most infections with t. gondii occur by ingestion of food or water contaminated with oocysts shed by cats [ 3 , 4 ] and eating undercooked or raw meat containing tissue cysts [ 3 , 5 ] . however , some t. gondii - infected individuals develop chorioretinitis that may progress to blindness . immunocompromised patients infected with t. gondii may develop severe neurological disease [ 7 , 8 ] . in addition , primary infections with t. gondii during pregnancy may lead to congenital disease [ 3 , 8 ] . infections with t. gondii may manifest in the heart in humans [ 9 - 13 ] and animals [ 14 - 17 ] with myocarditis [ 18 - 20 ] , pericarditis with myocarditis [ 21 , 22 ] , and acute heart failure [ 23 , 24 ] . patients with t. gondii myocarditis may present with pericardial effusion , constrictive pericarditis , congestive heart failure , and arrhythmias . the seroepidemiology of infection with t. gondii in patients suffering from heart diseases has been poorly studied . we are not aware of any data about the epidemiology of t. gondii infection in these patients in mexico . therefore , we determined the association between t. gondii exposure and patients with heart disease attending in a public hospital in northern mexico , and the association of seropositivity to t. gondii with socio - demographic , behavioral , and clinical characteristics of these patients . through a case - control study , we enrolled 400 patients suffering from heart diseases attending in a public hospital in durango city , mexico and 400 control subjects without heart diseases of the same city . inclusion criteria for the cases were : 1 ) inpatients with heart disease attending in the cardiology department at the general hospital of the secretary of health in durango city ; 2 ) aged 11 years and older ; and 3 ) that voluntarily accepted to participate . inclusion criteria for the control subjects were : 1 ) people without heart diseases from the general population of durango city ; and 2 ) who voluntarily accepted to participate in the study . patients included 156 ( 39% ) males and 244 ( 61% ) females with a mean age of 58.87  14.59 years ( range 11 - 93 years ) . controls included 156 males and 244 females with a mean age of 58.76  14.54 years ( range 9 - 91 ) . this study was approved by the ethical committee of the general hospital of the secretary of health in durango city , mexico . a written informed consent was obtained from all participants and from the next of kin of minor participants . for calculation of the sample size , we used a 95% confidence level , a power of 80% , a 1:1 proportion of cases and controls , a reference seroprevalence of 6.1%   as the expected frequency of exposure in controls , and an odds ratio ( or ) of 2.1 . the socio - demographic , clinical , and behavioral characteristics of the patients were obtained with the aid of a standardized questionnaire . socio - demographic data included age , sex , birthplace , residence , educational level , occupation , and socioeconomic status . clinical data included diagnosis of the heart disease , evolution time ( years ) of the heart disease , functional classification of the heart disease , and response to treatment . to evaluate the functional class of heart disease , we used the criteria of the new york heart association . in addition , we obtained clinical data about the presence of underlying diseases , history of lymphadenopathy , surgery , blood transfusion or transplants , presence of frequent headaches , dizziness , and impairments of memory , reflexes , hearing , and vision . behavioral data included contact with animals , cleaning cat excrement , foreign traveling , consumption of meat ( pork , beef , goat , lamb , boar , chicken , turkey , pigeon , duck , rabbit , venison , squirrel , horse , opossum , or other ) , frequency of meat consumption , consumption of raw or undercooked meat , unpasteurized milk , dried or processed meat ( ham , sausages or chorizo ) , consumption of unwashed raw vegetables or fruits , untreated water , frequency of eating away from home ( in restaurants or fast food outlets ) , contact with soil ( gardening or agriculture ) , hand washing before eating , and type of flooring at home . gondii igg antibody levels were expressed as international units ( iu)/ml . a cut - off of  8 iu / ml was used for seropositivity . in addition , sera of patients positive for anti - t . toxoplasma igm  kit ( diagnostic automation inc . , calabasas , ca , usa ) . the statistical analysis was performed with the software : epi info version 7 and spss version 15.0 . we used the student s t - test to compare age among cases and controls . the pearson s chi - square test and the fisher exact test ( when values were small ) were used for comparison of the frequencies among groups . multivariate analysis was used to assess the association between the characteristics of the patients and the seropositivity to anti - t . . socio - demographic and behavioral characteristics of the patients were included in the multivariate analysis if they had a p value  0.20 in the bivariate analysis . or and 95% confidence interval ( ci ) were calculated by multivariate analysis with the enter method . through a case - control study , we enrolled 400 patients suffering from heart diseases attending in a public hospital in durango city , mexico and 400 control subjects without heart diseases of the same city . inclusion criteria for the cases were : 1 ) inpatients with heart disease attending in the cardiology department at the general hospital of the secretary of health in durango city ; 2 ) aged 11 years and older ; and 3 ) that voluntarily accepted to participate . inclusion criteria for the control subjects were : 1 ) people without heart diseases from the general population of durango city ; and 2 ) who voluntarily accepted to participate in the study . patients included 156 ( 39% ) males and 244 ( 61% ) females with a mean age of 58.87  14.59 years ( range 11 - 93 years ) . controls included 156 males and 244 females with a mean age of 58.76  14.54 years ( range 9 - 91 ) . this study was approved by the ethical committee of the general hospital of the secretary of health in durango city , mexico . a written informed consent was obtained from all participants and from the next of kin of minor participants . for calculation of the sample size , we used a 95% confidence level , a power of 80% , a 1:1 proportion of cases and controls , a reference seroprevalence of 6.1%   as the expected frequency of exposure in controls , and an odds ratio ( or ) of 2.1 . the socio - demographic , clinical , and behavioral characteristics of the patients were obtained with the aid of a standardized questionnaire . socio - demographic data included age , sex , birthplace , residence , educational level , occupation , and socioeconomic status . clinical data included diagnosis of the heart disease , evolution time ( years ) of the heart disease , functional classification of the heart disease , and response to treatment . to evaluate the functional class of heart disease in addition , we obtained clinical data about the presence of underlying diseases , history of lymphadenopathy , surgery , blood transfusion or transplants , presence of frequent headaches , dizziness , and impairments of memory , reflexes , hearing , and vision . behavioral data included contact with animals , cleaning cat excrement , foreign traveling , consumption of meat ( pork , beef , goat , lamb , boar , chicken , turkey , pigeon , duck , rabbit , venison , squirrel , horse , opossum , or other ) , frequency of meat consumption , consumption of raw or undercooked meat , unpasteurized milk , dried or processed meat ( ham , sausages or chorizo ) , consumption of unwashed raw vegetables or fruits , untreated water , frequency of eating away from home ( in restaurants or fast food outlets ) , contact with soil ( gardening or agriculture ) , hand washing before eating , and type of flooring at home . toxoplasma igm  kit ( diagnostic automation inc . , calabasas , ca , usa ) . the statistical analysis was performed with the software : epi info version 7 and spss version 15.0 . we used the student s t - test to compare age among cases and controls . the pearson s chi - square test and the fisher exact test ( when values were small ) were used for comparison of the frequencies among groups . multivariate analysis was used to assess the association between the characteristics of the patients and the seropositivity to anti - t . socio - demographic and behavioral characteristics of the patients were included in the multivariate analysis if they had a p value  0.20 in the bivariate analysis . or and 95% confidence interval ( ci ) were calculated by multivariate analysis with the enter method . anti - t . gondii igg antibodies were detected in 55 ( 13.8% ) of 400 patients with heart diseases and in 32 ( 8.0% ) of 400 controls . gondii igg antibodies was significantly higher in cases than in controls ( or = 1.83 ; 95% ci : 1.15 - 2.90 ; p = 0.01 ) . gondii igg levels ( > 150 iu / ml ) were found in 28 ( 50.9% ) of the 55 positive cases and in 14 ( 43.8% ) of the 32 positive controls ( p = 0.51 ) . gondii igm antibodies were found in 13 ( 23.6% ) of the 55 anti - t . gondii igg positive patients and in 19 ( 59.4% ) of 32 anti - t . gondii igm antibodies was significantly lower in cases than in controls ( or = 0.21 ; 95% ci : 0.08 - 0.54 ; p = 0.0008 ) . general socio - demographic characteristics of the 400 patients studied and their correlation with t. gondii seroprevalence are shown in table 1 . seroprevalence of t. gondii infection was not associated with age , sex , residence , educational level , occupation or socioeconomic level of the patients by bivariate analysis . in contrast , patients born out of durango state had a significantly higher seroprevalence of t. gondii infection than patients born in durango state ( p = 0.008 ) . agriculture , business , employee , cattle raising , factory worker , professional , other . showed p values  0.20 by bivariate analysis . whereas other diagnoses of heart disease , functional stages of heart disease , response to treatment , presence of underlying diseases , history of lymphadenopathy , surgery or transplants , presence of frequent headaches , dizziness , and impairments of memory , reflexes , hearing , and vision showed p values > 0.20 by bivariate analysis . a selection of clinical characteristics of the patients and their correlation with t. gondii seroprevalence is shown in table 2 . in female patients , seropositivity to t. gondii did not correlate with obstetric history . among the behavioral characteristics , a number of variables showed p values  0.20 in the bivariate analysis including national trips ( p = 0.12 ) , consumption of meat from squirrel ( p = 0.08 ) , opossum ( p = 0.05 ) , armadillo ( p = 0.18 ) , iguana ( p = 0.14 ) , and snake ( p = 0.19 ) , degree of meat cooking ( p = 0.05 ) , consumption of unwashed raw fruits ( p = 0.06 ) , frequency of eating out of home ( p = 0.07 ) , frequency of meat consumption ( p = 0.16 ) , and alcohol consumption ( p = 0.02 ) . a selection of behavioral characteristics of the patients and their correlation with t. gondii seroprevalence are shown in table 3 . other behavioral characteristics of patients including contact with cats , cleaning cat excrement , raising animals , consumption of meat other than those from squirrel , opossum , armadillo , iguana and snake , consumption of unpasteurized milk , processed meat , unwashed raw vegetables , and untreated water , and contact with soil showed p values > 0.20 in the bivariate analysis . further analysis by using logistic regression showed that t. gondii exposure was positively associated with being born out of durango state ( or = 2.93 ; 95% ci : 1.40 - 6.13 ; p = 0.004 ) , and with consumption of alcohol ( or = 2.04 ; 95% ci : 1.01 - 4.12 ; p = 0.04 ) ( table 4 ) . the present study was performed to investigate the association of t. gondii infection with patients suffering from heart diseases attending in a public hospital in durango city , mexico and to determine the correlates of infection in these patients . this seroprevalence is higher than the 8.0% seroprevalence found in controls , and the 6.1% seroprevalence of t. gondii infection reported in the general population in durango city . results indicate that patients with heart diseases represent a risk group for t. gondii infection . seroprevalence of t. gondii infection increases with age in our region [ 25 , 27 ] . therefore , we matched cases and controls by age and this strategy allowed us to evaluate properly the association between t. gondii exposure and patients with heart disease . it is hypothesized that patients with t. gondii infection have a higher risk for heart disease caused by the presence of cysts in the heart muscle . the interaction of t. gondii within skeletal muscle cells has been nicely described recently . however , to the best of our knowledge , the interaction of t. gondii within heart muscle cells has not been studied . it is unclear how t. gondii may affect the function of heart muscle . with respect to igm seropositivity to t. gondii , it is remarkable that seroprevalence of anti - t . this finding suggests that heart disease might be related with a chronic rather than a recent infection with t. gondii . however , the high frequency of igm antibodies should be interpreted with caution since igm elisa kits have a high rate of false positive results . seroprevalence of t. gondii infection varied among heart diseases . however , this difference was not statistically significant . this might be due to a small sample size of some subgroups of specific diagnosis . logistic regression showed that seropositivity was positively associated with being born out of durango state , and with consumption of alcohol . the characteristic  born out of durango state  has been associated with t. gondii seropositivity in some previous epidemiological studies in durango including adults   and elderly people of the general population . on the other hand , to the best of our knowledge , this association has not been reported