Parasites, suckers, intestinal visitors: Mike Leahy's 10 terrifying creatures for travelers

Parasites, suckers, intestinal visitors: Mike Leahy's 10 terrifying creatures for travelers

Spiders that cause priapism, eyeball-loving worms ... Dr. Mike Leahy, star of National Geographic's "Bite Me," explains some of the world's treacherous creepy-crawlies
On National Geographic's TV series "Bite Me," virologist Dr. Mike Leahy goes looking for the creatures most of us would prefer didn't exist.

When traveling overseas most of us would get the relevant vaccinations, maybe take anti-malarial medication, and assume that we are safe.

This is potentially a very dangerous and painful assumption to make, because there are plenty of unexpected threats out there that could turn your vacation into a nightmare –- and possibly kill you.

Here are 10 you may never even have heard of. Not for the squeamish.

10. Loa loa

This disease is spread by the bite of the innocuous mango fly, but can leave you with worms crawling out of your eyeballs. (Google "Loa loa" at risk, the images are rather graphic.) 

It’s only number 10 on my list because it won’t kill you, and may not even blind you, but it is pretty freaky. 

If you plan to travel in sub-Saharan Africa the best way to protect yourself (and this is a common theme) is to cover up with long sleeved clothing and consider using insect repellent.

9. Assassin Bug and Chagas Disease

Dr. Mike lets the dreaded "Assassin Bug" roam free on his face. The Assassin Bug can find you at night while you sleep, firstly using its natural thermal-imaging camera, then a chemo-sensor that can detect carbon dioxide given off as you breathe.

Once on your face the bug feeds on blood from your lips or your eyelids -- without you even knowing that it's there. As the insect feeds it also defecates, and that’s how a tiny single celled parasite can leave the assassin bug and enter your bloodstream, leading to Chagas Disease.

Over the years Chagas Disease might kill you by stopping the muscular contractions of the guts, meaning you will fill up with your own waste products, or it may simply cause heart failure. The bite of an infected Assassin Bug supposedly killed Charles Darwin, but it took decades of suffering to do so. 

Although present in the United States, this bug, and the disease it carries, is normally only a problem in Central and South America. Sleep in a romantic thatched beach hut at your peril, because assassin bugs love making their homes in such places.

8. Botflies

If you knew that there was a large, slow-moving fly at large in South America, and that if it landed on you it was likely to lay eggs onto your skin, which would hatch immediately and release larvae that would burrow into your flesh and eat you alive, then you would probably squash it.

But the botfly has evolved to avoid this response by "kidnapping" other innocuous flies or mosquitoes and laying eggs on them instead of you, its intended host.

When the "kidnapped" fly lands on you the eggs drop off, larvae burrow into your skin and make you into their living dinner -- without the parent fly ever being at risk.

A botfly infestation might not kill you, but is messy, and it hurts. Doctors will usually cut out the larvae pustule and prescribe antibiotics to clear it out of your system.  

Again, the best protection is to cover up.

7. Intestinal worms, roundworms, hookworms and tapeworms

These creatures rarely kill you, but they will cause discomfort and embarrassment. In more severe cases, they can grow in your brain causing fits and seizures.

Tapeworms are usually contracted when eating under-cooked meat, whereas the larvae of hookworms and roundworms don’t even need to be eaten. They can access your body by burrowing through your skin without you ever noticing.

Once in your body, roundworms simply share your food (although they can also block your intestines). The hookworm, however, feasts on your blood.

Don’t eat under-cooked meat and never walk barefoot in developing or tropical countries because the roundworm ascaris lumbricoides is said to infect 75 percent of the world’s population.

6. Irukandji

The Irukandji jellyfish, considered by researchers to be one of the world's most poisonous creatures, is only the size of a thimble. A tiny jellyfish that is almost invisible, the Irukandji has a painless sting, but can cause massive pain and suffering shortly after you fall victim to its attentions.

You don’t even have to be swimming in the sea to suffer. It's been reported that a 45-year-old Filipino was stung by an Irukandji while fishing from a bulk carrier.

