LEIGH SALES, PRESENTER: Ask any farmer and they'll tell you that feral pigs need eradication because they carry disease and destroy crops.

Unlike efforts to control other types of feral animals, there's a growing subculture of people who enthusiastically do it for free.

But does that put pig hunters at risk from the very diseases farmers want gone?

Reporter Andy Park went to one of Australia's biggest pig hunting competitions to find out.

ANDY PARK, REPORTER: Night is falling fast in central Queensland.

(Shots of country landscapes at dusk)

Where later tonight, in the freezing cold and remote darkness, blood will spill.

(A man in an orange jacket lets dogs out of a ute)

STEVE REEVES, PIG HUNTER: They're sneaky. They get under cover before you can see them.

ANDY PARK: How long have you been pig hunting for?

STEVE REEVES: Most of my life. Same as my father when I was a little fella.

ANDY PARK: Steve goes hunting with three dogs, a mate and one long knife.

JAMIE PETRIE, BIG BOAR CQ: Steve Reeves is obviously one of the best guys in Queensland for sure in terms of hunting pigs.

ANDY PARK: Why is it important to control pigs?

STEVE REEVES: Just to control disease and the simple fact they breed like rabbits and destroy crops and foul up the waters.

ANDY PARK: But that doesn't fully explain why he and many others like him hunt for free most nights of the week.

(Night vision footage of a family of feral pigs)

JAMIE PETRIE: I think what drives the hunter is the thrill of the chase. It's no different to a young boy or girl wanting to find a boyfriend or a girlfriend.

STEVE REEVES: There's cattle and the forage and that down here, so we'll just poke around nice and steady, so nothing is spooked or anything like that. And the dogs will let us know when there's pigs.

ANDY PARK: Like a fisherman, Steve and his favourite dog Turbo play a silent, patient game.

STEVE REEVES: We've all got our little secret spots and just keep on top of them. Most of the time you won't see anything. They'll smell them and let them off and away they go.

ANDY PARK: Do you think he's on to something?

(Turbo looks around alertly)

STEVE REEVES: Yeah. He'll be tracking a boar.

He's on. Let's go.

ANDY PARK: Yeah?

ANDY PARK: Yep.

ANDY PARK: Hunters like these are out all over central Queensland tonight ahead of the weekend's festivities.

(Dog howls)

(Shot of GPS tracker on Turbo)

(Sound of pigs grunting as the car moves off)

(Aerial shot of country showground by day with lots of families and utes)

Steve Reeves is aiming to win one of Australia's largest annual pig hunting competitions, organised by Jamie Petrie.

(Utes driving slowly with huge pigs strung up on the back)

(Man speaks indistinctly over a microphone)

SPEAKER: Guys, back to the update of the scoreboard. We'll hand all the prizes out in a little bit. So we'll just dial through this...

JAMIE PETRIE: I didn't walk into a bar and grab the four drunkest blokes in the bar and say 'let's put a pig comp together', you know?

OFFICIAL (weighing a dead pig): 90... 90.3.

ANDY PARK: More than 300 pigs have been brought from all over the region to the tiny town of Jambin, and the weigh in will decide this year's Big Boar King and Queen.

JAMIE PETRIE: The joy of this year is that we have introduced the family ticket, so we try to encourage a more family fun environment.

SPEAKER: Still a couple hanging on the edge....

ANDY PARK: The hunt raises thousands for the local school, and is a rare glimpse at the sheer breadth of the pig problem in the region, a feral pest which destroys crops and carries disease.

JAMIE PETRIE: Well, a comment was made by a local grazier, walked past these pigs and said 'We should have this competition every week'.

ANDY PARK: It might not be everyone's cup of tea, but here in central Queensland pig hunting is a very popular pastime - and it's a completely legal one if done with the land owner's permission, which in turn keeps the feral population down.

These things can be dangerous to catch. You see, the health hazards don't just end there.

ALISON LYNCH: Clarkie? Yeah, no, he was the world's greatest larrikin. He was a top bloke. He was fantastic.

(Photograph of Alan Clarke)

ANDY PARK: Cattle farmer Alan Clarke had just turned 50 in 2011 when he began to feel unwell. Alison Leech was his best mate.

