Saturday, August 23, 2008

Exercise viewed from the relative safety of the couch

We are constantly urged to get out and do some exercise. This can be as simple as walking to work or doing a workout in the gym. However, walking at this time of the year in New Zealand has the distinct disadvantage that you can arrive at work looking like a drowned cat. The gym is less of a problem in that respect, but just pumping iron or running on a treadmill can get mighty boring.

What about mountain or cross-country biking? That can get your heart rate up and can be very exciting. There can also be a downside. Campylobacter.

There, I bet you immediately thought “What has mountain biking got to do with chilled chicken?” Certainly, we have heard a lot about Campylobacter and chicken meat over the last couple of years, much of it not good news. But this piece is not about transmission in poultry.

On July 5th and 6th this year, a mountain bike marathon was run on Builth Wells, Wales. The two-day event attracted 947 participants, up to 160 of whom became ill after the event. The conditions were very muddy and the course was contaminated with “sheep slurry”. The result was that contaminated mud splashed over the riders and their gear. An investigation* revealed that accidental ingestion of mud was the most statistically significant risk factor. Consumption of energy drinks and energy bars from feed stations was also associated with infection. It is easy to see how these factors might be linked – riders covered in mud would contaminate their drink bottles and dirty hands could transfer mud to food. Only the competitors became ill – support crew and visitors were not involved.

The running of this type of event over muddy agricultural land makes it almost inevitable that competitors would be exposed to zoonotic infectious agents, such as Campylobacter, Salmonella and Listeria.

It is very tempting to ask whether the high incidence of campylobacteriosis in new Zealand could be at least partly explained by our passion for strenuous outdoor sports that involve getting muddy and the high proportion of the country given over to farming. We already have some data on risk factors in New Zealand see
Perhaps it would be worth including questions in the surveys about contact with mud and activities such as cross country running or rugby.

* Griffiths, S. et al (2008) Preliminary report of the epidemiological investigation into the outbreak of diarrhoeal illness in Mountain Bike Marathon participants, Builth Wells. National Public Health Service for Wales

Friday, August 22, 2008

A hard course to row: the colossal task of making food safe in China

The heartbreaking spectacle of New Zealand Olympic rower Mahe Drysdale pulling to the front of the field in the finals of the single sculls and then fading only 250 m from the finish will be hard to forget, no matter which country you support. We have all experienced the debilitating effects of food poisoning and some of us know how it feels to go beyond our physical limits, though perhaps at a much lower level of competition.

Drysdale apparently suffered a food borne infection that left him unable to eat and severely dehydrated. These are common sequelae of food poisoning. The normal way of dealing with this is rest and careful intake of suitable rehydration fluids. To go out and exercise strenuously in high temperatures would definitely not be recommended. That he did is a testament to Mahe’s true grit and determination.

It seems that Drysdale was not the only Olympian to suffer from food poisoning. About 15% of the U.S. track team also became ill, despite their team managers having taken precautions to protect them. Large quantities of food were imported into China from the United States to reduce the risk from eating local food. However, the track team spent a period of training in Dalian, 300km from the Olympic Village and did not have access to the imported food. The infections could not be attributed definitively to food, according to a chef brought from the U.S. to prepare the team’s meals. He suggested that water used to prepare the food might have been the source of contamination. The team doctor described the illnesses as “normal stomach bugs… not widespread… not out of the ordinary for international trips”.

Whatever the explanation, to find 15% of a very healthy population succumbing to gastro-intestinal illness in such a short period suggests to me a food or water borne infection or indirect contact with infective faecal matter, perhaps via an unclean restroom surface. (Norovirus is often transmitted in this way, though at this stage there is no indication that the team contracted Norovirus).

It is actually quite difficult to avoid all possible sources of infection. Drinking only beer, wine, hot tea or sealed bottles of water and eating only hot foods helps, but also means that you miss many wonderful culinary experiences. Even fresh fruit may have been washed in contaminated water before being sliced and this has sometimes been shown to be the vector for intestinal pathogens.

