FW:Subject: PRO/AH/EDR SARS - worldwide (176): serosurvey China animal traders

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PRO/AH/EDR> SARS - worldwide (176):

serosurvey China animal traders

 

SARS - WORLDWIDE (176): SEROSURVEY CHINA ANIMAL

TRADERS

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16 Oct 2003

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Source: Morbidity Mortality Weekly Report 17 Oct 2003

52(41);986-987 [edited]

<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5241a2.htm>

 

Prevalence of IgG Antibody to SARS-Associated

Coronavirus in Animal Traders -- Guangdong Province,

China, 2003

---------------------------

Severe acute respiratory syndrome (SARS) was

identified in 2003 as an infectious disease caused by

the SARS-associated coronavirus (SARS-CoV), a member

of the coronavirus family not observed previously in

humans (1,2). Because its sequence data differ from

those of known human coronaviruses, SARS-CoV is

suspected to have crossed the species barrier between

an animal host and humans.

 

The SARS outbreak began in China's Guangdong Province,

where approximately 1500 probable cases were

identified during November 2002--June 2003 (3).

Detection of SARS-like coronavirus has been reported

previously in masked palm civets (sometimes called

civet cats) and a raccoon dog for sale in a live

animal market in Shenzhen municipality (4).

 

This report summarizes results of an investigation

conducted by public health authorities in Guangdong

Province, which compared the seroprevalence of

SARS-CoV IgG antibody in animal traders (i.e., workers

in live animal markets) with that of persons in

control groups. The results indicated that 13 percent

of the animal traders, none of whom had SARS

diagnosed, had IgG antibody to SARS-CoV, compared with

1-3 percent of persons in 3 control groups. Although

the results provide indirect support for the

hypothesis of

an animal origin for SARS, they also underscore the

need for detailed patient histories and more focused

animal studies to confirm an animal origin for SARS.

 

The seroprevalence study was conducted by the

Guangdong Center for Disease Control and Prevention

(CDC) in conjunction with the Guangzhou CDC, Baiyun

District CDC, and Shijing Township Hospital. Traders

in 3 animal markets in Guangzhou, Guangdong Province,

were offered participation in the study, and samples

were collected on 4 May 2003 from those who gave

consent. The trader test results were compared with

those for persons in 3 control groups: 1) health-care

workers involved with SARS control in 2 city

hospitals, 2) public health workers in the Guangdong

CDC facility, and 3) healthy adults visiting a clinic

for routine physical examinations. Compared with the

overall control population, the animal traders were

more likely to be male and older; the majority of

persons in both the trader and control groups were

aged 20-39 years. A sample of blood (5 mL) was drawn

from each subject, and IgG antibody to SARS-CoV was

tested by enzyme-linked immunosorbent assay (ELISA) by

using the test kit (batch no. 20030501) manufactured

by Beijing Huada GBI Biotechnology Co. Ltd., Beijing.

 

Of 792 persons tested, IgG antibody to SARS-CoV was

detected in 72 (9.1 percent). Positive rates were

highest in the trader group (13.0 percent), compared

with the 3 control groups (range: 1.2-2.9 percent)

(Table 1 below). The prevalence of IgG antibody in the

trader group was statistically significantly higher

than that of the overall control population (chi

square = 26.1; p<0.01). In contrast, no statistically

significant difference was determined in the

prevalence of antibody detected among the 3 control

groups (chi square = 0.89; p = 0.64).

 

Among animal traders, the highest prevalence of

antibody was found among those who traded primarily

masked palm civets (72.7 percent), wild boars (57.1

percent), muntjac deer (56.3 percent), hares (46.2

percent), and pheasant (33.3 percent) (Table 2). The

prevalence of traders with IgG antibody to SARS-CoV

varied by market (6 percent, 11 percent, and 20

percent, respectively; p<0.001); no correlation was

found between SARS-CoV antibody and sex, age, or

number of years worked in a live animal market. None

of the subjects had SARS or atypical pneumonia

diagnosed during the Guangdong Province outbreak.

