Enterococcus hirae-associated endocarditis outbreaks in broiler flocks: clinical and pathological characteristics and molecular epidemiology.
BACKGROUND
Enterococcus hirae-associated endocarditis, characterized by a peak in mortality during the second week of the grow-out, and occasionally lameness, was diagnosed at Dutch broiler farms.


OBJECTIVE
Field cases were studied to increase knowledge on clinical and pathological characteristics, pathogenesis and epidemiology of these infections.


METHODS
In total, 1266 birds of 25 flocks from 12 farms were examined. Post-mortem examinations, bacteriology, histopathology, PCR and DNA fingerprinting was carried out. Six flocks were followed longitudinally (n = 1017 birds).


RESULTS
Average mortality was 4.1% for the entire grow-out, of which 36% was attributed to endocarditis. Fibrinous thromboendocarditis of the right atrioventricular (AV) valve was found in 24% of hearts, compared to 7% and 4% with lesions of left and both AV valves, respectively. Thrombotic lesions were found in 24% (n = 432) of lungs, but only in larger branches of the Arteria pulmonalis. Occasionally, thrombi were found in the Arteria ischiadica externa and in liver and brain vessels. Enterococcus was cultured from 54% (n = 176) of heart and in 75% (n = 28), 62% (n = 106) and 31% (n = 16) of liver, bone marrow and lung samples, respectively. Further identification, using the Rapid ID Strep 32 API system and a PCR targeting mur-2 and mur-2(ed) genes was carried out on a subset of Enterococcus positive isolates (n = 65): both techniques identified the isolates as Enterococcus hirae. Pulsed-field gel electrophoresis did not indicate evidence of clonality between farms and flocks.


CONCLUSIONS
The relevance of these findings for pathogenesis and epidemiology of E. hirae infections is discussed. CLINICAL IMPORTANCE. This study may facilitate diagnosis of field cases and may contribute to the design of further research and development of control measures.
Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands. f.c.velkers@uu.nl
F C
FC
Velkers
L
L
van de Graaf-Bloois
J A
JA
Wagenaar
S T
ST
Westendorp
M A P
MA
van Bergen
R M
RM
Dwars
W J M
WJ
Landman
D000822:Animal Husbandry; D000818:Animals; D001344:Autopsy / Q000662:veterinary; D002645:Chickens; D004196:Disease Outbreaks / Q000662:veterinary; D004696:Endocarditis / Q000453:epidemiology / Q000473:pathology / Q000662:veterinary*; D016983:Enterococcus / Q000235:genetics / Q000302:isolation & purification*; D005260:Female; D005838:Genotype; D007668:Kidney / Q000382:microbiology / Q000473:pathology; D008099:Liver / Q000382:microbiology / Q000473:pathology; D016015:Logistic Models; D008168:Lung / Q000382:microbiology / Q000473:pathology; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D016133:Polymerase Chain Reaction; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology* / Q000473:pathology