# Toxoplasma gondii Infection in Dustmen in Northeastern China: A Case-Control Seroprevalence Study

Authors: Ruo-Lan Jiang; Quan Zhao; Jing Jiang; Xue-Long Chen; Xiao-Xuan Zhang; Xiang Wu
Journal: BioMed Research International
 (2018)

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## Abstract

Background. Toxoplasmosis is caused by an intracellular parasiteToxoplasma gondii, which can infect many hosts including humans.Methods.In order to estimate whether dustmen are more susceptible toT. gondii, a case-control study was conducted containing 332 dustmen from Jilin and Heilongjiang in Northeastern China, as well as 332 general populations from the same regions as control subjects. Serum samples were tested IgG and IgM antibodies toT. gondii using the enzyme-linked immunosorbent assay (ELISA).Results. The overall anti-T. gondii IgG was 15.06% (50/332) in dustmen compared with 9.64% (32/332) in the controls (P = 0.0337). Also, 5 (1.51%) dustmen had anti-T. gondii IgM antibodies compared with 2 (0.60%) control individuals (P = 0.2543). A significant association was only found between dustmen and level ofT. gondii IgG in comparison with the control subjects. Seroprevalence ofT. gondii IgG antibodies in male dustmen was significant higher than male control subjects (P = 0.0399). Dustmen from Jilin had the significant higherT. gondii IgG rate (P = 0.0143), in comparison with the control subjects from Jilin. Moreover, dustmen raising cat at home had the significant higherT. gondii IgG rate (P = 0.0097), in comparison with the control subjects. Risk factor analysis suggested that raising cat at home and not having habits of washing hand before eating were mainly related to theT. gondii infection in dustmen.Conclusions.This is the first record of seroprevalence ofT. gondii infection in dustmen in Jilin and Heilongjiang provinces in Northeastern China. These findings also suggest that the government departments should pay close attention to the toxoplasmosis in dustmen in Northeastern China.


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## Body

## 1. Introduction

Toxoplasmosis is a zoonotic disease caused by an intracellular protozoan parasiteToxoplasma gondii, which has a global distribution and wide-ranges of hosts [1, 2]. Felines are the only definitive hosts for the parasite and virtually all warm-blooded animals are intermediate hosts such as humans [3, 4]. Foodborne and waterborne transmission as well as transplacental infection are the major routes for transmission ofT. gondii [5, 6]. Although 1/3 of the world populations are seropositive forT. gondii, most of them are asymptomatic [3]. However, it can cause various severe diseases, and even death in immunocompromised individuals [7].In view of such severe situations, it is essential to investigate the status ofT. gondii infection in workers in different professions. There are some investigations focusing on detection ofT. gondii in people worked at different professions recently. For example, Alvarado-Esquivel et al. demonstrated that 23 (12.0%) of 192 truck drivers were anti-T. gondii IgG antibodies positive in Mexico [8]; moreover, a total of 278 out of 464 migrant workers have been detected as Sahimin et al. detected asT. gondii-positive in Malaysia [9]. The similar studies have also been conducted in China, such as involving in livestock and poultry breeding and processing workers [10]. Dustman is an occupation prone to acquire several infections and toxoplasmosis in one of them [11]. It is important that information regardingT. gondii infection in dustmen is still scarce [11], especially in China. Therefore, a case-control study was conducted containing 332 dustmen from Jilin and Heilongjiang in Northeastern China, as well as 332 general populations from the same regions as control subjects, to determine the seroprevalence ofT. gondii in dustmen and to estimate whether dustmen are more susceptible to beT. gondii-infected compared with general populations in Jilin and Heilongjiang in Northeastern China.


## 2. Materials and Methods

### 2.1. Study Design and Population

The study was approved by the Changchun Sci-Tech University. Participants were made aware of the aim of the study. A total of 664 blood samples (including 332 dustmen and 332 control subjects) were collected from Jilin Province (41°N–46°N, 122°E–131°E) and Heilongjiang Province (43°26′N–53°33′N, 121°11′E–135°05′E) in Northeastern China, January 2017 and March 2018. The individuals’ occupations and names were not recorded to ensure confidentiality. The purposes and procedures of the study were explained to all participants, and written informed consent was obtained from them all. The sera were collected with agreements from the volunteers. Control sera were collected from volunteers. Information regarding gender, age, whether raising cat at home, whether having habits of washing hands before meals, or geographic region was recorded.


### 2.2. Sample Collection and Serological Tests

About 5 mL of venous blood was collected aseptically from each participant in Eppendorf tubes and kept at room temperature for 2 h. Then serum was separated from the whole blood by centrifugation at 3,000 rpm for 10 min, which was labeled and frozen at -20°C until use. Testing forT. gondiiserology (IgG and IgM) was performed using commercial enzyme immunoassay kits (Demeditec Diagnostics GmbH, Germany) [4]. Positive, negative, and blank controls were included in every plate. Optical densities were measured by photometer at a wavelength of 450 nm. Values higher than the cut-off (10 IU/mL) were considered positive.


