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PLOS One logoLink to PLOS One
. 2021 Jan 28;16(1):e0245701. doi: 10.1371/journal.pone.0245701

Seroepidemiology of Toxoplasma gondii infection in people with alcohol consumption in Durango, Mexico

Sergio Estrada-Martinez 1, Alma Rosa Pérez-Álamos 1, Melina Ibarra-Segovia 2, Isabel Beristaín-Garcia 2, Agar Ramos-Nevárez 3, Leandro Saenz-Soto 3, Elizabeth Rábago-Sánchez 4, Carlos Alberto Guido-Arreola 3, Cosme Alvarado-Esquivel 4,*
Editor: Gheyath K Nasrallah5
PMCID: PMC7842906  PMID: 33507955

Abstract

The seroepidemiology of infection with Toxoplasma gondii (T. gondii) in alcohol consumers is largely undeveloped. In light of this, we sought to determine the seroprevalence of T. gondii infection in alcohol consumers in Durango, Mexico, and the association of T. gondii seroprevalence with characteristics of the population studied. Anti-T. gondii IgG and IgM antibodies were searched in sera of participants using commercially available enzyme immunoassays. Bivariate and logistic regression analyses were then used to determine the association between T. gondii infection and the characteristics of the population studied. Of the 1544 people studied (mean age: 39.4±14.0 years), 173 (11.2%) tested positive for anti-T. gondii IgG antibodies. We were able to test 167 of the 173 anti-T. gondii IgG positive sera for anti-T. gondii IgM antibodies. Fifty-five (32.9%) of these 167 serum samples were positive for anti-T. gondii IgM antibodies. Bivariate analysis showed that visual impairment, history of surgery, and hepatitis were negatively associated with T. gondii IgG seropositivity (P<0.05). In women, seropositivity to T. gondii was positively associated with a history of pregnancy (P<0.05). Logistic regression analysis showed that T. gondii seropositivity was associated with the variables consumption of armadillo meat (OR = 2.33; 95% CI: 1.04–5.22; P = 0.03), and the use of latrines for elimination of excretes (OR = 2.27; 95% CI: 1.07–4.80; P = 0.03); and high (>150 IU/ml) anti-T. gondii IgG antibodies were associated with consumption of both armadillo meat (OR = 2.25; 95% CI: 1.01–5.02; P = 0.04) and crowding at home (OR = 1.63; 95% CI: 1.02–2.61; P = 0.03). We found a distinct T. gondii seroprevalence in people with alcohol consumption from those previously found in population groups in the region. This is the first study that illustrates the association between high anti-T. gondii antibodies and crowding in Mexico, and the second study on the association between T. gondii infection and consumption of armadillo meat and the use of latrines in this country. We conclude that epidemiology of T. gondii infection in people with alcohol consumption deserves further investigation.

Introduction

The parasite Toxoplasma gondii (T. gondii) is a zoonotic pathogen belonging to apicomplexan parasites [1]. Infections of this parasite occur widely around the world [2]. It is estimated that about 30% of people are seropositive to T. gondii worldwide [3]. Cats and other Felidae are the definitive hosts of T. gondii, whereas a wide variety of warm-blooded animals, including humans, are intermediate hosts [4]. Humans can become infected with T. gondii through ingestion of oocyst-contaminated soil and water, tissue cysts in undercooked meat, or congenitally [5]. Infections with T. gondii are usually asymptomatic, but the parasite may induce severe disease in fetuses and immunocompromised patients [6]. Furthermore, T. gondii can cause posterior uveitis with vision loss [7]. Infection with T. gondii has also been linked to an increased incidence of several psychiatric diseases [8]. Chronic infections with T. gondii have been more recently linked to behavioral changes [9]. Suicide attempters have shown a higher seroprevalence of T. gondii infection than healthy controls [10]. In addition, infections with T. gondii have been linked to traffic [11, 12] and work accidents [13].

To the best of our knowledge, there have not been any studies done on the seroepidemiology of T. gondii infection in people with alcohol consumption. We believe it is important to study the seroepidemiology of T. gondii infection in this population group because alcohol consumption has been linked to infection with T. gondii in several studies. Seropositivity to T. gondii was associated with alcohol consumption in patients with heart disease [14]. In two studies of decedents in Poland, researchers found a positive association between T. gondii seropositivity and the presence of alcohol in the blood [15, 16]. In addition, alcohol consumption leads to an impaired immune response and dysregulated inflammatory state that contributes to an increased risk for infection [17]. On the other hand, infection with T. gondii has been associated with depression [18, 19], an illness that may lead to alcohol consumption. Therefore, we see a need to study the magnitude of infection with T. gondii and the factors associated with this infection in people with alcohol consumption. In this study, we sought to determine the seroprevalence of T. gondii infection in alcohol consumers in the northern Mexican city of Durango, and the T. gondii seroprevalence association with sociodemographic, clinical, and behavioral characteristics of the population studied.

