PARASITOLOGY LECTURE 2 – Nematodes – Dr. NgNotes from LectureUSTMED ’07 Sec C – AsM

TRICHURIS TRICHIURIA

also called as whipworm

incidence of occurrence, same as Ascaris

2nd common intestinal worm aside from Ascaris

usually occur in moist, warm, tropical region of Asia, Central and South America, Africa and the Caribbean Islands

MORPHOLOGY:

ADULT WORMo Color: Flesh or pinkish colored slender

wormso Size:

1. Female – 3.5 to 5.5 cm2. Male = 3.0 to 3.5 cmMale is smaller than female3. Anterior 3/5 o f the worm – fine

hair-like structure which forms the esophagus

Esophagus – is characteristically embedded in glandular cells called stichocytes4. Posterior 2/5 of the worm

contain the intestine and reproductive organs

Tail end:Female – straight and bluntMale – usually curved at 360o

EGGo Shape

- Barrel-shaped egg

- thick, smooth brown egg shell and 2 transparent plugs protruding from both poles

o Size – measures 50 to 54 microns by 22 to 23 microns

1. Fertilized egg

2. Embryonated egg

LIFE CYCLE OF TRICHURIS TRICHIURIA

Note:

There is no migration phase in the lungs, heart or liver

It require about 2-3 months from the time the eggs are swallowed until they are seen in the stool of infected person

Each female whipworm can produce 7,000 to 10,000 eggs per day or a total of over 60 million eggs by single whipworm over an average life span of 2 years

PATHOLOGY AND CLINICAL MANIFESTATION

A. Light infection with trichiuris are asymptomatic and without clinical significance

After copulation in the cecum

Female worms start to lay eggs w/c are passed out with feces and deposited in the stool in

With favorable environmental condition, in 2-3 weeks they develop into their infective stage with larval

stage w/in the egg (embryonation).

Whipworms inhabit the large intestine where the entire whiplike portion is deeply inserted into the wall

of large intestine. Because of this mode of attachment, it is much harder to expel whipworm than

ascaris by anti helmintics

Once the infective embryonated egg is swallowed by the host, they hatch in the intestine to release the larva and this larva undergoes 4 larval stages to become adult worm.

B. Symptoms produced by trichiuris are due to worms unique mode of attachment on the wall of the large intestine where it got its nutrition

- therefore, the degree of clinical symptoms is related to the intensity of the infection.

CLINICAL MANIFESTATION1. Diarrhea due to chronic

Hypoalbuminemia impairment of host’sIron Deficiency Anemia nutritional status

2. Anemia- due to ulceration of the intestine

resulting from heavy worm burden- Anemia is less frequent than

hookworm]

3. Prolapse of the anus and the rectum- due to frequent loose bowel

movement resulting to the loss of muscle tone of the anal sphincter

- could also resort to bleeding thus aggravates the anemia

4. Appendicitis- due to invasion of trichiuris

DIAGNOSIS:

1. Direct Fecal Smear (DFS)2. Cellophane thick smear method or the Kato thick

smearEPIDEMIOLOGY

In the Philippines- prevalence of trichiuris is 80-90% almost parallel

with Ascaris- Most infections are light to moderate and seldom

produce clinical symptoms- Trichiuris eggs are less resistant to adverse

reaction than Ascaris eggs

TREATMENT

A. Albendazole- Dose – 400 mgs single dose

B. Mebendazole- Dose – 500 mgs single dose or 100 mgs twice

a day for 3 daysC. Oxantel-Pyrantel

- Dose – 10-20 mgs per kg/body weight single dose

CAPILLARIA PHILIPPINENSIS

intestinal capillariasis is a disease characterized by:1. intestinal malabsortion2. chronic diarrhea3. Borborygmi

first recognized in the Philippines in 1963 where the first human case died in PGH

Origin: Bacarra Ilocos Norte Order Trichurida Prevalence

1. Philippines- Ilocos Norte- Ilocos Sur- Cagayan- La Union- Pangasinan- Zambales- Agusan del Norte- Leyte

2. Thailand3. Japan4. Iran5. Egypt6. Taiwan

MORPHOLOGY:

ADULT WORMo Small worm

1. Female worm size: 2.3 to 5.3 mm by

length larger than male

2. Male worm size: 1.5 to 3.9 mm by

length smaller than female characterized by the

presence of a chitinized spicule and a long spicule sheath extending beyond the length of worm

2 Types of Female worms

a. Typical female – which has 8-10 eggs in utero arranged in a single row

b. Atypical female – which has 40-45 eggs in utero arranged in 2 to 3 rows

CAPILLARIA EGGSo Color : pale yellow in color with a

moderately thick, striated shell with flattened bipolar plugs

o Shape: Peanut-shapedo Size:: Measures 42 by 20 umo Development stage – single or 2

segmented stage development

LIFE CYCLE OF CAPILLARIA PHILIPPINENSIS

PATHOLOGY AND CLNICAL MANIFESTATIONS

A. Disease is characterized by:1. Borborygmi or gurgling stomach2. Abdominal pain3. Diarrhea

Adult worms inhabit primarily in the jejunum and are threaded into the mucosa (Larvae and eggs are

produced by typical and atypical female worms)

