Seasonal dynamics in mosquito abundance and temperature do not influence avian malaria prevalence in the Himalayan foothills.

Farah Ishtiaq,Christopher G R Bowden,Yadvendradev V Jhala

doi:10.1002/ece3.3319

Abstract

We examined seasonal prevalence in avian haemosporidians (Plasmodium and Haemoproteus) in migrant and resident birds in western Himalaya, India. We investigated how infection with haemosporidians in avian hosts is associated with temporal changes in temperature and mosquito abundance along with host abundance and life‐history traits (body mass). Using molecular methods for parasite detection and sequencing partial cytochrome b gene, 12 Plasmodium and 27 Haemoproteus lineages were isolated. Our 1‐year study from December 2008 to December 2009 in tropical Himalayan foothills revealed a lack of seasonal variation in Plasmodium spp. prevalence in birds despite a strong correlation between mosquito abundance and temperature. The probability of infection with Plasmodium decreased with increase in temperature. Total parasite prevalence and specifically Plasmodium prevalence showed an increase with average avian body mass. In addition, total prevalence exhibited a U‐shaped relationship with avian host abundance. There was no difference in prevalence of Plasmodium spp. or Haemoproteus spp. across altitudes; parasite prevalence in high‐altitude locations was mainly driven by the seasonal migrants. One Haemoproteus lineage showed cross‐species infections between migrant and resident birds. This is the first molecular study in the tropical Himalayan bird community that emphasizes the importance of studying seasonal variation in parasite prevalence. Our study provides a basis for further evolutionary study on the epidemiology of avian malaria and spread of disease across Himalayan bird communities, which may not have been exposed to vectors and parasites throughout the year, with consequential implications to the risk of infection to naïve resident birds in high altitude.

Highlights

Parasite prevalence is a fundamental measure required to understand the temporal and spatial variations and epidemiology of infectious diseases (Ishtiaq, Rao, Huang, & Bensch, 2017; Scheuerlein & Ricklefs, 2004; Wood et al, 2007)
Given that suitable vectors are present to transmit and maintain the infection, migrants can form an effective bridge for parasites between wintering and breeding grounds, increasing the risk of infection to naïve resident birds at the higher altitudes. In this first molecular study on Plasmodium and Haemoproteus prevalence across resident and migrant birds, we aimed to explore the seasonal dynamics in parasite prevalence and its association with seasonal environmental drivers and host life-history traits
Our study is the first seasonal study in the tropics which captures the absence of seasonal pattern in prevalence of avian Plasmodium spp

Summary

Introduction

Parasite prevalence is a fundamental measure required to understand the temporal and spatial variations and epidemiology of infectious diseases (Ishtiaq, Rao, Huang, & Bensch, 2017; Scheuerlein & Ricklefs, 2004; Wood et al, 2007). Plasmodium and Haemoproteus parasites reproduce sexually in dipteran vectors—culicid mosquitoes and ceratopogonid midges, respectively (Valkinũas, 2005)—and use birds as intermediate hosts in which they undergo asexual reproduction Parasites in both genera have been shown to be pathogenic to their avian hosts (Atkinson & van Riper, 1991; Bennett et al 1993; Warner 1968) with deleterious effects on health and reproductive success (e.g., Marzal, De Lope, Navarro, & Møller, 2005) and body condition (Valkinũas, Zickus, Shapoval, & Iezhova, 2006), and possibly lead to extinction in immunologically naive hosts (Atkinson, Dusek, Woods, & Iko, 2000; Samuel et al, 2011). These parasites play a significant selective factor in bird populations and exert strong selection pressure on host life-history traits

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