Which condition is caused by two species of microsporidia?

Nosemosis is indeed caused by two species of microsporidia known as Nosema apis and Nosema ceranae. These microsporidia are intracellular parasites that infect the digestive system of honey bees, leading to a condition characterized by dysentery, reduced life expectancy, and overall declining colony health.

Nosema apis has traditionally been the more common species affecting honey bees, particularly in colder climates, but Nosema ceranae, which is more prevalent in warmer regions, has gained attention due to its association with increased mortality rates in bee populations. Both species can cause similar symptoms, often leading to significant losses within affected colonies.

In contrast, chalkbrood is a fungal disease caused by the fungus Ascosphaera apis, American foulbrood (AFB) is a bacterial disease due to the pathogen Paenibacillus larvae, and varroosis is caused by the Varroa destructor mite, which is an ectoparasite that infests bees and can transmit viruses. Thus, while all these conditions can affect honeybee health, only nosemosis is specifically linked to the microsporidia mentioned.