Nosema bombycis is a microsporidium that kills all of the silkworms hatched from infected eggs and comes from the food that silkworms eat. ... Therefore, it is extremely important to rule out all eggs from infected moths by checking the moth's body fluid under a microscope.

1. A SERIOUS THREAT TO
SILK INDUSTRY
Akash Mishra
Msc zoology
Bbau lucknow

2.  Nosema bombycis is a microsporidian protozoa
causes PEBRINE disease of silkworm. It was first
recorded in France in 1845 and later spread to
Italy, Spain, Syria and Romania. ' It was
responsible for the collapse of the French and
Italian silkworm industry in 1865. The name
pebrine was coined by De Quadrefagues (1860)
because of pepper-like spots seen on the diseased
larvae in advanced stage of infection. The disease
is known as KATA or MATHA KATA in Bengali
and as GANTU or GANTU ROGA iii Kannaaad.

3.  The life cycle of N.bombycis includes three stages
namely SPORE, PLANONT and MERONT.Mature
spore is oval or ovocylindrical and measures 3-4
microns by 1.5-2.0 microns with 3 layered
membrane,the inner,middle and outer.they can be
observed at 600 magnification under a
microscope.the spore consists of;
 Spore membrane,which enclose the sporoplasm.
 Sporoplasmin the form of a girdle across the width
of the spore

4.  Anterior and posterior vacuoles.
 Two nuclei in the sporoplasm.
 Posterior capsule.

6.  The spores are highly refrecting appearing light green
under microscope.the spore belongs to the dormant
stage of pathogen and posses great resistance .
 The spores germinates in digestive juice of silkworm
larva and produces a long polar fillament having a
length of more than 30 times that of the lengthwise
dimension of the spore,on the end of which grows a
sporoplasm. The sporoplasm is having two nuclei and
other cell organ and posses the limiting membrane.
 The sporoplasm multiplies through fisssion, comes out
of heamolymph intracelluar space spreading to every
part of body,and lives in various system particularly in
the fat body and muscular tissue,becomes a nucleus
and form spore after multiplication through fission.

7.  The pathogen of pebrine diseases is capable to
complete its life cycle within four days.
 The pathogen parasitizes the ovary first and when
4 and 5 instar larvae after pupation and emergence
becomes moth they move into egg and after
deposition of eggs undergo multiplication and
develops into the disease in the embryo or in the
body of silkworm in next generation.
 After the deposition of eggs the pathogen grows
and multiplies within the egg.
 The mature spore is unicellular, endomembranous
differentiation of its sporoblast.

8.  Phylum -Protozoa
 Order -Microsporidia Balbiani ( 1882)
 Family -Nosematidae Labbe (1899)
 Genus -Nosema Naegeli (1857)
 Species -Nosema bombycis Naegeli (1857)

9.  Transovarial transmission and per os infection
are the two routes of pebrine infection in
silkworm.
 A-Transovarial/Embryonic/Vertical
Transmission: Embryonic infection occurs
when the pathogen infects the fourth or fifth
instar larvae in which it invades the epithelial
cells of the ovaries and then the parasites are
transferred to the oogonia, oocytes and
nutritive cells.

11. i) Egg stage: The eggs laid by moth are fewer and do not firmly
attach to the egg sheet. ” The number of dead and unfertilized
eggs is higher. ” The hatching is irregular and number of
hatched eggs is fewer.
s to moult. ” The silk gland will have white pustules on its
surface. ” The dead larvae remain rubbery for sometimes and
then turn black.
ii) Larval stage: ” The diseased larvae will have poor appetite,
retarded growth, undersized and flaccid. ” The larvae are
comparatively paler, translucent and delays to moult. ” The silk
gland will have white pustules on its surface. ” The dead larvae
remain rubbery for sometimes and then turn black

14.  When spores of N. bombycis were ingested by
silkworm larvae, the inner part of the spore lost
its affinity and small sporoplasm discharged
from the spores developed into large ovoid
cells with two nuclei and a vacole. The
sporoplasms were observed in the peri trophic
membrane and microvilli of the midgut (Abe,
1978a). Histological observations on silkworm
larvae orally infected in the 2nd instar with N.
bombycis spores revealed that after 24 hour
Nosema cells occurred only in the granulocytes
(Abe, I 978a)

15. Detection and elimination of pebrine disease is essential
for sustenance of cocoon crop from industrial point of
view. The age old detection procedure, the only
reliable and widely accepted technique for
preparation of pebrine free eggs, is the one which
involves examination of mother moth tissue smears
under light microscope. The technique was
developed by Louis Pasteur in 1870 and is still
followed to detect the pebrine spore in the field of
commercial seed production in all silk producing
countries including India. Thereafter, though many
novel techniques were developed to detect pebrine
spore, the popularity of the mother moth examination
has not been dwindled. Due to many practical
reasons, the other detection procedures remained
only as of theoretical interest for the researchers.

16. The fundmental measure in the control of this
disease is production of innocus eggs,which
which would preclude embryonic
infection.inspection of the mother of silkworm
moths,corrective inspection for pebrine ,and
disease prevention and mangement in the egg
producing farms should be carefully
undertaken.strict implementation of the
supervising regulstions should be carried out

17.  Crop loss is a regular feature associated with
Indian sericulture scenario for various reasons. It
may be accounted for different sorts of disease,
parasites, weather conditions or even for cultural
reasons. But none of them is as severe as the larval
mortality owing to pebrine disease where the
entire crop is lost. The causative agent for the
disease is Nosema bombycis Nageli, a spore
forming eukaryotic, obligatory and intracellular
protozoan. Detection and elimination of pebrine
disease is essential for sustenance of cocoon crop
from industrial point of view