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TRICHINELLOSIS - CHINA: BACKGROUND
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A ProMED-mail post
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[The following information provides background to:
Undiagnosed fatal illness - China (02): (YN) trichinellosis 20090307.0952.
Only a very small fraction of human trichinellosis in China can be
attributed to eating infested dog meat. - Mod.JW]
[1]
Date: Sun 8 Mar 2009
Source: Gideon [abstracted, edited]
<http://www.gideononline.com/blog/2009/03/07/trichinosis-in-china/>
Background on Trichinellosis in China
-----------------------------------------
Primary references are available on request; (This is one of 17 582
Gideon text files which follow the status of individual diseases in
each country).
Time and Place:
Trichinosis [an alternative designation for the disease] was 1st
documented in China in 1918. Disease prevalence in Beijing was
estimated at 0.3 percent in 1918 and 0.16 percent in 1919. The
principal foci of trichinosis are located in the southeast, center and
northeast.
As of 1999, 17 of the country's provinces and autonomous regions
report the disease.
4033 cases (73 fatal) were reported during 1964
to 1979;
5558 in 1983;
15 599 (141 fatal) during 1980 to 1989;
5529 (26 fatal) during 1990 to 2002.
88.6 percent of clinical cases and 99.6 percent of fatal cases during
1964 to 2002 were reported from Yunnan, Guangxi and Tibet.
Prevalence surveys:
3.38 percent, nationwide (2001 to 2004)
5.5 percent of the population (survey of 10 provinces during 1991 to 2000)
2.4 percent of humans in Henan Province
3.1 percent of pigs in Henan Province (1991)
12.16 percent of persons in Hubei Province (1982 to 1996)
7 percent of dogs in Henan;
9.82 percent in Jilin;
23.52 percent in Inner Mongolia;
35.6 percent in Liaoning;
39.5 percent in Heilongjiang
21.9 percent of adult dogs in Heilongjiang Province (_Trichinella
nativa_, 1996 to 2004)
1.98 - 15.06 percent of rats (2001 publication)
0.09 - 29.63 percent of swine
6.76 percent of swine in Hubei (1997)
Seroprevalence surveys:
58.8 percent of persons in Eryuan County, rural Yunnan (2007 publication)
Vehicles:
94.3 percent of outbreaks among humans are caused by consumption of
raw or undercooked pork. Pork is implicated in 95.8 percent of
outbreaks (1964 to 1999). Raw pork dishes ("oru" and "shengpi") are
commonly implicated in Yunnan; the seroprevalence in this province
was 13.5 percent during the 1990-92. Garbage is the principal source
for infection of swine, and rats act as key reservoirs.
In Henan Province during 1996 to 1998, 0.6 percent to 1.6 percent of
market pork was found to be infested; 0.5 percent to 4.1 percent of
rats (11.1 percent of rats in abattoirs); and in humans, 2.2 percent
of peasants; 7.8 percent of professional drivers.
Mutton and game meat have been increasingly implicated in recent
years. In 1997, a Japanese traveler acquired trichinosis from smoked
bear meat while in China.
Animal Reservoirs:
As of 2002, trichinosis had been documented in 14 animal species in
China: pig, dog, cat, rat, cow, fox, bear, tiger, marten, raccoon,
muntjac, yellow weasel, wolf and wild boar.
The 1st outbreak ascribed to dog meat was reported in 1974. During
1974 to 1999, 81 cases of dog meat-associated trichinosis were
reported in Jilin and Liaoning, 6 in Beijing and 2 in Henan.
Infestation of dogs is widespread, in at least some cases by
_Trichinella nativa_ [described as an Arctic species of the worm, as
opposed to the more common _T. spiralis_ - Mod.JW].
Outbreaks:
The 1st outbreak of human disease in China was reported in 1964
(Tibet). 548 outbreaks, 23 004 cases and 236 deaths were recorded in
12 provinces and autonomous regions during 1964 to 1999.
At least 8 outbreaks up to 2001 were ascribed to consumption of dog
meat and 3 to consumption of wild boar; 7 outbreaks (250 cases)
were reported in Zhengzhou (Henan) during 1992 to 1996. A total of
467 cases were reported for the province during this period. 17
outbreaks (828 cases, 11 fatal) were reported in 8 provinces during
2000 to 2003, including 13 outbreaks related to pork.
