Unraveling the host range of <i>Plasmodium huffi</i>: morphological, histopathological and molecular characterization in red-legged seriemas from Brazil

Avian <i>Plasmodium</i> parasites can be pathogenic to their vertebrate hosts. Although cases of anaemia are frequently reported in parasitized birds, the potential damage caused by the parasite during the exoerythrocytic reproduction phase remains poorly investigated. Here, we report 2 individuals of red-legged seriemas (<i>Cariama cristata</i>) infected with 2 different lineages of <i>Plasmodium huffi</i>, one of them exhibiting potential malarial-compatible tissue lesions in the spleen, liver, brain and lungs, alongside molecular confirmation of parasite presence in the spleen. Previously classified as specific to birds from the order Piciformes, this parasite has shown different associated lineages amplified across diverse host orders in South America (Anseriformes, Charadriiformes, Columbiformes, Galliformes, Pelecaniformes and Passeriformes). Those infections, however, were defined as abortive due to the absence of gametocytes visualized in blood smear slides. Herein, we confirm <i>P. huffi</i> as a generalist parasite based on the first morphological characterization in the peripheral blood of a bird outside the Piciformes order. This is also the first morphological and molecular description of a <i>Plasmodium</i> species in Cariamiformes. In addition to the morphological analyses, we have also proposed a novel phylogenetic hypothesis based on the partial <i>cytb</i> gene and the near-complete mitochondrial genome of this parasite. Our findings support that the division of the genus <i>Plasmodium</i> into subgenera is not monophyletic, as <i>P.</i> (<i>Huffia) huffi</i> and its associated lineages cluster more closely with <i>Plasmodium</i> (<i>Haemamoeba) gallinaceum</i> than with <i>Plasmodium</i> (<i>Huffia) elongatum</i>.