Listeria

Patients who are expecting to undergo treatment with alemtuzumab are advised to avoid food potentially contaminated with listeria.

My neurologist mentioned this to me and suggested I should start excluding higher risk foods from my diet immediately.

These include:

  • Any ready-made food such as shop-bought sandwiches and salad, or quiche if it’s not thoroughly heated before eating.
  • Anything from a supermarket delicatessen or similar.
  • Any fruit or vegetables that have not been either cooked or properly washed.
  • Any food not prepared in my own kitchen, unless I have good reason to be confident about the food hygiene. So kebab shops are probably out!
  • Anything eaten “out of the fridge” such as reheated leftovers.
  • All the stuff you are supposed to avoid when pregnant – such as soft cheese, rare meat (I don’t eat meat anyway but love soft cheese…)

Sounds restrictive ūüė¶
But in reality it’s not. The advice on soft cheese is no different from the advice you get when you’re pregnant. And the rest is mostly just good food hygiene – which I don’t usually trouble too much about, beyond what I like to think of as “just common sense”, because I assume I am more or less invincible.

So I will remind myself that I will be far less invincible under alemtuzumab Рavoid cold supermarket quiche Рskip soft cheese Рand start to wash fruit and salad. Washing fruit and salad is probably the only thing I will find properly annoying.

(But Google has turned up a big and deadly listeria outbreak in the USA that was traced back to infected melons¬†(!), which I will try to keep in mind…)

Why is listeria a worry?

The incidence of listeriosis in the general population is small, partly because you need to ingest a large number (10,000,000 minimum) of listeria “colony forming units” to become infected. Those with compromised immune systems can become infected much more easily (as little as 100,0000, about 1% of what would harm a healthy person). Which means that once we’ve had alemtuzumab we’ll be much more likely to catch it. (Source.)

And, if we do get it, with a suppressed immune symptom the danger is greater and complications are a greater risk – including meningitis, septicaemia and brain infections. (Source.)

Yikes!

This paper includes observations on two case studies specific to alemtuzumab –¬†Listeria Meningitis Complicating Alemtuzumab Treatment in Multiple Sclerosis‚ÄĒReport of Two Cases

Prevention advice

Echoing the advice from my neurologist – here is the NHS advice on Listeriosis prevention.

Wikipedia (less unreliable these days than it’s cracked up to be) includes the following, similar prevention information:

The main means of prevention is through the promotion of safe handling, cooking and consumption of food. This includes washing raw vegetables and cooking raw food thoroughly, as well as reheating leftover or ready-to-eat foods like hot dogs until steaming hot.¬†Another aspect of prevention is advising high-risk groups such as pregnant women and immunocompromised patients to avoid unpasteurized p√Ęt√©s and foods such as soft cheeses like feta, Brie, Camembert cheese, and bleu. Cream cheeses, yogurt, and cottage cheese are considered safe. In the United Kingdom, advice along these lines from the Chief Medical Officer posted in maternity clinics led to a sharp decline in cases of listeriosis in pregnancy in the late 1980s.

How long do I have to keep this up?

It’s recommended that you start managing your risk well before treatment, because once infected the listeria can kick about in your system for a while. It has an incubation period of up to 70 days (source, source).

And the case-report paper referenced above includes the following:

We recommend that patients undergoing alemtuzumab treatment should avoid potentially contaminated animal and herbal food (e.g., raw milk products, sliced mushrooms, and smoked salmon) before and during alemtuzumab treatment. The duration of a diet sparing those products, however, is uncertain; currently there is no clear rationale to recommend a definite time interval.

Which means I will keep it up from now until my immune system has had a chance to recover from the treatment.

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