**2. Honeybee diseases**

Honeybees are affected by fungal, bacterial, viral (Thai Sac brood) and acarine (*Varroa*) diseases. Antibiotics are generally used to fight bacterial and fungal diseases such as American foulbrood, European foulbrood and nosemosis [3].

American foulbrood is by far the most virulent brood disease known in honeybees. The disease is caused by the spore-forming bacterium, *Paenibacillus larvae*. Larvae up to 3 days old become infected by ingesting spores that are present in their food. Spores germinate in the gut of the larva and the vegetative form of the bacteria begins to grow, taking its nourishment from the larva. Infected larvae normally die after their cell is sealed. The vegetative form of the bacterium, before to die, produces many millions of spores which are extremely resistant to desiccation and can remain viable for more than 40 years in honey and beekeeping equipment. Because of this persistence, in most countries official apiary inspectors are required to burn all infected colonies. Other countries (e.g. USA, Canada, and Argentina) allow the use of antibiotics, such as oxytetracycline and tylosin, to keep the disease in control. However, antibiotics are not a cure or a treatment of the infection since they affect only the vegetative stage of American foulbrood, inhibiting its development in the gut of the larvae. This may prevent the rapid diffusion within a colony.

European foulbrood is closely related to American foulbrood in symptomatology, and until 1906, these two diseases were not differentiated. The causative organism of European foulbrood is the bacterium *Melissococcus plutonius*, which does not produce spores, and therefore, this disease is considered less severe than American foulbrood. European foulbrood occurs primarily in spring when numbers of *M. plutonius* reach their peak. The bacterium is ingested by honey bee larvae and it replicates in mid-gut. If the bacteria out-compete the larva, the larva will die before the cell is capped. Alternatively, the bee may survive until adulthood if the larvae has sufficient food resources. Some antimicrobials, for example, oxytetracycline, have been demonstrated to be an effective treatment.

Nosemosis, caused by the fungus *Nosema apis* or *Nosema ceranae*, is historically considered the most serious disease of adult bees. Infection is acquired when spores are swallowed by bees and infect the epithelial cells of the hind gut, giving rise rapidly to large numbers of spores and impairing the digestion of pollen which shortens the life of honeybees. *N. ceranae* was originally a parasite of the Asian honeybee (*Apis cerana*), but now is widespread in some European regions, too. In recent years, the disappearance of adult honeybees, known as colony collapse disorder, has been devastating a great number of beehives worldwide. This problem has caused serious damage to apiculture and also to agricultural activities that use honeybees as pollinators. Among the possible causes of the disappearance of honeybees, nosemosis has been reported as a primary candidate.
