Question

Nosema bombycis that causes pebrine in silkworms is a
(a) Fungus
(b) Virus
(c) Bacteria
(d) Protozoan

Answer 1

Hint: The pebrine or pepper disease is a fatal disease of the silkworms. It doesn't directly infect them but infects the mother moth that gives rise to infected eggs, which dies in the larval stage. This was first recognized in France.

Complete step by step answer:
The protozoan named Nosema bombycis causes pebrine diseases in silkworms. This is a reason for great economical damage in Sericulture. It is also known as Pepper disease of silkworms. It is also caused to a lesser extent by Vairimorpha, Pleistophora, and Thelohania species.

Additional Information: The larva of silkworms is most prone to pebrine or pepper disease. But it doesn't affect the larvae directly. The cause of this disease, the Nosema bombycis protozoa, enters the body of the silkworm from their food at their larval stage. However, they stay symptomless in that generation and get passed down by the mother moth to the eggs. When the worms hatch from these infected eggs, they die in their larval stage. These larvas are usually covered in brown patches and aren't able to produce silkworms. It is a very dangerous disease to the silkworms and causes a great deal of damage to the Sericulture industry. So, it is very important to rule out the eggs from the mother moth. This fatal disease was first recognized by Antoine Béchamp, a French scientist, during the pebrine plague across France.
Therefore, the correct answer is protozoan.

Note: The Nosema bombycis in the mother moth can be found out by examining the moth's body fluid under the microscope. Other microsporidians (spore-forming protozoans) such as Vairimorpha and Pleistophora can also cause disease in moths. The species of the Nosema genus can cause disease in other insects like Mosquitoes, honey bees, bumblebees, etc.
The image shows the dark-spotted infected silkworm larvae