Comparison of concentrations of Rhodococcus equi and virulent R. equi in air of stables and paddocks on horse breeding farms in a temperate climate.
BACKGROUND
Rhodococcoccus equi is a significant cause of bronchopneumonia in foals worldwide. Infection of the lungs is believed to result from inhalation of virulent R. equi in dust from contaminated environments. A measure of infectious risk in an environment is the level of airborne contamination.


OBJECTIVE
To assess and compare the level of airborne virulent R. equi in paddocks and stables.


METHODS
Air samples were collected sequentially over the 2003 foaling season from the paddocks and stables on 3 Irish horse breeding farms affected by R. equi pneumonia. Colony blotting and DNA hybridisation techniques allowed quantitation of virulent R. equi.


RESULTS
The odds of detecting airborne virulent R. equi in stables were 173 times greater than in paddocks. The median airborne concentration of virulent R. equi was significantly higher (P < 0.001) in stables than in paddocks on all farms. These observations suggested that stables were high-risk areas for infection.


CONCLUSIONS
Our results indicate that contaminated stables are a significant risk factor in the epidemiology of R. equi pneumonia on horse-breeding farms in a temperate climate, such as in Ireland. Management strategies that improve the air hygiene of stables, through better ventilation, use of less fragile bedding material and the use of fogging agents to reduce the airborne concentration of virulent R. equi, may reduce the incidence and severity of R. equi pneumonia on farms.
Muscatello
G
G
Equine Infectious Disease Laboratory, School of Veterinary Science, The University of Melbourne, Victoria 3010, Australia.
Gerbaud
S
S
Kennedy
C
C
Gilkerson
J R
JR
Buckley
T
T
Klay
M
M
Leadon
D P
DP
Browning
G F
GF
D000193:Actinomycetales Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D000391:Air Microbiology; D000818:Animals; D000831:Animals, Newborn; D001947:Breeding; D002980:Climate; D005260:Female; D006734:Horse Diseases / Q000453:epidemiology / Q000382:microbiology; D006736:Horses; D006799:Housing, Animal / Q000592:standards*; D007494:Ireland; D008297:Male; D016929:Rhodococcus equi / Q000302:isolation & purification* / Q000472:pathogenicity; D012621:Seasons; D014774:Virulence