INTESTINAL NEMATODES Lecture NO -15- Mrs. Dalia Kamal Eldien MSC in Microbiology

Objectives  General characteristic of Nematode  Common species of Nematode  Ascaris lumbricoides (Transmission & life cycle, Clinical Features& laboratory diagnosis )  Enterobius vermicularis (Transmission & life cycle, Clinical Features& laboratory diagnosis )  Strongyloides stercoralis (Transmission & life cycle, Clinical Features& laboratory diagnosis )  Trichuris trichiura (Transmission & life cycle, Clinical Features& laboratory diagnosis )

General characteristic of nematode a)Nematodes are invertebrate roundworms b)Nematodes are non-segmented worms that are present in a variety of habitats. c)Nematodes are characterized by an external layer of cuticle that is secreted by the hypodermis underneath it. d)Nematodes lack a true coelom (body cavity) since their internal cavity is not lined by cells originating from the embryonic mesoderm. Instead, they possess a fluid- filled pseudocoel (incomplete coelum) that contains the intestine and reproductive organs.

d) Nematodes breathe across their entire body surface. e) Nematodes have a complete gut with a mouth and an anus& Teeth, which aid in obtaining food. The pharynx is muscular and pumps food through the gut, and nutrients are absorbed in the intestine. There is no internal system of circulation, so the transport of nutrients and wastes is achieved by diffusion Characteristic of nematode

characteristic of nematode f) Most nematodes have the same simple body plan. Their bodies are bilaterally symmetrical (one half is a mirror image of the other). Many have a "tube-within-a-tube" body plan comprised of a long, cylindrical body that encloses a hose-like canal called an alimentary canal. g) Food enters the alimentary canal on one end, and waste is expelled through the anus on the tail end. h) While nematodes have digestive, reproductive, nervous and excretory systems, they do not have a distinct circulatory or respiratory system.

Common species Most clinically important Intestinal Nematode species are:  Ascaris lumbricoides  Enterobius vermicularis  Strongyloides stercoralis  Trichuris trichiura  Ancylostoma duodenale Hook worms  Necator americanus. Tissue Nematode  Filarial worms  Dranculuculus medinensis (guinea worm )  Trichinella spiralis

Ascaris lumbricoides  Large worms, live in the lumen of the small intestine.  The mouth has three lips  Male has two spicules & the tail is curved ventrally  Female is oviparous, produce 200,000 eggs per day, which are excreted in stool and must incubate in soil for 3 to 4 weeks for the embryo to form and to become infectious.  Soil transmitted  Highest infection rates are in children. If infection is untreated, adult worms can live for 12 to 18 months, resulting in daily excretion of large numbers of ova.  Infection with A. lumbricoides is widespread but is most common in the tropics, in areas of poor sanitation, and where human feces are used as fertilizer.

Morphology Egg with infective larva, eggs yellow brown, covered with an albuminous coat, oval or round,60X40 µm Larva hatching from an egg An adult Ascaris worm

Adult worm is pinkish in color, mouth with 3 lips, measure up to 35 cm in length,male shorter Male posterior Characteristic hooked end with spicules Morphology

Transmission & life cycle  Eggs are long lived in soil- up to 15 years, resistant to drying, but killed by sunlight  Transmission by ingestion of contaminated food, water with infective eggs  Larvae hatch in the small intestine, penetrate the mucosa, and are transported passively by blood, follow a heart-lung migration, during which they develop. Larvae then ascend through the tracheobronchial tree to the pharynx, are swallowed, and mature into adults in the small intestine.  After mating the female produces eggs which passed in feces, within days of being passed each egg contains an infective larva.

Clinical Features  The incubation period is approximately 8 weeks.  Most infections are asymptomatic.  Lung Phase: 5-6 days after exposure Fever, Cough, Blood-tinged sputum, Dyspnea, Substernal pain, Eosinopilia, Urticaria, Asthma  Intestinal Phase: 2-3 months after infection - abdominal pain, diarrhea - malabsorption of nutrients - stunted growth, cognitive impairment - intestinal obstruction by high worm numbers

Wandering worms: - Intestinal perforation: peritonitis - Blockage of bile & pancreatic ducts - Obstruction of respiratory tract - Liver abscesse

Diagnosis  The laboratory diagnosis by finding the Eggs in feces  Occasionally, patients pass adult worms from  The rectum  From the nose after migration through the nares  From the mouth in vomits.

Eggs of Ascaris lumbricoides

Male& female of Ascaris lumbricoides

Enterobius vermicularis  Enterobius vermicularis is known as the human pin worm are one of the most common intestinal nematodes.  Most common anywhere poor hygiene is practiced  Causes Enterobiasis.  The adult worms inhabit the cecum and colon.  Right after mating, the male dies. Therefore, the male worms are rarely seen.  The female worms migrate out the anus depositing eggs on the perianal skin.  Humans get this infection orally and by autoinfection.  Airborne transmission of E. vermicularis eggs can also occur.

