Susceptibility of wild and colonized Anopheles stephensi to Plasmodium vivax infection

Abstract

Abstract Background As much as 80% of global Plasmodium vivax infections occur in South Asia and there is a shortage of direct studies on infectivity of P. vivax in Anopheles stephensi, the most common urban mosquito carrying human malaria. In this quest, the possible effects of laboratory colonization of mosquitoes on infectivity and development of P. vivax is of interest given that colonized mosquitoes can be genetically less divergent than the field population from which they originated. Methods Patient-derived P. vivax infected blood was fed to age-matched wild and colonized An. stephensi. Such a comparison requires coordinated availability of same-age wild and colonized mosquito populations. Here, P. vivax infection are studied in colonized An. stephensi in their 66th–86th generation and fresh field-caught An. stephensi. Wild mosquitoes were caught as larvae and pupae and allowed to develop into adult mosquitoes in the insectary. Parasite development to oocyst and sporozoite stages were assessed on days 7/8 and 12/13, respectively. Results While there were batch to batch variations in infectivity of individual patient-derived P. vivax samples, both wild and colonized An. stephensi were roughly equally susceptible to oocyst stage Plasmodium infection. At the level of sporozoite development, significantly more mosquitoes with sporozoite load of 4+ were seen in wild than in colonized populations. Conclusions Overall at the level of oocyst development, significant difference was found between the colonized and wild Anopheles stephensi in their susceptibility to P. vivax. For initial understanding of infections with local strains of P. vivax, colonized Anopheles stephensi will serve as a good model. For experiments, where high number of sporozoites are necessary, wild mosquitoes provide distinct advantage over the colonized vector populations. Understanding the molecular mechanism modulating this variability between these two populations will be prime area of focus in future studies.

Keywords

• Plasmodium vivax
• Anopheles stephensi
• Oocysts
• Sporozoites
• Wild populations
• Colonized populations