Omrani Seyed-Mohammad, Nematollahi Nooshafarin
Department of Medical Parasitology, School of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Islamic Republic of Iran.
Department of Medical Parasitology, School of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Islamic Republic of Iran.
J Invertebr Pathol. 2022 Oct;194:107823. doi: 10.1016/j.jip.2022.107823. Epub 2022 Aug 30.
Parathelohania is a genus of microsporidia that preferentially attacks Anopheline mosquitoes. This study explored some selective aspects of the epizootiology of Parathelohania iranica (Microsporidia: Amblyosporidae) in its malaria mosquito host Anopheles superpictus s.l. (Diptera: Culicidae). For this study, Sar-rok Village, a place adjacent to the type locality of the parasite, located at the central western part of Iran was visited twice a month to collect host larvae from mid-summer to mid-autumn of 2017-2021. Patent infections were detected by the whitish discoloration of the involved segments. Superficially uninfected larvae were reared up to 26 days in the insectary to elucidate hidden infections. Molecular investigation and laboratory trials were conducted to evaluate the possibility of secondary infections in subsequent days. Morphological characters were used to determine the sex of larvae and adults. Data were entered in SPSS 23.0 and analyzed with relevant statistical tests as needed. In total, 584 P. iranica infected larvae of An. superpictus s.l. were collected in the study years at day zero (D0). Extended observations in the insectary revealed that 849 larvae (84.2 %), 22 dead pupae (2.2 %), and 137 emerged adults (13.6 %) were also infected. In the first two years of the study, the mean infection rate for D0 and D0 + D1-D26 infections was 6.25 % and 15.6 %, respectively. Exposure experiments indicated that subsequent infections in larvae (D1-D26) were not affected by a possible source in the accompanying field water. Patent (D0) infections were seasonal and had about a month delay compared to the general population of larvae. Concealed infections of larvae (D1-D26) were significantly more frequent in late mosquito season (P < 0.01). It is proposed that the gradual decrease of ambient temperature and the shortening of day length postpones the growth and development of P. iranica in the affected larvae. Both sexes of larvae were involved and none of them survived beyond a couple of days. The frequency of infections in adult males (5.8 %) were significantly more than females (4 %) (P = 0.02). The infections of larvae were more common in the late mosquito season, and the infections of adults were more frequent in the early mosquito season. This suggests the relative importance of vertical and horizontal routes of transmission in early and late mosquito seasons, respectively. However, age-specific data revealed that only 26 % of hidden infections of larvae (D1-D26) were stemmed from I to II age group. This implies that the vertical route may be less efficient than the horizontal route in the transmission of P. iranica to the mosquito host. These inferences should be verified with further field and laboratory investigations.
副嗜碘孢虫属是一类微孢子虫，主要侵袭按蚊。本研究探讨了伊朗副嗜碘孢虫（微孢子虫：微孢子虫科）在其疟疾蚊宿主——伪杂鳞库蚊复合组（双翅目：蚊科）中的一些流行病史学的选择性方面。在本研究中，位于伊朗中西部、毗邻该寄生虫模式产地的萨尔罗克村，于2017年至2021年的仲夏到仲秋期间每月两次进行走访，以收集宿主幼虫。通过感染部位的白色变色来检测显性感染。将表面未感染的幼虫在昆虫饲养室饲养26天，以阐明潜在感染情况。进行了分子研究和实验室试验，以评估后续几天继发感染的可能性。利用形态学特征来确定幼虫和成虫的性别。数据录入SPSS 23.0，并根据需要进行相关统计检验分析。在研究年份的第零天（D0），共收集到584只感染伊朗副嗜碘孢虫的伪杂鳞库蚊复合组幼虫。在昆虫饲养室的进一步观察显示，849只幼虫（84.2%）、22只死亡蛹（2.2%）和137只羽化的成虫（13.6%）也受到了感染。在研究的前两年，D0和D0 + D1 - D26感染的平均感染率分别为6.25%和15.6%。暴露实验表明，幼虫在后续（D1 - D26）的感染不受伴随田间水体中可能来源的影响。显性（D0）感染具有季节性，与幼虫总体数量相比有大约一个月的延迟。幼虫的潜在感染（D1 - D26）在蚊虫季节后期显著更频繁（P < 0.01）。据推测，环境温度的逐渐降低和日照时长的缩短推迟了伊朗副嗜碘孢虫在受影响幼虫体内的生长和发育。幼虫的雌雄两性均受影响，且无一能存活超过几天。成年雄性的感染频率（5.8%）显著高于雌性（4%）（P = 0.02）。幼虫感染在蚊虫季节后期更为常见，而成虫感染在蚊虫季节早期更为频繁。这分别表明了垂直传播和水平传播途径在蚊虫季节早期和后期的相对重要性。然而，按年龄特异性数据显示，幼虫的潜在感染（D1 - D26）中只有26%来自I至II龄组。这意味着在伊朗副嗜碘孢虫传播至蚊虫宿主的过程中，垂直传播途径可能不如水平传播途径有效。这些推论应通过进一步的野外和实验室研究加以验证。