Materials and methods

Study design and study population

We performed a cross sectional study from June 2014 to May 2018 in which we surveyed 1544 people with alcohol consumption in Durango State, Mexico. The inclusion criteria for enrollment of participants in the survey were: alcohol consumers, aged 15 years and older, and willing to participate in the study. “Alcohol consumption” is defined as the act of ingesting -typically orally- a beverage containing ethanol [20]. We used this criterium for enrollment of participants; however, we further considered quantity and frequency of alcohol drinking. Thereafter, alcohol consumption was defined as: consumption of any alcoholic drink (beer, wine, tequila, brandy, vodka, whisky, etc.) at least once a month during the previous six months. Occupation, gender, residence, education, socioeconomic status, or presence of any disease were not restrictive criteria for enrollment. Exclusion criteria were insufficient blood sample or unwillingness to provide information. Participants were enrolled in 9 public hospitals and health care centers in urban and rural areas of Durango when attending for health check-ups or medical consultations or when health care providers visit them at their workplace or home. Patients in these settings were informed about the study and invited to participate. Only patients that fulfilled the inclusion criteria were enrolled in the study.

Data collection and socio-demographic, clinical, behavioral, and housing variables of participants

A standardized questionnaire was administered to participants concerning their socio-demographic, clinical, behavioral, and housing characteristics. We saw no need to perform a validation of the questionnaire because we did not attempt to measure a variable or make a diagnosis with it. The questionnaire was used as a method for recording simple variables as age, gender, etc. The questionnaire has been used in a number of epidemiological studies in the same language in the same country [13, 14, 18, 21–26]. Items of housing variables were previously validated [27]. We obtained information about the age, gender, birthplace, residence, education, occupation, and socioeconomic status of participants. Clinical data included presence of any disease, dizziness, frequent abdominal pain or headache, impairments in memory, reflexes, hearing and vision, and history of blood transfusion, organ transplantation, lymphadenopathy, hepatitis, or surgery. Obstetric history in women was also obtained. With respect to behavioral data, we recorded information about contact with soil, cleaning cat feces, contact with cats and other animals, travel (in Mexico or abroad), frequency of eating away from home (in restaurants or fast-food outlets), washing hands before eating, consumption of unpasteurized milk, untreated water, unwashed raw vegetables or fruits, type of meat consumed, frequency of meat consumption, eating raw or undercooked meat, animal brains, dried or cured meat, or beef liver. We also recorded history of drug use, tobacco consumption, sexual promiscuity, and the following housing conditions: crowding, availability of potable water, type of flooring, form of elimination of excretes, and education of the head of the family.

Detection of anti-T. gondii IgG and IgM antibodies

A serum sample from each participant was obtained and stored at –20° C until analyzed. Detection and quantification of anti-T. gondii IgG antibodies were performed using a commercially available enzyme immunoassay “Toxoplasma gondii IgG” kit (Diagnostic Automation/Cortez Diagnostics, Inc., Woodland Hills, California. USA). Detection of anti-T. gondii IgM antibodies was performed using a commercially available enzyme immunoassay “Toxoplasma gondii IgM” kit (Diagnostic Automation/Cortez Diagnostics, Inc.). Only sera with seroreactivity to T. gondii IgG were further tested for IgM antibodies. Positive and negative controls were included in each run. Both IgG and IgM tests were performed following the instructions of the manufacturer. The immune status ratio (ISR or index) for anti-T. gondii IgG and IgM antibodies were calculated by dividing the sample optical density value by the cut-off calibrator value. We considered the sample positive for IgG or IgM when an IgG index or an IgM index was ≥1.1. Seropositivity was a qualitative measurement and considered the presence of anti-T. gondii IgG antibodies (regardless the levels), whereas serointensity was a quantitative measurement and considered the serum levels of anti-T. gondii IgG antibodies expressed as international units per milliliter (IU/ml). High levels (>150 IU/ml) of anti-T. gondii IgG antibodies were considered as a strong antibody response probably due to continuous exposure to the parasite.

Statistical analysis

Data analysis was performed with the aid of the software EPIDAT 3.1 and SPSS version 15.0 (SPSS Inc. Chicago, IL. USA). We calculated the sample size (n = 1543) based on the following parameters: a 6.1% estimated seroprevalence of T. gondii infection [21], 336,606 as the size of population from which the sample was selected, a precision of 1%, and a confidence level of 90%. We estimate there to be 336,606 alcohol consumers in the state. We arrived at this number by extrapolating the 51.4% prevalence of alcohol consumption reported in Mexico (https://encuestas.insp.mx/ena/ena2011/factsheet_alcohol25oct.pdf) from the number (654,876) of inhabitants in the municipality of Durango (http://cuentame.inegi.org.mx/monografias/informacion/dur/poblacion/default.aspx). To compare the frequencies among groups, we used the Pearson’s chi-square test and the Fisher exact test (when values were less than 5). The association between the variables and anti-T. gondii IgG seropositivity was assessed using binary logistic regression analysis with the Enter method. Only statistically significant factors (P value <0.05) obtained in the bivariate analysis were included in the binary logistic regression analysis. No analysis of groups within individual variables (multiple comparisons) was performed. A P-value < 0.05 was considered statistically significant.

Ethical aspects

Participants were informed about the aims and methodology of the survey. Enrollment in the study was voluntary. This study was approved by the General Hospital Institutional Review Board of the Secretary of Health in Durango City, Mexico (Approval No. 449/015). Written informed consent was obtained from all participants and from the next of kin for minor participants.