China has tried to provide safe food for teams and spectators at the Olympics. Unfortunately, their approach illustrates the enormity of the task and the collateral damage of draconian measures. John Garnaut, writing in the Sydney Morning Herald on 15th August, told of chefs and hoteliers across Beijing being forbidden to purchase foods from their normal suppliers. Fresh and processed foods could be bought only from a Government-approved list of 64 suppliers. This effectively gave those favoured suppliers a licence to print money, so costs have gone up by as much as 1200 per cent. Though it has avoided food scandals so far, there is no guarantee that food is any safer.

In a parallel to the problem of fake luxury goods, it will require a long process of education and rooting out of corrupt food suppliers - those who use substandard materials, illegal chemicals and inadequate processes to make a fast buck - before we can be reasonably sure that food in China will be as safe, microbiologically and chemically, as our food here in New Zealand.

Wednesday, August 13, 2008

Coming soon to a store in New Zealand?

I have written several times about the potential hazards of consuming raw milk and raw milk products. Search this site using keyword “raw milk” for other posts.

Currently the New Zealand food regulations allow only three particular hard and very hard Swiss cheeses, extra-hard Parmesan style grating cheeses like Grana Padano, Pamigiano Reggiano, Romano, Asiago and Montasio and the semi-hard Roquefort cheese. Local manufacture of similar products is not permitted. See

The New Zealand Food Safety Authority is now asking for submissions on a proposed framework for the manufacture, importation and sale of raw milk products. See

Aficionados of raw milk cheeses will applaud this move. It is quite possible to produce safe cheeses without pasteurization of milk and, provided that the resulting products are safe, manufacturers and consumers should be given the opportunity to make and taste them. However, the process requires strict control of animal health and rigorous processing hygiene - good regulations and inspection will be needed.

Even the cheesemakers are divided on the desirability of permitting the manufacture of raw milk cheeses. One, quoted in the Otago Daily Times on 11th August 2008 said that cheeses made from non-pasteurised milk could be “lovely", but they could also be “bloody awful stuff". The explanation for this is that pasteurized milk contains only heat resistant bacteria, such as some Streptococcus species and sporeformers. The cheese is made by inoculating the pasteurized milk with known cultures of "starter bacteria", which will produce lactic acid to coagulate the milk protein and produce a curd. When cheese is made from unpasteurized milk, the bacteria present in the raw milk may grow beside the starters. This can result in more complex flavours, but can also lead to variation between batches. Unfortunately, the non-starter bacteria can sometimes cause disease, such as salmonellosis and campylobacteriosis, or may produce toxins, such as staphylococcal enterotoxin.

Softer raw milk cheeses represent a greater risk to the consumer because of their higher water activity, which allows some pathogens to survive and grow. Control over the milk production and handling and the cheesemaking process itself must therefore be absolutely spot-on for these products.

Under the proposed framework, raw milk products would be categorised according to the risks they present. Category one products would pose no greater food safety concerns than pasteurised cheeses, such as Parmesan-style raw milk cheeses. Category two products would pose a low risk for the general population but vulnerable consumers with reduced immunity might be at greater risk. Products in this category would include semi-hard Roquefort. Category three would cover those raw milk products that cannot currently be produced to an acceptable level of safety for the general population. (As far as I know, this category has not yet been defined more closely).

Assuming that the consultation process approves the proposed framework, locally produced raw milk cheeses and other raw milk products may soon hit the delicatessen and specialty store shelves. It may be too soon to expect these products to be sold in supermarkets.

Would I eat raw milk cheese? Probably not until the framework were shown to be working well and the suppliers had built up a record of selling safe products. Even then, I would eat only the hard or semi-hard varieties. Would I give it to my little granddaughter? Not a chance! Raw milk products are not for little children or the immunocompromised.