Australia’s Most Venomous Species

    

The red back is one of the most venomous spiders in the worldAustralia has its fair share of venomous species – 20 of the world’s 25 most venomous snakes are Australian and two of the world’s most venomous spiders are native. But before you are gripped with panic, only three species have bites which alone are capable of causing death – the funnel-web spider (and related atrax species), the red back spider and the paralysis tick.  Every year there are hundreds of bites reported but fewer than 30 percent of them require the anti-venom treatment. The pain from a spider bite can be excruciating but should serve no lasting damage.

The Brazilian wandering spider is world’s most venomous spider and is native to Brazil. Unfortunately the spider, which is fond of living in banana plantations, can be boxed up with its fruity cargo and wander into Australia, and other parts of the globe as was reported by a shopper at a British supermarket last week who discovered a spider as big as his hand hanging from a bunch of bananas.

Most venomous species are brightly coloured to warn predators away. The distinct red splash of colour displayed by the red back or the yellow and black stripes of a wasp are nature’s way of signalling danger. And just to confuse you, other insects such as the hover fly mimic these patterns but are completely harmless. Here’s some more information about Australia’s three most venomous pests:

Red Back Spider

The red back spider is a close relative of the black widow spider in America and the false black widow which can be found in certain parts of the UK and Europe. All three species deliver a nasty bite but it is normally only the female who delivers a potentially harmful bite – the males are normally too small.

Red Back Spiders are around the size of a 20 cent coin and can be found in every area of Australia, including populated areas. They are not aggressive and  will happily live alongside humans as long as they have access to food and shelter.

The venom of the red-back spider is much slower acting than the funnel web spider and since the introduction of anti-venom in 1956 there have not been any deaths from the spider bite.  According to Australian Museum the average seems to be around 250 anti-venom treatments being administered every year in Australia. The majority of victims of red-back spider bites suffer from a immediately painful bite which may spread to the whole limb. The inflicted may sweat and suffer from headache, nausea, vomiting, abdominal pain, fever, hypertension and in severe cases, paralysis. Untreated, the symptoms worsen over a 24 hour period and may take weeks or months to resolve.

 

Funnel web spiderSydney Funnel web spider

This spider is a sizeable beast mostly found near Sydney (Newastle to Nowra and as far west as Lithgow but sightings have been reported as far north as Brisbane. Related species are found along the eastern coast of New South Wales).

Funnel-webs burrow in sheltered sites under logs and rocks where they can find a cool and humid climate. For this reason is is advisable to avoid storing wood next to your house. Funnel-webs eat beetles, cockroaches, small lizards or snails. They catch their prey when their victims trigger a silken trip-lines placed around the outside of its burrow. They rush out of their burrow to catch their dinner then return to their burrow to eat their meal.

Funnel-webs burrow in sheltered sites under logs and rocks where they can find a cool and humid climate. Funnel-webs rush out of their burrow when potential prey, such as beetles, cockroaches, small lizards or snails, walk across silken trip-lines that the spider has placed around the outside of its burrow. They then return to their burrow to eat their meal.

The venom of the slightly smaller male spider is five times as toxic as the female as male funnel webs tend to roam about looking for a mate. After periods of heavy rain in summer they may wander into homes and other premises to seek shelter. Sometimes they may fall into a pool and can survive for many hours. Interestingly humans are particularly sensitive to their venom, whereas potential predators such as toads, cats and rabbits are largely unaffected.

The bite is usually immediately very painful and symptoms commence usually within a few minutes. They include, progressively, sweating, muscle twitching, salivation, secretion of tears, excessive heart beat and severe hypertension, vomiting, airway obstruction, muscle spasms, writhing and grimacing, unconsciousness, raised intracranial pressure, widely dilated pupils (often fixed), and death unless artificial ventilation is provided.

After about two hours the muscle fasiculations and most symptoms start to subside, and are replaced with insidious but profound hypotension, primarily due to severe cardiac failure.

 

Australian paralysis tick

Macro photography of a tick Also known as the seed or grass tick, the Australian paralysis tick is widely distributed in south eastern coastal temperate regions. Ticks are prevalent in wooded and deep grassy areas and dogs can be easily pick them up. Adults ticks can be difficult to spot and are about the size of a sesame seed. They can cause itchy bites and sometimes hundreds of small ticks can attach to a persons legs, causing significant swelling and profound itching. Ticks need a blood meal to survive and can carry and pass on disease including Lyme disease.

The Australian paralysis tick secretes a neurotoxin in its saliva that causes a progressive, and occasionally fatal, paralysis. Sometimes a severe hypersensitivity reaction or localised paralysis of facial muscles occur, but more commonly there is progressive ascending flaccid paralysis affecting the lower limbs first.

Incorrectly removing a tick may result in a greater number of poison released into your bloodstream. Touching the tick with a lighted match or spraying with insecticide or oil can induce spasm in the tick and may cause it to inject more venom. The Centre for Disease, Control and Prevention advises that the best means of removal is to grip the tick as near to the head as possible with a very pointy pair of tweezers. To reduce infection, ensure that all parts of the tick have been removed. Avoid gripping the end part of the body as it almost always breaks off and fails to remove the head and legs.

If you know you are going into tick areas, wear long sleeves and light-coloured trousers and tuck them inside tight socks and boots. Check regularly for ticks and brush them away before they get a chance to crawl inside.  If you have a tick removal trick please share it with us.

 

Sources: http://www.anaesthesia.med.usyd.edu.au/resources/venom/spiders.html

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