Nairobi fly (Paederus beetle) Symptoms and Prevention

Nairobi fly (Paederus beetle) Symptoms and Prevention


  • Nairobi fly, Paederus beetle
  • Scientific classification
  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Coleptera
  • Family: Staphylinidae
  • Tribe: Paerini
  •  Genus: Paederus

Nairobi fly, Kenya fly or Paederus beetle is commonly found in humid areas and is attracted to fluorescent light. They are called as a fly but they actually are beetles. They belong to the genus Paederus which contains about 600 described species and is part of the beetle family Staphylinidae, commonly known as rove beetles. They are well known and feared for the burns, or dermatitis- that they cause on human skin.

A Paederus beetle can induce Paederus dermatitis, a unique and irritating contact dermatitis. Instead of biting or stinging, this insect exudes a fluid that contains paederin, a strong blistering agent. The chemical causes linear dermatitis, which includes blisters and red, irritated skin if it is not removed right once.

Note that Paederus beetles are not “blister beetles,” which belong to the Meloidae family. When threatened, blister beetles, which are similarly extensively spread, do emit a defense substance. Cantharidin, a bicyclic terpenoid, differs significantly from paederin, an amide, in the chemical that is released.

Dermatitis linearis, what is it?

Dermatitis linearis is the name for an acute skin disorder brought on by exposure to the lethal toxin pederin, which is present in a few species of the Paederina subfamily of Staphylinidae beetles. Paederus, the largest genus in this subfamily, with more than 600 species. Paederus beetles are relatively slender and can be uniquely identified by their size (∼1.5 mm wide and 7–10 mm in length) and coloring (black head with red, russet or orange thorax). The typical red or orange coloring is aposematic, warning predators that the beetle is toxic. Humans are exposed to pederin when the beetle is crushed and smeared across the skin, resulting in a characteristically linear lesion. If someone touches the periocular area or genitals after crushing the beetles, the toxin might be conveyed there. Local names for Paederus beetles that cause dermatitis linearis include whiplash rove beetle in Australia and Nairobi fly (or eye) and Econda in Africa, “tomcat” in Southeast Asia, and “tomcat” in the United States.

YOU MAY ALSO LIKE TO READ ABOUT Antimicrobial Resistance and how its affecting our everyday lives


Swelling and burning sensation on the affected body part

  • Presence of neck lesions with a whiplash appearance and linear reddish lesions
  • Kissing lesions on the elbow and surrounding thigh surfaces as a result of contact between healthy and diseased areas.
  • Allergies to the eyes, nose, or skin might occur occasionally.
  • Although dermatitis itself cannot be spread, pederin on hands, clothing, and bedding can be transferred and result in lesions in other locations.
  • The lesions may develop black or infect within 24-48 hours.

Treatment /Prevention

  1. Treatment initially involves removal of the irritant by washing the area with soap and water.
  2. Cool, moist soaks should be used to the blister site before applying a potent topical steroid. In a study that involved 36 patients and was done in Sierra Leone, in addition to the topical steroid, oral ciprofloxacin was administered to half of the patients. The fact that these individuals recovered more quickly suggests a concomitant bacterial infection, most likely caused by the Pseudomonas the Paederus beetle contains.
  3. For preventing, avoid contact between beetle and human.
  4. Learning to recognize Paederus beetles and avoiding handling or crushing these insects will help decrease these eruptions.
  5. If a beetle lands on the skin, it should be blown off or encouraged to walk onto a piece of paper and then removed. The area in contact should be immediately washed with soap and water, and any clothes in contact with the beetle should be washed as well.
  6. Doors should be kept closed and window screening should be kept in good repair to help reduce the entry of these insects into buildings. Since beetles are attracted to light, these should be switched off near areas where people sleep.
  7. As these insects are attracted to light, turn off fluorescent lights or tie a net cloth under the light to avoid the dropping of these insects on the bed or human body
  8. Try to sleep under a bed net to avoid their contact with the body at night in situations where a large population of these insects is present.
  9. Remove excessive vegetation from and around the home.