Deadly spiders in Europe: should we be worried?

Perhaps Australia, with its famous snakes like the taipan (Oxyuranus microlepidotus), or Brazil, home to formidable creatures like the yellow scorpion (Tityus serrulatus). Europe, however, is unlikely to be first on the list, as the continent is not known for threatening fauna, according to the phys.org article.

But in recent years, fear of one small, eight-legged creature has grown in southern Europe, with deaths attributed to a particular species of spider gaining publicity. The latest high-profile incident occurred this summer in the Italian city of Bari, where a 23-year-old man died after a suspected bite from a Mediterranean hermit spider, also known as a brown recluse. A month earlier, a 52-year-old policeman in Palermo died of the same cause.

Europe's two most dangerous spiders

If you like to explore every nook and cranny and you're unlucky, a walk in the Spanish countryside could result in a painful bite from one of the larger spiders, such as the kingworm spider (Macrothele calpeiana) or the tarantula (Lycosa tarantula). However, there are only two species of spiders in the Mediterranean whose bites are considered medically significant: the European black widow (Latrodectus tredecimguttatus) and the Mediterranean recluse spider (Loxosceles rufescens).

The black widow has always had a bad reputation, but there are no documented cases of death from the bite of its European variant. In addition, encounters with this spider are rare, as it lives in rural areas and weaves nets under tree bark or rocks. Its neurotoxic venom, known as latrotoxins, affects the nervous system, heart and smooth muscles, causing latrodectism syndrome.

The recluse spider, which usually has a dark violin-shaped spot on its back, poses another danger. Although it is found in the wild, it can be considered a synanthropic species - it prefers to live near humans, especially in homes, garages or workplaces. It often hides in dark, dusty places, such as behind or under furniture, and can go undetected for long periods of time.

Necrotic poison and its effects

Unlike the neurotoxic venom of the black widow, the venom of spiders in the family Sicariidae, which includes the Mediterranean recluse, causes tissue necrosis. Their venom contains phospholipase enzymes that destroy cell membranes and blood vessels. As a result, a localised reaction occurs at the bite site: swelling, redness and itching that can last for several weeks.

In rare cases, a necrotic ulcer may develop where the tissue dies off and eventually heals. This syndrome, known as cutaneous loxoscelism, is usually not serious unless the bite is on the face or other sensitive areas. Necrosis is less common in the European hermit than in its Latin American relatives (L. reclusa and L. laeta), which are a serious problem in countries such as Chile and Argentina.

In very rare cases, necrosis can reach the muscles and cause toxic shock syndrome with symptoms such as fever and muscle pain. This condition, known as cutaneous visceral loxoscelism, can lead to acute haemolysis, kidney failure and even death.

Should we be wary of recluse spiders?

In Spain, L. rufescens has lived near humans for thousands of years, but bites are extremely rare and reliable data are scarce. Even in serious reactions, the patient rarely sees the spider, so diagnoses are often not confirmed.

An interdisciplinary team of researchers from the University of the Balearic Islands this year analysed several cases of suspected recluse spider bites in Spain. So far, no deaths from its bites have been reported in the country. The recent deaths in Italy remain a mystery: perhaps a statistical anomaly or errors in diagnoses.

There is also the possibility that American species of Loxosceles, more dangerous to humans, have been accidentally introduced to Europe due to globalisation. However, there are no official records of such populations in Europe.

Arachnophobia fuelled by horror films and sensational articles does not reflect the real threat. In Europe, the risk of suffering a spider bite is minimal. There have been 1,691 deaths from wasp and bee stings in 23 years, but we don't panic at the sight of a bee on our sandwich.

Mediterranean recluse spiders are not aggressive and only bite when directly disturbed. Regular cleaning and caution when moving furniture will minimise the risk of a bite. The likelihood of being hospitalised due to a Loxosceles bite is no greater than being struck by lightning.