Today is our topic of discussion Hookworm disease
Hookworm disease
Definition:
Hook worm infection is defined as any infection caused by Ankylostoma duodenale (AD) and Necator americanus (NA). They may occur as single or mixed infection in same individual.
Predisposing factors:
Hookworm disease is one of the most common parasitic roundworm infections of the intestine. The disease is widespread in developing countries like Bangladesh, where open air defecation and poor sanitation prevails.
Agent factors:
Agent:
Ankylostoma duodenale & Necator americanus
Reservoir of infection:
Man
Infective material:
Faeces containing fertilized eggs & soil contaminated with infective larvae.
Period of infectivity:
Until all fertile females are destroyed and stool are negative.
Life cycle:
- Eggs excreted in human faeces → Undergo development in soil to become embryonated →→ Embryonated egg gives rise to rhabditiform larva and then filariform larva which is infective. It takes about 5-10 days.
- The skin penetrating larva survive in moist soil for upto one month → Enters human body by penetrating skin (commonly feet) → Via lymphatic and blood stream to the lungs →→ Undergo further development & breaks through alveolar walls to migrate into bronchioles → Coughed up through trachea and swallowed.
- Become mature adult (male & female) in intestine in 20-30 days & life span of adult is about 1 and 5 years for AD an NA respectively → Females produce eggs and passed in faeces.
Fig: Life cycle of hookworm
Host factors:
Age and sex:
All ages and sexes are susceptible. Highest incidence between 15-25 years.
Nutrition:
Malnutrition is predisposing factor. bod 2 mag ana
Host parasite balance:
In endemic areas, a balance between host and parasite develops and the load of parasite is low, so the patient does not show signs and symptoms.
Occupation:
Agricultural workers
Environmental factors:
Soil:
Damp, sandy soil is more favourable than clay soil.
Temperature:
Optimum temp. 24-32°C, eggs fails to develop at <13°C and larvae are killed at >45°C.
Oxygen:
Required for growth and development of larva.
Moisture:
Moisture is necessary for survival, dryness is fatal.
Rainfall:
Distribution of rainy days throughout the year is more important. Flood unfavourable.
Shade:
Direct sunlight kills whereas shade protects the larvae.
Human habit:
Determines mode and extent of soil pollution and the mode and extent of contact between infected soil and skin or mouth. These include: indiscriminate defaecation, using same places for defaecation with bare footed, farming practices using untreated sewage, children wading in the infected mud with bare foot and hand.
All these habits are compounded by social factors such as illiteracy, ignorance, and low standard of living.
Mode of transmission:
Penetration of skin (usually feet) by infective larvae and direct ingestion of infective larvae through contaminated fruits and vegetables.
Incubation period:
5 weeks to 9 months
Clinical features: May be asymptomatic.
Usual features are –
1. Iron deficiency anemia and its consequences – Pallor, fatigue etc.
2. Abdominal discomfort, bloating & diarrhoea
3. Blood in the stool (stool occult blood test may be positive)
4. Bloody sputum and cough
5. Itchy rash (‘Ground itch’ at the site of penetration)
6. Loss of appetite, nausea & vomiting
7. In children – Retardation of physical growth and development.
8. In mothers – Increased morbidity, low birth wt. baby, abortion, stillbirth and impaired lactation.
[Three ways for anaemia by hookworm – They suck blood from intestinal mucosal lining through hook in the body end, oozing of blood occurs through the puncture site and they ingest intestinal contents]
Complications:
1. Anemia
2. Severe protein loss with fluid build-up in the tissues.
3. Other nutritional deficiencies
Treatment:
Antihelminthic medication:
Anyone of the following drugs can be taken –
Albendazole:
Single dose: 400 mg all ages above 2 years.
Mebendazole:
500 mg single dose or 100 mg twice daily for 3 days.
Pyrantel pamoate:
10 mg/kg body wt. (max 1g) daily for 3 days.
Levamisole:
50-150 mg (3 mg/kg body wt.) single dose.
Correction of anaemia:
Iron tablet (200 mg) 2/3 times daily (may be coupled with folic acid) for 3 months after Hb level raised to 12 gm/dl.
Control and preventive measures:
1. Sanitary disposal of faeces – Installing sewage disposal system in urban areas and low cost sanitary latrine in rural areas.
2. Anti-helminthic therapy – Periodic case finding and treatment, periodic campaigning helminthic prophylaxis.
3. Anemia correction
4. Awareness through health education and improvement of socioeconomic condition.
See also :