Results

Most participants were female (65.7%) and were born in the state of Durango (89.8%). Mean age of participants was 39.4±14.0 years (range: 15–93 years). Of the 1544 people surveyed, 173 (11.2%) were positive for anti-T. gondii IgG antibodies. Of these 173 seropositive individuals, 82 (47.4%) had anti-T. gondii IgG levels between 8 to 99 IU/ml, 15 (8.7%) between 100 to 150 IU/ml, and 76 (43.9%) higher than 150 IU/ml. We were able to test 167 of the 173 anti-T. gondii IgG positive sera for anti-T. gondii IgM antibodies. Fifty-five (32.9%) of these 167 serum samples were positive for anti-T. gondii IgM antibodies. Table 1 shows the sociodemographic and housing data of participants and the seroprevalence of T. gondii infection. Bivariate analysis showed that the sociodemographic characteristics gender, residence area, educational level, occupation, and socioeconomic status were significantly (P<0.05) associated with T. gondii IgG seropositivity, whereas the variables age group, birthplace, and place of residence showed P values higher than 0.05 in the bivariate analysis. Concerning housing characteristics, bivariate analysis showed that availability of potable water, type of flooring, form of elimination of excretes, and education of the head of the family were significantly (P<0.05) associated with T. gondii IgG seropositivity. Overcrowding was not associated with T. gondii seropositivity. Bivariate analysis showed that the clinical conditions visual impairment, history of surgery, and hepatitis were negatively associated (P<0.05) with T. gondii infection. Whereas other clinical variables as presence of any disease, dizziness, frequent abdominal pain or headache, impairments in memory, reflexes, and hearing, and history of blood transfusion, organ transplantation, and lymphadenopathy, showed P values higher than 0.05 in the bivariate analysis. Of the obstetric characteristics of women, only the variable of pregnancy history was significantly (P<0.05) associated with T. gondii IgG seropositivity. Table 2 shows the clinical data of participants and the seroprevalence of T. gondii infection.

Table 1. Socio-demographic and housing characteristics of participants and seroprevalence of T. gondii infection.

Characteristic Participants tested No. Prevalence of T. gondii infection P value
No. %
Age groups (years)
 30 or less 460 39 8.5 0.07
 31–50 746 90 12.1
 >50 338 44 13.0
Gender
 Male 530 90 17.0 0.00
 Female 1014 83 8.2
Birthplace
 Durango State 1387 148 10.7 0.06
 Other Mexican State 151 25 16.6
 Abroad 6 0 0.0
Residence place
 Durango State 1532 171 11.2 0.71
 Other Mexican State 11 2 18.2
 Abroad 1 0 0.0
Residence area
 Urban 1200 86 7.2 0.00
 Suburban 190 29 15.3
 Rural 154 58 37.7
Educational level
 No education 22 8 36.4 0.00
 1 to 6 years 248 65 26.2
 7–12 years 773 71 9.2
 >12 years 501 29 5.8
Occupation
 Agriculture 36 6 16.7 0.00
 Housewife 401 53 13.2
 Business 94 7 7.4
 Construction 11 1 9.1
 Employee 386 30 7.8
 Student 97 4 4.1
 Cattle raising 4 0 0.0
 Day laborer 7 1 14.3
 Factory worker 27 3 11.1
 Professional 238 10 4.2
 Miner 67 42 62.7
 Sex worker 27 3 11.1
 None 43 1 2.3
 Other 106 12 11.3
Socio-economic level
 Low 353 62 17.6 0.00
 Medium 1184 109 9.2
 High 7 2 28.6
Floor at home
 Ceramic or wood 932 75 8.0 0.00
 Concrete 578 86 14.9
 Soil 32 12 37.5
Availability of potable water
 In the home 1195 86 7.2 0.00
 In the land 24 4 16.7
 In the street 194 60 30.9
Toilet facilities
 Sewage pipes 1304 92 7.1 0.00
 Latrine or another 122 58 47.5
Crowding at home
 No 579 52 9.0 0.05
 Semi-crowded 538 57 10.6
 Overcrowded 277 40 14.4
Education of the head of family
 Seven years or more 920 60 6.5 0.00
 Four to six years 360 57 15.8
 Up to 3 years 140 35 25.0
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Table 2. Bivariate analysis of clinical data and infection with T. gondii in people with alcohol consumption.

Characteristic Subjects tested No. Prevalence of T. gondii infection P value
No. %
Clinical status
 Healthy 1093 127 11.6 0.46
 Ill 446 46 10.3
Lymphadenopathy ever
 Yes 412 40 9.7 0.24
 No 1126 133 11.8
Abdominal pain
 Yes 503 49 9.7 0.20
 No 1039 124 11.9
Headache frequently
 Yes 768 89 11.6 0.64
 No 774 84 10.9
Memory impairment
 Yes 597 60 10.1 0.29
 No 942 111 11.8
Dizziness
 Yes 448 55 11.3 0.97
 No 1053 118 11.2
Reflexes impairment
 Yes 257 29 11.3 0.97
 No 1285 144 11.2
Hearing impairment
 Yes 233 27 11.6 0.84
 No 1310 146 11.1
Visual impairment
 Yes 577 51 8.8 0.02
 No 965 122 12.6
Surgery ever
 Yes 892 87 9.8 0.03
 No 650 86 13.2
Transplantation
 Yes 3 0 0 1.00
 No 1538 173 11.2
Blood transfusion
 Yes 206 25 12.1 0.65
 No 1335 148 11.1
Hepatitis
 Yes 88 4 4.5 0.04
 No 1454 169 11.6
Pregnancies
 Yes 850 77 9.1 0.03
 No 150 6 4.0
Deliveries
 Yes 609 61 10.0 0.13
 No 239 16 6.7
Cesarean sections
 Yes 382 37 9.7 0.57
 No 466 40 8.6
Miscarriages
 Yes 284 28 9.9 0.58
 No 562 49 8.7
Stillbirths
 Yes 49 6 12.2 0.43
 No 789 70 8.9
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With respect to behavioral characteristics, bivariate analysis showed many variables associated with T. gondii seropositivity. Table 3 shows all behavioral characteristics significantly associated with T. gondii seropositivity in the bivariate analysis. The variables domestic travel, consumption of beef, mutton, chicken, turkey or horsemeat, frequency of meat consumption, degree of meat cooking, consumption of dried meat, sausages, and frequency of eating away from home were not associated with T. gondii seropositivity. Logistic regression analysis showed that T. gondii seropositivity was associated with the following variables: consumption of armadillo meat (OR = 2.33; 95% CI: 1.04–5.22; P = 0.03), and the use of latrines for elimination of excretes (OR = 2.27; 95% CI: 1.07–4.80; P = 0.03) (Table 4). Other sociodemographic, housing, or behavioral variables included in our study were not associated with T. gondii seropositivity by logistic regression analysis.

