Paederus dermatitisL24.8

In 1998, an unusual proliferation of the beetle Paederus sabaeus led to an epidemic of toxic contact dermatitis in sub-Saharan Africa. Cell toxins contained in the hemolymph, which get onto the skin when the beetle is accidentally crushed, cause blistering and necrosis of the skin. The dermatitis usually heals without complications in seven to ten days. More pronounced inflammatory symptoms, for example on the face ("Nairobi Eye") and secondary infections can occur. Treatment is symptomatic.

Toxic, frequent blistering dermatitis following skin contact with beetles of the genus Paederus from the short-winged beetle family, triggered by the toxin pederin found in female beetles.

Paederus is a slender beetle about 7 to 13 mm long that belongs to the Staphylinidae family (short-winged beetles) and is found worldwide. The orange-red and very dark green or blue metallic color of its body makes it easy to recognize. Beetles of the genus Paederus occur worldwide. Endemic outbreaks of toxic dermatitis caused by this beetle genus have been observed in the past in tropical countries (Kenya, Cameroon, Naminia, Congo, Sudan, Uganda), occasionally also in France, Turkey and Australia. (McCrae AW et al. 1975 ; Okiwelu SN et al. 1996; Penchenier L et al. 1994).

The genus Paederus comprises more than 500 species, of which about 30 are medically relevant. For example, Paederus sabaeus is found in West and Central Africa and P. eximius in East Africa.

Only fragmentary information exists on the ecology of the beetle. It lives as a hunter of smaller insects in humid environments under vegetation and along watercourses. This also explains its occurrence in tropical regions during the rainy season. Paederus is a nocturnal insect and is attracted by light, especially neon tubes. The beetles then crawl over the brightly lit skin or drop from the ceiling onto the victim. In 1998 there was an exceptionally intensive increase and spread of Paederus south of the Sahara compared to previous years.

The highly toxic alkaloids pederine and, to a lesser extent, pseudopederine, which are contained in the insect's hemolymph, have been identified as the cause of dermatitis. In cell cultures, concentrations of 1 to 1.5 ng/ml already cause an inhibition of cell growth. Histologically, the toxins lead to intra- and subepidermal blistering, epidermal necrosis and acantholysis (Borroni G et al. (1987).

Pederin only comes into contact with human skin when a beetle is vigorously brushed or crushed over the skin. Due to their common appearance or misunderstandings about their etiology, the resulting skin lesions have been termed dermatitis linearis, spider lick (India and Sri Lanka) and whip lash dermatitis.

The beetle is mainly nocturnal and is attracted by artificial light at night. When staying outside at night the beetles meet humans. They let themselves fall from walls or ceilings onto brightly lit skin areas. Only when the beetles are injured by stripping or crushing them, toxic dermatitis is caused by toxins (toxic alkaloids: pederin, pseudopederin) released by the female beetle. The form and type of dermatitis is determined by the mechanical act of "stripping" from the skin (streaking). Often linear blistering (Paederus sabeus also known as "blister beetle")

Female short-winged beetles of the genus Paederus harbor an endosymbiont very closely related to Pseudomonas aeruginosa, which is responsible for the synthesis of the cytotoxic toxin "pederin". The importance of this toxin for Paederus beetles apparently lies in its defense function against potential attackers. Due to its very high tumor-inhibiting and antiviral effectiveness, pederin is also of interest for medical research. The pederin-producing symbiotic bacteria can only be detected in the appendage glands of the female reproductive system and the excretory duct. Thus the dermatitis is only triggered by the female beetle.

Compare also Lytta vesicatoria dei"Spanish fly" which triggers the so-called " oil beetle dermatitis" by releasing cantharidin.

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