Nematodes - Teaching Demo

An Introduction to the Nematodes Christian Gallardo, MD

Helminths • Three phyla: – Annelida (Segmented Worms) – Nemathelminthes (Roundworm) • Nematoda – Plathyhelminthes (Flatworms) • Cestoda (Tapeworms) • Trematoda (Flukes)

Nematodes • Free living and parasitic • More than 80,000 are parasitic to vertebrates • 2mm (Strongyloides stercoralis) to a meter ( Dracunculus medinensis) • Sexes usually separate, male smaller than female

Morphology – Elongate cylindrical worm – Symmetrical bilaterally – Body • Outer, hyaline, noncellular cuticle • Subcuticular epithelium – Four longitudinal cords – dorsal, ventral and 2 lateral » Carry nerves and excretory canals • Layer of muscle cells

Morphology – Alimentray tract • Simple • Mouth: surrounded with lips, some may have teeth or plates • Esophagus • Intestine: flattened tube, straight course up to the rectum – No circulatory system • Hemoglobin, glucose, proteins, salts and vitamins – Nervous system • Ring or commisure of connected ganglia surrounding the esophagus • Sensory organs: Labial, cervical, anal, and genital regions

Morphology – Male reproductive organ • Porterior 3rd of the body – Testis, vas deferens, seminal vesicle, and ejaculatory duct • Accessory copulatory apparatus – 1 or 2 ensheated spicules – Gubernaculum – Copulatory Bursa: winglike appendedages – Female reproductive organ • Single or bifurcated tube – Ovary, oviduct, seminal receptacle, uterus, ovejector, and vagina – 20 – 200,000 eggs

Physiology – Excretory system • 2 lateral canals that lie in the lateral longitudinal cords – 2 Longitudinal muscles – for sinuous movement

• Thigmotropism – penetration of the skin by the hookworm larvae • Methods of obtaining food – – – –

Sucking with ingestion of blood (Ancyclostoma) Ingestion of lysed tissues and blood (Trichuris) Feeding Intestinal content (Ascaris) Ingestion of nourishment from the body fluids (filarial worms)

Physiology • Anaerobic – metabolic process – Glycogen content is high – Major portion expended in the production of large number of ova

• Resist digestive juices and tissue invaders – Afforded by the cuticle and elaboration of antienzymes

• Life Span: – – – –

Trichinella spiralis: 4-16 weeks Enterobius vermicularis: 1-2 months Ascaris lumbricoides: 12 months Persist for at least 14 years

INTESTINAL HELMINTHS • • • • •

Ascaris lumbricoides (roundworm) Trichinella spiralis (trichinosis) Trichuris trichiura (whipworm) Enterobius vermicularis (pinworm) Strongyloides stercoralis (Cochin-china diarrhea) • Ancylostoma duodenale and Necator americanes (hookworms)

Ascaris lumbricoides (Large intestinal roundworm)

Ascaris lumbricoides (Large intestinal roundworm) • Epidemiology – – – – –

Annual global morbidity: 1 billion/ year Mortality: 20,000/ year. Occur at all ages, More prevalent: 5 to 9 years age group. The incidence is higher in poor rural populations

• Morphology – – – –

Female: 22 – 35 cm; Male: 10 – 31 cm Smooth finely straited cuticle Conical anterior and posterior extremities Ventrally curved papilatted posterior extremity (male)

Ascaris lumbricoides (Large intestinal roundworm) – Terminal mouth with three oval lips with sensory papillae – Paired reproductive organs – posterior 2/3rd in (female) – Single long tortuous tubule(male)

• Eggs

Ascaris lumbricoides (Large intestinal roundworm)

Ascaris lumbricoides (Large intestinal roundworm) • Symptoms – Usual infection: 5 -10 worms – unnoticed by host – Routine stool examination – Vague Abdominal Pain – Eosinophilia – Loeffler’s Syndrome – migrating Ascaris larvae

Ascaris lumbricoides (Large intestinal roundworm) • Diagnosis – Identification of eggs (40 to 70 micrometers by 35 to 50 micrometers) in the stool. – Outline of the worm in Upper GI series

• Treatment and Prevention – Mebendazole, 200 mg (Adults); 100 mg (Children) for 3 days is effective – Piperazine Citrate, 75mg/kg/day – Good hygiene is the best preventive measure – Sanitary disposal of feces and health education – Night soil not be used unless treated with chemicals

Ascaris lumbricoides (Large intestinal roundworm) • Special Considarations” – Isolation is unnecessary • Proper disposal of stool and soiled linen – NG suctioning, provide good mouth care – Washing of hands – Inform of patient of adverse effect of drug • Piperazine – CI on seizure disorder • Mebendazole – adbominal pain and diarrhea