Table 3. Bivariate analysis of selected behavioral factors and infection with T. gondii in the population studied.

Characteristic Subjects tested No. Prevalence of T. gondii infection P value
No. %
Cats at home
 Yes 543 89 16.4 0.00
 No 999 84 8.4
Cats in the neighborhood
 Yes 1011 127 12.6 0.02
 No 531 46 8.7
Cleaning cat excrement
 Yes 400 57 14.3 0.02
 No 1134 115 10.1
Birds at home
 Yes 480 70 14.6 0.005
 No 1061 103 9.7
Raising farm animals
 Yes 423 87 20.6 0.00
 No 1119 86 7.7
Traveled abroad
 Yes 430 31 7.2 0.002
 No 1112 142 12.8
Goat meat consumption
 Yes 312 71 22.8 0.00
 No 1227 102 8.3
Boar meat consumption
 Yes 167 59 35.3 0.00
 No 1372 114 8.3
Pigeon meat consumption
 Yes 129 47 36.4 0.00
 No 1411 126 8.9
Duck meat consumption
 Yes 104 23 22.1 0.00
 No 1435 150 10.5
Quail meat consumption
 Yes 117 36 30.8 0.00
 No 1423 137 9.6
Rabbit meat consumption
 Yes 346 62 17.9 0.00
 No 1194 111 9.3
Venison consumption
 Yes 405 89 22.0 0.00
 No 1134 83 7.3
Squirrel meat consumption
 Yes 155 48 31.0 0.00
 No 1384 125 9.0
Opossum meat consumption
 Yes 60 30 50.0 0.00
 No 1478 142 9.6
Armadillo meat consumption
 Yes 72 40 55.6 0.00
 No 1467 133 9.1
Iguana meat consumption
 Yes 49 17 34.7 0.00
 No 1492 156 10.5
Snake meat consumption
 Yes 200 36 18.0 0.001
 No 1341 137 10.2
Fish consumption
 Yes 1380 163 11.8 0.03
 No 161 10 6.2
Skunk meat consumption
 Yes 22 11 50.0 0.00
 No 1522 162 10.6
Chorizo consumption
 Yes 1395 164 11.8 0.04
 No 147 9 6.1
Consumption of cow brain
 Yes 287 45 15.7 0.008
 No 1257 128 10.2
Liver consumption
 Yes 883 118 13.4 0.00
 No 546 34 6.2
Cow raw milk consumption
 Yes 468 76 16.2 0.00
 No 1076 97 9.0
Goat raw milk consumption
 Yes 37 12 32.4 0.00
 No 1507 161 10.7
Unwashed raw vegetables
 Yes 325 69 21.2 0.00
 No 1219 104 8.5
Unwashed raw fruits
 Yes 414 81 19.6 0.00
 No 1128 92 8.2
Untreated water
 Yes 564 99 17.6 0.00
 No 976 74 7.6
Tobacco consumption
 Yes 727 97 13.3 0.01
 No 817 76 9.3
Drug use
 Yes 159 27 17.0 0.01
 No 1383 146 10.6
Sexual promiscuity
 Yes 193 39 20.2 0.00
 No 1346 133 9.9
Soil contact
 Yes 899 124 13.8 0.00
 No 642 49 7.6
Washing hands before eating
 Yes 1448 153 10.6 0.001
 No 91 20 22.0
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Table 4. Multivariate analysis of selected characteristics of people with alcohol consumption and their association with T. gondii infection.

