Re: Mystery disease kills pigs in Southern China: press
UNDIAGNOSED DISEASE, PORCINE - CHINA (12): PORCINE REPRODUCTIVE &
RESPIRATORY DISEASE
*****************************************
A ProMED-mail post
<
http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<
http://www.isid.org>
Date: Fri 22 Jun 2007
Source: PLoS ONE [edited]
<
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1885284>
[The following paper, freely available online, has been published in
the June 2007 issue of PLoS (Public Library of Science) ONE
<WWW.PLOSONE.ORG>.
Tian K, Yu X, Zhao T, Feng Y, Cao Z, et al (2007): Emergence of Fatal
PRRSV Variants: Unparalleled Outbreaks of Atypical PRRS in China and
Molecular Dissection of the Unique Hallmark. PLoS ONE 2(6): e526.
DOI: 10.1371/journal.pone.0000526]
Summary
-------
Porcine reproductive and respiratory syndrome (PRRS) is a severe
viral disease in pigs, causing great economic losses worldwide each
year. The causative agent of the disease, PRRS virus (PRRSV), is a
member of the family _Arteriviridae_.
Here we report our investigation of the unparalleled large-scale
outbreaks of an originally unknown, but so-called "high fever"
disease in China in 2006, with the essence of PRRS, which spread to
more than 10 provinces (autonomous cities or regions) and affected
over 2 million pigs with about 400 000 fatal cases.
Different from the typical PRRS, numerous adult sows were also
infected by the "high fever" disease. This atypical PRRS pandemic was
initially identified as a hog cholera-like disease manifesting
neurological symptoms (such as shivering), high fever (40-42 deg C /
104-107.6 deg F), erythematous blanching rash, etc. Autopsies
combined with immunological analyses clearly showed that multiple
organs were infected by highly pathogenic PRRSVs with severe
pathological changes observed. Whole-genome analysis of the isolated
viruses revealed that these PRRSV isolates are grouped into Type II
and are highly homologous to HB-1, a Chinese strain of PRRSV (96.5
percent nucleotide identity). More importantly, we observed a unique
molecular hallmark in these viral isolates, namely a discontinuous
deletion of 30 amino acids in nonstructural protein 2 (NSP2). Taken
together, this is the 1st comprehensive report documenting the 2006
epidemic of atypical PRRS outbreak in China and identifying the 30
amino-acid deletion in NSP2, a novel determining factor for
virulence, which may be implicated in the high pathogenicity of
PRRSV, and will stimulate further study by using the infectious cDNA
clone technique.
--
Communicated by:
Les Sims
Asia Pacific Veterinary Information Services Pty Ltd
<
apvis@bigpond.net.au>
[This paper was also forwarded to us by Dr Peter Roeder, FAO (Food
and Agriculture Organization), who is cordially acknowledged.
The full list of authors and their respective affiliations is:
Kegong Tian(1), Xiuling Yu(1), Tiezhu Zhao(1), Youjun Feng(2,3), Zhen
Cao(1), Chuanbin Wang(1), Yan Hu(1), Xizhao Chen(1), Dongmei Hu(1),
Xinsheng Tian(2,3), Di Liu(2), Shuo Zhang(1), Xiaoyu Deng(1), Yinqiao
Ding(1), Lu Yang(1), Yunxia Zhang(1,4), Haixia Xiao(2,3), Mingming
Qiao(1,4), Bin Wang(1,4), Lili Hou(1,4), Xiaoying Wang(1), Xinyan
Yang(1), Liping Kang(1), Ming Sun(1), Ping Jin(1), Shujuan Wang(2,4),
Yoshihiro Kitamura(2,5), Jinghua Yan(2), George F. Gao(2,5).
1. China Animal Disease Control Center, Beijing, China
2. Center for Molecular Immunology, Institute of Microbiology,
Chinese Academy of Sciences, Beijing, China
3. Graduate University, Chinese Academy of Sciences, Beijing, China
4. College of Veterinary Medicine, China Agricultural University,
Beijing, China
5. China-Japan Joint Laboratory of Molecular Immunology and Molecular
Microbiology, Institute of Microbiology, Chinese Academy of Sciences,
Beijing, China
The paper includes a map of the affected provinces, pictures of
clinical and anatomo-pathological findings, and details of an
experimental infection trial that was done. The following copied
clause may help in assessing the initial confusions on the issue, as
reflected in the media:
"Initially, the "high fever" was suspected to be hog cholera or
African swine fever (ASF). The representative sick pigs had the
following common clinical symptoms: rubefaction, blood spots,
petechiae, erythematous blanching rashes, and pimples, frequently
observed in ears, mouth, noses, back, and the inner thigh. Other
common symptoms included high fever (40-42 deg C / 104-107.6 deg F),
depression, anorexia, cough, asthma, lameness, shivering, disorder in
the respiratory tract, and diarrhea. Infected pigs could be divided
into 2 groups: group one, which appeared fat and healthy; and group 2
with thin and debilitated features, ultimately leading to death. To
our surprise, many grown pigs also died during this epidemic period,
which is unlike the case for typical PRRSV infection.
"The disease course varied from 5 to 20 days. Infected pigs were
highly contagious, usually affecting the whole pig population within
3-5 days. The 1st pig death case was recorded on the 7th day
post-monitoring. The epidemic persisted for several months without
any obvious improvements, due partly to poor initial knowledge of the
etiological agent as well as the limited efficacy of the routine
treatments.
"Consequently, this large-scale outbreak of so-called "high fever"
disease has caused enormous economic losses, especially for pig
farmers. According to authoritative statistics from China Animal
Disease Control Center (CADC), this epidemic ended in September
[2006], affected about 2 120 000 pigs and claimed a death toll of no
less than 400 000 pigs, with an average death rate of 19.68 percent".
Regarding the laboratory infection trials, the paper provides the
following information:
"To reproduce what we observed in the field, laboratory infection
experiments were performed using 16 SPF-piglets (specific
pathogen-free). Three newly isolated PRRSV strains, termed JXA1,
HEB1, and HUB2, were used and they were isolated from dead pigs in
Jiangxi Province, Hebei Province, and Hubei Province, respectively.
One virulent strain (termed LB2) of PRRSV (collected in our
laboratory) was used for positive control. The viral titers of nasal
and injection challenge were 1.0 ml and 0.5 ml of virus culture (107
PFU/ml), respectively. Challenged pigs (4 piglets/group) were
monitored daily for clinical signs. Viral isolates were recovered
from those animals showing apparent clinical symptoms. Autopsies were
performed for further examination of the immunological effects and
pathological lesions".
-----
It would be helpful if further details on the experimental infection
trials become available, including the clinical and pathological
changes in the challenged piglets, in comparison to the positive
control and, in particular, to field observations.
It would also help to obtain details on the laboratory methods
applied to exclude CSF and ASF in the field-collected material.
The paper addresses the 2006 outbreak, stating that it was finished
by September (2006).
According to media reports and to a recent
notification of China's Vet Services to the OIE (World Organization
for Animal Health), the so-called "swine high fever disease" is
continuing its spread during 2007, causing heavy economical losses in
China. The paper above is a valuable step on the road to unfolding the
etiology. - Mod.AS]:tiphat:
http://www.promedmail.org/pls/prome..._BACK_PAGE,F2400_P1001_PUB_MAIL_ID:1000,38063
nly the last price was for 500g, others for 1kg)