Eggs passed out in the feces embryonate in the fresh water in 3 to 5 days

Upon ingestion by fresh water fish, hatch in the intestine of fish. Larvae are found mostly in the

gastric mucosa and Intestines

When infected fish is ingested the worm’s mature in the host’s small intestine

In 2 weeks, atypical females start producing larvae then grow into mature adult worms

B. Without Treatment the patient may experience1. Weight loss2. Dehydration3. Malaise4. Anorexia5. Vomiting6. Anasarca7. Muscle wasting8. Cachexia

C. Other Manifestations1. Malabsorption of fats and sugar2. Protein-losing enteropathy3. Low level of K, Ca++, Carotene4. Low plasma level of total protein

D. Death is attributed to massive parasitic infection resulting to:1. Electrolyte loss2. Heart failure3. Septicemia secondary to bacterial infection

PATHOLOGIC CHANGESa. Atrophy of the crypts of Liberkuhnb. Flattened villi with lamina propia infiltrated

by plasma cells, lymphocytes and macrophages

DIAGNOSIS:

by finding characteristico eggso larvaeo adult worms in stool

eggs can readily be seen in a simple fecal smearo concentration technique acid ether or

formalin ether method

EPIDEMIOLOGY:

- first recognized in 1963- 1,800 confirmed cases w/ 108 deaths- male is affected twice than females- Peak age: 20-49 years old

TREATMENT:

A. Mebendazole- Dose: 200 mgs twice daily for 20 days

B. Albendazole- Dose: 400 mgs daily for 60 days

PREVENTION AND CONTROL:

changing the eating habits from raw uncooked fresh water fish9 to cooked fish

TRICHINELLA SPIRALIS

diseases:a. Trichinosisb. Trichiniasisc.Trichinelliasis

MORPHOLOGY

ADULT WORMo Small wormo Size

1. Male – 1.50 mm by 0.04 mm2. Female – 3.50 mm by 0.50 by

0.06 mmo Shape

- thread-like appearanceo characteristics

1. Anterior endo provided w/ a small

orbicular, non-papillated mouth

o in female, Anterior fifth is provided w/ a single ovary with vulva and a long narrow digestive system

2. Posterior endo Female: bluntly roundedo Male: ventrally curved with

2 lobular appendages

LARVAEo Has a spear-like burrowing tip at its

tapering anterior endo Measures 80-120 h by 5.6 u at birtho Matured encysted larvae have digestive

tracts although the reproductive are not fully developed.

DIAGNOSIS

Clinical Diagnosiso History of eating raw or inadequetly

cooked or improperly processed meat usually pork

o History of intestinal flu or rheumatic paino Marked eosinophilia in bloodo Swollen eyelids or severe conjunctivitis

Specific Diagnosiso Biopsy - free larvae or encapsulated

larvae in skeletal muscleo Xenodiagnosiso Bachman Intradermal test

TREATMENT

No established specific treatmentA. Thiabendazole

- Dose: 50 mg/kg/body weight- Effect:

- may prevent the appearance of symptoms if given from the second day after ingestion of infected meat

- greatly mitigate the illness if drug is given between the fifth and ninth day after ingestion

B. ACTH or corticosteroid- treatment of allergic reaction

C. Mebendazole- lethal effect

LIFE CYCLE OF TRICHINELLA SPIRALIS

PATHOGENESIS

Pathologic changes and the symptomatology are divided into 3 stages:

1. incubation or intestinal phase

2. acute or larval invasion3. chronic or encapsulated

1. Intestinal Phase- Inflammation of duodenal and jejunal mucosa:

a. Malaiseb. Nauseac. Diarrhead. Abdominal cramps

2. Stage of Muscle Invasiona. Feverb. Facial edemac. Muscle pain, swelling and weaknessd. Peripheral eosinophilia

Less common symptoms:a. headacheb. Flushing of facec. Conjunctivitisd. Prurituse. Diaphoresisf. Anorexiag. Thirst

Damage of muscle may cause difficulty in:a. Eye movementb. Breathingc. Chewingd. Swallowinge. Speechf. Movement of extremities

Myocarditis – appear as early as the second week but more ofteh after the third week.

- Death from myocarditis usually occurs between the fourth and eight weeks of infection.