Characteristic Odds ratio 95% confidence interval P value
Gender (male) 1.10 0.74–1.92 0.45
Residence area (area) 1.70 0.37–7.98 0.48
Educational level (no education) 1.00 0.24–4.21 0.97
Occupation (none) 0.25 0.03–1.98 0.19
Socioeconomic level (low) 1.44 0.91–2.26 0.11
Cats at home (yes) 1.48 0.92–2.36 0.09
Cats in the neighborhood (yes) 0.83 0.52–1.34 0.45
Cleaning cat excrement (yes) 0.90 0.55–1.47 0.69
Birds at home (yes) 1.11 0.71–1.75 0.63
Raising farm animals (yes) 1.51 0.94–2.43 0.08
Traveled abroad (yes) 0.68 0.4–1.16 0.16
Goat meat consumption (yes) 0.95 0.55–1.66 0.87
Boar meat consumption (yes) 1.44 0.73–2.84 0.28
Pigeon meat consumption (yes) 1.08 0.52.31 0.84
Duck meat consumption (yes) 1.24 0.56–2.74 0.59
Quail meat consumption (yes) 1.31 0.622.74 0.47
Rabbit meat consumption (yes) 0.92 0.52–1.62 0.77
Venison consumption (yes) 1.41 0.82–2.43 0.21
Squirrel meat consumption (yes) 1.28 0.65–2.49 0.46
Opossum meat consumption (yes) 0.95 0.37–2.45 0.93
Armadillo meat consumption (yes) 2.33 1.04–5.22 0.03
Iguana meat consumption (yes) 1.56 0.63–3.87 0.33
Snake meat consumption (yes) 0.64 0.34–1.22 0.18
Fish consumption (yes) 1.21 0.56–2.60 0.62
Skunk meat consumption (yes) 1.09 0.27–4.42 0.89
Chorizo consumption (yes) 1.42 0.58–3.48 0.43
Consumption of cow brain (yes) 0.95 0.55–1.64 0.86
Liver consumption (yes) 1.37 0.84–2.25 0.20
Cow raw milk consumption (yes) 0.89 0.56–143 0.65
Goat raw milk consumption (yes) 0.47 0.14–1.54 0.21
Unwashed raw vegetables (yes) 1.46 0.76–2.79 0.24
Unwashed raw fruits (yes) 0.69 0.35–1.35 0.28
Untreated water (yes) 1.40 0.87–2.23 0.15
Tobacco consumption (yes) 1.21 0.79–1.85 0.35
Drug use (yes) 0.82 0.43–1.57 0.55
Sexual promiscuity (yes) 1.07 0.6–1.89 0.80
Soil contact (yes) 0.99 0.62–1.56 0.96
Washing hands before eating (yes) 1.02 0.46–2.23 0.95
Floor at home (soil) 0.78 0.25–2.42 0.66
Availability of potable water (in the street) 1.69 0.92–3.10 0.08
Toilet facilities (latrine) 2.27 1.07–4.80 0.03
Education of the head of family (up to 3 years) 1.26 0.68–2.33 0.44
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Our final task was to determine the association between high (>150 IU/ml) anti-T. gondii IgG antibody levels and the sociodemographic, housing, and behavioral characteristics of participants. Bivariate analysis showed that several variables are associated (P<0.05) with high (>150 IU/ml) anti-T. gondii IgG antibody levels. The variables associated with high anti-T. gondii IgG antibody levels by bivariate analysis were selected for further analysis by logistic regression analysis (Table 5). This additional analysis showed that high anti-T. gondii IgG antibodies were associated only with consumption of armadillo meat (OR = 2.25; 95% CI: 1.01–5.02; P = 0.04) and crowding at home (OR = 1.63; 95% CI: 1.02–2.61; P = 0.03).

Table 5. Multivariate analysis of selected characteristics of people with alcohol consumption and their association with high (>150 IU/ml) anti-T. gondii IgG antibodies.

Characteristic Odds ratio 95% confidence interval P value
Age (more than 50 years) 1.07 0.63–1.84 0.78
Gender (male) 1.2 0.75–1.90 0.43
Residence area (rural) 1.25 0.59–2.67 0.55
Educational level (no education) 0.99 0.22–4.31 0.99
Occupation (none) 0.24 0.03–1.86 0.17
Socioeconomic level (low) 1.31 0.84–2.06 0.22
Cats at home (yes) 1.49 0.98–2.25 0.05
Raising farm animals (yes) 1.48 0.94–2.33 0.08
Traveled abroad (yes) 0.69 0.41–1.18 0.18
Goat meat consumption (yes) 0.9 0.52–1.57 0.73
Boar meat consumption (yes) 1.34 0.68–2.64 0.38
Pigeon meat consumption (yes) 1.04 0.49–2.20 0.91
Duck meat consumption (yes) 1.16 0.52–2.58 0.7
Quail meat consumption (yes) 1.32 0.63–2.75 0.44
Rabbit meat consumption (yes) 0.92 0.52–1.61 0.78
Venison consumption (yes) 1.48 0.86–2.54 0.14
Squirrel meat consumption (yes) 1.32 0.68–2.55 0.4
Opossum meat consumption (yes) 0.83 0.33–2.07 0.7
Armadillo meat consumption (yes) 2.25 1.01–5.02 0.04
Iguana meat consumption (yes) 1.48 0.60–3.64 0.39
Snake meat consumption (yes) 0.64 0.34–1.20 0.16
Skunk meat consumption (yes) 1.12 0.29–4.36 0.86
Chorizo consumption (yes) 1.45 0.59–3.58 0.4
Liver consumption (yes) 1.39 0.86–2.25 0.17
Cow raw milk consumption (yes) 0.74 0.46–1.18 0.21
Unwashed raw vegetables (yes) 1.44 0.76–2.74 0.25
Unwashed raw fruits (yes) 0.75 0.39–1.46 0.4
Untreated water (yes) 1.39 0.87–2.21 0.15
Washing hands before eating (yes) 1.06 0.49–2.30 0.86
Floor at home (soil) 0.64 0.21–1.97 0.44
Availability of potable water (in the street) 1.72 0.93–3.19 0.08
Toilet facilities (latrine) 1.94 0.82–4.59 0.12
Crowding (yes) 1.63 1.02–2.61 0.03
Education of the head of the family (up to 3 years) 1.23 0.67–2.24 0.5
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Discussion

