New Findings on the Developmental Process of Ascogregarina Taiwanensis and Ascogregarina Culicis in Aedes Albopictus and Aedes Aegypti

Abstract

Infection in different stages of larvae of Aedes aegypti and Ae. albopictus with Ascogregarina taiwanensis and A. culicis, respectively, revealed that the oocysts of Ascogregarina spp. are able to infect any instar and can complete their life cycle within 9.5 +/- 1 days. When early instars ingested oocysts, parasite development was synchronized to larval-pupal ecdysis and oocyst dissemination occurred at the time of adult emergence, oviposition, or both. The parasites also developed normally when infecting 2nd, 3rd, and early 4th instars and oocysts were released only during oviposition. The parasitic development stopped at the gamont stage when oocysts were ingested by late 4th instars (6 days old). The release of sporozoites in the midgut of any larval stage started within 45 min of oocyst ingestion. About 98% of oocysts of both A. taiwanensis and A. culicis were emptied within 2-3 h of their ingestion in their respective hosts. The oocysts of both species remained viable on desiccated filter paper stored at 27 degrees C and 65 +/- 5% relative humidity, indicating that the oocysts were resistant to dryness. The oocysts of A. culicis could survive up to 6 months, whereas those of A. taiwanensis survived up to 4 months. These biological characteristics relating to parasite development might enhance the distribution of Ascogregarina spp. widely in nature and facilitate the species to be considered for biological control of Aedes mosquitoes in the future.

Infectious Dose Affects the Outcome of the Within‐Host Competition between Parasites

“…The parasite goes through two developmental stages before producing infectious oocysts again. If infection occurs in the first days of larval life, all oocysts are produced approximately 24 h before the host's emergence (Roychoudhury and Kobayashi 2006). If infection occurs later, the oocysts are formed after emergence.…”

Cost of co-infection controlled by infectious dose combinations and food availability

“…Larvae are infected by ingesting the parasite's oocysts along with their food. The parasite has two modes of transmission (Roychoudhury and Kobayashi 2006). First, local transmission occurs when pupae or emerging mosquitoes that harbor oocysts die in the breeding site or when oocysts are released as adults emerge.…”

Further study on Ascogregarina culicis in temperate Argentina: Prevalence and intensity in Aedes aegypti larvae and pupae

“…Laboratory studies suggested that high water temperatures reduce trophozoite survival (Mourya et al, 2004) and oocyst viability (McCray et al, 1970). In the same way, long periods of dryness could have a central role on oocyst viability (Roychoudhury and Kobayashi, 2006) and similar responses occur in Ascogregarina taiwanensis and Ascogregarina barreti infecting Aedes albopictus and Ochlerotatus triseriatus, respectively (Chen and Yang, 1996;Van Rhein et al, 2000). These studies usually quantified parasite population by estimating prevalence and intensity in larvae, but information regarding infection in pupae or adults is lacking.…”