Researchers investigate possible malaria protection in Pacific

Transcript

A team of New Zealand researchers are investigating a possible link between gout and protection against malaria in Pacific communities.

Gout causes severe pain, often in the big toe, and is the result of high levels of uric acid, or urate, which can form crystals that lodge in joints.

Otago University PhD student, Anna Gosling, says the disease is prevalent among Pacific Islanders and Maori people, who also have high levels of uric acid.

She told Amelia Langford about her research including a planned trip to PNG's Kavieng Island in New Ireland province in June.

ANNA GOSLING: What the research we've been doing recently is looking at serum urate levels, so that's a chemical in your blood. And when this chemical gets high, it makes you more likely to develop the gout disease. So what has been found is that Pacific Islanders in particular, and Maori and Polynesians, have really quite high levels of this serum urate in their blood which makes them more likely to develop disease. And it's something we see throughout the Pacific. And so we've been looking at reasons why they might have these high levels compared to people of other ancestral backgrounds, like you know, Europeans.

AMELIA LANGFORD: And what is this connection you've found between gout and protection against malaria?

AG: Well one of the things that we were looking at, you know, to try and answer these reasons why this urate in the blood is so high is looking at the roles of urate for normal human function. And actually it plays a pretty important role in our immune systems. So when you get sick your immune system has to fight off the pathogen. So there has been quite recently research to suggest that urate increases in the blood during malarial infection. And since malaria is endemic throughout Papua New Guinea and Indonesia and Vanuatu, and areas that Pacific Islanders would have travelled before they got out to their various islands, there's a possibility that high levels of urate in their blood was selected for, it gave them an advantage when faced by malaria, which actually even today is one of the highest causes of deaths in some of these countries where you don't have such good medical systems as we do here in New Zealand.

AL: So even now, today, people from Polynesian countries are protected, have a natural protection against malaria to some degree?

AG: Well in Polynesia, well Polynesia has actually never had malaria itself, the islands are kind of too far apart for the mosquitos, it's a mosquito-borne disease, to get out to. And well, traditionally called Melanesia, but what we now called near Oceania, where the islands are pretty close together, that's where you see these high rates of malaria of transmission. When people go out into the wider Pacific, the mosquitos and malaria parasite itself just couldn't survive, well it didn't possibly get there. So we're not entirely sure for certain whether it does make you more likely to survive, it's at this point just a working hypothesis which we're hoping to test soon. We're hopefully going to do some field work in Papua New Guinea to test it. But it seems like an interesting idea, and in some ways it is quite logical, that you know, high levels of this urate must have been advantageous somehow, or otherwise why would it develop.

AL: As you say, this is testing a hypothesis at this point, but there is a possibility. What sort of significance could this have down the track if it is proved correct?

AG: I think mostly what we're trying to do here is to take some of the stigma away from gout as being something that is the fault of the sufferer. Because there has been an attitude to a certain degree that it's a disease which is brought on my bad behaviours. So drinking too much beer and spirits, and smoking, and eating really sugary and bad foods, whereas there is definitely evidence that there is a genetic pre-disposition for this and while you can change your lifestyle to a certain degree, some of it is actually just poor, well not necessarily poor luck, but it's down to who your ancestors were and where they came from, and what conditions they faced in the past. So these traits that were probably quite useful in the past are not necessary for our current lifestyle so they're having a slightly different effect.

AL: So is gout quite a problem for Pacific communities?

AG: Yes, it is. And it does result in time having to be taken off work, because it is a very painful disorder.

AL: I should be clear, so having this high level of uric acid wouldn't mean they were immune from malaria?

AG: No, not necessarily. But our hypothesis is that having the high urate would mean that your immune system figures out that you have malarial parasites in you, so you're infected with malaria more rapidly and mount a response to get rid of the parasite faster. Because part of the infectious cycle of malaria, is that, first it invades your liver, and then it gets into your blood cells, your red blood cells, and just through the normal cycle of malaria it breaks blood cells down to make more parasites but during this process it creates uric acid, and so the levels of urate in your blood increase during infection. So our hypothesis is that if you have already elevated levels of urate, it takes less of your red blood cells to be broken down for your immune system to be like, hey, something's wrong here, we should probably stop this.