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22 Cards in this Set

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Trichinellida Trichuridae
- classification
Nematodes Order Trichinellida
Trichuridae :
Trichuris trichuria
Trichinella spiralis
Trichinellida Trichuridae
-
Family Trichuridae
Whipworms Trichuridae ( Gr. trichos = a hair + oura = the tail).
Thread-like body, becomes thick at the posterior end (looks like whip).
There are many species in a wide variety of mammalian hosts,
In humans: Trichuris trichiura
Eggs of Trichuris trichiura have been found in a glacier mummy more than 5000 years old
Morphology.
measures 30 mm to 50 mm long,
males smaller than females.
The buccal cavity is tiny followed by a very long esophagus, occupying about two- thirds of the body length, surrounded by large, unicellular glands, or stichocytes. The entire structure often is referred to as a stichosome.
Both sexes have a single gonad, and the anus is near the tip of the tail.
Males have a single spicule that is surrounded by a spiny spicule sheath. The ejaculatory duct joins the intes-tine anterior to the cloaca.
In females the vulva is near the junction of esophagus and intestine.
The uterus contains many unembryonated, lemon- shaped eggs, each with a prominent opercular plug at each end .
An excretory system is absent. The ventral surface of the esophageal region bears a wide band of minute pores, leading to underlying glandular and nonglandular cells. This bacillary band is typical of the order, may have a role in osmotic or ion regulation, and the nongland cells may function in cuticle formation and food storage.
Trichinellida Trichuridae
- Male Trichuris sp.
Note the slender anterior end and the stout posterior end with a single, terminal spicule.
Trichinellida Trichuridae - male
Male Trichuris sp. Note the slender anterior end and the stout posterior end with a single, terminal spicule.
Trichinellida Trichuridae - Biological and distributional characteristics of Trichinellida spp
Trichinellida Trichuridae - life cycle
The unembryonated eggs are passed with the stool . In the soil, the eggs develop into a 2-cell stage , an advanced cleavage stage , and then they embryonate ; eggs become infective in 15 to 30 days. After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae that mature and establish themselves as adults in the colon . The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. The females begin to oviposit 60 to 70 days after infection. Female worms in the cecum shed between 3,000 and 20,000 eggs per day. The life span of the adults is about 1 year.
Trichinellida Trichuridae - Pathology
Fewer than 100 worms rarely cause clinical symptoms, and the majority of infections are symptomless.
200 to more than 1000 worms. Cause symptoms in children mainly occasionally terminating in death.,
Symtpoms
dysentery, anemia, and growth retardation are very common, and finger clubbing and rectal prolapse ( Fig). are fre-quent.
With their anterior ends buried in mucosa, worms feed on cell contents and blood, although blood loss by this mechanism is negligible.
Trauma to intestinal epithelium, can cause a chronic hemorrhage that results in anemia due
to host inflammatory response, and increase in macrophages in the colonic lamina propria and increased TNF concentration both in the mucosa and systemic circulation.
There is an increase in degranulating mast cells and a 10- fold increase in the proportion of lamina propria cells with surface IgE. This and other evidence suggests that inflammation in Trichuris colitis may be considered a local tissue anaphylactic response.
Trichinellida Trichuridae - identify this symptom
Prolapse of rectum caused by whipworm infection.
Trichinellida Trichuridae - Diagnosis and Treatment
:Specific diagnosis
worm or eggs in the stool. have smooth outer shells with distinctive bipolar plugs.
Clinical symptoms may be confused with those of hookworm, amebiasis, or acute appendicitis.
Worms can be demonstrated dramatically by colonoscopy.

Treatment
Because of their frequent location in the cecum, appendix, or lower ileum, whipworms are difficult to reach with oral drugs or medicated enemas.
Mebendazole and albendazole are effective drugs. 13

Prevention
Training of children and adults in sanitary disposal of feces and in washing of hands is necessary to prevent reinfection.
Egg of Trichuris trichiura. It measures 50 µm to 54 µm by 22 µm to 23 µm.
Trichinelliida biology/lifecycle image
Biology:
Each female worm produces from 3000 to 20,000 eggs per day
Embryonation is completed in about 21 days in soil, which must be moist and shady.
When swallowed, infective juveniles hatch and enter the crypts of Lieberkühn.
After penetration of cells in the base of the crypts, worms begin to .grow .
They can penetrate the gut mucosa in many places,
At maturity, the enlarging posterior portion of worms breaks out of the epithelium and protrudes into the intestinal lumen. The process requires about three months. The slender anterior ends re-main embedded in the gut mucosa, and the worms essentially are tissue parasites.
Adults live for several years, so large numbers may accumulate in a person, even in areas in which the rate of new infection is low.
Trichinellida trichuridae - trichuris trichuria in large intestine
Section of large intestine with sections of Trichuris trichiura embedded in the mucosa. Individual stichocytes are evident.
Trichinellida Trichuridae - Trichinella spp, eg Trichinella spiralis
the smallest nematode parasite of humans, one of the most wide-spread and clinically important parasites in the world.

These parasites are responsible for the disease variously known as trichinosis, trichiniasis, or trichinelliasis.
It is common in carnivorous mammals, including rodents and humans, primarily .
Trichinella spp. are less common in tropical regions but are well known in Mexico, parts of South America, Africa, southern Asia, and the Middle East.

