Mystery about the cause

Lower Austria: Bite causes foot to swell – suspected spider!

The symptoms of a bite from the nurse thorn finger are similar to those of a wasp sting.

(Bild: Krone KREATIV, Michael Titz, zVg.)

Pictures and descriptions of a young man from Lower Austria make us feel uneasy. He was apparently bitten by a spider at the end of March - his entire leg swelled up and hurt. The doctor's diagnosis: the bite of a spider was to blame for his misery. But how dangerous are spider bites really?

The reassuring thing first: spiders that are dangerous to humans are rare in Austria. They are also shy animals. "They usually only bite when they feel threatened," says Christoph Hörweg, curator of the Arachnoidea collection at the Natural History Museum Vienna.

Spider bites are often confused
However, it is unclear how often spider bites actually occur. "Many people believe they have been bitten by a spider. But from a purely scientific point of view, it would only be a spider bite if the spider was observed or even caught so that an expert can confirm that it really was a spider." There are many factors that make documentation difficult. For example, you also need to know when which spider is in season. Stings or bites from other insects are often mistaken for a spider bite.

Whether the young man in Lower Austria was actually bitten by a spider cannot therefore be clearly verified.  

Is the bite of a spiny-fingered spider to blame? The swollen foot on the left, the normal side on the right.

(Bild: zVg)

Nevertheless, most of the rare spider bites recorded in Austria can be attributed to the house or nurse spider. These are one of the few native spiders that can penetrate human skin with their jaw claws and that we can actually encounter. "Theoretically, a water spider could also bite, but you hardly ever come into contact with this species," says Hörweg. 

There are ten different species of thorn finger in Austria, which in turn have different habitats. The nurse thorn finger is often only found in late summer in so-called "Gstettn", while the house thorn finger can already be found from May and also in houses. According to Hörweg, the green thorn finger is first found as early as March, for example in semi-arid grasslands.

A male nurse thorn finger with wide open chelicerae

(Bild: Michael Titz)

Symptoms are similar to a wasp sting
The symptoms of a bite from the nurse thorn finger are similar to those of a wasp sting. Initially severe pain that can last for several hours. Redness, itching, swelling and, very rarely, nausea may develop as the sting progresses. "After 24 hours, you shouldn't really feel anything and the bite is not that extreme in the case of the house thorn finger," says Hörweg, "secondary bacterial infections often play a greater role."

Poisonous banana spider in local supermarkets?
People are right to fear the Brazilian wandering spider, which, as the name suggests, is only (or mainly) found in Brazil. In Lower Austria, a supermarket was closed after an alleged sighting of the so-called banana spider. However, Hörweg sees little cause for concern here: "The majority of bananas that come from the EU do not come from Brazil, but from Costa Rica or Ecuador. There are some related species there, but they are not as dangerous for humans."