Data from: Climate-driven increase in transmission of a wildlife malaria parasite over the last quarter century

Climate warming is expected to influence the prevalence of
vector-transmitted parasites. Understanding the extent to which this is
ongoing, or has already occurred, requires empirical data from populations
monitored over long periods of time, but these studies are sparse.
Further, vector-disease research involving human health is often
influenced by disease control efforts that supersede natural trends. By
screening for malaria parasite infections in a wild population of blue
tits (Cyanistes caeruleus) in Northern Europe, over 26 years, we tested
whether prevalence and transmission changes were climate-driven. We found
that all three malaria parasite genera occurring in blue tits
(Haemoproteus, Plasmodium, and Leucocytozoon) have increased significantly
in their prevalence and transmission over time. The most common parasite
in the study, Haemoproteus majoris, increased in prevalence from 47%
(1996) to 92% (2021), and this was a direct consequence of warmer
temperatures elevating transmission. Climate window analyses revealed that
elevated temperatures between May 9th and June 24th, a time period that
overlaps with the host nestling period, were strongly positively
correlated with H. majoris transmission in one-year-old birds. A warming
climate during this narrow timeframe has had a demonstrable impact on
parasite transmission, and this has favored an increase in the prevalence
of parasites in wild birds in a temperate region of Europe. While more
challenging to measure, similar implications of climate warming on human
vector-disease systems might be occurring. It is therefore critical that
we understand what specific aspects of malaria parasite development and
transmission are most influenced by climate warming, for the benefit of
human and wildlife health.