Intestinal Nematodes PDF

Phylum: Nemathelminthes  Class: Nematoda ❖ Nematodes or round worms (from Greek: nema, nematos = thread and ode = like) are characterized by the following general features: ✓ Elongate, cylindrical, round or oval. ✓ Bilaterally symmetrical, tapering at both ends. ✓ Non-segmented, have...

Phylum: Nemathelminthes  Class: Nematoda ❖ Nematodes or round worms (from Greek: nema, nematos = thread and ode = like) are characterized by the following general features: ✓ Elongate, cylindrical, round or oval. ✓ Bilaterally symmetrical, tapering at both ends. ✓ Non-segmented, have well developed digestive tract. ✓ Sexes are separate and the male is shorter and more slender than female. ✓ Round worms have no circulatory or repiratory system. ✓ The digestive system: a simple tube extending from the mouth to the anus (mouth, oesophagus, midgut and anus). ✓ Reproduction is usually sexual through the genital systems. ❖ Nematodes infecting man may be divided into intestinal and tissue nematodes: I. Intestinal nematodes: have no intermediate host. These include: 1. Ascaris lumbricoides. 2. Trichuris trichiura. 3. Enterobius vermicularis. 4. Hook worms. 5. Strongyloides stercoralis. II. Tissue nematodes: require an intermediate host which is usually arthropod. These include: 1. Lymphatic : a) Wuchereria bancrofti. b) Brugia malayi. 2. Cutaneous : a) Onchocerca volvulus. b) loa- loa. c) Dracunculus medinensis. Phylum: Nemathelminthes Intestinal nematodes 1- Ascaris lumbricoides 2- Trichuris trichiura 3- Enterobius Vermicularis 4- Hook Worms I. Ancylostoma duodenale II. Necator americanus 5. Strongyloides stercoralis.  Ascaris lumbricoides (Giant intestinal round worm) ❖ Disease : Ascariasis ❖ Habitat : Small intestine. ❖ Definitive host : Man  Morphology and life cycle : ✓ The eggs remain viable for many years. The lipid layer of the eggshell contains a unique glycoside ascaroside which render the eggshell impermeable to many chemicals. ✓ The larva grows to an adult worm in about 2 months. ✓ The adult lives about 6-12 months. ❖ Pathogenicity: Light infection is usually asymtomatic 1. Migration phase (Pulmonary phase):  Larval migration through lungs causes a condition known as loeffler’s syndrome due to minute hemorrhages and eosinophilic infiltration.  Fever, cough with blood stained sputum.  Allergic manifestation as asthma and oedema.  Verminous pneumonitis. 2. Intestinal Phase : loeffler’s syndrome a. Toxic effect : i. By product of living or dead worms produce allergic manifestation, nervous irritability, anorexia, loss of weight and dyspepsia. ii. Worms produce a trypsin-inhibiting substance which interferes with protein digestion. iii. Digestive disorders as nausea, vomiting diarrhea and abdominal discomfort. b. Traumatic effect (Phase of complication): i. During migration many worms get lost and accumulate in almost every organ of the body causing acute tissue reaction. ii. When bacterial infections become superimposed death can result before the disease is diagnosed. iii. Heavy infection results in intestinal obstruction, perforation and peritonitis. ❖ Mode of infection:  The disease is transmitted by eating contaminated food with the embryonated eggs.  Transplacental migration into a developing foetus is known. Ascaris egg  ❖Diagnosis: 1. Finding the eggs in the faeces. 2. During the pulmonary phase, there may be eosinophilia and larvae may be found in sputum. ❖ Prevention and control:  As previously mentioned in the introduction. ❖ Treatment:  Mebendazole or flubendazole : 100mg twice for 3 days orally.  Albendazole : 400mg in a single dose.  Trichuris trichiura (Whip worm) ❖ Disease : Trichuriasis. ❖ Habitat : Large intestine mainly caecum. ❖ Definitive host : Man Morphology and life cycle : ❖ Pathogenicity :  Depend on intensity and duration of infection. 