Helminthes Parasites

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Intestinal Worms

Intestinal worms enter the human body through ingestion of the worm eggs in food or water via dirty hands or through injured skin when walking barefoot. Examples include:

TYPE OF INFESTATION

 

FEATURES

Ascariasis Ascaris lumbricoides (round worm). Infests small intestines
  • Oro-faecal transmission
  • Usually few or no symptoms
  • Persistent dry irritating cough
  • Patient may pass out live worms through the anus, nose, or mouth
  • Pneumonitis- Loeffler’s syndrome
  • Heavy infestations may cause nutritional deficiencies
  • Worms may also cause obstruction to bowel, bile duct, pancreatic duct, or appendix

Enterobiasis (threadworm) Enterobias vermicularis
  • Transmitted by faecal-oral route
  • Mainly affects children
  • Intense itching at the anal orifice

Hook worm Caused by Necator americanus and Ancylostoma duodenale
  • Chronic parasitic infestation of the intestines
  • Transmitted by penetration of the skin by larvae from the soil
  • Dermatitis (ground itch)
  • Cough and inflammation of the trachea (tracheitis) common during larvae migration phase
  • Iron-deficiency anaemia
  • Reduced blood proteins in heavy infestations

Strongyloidiasis Strongyloides stercoralis
  • Skin symptoms: Itchy eruption at the site of larval penetration
  • Intestinal symptoms e.g. abdominal pain, diarrhoea, and weight loss
  • Lung symptoms due to larvae in the lungs, e.g. cough and wheezing
  • Specific organ involvement, e.g. meningoencephalitis
  • Hyperinfection syndrome: Occurs when immunity against auto-infection fails, e.g. in immunosuppressed cases

Whip worm

Whip worm

Infests human caecum and upper colon
  • May be symptomless
  • Heavy infestation may cause bloody, mucoid stools, and diarrhoea
  • Complications include anaemia and prolapse of the rectum

Differential diagnosis

  • Other causes of cough, diarrhea
  • Other causes of intestinal obstruction and nutritional deficiency
  • Loeffler’s Syndrome
  • Other causes of iron-deficiency anaemia

Investigations

  • Stool examination for ova, live worms or segments
  • Full blood count

Management

Treatment LOC

Roundworm, threadworm, hookworm, whipworm

  • Albendazole 400 mg single dose
    • Child <2 years: 200 mg
  • Mebendazole 500 mg single dose
    • Child <2 years: 250 mg
 HC1

Strongyloides

  • Albendazole 400 mg every 12 hours for 3 days
  • Or Ivermectin 150 micrograms/kg single dose 
 HC3

 

Prevention

  • Proper faecal disposal
  • Personal and food hygiene
  • Regular deworming of children every 3-6 months
  • Avoid walking barefoot

Taeniasis (Tapeworm)

An infestation caused by Taenia (Taenia saginata (from undercooked beef ), Taenia solium (from undercooked pork), Diphyllobothrium latum (from undercooked fish).

Cause

  • Adult Tapeworms: intestinal infestation, by ingestion of undercooked meat containing cysticerci (larval form of the worm)
  • Larvae forms (cysticercosis): by ingestion of food/water contaminated by eggs of T.solium. The eggs hatch in the intestine, the embryos invade the intestinal walls and disseminate in the brain, muscles or other organs

Clinical features

T. saginata, T.solium (adult tapeworm)

  • Usually asymptomatic, but live segments may be passed
  • Epigastric pain, diarrhoea, sometimes weight loss

Cysticercosis

  • Muscular: muscle pains, weakness, fever, subcutaneous nodules
  • Neurocysticercosis: headache, convulsions, coma, meningo-encephalitis, epilepsy
  • Ocular: exophthalmia, strabismus, iritis

D. latum

  • Usually asymptomatic, but mild symptoms may occur
  • Megaloblastic anaemia may occur as a rare complication

Differential diagnosis

  • Other intestinal worm infestations

Investigations

  • Laboratory: eggs, worm segments in stool or collected from perianal skin (scotch tape method)
  • Cysticercosis: hypereosinophilia in blood and CSF

