Varroosis is an ectoparasitosis of adult bees and bee larvae.
The pathogen responsible is Varroa
destructor, this parasite has a sexual dimorphism. The female of the parasite
is larger than the male and their morphology is perfectly adapted to their host
et. al 2010). Their life cycle is missing a free-living
stage and can be divided into two main
phases. First one is the phoretic stage, located on the adult bees, this stage
is used by the female of the parasite in order to infestate other larva cells or other colonies of bees, at this stage the adult bee is used as a
carrier and as food source (Rosenkranz et. al 2010, Piou et. al. 2016).
After a certain amount of time (that may vary between one and ten days)
the female mite switches to the reproduction phase leaving the adult bee and
entering a cell with brood larva (Piou et. al. 2016). According to Rosenkranz et. al 2010 and Kuenen and Calderone, 2000 the mite
prefers the brood larva in detriment of worker larva because the brood larva
has a longer period of incubation and that gives the mite more time to reproduce (Rosenkranz et. al 2010; Kuenen and
Calderone, 2000; Martin and Cook, 1996).
cycle of the mite is perfectly adapted to
its host, and the female mite enters a brood cell a few hours before the cell
is closed. A few hours after the cell is sealed the female feeds of the brood
larva hemolymph. This step is necessary to activate its ovary system and in
less than three days after the cell is closed appears the first egg (which is
always a haploid male mite), after that she lays up to 5 eggs at regular
intervals of approximately 30h each. The mother and her offspring continue to
feed with the hemolymph of the bee larva and the male mite will mate with his
sisters, except the case in which two adult female mites infest the same
cell (Frey et. al. 2013; Andino et. al.,
host of the parasite is Apis cerana
and until the mite infestation started to produce economical damage to the
beekeepers at the end of the 20th century, the parasite had little attention.
At first, the mite responsible for the damage of the colonies was considered V. jacopsoni, and only after further
studies was revealed the existence of more families of Varroa and has been
concluded that the mite responsible for the damage is V. destructor (Anderson and Trueman, 2000).