### 2.3. Date Analysis

The data of questionnaire covered information such as gender, age, whether raising cat at home, whether having habits of washing hands before meals, or geographic region. The information of questionnaire and experimental results was entered on to an excel spreadsheet and transferred to SPSS v. 19.0 software package (SPSS Inc., USA) [4]. Univariate analysis was used to analyze the association between variables andT. gondiiinfection. Probability (P) value < 0.05 was considered as statistically significant in the analysis.


## 2.1. Study Design and Population

The study was approved by the Changchun Sci-Tech University. Participants were made aware of the aim of the study. A total of 664 blood samples (including 332 dustmen and 332 control subjects) were collected from Jilin Province (41°N–46°N, 122°E–131°E) and Heilongjiang Province (43°26′N–53°33′N, 121°11′E–135°05′E) in Northeastern China, January 2017 and March 2018. The individuals’ occupations and names were not recorded to ensure confidentiality. The purposes and procedures of the study were explained to all participants, and written informed consent was obtained from them all. The sera were collected with agreements from the volunteers. Control sera were collected from volunteers. Information regarding gender, age, whether raising cat at home, whether having habits of washing hands before meals, or geographic region was recorded.


## 2.2. Sample Collection and Serological Tests

About 5 mL of venous blood was collected aseptically from each participant in Eppendorf tubes and kept at room temperature for 2 h. Then serum was separated from the whole blood by centrifugation at 3,000 rpm for 10 min, which was labeled and frozen at -20°C until use. Testing forT. gondiiserology (IgG and IgM) was performed using commercial enzyme immunoassay kits (Demeditec Diagnostics GmbH, Germany) [4]. Positive, negative, and blank controls were included in every plate. Optical densities were measured by photometer at a wavelength of 450 nm. Values higher than the cut-off (10 IU/mL) were considered positive.


## 2.3. Date Analysis

The data of questionnaire covered information such as gender, age, whether raising cat at home, whether having habits of washing hands before meals, or geographic region. The information of questionnaire and experimental results was entered on to an excel spreadsheet and transferred to SPSS v. 19.0 software package (SPSS Inc., USA) [4]. Univariate analysis was used to analyze the association between variables andT. gondiiinfection. Probability (P) value < 0.05 was considered as statistically significant in the analysis.


