Data from: Infection with Haemoproteus iwa affects vector movement in a hippoboscid fly – frigatebird system

Haemosporidian parasites, which require both a vertebrate and invertebrate host, are most commonly studied in the life stages occurring in the vertebrate. However, aspects of the vector's behavior and biology can have profound effects on the parasite dynamics. Here we explore the effects of a haemosporidian parasite, Haemoproteusiwa, on a hippoboscid fly vector, Olfersiaspinifera. Olfersiaspinifera is an obligate ectoparasite of the great frigatebird, Fregata minor, living among bird feathers for all of its adult life. This study examines the movements of O. spiniferabetween great frigatebird hosts. Movement, or host-switching, was inferred by identifying host (frigatebird) microsatellite genotypesfrom fly bloodmeals that did not match the host from which the fly was collected. Such host-switches were analyzed using a logistic regression model, and the best-fit model included the H. iwa infection status of the fly and the bird host sex. Uninfected flies are more likely to have a bird genotype in their blood meal that was different from their current host's genotype (i.e., to have switched hosts) than infected flies. Flies collected from female birds were more likely to have switched hosts than those collected on males. Reduced movement of infected flies suggests that there may be a cost of parasitism for the fly. The effect of host sex is likely driven by differences in the sex ratio of bird hosts available to moving flies.

血孢子虫（Haemosporidian parasites）需同时以脊椎动物与无脊椎动物作为宿主，当前相关研究多聚焦于其在脊椎动物体内的生活史阶段。然而，媒介昆虫的行为与生物学特性可对寄生虫种群动态产生深远影响。本研究探讨了血孢子虫——血变原虫（Haemoproteus iwa）对其虱蝇媒介刺颚虱蝇（Olfersia spinifera）的作用。刺颚虱蝇是大军舰鸟（Fregata minor）的专性外寄生虫，成虫阶段全程栖息于军舰鸟的羽毛之间。本研究针对刺颚虱蝇在大军舰鸟宿主间的移动行为展开分析：通过比对蝇类血餐的宿主（军舰鸟）微卫星基因型与采集该蝇类的原宿主基因型，推断其宿主转换（host-switching）事件——即血餐基因型与当前宿主基因型不匹配的情况。研究采用逻辑回归模型（logistic regression model）对这类宿主转换事件进行分析，最终最优拟合模型纳入了蝇类的H. iwa感染状态以及鸟类宿主的性别两个因素。结果显示，未感染的蝇类相较于感染个体，其血餐中出现与当前宿主不同的鸟类基因型（即发生宿主转换）的概率更高；从雌性军舰鸟体内采集的蝇类，其发生宿主转换的概率也高于取自雄性宿主的蝇类。感染蝇类的移动能力下降，提示寄生作用可能对蝇类带来了寄生代价。宿主性别所产生的影响，大概率源于移动中的蝇类可接触到的鸟类宿主性比差异。