Morphology Adults: The adults look like a pin and are yellow- white in color. The female worm measures about 8 to 13 mm in size and has a thin pointed tail. The male adult is only 2-5mm. The tail of a male is curved. The anterior end is covered on each side by cuticular extensions called “ cephalic alae”. The esophagus is slender, terminating in a prominent posterior bulb, which is called esophageal bulb. The cephalic alae and esophageal bulb are important in identification of the species. Egg: 50 to 60 µm by 25 µm, oval(D-shape), colorless and transparent, thick and asymmetric shell, content is a larva.

Egg of Enterobius vermicularis

Enterobius vermicularis in the anus

Clinical Manifestations  Although some people are asymptomatic, pinworm infection (enterobiasis) may cause pruritus ani and, rarely, pruritus vulvae.  Pinworms have been found in the lumen of the appendix, so it may be associated with acute appendicitis.  Urethritis, vaginitis or salpingitis, may occur from migration of an adult worm from the perineum.

Diagnosis  Diagnosis depends on recovery of the characteristic eggs.  The eggs and the female adults can be removed from the folds of the skin in the perianal regions by the use of the cellophane tape method.  The examination should be made in the morning, before the patient has washed or defecated

Treatment: – Albendazol, and mebendazol are 95% effective but do not kill eggs so two or more treatments may be needed. Prevention: – Treat the patient and whole the family – Individual health –Health education and hygienic habits

Strongyloides stercoralis  Parasite of human intestine also known as "threadworm"  Most of pathology associated with larval stages that move through tissues  World wide distribution, endemic in many tropical & subtropical countries.  The Strongyloides life cycle is more complex than that of most nematodes with its alternation between free-living and parasitic cycles, and its potential for autoinfection and multiplication within the host.

Strongyloides stercoralis: adult female, measuring about 2 mm in length, has small buccal cavity surrounded by 4 lips

Strongyloides larvae Filariform larva (infective larva)is approximately 0.6 mm long and has a notched tail compared with that of hookworm which is sheathed and has a long slender tail. The rhabditiform larvae measure approximately 0.38 mm in length. They have a bulbed oesophagus and a short buccal cavity., rhabditiform larvae of S. stercoralis must be differentiated from those of hookworm which have a longer buccal cavity.

Eggs are rarely found in the stool as they hatch in the intestine. They are oval and thin shelled, resembling those of hookworm but are smaller measuring by microns.

Transmission By filariform (infective larvae) penetrating the skin By autoinfection with rhabditiform(first stage larvae) larvae in intestines or perianal skin. Transmammary(breast milk)

Clinical feature  Most infections with Strongyloides stercoralis are asymptomatic  Symptoms are most often related to larval skin invasion, tissue migration, and/or the presence of adult worms in the intestine  Infective (filariform) larvae are acquired from skin contact with contaminated soil, producing transient pruritic papules at the site of penetration.

 Larvae migrate to the lungs and can cause a transient pneumonitis like syndrome(coughing, shortness of breath, and fever.)  Symptoms of intestinal infection include vague abdominal pain, malabsorption, vomiting, and diarrhea with blood & mucous. Ulceration leading to anaemia & low plasma protein levels can occur.  Eosinophilia  Larval migration from defecate stool can result in pruritic skin lesions in the perianal area, buttocks, and upper thighs, which may present as serpiginous, erythematous tracks called larva currens.  Fatal infections in immunosupressed patients with involvement of CNS, heart, urinary tract, endocrine organs, and skin.

Migrating larvae of Strongyloides stercoralis in skin

Diagnosis  Finding S. stercoralis larvae in feces or doudenal aspirate, using the string test (Entero-Test).  Larvae excreted in intervals & in few numbers, so concentration techniques can be used  The use of culture methods may have greater sensitivity than fecal microscopy  In disseminated strongyloidiasis, filariform larvae may be isolated from sputum or bronchoalveolar lavage fluid as well as spinal fluid.  Serology  Eosinophilia (Eosinophil count greater than 500/µL) is common.

S.stercoralis larvae in feces

Treatment Ivermectin: 200 ug/kg per day Thiabendazole: 50 mg/kg per day Albendazole: 400 mg orally for adults and 15mg/kg per day for children Control measure –Sanitary disposal measures for human waste should be followed –Treating patients – Education about risk of infection through bare skin is important.

Trichuris trichiura ( Whipworm)  Causes trichuriasis  World wide distribution, more common in warm moist climates  Transmitted by faecally polluted soil, through ingestion of infective eggs  Children are more commonly affected.  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

Morphology:  Adult: the worm looks like a buggy whip, the anterior 3/5 is slender and the posterior 2/5 is thick. It is pinkish gray in color. The female worm is 3-5 cm in length and has a long slender esophageal region. The male is smaller than the female and has a curved tail.  Egg: it is barrel or spindle in shape and 50 x 20µm in size. It is brownish and has a translucent polar plug at either ends. The content of the egg is unsegmented

Adults of T. trichiura MaleFemale

Egg of T. trichiura

Clinical features  Light infection: Asymptomatic  Moderate infection: Clinical manifestations are usually abdominal pain, anorexia, diarrhea, constipation.  Heavy infection: Bloody diarrhea, eosinophilia, emaciation, prolapse of the rectum may occur.  Severe infection may increase the risk of infection with E. histolytica & pathogenic Enterobacteria.

Diagnosis By finding eggs in feces