Abstract
Environmental temperature is a key driver of malaria transmission
dynamics. Using detailed temperature records from four sites
(1800-3200m) in the western Himalaya, we model how temperature regulates
parasite development rate (the inverse of the extrinsic incubation
period, EIP) in the wild. Using a BriƩre parametrization of the EIP,
combined with Bayesian parameter inference, we study the thermal limits
of transmission for avian (P. relictum ) and humanPlasmodium parasites (P. vivax and P. falciparum )
as well as for two malaria-like avian parasites, Haemoproteus andLeucocytozoon . We demonstrate that temperature conditions can
substantially alter the incubation period of parasites at high elevation
sites (2600-3200m) leading to restricted parasite development or long
transmission windows. We then compare estimates of EIP based on measures
of mean temperature versus hourly temperatures to show that EIP days
vary in cold versus warm environments. We found that humanPlasmodium parasites experience a limited transmission window at
2600m. In contrast, for avian Plasmodium transmission was not
possible between September to March at 2600m. In addition, temperature
conditions suitable for both Haemoproteus andLeucocytozoon transmission were obtained from June to August and
in April, at 2600m. Finally, we use temperature projections from a suite
of climate models to predict that by 2040, high elevation sites
(~ 2600 m) will have a temperature range conducive for
malaria transmission, albeit with a limited transmission window. Our
study highlights the importance of accounting for fine-scale thermal
effects in the expansion of the range of the malaria parasite with
global climate change.
Key words: Climate change, Extrinsic Incubation Period,
Malaria, Western Himalaya