1- Light infection: usually asymptomatic. 2- Moderate infection: ✓ Generalized abdominal pain, colic. ✓ Anorexia, nausea. ✓ Profuse mucus and bloody diarrhea. 3- Heavy infection : ✓ Anaemia. ✓ Rectal prolapse. ✓ Intestinal perforation and peritonitis. ✓ Acute appendicitis. ❖ Diagnosis: Finding the eggs in the faces. Trichuris trichiura egg ❖ Prevention and control as ascariasis.  Enterobius Vermicularis (Pinworm) ❖ Disease : Enterobiasis , oxyuriasis. ❖ Habitat : Large intestine mainly caecum. ❖ Definitive host : Man Morphology and life cycle : ❖ Pathogenicity : ✓ Irritation and pruritis ani at night (Nocturnal periodicity).Scratching may cause dermatitis and secondary bacterial infection. ✓ Nervous irritability, restlessness and insomnia. ✓ Nausea, vomiting, colic diarrhea alternating with constipation. ✓ Appendicitis. ✓ In female patients, worms may migrate to vagina, uterus, bladder and urethra causing irritation and inflammation. ❖ Diagnosis: ✓ Recovery of adult worms from anus at night or on the stool. ✓ Eggs are best obtained by swabbing the perianal region by : a. NIH swab. b. Scotch adhesive tape swab. ✓ Eggs may be recovered from urine in female patients. Enterobius Vermicularis egg ❖ Mode of Infection: a. Auto infection (hand to mouth). b. In food or drink. c. Retroinfection. ❖ Prevention and Control: 1. Personal cleanliness. 2. Mass treatment. 3. Food and drink should be protected from dust and hands of infected persons. ❖ Treatment: 1. Flubendazole 100mg or albendazole 400mg as a single oral dose. 2. Local application of white mercury ointment around anus at night.  Hook Worms Ancylostoma duodenale & Necator americanus ❖ Disease : Ancylostomiasis ❖ Habitat : Small intestine, particularly jejunum. ❖ Definitive host : Man Morphology and life cycle : ❖Pathogencity:  Invasion or cutaneous phase (ground itch) : Dermatitis with itchy papules turns to vesicles with oedema and erythema.  Pulmonary migration phase: as in ascariasis.  Intestinal phase : a. Blood loss leads to hypochromic microcytic anemia. b. Toxins lead to physical and mental retardation. c. Intestinal ulcers, abdominal discomfort, nausea, vomiting, diarrhea or constipation. ❖Mode of infection:  Skin penetration of filariform larvae in moist soil through bare feet.  Ingesting infective larvae.  Transplacental transmission. ❖ Diagnosis: Finding eggs in feces. ❖ Prevention and control:  Use of footwear. Ancylostoma duodenale egg  Hygienic measures. ❖ Treatment:  Albendazole 400mg single dose.  Iron preparations to treat anemia.  Adequate nutrition with high protein diet.  Strongyloides stercoralis (Dwarf thread worm) ❖ Disease : Strongyloidiasis. ❖ Habitat : Stronglyloides is a facultative parasite which is capable of existing as free living in soil or parasitic forms in the small intestine of man ❖ DH: Man ❖ RH : Dogs and Monkeys Morphology and life cycle : ❖ Pathogenicity:  Cutaneous manifestations: as ancylostoma.  Pulmonary migration phase: Pulmonary manifestations are more severe than those of ascariasis and ancylostomiasis due to autoinfection.  Intestinal phase : Nausea, vomiting, epigastric pain. Watery diarrhea alternating with constipation. Death resulting from septicemia following ulceration of the intestine. ❖ Diagnosis:  The presence of free rhabditiform larva in the faeces is diagnostic.  Sputum examination shows larvae, eosinophils. Strongyloides stercoralis rhabditiform larva ❖ Mode of Infection:  Infective filariform larvae penetrate intact skin.  Autoinfection. Strongyloides stercoralis filariform larva ❖ Prevention and Control: as hookworms control. ❖ Treatment:  Albendazole: 400 mg once.  Ivermectin: 200 mg / kg daily for 2 days.