Invasion of the brown widows
The venomous brown widow spider arrives in Malaysia.
A POISONOUS spider, once confined to Africa, is slowly spreading around the globe. And it has found its way to Malaysian shores.
The brown widow spider ( Latrodectus geometricus) is now confirmed to exist in Penang, Selangor and Johor, after Universiti Malaya ( UM) scientists studied the physical features and DNA bar- coding of samples.
In Penang, the 1cm- long spiders had infested homes in a newly completed housing estate in Bukit Mertajam. The developer was advised to fumigate the area. In Selangor, the spiders found a home on a student’s bicycle in Serdang and on furniture in a mamak stall in Bandar Sunway. In Johor, they were found in the hinges of a car door. These sightings were made in 2011 and 2012, and the results were recently published in the Journal Of Venomous Animals And Toxins Including Tropical Diseases.
The latest reported sighting was four months ago, when the UM scientists received a spider sample collected from Sungai Buloh from the Selangor Health Department for identification as it was unusual- looking, and it turned out to be the brown widow.
The brown widow spider is among the 30 species of the genus Latrodectus. They earned the name “widow” because the female supposedly eats the male after mating. However, this behaviour has been only conclusively documented for one species, the red- backed spider ( Latrodectus hasselti) that is found in Australia, New Zealand and Japan.
The name widow spider instantly strikes fear as their venom has gained them notoriety. But while bites from the black widow ( Latrodectus mactans, found in North h America) can be fatal, they have led to deaths in less than 1% of cases. Deaths from injection of venom ( envenomation) from the brown spider is less- known. A case was as reported in Madagascar in 1991 but it remains in question.
Mustakiza Muslimin, lead author of the paper, says save for two species, all spiders are venomous but not all of these cause harm to humans. The brown widow is known to be non- aggressive and only bites when threatened. Like most widow spiders, it avoids people and if disturbed, retracts its legs and play dead.
Co- author Dr Noraishah Mydin Abdul Aziz says the venom of the brown widow is actually more potent than the black widow’s but because it is less able to bite through the skin, this bring cases of injection of venom to almost nil. “The worrying thing is if someone develops an allergic reaction from the bite,” says the senior lecturer in the department of parasitology, UM faculty of medicine.
Nevertheless, she adds that the presence of the brown widow here is a concern and should be monitored. “People should be aware that they’re found here and know what they look like. But there has been no reports of people suffering severe pain from a spider bite.”
The brown widow spider is highly adaptable and has found niches in 58 countries. They very likely “hitchhiked” in shipping containers into south and north America, the Middle East, Central Asia, Indonesia, the Philippines, Singapore, Malaysia, Japan and Australia. They have yet to be reported in Europe, with the exception of Turkey.
The ones seen here are similar to those from port cities in Japan, so they probably originated from there. Selangor also has one form with a spherical abdomen that is similar to those seen in India and Brazil.
Dr John- James Wilson who identified the species using DNA bar- coding, believes the brown widows are likely to have spread beyond the three states but this goes unreported because people do not recognise them.
“We want the general public to be aware of it. If someone is bitten, it’s possible that it might be the brown widow since it’s found here now. Doctors can give the right treatment if we know what spider it is.” He adds that there should be websites to help the public identify harmful spiders, such as seen in the United States.
Spiders have generally been poorly studied, but the UM team is changing that. The scientists have been studying all kinds of spiders to document their diversity and to see how they can be of help to us. Noraishah says as spiders feed on mosquitoes, there is a lower incidence of mosquito- borne diseases in places with big spider populations. There is also research that shows the potential of spider venom in treating heart diseases.
The brown widow spider has a distinctive hourglass- shaped mark on its belly that is tan or orange in colour. — TnS
STAr2, Monday 13 July 2015
“There are many ways in which they affect our daily lives, and it could be important, for example, in controlling mosquito populations. We don’t know until we study them,” says Wilson.
The scientists have observed jumping spiders feeding on the brown widow, so there is a possibility of some sort of bio- control. This will be the subject of future research. So how can people protect themselves from this spider? The scientists say the simplest way is to keep your home clean and free of cobwebs. Insect repellent also works. Kill the spiders and destroy their egg sacs if found inside the home or garden. And learn to identify the species, which has distinctive features:
> Dome- or round- shaped abdomen which is much larger than the head;
> Thick dark bands on the leg joints;
> Hourglass- shaped marking on the belly, seen in all widow spiders;
> Spiky egg sacs.