Management

Treatment LOC

Tapeworm

  • Praziquantel 5-10 mg/kg single dose

Alternative

  • Niclosamide
    • Adult and child > 6 years: 2 g single dose
    • Child < 2 years: 500 mg
    • Child 2-6 years: 1 g
  • Give Bisacodyl 2 hours after the dose

HC3

HC4

Cysticercosis

  • Refer to specialised facilities
  • Antiparasitic treatment without diagnosis of location by CT or MRI scan can worsen symptoms, and even threaten the life of the patient.
  • Neurosurgical treatment required
 RR

 

Prevention

  • Cook all fish and meat thorougly
  • Proper hygiene: handwashing, nail cutting, proper disposal of faeces

Echinococcosis (Hydatid Disease)

Tissue infestation by larvae of Echinococcus granulosus. It is transmitted through direct contact with dogs or by ingesting water and food contaminated by dog faeces.

Clinical features

  • Cough, chest pain
  • Liver cysts may be asymptomatic but may also give abdominal pain, palpable mass and jaundice (if the bile duct is obstructed)
  • Rupture of cysts may cause fever, urticaria, or anaphylactic reaction
  • Pulmonary cysts can be seen on chest X-ray and may rupture to cause cough, chest pain and haemoptysis

Differential diagnosis

  • Amoebiasis, hepatoma
  • Other causes of liver mass and obstructive jaundice
  • Tuberculosis (TB)

Investigations

  • Skin test
  • Ultrasound
  • Chest X-ray: for pulmonary cysts
  • Serological tests
  • Needle aspiration under Ultrasound Sonography (US) or CT-scan guidance

Management

Treatment LOC

Refer for specialist management

  • Surgical excision

Prior to surgery or in cases not amenable to surgery

  • Albendazole
    • Child >2 years and adults: 7.5 mg/kg every 12 hours for 3-6 months
 RR

Prevention

  • Food hygiene
  • Health education
  • Proper disposal of faeces

Dracunculiasis (Guinea Worm)

An infestation of the subcutaneous and deeper tissue with the guinea worm. It is a notifiable disease.

Cause

  • Dracunculus medinensis, transmitted to man by drinking water containing cyclops (waterflea or small crustacean) infected with larvae of the guinea worm

Clinical features

  • Adult worm may be felt beneath the skin
  • Local redness, tenderness, and blister (usually on the foot) at the point where the worm comes out of the skin to discharge larvae into the water
  • There may be fever, nausea, vomiting, diarrhoea, dyspnoea, generalised urticaria, and eosinophilia before vesicle formation
  • Complications may include cellulitis, septicaemia, and aseptic or pyogenic arthritis; tetanus may also occur

Differential diagnosis

  • Cellulitis from any other causes
  • Myositis

Investigations

  • Recognition of the adult worm under the skin
  • X-ray may show calcified worms

Management

Treatment  LOC

There is no known drug treatment for guinea worm

All patients:

  • To facilitate removal of the worm, slowly and carefully roll it onto a small stick over a period of days
  • Dress the wound occlusively to prevent the worm passing ova into the water
  • Give analgesics for as long as necessary

If there is ulceration and secondary infection give:

  • Amoxicillin 500 mg every 8 hours for 5 days
    • Child: 250 mg every 8 hours for 5 days
  • Or cloxacillin 500 mg every 6 hours for 5 days
 HC2

 

Prevention

  • Filter or boil drinking water
  • Infected persons should avoid all contact with sources of drinking water

Lymphatic Filariasis

Lymphatic filariasis is a disease caused by tissue dwelling nematode, transmitted by the Aedes aegypti mosquito bite

Causes

  • Wuchereria bancrofti

Clinical features

Acute

  • Adenolymphangitis- inflammation of lymph nodes and lymphatic vessels (lower limbs, external genitalia, testis, epididymis or breast)
  • With or without general signs like fever, nausea, vomiting
  • Attacks resolve spontaneously in one week and recur regularly in patients with chronic disease

Chronic

  • Lymphoedema (chronic hard swelling) of limbs or external genitalia, hydrocele, chronic epididymo orchitis, initially reversible but progressively chronic and severe (elephantiasis)

Differential diagnosis

  • DVT
  • Cellulitis

Investigations

  • Blood slide for Microfilaria (collect specimen between 9 pm and 3 am)

