(Abstract). In: Program and abstracts
of the 29th Interscience Conference on Antimicrobial
Agents and Chemotherapy. Houston: American Society for
Microbiology, 1989:145). Additionally, an outbreak of
invasive infection due to
S. pneumoniae,
including cases of primary septicemia and meningitis
as well as pneumonia, was described in 12 inmates of
an overcrowded jail in Texas in 1989
ref.
All patients were male; their mean age was 30 (range:
19-53) years. 5 additional inmates with pneumonia had
S. pneumoniae isolated from sputum specimens.
All isolates from the 17 patients were serotype 12. 14
patients had underlying conditions including
alcoholism and intravenous-drug abuse, cirrhosis, and
asplenia. Only one inmate had been previously
immunized with pneumococcal vaccine. More recently, in
1998, an outbreak of multidrug-resistant pneumonia and
bacteremia was described among unvaccinated nursing
home residents
ref.
Pneumonia developed in 11 of 84 residents (13%), 3 of
whom died. Multidrug-resistant
S. pneumoniae,
serotype 23F, was isolated from blood and sputum from
7 of the 11 residents with pneumonia (64%) and from
nasopharyngeal specimens from 17 of the 74 residents
tested (23%) and 2 of the 69 employees tested (3%).
All the serotype 23F isolates were identical according
to pulsed-field gel electrophoresis. Recent use of
antibiotics was associated with both colonization (RR
= 2.3; IC
95 = 1.3 to 4.2) and disease (RR =
3.6; IC
95 = 1.2 to 10.8). Only 3 residents
(4%) had undergone pneumococcal vaccination. After
residents received pneumococcal vaccine and
prophylactic antibiotics, there were no additional
cases of pneumonia, and the rates of carriage
decreased substantially. Additionally, a 1996 outbreak
in a NY nursing home was discussed in ProMED
Epidemiology
: endemic in swine in most pig-rearing countries in
the world. Human infections are rare, with < 150
sporadic cases reported in the world literature
according to the UK Health Protection Agency, mainly
in countries and regions breeding pigs and eating pork
in Northern Europe and Southern Asia. The 1st-ever
recorded case was in Denmark in 1968. Though endemic
in swine, human infections are rare. And where they
have occurred, mortality rates have been < 10%. In
past literature, there have been 1 or 2 cases when
people died within 36 hours, but those were exceptions
rather than the rule.
- Germany : a carrier prevalence study was
reported to assess the amount of culture-positive
throats among workers in swine slaughterhouses and
processing plants. 7 of 132 workers (5.3%) were
found to have positive throats cultures with no
colonization in control individualsref.
- Thailand usually had < 20 known cases a year.
- In 1998, 25 cases of Streptococcus suis
type 2 infection were reported in Jiangsu, China
-- characterized by toxic shock-like illness or
meningitisref.
Zhonghua Yu Fang Yi Xue Za Zhi 2000; 34:150-2).
Identical strains were identified in local swineref.
S. suis (type not specified) may be the 2nd
most common cause of adult streptococcal
meningitis in Thailand. Single hospitals reviewed
8 (1993 to 1999)ref,
10 and 12 cases (1997 to 2002). Associated skin
and soft tissue infections were commonref.
25 cases were treated in 2 hospitals in Hong Kong
during 1984 to 1993ref.
30 cases of S. suis meningitis were
reported in the Netherlands during 1968 to 1984ref.
Additional cases have been reported in Greeceref,
Spainref,
Japan (S. suis type 2)ref,
Croatia (S. suis type 1) (Kopi J, Paradzik
MT, Pandak N: [Streptococcus suis infection, a
zoonosis we should have in mind--2 case reports].
Lijec Vjesn 2003; 125:134-7), Taiwanref,
Singaporeref,
the United Kingdomref,
Austriaref,
Belgiumref,
Canadaref,
Italyref,
New Zealandref,
Swedenref,
and Latin Americaref.
Cases in Germanyref,
Netherlandsref
and Franceref
have been acquired from wild boar. Occupational
seropositivity has been documented in New Zealandref
and the Netherlandsref.
S. suis infection is found in all
pig-raising countries, worldwide. Pigs develop
meningitis, arthritis, pneumonia, septicemia,
endocarditis, encephalitis, polyserositis, and
abscesses. The disease is not considered to be
highly infectious, and most outbreaks are limited
to the affected farms. Pig infection is not
notifiable on the national or international level.
Affected farms may suffer economic loss.
Vaccination and antibiotic therapy in pigs have
been used with varying success. The rarity of
human disease to date suggests that the outbreak
in China is due to a new strain of the bacterium.
