cestodes- diphyllobothrium and ligula spp.

1. Endoparasite of fish:Cestode

2. INTRODUCTION
• Cestodes are endoparasitic tapeworms.
• They are parasitic in the intestine of the host Larval cestodes are commonly found
in fish, often encysted amongst the viscera and musculature.
• CAUSATIVE AGENT:
1. Asian tapeworm-Bothriocephalus acheilognathi
2. Ligula intestinalis

3. AETIOLOGY
• Body is ribbon-like, segmented or unsegmented, 5-70
mm long The cestodes are also endoparasitic with at
least one intermediate host in their life cycle. Usually
the body (strobila) is subdivided into a number of
segments (proglottids) each containing a single set of
reproductive organs

4. • A scolex (attachment organ) is present at the anterior end. The adult worms are
usually white in colour and may be very elongated The scolex of these larvae is fully
developed, but the strobila is usually relatively short and unsegmented..
• All cestodes are oviparous and the eggs passed in the faeces of the final host may or
may not hatch in water to release a free-swimming larva coracidium.

5. LIFE CYCLE
• The cestodes of fish have a life cycle involving at least one other host. Fish may
serve as final or inter-mediate hosts for cestodes.
• Whether ingested as larvae coracidium or egg the larval cestode penetrates through
the gut wall of the host and undergoes further development in the body cavity to a
stage capable of infecting the fish host. In most orders of cestodes, this stage is
known as a procercoid.
• If the procercoid is ingested by a suitable fish host, it penetrates through the gut
wall and encysts in the viscera or musculature where it develops to the plerocercoid
stage.
• . The life cycle of this group of cestodes is completed if an infected fish is eaten by a
suitable final host. This may be another fish, a bird or a mammal, in the gut of
which the cestode develops to maturity

6. Life cycle of cestodes

7. HOST RANGE
1. Minnows
2. Golden shiner
3. Various carp species (cyprinidae)
4. Poecilidae.
5. Centrachidae
6. Channel catfish
7. Aquarium fish, such as discus and other cichlids

8. TRANSMISSION
• Many piscivorous birds or mammals can act as a final host for cestodes
• Development ceases at 12 ° C. Worms mature in about 21 days at 28 ° C in 2 months
• at 15 ° C.
• The plerocercoids are transmitted by copepods. Several copepod genera can be
intermediate hosts and the distribution of infections depends largely on the
abundance of the intermediate host

9. EXTERNAL PATHOLOGY
1. Affected fish are sluggish.
2. Emaciated body because of non-feeding
3. Gut blockage
4. Abdomen
5. Chronic mortality.

10. INTERNAL PATHOLOGY
• This parasite is commonly found in intestine of
fish.
• Migrating plerocercoids may cause adhesions
and severely damage viscera or muscle because
of pressure necrosis. Ligula causes peritoneal
adhesions and pressure atrophy of the liver,
gonads, and body wall musculature of cyprinids
worldwide.
Ligula intestinalis in a cyprinid. The body wall has been
cut, revealing the peritoneal cavity filled with a single
plerocercoid ( P ). Part of the worm remains in the
peritoneal cavity.

11. DIAGNOSIS:
• Gross examination of the intestine of host
fish.
• Worms are easily identified as cestodes
from wetmounts or histopathology.
• From wet mounts of fecal contents having
proglottids or eggs can be detected.
Histological section through a cestode ( C ),
Bothriocephalus acheilognathi , filling the lumen of the
intestine ( I ) of a minnow. Giemsa stain.

12. PATHOGENESIS
• The parasite may induce hemorrhagic
enteritis due to destruction of the intestinal
epithelium & eggs are found in intestine
and peritoneal cavity grossly.
• Adult stage of the parasite interferes with
absorptive processes of the intestine and
may reduce food intake.
• Secondary microbial infection is possible.
Some fish cestodes are important human
parasites.

14. PREVENTION AND CONTROL
• Elimination of intermediate hosts (copepod)
• Disinfection of culture facilities with quick lime to destroy cestode eggs
• Praziquantel 300 mg/kg feed orally for every 4th day for 1month is effective in
treating adult cestode infections.
• Aquarium fish should not be fed live foods that might transmit larval cestodes.
• In farms using surface water, filtering the water to exclude the intermediate host
can prevent infections

15. Thank you..