Adult tapeworm in formalin: Introduction and Its Details

Adult Tapeworm in Formalin: Introduction and Its Details

Tapeworm in Formalin

The above picture is showing adult tapeworm in formalin having scolex, neck, and proglottids. Formalin is a colorless solution of formaldehyde in water, used chiefly as a preservative for biological specimens and therefore for Taenia species (tapeworm). Tapeworm is segmented, dorsoventrally compressed, and tape-like, therefore called tapeworm. It varies from a few millimeters to several meters in length. Adult cestode or tapeworm lives attached to the mucosa in the small intestine and absorbs food from the host intestine.

Scientific Classification of tapeworm

Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestoda
Order: Cyclophyllidea
Family: Taeniidae
Genus: Taenia
Spceis: T. saginata
T. saginata

***Taenia saginata* and *Taenia solium***

Taenia saginata: the beef tapeworm, the unarmed tapeworm.
Taenia solium: the pork tapeworm: the armed tapeworm of man.
T. saginata has a worldwide distribution in countries where cattle are raised and beef is eaten.
T. solium is not as widely distributed as T. saginata. It occurs mainly in Southern Africa, China, India, Central America, etc.

Habitat

Adult worms of both T. saginata and T. solium live in the small intestine (upper jejunum) of man.

Morphology of Taenia saginata

Adult worm
The adult worms consist of the scolex (head), neck, and strobila which is made of a large number of proglottids (segments).

White and semitransparent
Mesures up to 10 meters
Life span-10 years
Morphology of proglottids (segments)
1000 to 2000 in number
2 cm long 0.5 cm wide
Genital pore
Marginal
Posterior of segment
Alternate right and left irregularity

Egg

They are spherical, brown in color (bile stained) and measure 30-40 µm in diameter.
They are surrounded by embryophore which is brown, thick-walled, and radially striated.
Inside embryophore, the hexacanth embryo (oncosphere) presents three pairs of hooklets.
It does not float in a saturated solution of common salt (brine solution).
It is viable for 8 weeks.

Morphology of Taenia solium

Adult worm

Life span: 25 years

2-3 meters in length

The adult worm contains three parts and they are-

Scolex

Neck: 0.5 mm
Proglottids
The genital pore is marginal
Middle of the lateral margin of segments (alternating right and left)

Egg

30-40 µm
Spherical and brown in color
Thin outer transparent shell
Inner embryophore- brown radially striated
It contains an oncosphere with 3 pairs of hooklets.
It does not float in saturated saline solution.
Eggs are viable for up to 8 weeks.

Gravid segment

Size:12 mm ×6 mm
The longitudinal stem of the uterus with 5 to 10 lateral branches
Gravid segments are discharged passively in chains of 5 to 6 at a time

Cysticercus cellulosae (bladder worm)

Ovoid, opalescent ( 5 mm× 10 mm)
White vesicle
Covered by capsule and contain thick fluid 9 protein and salt)
The scolex of the larvae invaginated in the bladder
It is viable for many months.
It develops in men and pigs.
It becomes an adult worm in 5 to 12 weeks.

Life cycle of Taenia species

The T. saginata passes its life cycle in two hosts. A definitive host is a man who harbors the adult worm. The intermediate host is cattle. Eggs or gravid segments are passed out with the feces on the ground. These are ingested by cows or buffaloes.

Clinical features of Taenia saginata

Adult worms in the small intestine usually produce no symptoms. But at times, they may cause abdominal discomfort, indigestion, persistent diarrhea or diarrhea alternating with constipation and loss of appetite, intestinal obstruction, and even acute appendicitis.

Clinical features of Taenia solium

Vague abdominal discomfort
Indigestion
Alternating diarrhea and constipation
Anemia

Cysticercus cellulose infection

Ingestion of eggs in water or vegetables

autoinfection

Solitary or multiple

Commonly subcutaneous and muscles

Any other organs may be involved

Eyes

Blurring vision

Uveitis

Iritis

Loss of vision

Brain

Epilepsy

Behavioral disorder

Paresis

Hydrocephalus

Less often organs are-

Heat

Liver

Lung

Abdominal cavity

Spinal cord

Brain

Cysticercus cellulosae is surrounded by fibrous capsules except for eye and brain ventricles

Evokes cellular response

Pathogenicity

Cysticercosis is a disease caused by the larval stage of T. solium, an important public health problem in tropical countries. Occasionally obstructive appendicitis or cholangitis occurs in Taenia infections due to aberrant migration of segments, which have been found also in the uterine cavity. In rare cases, proglottids may obstruct the respiratory tract, enter the middle ear through the eustachian tube or localize in adenoid tissue of the nasopharynx. They usually develop in the subcutaneous tissues and muscles forming visible nodules. It may develop in the brain.

Laboratory diagnosis

Specimens: Stool, a biopsy of subcutaneous nodules, blood, serum

Direct method

Demonstration of egg and gravid segments.

By microscopy method; Saline wet mount: Saline wet mount is made by mixing a small quantity (about 2 mg of feces) in a drop of saline placed on a clean glass slide. Remove any gross fibers or particles and cover with a cover slip. The smear is then examined under a microscope.

Concentration methods: Formalin-ether sedimentation; for species diagnosis- head and gravid segments are required. It can’t be differentiated morphologically.

Anal swab: Anal swabs are superior to the methods using for detecting eggs from feces.

The diagnosis of cysticercosis can be carried out using biopsy of the subcutaneous nodule, it may reveal Cysticercus cellulosa.

Indirect method

X-ray of skull and soft tissue to reveal calcified cysticerci. MRI for non-calcified cyst

Blood cell count: eosinophilia

Serological test for detection of specific antibodies by using serum, CSF, IHA
(indirect hemagglutination) , IFA (Indirect fluorescent antibody) and ELISA.

Treatment

Praziquantel and niclosamide can be used for the treatment of human tapeworm infection. Other drugs are-

Quinacrine
Bithionol
Mebendazole

for cysticercosis

surgical excision
Praziquantel
Metrifonate

**Prophylaxis of T. saginata infection**

All beef to be eaten by man should be inspected for cysticerci. Through cooking of beef ensures complete protection.

Proper sanitary disposal of feces.

Cattle should not be allowed to feed or graze on the ground polluted by human feces or sewage. This will control cattle infection.

**Prophylaxis of T. solium infection**

Personal hygiene
General sanitary measures
Avoid food and water contamination with T. solium eggs.
A strict veterinary inspection of pork in all slaughter houses with condemnation of infected pigs. Thorough cooking of pork ensures complete protection.

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