Clinical features of S. suis type 2
infection in these case reports have included high
fever, malaise, nausea and vomiting -- followed by
meningitis, subcutaneous hemorrhage, multi-organ
failure (hepatic, renal, pulmonary, cardiac) and
coma in severe cases. Deafness is
common. Individual reports of peritonitis,
endocarditis, rhabdomyolysis, spondylodiscitis
, sacroilitis, monoarthritis, endophthalmitis
and cranial nerve palsy
are documented. Virtually all patients have been
farmers and butchers, of whom 80% were men. Most
had been involved in butchering sick pigs or
selling the pork. > 40% of the patients were in
the age group 50 to 60 years, and none were
children.
- China : the last outbreak of Streptococcus
suis in China was in 1998 (Jiangsu
province), and involved 22 people causing 14
deaths. But in 2005, ...
- in China's western Sichuan province
between 24 Jun and 30 Jul 2005 204 farmers
(44 laboratory-confirmed, 131 diagnosed at a
clinic, and 39 suspected) (80% males, >
40% aged between 50 and 60 years) from 108
villages of 40 different townships in 11
cities/prefectures (first in Ziyang (414
pigs affected and 2899 destroyed since 25 Jun)
and its neighboring city of Neijiang
(193 pigs affected and 3159 destroyed since 15
Jul), then Jianyang (9 pigs affected and
583 destroyed since 17 Jul), Zigong, Suining,
Deyang (5 pigs affected since 29 Jul : 66
destroyed), Luzhou (2 pigs affected
since 12 Jul : 7 destroyed), Mianyang (1
pig destroyed on 24 Jul), Nanchong (2
pigs affected and destroyed since 29 Jul), Yibin,
Leshan, and the provincial capital Chengdu
(15 pigs affected since 2 Aug : 19 destroyed)),
were admitted to hospital with high fever,
fatigue, nausea, and vomiting and became
comatose later with bruises under the skin. The
area has a population of 7 million, in a 100-km
(62-mile) belt stretching from the cities of
Ziyang to Neijiang. From 24 Jun through 21 Jul
2005, the authorities reported 20 cases of
illness of unknown cause admitted to 3 hospitals
in that city. WHO was officially informed of the
outbreak on 22 Jul 2005, at which time, 20 cases
and 9 deaths had been reported. By 22 Aug 2005,
40 patients had died, 58 had been
discharged from hospital, 117 are in hospita,
with 12 still in a critical condition. They all
butchered sick pigs or sheep before coming down
with the strange disease, but the detected cases
are not interrelated and no infection has been
found in any close contact of the patients.
There have been 36 counties (districts), 132
towns (streets), and 202 villages (community
offices) infected in areas. > 450 pigs
infected with Streptococcus suis were
burned in the area. 50 checkpoints are in place
to prevent swine from being moved around. No new
cases have been reported since 5 Aug 2005. The
data provided by China depict an outbreak that
peaked from the 2nd through the 4th week of Jul
2005, and dwindled rapidly thereafter
Transfer to humans is rare -- which makes the
Sichuan mortality rate alarming. In addition, this
province is China's largest pig center, producing
> 50 million swine annually. S.suis type
2 (B) was identified in 5 patients on 26
Jul. One differential diagnosis was CCHF
, first reported in China in
1964, and is known locally as Xinjiang hemorrhagic
fever. Cases are reported from the south west
region. 260 cases (54 fatal) were reported in
Xinjiang (southern desert region) during 1964 to
1995. 10 to 20% of sheep, goats, and cattle in
Sichuan are seropositive. This latter information
raises the index of suspicion that CCHF is a
likely candidate. While CCHF is usually thought of
as a tickborne disease, it can also be transmitted
through contact with infected bodily fluids from
people (in nosocomial outbreaks) and animals.
Another of the hemorrhagic fevers seen in the
region is hemorrhagic renal syndrome associated
with hantavirus infection. The description above
makes that diagnosis less likely, although one
must recognize that newswire descriptions may not
necessarily be representative of the actual
clinical picture. Some of the features of these
illnesses are not characteristic of avian
influenza; in particular, the unrelatedness of the
victims, the development of hemorrhagic symptoms
and shock, and the association with slaughter of
pigs and sheep. The one caution towards that being
the diagnosis is the lack of mention of that in
the press articles, as one would expect that
specimens have been sent for testing of previously
known hemorrhagic fever organisms. Virtually all
infection diseases begin with "flu-like" symptoms
and this cannot be taken as indicative of avian
influenza virus infection. Furthermore the role of
pigs as a mixing vessel allowing interactions
between human and avian influenza viruses is an
attractive hypothesis, but one that has still to
be substantiated. As of April, 23% of 450 Chinese
pigs tested were carrying a less virulent avian
flu strain : H9N2. If it is
the case that the porcine streptococcus is the
cause of these illnesses, perhaps the organism has
acquired one or more virulence factors (from, for
instance, the Group A streptococcus or Staphylococcus
aureus) to increase its transmissibility and
virulence in humans. It would be interesting to
assess any medical co-morbidities in the infected
cohort. The authorities have dismissed speculation
that the deaths were caused by bird flu, a virus
that has killed over 50 people in Asia since late
2003. Nevertheless, medical experts outside
mainland China said the unusually high mortality
rate of 20% and reports that many of the 27
victims died within a day of showing symptoms were
inconsistent with what is known so far about human
Streptococcus suis infection.