Trichinella spiralis (Trichinosis)

Trichinella spiralis (Trichinosis) •

Epidemiology – Related to the quality of pork and consumption of poorly cooked meat – Autopsy surveys: 2 percent infected/ population is infected – Mortality is low

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Morphology – Female: 3.50mm x 0.06 mm, Male: 1.50mm x 0.04mm – A slender anterior end with a small, orbicular, nonpapillated mouth – Posterior end bluntly rounded in the female – Ventrally curved with two lobular caudal appendages in male

Trichinella spiralis (Trichinosis) – A single ovary with vulva in the anterior fifth in the female – Long narrow digestive tract – Larvae: spearlike burrowing tip at tapering end: 80 – 120 microns and grows up to 900 to 1300 microns

Trichinella spiralis (Trichinosis) • Life Cycle – Infection occurs by ingestion of larvae, in poorly cooked meat. – Invade intestinal mucosa and sexually differentiate within 18 to 24 hours. – The female, after fertilization, burrows deeply in the small intestinal mucosa, whereas the male is dislodged (intestinal stage). – On about the 5th day eggs begin to hatch in the female worm and young larvae are deposited in the mucosa – They reach the lymphatics, lymph nodes and the blood stream (larval migration).

Trichinella spiralis (Trichinosis) – Larval dispersion occurs 4 to 16 weeks after infection. – The larvae are deposited in muscle fiber and, in striated muscle, they form a capsule which calcifies to form a cyst. – In non-striated tissue, such as heart and brain, the larvae do not calcify; they die and disintegrate. • Persist for several years. – One female worm produces approximately 1500 larvae. – Man is the terminal host. The reservoir includes most carnivorous and omnivorous animals.

Trichinella spiralis (Trichinosis) Symptoms Trichinosis Symptomatology Intestinal mucosa (24-72 hrs) Nausea, vomiting diarrhea, abdominal pain, headache.

Circulation and muscle Edema, peri(10-21 orbital days) conjunctivit is, photo phobia, fever, chill, sweating, muscle pain, spasm, eosinophili

Myocardium (10-21 days) Chest pain, tachycardia , EKG changes, edema of extremities , vascular thrombosis .

Brain and meninges (14-28 Headache days) (supraorbit al), vertigo, tinnitus, deafness, mental apathy, delirium, coma, loss of reflexes.

Trichinella spiralis (Trichinosis) • Diagnosis – Early in infection, serologic test: NEGATIVE – Serum levels of muscle enzymes (CPK, LDH) – Muscle Biopsy – most definitive diagnosis • 3rd to 4th week best time to do biopsy

• Treatment and Prevention – – – –

Mebendazole: 1000mg/day for 10-14 days Oral prednisone: 20 – 40mg daily Elimination of parasite in hogs Adequate cooking of meat products • Larvae are killed at 55C to 77C

Trichuris trichiura (whipworm)

Trichuris trichiura (whipworm) • Epidemiology – A tropical disease of children (5 to 15 yrs) in rural Asia (65% of the 500-700 million cases) – Seen in the South Americas, • concentrated in families and groups with poorer sanitary habits. – Distribution coextensive with A. lumbricoides

• Morphology – Attenuated whip like anterior, three fifths traversed by a narrow esophagus resembling a string of beads – A more robust posterior, 2/5th containing the intestine and a single set of reproductive organs

Trichuris trichiura (whipworm) – Male: 30-45mm, Female: 35-50mm – Bluntly rounded posterior end of the female – Coiled posterior extremity of the male • single spicule and retractile sheath – Eggs: 3000 – 10000/ day • Lemon shaped with pluglike translucent polar prominences (lantern shaped)

Trichuris trichiura (whipworm) • Life Cycle – The unembryonated eggs are passed with the stool – In the soil, the eggs develop into a 2-cell stage and an advanced cleavage stage – Eggs embryonate – Eggs become infective in 15 to 30 days – After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine – Release larvae that mature and establish themselves as adults in the colon

Trichuris trichiura (whipworm) – The adult worms (approximately 4 cm in length) live in the cecum and ascending colon • Found anterior portions threaded into the mucosa. – The females: Oviposit 60 to 70 days after infection. – Life Span: 1 year – The embryo is killed under desiccation at 37C within 15 minutes • Lethal temp: 52C and -9C

Trichuris trichiura (whipworm) • Symptoms – Worm burden: less than 10 worms are asymptomatic. – Heavier infections (e.g., massive infantile trichuriasis) • Chronic profuse mucus and bloody diarrhea • Abdominal pains • Edematous prolapsed rectum. – Malnutrition, weight loss and anemia – Sometimes death.