ALISON LYNCH: He sort of had like flu-like symptoms. Then glassy eyes. And just felt pretty crook.

ANDY PARK: Alan was not even a pig hunter, but he had been in contact with soil soaked in animal urine.

ALISON LYNCH: His body ballooned. And he bled out every orifice and they had to give him blood.

At the time, they were grasping at any information. They didn't know what they were dealing with.

And so afterwards, after his passing, the post-mortem put it down to, it was lepto.

ANDY PARK: Lepto, or Leptospirosis, claimed the life of Alan Clarke, who died at Ipswich in 2011. It's a disease transmitted by feral pigs, cattle and rats.

DR BRUCE CHATER, RURAL CLINICAL SCHOOL: Leptospirosis is a pretty nasty illness.

ANDY PARK: Country GP Bruce Chater was on hand for the last major outbreak of leptosprirosis.

DR BRUCE CHATER: Eighty per cent of the town was covered in floodwaters for eight days. So it was a perfect environment for lots of mud.

And it was probably the urine from rats, in particular, probably and pigs.

So you might think you have the flu. That's the difficulty. You've got a headache. You've got aches and pains and you've got fevers.

But if you let it go on it can actually give quite serious complications, including liver failure, kidney failure, and heart attacks and heart failure.

(Long shot of a little pig trotting along the edge of a bare paddock)

ANDY PARK: On average, cases, which can be contacted through animal urine, have been growing in Queensland. Over all, there have been 50 reported cases this year.

DR BRUCE CHATER: A lot of the cases are from recreational stuff, so it's people being out in the bush.

ANDY PARK: Research by Queensland's Murray Darling Committee shows a quarter of all feral pigs carry the disease. Pig populations can explode unchecked, doubling in a year, putting humans at risk of a number of animal-borne diseases.

(Three men hogtying and trapping a small pig)

DR BRUCE CHATER: There needs to be more awareness of both leptosprirosis, Q fever and brucellosis amongst rural people and also amongst rural doctors.

ALISON LYNCH: I didn't think that it was lepto because I was thinking that we're not a Third World country. Like, you don't die of that in Australia.

SPEAKER (at Pig hunting event): That's a great effort, guys. Over 500 pigs this year, which is an extraordinary effort.

JAMIE PETRIE: I'm pretty sure there's still a lot of hunters out there that probably aren't aware of the diseases that can be contracted, lepto and bruco.

ANDY PARK: Is that a problem, do you think?

JAMIE PETRIE: Look, I don't want to say it's not a problem because it obviously is.

ALISON LYNCH: They're not going out there thinking, 'Gee, I hope I don't get lepto today'.

(Still of Steve Reeves standing between two enormous black boars hung up)

ANDY PARK: At the weigh-in, the disappointment is real for the region's best hunter, Steve Reeves, who this year missed out on being crowned king of central Queensland.

STEVE REEVES: I'd like to see someone win it that has never won nothing, though.

ANDY PARK: Which was taken out in royal style by Top Trotter Josh Allen.

JAMIE PETRIE: 138.4 kilo boar...

JOSH ALLEN: This is quite good, this is my first year and I've never gone in a pig hunting contest before.

ANDY PARK: How careful are you when you're dressing a pig?

(Camera pans across bloody carcasses of hung pigs)

JOSH ALLEN: Oh, it probably doesn't really cross my mind. But it is out there in some pigs. And it can get quite serious. I suppose it's just a risk you take.

ANDY PARK: And this year's Big Boar Queen won't be taking any risks either.

What are your duties as the Queen - do you know what it entails?

RHIANA MASON, QUEEN OF CQ BIG BOAR: No, I can't even celebrate, because I'm pregnant. I can't drink or anything, so...

ANDY PARK: We've got a pregnant Queen?

RHIANA MASON: Yes, yes.

ANDY PARK: Feral pig hunting is a way of life here that's often misunderstood in the city but some caution today's celebrations hide very real dangers.

ALISON LYNCH: You don't want to be taking these diseases back home to your loved ones.

(Last shot of bloody, dusty dead pig being dragged by its back feet)