The deaths in China are very unusual. Many
patients in Sichuan were bleeding under the skin,
a symptom that has been cited in only 2 or 3 cases
in medical literature on the bacteria. According
to experts with the team sent by the Ministry of
Agriculture to the area of the outbreak, the
vaccines for Streptococcus suis type II, a
bacterium carried by pigs, will soon be
batch-produced in south China's Guangdong Province
and are expected to reach Sichuan Province in
about 1 week after being inspected by the Ministry
of Agriculture. Yongshun biomedical company in
Guangdong will be the first to mass-produce the
vaccines. The Chinese government responded on Sun
31 Aug 2005 by airlifting the 1st batch of a
vaccine for the infection -- enough to treat 360
000 pigs -- from the southern city of Guangzhou to
the affected towns. The vaccine's manufacturers
will be producing enough vaccine to treat 10
million pigs in the coming days, but vaccines take
3 weeks to produce immunity in the pigsref.
It is plausible that the organism (and possibly
toxin) load to which the patients were exposed was
higher if the swine had been dug up after being
buried, with the possibility of further S.
suis replication and toxin production while
buried. This could explain the different disease
observations, which have caused observers to be
somewhat unsure if the S. suis is indeed
the etiology. From the perspective of a researcher
in human streptococcal infection, this emergence
of Streptococcus suis infection in humans
resembles the outbreaks of group B streptococcal
infection that emerged in human neonates during
the 1970s and then in debilitated adults in the
1980s. Both instances remain unexplained. Indeed,
S. suisresembles group B streptococcus (S.
agalactiae) in many respects. Both are
encapsulated hemolytic streptococci that have
propensity to cause bacteremia and meningitis in
newborns after exposure to the organism in vaginal
secretions. Most newborns remain asymptomatically
colonized but in a minority progress serious
infection including sepsis, meningitis, pneumonia
and localized infections. Both organisms remain
susceptible to beta-lactam antibiotics and, in
humans, control of the infection has been largely
achieved by use of antibiotic prophylaxis of
maternal carriers of group B strep. during
childbirth. Diagnosis of S. suis infection
in both pigs and humans is based upon culture of
the organism from normally sterile sites and
should not be difficult. Clinical details from the
current outbreak (both from the pigs and the
humans) are thus far lacking and it is therefore
difficult to assess whether some co-infection (or
other co-morbidity) may be accounting for this
unprecedented cluster of human disease.
Inspectors swooped down on the unregistered
abattoir in the city of Gongzhuling in Jilin
province in the 1st week August 2005, and found it
had been supplying meat to a sausage factory in
the provincial capital, Changchun, which had also
been shut down. Inspectors found 6 to 8 tons of
pork in the underground slaughterhouse, and our
tests showed at least one ton came from pigs who
had died of illnessref.
Several aspects of the current outbreak still
remain unanswered. What are the morbidity and
mortality rates in pigs? Is there any differential
age susceptibility? What are the pathological and
histopathological changes? Are there any
performed/envisaged virological investigations
besides excluding influenza and Nipah? Have there
been any experimental infection trials in animals?
All these unanswered questions cloud the
perception of transparency in disease
reporting. At this point, might it not be
useful to have an international presence on
outbreak swine farms so that some of these
questions can be answered sooner rather than
later? Applying "stamping out" is an unusually
severe measure when related to a bacterium which
-- at least, according to existing knowledge -- is
rather endemic in many countries in piggeries. It
would be helpful to note how screening is to be
applied, and what criteria will be used for farms
to be "stamped out."
A circular has been issued by the Sichuan
Provincial Propaganda Department...which forbids
local press from sending reporters to the infected
areas or hospitals. No amendments of Xinhua
reports are allowed, including the headline:
Xinhua's is currently the only version of events
available to both Chinese and overseas reporters
alike. Please note that S. suis does not
spread from person-to-person. The symptoms of the
disease have led some experts to speculate that
Ebola virus could be the cause : the Chinese
Communist Party (CCP) has prohibited news
coverage, and has forbidden the use of the words
‘Ebola virus’ in reports, instead requiring the
use of alternate wording. Doctor Wang (?) said
that the virus sample specimen was examined as
soon as it was received and a type of Ebola virus
was extracted from the specimen. When asked why
“low dissemination” was added to the name of the
Ebola virus in China, Doctor Wang explained that
it was done to reduce public concern, and also
because a variation of the Ebola virus had
actually occurred in China. They started the
examination quickly after receiving the sample,
they extracted SZ77++A3231 virus from the
sample, which is a kind of Ebola virus. The
previous classification of Ebola in the country
used the EBO – location (where it was discovered)
– model; later on, for unknown reasons, the news
of classification leaked out. Therefore the
classification method changed, they abandoned EBO,
increasing the infection extent, infection speed,
etc. The disease that occurred at the beginning of
June is SZ77++A3231 virus, sometimes we do not
specify the source region but directly use
++A3231, so that people will not think of the
Ebola virus.” The CCP formed 3 departments
specifically to conduct these examinations, so
obviously Sichuan is not the only area to have
experienced the illness caused by the Ebola virus.