The seroprevalence and risk factors associated with T. gondii infection in people with alcohol consumption are largely unknown. Consequently, we attempted to determine the rate of T. gondii seropositivity and the seroprevalence association with the sociodemographic, clinical, behavioral, and housing characteristics in people with alcohol consumption in Durango, Mexico. The 11.2% seroprevalence of T. gondii infection found in this study is higher than the 6.1% seroprevalence of this infection reported in the general population of Durango City, Mexico [20], but is lower than the 23.8% T. gondii seroprevalence reported in the general population in rural communities in Durango State, Mexico [22]. It is unclear why alcohol consumers had a different seroprevalence of T. gondii infection from those in the general population in urban and rural Durango. In these surveys the same enzyme immunoassay was used. However, differences in the risk factors between the population groups might exist. Seroprevalence of T. gondii infection increases with age [21] and is high in rural areas [22]. The mean age of people in the present study (39.4±14.0 years) was comparable to the mean age (37.04±16.1 years) found in the survey in Durango City [21], but lower than that (42.5 ± 17.6 years) found in people in rural Durango [22]. The high seroprevalence of T. gondii infection in the subset of people from rural areas observed in our present study might have contributed to an increase in the general seroprevalence. However, the seroprevalence found in people with alcohol consumption is lower than those found in other population groups in our region, including waste pickers (21.1%) [23], schizophrenic patients (20%) [24], inmates (21.1%) [25], or miners (60%) [26]. This relatively low seroprevalence found in our study coincides with the finding of a study of the Finnish general population, where researchers found that T. gondii seroprevalence was not associated with alcohol use disorders [28]. It is unknown whether T. gondii-induced behavioral changes might lead to alcohol consumption or whether alcohol consumption may lead to risky behavior for T. gondii infection. This study was performed over a 4-year period; however, this fact does not affect the interpretation of the results as the immunoassays were the same and no change in the seroprevalence of T. gondii infection in Durango during the last 10 years has been reported.

We sought to determine the risk factors associated with T. gondii seropositivity and serointensity. Logistic regression analysis of sociodemographic, housing, and behavioral characteristics of people with alcohol consumption showed that T. gondii seropositivity was associated with consumption of armadillo meat, and the use of latrines for elimination of excretes. In an epidemiological study in elderly people in Durango, Mexico, we found that T. gondii seropositivity was associated with consumption of armadillo meat [29]. Thus, we demonstrate this association for the second time in Mexico. Serological evidence of T. gondii infection in armadillos has been established in Brazil [30, 31]. However, to the best of our knowledge, no study about T. gondii infection in armadillos in Mexico has been reported. Our conclusions coincide with a previous report in Mexico examining the association between T. gondii seropositivity and the use of latrines. This association was noted in an epidemiological study of pregnant women in the central Mexican city of Aguascalientes [32]. Additionally, high anti-T. gondii IgG antibodies were associated with consumption of armadillo meat and crowding at home. Incidence of toxoplasmosis increases with crowding and poor sanitary habits [33]. The association between high antibody levels and crowding found in the present study is in line with a previous report of an association between seroreactivity (IgG and IgM) to T. gondii and crowding in the US [34].

As to clinical characteristics, the negative association between T. gondii seropositivity and visual impairment, history of surgery, and hepatitis suggests that T. gondii infection did not play an important role in these clinical factors in the study population. In the women studied, the higher frequency of T. gondii seropositivity in women with pregnancies than in women without pregnancies may be due to a higher age in women with pregnancies than in those without pregnancies.

The current study has the following limitations: 1) Although the sample size was large, we studied subjects in only one Mexican state, and the results of this study cannot be extrapolated to other Mexican states; and 2) the quantity and frequency of alcohol intake was not correlated with T. gondii exposure. Epidemiological studies to evaluate the link between seropositivity and serointensity of T. gondii infection and alcohol consumption including several Mexican states and quantification of alcohol intake are needed.

Conclusions

This is the first study about the epidemiology of T. gondii exposure in alcohol consumers. We found a different T. gondii seroprevalence in alcohol consumers from those previously found in population groups in the region. This is the first study to show the association between high anti-T. gondii antibodies and overcrowding in Mexico, and the second study on the association between T. gondii infection and consumption of armadillo meat and the use of latrines in this country. We believe the epidemiology of T. gondii infection in people with alcohol consumption merits further investigation. We further believe identification of factors associated with T. gondii seropositivity in this study may help inform and contribute to the effective planning of prevention and control measures against infection with T. gondii and its sequelae.

Supporting information

S1 File

(DOCX)

Click here for additional data file. (22.5KB, docx)
S2 File

(DOCX)

Click here for additional data file. (24.8KB, docx)

Acknowledgments

Tolliver Cleveland Callison IV edited the manuscript.

Data Availability

All relevant data are within the paper and its Supporting Information files.

Funding Statement

This study was financially supported by Universidad Juárez del Estado de Durango, Mexico. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

Gheyath K Nasrallah

23 Nov 2020

PONE-D-20-27939

Seroepidemiology of Toxoplasma gondii infection in people with alcohol consumption

PLOS ONE

Dear Dr. Cosme Alvarado-Esquivel

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. I have reviewed both reviewer comments, one of them was "reject" and the other one was Minor revision. Thus, I will give you another chance to address the comments carefully. 

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Reviewer #1: The authors evaluated the " Seroepidemiology of Toxoplasma gondii infection in people with alcohol consumption". After close review I have recommended that the manuscript cannot be accepted for publication. Please see some major concerns as below:

Add the location of study in the title

Keywords must be different from title words.

The rational of the study is not clearly understood.

About the inclusion criteria, what about other criteria such as immune deficiency diseases, chronic diseases, etc?????

