Prevalence of IgG Antibody to SARS-Associated Coronavirus in Animal Traders

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> 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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--

Dave Neale

Animals Asia Foundation

 

Find out more about the historic China Bear Rescue by visiting the

Animals Asia Foundation website at http://www.animalsasia.org