Order Oxyurida Enterobius vermicularis Pinworms Enterobiasis Large esophageal

Order Oxyurida • Enterobius vermicularis – Pinworms – Enterobiasis • • • Large esophageal bulb Sharp, pointed tail Alae at anterior end Cosmopolitan Common in people Relatively unpathological

• Direct life cycle • Adults live in ileocecal region of intestine (wander throughout gut) • Feed on bacteria and organic material from cells • At night, females migrate to anus and lay eggs (up to 16, 000 each) • Embryonates within 6 hours • Infection via ingestion of embryonated eggs • Or may hatch on perianal folds and wander up intestine

Symptoms and Pathology • 1/3 asymptomatic • Pruritus • Lesions from feeding not significant – Secondary infections can occur • Itching can lead to secondary infections

Pinworm Neurosis • Nervousness – Fidgeting, restlessness, irritable, nail biting, nose picking – Due to toxemia and damage of epithelium • Children • Parents – Obsessive cleaning

Diagnosis • Scotch tape test • Flashlight test • Mebendazole • Treat entire family

Diagnosis of Enterobius vermicularis DIAGNOSIS Use of double-stick tape on a tongue depresser. This is pressed against the perianal folds where eggs will stick to the tape. Tape is then stuck onto a microscope slide and examined for eggs.

Enterobius vermicularis Almost anybody can become infected with this parasite. No social class is exempt. These parasites soon become "family affairs". Once one person, usually a child becomes infected, other family members will undoubtedly also become infected.

Epidemiology • Very Prolific • Eggs build up fast – Clothing and bedding – Eggs very light and float – Easily distributed • Eggs viable for up to a week

Prevention and Control • Not very serious • Good hygiene

Order Trichiurida

Order Trichiurida • Trichuris trichiura – Whipworm • Trichinella spiralis

Trichuris trichiura • 30 -50 mm • Long esophagus surrounded by stichocytes (glands) – Stichosome • Single gonad • Males have single spicule • Eggs have characteristic shape 50 -54 X 22 -23 μm

• Direct Life Cycle • Adults live in cecum and ascending colon • Release eggs with feces • Eggs embryonate in soil (21 days) • Eggs ingested • Hatch • Juveniles enter crypts of Lieberkühn

Crypts of Lieberkühn Tubular glands at base of villi

• Juveniles enter crypts of Lieberkühn (large intestine) • Penetrate cells • As they grow, tunnel in epithelium. Posterior end enters lumen • Mating • Egg production

Symptoms and Pathology • Most symptom-less • > 100 worms – Heavy infections common (200 to over 1000 worms) • • • Dysentery Anemia Growth retardation Finger clubbing Reduce cognitive function in children

Trichuris trichiura • Worms cause loss of muscle tone in wall of rectum and it everts out the anus; whipworms are often seen attached to the rectal tissue

Trichuris trichiura • Rectal prolapse

Symptoms and Pathology • Anterior end buried in mucosa – Physical damage – Fibrosis – Chronic hemorrhage anemia

Diagnosis • • • Look for eggs in feces Adult worms Frank blood in feces Treatment difficult Mebendazole

Epidemiology • Cosmopolitan • Prevalence – SE U. S. 20 -25% in children – U. S. 1. 2% • 902 million infected worldwide

Prolific • Females produce 3, 000 -20, 000 eggs per day • Sensitive to environmental conditions – High rainfall – Moisture retaining soil – Shade – Warm climate

Epidemiology • Ingest Eggs with Juveniles! – Very similar to Ascaris epidemiology

Trichinella spiralis • Males 1. 5 mm, Females 3 mm • Short esophagus • Stichosome • Psuedobursa • No copulatory spicule • Single gonad • Uterus contains fully developed eggs

Trichinella spiralis • Parasites of carnivorous mammals • Causes Trichinosis • Unusual life cycle – Same individual host is both definitive and intermediate host – Adults in small intestine – Juveniles inside muscle cells • Largest intracellular parasite

• Def. host is infected by ingesting juveniles in the muscle of other hosts • Juveniles enter intestinal mucosa • 4 molts • Growth

• Copulation • Within 32 hours after ingestion

Adults in small intestine • Thread throughout intestinal cells • Females release juveniles into mucosa • Thousands over 4 -16 weeks

• Juveniles enter hepatoportal system • Carried to liver, heart, lungs, then arterial system • Distributed throughout body

• Penetrate cells of skeletal muscle • Grow to about 1 mm • Infective in 4 -6 weeks

• How do the juveniles fit inside a muscle cell? • How do juveniles survive inside a muscle cell?

Nurse Cell • Juveniles take over cell – Redirect cell activities to their survival • Alter gene expression – From a contractile fiber – To a cell that nourishes the worm • Cell becomes encapsulated with collagen • Blood vessels form around the cell • Juveniles arrest development • Live for months-years and up to 39 years • Die from calcification

Which muscles? • Commonly – Eye – Tongue – Masticatory – Diaphragm – Intercostals – Heavy muscles of arms and legs

Diagnosis and Treatment • • Most cases go undetected Difficult to diagnose Symptoms are vague Difficult to find juveniles in tissue – Muscle biopsy – But too late • No treatment to kill parasites – Shielded from drugs • Treat symptoms

Epidemiology • Cosmopolitan – Circumboreal (northern areas of North America and Eurasia) – Less common in tropical areas • Common in U. S. – – – 1940 -1950 high prevalence Decreased until 1980 Asian immigrants consuming raw pork • Transmission cycles – Domestic – Sylvatic

Domestic Cycle PIG Nip tails RAT PIG Cannibalism Scavenging, Eating human garbage DEAD END Eat undercooked pork Humans Feed garbage to pigs Raise pigs Create rat habitat Keep infection cycle going Eats rats