Such lethal infections were frequently reported in immunologically naive hosts, which are highly susceptible to infection, e.g. For example, Plasmodium infections can result in excessive multiplication of parasites in various organs including the brain, where meronts cause blockage of capillaries, ultimately leading to death of the host. Generally, haemosporidian infection is subclinical in birds however, it is well established that parasites not only cause haematological disorders but can also elicit severe damage to organs due to marked merogony in tissues. The pathogenic impact of haemosporidians on the host can be variable at different developmental stages, and severity of infection in avian hosts depends on many factors. Haemosporidians always undergo exo-erythrocytic merogony producing meronts in tissue cells before they infect blood cells and form gametocytes, the parasite stage infective for vectors. The life-cycle of haemosporidians in the avian host includes development both in tissues (exo-erythrocytic merogony) and blood cells. The majority of described parasites belong to the genera Plasmodium, Haemoproteus and Leucocytozoon, comprising more than 200 morphologically distinct species. ConclusionsĬhromogenic in situ hybridization using 18S ribosomal RNA-specific oligonucleotide probes reliably identifies and discriminates Haemoproteus and Leucocytozoon parasites in tissue sections and enables unequivocal diagnosis of haemosporidioses.Īvian haemosporidian parasites (Haemosporida) are widespread almost all over the world and infect birds of diverse families and orders. Cross-reactivity of the probes was ruled out by negative chromogenic in situ hybridization when applied to samples positive for a parasite of a genus different from the probes’ target. Binding of probes to parasites was consistent with detection of the same exo-erythrocytic meronts in consecutive haematoxylin–eosin-stained sections. Parahaemoproteus- and Leucocytozoon-specific probes labelled erythrocytic and exo-erythrocytic stages of Haemoproteus spp. To confirm the presence of parasites at sites of probe hybridization, consecutive sections were stained with haematoxylin–eosin and examined. (subgenus Leucocytozoon) and were in situ hybridized to sections from formalin-fixed, paraffin-embedded tissue samples determined positive for these parasites by PCR and histopathology. Parasite subgenus-specific oligonucleotide probes were designed to target the 18S ribosomal RNA of Haemoproteus species (subgenus Parahaemoproteus) and Leucocytozoon spp. in histological sections using chromogenic in situ hybridization. Therefore, the present study aimed at developing specific molecular probes for the identification of Haemoproteus spp. However, sequences frequently are not reliably obtained and the generic discrimination of exo-erythrocytic tissue stages based on morphological characters is challenging. Diagnosis of lethal infections is currently accomplished by the detection of parasites’ tissue stages in histological sections combined with PCR and sequencing. Notably, the development of megalomeronts by species of Haemoproteus and Leucocytozoon has been associated with mortalities in birds. Avian haemosporidian parasites can cause severe disease in their hosts due to excessive exo-erythrocytic merogony and anaemia caused by blood stages.
0 Comments
Leave a Reply. |