Association Between PRRSV ORF5 Genetic Distance and
Differences in Space, Time, Ownership and Animal Sources Among Commercial Pig
Herds. Transbound Emerg Dis. 2014 Aug 4. doi:
10.1111/tbed.12253. [Epub ahead of print]
Abstract
The
objective of this study was to investigate associations between genetic
distance of porcine reproductive and respiratory syndrome virus (PRRSV)
detected in Ontario swine herds, and the distance between the herds with
respect to space, time, ownership and animal sources. PRRSV sequence data
between September 2004 and August 2007 were obtained from the Animal Health
Laboratory of the University of Guelph. Geographical coordinates were obtained
from the Ontario Pork marketing board, and network information about ownership
and animal suppliers was obtained using a telephone interview. The matrices of
sequence, spatial, temporal and network distances were generated and were
analysed using the Mantel test, and using linear-mixed models with P-values
based on random permutations. A total of 438 PRRSV isolates from 329 premises
and 232 ownerships were originally included; 57 of the isolates were considered
vaccine type. The Mantel correlation test indicated that there was positive
correlation between sequence distance and geographic distance
(r = 0.11, P = 0.001), as well as sequence distance and
temporal distance (r = 0.03, P = 0.03), with similar
results reported after adjusting for the ownership distance. Mantel correlogram
suggested existence of spatial correlation up to ~30 km distance.
Multivariable linear-mixed model for association between genetic distance and
space-time distance was characterized by the three-way interaction among space,
time and ownership (P < 0.001). It suggested that positive
association between sequence similarity and spatial proximity exists in herds
under different ownerships, but its magnitude is very small. In contrast, for
pairs of herds under identical ownership, the spatial association was more
complex. This could be a consequence of interactions within ownerships, or
alternatively decisions made about sampling of herds for diagnostic purposes.
Of the networks evaluated, ownership (P < 0.001) and gilt supplier
(P < 0.001) showed the highest magnitude of association with
genetic distance and should be investigated further for their impact on disease
spread.
© 2014
Blackwell Verlag GmbH.
KEYWORDS:
ORF 5; PRRS virus; disease
spread; epidemiology; geographical correlation; swine
PMID:
25088908 [PubMed - as supplied by publisher]
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