Ancylostomiasis (hookworm)
Ancylostomiasis is caused by Ancylostoma duodenale or Necator
americanus, it is one of the main causes of anaemia in the tropics and
subtropics.
In the early stage of infection eosinophilia is common, The adult worm is 1
cm long and lives in the duodenum and upper jejunum, Eggs are passed in
the faeces. In warm, moist soil, the larvae develop into filariform infective
stages, they then penetrate human skin and are carried by the blood to the
lungs. After entering the alveoli, they ascend the bronchi, are swallowed and
mature in the small intestine, reaching maturity 4–7 weeks after infection.
Hookworm infection is widespread in the tropics and subtropics. A.
duodenale is endemic in the Far East and Mediterranean while N.
americanus is endemic in West, East and Central Africa, and Central and
South America.
Pathology
The larvae may cause allergic inflammation at the site of entry through the
skin, when infection is heavy, the passage through the lungs may cause
pulmonary eosinophilia.
The worms attach themselves to the mucosa of the small intestine by their
buccal capsule and withdraw blood. The mean daily loss of blood from
one A. duodenale is 0.15 mL and from N. americanus 0.03 mL.
The degree of iron and protein deficiency which develops depends not only
on the load of worms but also on the nutrition of the patient and especially
on the iron stores, in a light infection there may be no anemia.
Clinical features
Dermatitis on the feet (ground itch), may be experienced at the time of
infection.
The passage of the larvae through the lungs in a heavy infection causes a
paroxysmal cough with blood-stained sputum, associated with patchy
pulmonary consolidation. In the small intestine, vomiting and epigastric pain
resembling peptic ulcer disease may occur. Sometimes, frequent loose stools
are passed.
Iron deficiency anemia, protein losing enteropathy and hypoproteinemia
may develop in the undernourished
High-output cardiac failure may result from chronic iron deficiency anemia;
the mental and physical development of children may be retarded. A well-
nourished person with light infection may be asymptomatic.
Investigation
Stool exam for ovum
In heavy infection stool for occult blood is positive and ova will be present
in large numbers.
Management
Mebendazole tab 100 mg twice daily for 3 days, or a single dose of
albendazole (400 mg) is the best choice.
Anaemia and heart failure respond well to oral iron, blood transfusion
should only be used in severe anemia < 4g/dl.
Ascaris lumbricoides (roundworm)
This pale yellow worm is 20–35 cm long. Humans are infected by eating
food contaminated with mature ova. Ascaris larvae hatch in the duodenum,
migrate through the lungs, ascend the bronchial tree, are swallowed and
mature in the small intestine. This tissue migration can provoke both local
and general hypersensitivity reactions, with pneumonitis, eosinophilic
granulomas, bronchial asthma and urticaria.
Clinical features
symptoms range from vague abdominal pain through to malnutrition
(malabsorption). The large size of the adult worm and its tendency to
aggregate and migrate can result in obstructive complications, e.g. intestinal
obstructions, intussusception, volvulus, haemorrhagic infarction and
perforation. Other complications include blockage of the bile or pancreatic
duct and obstruction of the appendix by adult worms
.
Investigations
Stool examination and finding ova. Adult worms are frequently expelled
rectally or orally. Occasionally, the worms are demonstrated
radiographically by a barium examination. There is eosinophilia
Management
mebendazole (100 mg twice daily for 3 days)
albendazole (400 mg) or piperazine 4 gr as a single dose or pyrantel pamoate
(11 mg/kg; maximum 1 g), ivermectin (150– 200 µg/kg). Patients should be
warned that they might expel numerous whole, large worms. Obstruction
due to ascariasis should be treated with nasogastric suction, piperazine and
intravenous fluids.
Prevention
Community chemotherapy programmes have been used to reduce Ascaris
infection. The whole community can be treated every 3 months for several
years. Alternatively, schoolchildren can be targeted; treating them lowers the
prevalence of ascariasis in the community.