Antigenic escape

How do these trypanosomes manage to survive extracellularly in human blood and tissue fluids for months or years without being destroyed by the host's immune system?

Well, yes, trypanosomes are absolute masters of immune evasion.

The entire parasite surface is covered by a dense glycoprotein coat composed of what we call variant surface glycoproteins, abbreviated as VSG.

The trypanosome genome contains nearly 2,000 different VSG genes.