Ancylostoma Duodenale Quiz

Ancylostoma duodenale (Hookworm)

• Adult worms live in the small intestine of infected persons, mainly in the jejunum, occasionally in the duodenum, and rarely in the ileum.
• They are relatively stout, cylindrical, pale pink or greyish white, and may appear reddish brown due to ingested blood.

Life Cycle

• Involves only one host (human).
• Infective stage is the third-stage filariform (L3) larva.
• Adult worms attach themselves to the mucous membrane by means of their mouth parts.
• Female worms lay eggs, which are passed out in the feces of infected persons.
• Eggs develop in the soil, and a rhabditiform larva hatches out, molts twice, and becomes the third-stage infective filariform larva.
• A single infective larva develops into a single adult, male or female.

Mode of Infection

• Infection occurs when a person walks barefooted on soil containing the filariform larva, which penetrate the skin and enter the subcutaneous tissue.
• Rarely, infection may take place by the oral route.
• Transmammary and transplacental transmission has been reported for Ancylostoma.

Life Cycle (continued)

• Inside the human body, the larvae are carried through the venous circulation to the right side of the heart and lungs.
• They escape from the pulmonary capillaries into the alveoli, migrate up the respiratory tract to the pharynx, and are swallowed, reaching the small intestine.
• During migration, they undergo a third moult and develop a buccal capsule, which they use to attach themselves to the small intestine and grow into adults.

Necator Americanus

• Adult worms are slightly smaller than A. duodenale.
• Eggs of N. americanus are identical with those of A. duodenale.
• Life cycle is similar to that of A. duodenale.

Pathogenicity and Clinical Features of Hookworm Infection

• Symptoms can be linked to inflammation of the gastrointestinal system stimulated by feeding hookworms.
• Inflammation is accompanied by nausea, abdominal pain, and intermittent diarrhea.
• Progressive anemia (iron-deficiency anemia) and protein deficiency states often occur in prolonged infections.
• Patients with more severe infections may experience vomiting, general fatigue, and dysentery.
• Untreated infections may lead to hemorrhage, edema, and fatal consequences.
• Characteristics of chronic hookworm disease include emaciation, wasting, cardiac failure, abdominal distension, and delayed mental and physical development in children.

Larval Stage

• Hookworm infections begin with larval invasion of the skin, particularly the lower extremities and feet.
• Lesions resemble spider bites and insects, causing intense itching (pruritis) and blistering, known as "ground itch" or "toe itch".
• Migration of larvae through the skin causes lesions called vesicles containing serous fluids.
• Initial areas of lesions appear dry and crusty as the larvae move through the body.
• Passage of larvae through the lungs can cause coughing, chest pain, wheezing, and fever.