%0 Journal Article
%T Gastrointestinal Neoplasia Associated with Bowel Parasitosis: Real or Imaginary?
%A Michael R. Peterson
%A Noel Weidner
%J Journal of Tropical Medicine
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/234254
%X Several parasitic species are well known to have carcinogenic properties, namely; Schistosoma hematobium (squamous cell carcinoma of the bladder) and the liver flukes Opisthorchis and Chlonorchis (cholangiocarcinoma). A large number of parasites are known to colonize the gastrointestinal tract. We sought to review the evidence that implicates these parasites in gastrointestinal neoplasia. Schistosoma japonicum, which is endemic primarily in east Asia, has been shown in multiple studies to convey a mildly increased risk of colorectal adenocarcinoma. The data supporting a causative role for Schistosoma mansoni in colorectal or other neoplastic processes are less convincing, limited primarily to small case-control studies and case series. Reports of possible associations between other gastrointestinal parasites (e.g., E. histolytica and A. lumbricoides) and neoplasia may be found in the literature but are limited to individual cases. We conclude that, other than S. japonicum and to a lesser extent S. mansoni, there is little evidence of an association between gastrointestinal parasites and neoplasia. 1. Introduction A wide variety of parasites are known to cause disease in the human gastrointestinal tract, including some species that are very prevalent over a large geographical area. Human parasites are traditionally divided into two broad groups, protozoa and helminths. The phylum protozoa includes a number of gastrointestinal parasites, with some notable members such as Entamoeba histolytica, Giardia lamblia, Cryptosporidia, and Trypansoma cruzi. The multi cellular helminths are further divided into three groups, cestodes/tapeworms (e.g., Taenia solium and Diphyllobothrium latum), nematodes/round worms (e.g., Ascaris lumbricoides, Strongyloides stercoralis, and Enterobius vermicularis), and trematodes/flukes (e.g., Schistosoma japonicum and Schistosoma mansoni). There has long been scientific interest in exploring the possibility of infectious causes of cancer, including bacterial, viral, and parasitic causes. Mathematical modeling has estimated that approximately 16% of cancers throughout the world may be attributable to infection [1]. The fraction of this that is attributable to parasitic infection is currently unknown. Historically, one of the first proposed links between parasitosis and cancer garnered Dr. J. A. G. Fibiger the Nobel Prize in 1926 for his work demonstrating that mice infected with the nematode Spiroptera later developed stomach cancer. This work was later debunked on at least two levels. It was shown that the risk of ¡°cancer¡± was only
%U http://www.hindawi.com/journals/jtm/2011/234254/