Management

Treatment LOC

Case treatment

  • Supportive treatment during an attack (bed rest, limb elevation, analgesics, cooling, hydration)
  • Doxycycline 100 mg twice a day for 4-6 weeks (do not administer antiparasitic treatment during an acute attack)

Chronic case

  • Supportive treatment: bandage during the day, elevation of affected limb at rest, analgesics and surgery (hydrocelectomy)

Large scale treatment/preventive chemotherapy

  • Give annually to all population at risk, for 4-6 years
  • Ivermectin 150-200 mcg/kg plus albendazole 400 mg single dose

Not effective against adult worms

    • Ivermectin is not recommended in children < 5 years, pregnancy, or breast-feeding mothers
    • No food or alcohol to be taken within 2 hours of a dose
 HC2

Prevention

  • Use of treated mosquito nets
  • Patient Education

Onchocerciasis (River Blindness)

Chronic filarial disease present in areas around rivers

Cause

  • Onchocerca volvulus, transmitted by a bite from a female black fly (Simulium damnosum, S. naevi and S. oodi, etc), which breeds in rapidly flowing and well-aerated water

Clinical features

Skin

  • Onchocercoma: painless smooth subcutaneous nodules containing adult worms, adherent to underlying tissues, usually on body prominences like iliac crests, pelvic girdle, ribs, skull
  • Acute papular onchodermatitis: Intense pruritic rash, oedema (due to microfilariae)
  • Late chronic skin lesions: dry thickened peeling skin (lizard skin), atrophy, patchy depigmentation

Eye

  • Inflammation of the eye (of the cornea, uvea, retina) leading to visual disturbances and blindness

Differential diagnosis

  • Other causes of skin depigmentation (e.g. yaws, burns, vitiligo)
  • Other causes of fibrous nodules in the skin (e.g. neurofibromatosis)

Investigations

  • Skin snip after sunshine to show microfilariae in fresh preparations
  • High eosinophils at the blood slide/CBC
  • Excision of nodules for adult worms
  • Slit-lamp eye examination for microfilariae in the anterior chamber of eye

Management

Treatment LOC

Case treatment (adult worms)

  • Doxycycline 100 mg twice a day for 6 weeks followed by
  • Ivermectin 150 micrograms/kg single dose 

Mass treatment

  • Ivermectin 150 micrograms/kg once yearly for 10-14 years (see also dose table below)
  • Not recommended in children <5 years, pregnancy, or breast-feeding mothers
  • No food or alcohol should be taken within 2 hours of a dose
 HC3

 

Ivermectin dose based on height

HEIGHT (CM)

DOSE

>158

12 mg

141–158

9 mg

120–140

6 mg

90–119

3 mg

< 90

Do not use

Prevention

  • Vector control
  • Mass chemoprophylaxis

Schistosomiasis (Bilharziasis)

Disease of the large intestine and the urinary tract due to infestation by a Schistosoma blood fluke.

Causes

  • The larvae form (cercariae) of Schistosoma penetrate the skin from contaminated water and they migrate to different parts of the body, usually the urinary tract (Schistosoma haematobium) and the gut (S. mansoni)

Clinical features

S.haematobium (urinary tract)

  • Painless blood stained urine at the end of urination - terminal haematuria
  • Frequent and painful micturition
  • In females: low abdominal pain and abnormal vaginal discharge
  • Late complications: fibrosis of bladder and ureters with increased UTI risks, hydronephrosis, infertility

S.mansoni (gastrointestinal tract)

  • Abdominal pain, frequent stool with blood-stained mucus, hepatomegaly
  • Chronic cases: hepatic fibrosis with cirrhosis and portal hypertension, haematemesis/melena are frequent

Differential diagnosis

  • Cancer of the bladder (S. haematobium)
  • Dysentery (S. mansoni)

Investigations

  • History of staying in an endemic area (exposure to water bodies)
  • Urine examination (for haematobium ova)
  • Stool examination (for mansoni ova)
  • Rectal snip (for mansoni)

Management

Treatment LOC
  • Praziquantel 40 mg/kg single dose
  • Refer patient if they develop obstruction or bleeding
 HC4

 

Prevention

  • Avoid urinating or defecating in or near water
  • Avoid washing or stepping in contaminated water
  • Effective treatment of cases
  • Clear bushes around landing sites