The effect of bacterial dose and foal age at challenge on Rhodococcus equi infection.
Vet Microbiol
; 167(3-4): 623-31, 2013 Dec 27.
Article
in En
| MEDLINE
| ID: mdl-24139178
ABSTRACT
While Rhodococcus equi remains the most common cause of subacute or chronic granulomatous bronchopneumonia in foals, development of a relevant model to study R. equi infection has proven difficult. The objective of this study was to identify a challenge dose of R. equi that resulted in slow progressive disease, spontaneous regression of lung lesions and age-dependent susceptibility. Foals less than one-week of age were challenged intratracheally using either 10(6), 10(5), 10(4), 10(3) or 10(2) cfu of R. equi. Two doses (10(3) cfu and 10(5) cfu) were used to challenge 2 and 3-week-old, and 3 and 6-week-old foals, respectively. Physical examination, thoracic ultrasound and blood work were performed. Foals were euthanized at the end of the study or when clinical signs of pneumonia developed. All foals were necropsied and their lung lesions scored. Foals challenged with low concentrations of R. equi developed slow progressive pneumonia and approximately 50% of the foals recovered spontaneously. Likewise, macroscopic (>1cm diameter) pyogranulomatous lesions were only observed when low doses of R. equi were used. Clinical pneumonia was not seen after low dose challenge in the 3-week-old foals or in the 6-week-old foals. This study demonstrates that the use of low doses of R. equi to challenge neonatal foals provides an improved model for studying this disease. Furthermore, susceptibility to R. equi infection was shown to diminish early in the foal's life, as has been reported in the field.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Pneumonia
/
Actinomycetales Infections
/
Rhodococcus equi
/
Horse Diseases
Type of study:
Diagnostic_studies
/
Etiology_studies
/
Prognostic_studies
Limits:
Animals
Language:
En
Journal:
Vet Microbiol
Year:
2013
Document type:
Article
Affiliation country:
United States