carcinogenesis. in particular, as reviewed by raza et al., human gastric infection with h. pylori causes epigenetically reduced protein expression of dna repair proteins mlh1, mgmt and mre11. in addition, raza et al. showed that two further dna repair proteins, ercc1 and pms2 had epigenetically severely reduced protein expression once h. pylori infection had progressed to cause dyspepsia (which occurs in 20% of infected individuals). mycobacterium tuberculosis is a risk factor for lung cancer. other bacteria one meta-analysis of serological data comparing prior chlamydia pneumoniae infection in patients with and without lung cancer found results suggesting prior infection was associated with a slightly increased risk of developing lung cancer. parasites the parasites that cause schistosomiasis (bilharzia), especially s. haematobium, can cause bladder cancer and cancer at other sites. inflammation triggered by the worm's eggs appears to be the mechanism by which squamous cell carcinoma of the bladder is caused. in asia, infection by s. japonicum is associated with colorectal cancer. distomiasis, caused by parasitic liver flukes, is associated with cholangiocarcinoma (cancer of the bile duct) in east asia. malaria is associated with burkitt's lymphoma in africa, especially when present in combination with epstein-barr virus, although it is unclear whether it is causative. parasites are also a significant cause of cancer in animals. cysticercus fasciolaris, the larval form of the common tapeworm of the cat, taenia taeniaformis, causes cancer in rats. spirocerca lupi is associated with esophageal cancer in dogs, at least within the southern united states. a novel type of case, reported in 2015, involved an immunocompromised man whose tapeworm underwent malignant transformation, causing metastasis of tapeworm cell neoplasia throughout his body. this was not a cancer of his own cells but of the parasite's. this isolated case has no substantive bearing on public health but is interesting for being "a novel disease mechanism that links infection and cancer."