## 3. Results and Discussion

In the present study, a total of 332 dustmen and 332 control individuals were examined (Tables1 and 2). Of the dustmen, 50 (15.06%) and 5(1.51%) were detected as anti-T. gondii IgG and IgM antibodies positive, respectively, based on the ELISA methods (Tables 1 and 2). Of them, only two samples were detected as both anti-T. gondii IgG and IgM antibodies positive. The overall prevalence of anti-T. gondiiIgG and IgM antibodies in the control individuals was 9.64% (32/332) and 0.60% (2/332), respectively (Tables 1 and 2). TheT. gondii IgG seropositivity rate was 15.70% (17/147) and 16.08% (23/185) in dustmen in Jilin and Heilongjiang, respectively (Table 1). There are 8.67% (13/150) and 10.44% (19/182) control individuals were examined asT. gondii IgG seropositivity in Jilin and Heilongjiang, respectively (Table 1). The dustmen (15.06%) had the significant higherT. gondii IgG seroprevalence than control subjects (9.64%,P = 0.0337) (Table 1); however, no significant difference ofT. gondii IgM seroprevalence was found between dustmen group and control group (P = 0.2543) (Table 2). In dustmen groups, having cat at home (P = 0.0269) and not having habits of washing hand before eating (P = 0.0117) were identified to be associated withT. gondii infection in dustmen (Table 1).Table 1
Seroprevalence ofT. gondii IgG infection in dustmen and control subjects in China.
Characteristic Dustmen Control subjects Dustmen vs Controls No. tested No. positive % (95% CI) Pvalue No. tested No. positive % (95% CI) Pvalue P value Age Group (years) ≤ 40 24 4 16.67 (0.59-32.74) 0.6599 112 12 10.71 (4.90-16.53) 0.8646 0.4115 41 – 50 129 22 17.05 (10.48-23.63) 82 8 8.89 (2.90-14.88) 0.1390 51 – 60 179 24 18.32 (11.61-25.03) 138 12 8.70 (3.94-13.46) 0.1898 Gender Male 162 25 15.43 (9.81-21.05) 0.8533 171 14 8.19 (4.04-12.34) 0.3557 0.0399 Female 170 25 14.71 (9.33-20.08) 161 18 11.18 (6.26-16.10) 0.3403 Geographic region Jilin 147 27 15.70 (10.21-21.19) 0.1331 150 13 8.67 (4.11-13.22) 0.5859 0.0143 Heilongjiang 185 23 16.08 (9.99-22.18) 182 19 10.44 (5.95-14.92) 0.5488 Cat at home No 154 16 10.39 (5.52-15.26) 0.0269 137 13 9.49 (4.52-14.46) 0.9383 0.7980 Yes 178 34 19.77 (13.76-25.78) 195 19 9.74 (5.54-13.94) 0.0097 Habits of washing hand before meals No 158 28 16.28 (10.71-21.85) 0.0117 161 22 13.66 (8.30-19.03) 0.0159 0.3190 Yes 174 22 14.47 (8.81-20.13) 171 10 5.85 (2.30-9.40) 0.0686 Total 332 50 15.06 (11.19-18.93)  332 32 9.64 (6.45-12.83)  0.0337Table 2
Seroprevalence ofT. gondiiIgM infection in dustmen and control subjects in China.
Characteristic Dustmen Control subjects Dustmen vs Controls No. tested No. positive % (95% CI) P value No. tested No. positive % (95% CI) P value P value Age Group (years) ≤ 40 24 0 0 (-) 0.8173 112 1 0.89 (0-2.66) 0.7103 0.6422 41 – 50 129 2 1.55 (0-3.71) 82 0 0 (-) 0.2573 51 – 60 179 3 1.68 (0-3.57) 138 1 0.72 (0-2.16) 0.4518 Gender Male 162 5 3.09 (0.39-5.78) 0.0210 171 2 1.17 (0-2.80) 0.1560 0.2230 Female 170 0 0 (-) 161 0 0 (-) - Geographic region Jilin 147 2 1.36 (0-3.26) 0.8462 150 1 0.67 (0-1.98) 0.8907 0.5499 Heilongjiang 185 3 1.62 (0-3.46) 182 1 0.55 (0-1.63) 0.3226 Cat at home No 154 2 1.30 (0-3.11) 0.7730 137 0 0 (-) 0.2345 0.1836 Yes 178 3 1.69 (0-3.59) 195 2 1.03 (0-2.45) 0.5800 Habits of washing hand before meals No 158 5 3.16 (0.41-5.92) 0.0181 161 2 1.24 (0-2.97) 0.1438 0.2413 Yes 174 0 0 (-) 171 0 0 (-) - Total 332 5 1.51 (0.19-2.82)  332 2 0.60 (0-1.44)  0.2543T. gondii is one of the most important foodborne zoonotic pathogens, which can cause various severe diseases and even death in immunocompromised individuals [7]. Our case-control study firstly estimated the seroprevalence ofT. gondii infection in dustmen. A total of 50 out of 332 dustmen were examined asT. gondii IgG-positive. The overall seroprevalence of anti-T. gondii IgG was 15.06%, which is significant higher than that in control individuals (9.64%, 32/332,P = 0.0337). However, although the seroprevalence of anti-T. gondii IgM in dustmen was higher than control groups, the difference was not statistically significant (P = 0.2543). These findings suggest that dustmen are more susceptible to beT. gondii-infected than general individuals, and the government departments should pay close attention to the toxoplasmosis in dustmen.Previous studies have also demonstrated that age was highly related to theT. gondii seropositivity [12–15]. Perhaps, elder dustmen had more opportunity to interact with the infective oocysts than younger dustmen. In the present study, seroprevalence ofT. gondii in dustmen was increase with age (Table 1); however, the difference was not statistically significant (P = 0.6599). Moreover, previous studies demonstrated that females were more susceptible to the males, which differ from the present results, revealing that no significant difference in theT. gondii IgG prevalence between males (15.43%) and females (14.71%) was found (Table 1), and males had a significant higherT. gondii IgM prevalence than females (P = 0.0210) (Table 2). Also, there was no significant difference statistically among different area of residence (Tables 1 and 2). However, in geographic region groups, dustmen from Jilin had the significant higherT. gondii IgG seroprevalence (P = 0.0143) (Table 1) than control subjects from Jilin; the findings suggest that dustmen from Jilin must be must be paid attention to detection ofT. gondiiinfection.Cat is the only definitive host forT. gondii, so they play a crucial role in transmittingT. gondii[3, 16, 17]. Cats discharge feces containingT. gondiioocysts into the environment and then become the potential resources of human infection [18]. Therefore, dustmen raising cat at home had a significant higherT. gondii IgG seroprevalence than not raising cat at home groups. Moreover, bothT. gondii IgG and IgM seroprevalence in dustmen who have habits of washing hands before eating were significant lower than those who have not habits of washing hands before eating. The findings suggest the dustmen and other people must cultivate good health habits and wash hands before eating.


## 4. Conclusion

In summary, this is the first report of seroprevalence ofT. gondiiinfection in dustmen in Jilin and Heilongjiang Province in Northeastern China. Dustmen were seen to be more susceptible than control individuals. Seroprevalence ofT. gondii infection in dustmen was mainly related to raising cat at home and not washing hands before eating. The findings will provide key and baseline data for prevention and control of toxoplasmosis in dustmen.



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