Diversity, distribution, and methodological considerations of haemosporidian infections among Galliformes in Alaska

Insights into the Biology of Leucocytozoon Species (Haemosporida, Leucocytozoidae): Why Is There Slow Research Progress on Agents of Leucocytozoonosis?

“…In other words, some solely PCR-based reports of Leucocytozoon infections and co-infections might be due to the amplification of DNA from persistent sporozoites, including those injected by vectors, that are unable to initiate development if they appear in the wrong (resistant or partly resistant) avian host. It is still unclear if many reported co-infections of Leucocytozoon lineages in naturally infected birds [ 7 , 51 , 118 , 119 ] represent competent or incompetent (abortive) infections at the sporozoite and/or exo-erythrocytic meront stage. It is worth mentioning that some abortive haemosporidian infections at the megalomeront stage might be virulent and even lethal when they appear in non-adapted avian hosts [ 4 , 94 , 120 , 121 ].…”

“…However, it remains unclear how often such co-infections occur in wildlife. The application of the commonly used general primers for the detection of partial sequences of the cyt b gene that are important for barcoding might not distinguish some co-infections [ 9 , 93 , 118 ]. This might lead to the incorrect conclusion that a single species can produce gametocytes both in roundish and fusiform host cells [ 9 , 153 ].…”

“…Targeted molecular testing of such cases is needed for final taxonomic conclusions, but such studies remain rare [ 9 ]. This is a particularly important issue for understanding the pathology of Leucocytozoon species if co-infections are present [ 95 , 118 , 119 , 234 ].…”

“…The application of CISH tools using parasite-specific probes opens new opportunities to link tissue stages found in wild birds with certain haemosporidian parasites [ 93 , 94 , 95 , 234 , 250 , 251 , 252 ]. This was difficult or impossible to do before the molecular era because co-infections of Apicomplexan parasites are common and even predominating in many avian hosts worldwide [ 4 , 7 , 9 , 10 , 23 , 38 , 40 , 42 , 58 , 105 , 110 , 118 , 253 , 254 , 255 , 256 , 257 , 258 , 259 , 260 , 261 , 262 , 263 , 264 , 265 , 266 , 267 , 268 , 269 , 270 , 271 , 272 , 273 , 274 ]. Recent molecular and microscopic studies show that the morphological diversity of haemosporidian exo-erythrocytic stages is unexpectedly diverse, particularly in Haemoproteus and Leucocytozoon parasites, which have historically been difficult or impossible to link to certain parasite species or lineages, even on genera levels, due to common co-infections […”

“…Second, the molecular characterization of Leucocytozoon species is often confused because of common co-infections of parasites belonging to the same genus [ 7 , 10 , 38 , 40 , 42 , 105 , 118 , 119 , 254 , 256 , 257 , 259 , 260 , 261 , 262 , 263 , 268 , 270 , 272 , 273 , 274 ]. Microscopic examination of blood films from many naturally infected birds shows that infection with a single species of Leucocytozoon is rare.…”