LAUSR

Parathelohania is a genus of microsporidia that preferentially attacks Anopheline mosquitoes. This study explored some selective aspects of the epizootiology 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 accompanied 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-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.