- Encephalitis and meningitis may also occur at this stage

3. Stages of Convalescence- end of the 3rd week of infection

where encapsulation start to be seen

SYMPTOMS

1. Fever subsided2. Muscular symptoms begin to decline3. If there is marked edemaàdiuresis may occur4. Appetite return to normal5. Malaise subsided

- myocarditis may still be present at this stage and physical exertion may precipitate congestive heart failure

- venous thrombosis and encephalitis- eventually- when all symptoms subsided, the cyst

wall and larva itself calcify

Biological Stage Beginning/Onset

Clinical Conditions

Ingested larvae exist in epithelium

2-4 hrs24

GI symptoms

Worms become mature and mate

30

Females deposit larvae, which invade skeletal muscles

6 days

7 Edema of face and fever

Maximum invasion of muscle fibers

10 Fever at max (40-41oC)

11 Myositis and “rheumatic” pains

Decrease in larviposting

14 Eosinophilia and circulating antibody

Larvae in muscles fully differentiated

17

20 Eosinophilia reaches maximum

Early encapsulation 21 Myocarditis or encephalitis

appearIntestine practically free of adults

23

26 Respiratory symptoms

Encapsulation practically complete

1 Month

2 Fever subsidesMaximum life of worms in intestine

3 Death from myocarditis or

encephalitis most likely

Cyst calcification may begin

6 Slow convalescence

8 Neurological symptoms and

myocarditis subside

Cyst calcification may be complete

1 year

Larvae possibly still viable w/in calcified capsules

6

PREVENTION

smoking, drying and slating of meat are not effective measures

A. Refrigeration at 5°F (-15°C) for not less than 20 days- at –10°F (for 10 days)- at -20°F for 6 days- Deep freezing

B. Avoid feeding raw garbage to hogsC. Extermination of rats around the farmsD. Thorough cooking or deep freezing of all pork

ENTEROBIUS VERMICUALRIS

Seatworm or pinworm affecting 208 million population Habitat

o Cecumo Appendixo adjacent portion of ascending colono ileum

MORPHOLOGY

ADULT WORMSo Color: whitish or brownisho Shape: spindle-shapedo Size: very small

1. Female: measures 8-13 mm by 0.3 to 0.5 mm

2. Male: 2 to 5 mm by 0.1 to 0.2 mm

o Posterior end1. Female: long sharp pointed end2. Male: ventrally curved; has a

single conspicuous copulatory spicule but lack gubernaculums

o Anterior End- is a pair of lateral cuticular

expansions known as “lateral wings or cephalic alae”

- Another feature of pinworm adult is the presence of posterior esophageal bulb

EGGSo Size: 50-60 um by 20 to 30 umo Shape: elongated, ovoid flattened on

ventral side giving a letter D appearanceo Egg shell composed of 2 layers

1. An outer thick hyaline albuminous shell

2. Inner embryonic lipoidal membrane

LIFE CYCLE OF ENTEROBIUS VERMICULARIS

PATHOGENESIS AND CLINICAL MANIFESTIONS

Pathogenesis in enterobiasis take 3 forms1. Pathology at the site of attachment of the

worm2. Pathology due to egg deposition in perianal

region3. Pathology caused by migrating worms

A. At the site of attachment- minute ulceration and abscesses develop in

cecal mucosaB. Egg Laying

- intense itching or pruritus in the perianal region resulting to scratching the area until it is scarified

- can also result to hemorrhages, eczema and bacterial infection

C. Migrating worm may go beyond the perianal region and may cause

1. Vulvovaginitis 2. Salphingitis

DIAGNOSIS

Pinworm infection may be suspected in patient exhibiting manifestation like pruritus of the perianal area, restlessness

Use of Perianal cellulose tape swab or Scotch tape swab

o recovery of D shaped embryonated egg Since oviposition take place at night the best time

to take the swab right after the patient awakens or before taking a bath.

EPIDEMIOLOGY

Prevalence among regions varies from 10% in rural area to 75% in crowded urban area

women are infected more than men children are infected more than adult infection may occur thru

1. Hand to mouth transmission from scratching the perianal region or from handling contaminated objects

2. Inhalation of airborne egg in dust3. Reinfection through the anus

The most common mode of transmission hand to mouth transmission

Retroinfection, the eggs hatch in the perianal region and the larvae migrate back into intestines

TREATMENT

A. Mebendazole- single dose of 100 mg tab for everyone above

2 years of age -à this is repeated after 2 weeks

B. Pyrantel pamoate- Dose:

o 11 mg/kg orally (maximum of 1 g) as a single dose

o a second dose should be given after 2 weeks

PREVENTION

1. Personal hygiene2. Finger nail should be cut short. 3. Handwashing after using the toilet or before meal.4. Bed linens and clothing of infected person should

be sterilized by boiling.

-fin-

audsmartinez@gmail.comustmedc3@yahoogroups.com

Adult worms inhabit the cecum where the head attached to the intestinal wall

In gravid female, the uteri packed with eggs and the body becomes distended which makes the female releases its hold on the Intestinal wall and migrate

down the colon andout the anus to lay eggs on the perianal and perineal

Eggs laid on the perianal region become fully matured or embryonated within 6 hours

When ingested, eggs containing the third stage juvenile larva hatch in the duodenum, pass down the small intestines to the cecum and develop into egg laying worm