Para Lab 1 U 2006

PARASITOLOGY LABORATORY 1 – NEMATODES USTMED ’07 Sec C – AsM; pictures provided by JV.N. Update 2006 – A. Abad

Trichuris trichiura (female)

TRICHURIS TRICHIURA Note the gross features of the typical, unembryonated, fertile egg, ie, the bile-stained, thick, smooth shell with polar prominences, often called polar “plugs.”

ENTEROBIUS VERMICULARIS Enterobius vermicularis (adult male) Adult male worms are much smaller than females and are detected less frequently in feces or on cellulose tape. The oral end lacks a true buccal capsule but is provided with three lips and dorsoventral bladderlike expansion of the cuticula. Note the posterior end strongly curved ventrad. It has a single conspicuous copulatory spicule.

Trichuris trichiura X-section Appendix

(below) Higher magnification of the posterior end of the adult male showing strongly curved ventral end and the conspicuous copulatory spicule.

Trichuris trichiura fertilized ova. Female worms in the human cecum shed 3,000 to 20,000 eggs per day. Embryonation occurs after the egg passes into the environment (requires tropical temperature). On average, an infective egg (embryonated) survives for less than 1 year.

Enterobius vermicularis

T. trichiura in sect. appendix.

Trichuris trichiura This illustration demonstrates the gross features of male and female adult worms. Note that both are whip-like, that the male, in contrast to the female, has a characteristically coiled tail. These worms, though small, are readily seen but rarely found in feces, except following treatment.

Trichuris trichiura (adult male)

Female and male adult worms. The female worms of E. vermicularis (pinworm) is white and measures from 8 to 15 mm in length by approximately 0.4 mm in width. In contrast, the male adult worm is much smaller, measuring 2 to 3 mm in length by 0.1 to 0.2 mm in width. The dilated cephalic region is similar in both sexes, while the tail is pointed in the females (left) and blunted in the males (right). Females are more frequently found in cellophane tape preparations than the males. The cephalic inflation of the cuticle and the muscular and bulbous protions of the esophagus separated by a narrow region can be observed in the right figure.

Enterobius vermicularis ova Clear adhesive tape applied to the perianal area of a child reveals numerous D-shaped Enterobius vermicularis embryonated ova. Scratcing the perianal area leads to hand contamination with infective ova and reinforcement of the houst.

G. Smooth Tape with cotton or guaze.

.G.

Note: Specimens are best obtained a few hours after the person has retired, perhaps at 10p.m, or the first thing in the morning before a bowel movement or bath.

TRICHINELLA SPIRALIS Enterobius vermicularis female

Enterobius vermicularis male

Materials used for scotch tape method for diagnosis of Enterobius vermicularis

a. a.

c.

Cellulose Tape Slide Preparation (End Product)

b. Cellulose-tape slide preparation b. Hold slide against tongue depressor one inch from end and lift long portion of tape from slide

CLASSIFICATION – Nematode DISEASE trichinosis GEOGRAPHIC DISTRIBUTION Cosmopolitan, but more prevalent in Europe and North America than in tropical countries. LOCATION IN HOST Adult worms live in intestinal tract for several weeks to several months. The larval stage, encapsulated in muscle tissue, may live for several years MORPHOLOGY - Adult worms. The adult male is minute, measuring 1.41.6 mm in length by 40-60 u, and has two large, fleshy papillas(?) at the posterior end. Adult females are 2.54.0 mm long by 100-150 u wide. The reproductive tract is filled with developing eggs and larvae. In both sexes, the esophagus (stichosome) consists of a thin, narrow tube surrounded by a column of glandular cells called stichocytes. LARVAE Minute larvae, produced by the adult female, measure 100 u long by 6 u in diameter. Infective larvae in muscle tissue measure 0.8-1.0 mm long. LIFE CYCLE When infective larvae in muscle tissue are ingested, they reach maturity in the intestine in approximately one week. Adult females deposit their minute larvae in the mucosal epithelium. These larvae enter the bloodstream and are carried to the muscle tissue throughout the body. The larvae grow in muscle tissue, become infective in approximately one month,, and are encapsulated by host tissue. All mammals may be infected by this parasite, but pigs and rats are the most important reservoir hosts in nature. DIAGNOSIS usually based on clinical symptoms and history of ingestion of poorly cooked meat, especially pork products. Serologic tests are useful. Although muscle biopsies usually are not performed to detect larvae, the procedure may be used. Diagnosis of animal infections is best established by examination of tissue. Larvae are most abundant in tongue, masseter muscle, diaphragm, and other active muscle tissues. Diagnostic problems – in light infections, symptoms may be vague and trichinosis not considered in a differential diagnosis. In animal infections, a few press preparations of muscle tissue may not be adequate to demonstrate larvae. Thus, artificial digestion of large amounts of muscle tissue may be required. COMMENTS Most infections in the United States now are attributable to eating of poorly cooked or smoked pork products derived from hogs raised on private farms, rather than from processed by commercial meat packing firms. Bear meat has been shown to be infected, and numerous cases of human infection have been traced to this source.

d.

c.Loose tape over end of depressor to expose gummed surface d. Hold tape and slide against tongue depressor Trichinella spiralis encysted larvae

e.

f.

e. Press gummed surfaces against several areas of perianal region f. Replace tape on slide

The larvae produced by adult females migrate via the blood-stream to the musculature where they undergo considerable growth and development, and become encapsulated by host tissue. Larvae may be found in press preparations of skeletal muscle (left) or in hematoxylin-eosin-stained histologic sections of the same tissues. In this stained section (right) of diaphragm, not the presence of four larvae surrounded by the host tissue reaction.

Capillaria philippinensis unembryonated fertile eggs. These small

eggs have striated shells and inconspicuous polar prominences.

Trichinella spiralis Adult

Capillaria philippinensis adult

CAPILLARIA PHILIPPINENSIS Capillaria philippinensis Capillaria philippinensis ova

Stichosome

Egg

Spicule

Spicule sheath

Adult female

Adult male

Capillaria Ova -fin-