Many Mainland Chinese recognize that the current
mystery disease in Sichuan is the EB-SZ77 type
Ebola virus. The earliest occurrence of this Ebola
virus disease can be traced back to Shenzhen city
in Guangdong Province. On March 25, 2005, The
Epoch Times published an article on the
first appearance of the Ebola virus in Shenzhen
during February. The virus had already caused
several deaths and cases of ‘missing people’
[Editor’s note: rather than accurately reporting
the cause of death, the authorities simply claim
that victims are ‘missing’]. This article
mentioned that medical personnel who had been
working in hospitals for years said that they had
never seen an illness like it. The bodies of those
who died of the illness appeared to be dissolved,
much like the Ebola virus in Africa. The main
spread of the virus was through blood, causing
doctors to die after contact with infected blood.
On March 26, Shenzhen Customs and related
hospitals and government departments held a
confidential meeting to pass an order from higher
authorities to strengthen the hygiene-related
work. An insider also disclosed that at dawn on
March 26, another suspected Ebola virus death case
occurred in Nanao Town, Shenzhen. There are
indications that the Ebola virus was already
spreading in Mainland China. The CCP blocked this
information, telling the outside world that the
deaths were caused by the advanced stages of AIDS.
On March 29, China’s Ministry of Health announced
that, “Presently, this virus has not been found in
the mainland.” The source of the information
regarding the death case in Nanao Town couldn’t be
contacted further, and the company and hospitals
denied the existence of the Nanao Town case or any
existence of a patient record. All websites in
mainland China have now started using official
language to report this case. Although the
Ministry of Health said that Ebola virus has not
been found on the mainland, according to inside
information on July 14, frequent confidential
meetings were held by the Guangdong Province
government, Guangzhou military region, Shenzhen
municipal government and Shenzhen Customs during
late June and early July, discussing the slow
spread of the Ebola virus in Guangdong Province.
People were strictly prohibited from spreading
information about the Ebola virus and bird flu
that appeared in Guangdong and media reports were
also forbidden. Why don’t CCP officials allow the
WHO to investigate and provide help? Veterinary
pathology scholar Liu Zhenyi said that the CCP has
always flaunted its “greatness, honor, and
correctness”, and is most concerned about saving
face. This appears to be a higher priority than
people’s lives. Guan Yi, scholar and bird flu
expert at Hong Kong University disclosed in Nature
magazine that bird flu had infected southern
China. Chinese officials subsequently shut down
his laboratory, slandered him and said that his
laboratory was “illegal.” Doctor Wang, quoted
earlier, who examined this strange Sichuan
disease, also believes that the CCP would not
allow the involvement of the WHO because it would
be extremely disadvantageous for the international
image of the CCP. It wouldn’t be just a medical
question, but could lead to exposure on issues
such as the local medical environment, survival
conditions, environmental pollution and political
corruptionref.
A total of 647 pigs have died as a result of Streptococcus
suis infection in Sichuan province. The
deaths occurred in 149 villages of 88
municipalities in 21 counties of the following 8
regions: Chengdu, Deyang, Luzhou, Mianyang,
Nanchong, Neijiang, Zigong, Ziyang. The epizootic
began in late June 2005, reached a peak around 20
Jul, and then declined sharply. No new cases have
occurred since 6 August 2005. This epizootic was
caused by Streptococcus suis type 2. The
LD50 (dose lethal to 50% of the
animals) of the bacterial strain isolated in
Sichuan was determined using the new laboratory
animal model, zebra fish (pure breeding line), and
the virulence genes of the bacterium were also
tested. The results of the tests showed that the
virulence of the isolate is not significantly
different from that of isolates obtained from
other places in the past, and no evidence of
genetic variation has been found. The main
characteristics of the epizootic were as follows:
- 1.1. Spatial distribution : the outbreak
areas were mainly centralised in the
historical endemic areas of S. suis
infection in Ziyang, Neijiang, and other
places. The outbreaks occurred sporadically,
and did not occur densely over a large region.
Infected points were far apart and had no
direct epidemiological relationship. There is
therefore little likelihood of transmission
having occurred between them.
