One of the more striking features of colony collapse is the sudden
abandonment of the hives. Speculation has surrounded the idea that
damage to the nervous system by pesticides could cause the bees to
become lost. Other possibilities include deliberate suicide to rid the
hive of pathogens. A third scenario has arisen, whereby parasites
manipulate the hosts in order to propagate themselves. Any number of
parasites could benefit from widespread dispersal by causing bees to
abandon their hives and widely distribute themselves, spreading the
pathogen over a very broad area. Additionally, bees drifting into
other colonies obviously would enable parasites to spread rapidly.
This drifting behavior could be manipulated by pathogens in the honey
bee.

Excerpts from "Manipulation of Host Behavior by Parasitic Insects and
Insect Parasites" by Frederic Libersat, et al (source: Annu. Rev.
Entomol. 2009. 54:189–207)

Parasites often alter the behavior of their hosts in ways that are
ultimately beneficial to the parasite or its offspring. Among these,
we describe how a worm may influence the nervous system of its cricket
host and manipulate the cricket into committing suicide by jumping
into water.

Parasites have evolved remarkable strategies to manipulate the
behavior of their hosts in order to perpetuate their own genes. Among
the most dramatic cases of such manipulation are those that take place
in parasitized insects. Because it is the nervous system that
generates behavior, for a given behavioral manipulation to occur,
parasites must manufacture chemicals that in one way or another affect
the CNS [central nervous system] of their hosts. Over time, several
extreme forms of behavioral manipulation have evolved in which the
parasite eventually controls the ‘free will’ of its host. Some
parasitic fungi and worms manipulate their hosts in a way that
ultimately leads to suicidal behavior.

1. Adult nematomorphs need an aquatic environment for successful
reproduction. Infected hosts are thus manipulated in their behavior to
actively seek water and to jump in—which leads to the host’s death.

2. Parasites interfere with the CNS of their hosts. In particular,
certain free amino acids and certain protein families involved in the
brain development of the host undergo significant changes during the
manipulation process.

3. Parasitoproteomics revealed that parasite proteins are expressed in
the brain of the host. This molecular mimicry includes Wnt proteins
that are also primarily involved in brain development.

-- 
Peter Loring Borst
Ithaca, NY  USA
+42.347999, -76.495239

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