3 Morphology Necator americanus “New World Hookworm” Pair of dorsal and ventral cutting plates surrounding the buccal cavityAlso have subdorsal and subventral teeth near the rear of the buccal cavityMales:7-9 mm longCopulatory Bursa with needle-like spicules forming a distal hookFemales:9-11 mm longVulva located in middle of bodyProduce 5,000-10,000 eggs per day (Life Span = 5 Years!)Eggs: μm by μm, thin shelledKerbe
4 Necator americanusdorsal and ventral cutting plates
5 Morphology Ancylostoma duodenale “Old World Hookworm” Two ventral cutting plates with two large teeth fused at their baseA pair of small teeth are located in the capsule as wellMales:8-11 mm longCopulatory Bursa with needle-like spicules that are NOT fused distallyFemales:10-13 mm longVulva located about 1/3 of the body length from the posterior endProduce 10,000-30,000 eggs per day (Life Span= 1 year)Eggs: μm by μm, thin shelledBrandy
6 Ancylostoma duodenale cutting plates with two large teeth fused
7 Transmission Ancylostoma duodenale Necator americanus Fecal Oral Route Penetration of filariform larvae upon human skinTransplacentally and through mother’s milkNecator americanusKerbe
8 Hosts Definitive Host Paratenic Host Humans (Children more commonly than adults)Paratenic HostA. duodenale can be transmitted through ingestion of undercooked meat (rabbit, pork, beef, lamb)Pigs can serve as a transport host for N. americanusBrandy
9 1. Eggs are passed in the stool and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. 2. The released rhabditiform larvae grow in the feces and/or the soil , and after 5 to 10 days (and two molts)3. they become filariform (third-stage) larvae that are infective . These infective larvae can survive 3 to 4 weeks in favorable environmental conditions.4. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed . The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host . Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years. Some A. duodenale larvae, following penetration of the host skin, can become dormant (in the intestine or muscle). In addition, infection by A. duodenale may probably also occur by the oral and transmammary route. N. americanus, however, requires a transpulmonary migration phase.
10 Other Forms Ancylostoma caninum Ancylostoma braziliense dogs, foxintestinalAncylostoma braziliensecanines, felinesCutaneous larval migransHumans act as accidental hosts for both speciesBrandy
11 Pathogenesis Cutaneous Phase: Pulmonary Phase: Occurs when the juvenile penetrates human skinGround Itch (“Creeping Eruption”)Pulmonary Phase:Occurs when juveniles break out of lung capillaries and into the throatUsually asymptomaticDry coughing or sore throat may occurPneumonitis (Rare)Kerbe
12 Pathogenesis Intestinal Phase: Occurs when worms reach the small intestine and attach themselvesIron deficiency anemia:N. americanus can suck approximately 0.03 L of blood per day (1000 worms)A. duodenale can suck approximately 0.26 L of blood per day (100 worms)Abdominal PainLoss of normal appetiteCognitive ImpairmentsBrandy
13 Diagnosis Eggs or Worms in Feces Must use concentration techniqueDifferentiating between N. americanus & A. duodenale:Use PCR-RFLP methodWhy differentiate?N. americanus has drug sensitivity to Ivermectin, A. duodenale does not have senstitivityKerbe
14 Treatment & Prevention Mebendazole- Drug of choiceRemoves both species of HookwormSingle dose therapy is efficient and cheapPrevention:EducationPersuasion of sanitary disposal of feces (use of latrines)Avoid using nightsoil for fertilizationMass Drug Administration (Distributing Benzimidazole Anthelmintic Drugs)Brandy
15 Public Health ConcernApproximately 22.1 million DALY’s (Daily Adjusted Life Years) have been lost due to Hookworm InfectionResearch:Vaccines currently being clinically tested for targeting:Larval worm stageAdult worm stageKerbe
16 Referencessht_hookworm.htmhttps://health.google.com/health/ref/Creeping+eruptionRoberts, Larry S. and Jr. John Janovy. Foundations of Parisitology. 8th Edition. November 30th, 2008.