Fig. 1

The avian malaria life cycle starts when (a) a feeding mosquito infects an avian host with Plasmodium sporozoites; (b) sporozoites then develop into exo-erythrocytic meronts (i.e. cryptozoites) in reticuloendothelial cells (e.g. spleen, liver, bone) throughout the body (c) followed by the development of merozoites into the second pre-erythrocytic exo-erythrytic stage and producing metacryptozoites. d Following development into metacryptozoites, further generations of this stage can be formed from previous generations. e Alternatively, merozoites from metacrytpzoites can enter the bloodstream, infect erythrocytes and (f) become meronts to continue into the erythritic cycle. g Merozoites can also develop into the next exo-erythrocytic form, the post-erythritic phanerozoites, which can (h) also develop further generations of phanerozoites or (i) develop into merozoites. Merozoites can be formed from either phanerozoites or erythrocytic meronts. From (j) merozoites, the erythrocytic cycle continues with the development of (k) male and female micro/macrogametocytes. These gametocytes are then (l) capable of infecting another mosquito to begin the process of sporogony in this next host. Once inside the mosquito, the gametocytes develop into (m) gametes in the midgut. These gametes come together to form (n) a zygote, which then develops into ookinetes that travel from the midgut to the epithelium, (o) followed by development into oocysts. Within the oocysts, (p) infective haploid sporozoites form and burst through the oocyst wall once reaching maturity. These haploid sporozoites then invade mosquito salivary glands, where they can be transferred to another bird host when the mosquito feeds