 

Reported by: D Yu, MD, H Li, R Xu, MPH, J He, J Lin, L

Li, W Li, H Xu, S Huang, J Huang, Guangdong Center for

Disease Control, Guangzhou, China.

 

MMWR Editorial Note:

 

This study found serologic evidence suggesting that

asymptomatic infection with SARS-CoV or an

antigenically related virus occurred in Guangdong

Province. Seroprevalence of IgG antibody to SARS-CoV

was substantially higher among traders of live animals

than among persons in control groups, consistent with

the hypothesis that SARS-CoV crossed the species

barrier from animals to humans. The results are

consistent with preliminary determinations of a joint

research team from China's Ministry of Agriculture and

Guangdong Province, which found that sequences of

coronavirus detected by polymerase chain reaction in

bats, monkeys, masked palm civets, and snakes were

identical to or similar to those of human SARS-CoV

isolates. In addition, a joint study by Shenzhen CDC

and Hong Kong University determined that the sequence

of coronavirus isolated from masked palm civets is 99

percent identical to human SARS-CoV (4). These

determinations appear consistent with the hypothesis

that an animal reservoir exists for SARS-CoV or an

antigenically related virus; however, the findings are

not sufficient to identify either the natural

reservoir for SARS-CoV or the animal(s) responsible

for crossover to humans.

 

Primary modes of SARS transmission probably are direct

contact or droplet spread from a patient symptomatic

with SARS; however, other routes of transmission might

exist (5). Approximately 63 percent of Guangdong

Province patients with clinically defined SARS had no

known history of exposure to other SARS patients, and

the percentage increased after April 2003 (6). This

trend of unknown exposure also was observed in other

areas (7). Therefore, the possibility of unrecognized

sources of infection or infection from asymptomatic

carriers of the virus cannot be excluded, although

some patients might also have pneumonia caused by

etiologies other than SARS-CoV.

 

The findings in this report are subject to at least 4

limitations. 1st, although subjects were categorized

as primarily traders of the animals they were selling

at the time of the survey, a substantial portion

traded or handled more than one type of animal. 2nd,

the small number of subjects with reported exposure to

certain types of animals limits the ability to

differentiate risk among specific groups of animal

traders. 3rd, although the animal traders worked at 3

markets in Guangzhou, risk might differ among traders

in other parts of Guangdong Province or elsewhere in

China. Finally, as with other urgently developed

tests, validation of the ELISA kit employed has not

been completed, and the IgG antibody cannot

distinguish recent from remote infection.

 

This report provides indirect support for the

hypothesis that SARS-CoV might have originated from an

animal source and identifies multiple animals for

further study. However, none of the traders in this

study had SARS, and only 2 SARS patients in Guangdong

Province were identified as animal traders (i.e., a

snake seller and a pigeon seller) (6). In contrast,

comparative analysis of early Guangdong cases,

unlinked to other SARS cases, indicated an

overrepresentation of food handlers (6). Whether the

antibody detected in the animal traders in this report

might represent infection with a related coronavirus

that cross-reacts with SARS-CoV, or whether that

antibody provides protection from SARS, is not known.

Efforts to identify a possible animal reservoir for

SARS might benefit from prompt attention to collecting

detailed histories from any future SARS patients

regarding animal and other environmental exposures and

initiating tracebacks to animal supply sources (e.g.,

markets, farms, and wildlife areas).

 

Acknowledgments

 

This report was based on contributions by Guangzhou

Municipal Center for Disease Control (CDC), Baiyun

District CDC; Shijing Township Hospital, Guangdong

Province; CK Lee, MD, World Health Organization

(WHO)--China SARS Team, Beijing, China. A Schuchat,

MD, WHO-China SARS Team and National Center for

Infectious Diseases, CDC.

 

References

 

1. Drosten C, Gunther S, Preiser W, et al.

Identification of a novel coronavirus in patients with

severe acute respiratory syndrome. N Engl J Med

2003;348:1967--76.