Specific outbreaks:
- 1979 to 1980: An outbreak in Harbin was ascribed to scalded mutton.
One series described 4 outbreaks in the province, with 110 total
patients.
- 1995 to 1996: An outbreak (600 cases or more) in Zhengzhou was
associated with dumplings served at a restaurant.
- 2008 (publication year): An outbreak (9 cases, 2 fatal) in Tibet was
associated with infested pork.
--
Communicated by:
Steve Berger
Geographic Medicine
Tel Aviv Medical Center
<mberger@post.tau.ac.il>
******
[2]
Date: Sun 8 Mar 2009
From: Merritt Clifton <anmlpepl@whidbey.com>
While eating dogs may be part of the explanation for the high rate of
trichinella in China, "widespread consumption of dog meat" is
actually a widespread misconception and is something I have been to
China twice to investigate (among other issues).
By volume, about 85 percent of all dog consumption in China occurs in
Guangdong, and almost all of the rest in the Cantonese-speaking
coastal regions. Dog-eating is common in Mandarin-speaking regions
only close to Korea. Dog-eating is common in only about half of the
Cantonese-speaking part of China moreover, and is very rare in areas
that speak other languages.
There are about 100 restaurants in Beijing that serve dog meat, but
most are quite small, serving mainly Cantonese and Korean visitors as
well as occasional western thrill-seekers, and there are more than 14
000 restaurants in Beijing altogether. Probably, far more offer vegan
menus for visitors from India and the west than serve dog meat.
The geography of dog-eating and rabies outbreaks in China very
closely coincides, as I have pointed out on ProMED several times. But
the geography of _Trichinella_ deaths and dog-eating does not.
Dog-eating is relatively common in some parts of Sichuan. In Tibet on
the other hand, deadly riots broke out a few years ago when Chinese
soldiers began capturing and eating street dogs. No doubt, some
people eat dogs in Tibet, but not in public.
The distribution of the 811 cases that did not result in fatalities
may more closely coincide with the geography of dog-eating. The
deaths may occur mainly in more remote places with less developed
medical infrastructure. Guangzhau, the major center of dog-eating,
and Shanghai, where the 2nd most dogs are eaten (but just a fraction
of the Guangzhau volume), have relatively advanced medical
infrastructure.
A map of the distribution of dog-eating in China is available as a PDF
on request to me. Since I assembled it, the proportional weighting
toward the Guangdong region has only increased. There are relatively
small dog farms and enclaves of dog-eating that attract attention in
the north because they are unusual, and then vast dog farms & markets
in the south that attract less attention because they are more
familiar. The same is true of rabies outbreaks. An outbreak in the
regions where they are relatively rare will attract all sorts of
furor, while an outbreak in the southern mountains is almost routine.
--
Merritt Clifton
Editor, Animal People
P.O. Box 960
Clinton, WA 98236
<anmlpepl@whidbey.com>
[ProMED thanks Steve Berger for providing background information on
_Trichinella_ in China and Merritt Clifton for providing detailed
data on dog consumption and _Trichinella_ in China.
For a map of the provinces of China showing Yunnan in the south,
bordering Myanmar, Laos, and Viet Nam, see
<http://www.sacu.org/provmap.html>.
For the interactive HealthMap/ProMED map of China with links to other
recent ProMED-mail and PRO/MBDS posts in China and neighboring areas,
see
<http://healthmap.org/promed/en?g=1280761&v=36.5,103.9,4>.
- Mod.EP]
[see also:
Undiagnosed fatal illness - China (02): (YN) trichinellosis 20090307.0952
Undiagnosed fatal illness - China: (YN) 20090303.0869
2008
----
Trichinellosis, porcine - Germany: (Western Pomerania) 20081123.3700
Trichinellosis - Russia (06): (Kemerovo Region) 20081123.3697
Trichinellosis, salami - Argentina: (SFE) 20080722.2214
2007
----
Trichinellosis, imported infections: background 20070719.2320
Trichinellosis, human - Germany ex Poland 20070717.2292
Trichinellosis, human - Poland (W. Pomerania) (02) 20070713.2242
Trichinellosis - Russia (Krasnoyarsk) 20070422.1313
Foodborne illness, fatal, boar - Nepal (02): trichinellosis susp.
20070320.0984
Trichinellosis, wild boar sausage - Sweden ex Spain 20070317.0935]
........................................ep/msp/jw
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