What about the exclusion criteria?

The main disadvantage of this study is the lack of a control group.

Considering serological tests, what about the range of equivocal results and index values for IgG and IgM?

Considering low specificity of IgM and IgG in the ELISA test, it is better that the authors perform the high level tests such as Elecsys Toxo IgM assay, PCR assay, …..

Add ethical statement number

Reviewer #2: Summary:

The authors studied the seroprevalence of toxoplasma in people with alcohol consumption in Durango in Mexico. They also reported the associated factors with being seropositive. The study included 1544 participants during the period 2014 to 2018 and found 11.2 % prevalence. The authors used bivariate analysis to compare the Prevalence Ratio among participants with different sociodemographic and clinical characteristics where they identified the characteristics associated with higher (or lower) prevalence ratio. The authors then included variables with statistical significance in a logistic regression model where they compared the Odd Ratio and identified consumption of armadillo meat, the use of latrine for elimination of excretes, and crowding at home as associated factors with being positive.

The authors addressed an interesting topic in a presentable fashion. They studied a wide range of characteristics which were quite compressive. The statistical methods were appropriately used to present the results.

The authors didn’t give clear description of the study setting, the sampling frame and the sampling technique.

Issues:

1- Authors might need to give a bit of context for the study settings including if it was conducted in Durango state or Durango city. It was not clear to the reviewer what area does this study cover. It was not clear as well where the recruitment of participant in the study was conducted (community, health facilities, ….???).

2- Would you explain the number mentioned in line 134 (336,606) as the size of population from which the sample was selected?

3- What was the sampling technique employed in this study? How the participants in the study were selected and enrolled?

4- Would you please highlight if the study duration of 4 years (2014 – 2018) would impact the interpretation of the results?

5- In table 5, the authors presented the logistic regression results of high IgG and some characteristics. The bivariate analysis of this characteristics was not reported in the manuscript.

6- The authors didn’t consider a P value of exactly 0.05 as significant, which is debatable.

7- In line 172, the authors stated that (crowding was not associated with seropositivity). However, it was mentioned that crowding was associated with (high) antibodies. The authors need to define the term (seropositivity) and make clear distinction between IgG, IgM and both IgG/IgM positive cases. Moreover, the clinical and statistical significance of the levels of IgG need to be explained.

8- It was mentioned in line 111 and 112 that “traveling, frequency of eating away from home (in restaurants or fast food outlets)” were studied as an associated factors. In the results section in lines 184 to 188, authors reported that these factors were not found to be associated with seropositivity. However, the reviewer failed to find these factors among the results tables.

9- In lines 173, 174 and 175, the authors mentioned that visual impairment, history of surgery, and hepatitis were associated with IgG seropositivity. This should be corrected to (negatively associated) as mentioned in line 36.

10- In line 33, the sentence starting (fitty-five …..) is confusing. Please consider mention first that 167 of the IgG positives were also tested for IgM and 55 of them were positive.

11- In line 29, please replace the word (detected) by another word (e.g. studies, measured) to avoid confusion.

12- Please consider how this study will inform the prevention and control measures.

**********

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Reviewer #1: No

Reviewer #2: Yes: Sayed Himatt

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PLoS One. 2021 Jan 28;16(1):e0245701. doi: 10.1371/journal.pone.0245701.r002

Author response to Decision Letter 0

14 Dec 2020

Durango, Dgo. Mexico. December 14, 2020.

Dear Editor,

Please find attached a revised version of our manuscript that has been modified according to the reviewers’ comments. In addition, please find below our response to each of the reviewers’ comments on a point-by-point basis.

We appreciate the valuable comments of the reviewers and we hope the revised manuscript may have more success for publication in the journal Plos One.

Kind regards,

Dr. Cosme Alvarado-Esquivel.

Laboratorio de Investigación Biomédica

Facultad de Medicina y Nutrición

Avenida Universidad S/N.

34000 Durango, Dgo. Mexico.

Tel/Fax.: 0052 618 8 271200

Email: alvaradocosme@yahoo.com

 

RESPONSE TO THE REVIEWERS’ COMMENTS

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming.

The manuscript was modified according to the PLOS ONE’s style requirements.

2.We suggest you thoroughly copyedit your manuscript for language usage, spelling, and grammar. If you do not know anyone who can help you do this, you may wish to consider employing a professional scientific editing service.

English was revised. The name of the American who review the manuscript was written in the Acknowledgements section. Changes were highlighted in the manuscript. A file (“Supporting information”) with the changes marked in green color was included. A clean copy of the edited manuscript (“Manuscript”) was included.

3. Please include additional information regarding the survey or questionnaire used in the study and ensure that you have provided sufficient details that others could replicate the analyses. For instance, if you developed a questionnaire as part of this study and it is not under a copyright more restrictive than CC-BY, please include a copy, in both the original language and English, as Supporting Information.

A questionnaire was included in both the original language and English.

4. In the Methods, please discuss whether and how the questionnaire was validated and/or pre-tested. If this did not occur, please provide the rationale for not doing so.

There was no need to perform a validation of the questionnaire because it has been used in a number of epidemiological studies in the same language in the same country. The questionnaire was not used as an evaluation scale but for recording simple variables as age, gender, etc. Items of housing variables were previously validated. This information was added to the Methods section (lines 108-113).

5. Please clearly define alcohol consumption and specifically outline the criteria that were used to determine consumption. The statement "...at least one drink a month..." is non-specific as different drinks have varying concentrations of alcohol.

