Calculation of the extrinsic incubation period (EIP)
The EIP was calculated using mean daily temperature and mean hourly
temperature for P. falciparum , P. vivax , P.
relictum , Leucocytozoon and Haemoproteus parasites. The
mean hourly temperature is used to estimate the effect of diurnal
temperature fluctuation on EIP. The diurnal temperature range (DTR)
variation across these four sites is the difference between maximum and
minimum temperatures on each day of the month at each site. This was
done for each day of the month for all four sites. Since all four sites
are at different elevations, it is possible that for a few days of a
month, the temperature was marginally above the minimum threshold
temperature for the development of parasites. The EIP calculated using
these temperatures can thus become anomalously high. We thus set the EIP
to 90 days whenever the computed EIP exceeded that number. We calculated
the mean EIP using both the mean daily temperature as well as mean
hourly temperatures for the month with the following procedure: We
calculate the EIP using the mean temperature for each day of the month.
We then average this EIP over the entire month. We use a similar
procedure for the mean hourly temperature. We set the upper threshold
temperature to about 5oC above the maximum threshold
temperature (Tmax) following Hu and Appel (2004) and
Cator et al . (2013). The upper threshold temperature is lethal
for parasite development. Once the temperature exceeds this lethal
temperature the development of parasites does not occur and no estimate
of EIP is possible.