Many cancers caused by germs

Vaccines can help to prevent
some cancers Cancer is a mysterious disease which cause(s) has been a source of concern to medical researchers. The causes of some cancers, however, may not be as mysterious as they look. Sade Oguntola reports that some cancers are attributable to germs.

Many people would be surprised to learn that cancer, popularly understood as a result of mutations or mistakes within the genetic code in cells, can be caused by germs such as viruses, bacteria and parasites. Conservatively, 15 to 20 per cent of all cancers are caused by infections and the number could be larger – maybe double, according to Dr. Andrew J. Dannenberg, director of the Cancer Centre at New York Presbyterian Hospital. Unfortunately, people are unaware of the significance of germs as potential, though preventable, causes of cancer despite several studies confirming this. Cancers that have been linked with germs thus include:

Childhood cancers
The University of Newcastle-led team looked at 3,000 childhood cancers in 0 to 14-year-olds from 1954 to 1998 and according to the European Journal of Cancer reported that there were compelling evidences that infections such as colds may trigger childhood cancers. The team found a pattern emerged whereby the cancers repeatedly occurred at similar times and geographical locations, known as “space-time clustering”. Lead researcher, Dr Richard McNally, said: “We found that place of birth was particularly significant, which suggests that an infection in the mother while she is carrying her baby, or in a child’s early years, could be a trigger factor for the cancer. “These could be minor, common illnesses that are not even reported to the GP, such as a cold, mild flu or a respiratory virus.”

Cervical cancer
Cervical cancer has been proven to be due to a virus called the Human Papilloma Virus (HPV). Prof. Isaac Folorunsho Adewole, a consultant obstetrician and gynaecologist at the University College Hospital (UCH) Ibadan, said this at a lecture he gave on cervical cancer in honour of Prof. Jide Ajayi, a foremost breast cancer expert at the Olabisi Onabanjo University Teaching Hospital, Sagamu. Screening with a pap test can find changes in the cervix before they turn into cancer, or detect cancer when it is still at a very early stage. In fact, this type of screening and vaccination with HPV vaccine is credited with reducing both the incidence and death rate from cervical cancer.

Stomach cancer
Many stomach cancers are related to an infection with a bacterium called Helicobacter pylori. This infection probably comes from food and water and is also responsible for stomach ulcer. The 2005 Nobel Prize in Physiology or Medicine recognised the work, which showed H. pyloric infection as an important cause of peptic ulcer disease, including stomach cancer.

Liver cancer
Worldwide, most cases of liver cancer are caused by infection by the hepatitis B or C virus explained Dr. Abiodun Otegbayo, a consultant, gastroenterologist at the UCH. Vaccinating people against hepatitis B could prevent cases due to that virus. Although there is no vaccine for hepatitis C, measures to prevent people from passing the infection to others could have an impact. These include screening blood donors for the disease, safer sex practices and using clean needles in medical procedures. The disease can also spread through injecting drugs.

Oral cancer
HPV increasingly causes oral cancer in men. The HPV virus now causes as many cancers of the upper throat as tobacco and alcohol. This is probably due to increase in oral sex and the decline in smoking, researchers said in the Journal of Clinical Oncology. Aside HPV being the leading cause of cervical cancer in women, it also can cause genital warts and cancers of the penis and the anus in men. Previous research by Dr. Maura Gillison of John Hopkins University and others established HPV as a primary cause of the estimated 5,600 cancers that occur each year in the tonsils, lower tongue and upper throat.

Bladder cancer
It is caused by chronic infection with Schistosome parasites also known as bilharzias. This parasitic disease that leads to chronic ill health has been associated with urinary schistosomiasis and a form of cancer of the bladder in some regions according to a study in the January edition of the journal, Clinical Microbiology Reviews. In Egypt, schistosomiasis linked with cancer is the primary cause of death among men aged between 20 and 44 years. In some regions of Africa where Schistosoma haematobium is prevalent, the incidence of cancer of the bladder linked to schistosomiasis is 32 times higher than the incidence of cancer of the bladder in the USA.

Burkitts lymphoma, a cancer of B-lymphocytes, the lymphocytes that the immune system uses to make antibodies, is caused by Epstein-Barr virus. *Nasopharyngeal cancer, an Epstein-Barr virus associated cancer, is the most common head and neck cancer in Southern China. The WHO World Cancer Report (2003) provides clear evidence that quiting smoking, balanced diet and infection control can prevent one third of cancers and another third can be cured.

In addition, Professor Alan Rickinson, from the University of Birmingham believes that, “studying the association between infectious agents and human cancers is extremely important because, in such cases, infection represents one defined link in the chain of events leading to cancer development.

“Knowing this helps us to trace other links in the chain and to understand how the whole chain fits together. More importantly, if we can break the chain by preventing the infection through vaccination, then we can prevent the cancer from developing.”

Also, Professor John Toy, medical director of Cancer Research UK, said it was important people understood it was not possible to “catch” cancer in the same way as a cold or flu virus. According to him, “As today we successfully vaccinate against infectious diseases so we shall soon be able to vaccinate against certain types of cancer.”

The knowledge that some germs can cause cancer had led to some action being taking by experts. In the same vein, Dr. Judith Sobowale, an expert in infectious diseases and the Preceptor, The Starfish Project Centre for Special Studies, Sabo, Sagamu said it is on the basis of this that HIV patients are usually asked to get tested for HPV so that if any sign of the infection is noticed it could be treated early before it progresses to cervical cancer.

Professor Taye Ijaduola, a consultant Ear, Nose, Throat surgeon at UCH, said much as germs, including viruses, can be linked to some cancers, science is yet to conquer most viruses as evidenced by HIV that is now on the scene. According to him, viruses are a big challenge to medical science and once your immunity is low, these germs easily express themselves.