INTESTINAL HELMINTHS

Introduction

Soil transmitted Helminthiasis includes Ascaris lumbricoides, Trichuris trichiura, Ancylostoma dudenale and Necator americanus. About one third of the global population is infected and it is an important cause of physical and intellectual retardation. It is most commonly seen in worm and moist climates and in areas where there is poor sanitation, poor hygiene and unsafe water supply. It is more prevalent in developing countries in Africa, South East Asia, China and South America. Morbidity depends on the heaviness of the infection.

ASCARIASIS

Life cycle

Ascaris lumbricoides infection is acquired by swallowing of embryonated ova from soil contaminated by human faeces. After being swallowed, the ova penetrate the intestinal wall, passes to the liver and thence through the systemic circulation to the lungs. There, it penetrates the alveoli, passes up the respiratory system to be swallowed again and develop into adults that inhabit the jejunum where they lay their ova. This life cycle takes about 12 weeks.

Clinical features

1- Larvae can penetrate into the:

a) Lungs: It causes cough, dyspneoa, wheezes and fever with patchy infiltrations on chest X-ray (Loffler's syndrome)

b) Brain leading to convulsions, meningism and insomnia

c) Kidneys

d) Liver

2- Adults worms:

Worm infestation may present with vomiting of worms, appear through the anus, penetrate to the peritoneum, cause obstructive jaundice by blocking the bile ducts, cause intestinal obstruction, malnutrition and anemia. Adult worms may also lead to allergic manifestations e.g. urticaria and asthma.

They may lead to malabsorption, anemia, growth retardation and cognitive impairment.

Laboratory tests:

• Stool examination to detect adult worms and Ova

• Full blood count for eosinophilia (high eosinophilia is a constant feature)

• Barium studies show string like appearance of worms.

Treatment

• Albendazole orally in a dose of 400mg given once.

• Mebendazole orally in a dose of 100mg to be given twice daily for 3 days.

ANCYLOSTOMIASIS (Hook worm)

The major 2 types known are Ancylostoma duodenale and Ancylostoma americanus.

Life cycle

An egg passed in stools, become larva in soil, penetrates the skin of man, passes through circulation to the lungs, migrates up the respiratory tract to be swallowed and eventually inhabits the intestines.

Clinical features

1-Larvae:

Ground-itch i.e. irritant rash after penetration of the skin.

2-Adults worms:

Iron deficiency anemia and malnutrition.

Laboratory tests

Stools and full blood count showing high eosinophil count.

Treatment

• Albendazole given orally in a single dose of 400mg

• Mebendazole given orally in a dose of 100mg twice daily for 3 days

• Pyrantel pamoate given orally in a dose of 11mg/kg/day for 3 days.

ENTEROBIASIS (Oxyuriasis, thread worm)

Enterobius vermicularis adult worm lives in the cecum and colon. The female migrates at night to lay its eggs around the anal area, thus causing severe nocturnal peri-anal itching. Sometimes it migrates up the perineum to the vulva and vagina. Scratching the itchy area leads to re-infection when the eggs, taken by the fingers and nails, are swallowed again.

Clinical features

• Perianal itching at night leads to insomnia and secondary infection.

• Vaginitis or ascending urogenital tract infection.

• Obstruction to the appendix may lead to appendicitis.

Laboratory tests

- Stool for worms and ova

- Adult worms seen at the anal area especially at night.

- sticking cellophane tape at the peri-anal area at night, and examining it under the microscope.

Treatment

• Albendazole given orally in a single dose 400mg once.

• Mebendazole given orally in a dose of 100mg twice daily for 3 days.

It is important to treat all the family and school members.

STROGYLOIDOSIS

Strongyloides stercoralis adult worm lives within the mucosa of the duodenum. Larvae escape into the intestinal tract, pass in the stools to the soil where it becomes infective, penetrates human skin and takes its route via the systemic circulation to the lungs and then re-swallowed into the gastrointestinal tract.