Further information about the definition of alcohol consumption was added to the Methods section (lines 91-96).

6. In statistical methods, please clarify whether you corrected for multiple comparisons.

No analysis of groups within individual variables (multiple comparisons) was performed (lines 163-165).

Thank you for your valuable comments for improving our manuscript.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: No

Reviewer #2: Partly

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

5. Review Comments to the Author

Reviewer #1:

1. Add the location of study in the title

The location of the study was added to the Title.

2. Keywords must be different from title words.

Changed. All keywords are now different from the Title words.

3. The rational of the study is not clearly understood.

The rationale section was rewritten to make it clearer (lines 68-80).

4. About the inclusion criteria, what about other criteria such as immune deficiency diseases, chronic diseases, etc?????

The presence of any disease was not a restrictive criterium for inclusion (lines 96-98).

5. What about the exclusion criteria?

Exclusion criteria were added (lines 98-99).

6. The main disadvantage of this study is the lack of a control group.

This is not a case control study; it was not aimed to determine an association between T. gondii infection and alcohol consumption. This study is a cross-sectional study aimed to determine the prevalence of and factors associated with T. gondii infection in people with alcohol consumption.

7. Considering serological tests, what about the range of equivocal results and index values for IgG and IgM?

There were no equivocal results. Information about index values for IgG and IgM was added (lines 137-140).

8. Considering low specificity of IgM and IgG in the ELISA test, it is better that the authors perform the high level tests such as Elecsys Toxo IgM assay, PCR assay, …..

This study was aimed to determine the seroepidemiology of T. gondii infection and this aim can only be reached by determining the anti-T. gondii IgG and IgM antibodies. These infection markers are well accepted markers used for epidemiological studies.

9. Add ethical statement number

Added (lines 170-171).

Thank you for your valuable comments for improving our manuscript.

Reviewer #2:

1- Authors might need to give a bit of context for the study settings including if it was conducted in Durango state or Durango city. It was not clear to the reviewer what area does this study cover. It was not clear as well where the recruitment of participant in the study was conducted (community, health facilities, ….???).

Information about the study settings was added (lines 99-102).

2- Would you explain the number mentioned in line 134 (336,606) as the size of population from which the sample was selected?

An explanation about the size of population from which the sample was selected was added (lines 153-158).

3- What was the sampling technique employed in this study? How the participants in the study were selected and enrolled?

Information about sampling was added (lines 101-103).

4- Would you please highlight if the study duration of 4 years (2014 – 2018) would impact the interpretation of the results?

Information about a lack of impact of the duration of the study on the interpretations of the results was added to the Discussion section (lines 246-249).

5- In table 5, the authors presented the logistic regression results of high IgG and some characteristics. The bivariate analysis of this characteristics was not reported in the manuscript.

Information about results of bivariate analysis of high IgG antibody levels and the characteristics of participants was added (lines 211-219).

6- The authors didn’t consider a P value of exactly 0.05 as significant, which is debatable.

We used a P<0.05 as statistically significant just to be more stringent in determining associations between T. gondii infection and other variables.

7- In line 172, the authors stated that (crowding was not associated with seropositivity). However, it was mentioned that crowding was associated with (high) antibodies. The authors need to define the term (seropositivity) and make clear distinction between IgG, IgM and both IgG/IgM positive cases. Moreover, the clinical and statistical significance of the levels of IgG need to be explained.

An explanation about the terms seropositivity, serointensity and high antibody levels were added (lines 141-146).

8- It was mentioned in line 111 and 112 that “traveling, frequency of eating away from home (in restaurants or fast food outlets)” were studied as an associated factors. In the results section in lines 184 to 188, authors reported that these factors were not found to be associated with seropositivity. However, the reviewer failed to find these factors among the results tables.

More information about “traveling” was added (line 120). The words “traveled abroad” were included in the Tables. The words “domestic travel” are mentioned in line 203.

The variable “frequency of eating away from home” is mentioned in line 205.

9- In lines 173, 174 and 175, the authors mentioned that visual impairment, history of surgery, and hepatitis were associated with IgG seropositivity. This should be corrected to (negatively associated) as mentioned in line 36.

Corrected (lines 192-193).

10- In line 33, the sentence starting (fitty-five …..) is confusing. Please consider mention first that 167 of the IgG positives were also tested for IgM and 55 of them were positive.

The sentence was modified (lines 32-34).

11- In line 29, please replace the word (detected) by another word (e.g. studies, measured) to avoid confusion.

Changed by “searched” (lines 27-29).

12- Please consider how this study will inform the prevention and control measures.

Added (lines 288-291).

Thank you for your valuable comments for improving our manuscript.

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file. (26.6KB, docx)

Decision Letter 1

Gheyath K Nasrallah

6 Jan 2021

Seroepidemiology of Toxoplasma gondii infection in people with alcohol consumption in Durango, Mexico

PONE-D-20-27939R1

Dear Dr. Cosme Alvarado-Esquivel,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Gheyath K. Nasrallah, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: (No Response)

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Reviewer #2: Yes: Sayed Himatt

Acceptance letter

Gheyath K Nasrallah

11 Jan 2021

PONE-D-20-27939R1

Seroepidemiology of Toxoplasma gondii infection in people with alcohol consumption in Durango, Mexico

Dear Dr. Alvarado-Esquivel:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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Kind regards,

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on behalf of

Dr. Gheyath K. Nasrallah

Academic Editor

PLOS ONE

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