The activity of arthropod parasites is dependent on the temperature and relative humidity of the local environment.
Ticks: the activity period is the period during which ticks are actively seeking and infesting their hosts in order to take their blood meal and it is the critical time for disease transmission. The infestation risk for an animal is therefore maximal when the climate is optimal and leads to the presence of ticks.
Fleas: the activity period is the period during which the development from eggs to larvae and then pupae is maximal. The population of fleas will be growing rapidly.
The model focuses on what happens outside (gardens, bushes, parks etc) but cannot take into account the activity of fleas on animals (in warm fur) or in houses (heated during winter).
The activity index is used to construct the activity forecast maps of the arthropod parasites for the week (only outdoor). Five levels of arthropod activity are represented on a scale from 0 to 100 : (0-20), (20-40), (40-60), (60-80) and (80-100).
Activity index calculation
Given that arthropod parasite activity is low at night, only meteorological data from 6:00 AM to 6:00 PM are used. These data correspond to the ECMWF outputs at 12:00 and 18:00 hours.
To apply these weighting factors, the ECMWF model refers to biotope maps from the filter maps adapted from LANMAP. To calculate the biological activity during the previous week (W-1), the following formula can be used:
W-1 = AveragehєW-1 abacus(Th, RHh) × Weightvegetation
To calculate the biological activity for the week ahead (W), the same formula can be used except that it is based on the Monday morning forecast.
W = AveragehєW-1 abacus(Th, RHh) × Weightvegetation
(h indicating the hours used for the calculation of week W-1 (h=12:00 and 18:00))