Hookworm Egg in Saline Preparation: Introduction, Life cycle, Pathogenecity, Lab Diagnosis and Treatment
Egg of Hookworm in Saline Preparation
An egg of hookworm ( N. americanus or A. duodenale) in saline preparation as shown above picture.
Having following features
Shape: oval or elliptical with flattened poles( one pole more often flattened than other), size: 65 X 40 um, color: colorless ( no bile stain), dark brown as stained with iodine. Shell: very thin transparent hyaline shell membrane, appears as a black line and contains: segmented ovum with 4 blastomeres, has a clear space between eggshell and segmented ovum. Float in saturated NaCl. Type: A (fresh stool) : 4 ,8, 16 grey granular cell clear blastomeres. Type: B(a few hours old): a uniform mass of many grey granular cells. Type: C (12-48 hr): the whole egg is filled with larva, embryonated.
Life cycle of Ancylostoma duodenale
Definitive host: Man No intermediate host
Stage 1: Passage of eggs from the infected host
Stage 2: Development in soil
From each egg, a rhabditiform larva (250 um), feeding stage of larvae, hatch out in the soil in 48 hr, molt twice on 3rd and 5th day and develops into filariform larva. Filariform larva ( extremely motile non-feeding stage of larvae,5 00 to 600 um) is an infective stage. The time taken for the development from eggs to filariform larvae is an average of 8 to 10 days.
Stage 3: Entrance into the new host: The larva cast off their sheath and gain entrance to the body by penetrating the skin.
Stage 4: Migration larva enter into lymphatics or small venules, pass into the venous circulation, and are carried into the right heart into pulmonary capillaries where they break through the capillary wall and enter into the alveolar spaces Migrate into bronchi, trachea, and larynx, crawl over the epiglottis to back of pharynx and ultimately swallowed. On the esophagus third molting takes. Period for migration: 10 days
Stage 5: Localization and laying of eggs. Four moltings in the small intestine. Buccal capsule with complete teeth is formed in 3 to 4 weeks and they are sexually matured and fertilized female begins to lay eggs in the feces.
Mode of infection
Filariform larvae penetrate directly through the skin with which they come in contact. Site of entry: skin
Thin skin between toes
Dorsum of the feet
The inner side of the sole
Skin of hands
Pathogenicity of Ancylostoma duodenale
- Ancylostoma dermatitis (ground itch)
- Creeping eruption
- Bronchitis and bronchopneumonia
- Anemia due to – chronic blood loss may be due to parasite sucking blood or hemorrhage from sites of attachment of hookworms and nutritional deficiency
Clinical feature of hookworm anemia
- Gastrointestinal manifestation: Duodenal ulcer, abnormal appetite, analysis of gastric acidity show hypo acidity; IDA cause low secretion of gastric acid, steatorrhea, constipated bowel ( less bowel movement)
- Effects of Anemia: Pallor of the mucous membrane of eyes, lips tongue, and skin Edema of feet and ankle (pitting on pressure), Koilonychia ( spoon nail). The general appearance of the patient is a pale plump individual with a protuberant abdomen and dry lusterless hair.
Laboratory diagnosis of Hookworm
A direct microscopical examination of stool (wet mount preparation), concentration technique may be used. Duodenal intubation may reveal eggs or adult worms. Indirect method- Examination of blood: Eosinophilia, occult blood test: positive, serologic tests for hookworms, including ELISA and immunoblotting (Western blotting). Presence of Charcot-Leyden crystals in the stool.
Treatment
- Treatment of Anemia with Iron first if Hemoglobin (Hb) is below 30 percent.
- Antihelmintic drugs-
- Thiabendazole
- pyrantel pamoate
- Mebendazole
- Albendazole
- Levamisole
- Tetramisole
- Bephenium hydroxynaphthoate
Prophylaxis
- Attack on adult parasite: treatment of carrier and diseased person.
- Attack on larvae: prevention of soil pollution by proper control of sewage disposal.
- Disinfection of feces or soil.
- Personal protection: wearing of boots and gloves.
Further Readings
- Atlas of Medical Helminthology and protozoology -4th edn -P.L. Chiodini, A.H. Moody, D.W. Manser
- Merkell and Voge’s medical parasitology
9th edition. - Parasitology: 12th edition
By K. D. Chatterjee - District laboratory practice in Tropical countries –Part-I.
By Monica Chesbrough. - Isenberg clinical microbiology procedures Handbook
2nd edition. Vol. 2 - Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji
- Atlas of Human Parasitology, Lawrence R Ash, Thomas C. Orihel, 3 rd ed, Publisher ASCP Press, Chicago.
- Molecular Medical Parasitology. Editors: J. Joseph Marr, Timothy W. Nilsen, and Richard W. Komuniecki, Publisher Academic Press, an imprint of Elsevier Science.
- Topley & Wilsons’ Principle of parasitology. Editors: M.T. Parker & amp; L.H. Collier, 8 th ed 1990, Publisher Edward Arnold publication, London.