• Diagnosis – Stool exam: Lemon shape eggs in feces

Trichuris trichiura (whipworm) • Treatment and Prevention – Mebendazole, 200 mg (Adults); 100 mg (Children) for 3 days is effective – Highly endemic and may be prevented by • Treatment of infected individuals • Sanitary disposal of human feces • Personal hygiene • Thorough washing of hands • Scalding of uncooked vegetables

Strongyloides stercoralis (Threadworm)

Strongyloides stercoralis (Threadworm) •

Epidemiology – – – –

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Cochin-China diarrhea, 50 to 100 million cases worldwide, Tropical and subtropical areas with poor sanitation. Prevalent in the South and among Puerto Ricans.

Morphology – Varies depending on whether it is parasitic or freeliving. – The parasitic female is larger (2.2 mm x 45 micrometers) than the free-living worm (1 mm x 60 micrometers). • Colorless semitransparent

Strongyloides stercoralis (Threadworm) – The eggs, when laid are 55 micrometers by 30 micrometers. – Rhabditiform larvae: 225 microns x 16 microns • Long slender, nonfeeding, infective, filariform larvae

Strongyloides stercoralis (Threadworm) • Strongyloides life cycle: complex – alternation between free-living and parasitic cycles – potential for autoinfection and multiplication within the host. – Two types of cycles” • Free-living cycle: – The rhabditiform larvae passed in the stool can either molt twice and become infective filariform larvae (direct development) or molt four times – Become free living adult males and females that mate and produce eggs from which rhabditiform larvae hatch.

Strongyloides stercoralis (Threadworm) – The latter in turn can either develop into a new generation of free-living adults or into infective filariform larvae – The filariform larvae penetrate the human host skin to initiate the parasitic cycle • Parasitic cycle: – Filariform larvae in contaminated soil penetrate the human skin – Transported to the lungs » penetrate the alveolar spaces; – Bronchial tree to the pharynx, are swallowed and then reach the small intestine

Strongyloides stercoralis (Threadworm) – Small intestine: Molt twice and become adult female worms – The females: threaded - epithelium of the small intestine » Produce eggs which yield rhabditiform larvae. – Rhabditiform larvae » passed in the stool » Autoinfection: become infective filariform larvae : can penetrate either the intestinal mucosa (internal autoinfection) or the skin of the perianal area (external autoinfection)

Strongyloides stercoralis (Threadworm) • Symptoms – Light infections: asymptomatic. – Skin penetration causes itching and red blotches – During migration: bronchial verminous pneumonia – Duodenum: • Burning mid-epigastric pain and tenderness • Nausea and vomiting. • Diarrhea and constipation may alternate.

Strongyloides stercoralis (Threadworm) – Heavy, chronic infections • Anemia, weight loss and chronic bloody dysentery. – Secondary bacterial infection of damaged mucosa may produce serious complications.

• Diagnosis – – – –

Examination of feces and duodenal contents String test: duodenal fluid Baermann Technique ELISA (enzyme-linkedimmunosorbent assay)

Strongyloides stercoralis (Threadworm) • Treatment and prevention – – – –

Thiobendazole: 25mg/kg/BID x 3 days Alternate: Albendazole and Ivermectin Sanitary disposal of human feces Protection of the skin from contact with contaminated soil

Enterobius vermicularis (Pinworm, Oxyuriasis)

Enterobius vermicularis (pinworm, oxyuriasis) •

Epidemiology – Commonest helminthic infection in the US (18 million cases at any given time). – Worldwide: 210 million. – Urban disease of children in crowded environment (schools, day care centers, etc.) – The incidence in whites is much higher than in blacks

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Morphology – Female:8 mm x 0.5mm; Male: 2mm – 5mm. – Female: • Cuticular alar expansion at anterior end • Prominent esophageal bulb • Long pointed tail

Enterobius vermicularis (pinworm, oxyuriasis) – Eggs: 60mm x 27mm • Ovoid • Asymmetrically flat on one side.

Enterobius vermicularis (pinworm, oxyuriasis) • Life Cycle – Eggs are deposited on perianal folds – Self-infection • Transferring infective eggs to the mouth with hands that have scratched the perianal area – Person-to-person transmission – Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting). – Eggs: airborne and inhaled. • Swallowed -- Ingested eggs.