- 1.2. Temporal distribution : the disease was
first recognised on 24 Jun 2005, and mainly
occurred in July. During this period the
weather was hot, humid and rainy. The season
when the epizootic occurred was the same as in
the past. This shows that the occurrence of S.
suis infection in pigs is specific to a
particular season.
- 1.3. Herd distribution : all outbreaks
occurred in remote rural areas with poor
economic conditions, and only in small
backyard farms, where animal health conditions
are poor, and pigpens are dimly lit, damp and
inadequately ventilated. No outbreaks were
reported in intensive farms and large-scale
premises with better sanitary conditions. The
morbidity observed in pigs within each
affected group was low.
- 2. Control measures : the recent S. suis
epizootic was effectively controlled by
applying all of the following measures:
- - preventive treatment of pigs in the same
herd as infected and dead animals using
highly sensitive antimicrobials, and
improvement of resistance to the disease by
adding preventive medicine to animal feed;
- - regular disinfection of swine holdings
in infected places and zones, livestock
markets and designated slaughterhouses,
aimed at improving sanitary conditions;
- - destruction of cadavers of dead pigs by
deep burial;
- - stepping up of inspection and
quarantine, and movement control of animals
and animal products;
- - development and production of vaccine,
and emergency vaccination of pigs in
high-risk areas aimed at improving their
level of immunity.
- 3. Vaccination : pigs have been vaccinated
with Streptococcus suis type 2
vaccine.
In the regions of Ziyang, Neijiang and Zigong,
where highest morbidity was found, vaccination was
performed in all counties; in the other 5 regions,
vaccination was performed only in the infected
counties and in the zones at risk adjacent to
infected zones. No vaccination was performed in
pigs for slaughter within 20 days, one month old
piglets, pregnant sows, or weak pigs. To date,
about 14 million pigs have been vaccinated, and
the vaccination cover is up to 90%. Testing of
vaccinated pigs with indirect ELISA showed that
70% of pigs had a significant serum antibody titre
14 days after vaccination. The application of
vaccine in the field has demonstrated that Streptococcus
suis type 2 inactivated vaccine is
effective, safe and has few side effects. While
this report indicates all swine cases were
confined to 647 cases in Sichuan province, there
appear to have been human cases in Hong Kong. In
fact, the disease is recognized, rarely in
ig-producing areas worldwideref
- in Jiangsu province (in eastern China
and not at all geographically close to Sichuan)
: the 1st man (a butcher) to fall ill was
admitted to the hospital of Suzhou with a high
fever on 28 Jul 2005 and died on 2 Aug 2005. The
2nd case (a meat seller) was hospitalized on 2
Aug 2005 and died a few days later. In the
summer of 1998 (Jul and Aug), an epidemic of
deadly S. suis infection struck people
in Jiangsu, resulting in 14 deaths and > 80
000 dead pigs. The epidemiological investigation
and clinical description (including diagnosis,
microbiological confirmation and treatment) of
the epidemic were well-reported in Chinese
medical journals. The epidemiologic link of the
victims to dead or diseased pigs is similar to
that in the recent outbreak in Sichuan, and
cases were sporadic in occurrence and scattered
in geographic distribution. No point-source
outbreak or human-to-human transmission was
documented. In one of the reports, 25 persons
were affected and 14 died (overall mortality
rate 56%). 13 out of 16 persons who developed
streptococcal toxic shock syndrome (STSS) died
(crude mortality rate 81%). Of the 9 persons who
developed streptococcal meningitis, only 1 died
(crude mortality rate 11%). The clinical picture
is similar to that reported recently in Sichuan,
except that the Sichuan cases are now classified
into 4 categories, (1) ordinary type (milder
febrile illness with no shock or meningitis),
(2) STSS (with high mortality), (3) meningitis
(with high incidence of sensorineural deafness),
and (4) mixed type (with both STSS and
meningitis, and with high mortality). The
culprit was confirmed to be S. suis
serotype 2, the same as that which caused the
recent Sichuan outbreak. The epidemiologic links
are the same as those
identified in Sichuan. Thus, the disease occurring
in epidemic proportion is not new in China, but
may be new in the English or world medical
literature. One thing that is not clear up to this
moment is the extent of swine deaths in Sichuan.
In an official news report dated 5 Aug 2005, only
644 pigs were reported to have been killed by the
deadly bacterium in Sichuan as of 4 Aug 2005.
Readers may be interested to look up some of the
Chinese publications (with English abstracts) on
the Jiangsu outbreak:
- Zhang X, Ding J, Qin H: Clinical analysis of
22 cases of the disease contracted both by man
and pigs with swine streptococcus infections.
Journal of Tropical Medicine 2002; 2:361-3,
372.
- Ying H, Zhu F, Shi Z, et al: Isolation and
identification of streptococcus suis. Jiangsu
Preventive Medicine 2001; 12:9-10.