Morphology.
Males measure 1.4 mm to 1.6 mm long and are more slender anteriorly than posteri-orly. The anus is nearly terminal and has a large copula-tory pseudobursa on each side of it ( Fig. 23.9). There is no copulatory spicule. As in other members of order Trichinellida, stichocytes are arranged in a row following a short muscular esophagus. Females are about twice the size of males and also taper anteriorly. The anus is nearly terminal. The vulva is near the middle of the esophagus, which is about a third the length of the body from the an-terior end. The single uterus is filled with developing eggs in its posterior portion, whereas the anterior portion con-tains fully developed, hatching juveniles.
Trichinellida Trichuridae - Trichinosis disease - lifecycle
Trichinosis is a disease caused by eating undercooked meat, pork, which contains cysts of Trichinella spiralis occurs also bear, fox, rat, horse, and lion meat.

. When a person eats meat from an infected animal, Trichinella cysts break open in the intestines and grow into adult roundworms. The roundworms produce other worms that move through the gut wall and into the bloodstream. These organisms tend to invade muscle tissues, including the heart and diaphragm (the breathing muscle under the lungs). They can also affect the lungs and brain. There are approximately 40 cases of trichinosis each year in the United States.
Male Trichinella spiralis ( 1.4 mm to 1.6 mm in length) from the intestine of a rat.
Scanning electron micrograph of male Trichinella nativa. Note the posterior end including copulatory pseudobursae and papillae.
Trichinellida Trichuridae: Biology/lifecycle
same individual animal serves as both definitive and intermediate host, with juveniles and adults located in different organs.
largest intracellular parasite! Adults are intramulticellular parasites in intestinal epithelium,
juveniles reside in nurse cells, generated by juveniles in , in skeletal muscle.

When infective juveniles are swallowed and reach the stomach of the host, they are released from their nurse cells and become “ activated”:
In host’s small intestine, they undergo four molts and growth, and copulation occurs within the mucosal epithelium within 30 to 32 hours of infection
The worms lie directly in the cytoplasm and thread through a serial row of intestinal cells females produce hundreds and thousands of juve-niles over a period of 4 to 16 weeks. Eventually a spent female dies and passes out of the host.
Males can copulate several times but then die shortly after.
Most juveniles are carried away by the hepatoportal system through the liver and then to the heart, lungs, and arterial system, which distributes them throughout the throughout the body.
When they reach skeletal muscle, they penetrate individual fibers. They alter gene expression of the host cell from that of a contractile fiber to that of a nurse cell, a cell that functions in nourishing the worm.
After the nematode enters it, the fiber loses its myofilaments, the entire unit becomes encapsulated with collagen secreted by the nurse cell.
Trichinellida Trichuridae
Conceptual illustration of an adult T. spiralis threading its way through the intestinal epithelium. ( Scale bar = 400 µm.)
Trichinellida Trichuridae
Schematic drawing of an intact nurse cell- parasite complex, showing the surrounding circulatory cappillaries
Trichinellida Trichuridae
Juvenile of Trichinella spiralis in a muscle nurse cell, the nurse cell- parasite complex.
The outer layer is collagen capsule ( C).
Note several hypertro-phied nuclei ( N, arrows).

( Scale bar = 100 µm)
Trichinellida Trichuridae - Pathogenosis
penetration of adult females into the mucosa, migration of juveniles, and penetration and nurse cell formation.
12 hours and two days after ingestion of infected meat. (may be asymptomatic)
First symptoms appear when worms migrate in intestinal epithelium, cause traumatic damage to host tissues;
Inflammation ,nausea, vomiting, sweating, and diarrhea.
During migration newborn juveniles damage blood vessels, resulting in localized edema, facial edema and red blotches erupt on the skin particularly in the face and hands. and fever five to seven days after the first symptoms.
Wandering juveniles may also cause pneumonia, pleurisy, encephalitis, meningitis, nephritis, deafness, peritonitis, brain or eye damage, and subcon-junctival or sublingual hemorrhage. Death resulting from myocarditis ( inflammation of heart muscle) may occur at this stage. Although juveniles do not stay in the heart, they migrate through its muscle, causing local areas of necrosis and infiltration of leukocytes.
By the 10th day after appearance of first symptoms, juveniles begin penetration of muscle fibers. Causes intense muscular pain, difficulty in breathing or swallowing, swelling of masseter muscles ( occasionally leading to a misdiagnosis of mumps), weakening of pulse and blood pressure, heart damage, and various nervous disorders, including halluci-nation.
Heavy infection
Death is usually caused by heart failure, respiratory complications, or kidney malfunction.
Trichinellida Trichuridae - Diagnosis and Treatment
. Most cases of trichinosis, par-ticularly subclinical cases, go undetected.
Routine examinations rarely detect juveniles in feces, blood, milk, or other secretions. Although
muscle biopsy (under microscope) is seldom employed, it remains an accurate diagnostic if trichinosis is suspected.
immunodiagnostic tests are available

No really satisfactory treatment for trichinosis is known.
Treatment is basically that of relieving the symptoms by use of analgesics and corticosteroids. Purges during the initial symptoms may dislodge females that have not yet begun penetrating intestinal epithelium.
Thiabendazole has been shown effective in experimental animals, but results in clinical cases have been variable. Despite immense research, trichinosis remains an important disease of humans