The man, who was airlifted to hospital, was 25 meters above sea level when stung. It is assumed that the creature was blown up with sea spray. Jellyfish nets won’t protect you either because this tiny animal can slip through.

You could wear a "stinger suit" if swimming in Queensland or the surrounding region during Irukandji season when advised, and never swim on beaches without lifeguards with reliable local knowledge.

This little beast is most problematic around the east coast of Australia, which is a shame, because the warm sea and sandy beaches look so inviting there.

5. Wandering spiders 

One of the most venomous and dangerous spiders in the world is the Brazilian "wandering spider," or "banana spider," although its bites are also famous for another nasty side effect.

The venom can cause an involuntary and long-lasting priapism for men.

Chances are you won’t even be able to put it to good use before you die from the other components of this potent toxin.

4. Bloodworms

The very name "bloodworm" sounds macabre. But the damage they can do to the human body, and the sheer scale of the problems caused by these tiny parasites, is far scarier.

The larvae (cercaria) of these little animals live in freshwater snails, usually in relatively clear water. But when they sense a warm-blooded host, such as a human being swimming past, they swim towards it, penetrate the skin, move around the body, and finally make their home in the intestines, or the bladder, where they can live and reproduce for up to 12 years gradually destroying the organ that they made into their home.

It sounds like something out of a sci-fi film, but it is definitely not rare. Up to 200 million people suffer from schistosomiasis (bilharzia) worldwide and a large proportion of these will die prematurely from the illness.

The solution -- don’t swim in slow moving fresh water anywhere in sub-Saharan Africa or South America. In other places check first. People have even contracted the disease in un-chlorinated swimming pools in Rio de Janeiro.

3. Sand flies, Leishmaniasis

On the west coast of New Zealand sand flies are a pain -- literally, but it’s only the intense itching that will bother you.

In South America a sand fly bite can lead to your eyes or nose being eaten away by bacteria, and in the Indian sub-continent the disease that they carry can (and often does) kill.

The tiny flies don’t make a buzzing noise, and can sneak through mosquito nets, so defending yourself can be very difficult.

Insect repellent, long-sleeved clothing and avoiding sand fly habitats are the best tactics, but surely you went on vacation purely to spend time on a sandy beach?

2. Day-biting mosquitoes -- dengue and elephantiasis

Researchers are working on a dengue fever vaccine. For now, the only way to protect yourself is to cover up and wear repellent. Most of us know that we should avoid going out at night without some form of protection against evening-biting mosquitoes, whether that is in the shape of long-sleeved clothes, insect repellent or simply staying inside.

However, day biting mosquitoes can spread a disease called dengue fever, otherwise known as "break-bone fever."

The first time you contract it you will probably survive. The second time it is possible that you will develop dengue hemorrhagic fever, in which case your organs can turn to mush, you may bleed from every orifice -- you stand a good chance of dying.

Dengue is widespread across most of the tropics, with cases often occurring among backpackers on idyllic Southeast Asian islands, but if that’s not bad enough daytime biting mosquitoes can also spread tiny worms that cause lymphatic filariasis.

Also known as "elephantiasis," the worms block the lymph nodes of the body’s drainage system" causing testicles to swell to the size of beach balls and legs to resemble tree trunks.

In areas of India up to one third of the population may be infected, and the disease is essentially incurable.

So, cover up in the day time as well as the evening, unless you know that it is safe to bare your flesh. 

1. Candiru fish

I would be lying if I said that candiru fish attacks were a regular occurrence, but the consequences are so dire that it definitely merits its place as the No. 1 weird and wonderful threat when traveling.

The way to avoid this blood-sucking fish’s unwanted attentions -- don’t pee in the Amazon.

Though there's much debate about this fish and alleged tales of its attraction to urine, no man wants one stuck in their urethra, as happened to at least one poor chap in recent years. 

Once inside, it will feed on your flesh before surgery is required to get it out. 

Tae kwon do black-belt and former motor vehicle mechanic Dr. Mike Leahy is currently traveling the world giving presentations to schools and other educational establishments about his research and adventures on TV. Check him out at or follow him on Twitter @OfficialDrMike