Omnipresent blue micro-organism native to BDA Tr#ska.
T. caruleus is blue because of complex cobalt ferrocyanides in its makeup. It is parasitic and pervasive, existing within any number of animal hosts and consequently tinting their skins blue. The presence of T. caruleus in the body creates a physiological dependence on traces of cobalt in the soil.
T. caruleus is highly infectious, but does not live long outside the body. Due to a high mutation rate, a specific population usually accustoms itself to a particular host's unique biochemistry within a Terran year or so. After this acclimatization period, the microbe is infectious only through transfusion and by placental crossover during pregnancy.
Only on BDA Tr#ska itself, where every living creature plays host to T. caruleus, is it one hundred percent certain that a Human will become infected.