- Tang J, Zhu J, Guo H, et al: Epidemiological
and pathogenic study on the outbreak of toxic
shock syndrome and meningocephalitis caused by
swine streptococcus. Acta Academiae Medicinae
Militaris Tertiae 2001; 23:1292-5.
- Yang H, Zhu F, Shi Z, et al: Analysis on
pathogenic feature of syndrome infected by S.
suis from human and swine. Chinese Journal of
Zoonoses 2001; 17:92-3, 120.
- You Y, Shen J: The epidemiological study on
human streptococcal infections syndrome caused
by infected pigs. Chinese Primary Health Care
2001; 15:20-1.
- Zhu J, Tang J, Zhang Y, et al: Biological
characters and identification of the pathogen
contributing to the outbreaking epidemic toxic
shock like syndrome. Chin J Infect Dis 2001;
19:84-6.
- Zhu F, Yang H, Hu X, et al: Homogeneity
study on the Streptococcus suis isolated from
human and swine. Chin J Epidemiol
2000;21(6):427-9.
- Zhu J, Tang J, Guo H, et al. Epidemiologic
and pathogenic study on an outbreak of acute
streptococcal disease in pigs. J Prev Med Chin
PLA 2000; 18:257-60.
- Hu X, Zhu F, Wang H, et al Studies on human
streptococcal infectious syndrome caused by
infected pigs. Chin J Prev Med 2000; 34:150-2.
- Wang H, Hu X, Zhu F, et al: A
epidemiological study on the human
streptococcal infective syndrome among men and
pigs. Modern Preventive Medicine 2000;
27:312-4.
- in Guangdong province, which borders
Hong Kong and is hundreds of miles southeast of
Sichuan, 4 cases and 1 death occurred,
including :
- a 43-year-old slaughterhouse worker in
Chaozhou was affected on Jul 31 through a
wound on his hand as he slaughtered a sick
pig: he recovered and was discharged.
Investigators suggest the infected pigs came
from 300 small farms with poor sanitary
conditions.
- a man who has slaughtered pigs from
Yangjiang town died
- Chao'an County
- Nanxiong city
- Shenzhen city
No pigs were reported sickened by S. suis,
the bacteria blamed for the human cases
- in Hong Kong : in Kay's paper
published in 1995ref,
the authors mention a "small outbreak" of 38
cases between 1981 and 1983. These cases,
indeed most cases including the cases occurring
now, tend to present in the summer months. The
1981-83 cases appear to have occurred following
the importation of "10 000 live pigs per day
from neighboring China in hot and crowded
conditions." Small clusters, therefore,
appear to have occurred before but not to this
degree and generally linked to meningitis due to
this organism (Chau PY, Huang CY, Kay R: Streptococcus
suis meningitis: an important
underdiagnosed disease in Hong Kong. Med J Aust
1983; 1:414-17). From 1983 to 1994, there were
25 cases of human Streptococcus suis
infections in Hong Kong. In 1983, it was shown
that the virus was the leading cause of
meningitis in Hong Kongref
: in 2005 there were 12 cases including 2 deaths
(4 since the outbreak in China was 1st reported
in June 2005; related to the Sichuan outbreak ?
a 26-year-old interior decorator who has not
traveled to the mainland recently and has had no
contact with pigs was admitted to hospital 5 Jul
2005 and discharged a week later; a 78-year-old
woman resident of Mong Kok who had not left Hong
Kong came down with the infection on 3 Aug 2005
and was admitted to Kwong Wah Hospital in Mong
Kok with a fever and pain in her right hip on 8
Aug 2005; a 44-year-old butcher working at
Wellcome Supermarket admitted to the hospital on
Tue 16 Aug 2005 with fever and pain in his
finger and left thigh and is now in stable
condition; a 79-year-old woman resident at
Kowloon City developed fever, right knee pain,
redness and swelling on 16 Aug 2005, was
admitted to Queen Elizabeth Hospital and
confirmed on Mon, 22 Aug 2005; A 62-year-old
woman; a 43-year-old, who had no recent travel
history, was admitted to the hospital and
immediately died on 13 Oct 2005). Pork
contaminated with this organism was found
worldwide and as much as 50% of pork imported
from Holland, New Zealand and Australia bore the
bacterium. So far in 2005, Hong Kong has
imported > 18,000 tons of frozen pork from
Sichuan, of which 5000 tons came from the 2 most
affected cities -- Ziyang and Neijiang. On Mon 1
Aug 2005, the Hong Kong authorities said that,
to better monitor the situation, they would
classify Streptococcus suis as a
statutorily notifiable disease, which would
require all local doctors to report cases (in
humans) to the government. They also stepped up
inspections and quarantine procedures on live
pigs and frozen pork imported from mainland
provinces and said they would crack down on
illegal pork importsref.
