What insect is this? (Central Africa)
It is a Rove beetle of the Genus Paederus.   

Why Paederus sp.?


They are brightly colored  rove beetles, Coleopterans with short elytra.
Have metallic blue or green-coloured elytra. 
Have bright orange or red on the pronotum and basal segments of the abdomen.


There are widely spread on the planet and I found two species of Paederus sp. that are found in East of Africa, together they are called Nairobi flies. 




The medical condition it causes is called Paederus dermatitis.


  According to Medical and Veterinary Entomology (2009) "At least 20 of the more than 600 species of Paederus beetles have been associated with Paederus dermatitis", even though Paederus beetles do not bite or sting. 
  
  This skin irritation results from contact with pederin, a vesicant toxin in the hemolymph of many but not all females in the genus Paederus. 
  
  The toxin is manufactured, not by the beetles themselves, but by endosymbiont bacteria, probably some species of Pseudomonas.
  
  Three different genera of rove beetles, all members of the same subtribe Paederina, can cause paederus dermatitis: Paederus, Paederidus, and Megalopaederus.


Pederin


  Pederin blocks mitosis at levels as low as 1 ng/ml, by inhibiting protein and DNA synthesis without affecting RNA synthesis, prevents cell division...


This makes it also a potent antitumour agent.


  The manufacture of pederin is largely confined to adult female beetles—larvae and males only store pederin acquired maternally (i.e., through eggs) or by ingestion.
  
  It is a contender of the title of most powerful animal toxin.
  
  It is among the most potent animal products known, more so than Latrodectus venom, which is 15 times more potent than cobra venom.
  
  Ingestion can cause severe internal damage and intravenous injection causes death ...


Further Reading:

1. Dermatitis Paederus: About 06 cases occurred in Bun
ia, 
Democratic Republic of Congo 

2. STUDIES ON THE MECHANISM OF ACTION OF PEDERINE, 1968

References:


 1. Paederus

2. Pederin

3. Paederus dermatitis

4. Encyclopedia of Entomology

5. The Role of Natural Products in Drug Discovery

6. ChEBI



Note: I found the picture in your question is the same as that of Wikipedia's picture of Paederus.