2. Ksiazek TG, Erdman D, Goldsmith CS, et al. A novel

coronavirus associated with severe acute respiratory

syndrome. N Engl J Med 2003;348:1953--66.

3. Li LH, Peng GW, Liang WJ, et al. Epidemiological

analysis on SARS clustered cases in Guangdong

province. South China J Prev Med 2003;29:3--5.

4. Guan Y, Zheng BJ, He YQ, et al. Isolation and

characterization of viruses related to the SARS

coronavirus from animals in southern China. Science

2003;302:276--8.

5. Ng SK. Possible role of an animal vector in the

SARS outbreak at Amoy Gardens. Lancet 2003;362:570--2.

6. He JF, Xu RH, Yu DW, et al. Severe acute

respiratory syndrome in Guangdong Province of China:

epidemiology and control measures. Chin J Prev Med

2003;37:227--32.

7. Beijing Joint SARS Expert Group. Large outbreak of

severe acute respiratory syndrome (SARS) in Beijing,

2003. Emerg Infect Dis (in press).

 

Table 1 - Prevalence of IgG antibody to

SARS-associated coronavirus in animal traders and

persons in 3 control groups -- Guangdong Province,

China, 2003

 

Group: No. tested / Testing positive (No./percent)

Animal traders 508 / (66/ 13.0)

Hospital workers 137 / (4/ 2.9)

Guangdong CDC workers 63 / (1/1.6)

Healthy adults in clinic 84 / (1/1.2)

 

Chi square 26.1 p less than 0.02 animal traders versus

other groups

 

Table 2 - Prevalence of IgG antibody to

SARS-associated coronavirus in selected animal

traders, by primary animal traded -- Guangdong

Province, China, 2003

 

Primary animal traded *: No. traders/ testing positive

(No./percent) / relative risk/ (95 percent CI)

Masked palm civet: 22/ (16/ 72.7) / 7.9 / (5.0-12.6)

Wild boar 28/ (16/ 57.1) / 6.2 / (3.8-10.3)

Muntjac deer 16/ (9/ 56.3) / 6.1 / (3.4-10.9)

Hare 13/ (6/ 46.2) / 5.0 / (2.5-10.2)

Pheasant 9/ (3/33.3)/ 4.9 / (0.7-24.8) **

Cat 43/ (8/ 18.6)/ 2.0 (1.0-4.2)

Other fowl 25/ (3/ 12.0)/ .3 (o.2-5.0) **

Snake 250/ (23/ 9.2)/ Reference group

 

* Categories not mutually exclusive, except for snakes

** Odds ratio and 95 percent confidence interval by

Fisher exact test

 

--

ProMED-mail

<promed

 

[These data are interesting and tantalizing although

not definitive. In addition to the questions posed in

the discussion above, there is the question of

asymptomatic infection with the SARS-associated

coronavirus (SARS-CoV), and its relevance to possible

transmission. Anecdotal information (hearsay) gathered

by this moderator is that some individuals with

positive IgG for the SARS-CoV (presumed to be

indicative of prior infection with the virus) when

interviewed were noted to have had a history of

respiratory illness, but in the absence of

hospitalization, were not considered to have had " the

disease " .

 

It would be interesting to know whether the definition

used in the above study for diagnosis of " SARS or

atypical pneumonia " in the study group was based on a

systematic interview of study participants to

determine whether there had been a history of a

significant respiratory illness on the part of those

animal traders with IgG evidence of infection with the

SARS-CoV, or whether illness was defined as having

been hospitalized with a diagnosis

of SARS. - Mod.MPP]

 

[see also:

SARS - worldwide (175): antibody survey, China

20030924.2412

SARS - worldwide (131): diagnostic testing

20030603.1359

SARS - worldwide (87): case definitions and

diagnostics 20030502.1103

SARS - worldwide (42): WHO historical overview

20030411.0878

SARS - worldwide (41):overview 20030411.0876]

.....................mpp/pg/dk

 

 

 

 

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