Science Questions

Does leprosy interact with TB and other diseases?

Sun, 30th Jan 2011

Listen Now    Download as mp3 from the show Leprosy: The Low Down

Question

asked:

I've heard that the BCG vaccine can actually give you some protection against leprosy – that's the vaccine against TB. So, what's the relationship between leprosy and TB in the past?

Answer

Charlotte -   Well, we see evidence for both leprosy and tuberculosis in skeletons, and the suggestion is that, in Europe, leprosy declines [after] about the 14th century while tuberculosis takes off as a major infectious disease and there's a belief that that's linked to increasing urbanisation and close-living between individuals. 

Leprosy and tuberculosis are both caused by Mycobacteria, but different species; so Mycobacterium leprae versus Mycobacterium tuberculosis; and there’s a suggestion that increasing exposure to tuberculosis will reduce the chances of contracting leprosy.  And it’s actually quite interesting to see that evidence in skeletons early-on in that medieval period tends to be the low-resistant form of the disease.  People are expressing the disease in their skeletons very obviously and as time goes by when you get into the 16th and 17th centuries, they're getting a less severe form of leprosy, something called tuberculoid leprosy, suggesting that they're more resistant to the bacteria.  But there’s also less evidence of leprosy during those periods too.

Diana -   I suppose one of them might kill you a bit faster than the other....

Charlotte -   Yes and in fact today, one of the major causes of death in people with leprosy is tuberculosis.

Ben -   Well that of course, brings me on to the modern clinical perspective.  Diana, do you see these infections together very often?

Diana L. -   You certainly see them together, but not very often, no.

Ben -   And are there any other interactions between different diseases?  Of course, there are things like HIV which are in the same parts of the world as you were saying, we still see leprosy.  That knocks your immune system almost totally dead.  Does that mean that leprosy runs absolute riot?

Diana L. -   We were very worried at the beginning of the HIV epidemic, that we would see a lot more leprosy and a lot worse leprosy cases.  But what’s actually happened is that having HIV doesn’t seem to make you more likely to get leprosy. 

Paradoxically, what we have seen, now that people have antiretroviral treatment, is that when they do get leprosy, they get leprosy with a lot more immune activation and the inflammation that I was talking about earlier, occurs in a very florid form, and it’s quite difficult to switch off again.

Ben -   So it actually complicates the issue quite a lot.

Diana L. -   Yes, it does.

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