Neurotoxic spiders

 

Black button spider complex

The black button spider complex contains the most venomous species: Latrodectus indistinctus, L. renivulvatus, L. cinctus and L. karooensis .

They are dark brown to pitch-black spiders with no ventral markings on the abdomen and with dorsal markings varying from red stripes to red spots. The egg cocoons are usually round and with a smooth appearance.

Black button spider, red pattern varies between species and female with eggs

Brown button spider complex

The brown button complex contains two less venomous species: L. geometricus and L. rhodesiensis. Their colour varies from cream, grey, and brown to pitch black. The ventral surface of the abdomen in both species has a prominent red to orange hourglass marking, while the dorsal surface is covered with an intricate geometrical pattern. A potential source of confusion in respect of the identification of these two species is that the most venomous species in Europe and America have the same red hourglass pattern as the two less venomous species found here. In general L. geometricus, the less venomous button or house button spider is an introduced species and the one more often found in built-up areas, especially in outbuildings and under windowsills. The other button spiders are more often found in natural habitats, usually outside built-up areas. The egg cocoons are characteristic in having a spiky appearance in L. geometricus and larger with a fluffy appearance in L. rhodesiensis.

Brown buttons vary in colour but all with glass pattern ventrally, red hour and egg sac

Signs and symptoms of Latrodectism

The term latrodectism is used to describe the symptoms and signs caused by envenomation of the button spiders. The black button complex causes a more severe form of envenomation than the brown button spiders. Only the female button spider is able to pierce the skin of man, and most cases the potential full dosage of venom is not administered.

• Black button spiders: a bite of a black button spider is usually very painful and causes generalised muscle pain and cramps, stiffness of the stomach muscles, limb pain especially legs, weakness in legs, profuse sweating, raised blood pressure and restlessness. Although no documented records exist of fatality due to button spider bites they have the potential to cause severe symptoms with small children and elderly people being at greatest risk.

• Brown button spiders: the symptoms occurring after a bite from one of the brown buttons are milder and tend to be restricted to the bite site, characterized by a local burning sensation which may spread to the surrounding tissue and lymph nodes. The bite site is more evident and often seen as a red macular spot or blanched area surrounded by a localised rash. The condition usually clears up within a day or two.

Treatment of button spider bites

In the case of black button envenomation the patient must be hospitalized and vital functions monitored for up to 24 hours. The administration of black button antivenom is the only effective treatment for severe latrodectism. Antivenom (10 ml) is administered intravenously. A follow up dose of 5 ml is occasionally necessary after 4-6 hours. Patients usually respond dramatically within 10-30 minutes. The patient should be kept under observation for at least 6-12 hours after treatment for any allergic reaction (not common) to the refined equine antivenom serum. The only effective agent for the relief of muscular pain and cramps is intravenous calcium gluconate (effect last only 20-30 minutes). Spider bites may easily become infected and care must be taken. The antivenom is produced by the South African Vaccine Producers Institute in Edenvale or can also be obtained from the South African Institute for Medical Research in Johannesburg.