Decreased appetite, lethargy, fever, tachypnea, and

labored breathing (nostril flaring, and increased abdominal effort)

Page 7: Rhodococcus equi  in foals

Inhalation is major route of pneumonic infection

Incubation period• Experimentally: 9 days with heavy inoculum

to approximately 2 to 4 weeks when lower inoculum administered

Page 8: Rhodococcus equi  in foals

CBC, fibrinogen• Used for monitoring

Transtracheal wash• Isolate R. equi

Radiographs Ultrasound

Page 9: Rhodococcus equi  in foals

Useful in evaluating the severity of pneumonia and in assessing response to therapy

Should not be used as sole criterion for prognostication and euthanasia

Prominent alveolar pattern characterized by ill-defined regional consolidation

Consolidated lesions are often more discrete nodular and cavitary• Consistent with pulmonary

abscessationLamb, 1990

Page 10: Rhodococcus equi  in foals

In foals < 4 months: nodular lung lesions and tracheobronchial lymphadenopathy is highly suggestive of R. equi infections

In foals 4 months or older, Streptococcus zooepidemicus is another common cause of lung abscesses

http://www.ca.uky.edu/gluck/ResearchDVS.asp

Page 11: Rhodococcus equi  in foals

Early lesions may be nonspecific irregularities of the pleural surface

In more chronic cases may see well-circumscribed, encapsulated abscesses

Very useful for evaluating severity of pneumonia and assessing response to therapy – especially if no access to thoracic radiography

Ramirez, 2004

Page 12: Rhodococcus equi  in foals

Pulmonary consolidation

Pulmonary bronchi give lung a liver-like appearance

Hyperechoic margin indicative of air in adjacent lung

Page 13: Rhodococcus equi  in foals

Slovis, 2005• Thoracic ultrasonography performed on foals on R. equi

endemic farms beginning at 30 days of age and repeated at 2 week intervals until weaned (16-20 weeks)

• Grading scale 0 (no evidence of pulmonary consolidation) to 10 (entire lung affected)

All foals with a graded pulmonary lesion were placed on antibiotics:• Azithromycin (10 mg/kg, q 24 h, PO for 7 days and then every

other day)• Rifampin (5 mg/kg, q 12 h, PO)• Treatments continued until ultrsonographic resolution was

determined

Farms that implemented thoracic ultrasonographic monitoring had no mortalities, and a marked reduction of clinical disease

Page 14: Rhodococcus equi  in foals

Giguère S. Rhodococcus equi infections. In Smith BP, ed. Large Animal Internal Medicine, 4th ed (St. Louis, MO: Mosby Elsevier, 2009) pp. 510-20.

Lamb CR, O’Callaghan MW, Paradis MR. Thoracic radiography in the neonatal foal: A preliminary report. Vet Radiol Ultrasound 1990; 31: 11-6.

Ramirez S, Lester GD, Roberts GR. Diagnostic contribution of thoracic ultrasonography in 17 foals with Rhodococcus equi pneumonia. Vet Radiol Ultrasound 2004; 45: 172-6.

Slovis NM, McCracken JL, Mundy G. How to use thoracic ultrasound to screen foals for Rhodococcus equi at affected farms. AAEP Proceedings 2005; 51: 274-8.