Clinical picture

1-Larva:

Through its travel in the tissues, it leads to creeping eruptions (larva currens) similar to cutaneous larva migrans. It is seen as erythematous serpiginous track with marked itching. Papular rash may be seen, most commonly in the legs and natal cleft.

2-Adult worms:

Presence of adult worms in the tissues may lead to diarrhea, abdominal pain and may lead to malabsorption. Hyperinfection occurs in immunosuppressed and HIV 1 patients leading to severe diarrhea and granuloma formation in the liver, kidneys, and lungs with serous effusions and C.N.S. involvement leading to meningitis and encephalopathy.

Laboratory tests

- Stool examination

- Duodenal aspirate for larva

- High eosinophil count

- Agar plate culture

- ELISA technique

- Serological tests

Treatment

• Albedazole given orally in a dose of 400mg/day for 7 days

• Ivermectin given orally in a dose of 200mg/kg/day for 2 days

• Thiabendazole given orally in a dose of 25mg/kg/day for 2-5 days.

TRICHURIASIS (Whip worm)

The adult worm Trichuris trichiura lives in the cecum. The female worm lye the eggs that pass out with stools. Infection is then acquired by drinking or eating contaminated fluids or food.

Clinical features

- Lower abdominal pain and dysentery i.e. prolonged diarrhea with blood, mucus and tenesmus, weight loss and Rectal prolapse due to tenesmus, weakened sphincters and worm load. Worms may be seen attached to the prolapsing bowel.

- Iron deficiency anemia

- Simultaneous infection with E.histolytica is common.

Laboratory tests

- Stool examination for adult worms and ova

- Proctoscopy and sigmoidoscopy reveal hyperaemic, friable and ulcerated mucosa.

- High eosinophil count

Treatment

• Mebendazole given orally in a single dose of 500mg.

• Albendazole given orally in a single dose of 400mg.

Three days course may be used for heavy infections.

ECHINOCOCCOSIS (Hydatid disease)

The adult Echinococcus granulosus is a small tape worm that lives in the upper G.I.T. of dogs and it passes ova in stools. Intermediate hosts are man, sheep, goats and pigs that ingest eggs through contaminated water and food or through close relationship with dogs. Ova then grow into oncospheres which penetrates the intestinal mucosa and travel in the blood vessels or lymphatics to host viscera including liver and lungs to develop into mature larval cyst.

Three types of echinococcosis are known to infect man:

a) E. granulosus: It forms a unilocular cyst in double membrane and it is not invasive.

b) E.multilocularis: It is invasive resembling malignancy (Alveolar type).

c) E. oligoarthuş: It is polycystic and invasive.

Clinical picture

Hydatid disease is a slowly progressive cystic tumor leading to destruction of the surrounding tissue. Leakage of the hydatid fluid may lead to allergic phenomena such as urticaria, asthma, oedema and anaphylaxis. Bacterial infection of the cyst can transform it into an abscess. Spread to other sites is produced when protscolices are released from a ruptured cyst. Protscolices are transported directly or via blood to other sites e.g. liver which is the most commonly affected organ, lungs, peritoneum, brain, bones, kidneys, heart and spleen. Pressure symptoms on these organs give organ-related symptoms and signs e.g. hepatomegaly or haemoptysis.

Laboratory tests

- Radiological examination

- Ultrasound

- Casoni skin test (false positive rate is high)

- Serology: haemagglutination, latex agglutination and immunoelectrophoresis.

- High eosinophil count.

Treatment

Ultrasound guided Percutaneous Aspiration Injection and Re-aspiration (PAIR) is a safe procedure and has high cure rate especially when followed by Albedazole treatment for 1 to 6 months orally in a dose of 400mg given twice daily.

Careful surgical removal of the cyst, whenever feasible.