in alive people . it is unclear why subjects with alcohol consumption had a higher seroprevalence of t. gondii infection than those without alcohol consumption . it is uncertain whether subjects with alcohol consumption have behaviors that might favor t. gondii exposure . in a recent study of postmortem examinations in people who died suddenly in warsaw , poland , the frequency of t. gondii igg antibodies was higher in subjects with positive blood alcohol test than that in subjects with negative test . researchers also found the highest seroprevalence of t. gondii infection among persons who died because of suicide and with positive alcohol test . interestingly , ethanol has been involved in t. gondii invasion to and egress from the host cells , and ethanol produces a dose - dependent stimulation of microneme secretion leading to adhesion of t. gondii to host cells . furthermore , exposure of t. gondii tachyzoites to ethanol induced conoid extrusion - an event of cell invasion - without affecting parasite viability . these facts support the association of t. gondii exposure and alcohol consumption found in the present study . further research to elucidate the role of alcohol consumption with t. gondii exposure should be conducted . the current study was limited for the scanty number of certain heart diseases among the studied population . this limitation did not allow properly assessing differences in t. gondii seroprevalence among the diagnoses and functional stages of heart diseases . our results indicate that t. gondii infection is associated with heart disease and suggest that heart disease might be related with a chronic infection . results warrant for further research to determine the epidemiological impact of t. gondii exposure on heart diseases . risk factors associated with t. gondii exposure found in the present study may help to design future prevention strategies against t. gondii infection . our results indicate that t. gondii infection is associated with heart disease and suggest that heart disease might be related with a chronic infection . results warrant for further research to determine the epidemiological impact of t. gondii exposure on heart diseases . risk factors associated with t. gondii exposure found in the present study may help to design future prevention strategies against t. gondii infection .
backgroundthe parasite toxoplasma gondii causes infections all around the world 
 . infections with t. gondii are systemic and the parasite can persist in the heart muscle . 
 very little is known about the impact of t. gondii on patients with heart disease . 
 we determined the association between t. gondii exposure and patients suffering from heart diseases attending in a public hospital in durango , mexico ; the association of t. gondii exposure with socio - demographic , behavioral , and clinical characteristics of these patients was also investigated.methodsthrough a case - control study , we examined the seroprevalence of anti - t . 
 gondii igg and igm antibodies in 400 patients with heart diseases and 400 age- and gender - matched controls using enzyme - linked immunoassays . 
 in addition , we analyzed the association of patient characteristics as determined by a standardized questionnaire with t. gondii exposure by bivariate and multivariate analyses.resultsfifty-five ( 13.8% ) of 400 patients and 32 ( 8.0% ) of 400 controls had anti - t . 
 gondii igg antibodies ( odds ratio ( or ) = 1.83 ; 95% confidence interval ( ci ) : 1.15 - 2.90 ; p = 0.01 ) . 
 high anti - t . 
 gondii igg levels ( > 150 iu / ml ) were found in 28 ( 50.9% ) of the 55 positive cases and in 14 ( 43.8% ) of the 32 positive controls ( p = 0.51 ) . 
 anti - t . 
 gondii igm antibodies were found in 13 ( 23.6% ) of the 55 anti - t . 
 gondii igg positive patients and in 19 ( 59.4% ) of 32 anti - t . 
 gondii igg positive controls ( or = 0.21 ; 95% ci : 0.08 - 0.54 ; p = 0.0008 ) . multivariate analysis showed that t. gondii exposure was positively associated with being born out of durango state ( or = 2.93 ; 95% ci : 1.40 - 6.13 ; p = 0.004 ) , and with consumption of alcohol ( or = 2.04 ; 95% ci : 1.01 - 4.12 ; p = 0.04).conclusionsresults obtained in this study indicate that t. gondii infection is associated with heart disease , and suggest that heart disease might be related with a chronic infection . 
 this is the first report of an association of t. gondii exposure with alcohol consumption in this population . 
 results warrant for further research to determine the epidemiological impact of t. gondii exposure on patients with heart diseases . 
 risk factors associated with t. gondii exposure are critical to design future prevention strategies against t. gondii exposure .