Increased incidence of traffic accidents in Toxoplasma-infected military drivers and protective effect RhD molecule revealed by a large-scale prospective cohort study

Department of philosophy, Faculty of Science, Charles University, Prague, Czech Republic.
BMC Infectious Diseases (Impact Factor: 2.61). 02/2009; 9(1):72. DOI: 10.1186/1471-2334-9-72
Source: PubMed

ABSTRACT

Latent toxoplasmosis, protozoan parasitosis with prevalence rates from 20 to 60% in most populations, is known to impair reaction times in infected subjects, which results, for example, in a higher risk of traffic accidents in subjects with this life-long infection. Two recent studies have reported that RhD-positive subjects, especially RhD heterozygotes, are protected against latent toxoplasmosis-induced impairment of reaction times. In the present study we searched for increased incidence of traffic accidents and for protective effect of RhD positivity in 3890 military drivers.
Male draftees who attended the Central Military Hospital in Prague for regular entrance psychological examinations between 2000 and 2003 were tested for Toxoplasma infection and RhD phenotype at the beginning of their 1 to 1.5-year compulsory military service. Subsequently, the data on Toxoplasma infection and RhD phenotype were matched with those on traffic accidents from military police records and the effects of RhD phenotype and Toxoplasma infection on probability of traffic accident was estimated with logistic regression.
We confirmed, using for the first time a prospective cohort study design, increased risk of traffic accidents in Toxoplasma-infected subjects and demonstrated a strong protective effect of RhD positivity against the risk of traffic accidents posed by latent toxoplasmosis. Our results show that RhD-negative subjects with high titers of anti-Toxoplasma antibodies had a probability of a traffic accident of about 16.7%, i.e. a more than six times higher rate than Toxoplasma-free or RhD-positive subjects.
Our results showed that a common infection by Toxoplasma gondii could have strong impact on the probability of traffic accident in RhD negative subjects. The observed effects could provide not only a clue to the long-standing evolutionary enigma of the origin of RhD polymorphism in humans (the effect of balancing selection), but might also be the missing piece in the puzzle of the physiological function of the RhD molecule.

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    • "It has been suggested that this polymorphism can be stabilized when the disadvantage of carriers of the locally rarer allele is counterbalanced by higher viability of their heterozygote children or by another form of frequency-dependent selection[6]. In the past seven years, several studies have demonstrated that Rhesus positive and Rhesus negative subjects differ in resistance to the adverse effects of parasitic infections, aging, fatigue and smoking78910111213. A recently published cross sectional study performed on a cohort of on 3,130 subjects showed numerous associations between Rh negativity and incidence of many disorders. "
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    • "Parasitism is one of the most important driving forces in ecology because it affects the distribution and abundance of organisms on local and global scales (Piersma, 1997; Tompkins & Begon, 1999) and many ecosystem processes (Marcogliese, 2004). Parasites potentially affect the life and death of essentially every organism (Price, 1980), from insects (Worden, Parker & Pappas, 2000) to humans (Fl egr et al., 2009). Accordingly, parasite–host systems are a subject of coevolution, with many particular adaptations for successful parasitism or, conversely, for the avoidance of parasitism (Combes, 2001). "
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    • "Our findings support previous observations in this new but growing research area [14-16]. Taken together, this study and previous findings suggests that the increased risk of traffic accidents could possibly be the consequence of acute toxoplasmosis, rather than the increasing effect of latent toxoplasmosis, a hypothesis previously proposed by studies conducted in the Czech Republic and Turkey [14-16]. "
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    ABSTRACT: Background The prevalence of toxoplasmosis in the general population of Guadalajara, Mexico, is around 32%. Toxoplasmosis can cause ocular lesions and slowing of reaction reflexes. Latent toxoplasmosis has been related with traffic accidents. We aimed to assess the prevalence of anti-Toxoplasma gondii antibodies and visual impairments related with traffic accidents in drivers from the metropolitan Guadalajara. Methods We prospectively evaluated the prevalence of IgG and IgM anti-T. gondii antibodies in 159 individuals involved in traffic accidents, and in 164 control drivers never involved in accidents. Cases of toxoplasmosis reactivation or acute infection were detected by PCR in a subset of 71 drivers studied for the presence of T. gondii DNA in blood samples. Ophthalmologic examinations were performed in drivers with IgG anti-T. gondii antibodies in search of ocular toxoplasmosis. Results Fifty-four (34%) traffic accident drivers and 59 (36%) controls were positive to IgG anti-T. gondii antibodies (p = 0.70). Among the 113 seropositive participants, mean anti-T. gondii IgG antibodies titers were higher in traffic accident drivers than in controls (237.9 ± 308.5 IU/ml vs. 122.9 ± 112.7 IU/ml, respectively; p = 0.01 by Student’s t test, p = 0.037 by Mann–Whitney U test). In multivariate analyses, anti-T. gondii IgG antibody titers were consistently associated with an increased risk of traffic accidents, whereas age showed an inverse association. The presence of IgM-anti-T. gondii antibodies was found in three (1.9%) subjects among traffic accident drives, and in two (1.2%) controls. Three (4.2%) samples were positive for the presence of T. gondii DNA, all among seropositive individuals. No signs of ocular toxoplasmosis were found in the entire cohort. Moreover, no other ocular conditions were found to be associated with the risk of traffic accidents in a multivariate analysis. Conclusions Anti-T. gondii antibody titers are associated with the risk of traffic accidents. We could not determine any association of ocular toxoplasmosis with traffic accidents. Our results warrant further analyses in order to clarify the link between toxoplasmosis and traffic accidents.
    Full-text · Article · Oct 2013 · Parasites & Vectors
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