Pork from Sichuan and Henan provinces, and also
Shenzhen, which supplies > 60% of the frozen
and chilled pork to Hong Kong, will re-enter
Hong Kong on Aug 24 for the 1st time since
imports were banned late in Jul 2005. Genetic
characterization of the first 9 of the 11 cases
known in Hong Kong have shown different
bacterial strains, suggesting the previous cases
were sporadic and that there was no link between
them. It would not be surprising if multiple
strains of S. suis are behind the
outbreak in Sichuan. If the digging up of dead,
infected pigs (with high titers of different
strains of type 2 S. suis in them) for
meat is behind the outbreak rather than
evolution of a more virulent, toxin-producing
strain, multiple Sichuan strains should be found
in pigs and man. Streptococcus suis was
isolated from 6.1% of raw pork meat from 3 of
the 6 wet markets in 6 districts in Hong Kong.
S. suis was particularly isolated in sites from
the tongue, tonsil, bone, and tail, but not from
lean meat/minced pork or internal organs.
Isolates were confirmed by PCR using S. suis-specific
primers, did not belong to serotype 2 using
serotype 2-specific antiserum, and were
clustered closely with other known serotypes by
phylogenetic analysis. 10 strains from patients
admitted to Hong Kong hospitals with sepsis or
meningitis in the past 10 years all belonged to
type 2, with closely related PFGE types that
were distinct from the S. suis strains
isolated from pork in this studyref.
13 cases (2 fatal) were reported in 2005, 8
cases in 2006 and 3 cases in 2007 (54-year-old
manref)
Serious infections with Streptococcus suis have
been recorded in the past in China : of the 22
cases, 5 cases which were ordinary type were cured;
10 cases were meningitis 2 type, 8 of which were
cured and 2 of which improved; an 7 cases were
toxicosis shock syndrome (TTS) 2 type , none of
which was able to avoid death. The total
mortality was 31.8%. At the time the disease was
widely epidemic and worsened (Zhang X , Ding J,
& Qin H: Clinical analysis of 22 cases of the
disease contracted both by man and pigs with swine
streptococcus Infections. (Chinese) Journal of
Tropical Medicine, 2, 2002; 2:361-63). The abstract
implies that an outbreak of human (and swine)
infections occurred but the exact details of the
length of time that the cases were found is not
given.
- USA : a 59-years old man reported in 2006
(occupational exposure)ref
Kay and colleagues
ref
present a cogent discussion on the classification of
S.
suis. Based on analysis of porcine streptococcal
strains in the 1950s and 1960s that were ungroupable
using the Lancefield typing sera, serogroups R, S and
T were designated for these porcine strains. The
S capsular strain became referred to as
S. suis
type 1 and the R capsular strain as type 2. Although
almost 30 capsular types have been now characterized,
type 2
S. suis remains the most relevant
serotype in porcine and human infection.
Transmission : reservoir
:
Sus
scrofa
(occupational disease
expecially in breeders and slaughterers). The organism
is carried on the pig's tonsils and is spread
pig-to-pig through nose rubbing or coughing. But it's
only found in small concentration on the pigs'
tonsils, so it's difficult for a human to catch it
that way. When the infection spreads to the brain,
causing meningitis, it's in far greater concentration,
and so it can be transmitted to humans who eat raw
infected pork or handle the dead animal with open
cuts. Although the governmental official states that
risk of infection is only present with open wounds,
Kay's study
ref
reported that only 20% of patients were noted to have
sustained minor cuts or burns before symptoms
occurred. Finding that many patients had no history of
any injury, the authors speculate that respiratory or
oral routes may be important.
=> a wide range of infections in pigs, including
meningitis, arthritis, pneumonia, septicemia,
endocarditis, encephalitis, polyserositis, and
abscesses. The bacterium is endemic in all pig-raising
countries world-wide, especially affecting large,
intensively managed pig farms. The disease is not
regarded to be highly infectious, most outbreaks are
limited to the affected farms, and is not notifiable,
nationally or internationally. Nevertheless, in the
affected farms, significant economic losses may be
observed, and, since antibiotic therapy gives
unsatisfactory results, vaccines have been developed
and widely used. The results of vaccination have been
inconsistent.
Human infection may occur, but it has generally been
known as occupational, affecting farmers and personnel
engaged with pig breeding and their handling,
including slaughter, not a food-borne disease. The
current spread of
Streptococcus suis in China
seems odd. Something must be perturbing the usual
epidemiology of this occupational infection. There may
be several guesses (and I emphasize guesses at this
point) based on the rereading of the reports:
- 1) The disease is being spread by the foodborne
route, and, therefore, is being transported to
markets at substantial distances. This would
probably be associated with some clinical outbreak
in swine in Sichuan, while sick pigs -- instead of
being presented for slaughter -- are sold on the
open market at heavily discounted prices. As
knowledge of the outbreak in people dries up the
local market, unscrupulous dealers would send the
meat further afield, thus explaining the new
cities involved. The farmer eating his own sick
pig falls in this category as well. The articles
above, and many others, refer incorrectly to this
disease as swine flu. Swine influenza is a well
known disease but it caused by the influenza
virus, not Streptococcus suis.
