Tag Archives: Hygiene

Three Hits Hypothesis

Quite a lot of diseases are brought about by the conflation of two factors. Mice infected with certain herpes viruses suffer no ill-effect unless a helminth infestation supervenes. Oral allergy syndrome arises when a certain pollen interacts with certain foods (usually raw fruits, vegetables and nuts). The hygiene hypothesis says that lack of exposure to certain gut bacteria sensitises the body to allergic reactions to a range of environmental allergens. The pathway for disease involves three hits:

Genetically predisposed person –> Exposure 1 –> Exposure 2 –> Disease.

An intriguing example of a three-hit condition is the severe disease of children – Burkitt’s lymphoma. This cancer arises in germinal centres of lymph nodes in the neck. It is known that Epstein-Barr (EB) virus infection is necessary for endemic Burkitt’s lymphoma to develop because it prevents apoptosis (cell death) when certain mutations occur in the cell. But endemic Burkitt’s lymphoma only occurs in the malaria belt, and why this is so has been a mystery until the last few years. Now we know that the malaria parasite Plasmodium falciparum ‘upregulates’ an enzyme that causes mutations in DNA in lymph cells. These mutations are a normal part of antibody production since rearrangements of chromosome segments is necessary for antibody specificity. But in people with falciparum malaria, the effect ‘spills over’ to cause mutations of cancer genes. The double hit of EB plus malaria sets the scene for carcinogenesis.[1] Why in the neck – perhaps because lymph cells in the necks of children work particularly hard eradicating throat and ear infections, in which case there is a ‘four hits’ hypothesis!

— Richard Lilford, CLAHRC WM Director

References:

  1. Thorley-Lawson D, Deitsch KW, Duca KA, Torgbor C. The Link between Plasmodium falciparum Malaria and Endemic Burkitt’s Lymphoma—New Insight into a 50-Year-Old Enigma. PLoS Pathog. 2016; 12(1): e1005331.

Fine Dining and Fine Hygiene are Negatively Correlated

A recent study shows that restaurants rated highly in food guides are associated with a greater overall risk of foodborne gastrointestinal diseases outbreaks than your run-of-the-mill restaurant.[1] However, the ‘high-end’ restaurants also score more highly on the Food Agency Inspection visits. So why do the posh restaurants generate more GI diseases than their more mundane peers despite better hygiene in the restaurants with the best food? The high disease risk in highly rated restaurants probably comes from the nature of the food served (e.g. oysters) and cooking methods (e.g. low temperatures to produce chicken liver parfait). So the risk is real, but worth running!

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Kanagarajah S, Mook P, Crook P, Awofisayo-Okuyelu A, McCarthy N. Taste and Safety: Is the Exceptional Cuisine Offered by High End Restaurants Paralleled by High Standards of Food Safety? PLoS Curr Outbreaks. 2016.