Tchoumbou Mélanie, Iezhova Tatjana, Hernández-Lara Carolina, Duc Mélanie, Valkiūnas Gediminas
Nature Research Centre, Akademijos 2, 08412 Vilnius, Lithuania.
Nature Research Centre, Akademijos 2, 08412 Vilnius, Lithuania.
Int J Parasitol. 2025 Jan;55(1):15-26. doi: 10.1016/j.ijpara.2024.10.002. Epub 2024 Oct 10.
Haemoproteus species (Haemosporida, Haemoproteidae) are cosmopolitan blood parasites that affect bird fitness and health. Recent discoveries based on the application of molecular markers showed that exo-erythrocytic or tissue stages of haemoproteids damage various internal organs including the brain. However, the patterns of exo-erythrocytic development remain unclear for most of the described species. This study aimed to understand the exo-erythrocytic development of Haemoproteus parasites in naturally infected Thrush nightingales Luscinia luscinia (Muscicapidae). Infections were confirmed in eight bird individuals by microscopic examination and PCR-based methods. Organs were examined using histology and in situ hybridization, which applied genus-specific and lineage-specific oligonucleotide probes targeting the 18S rRNA of the parasites. Exo-erythrocytic meronts of Haemoproteus attenuatus (lineage hROBIN1) were found and described for the first known time in this avian host. Most meronts were seen in the lungs, with a few also present in the liver, heart, and pectoral muscle. The available data suggest that this parasite produces only meronts, and not megalomeronts. However, numerous megalomeronts at different stages of development were observed in the gizzard and the heart of one individual. Based on the morphology, location in organs, and diagnostics using the lineage-specific probes, the megalomeronts were attributed to Haemoproteus majoris (lineage hWW2). Two cases of empty capsular-like walls of megalomeronts were seen in the gizzard, indicating that the megalomeronts had already ruptured and degenerated. The extensive microscopic examination did not reveal gametocytes of H. majoris, obviously indicating an abortive development. Abortive haemosporidian infections were often speculated to occur in wildlife but have not been documented in naturally infected birds. This study recognised patterns in the exo-erythrocytic development of H. attenuatus, and is to our knowledge the first documentation of abortive Haemoproteus infection in a naturally infected bird during exo-erythrocytic development.
血变原虫属（血孢子虫目，血变原虫科）是一种遍布全球的血液寄生虫，会影响鸟类的健康状况。基于分子标记应用的最新发现表明，血变原虫的细胞外或组织阶段会损害包括大脑在内的各种内部器官。然而，对于大多数已描述的物种而言，细胞外发育模式仍不清楚。本研究旨在了解自然感染的欧歌鸫（Luscinia luscinia，鹟科）中血变原虫寄生虫的细胞外发育情况。通过显微镜检查和基于聚合酶链反应的方法，在8只鸟类个体中确认了感染情况。使用组织学和原位杂交技术对器官进行检查，原位杂交应用了针对寄生虫18S核糖体RNA的属特异性和谱系特异性寡核苷酸探针。在这种鸟类宿主中，首次发现并描述了attenuatus血变原虫（谱系hROBIN1）的细胞外裂殖体。大多数裂殖体见于肺部，少数也存在于肝脏、心脏和胸肌中。现有数据表明，这种寄生虫只产生裂殖体，而不产生巨型裂殖体。然而，在一只个体的砂囊和心脏中观察到了处于不同发育阶段的大量巨型裂殖体。基于形态学、在器官中的位置以及使用谱系特异性探针的诊断结果，这些巨型裂殖体被归因于majoris血变原虫（谱系hWW2）。在砂囊中发现了两例巨型裂殖体的空囊状壁，表明巨型裂殖体已经破裂并退化。广泛的显微镜检查未发现majoris血变原虫的配子体，显然表明发育失败。人们经常推测野生动物中会发生血孢子虫感染失败的情况，但在自然感染的鸟类中尚未有记录。本研究识别出了attenuatus血变原虫细胞外发育的模式，据我们所知，这是首次记录自然感染鸟类在细胞外发育过程中血变原虫感染失败的情况。
