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

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.

Migratory birds as vehicles for parasite dispersal? Infection by avian haemosporidians over the year and throughout the range of a long‐distance migrant

“…Our data on the distribution of lineages across periods in juvenile birds indicate that transmission is likely occurring mostly on the breeding grounds Sorensen et al, 2016), where the most prevalent lineages infecting Grey-cheeked Thrush are shared with other species of boreal birds (Dodge et al, 2013;Loiseau et al, 2012;Oakgrove et al, 2014). (Ishtiaq, Bowden, & Jhala, 2017;Ishtiaq et al, 2008;. To our knowledge, ours is the first study addressing the dynamics of infection by haemosporidian parasites across the annual cycle of a long-distance migratory songbird in the Nearctic-Neotropical system and provides evidence consistent with previous findings in the Euro-African system that, aside from a few wide-ranging and generalist lineages, most parasites do not easily spread over continents and mostly remain confined to particular hosts or assemblages (Hellgren et al, 2007;Ricklefs et al, 2016;Valkiūnas, 2005).…”

“…Information about vector diversity, distribution, and specificity is critical to understand whether the apparent barriers for parasite dispersal across regions and species evidenced in our study result from inability of parasites to infect novel hosts due to differences in factors such as host immunity or whether the potential for infection is not realized owing to restrictions imposed by vector availability and suitability. Work involving vector assemblages is thus an open field to make important advances in the understanding of parasite dispersal in the Nearctic–Neotropical migratory system, particularly at wintering and stopover sites (Ishtiaq, Bowden, & Jhala, ; Ishtiaq et al., ; Ricklefs et al., ). To our knowledge, ours is the first study addressing the dynamics of infection by haemosporidian parasites across the annual cycle of a long‐distance migratory songbird in the Nearctic–Neotropical system and provides evidence consistent with previous findings in the Euro‐African system that, aside from a few wide‐ranging and generalist lineages, most parasites do not easily spread over continents and mostly remain confined to particular hosts or assemblages (Hellgren et al., ; Ricklefs et al., ; Valkiūnas, ).…”

Geographical and host species barriers differentially affect generalist and specialist parasite community structure in a tropical sky-island archipelago

“…We present one of the first comprehensive investigations of avian haemosporidian dynamics in the Indian subcontinent (see also [66]) by sampling almost the entire bird community in an important biodiversity hotspot. Here, we addressed the differential effects of geographical, climatic, and host species barriers in shaping generalist and specialist haemosporidian parasite community structure.…”

Do avian blood parasites influence hypoxia physiology in a high elevation environment?

“…Seasonal variation in ambient temperature, influences host condition through an increase in energy demands [ 23 ], leading to stress, and thereby increasing susceptibility to infection [ 24 ]. In addition, host and vector abundance govern the frequency-dependent transmission of the pathogens [ 22 , 25 – 28 ]. Cosgrove et al [ 29 ] showed a marked seasonality in Plasmodium transmission in temperate environments, which appears to result in zero prevalence estimates in winters.…”