DRACONTIASIS

The quinea worm Dracunculus medinensis infection occurs after drinking water from ponds containing water Cyclops (Crusacea and copepod). The adult worm lives in the subcutaneous and deep connective tissue and emerges through the surface of the skin to release the larvae where it causes blisters and severe itching which is relieved by immersing the limb in water. The dead worm may be seen calcified under the skin.

Diagnosis is made by seeing the adult worm emerging through the skin and with serology and high eosinophil count.

TREATMENT

• Adult worm could be pulled out gradually and slowly.

• Metronidazole given for one week or alternatively thiabendazole may be used instead.

TAENIASIS

Infection with Taenia saginata and Taenia solium is acquired by eating undercooked meat, beef and pork respectively. The adult worm is 3-5 meters long and attaches itself to the intestinal wall through suckers as in case of T. saginata or by hooklets as in case of T. solium

Clinical features:

The infection can be symptomless.

Symptoms when they occur include vague or colicky abdominal pain, abdominal distension and irregular bowel movements.

Despite an increased appetite, there is usually poor weight gain and malnutrition.

Laboratory tests

• Proglottids may be seen in the anal area or in the stools

• Ova in the stools

• Mild to moderate eosinophilia

CYSTICERCOSIS

is due to invasion of tissue by T.solium. It can cause CNS manifestations if it invaded the CNS viz. epilepsy, hydrocephalus, dementia, infarcts, meningitis, cranial nerve palsies, spinal symptoms, and blindness. Subcutaneous and muscular cysts may calcify and appear as firm nodules.

TREATMENT

• Praziquatel 10mg/kg orally once

For cystocercosis, praziquatel dose is 25 mg/kg in 2 divided dose 2hours apart.

• Albendazole 15mg/kg/day in 2 divided doses for 8-30 days is used (add dexamethasone 0.4mg/kg/day for the first 10 days).

TAENIA NANA

Adwarf taenia (2-5cm long) acquired by eating infected grains. It is usually asymptomatic but may cause diarrhea.

TREATMENT

Treatment is not necessary, but if needs be, then praziquantel is used as above.

Preventive Anthelminthic Chemotherapy

Helminth infections in the developing countries are usually due to more than one helminth at a time and its high morbidity rate has a direct impact on health, productivity and economy of the affected people and countries. Isotopic studies of blood loss in patients infested with intestinal worms e.g. Necator Americanus showed that a single worm sucks about 0.03 ml of blood per day while Ancylostoma dudenale sucks about 0.2ml per day. This indicates that a moderate infestation of N. Americanus of 80 adult worms causes a loss of 2mg of iron per day. Trichuris causes a loss of 0.005 ml of blood per day, and a heavy infestation of 800 parasites will lead to a loss of 4 ml of blood i.e. 1.5mg iron per day. Though some of this iron will be reabsorbed, iron stores will eventually be reduced leading to iron deficiency anemia. These facts indicate clearly that heavy worm infestations lead to chronic blood loss that culminates in severe iron deficiency anemia. In the year 2006 the World Health Organization (WHO) recommended that broad spectrum anthelminthic drugs - single or in combinations- should be used in the general preventive measures and programs to control or eliminate helminthiasis in the affected areas. Diseases targeted by these programs included Filariasis, Onchocerciasis, Schistosomiasis and Soil-Transmitted Helminthes (Ascaris, Ancylostoma, Trichura, and Strongyloides) and Taeniasis. Scheduled programs to control or eliminate these diseases should be explained clearly to the targeted community together with the information on the prevalence of the disease, morbidity, time and method of drug dosing and the possible side effects that may arise on using these drugs. Drug supply, transport and storage must be secured ahead of these campaigns. Trained health personnel, community leaders and volunteers, school teachers and traditional healers should all be involved. Coordination plan and road maps or algorithms should be prepared and well explained to the participants. In areas where it is cult to secure handy, efficient and durable weighing scale, WHO recommended a dose pole where height-dependent instead of weight-dependent doses are used.