- 2) There might be a co-infection with a virus
that weakens certain human immune systems in the
outbreak area and, therefore, allows opportunistic
Streptococcus suis infection. What virus
can only be speculated.
- 3) There might be a synergism between 2
pathogens, say a virus and Streptococcus suis
. If the latter was occult and widespread in a
latent form, it is just adding a match to tinder.
- 4) The old epidemiological adage: seek and ye
shall find. This is more applicable to the newer
cases and rather doubtful if representing the
explanation for the outbreak in Sichuan.
Unfortunately, there is little information on the
swine populations in Sichuan, because one key factor
in putting together the cause of the outbreak would be
to know the status of local swine farms where the
cases are occurring. There is little information,
other than bans on pork, coming from the animal side,
but unless there is evidence of an outbreak in pigs
indicating a new, more virulent strain, occupational
exposure to normal
Streptococcus suis could
hardly explain the magnitude of the cases in humans
generated this far.
Additionally, the organism could have acquired a toxin
or some other factor, increasing its virulence. To
date, it has not clearly been spread from human to
human, and the speculation of an analogy to pneumonic
plague and its transmissibility is just that. Short
latent period and multi-organ failure are ultimate
causes for the higher-than-expected mortality rate of
the pig-borne disease : most patients suffered
failures in the kidneys, livers, lungs and heart
shortly after they were contracted, and some of them
died before timely treatment. The latent period of the
disease is so short that some patients died
within 10 hours after infection : in one case, a man
died 2 hours after slaughtering a sick pig. In
comparison, it normally takes a week or 2 for an
ordinary bacterial infection to break out. On the
other hand, the disease was caused by
Streptococcus
suis type 2, the deadliest of all the 35 forms
of pig-borne
S. suis bacteria. These are
different capsular types of
S. suis. Type 2
has always represented the most virulent type in both
swine and humans. 2 bacterial pathogens come
immediately to mind that may have a short time, in
hours not days, from inoculation and onset of
infection. Both Group A streptococcal and
Pasteurella
multocida (the latter usually associated with
feline bites) wound infections can occur within hours
of exposure, but the rapidity of onset does not
necessarily correlate with severity or fulminating
infection. Such rapidly fulminating infections can be
seen in pneumococcal (
S. pneumoniae)
postsplenectomy infection and in meningococcemia.
Marcelo Gottschalk, one of the world's leading experts
on the disease, works at the world's only reference
laboratory for
S.
suis at the University of Montreal in Canada.
Some farmers in Hong Kong and the mainland "vaccinate"
by feeding the tissue of sick pigs to healthy pigs,
according to the chairman of the Hong Kong Pig Farm
Association, Wong Kwong-wing. On Wed, 17 Aug 2005, he
said these practices could lead to mutations of
bacteria. Gottschalk warned that homemade vaccination
is "extremely dangerous" because, instead of
preventing the disease, healthy pigs may get infected
by the live bacteria which could lead to a serious
outbreak. While Wong said the overuse of antibiotics
on pig farms is common and could be a factor in the
outbreak, Gottschalk said this isn't likely. Overusing
antibiotics could increase the resistance of bacteria,
he said, but he doesn't think this carries a greater
threat since antibiotics still kill bacteria like
Streptococcus
suis easily.
=> severe flu-like symptoms (such as fever and
nausea ) =>
septicemia
and
streptococcal toxic shock-like syndrome (STSS
/ STSLS)ref
=>
fulminant sepsis
,
meningitis
followed by partial or
permanent hearing loss),
endocarditis
, and a hemorrhagic diathesis
can be associated with many bacteremic syndromes
Laboratory examinations :
multiple PCR gives results in 4 hours
Therapy : although a
substantial case fatality rate has been recognized so
far, if the mechanism of pathogenesis here is
elaboration of toxins, it is likely that
antimicrobials would not be as useful in established
cases. In a 2002 report
ref,
110 strains of
S. suis from swine in France
and 25 strains of the organism from humans (in
different countries of origin) were assessed for
antimicrobial sensitivity. Macrolide and
tetracycline resistance was found in some strains,
especially serotype 2, but the beta-lactam class
antimicrobial agents were active. Of note, among
porcine isolates, there was no correlation between
antimicrobial resistance and virulence.
Prevention : I am not
aware of any trials using a
S. suis type 2
vaccine in humans. Several approaches have been used
in swine, however, including sonicated organisms
ref,
a non-encapsulated mutant
ref,
and
suilysin, the thiol-activated haemolysin
ref.