Enterobius vermicularis (pinworm, oxyuriasis) – Larvae: Small intestine – Adults: Colon – The time interval from ingestion of infective eggs to oviposition by the adult females is about one month – Life span: 2 months – Gravid females migrate nocturnally outside the anus • oviposit while crawling on the skin of the perianal area – The larvae contained inside the eggs develop in 4 to 6 hours – Retroinfection • The migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown

Enterobius vermicularis (pinworm) •

Symptoms – Relatively innocuous and rarely produces serious lesions. – The most common symptom: perianal, perineal and vaginal irritation caused by the female migration. • Insomnia and Restlessness. – Gastrointestinal symptoms (pain, nausea, vomiting, etc.) – Mother Complex • The conscientious housewife's mental distress, guilt complex, and desire to conceal the infection from her friends and mother-in-law is perhaps the most important trauma of this persistent, pruritic parasite.

Enterobius vermicularis (pinworm) • Diagnosis – Finding the adult worm or eggs in the perianal area, particularly at night. • Scotch tape / pinworm paddle – Made upon the morning before bathing or defecation

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Treatment – Pyrental Pamoate: 2 doses (10 mg/kg; maximum of 1g each) two weeks apart • Very high cure rate. – Alternative: Mebendazole. – The whole family should be treated, to avoid reinfection.

Enterobius vermicularis (pinworm) – Bedding and underclothing must be sanitized between the two treatment doses. – Personal cleanliness provides the most effective in prevention.

Necator americanes and Ancylostoma duodenale (Hookworms)

Necator americanes and Ancylostoma duodenale • Epidemiology – More than 900 million people worldwide – Cause daily blood loss of 7 million liters – Ancylostomiasis • Most prevalent hookworm infection • Second only to ascariasis in infections by parasitic worms. – N. americanes (new world hookworm) • Most common in the Americas, central and southern Africa, southern Asia, Indonesia, Australia and Pacific Islands.

Necator americanes and Ancylostoma duodenale – A. duodenale (old world hookworm) • Dominant species in the Mediterranean region and northern Asia.

• Morphology – Small cylindrical, fusiform, grayish white nematodes. – Female: 9 – 13mm, Male: 5 – 11mm – Thick cuticle – Bursa • Broad, translucent, membranous caudal bursa with riblike rays at the posterior end of the male • Used for attachment to the female during copulation

Necator americanes and Ancylostoma duodenale – N. americanes • Buccal capsule is conspicious • Dorsal pair of semilunar cutting plates • Concave dorsal median tooth • Deep pair of triangular subventricular lancets – A. duodenale • 2 ventral pairs of teeth – Egg • Sinle thin transparent hyaline shell • 2 – 8 cell stages division in fresh feces

Necator americanes and Ancylostoma duodenale •

Life cycle – Eggs are passed in the stool – Under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. – Rhabditiform larvae grow in the feces and/or the soil • After 5 to 10 days (and two molts) they become become filariform (third-stage) larvae that are infective. – Infective larvae can survive 3 to 4 weeks in favorable environmental conditions. – On contact with the human host, the larvae penetrate the skin • Carried through the veins to the heart and then to the lungs

Necator americanes and Ancylostoma duodenale – Filariform penetrate pulmonary alveoli – Ascend the bronchial tree to the pharynx, and are swallowed • Reach the small intestine, where they reside and mature into adults. – Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host. – Most adult worms are eliminated in 1 to 2 years, but longevity records can reach several years. – Some A. duodenale larvae, following penetration of the host skin, can become dormant (in the intestine or muscle). – A. duodenale infection • may probably also occur by the oral and transmammary route. – N. americanus infection • requires a transpulmonary migration phase.

Necator americanes and Ancylostoma duodenale Table 2. Clinical features of hookworm disease Site Dermal

Pulmonary

Gastro- intestinal

Hematologic

Symptoms Local erythema, macules, papules (ground itch) Bronchitis, pneumonitis and, sometimes, eosinophilia Anorexia, epigastric pain and gastrointestinal hemorrhage Iron deficiency, anemia, hypoproteinemia, edema, cardiac failure

Pathogenesis Cutaneous invasion and subcutaneous migration of larva Migration of larvae through lung, bronchi, and trachea Attachment of adult worms and injury to upper intestinal mucosa Intestinal blood loss

Necator americanes and Ancylostoma duodenale • Diagnosis – Identification of hookworm eggs in fresh or preserved feces. – Species of hookworms cannot be distinguished by egg morphology.

• Treatment and control – Mebendazole, 200 mg, for adults and 100 mg for children, for 3 days is effective. – Sanitation is the chief method of control: sanitary disposal of fecal material and avoidance of contact with infected fecal material.