Valkiūnas Gediminas, Iezhova Tatjana A, Palinauskas Vaidas, Ilgūnas Mikas, Bernotienė Rasa
Nature Research Centre, Akademijos 2, Vilnius 21, 08412, Lithuania,
Parasitol Res. 2015 Aug;114(8):2903-9. doi: 10.1007/s00436-015-4491-2. Epub 2015 May 6.
Avian haemosporidian parasites of the genus Haemoproteus (Haemoproteidae, Haemosporida) are widespread, and some species cause diseases both in vertebrate hosts and blood-sucking insects. Parasitemia of Haemoproteus species usually is long-lasting, with gametocytes present in the circulation for several months. However, the viability of gametocytes and their ability to produce sexual cells have been insufficiently understood in the course of parasitemia. We initiated the sexual development in vitro conditions and calculated proportions of normal and anomalous ookinetes, which developed in two species of Haemoproteus. Mature gametocytes of the parasites were obtained from naturally infected avian hosts at different days of parasitemia. Haemoproteus (Parahaemoproteus) lanii (cytochrome b lineage hRB1) was isolated from one red-backed shrike Lanius collurio. Two isolates of Haemoproteus (Parahaemoproteus) tartakovskyi (cytochrome b lineage hSISKIN1) were used: one was obtained from a siskin Carduelis spinus and one from a common crossbill Loxia curvirostra. The wild-caught birds were kept indoors under controlled conditions, and blood was taken from them every 1 or 2 days during 10-14 days. After each blood sampling, the sexual process and ookinete development were initiated in vitro by exposure of infected blood containing mature gametocytes to air. Smears were prepared at intervals of 15 min, 3 h, and 12 h after the exposure; they were examined microscopically. In all, 25 experiments were performed; each experiment was repeated two times. The ratios of macro- and microgametocytes did not change in all experimental infections during this study. Sexual process occurred, and both normal and anomalous ookinetes developed in all parasites. The proportion of normal ookinetes did not change significantly in both isolates of H. tartakovskyi. Between 8 and 10 days of observation, the proportion of normal ookinetes of H. lanii decreased 6 times compared to the beginning of the experiment. That was accompanied with the rapid decrease of parasitemia and the inability of the majority of mature gametocytes to escape from erythrocytes and produce gametes, indicating disorder of the gametogenesis. There was clear difference in the gametogenesis between H. tartakovskyi and H. lanii from this point of view. This study shows that the viability of Haemoproteus gametocytes might change dramatically in the course of parasitemia within 1-2 days, and the presence of mature gametocytes in the circulation does not necessarily indicate their ability to exflagellate and produce ookinetes. We predict that this finding is important epidemiologically due to relationship with sporogony success.
血变原虫属（血变科，血孢子虫目）的鸟类血孢子虫寄生虫分布广泛，一些物种会在脊椎动物宿主和吸血昆虫中引发疾病。血变原虫物种的虫血症通常持续时间较长，配子体在血液循环中存在数月之久。然而，在虫血症过程中，配子体的活力及其产生性细胞的能力尚未得到充分了解。我们在体外条件下启动了有性发育，并计算了在两种血变原虫中发育的正常和异常动合子的比例。寄生虫的成熟配子体从自然感染的鸟类宿主在虫血症的不同天数获得。血变原虫（副血变原虫）拉尼血变原虫（细胞色素b谱系hRB1）从一只红背伯劳（Lanius collurio）中分离得到。使用了两种血变原虫（副血变原虫）塔尔塔科夫斯基血变原虫（细胞色素b谱系hSISKIN1）的分离株：一种从黄雀（Carduelis spinus）中获得，另一种从普通交嘴雀（Loxia curvirostra）中获得。野外捕获的鸟类在可控条件下饲养在室内，在10 - 14天内每1或2天从它们身上采血。每次采血后，通过将含有成熟配子体的感染血液暴露于空气中，在体外启动有性过程和动合子发育。在暴露后15分钟、3小时和12小时间隔制备涂片；在显微镜下检查。总共进行了25次实验；每个实验重复两次。在本研究的所有实验感染中，大配子体和小配子体的比例没有变化。发生了有性过程，所有寄生虫中都发育出了正常和异常的动合子。在塔尔塔科夫斯基血变原虫的两个分离株中，正常动合子的比例没有显著变化。在观察的8至10天之间，拉尼血变原虫的正常动合子比例与实验开始时相比下降了6倍。这伴随着虫血症的迅速下降以及大多数成熟配子体无法从红细胞中逸出并产生配子，表明配子发生紊乱。从这个角度来看，塔尔塔科夫斯基血变原虫和拉尼血变原虫在配子发生方面存在明显差异。这项研究表明，血变原虫配子体的活力在虫血症过程中1 - 2天内可能会发生巨大变化，并且循环中存在成熟配子体并不一定表明它们能够进行出丝并产生动合子。我们预测，由于与孢子生殖成功的关系，这一发现在流行病学上很重要。
