During an
infection locusts behaviourally
fever by seeking out higher environmental temperatures. This behaviour places the pathogen at sub-optimal growth temperatures while improving the efficiency of the immune system, thereby prolonging the lifespan of the host. It is therefore in the interest of the pathogen to either adapt to
fever-like temperatures or to evolve mechanisms to interfere with, or inhibit
fever. We investigated the behavioural
fever response of desert locusts to two fungal pathogens. A prolonged
fever was observed in locusts infected with Metarhizium acridum. However,
fever was comparatively short-lived during
infection with Metarhizium robertsii. In both cases restriction of thermoregulation reduced lifespan.
Destruxin A (
dtx A) produced by M. robertsii, but not M. acridum has previously been associated with the inhibition of the insect immune system. Injection of
dtx A during
infection with the
fever-causing M. acridum inhibited
fever and was particularly effective when administered early on in
infection. Furthermore, locusts injected with
dtx A were more susceptible to M. acridum
infection. Therefore engineering M. acridum isolates currently used for locust biocontrol, to express
dtx A may improve efficiency of control by interfering with
fever.