Mosquitoes, ticks, mites, flies, fleas, and lice are more than simply annoying. Their bite can pass on serious, sometimes fatal, infectious diseases.
Perhaps the best known is the mosquito-borne P. falciparum (or cerebral) strain of malaria, which kills an estimated 600,000 people each year.
Dengue and Chikungunya may not be as lethal as malaria, but they are now so widespread in tropical and sub-tropical regions that hundreds of thousands of people across the globe are infected each year after being bitten by an infected female Aedes egypti or Aedes albopictus mosquito.
More and more Australian travellers are experiencing these painful, debilitating, and sometimes long-term illnesses.
While we have effective malaria preventation medication, there is still no pill or vaccine against the dozens of other insect-borne diseases. (One exception is dengue fever. A vaccine is undergoing clinical trials and is expected to be available in 2015.)
The biting habits of insects differ widely, yet the same preventative measures are effective against almost all of them:
· Applying DEET-containing insect repellent to bare skin.
· Wearing long sleeves and pants (especially at high-risk times), and
· Sleeping in a screened room or under a bed net impregnated with permethrin.
DEET won’t protect against deadly hornets
But, not all of the dangerous insects bite their victims. Some, like Vespa mandarinia or the Asian Giant Hornet, sting them to death.
And, unfortunately for anyone who encounters them, no amount of DEET will keep them at bay if they feel sufficiently threatened to attack.
These giant hornets of East Asia are the world’s largest – as big as a man’s thumb – and can travel at 40kph. Gold and black in colour, they make their homes in tree stumps or underground, making their nests extremely difficult to detect.
The hornet’s sting is extremely painful and its potent venom contains 8 different chemicals, each with a specific purpose – ranging from causing tissue degeneration and breathing difficulties, to calling in other hornets to join in an attack.
Unlike other wasps and bees, its stinger is not barbed, enabling the fierce insect to repeatedly sting its victims.
Chinese province under siege
In north-west China's Shaanxi province these truly scary insects have killed 41 people and injured a further 1675 in the past 3 months compared with an average of 36 deaths a year.
However, local reports put the number of fatalities this year as high as a staggering 1400 people, according to the international disease monitoring and reporting network, ProMED. All of the Asian Giant Hornet’s victims have been local people.
Little wonder residents describe 2013 as the worst year ever for the hornets and say the situation is tantamount to an epidemic.
Ankang, a municipality in the south of the province, has been at the centre of the attacks.
Local officials have removed 710 hives but have been overwhelmed by the task, especially as they are also battling to control a smaller species, the Asian hornet (Vespa velutina), which can be equally dangerous. Hundreds, even thousands, inhabit each nest, which typically hangs from high in trees and other lofty places.
Two other cities in Shaanxi - Hanzhong and Shangluo - have also been besieged by the two species, though the death tolls have been much lower.
Students, teacher attacked by swarm
In southern China's Guangxi Zhuang autonomous region, angry hornets attacked a primary school last month, injuring 23 children and 7 adults. The teacher, Li Zhiqiang, told pupils to hide under their desks and tried to fight the creatures off until he lost consciousness, state media reported.
The Asian Giant Hornet is a relentless hunter. It preys on other large insects and can quickly wipe out a colony of bees. Once a hive is emptied, the hornets feed on the honey and carry the larvae back to feed to their own larvae.
Adult Asian Giant Hornets cannot digest solid protein. Instead they chew it into a paste and feed their young. Adults consume Vespa amino acid, a clear liquid which is produced by their larvae.
Humans pose the biggest threat to the giant hornets. In the mountains of Japan, where the Asian Giant Hornet populations are most abundant, local people have found a way to catch and eat them fried or raw (the venom is not deadly when the hornet is eaten raw).
If you haven’t heard of these fearsome insects before, that is likely to change in the future.
Companies in Asia and Europe have begun to manufacture dietary supplements and energy drinks which contain synthetic versions of Vespa mandarinia larval amino acid secretion.
‘Hornet juice’ – the breakfast of champions?
A compound derived from Vespa mandarinia larval saliva (called Vespa Amino Acid Mixture or VAAM) is sold as a nutritional supplement. The makers claim that consuming the larval hornet secretions (marketed as ‘hornet juice’) will enhance human endurance, according to the ProMED report.
Mice that were administered VAAM have demonstrated enhanced swimming endurance, along with decreased lactate and increased glucose concentrations in their blood after exercise. The results suggest that VAAM inhibits muscle catabolism (the metabolic breakdown of complex molecules into simpler ones, often resulting in a release of energy) during endurance exercise.
As yet there’s no scientific evidence to suggest that VAAM can improve performance in human athletes.
However, if and when it can be shown to shave medal-winning milliseconds off an athlete’s personal best time, the sting could well be in the price it commands.