Question

Name the protozoan disease of Mulberry silkworm.
A. Flacheria
B. Grasseria
C. Pebrine
D. Muscardine

Answer 1

Hint:-Mulberry silkworm is a monophagous insect (i.e. insect that feeds upon one species of plants) which reared on the leaves of mulberry only.
The morin (yellow colored compound) present in the leaves helps to attract the silkworm.
Protozoan disease is a disease caused by protozoa. These organisms may remain in the human host for their entire life cycle, but many carry out part of their reproductive cycle in insects or their hosts.

Complete answer:
- The most virulent protozoan disease of silkworm is Pebrine. It is named so because the infected worms show some pepper-like black spots.
- The protozoa passes its life cycle through 2 stages – the infective stage and vegetative stage.
- The disease is transmitted to silkworm in three different ways:
1. Oral: Spores from the faeces of infected worms contaminate the mulberry leaves. Such leaves when taken by other larvae, they get infected.
2. Contact: Larvae may get infection through their skin from the rearing bed contaminated with faecal matter or dead tissues.
3. Transovarial: If the infection occurs in the 5th stage, the adult moth normally emerges through the pupal stage. Thus, the egg itself acquires infection from the mother and hatches into primary infected larvae.
- Live infected pupae present in cocoons may show black, swollen bodies with black spots on sides of the abdomen.
- Pebrine infected adult moths show black spots on abdomen, deformed antennae, unstretched and discoloured wings.

Flacherie is a bacterial disease of mulberry silkworm. So, this is not a correct option.
Grasseria is a viral disease caused by a virus called Borrelina. Therefore, this option is also incorrect.
Muscardine is a fungal disease. Therefore, this option is not correct.

Pebrine is a correct option as it is a protozoan disease of mulberry silkworm.

Note:- Disease larvae if detected in a rearing bed should be immediately removed and burnt. Adult moths showing symptoms of pebrine should not be undertaken for any sericultural processes. By advanced immune enzymatic methods, presence of pebrine spores can be detected quickly.