8月22日，《生物学快报》（Biology Letters）在线报道了一个国际研究团队的发现，拥有猫的女性并没有比不养猫的受调查者更容易患上脑癌。
猫的排泄物中含有一种被称为弓形虫的单细胞寄生虫。科学家们发现，人类弓形虫感染率较高的国家，其脑癌的发生率也相对较高。
不过，这项发现具有争议性，而且很多科学家认为猫和脑癌之间的关联很微弱。
现在，另一个团队的研究人员相信，他们已经解决了这个问题。
科学家们调查了一个超过60万人的年龄均在50岁及以上的英国女性群体，并追踪了在平均3年的时间里有多少女性患上了脑肿瘤。
这些女性中，有18%的人，即超过10万人拥有至少一只猫。但是，那些养猫的女性并没有比不养猫的受调查者更容易患上脑癌，尽管据推测前者接触弓形虫的风险可能要大。
所以，下一次当有人刮坏了你的家具时，可以怪罪到猫的头上，不过涉及到脑癌时，还是把矛头指向别的地方吧。（生物谷Bioon.com）
doi:10.1098/rsbl.2012.0625
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Cat ownership is neither a strong predictor of Toxoplamsa gondii infection nor a risk factor for brain cancer
Marion Vittecoq1,2, Kevin D. Lafferty3, Eric Elguero1, Jacques Brodeur4, Michel Gauthier-Clerc2, Dorothée Missé1, Benjamin Roche1,5 and Frédéric Thomas1,6,*
Using a dataset including 37 countries, we recently reported a positive correlation between the national seroprevalence of the protozoan parasite Toxoplasma gondii and the national incidence of brain cancer [1]. We further established the significance of this association in a second paper showing that in France, regional mortality rates owing to brain cancer correlated positively with the local seroprevalence of T. gondii [2]. These results do not demonstrate causation but suggest that T. gondii should be investigated further as a possible oncogenic pathogen of humans. Benson et al. [3] used data from a large UK prospective cohort of middle-aged women among whom 18 per cent owned at least one cat. Comparing brain cancer incidence in women living with a cat or without any pet, they found no correlation between cat ownership and brain cancer. This is an important finding because the popular press is drawn to the headline that pet cats are a health risk to their owners. Our disagreement with Benson et al. is that their findings do not inform how T. gondii is linked to brain cancer, which was the main finding of our research. Although cats are a necessary part of the life cycle of T. gondii, multiple studies have shown that cat ownership is not a strong predictor of risk of T. gondii infection [4,5]. Contact with oocysts from cat faeces can occur through contaminated soil or vegetables [6]. Contact with contaminated soil (combined with poor hygiene) and eating unwashed vegetables are significant risk factors [6]. In addition, undercooked meat consumption has been identified as the chief risk factor for human toxoplasmosis in a number of European countries, including the UK ([7]; see [6] for a review). Thus, cat ownership is not a good proxy of the probability of being infected by T. gondii, either through oocysts originating from cats or through T. gondii asexual stages. So, while cats are a key host for T. gondii and T. gondii seems to be a risk factor for brain cancer, cat ownership is not necessarily a significant risk factor for brain cancer, at least not unless other risk factors are accounted for statistically. To conclude, the study of Benson et al. should be reassuring to cat owners, but it does not test whether T. gondii affects risks of brain cancer. Clearly, what is now needed to assess the role of T. gondii in brain cancer risk are studies that compare the seroprevalence of T. gondii in individuals with brain cancer with matched controls.
