Like all Plasmodium species P. circumflexum has both vertebrate and insect hosts.

Schizonts: these are large and when mature may entirely encircle the erythrocyte nucleus.

Gametocytes: these are large and when mature may entirely encircle the erythrocyte nucleus.

This parasite is found in Argentina, Brazil, Canada, Germany, Italy, Malaysia, Morocco, South Africa, Sri Lanka and the United States.

Culiseta morsitans Mansonia crassipes Theobaldia annulata Sporogeny but not transmission has been recorded in Mansonia perturbans.