Necator americanus(New World Hookworm)1. The adult parasites are small cylindrical worms, 0.5 - 1.5mmlong.2. Males are usually 7mm-9mm long, while females are about9mm-11mm long3. The posterior end male worm is equipped with acharacteristic copulatory bursa.4. The females have a vulva situated near the center of thebody- slightly anterior.5. Have capsules equipped with cutting plates on the ventralmargins, and within the capsule small dorsal teeth.6. The eggs are bluntly rounded, thin shelled (60 by 40 µm)
• Life span- ( 3-5 years)• Can produce anywhere between 5000 to 10,000eggs per day.• Sexual maturity is reached at the final molt. –Mating occurs in the intestine of the host.• look for and inject sperm.• The male coils around a female with his curvedarea over the female genital pore.(Gubernaculum)• Males use spicules to hold open the genitalopening on the female to allow transfer of sperm
Scanning electron micrograph of the mouth capsuleof Necator americanus, another species of humanhookworm. Presence of two cutting "teeth“.
Copulatory bursa of N. americanus.
Ancylostoma duodenale• grayish white or pinkish with the head slightly bent.• a definitive hook shape at the anterior end.• well developed mouths with two pairs of teeth.• has two ventral plates at the anterior margin of the buccal capsule.• males measure 1cm by 0.5 mm, the females are often longer and stouter.• Special features- males have presence of a prominent posteriorcopulatory bursa.
• Males (8 mm to 11 mm ) long with a copulatory bursa at theposterior end and needlelike spicules which are not fused andhave simple tips• Females are 10 mm to 13 mm long with the vulva located at theposterior end.• Lay 10,000 to 30,000 eggs per day.• Life span is one year.
Scanning electron micrograph of the mouthcapsule of Ancylostoma duodenale. Presence offour "teeth," two on each side.
Ancylostoma duodenale - copulatory bursa and spinesof male
The Morphological Differences between Two speciesof HookwormsCharacteristics A. duodenale N. americanusSize larger smallerShape single curve, looks like C double curves, looks like SMouth 2 pairs of ventral teeth 1pair of ventral cuttingplatesCopulatory Bursa circle in shape oval in shapecaudal spine present noCopulatory spicule 1pair with separate endings 1pair of which unite to forma terminal hookletvulva position post-equatorial pre-equatorial
Copulatory bursa andspines of N. americanusCopulatory bursa of A.duodenale
The Bucal Cavity ofAncylostoma duodenaleThe Bucal Cavity ofNecator americanus
Life cycle of Hookworm
1) Eggs of Necator americanus or Ancylostoma duodenale passed frominfected host via feces.2) The eggs must reach warm and moist soil. Then, the eggs hatched intorhabditiform larvae in 48 hours. The larvae developes into second stageof rhabditiform larvae.3) The rhabditiform larvae molts into filariform larvae which is infectiveform by the 5th – 8th day.4) The filariform larvae penetrate the skin tissue to gain entry to the host.In host, the larvae migrates via lymphatic or circulatory vessel. Then thelarvae carried through heart to the lungs. Then they penetrate into thepulmonary alveoli, cough from the bronchial tree to the pharynx andswallowed to the esophagus.5) The larvae reach the small intestine, they reside and matures into adultform. The adults copulate while they attach at the mucosa.1) Then the eggs passed from the host via feces.
PATHOGENESISHookworm infection caused by nematode parasite:• Necator americanus• Ancylostoma duodenalePathogenesis:a) larvae form- Rhabditiform ( non infective stage)- Filariform ( infective stage)b) presence of buccal capsules (mouth)- N.americanus ( consists of cutting plates)- A. duodenale ( consists of teeth)
PATHOGENESISThe filariform (parasite) attach to the mucosalayer using the sharp teeth / cutting platesthe nematodes suck the mucosal tissuedigestion of the mucosaunderlying blood vessels are exposedthe blood vessels burst and blood releasedfrom the lesions
Clinical manifestation• The list of signs and symptoms mentioned in various sourcesfor Hookworm includes the 24 symptoms listed below:• Symptoms from entry of the worms into the body:– Itchy foot– Ground itch– Pimply rash at worm entry site– Foot pimply rash• Lung symptoms - when the larvae of the worms are temporarily in the lungs fromwhere they later move to the intestines– Wheezing– Coughing• Gastrointestinal symptoms - when the worms infest the bowel or intestines:– Diarrhea– Vague abdominal pain– Intestinal cramps– Abdominal colic– Nausea
Clinical manifestation• Gastrointestinal bleeding– Blood in stool– Black stools– For details see also symptoms of gastrointestinal bleeding• Anemia - from gastrointestinal bleeding and from worms suckingblood; see symptoms of anemia including:– Pallor– Fatigue– Malaise
DIAGNOSISTests that can help diagnose the infection include:• Complete blood count (CBC)• Stool ova and parasites exam
DIAGNOSIS• Diagnosis depends on finding characteristic worm eggs onmicroscopic examination of the stools.• The eggs are oval or elliptical, colorless, measuring 60 µm by40 µm• As the eggs of both Ancylostoma and Necator areindistinguishable, to identify the genus, they must be cultured inthe lab to allow larvae to hatch out.
DIAGNOSIS• Development of DNA-based tools for diagnosis of infection specific identification of hookworm analysis of genetic variability within hookwormpopulations• PCR assays hookworm eggs are often indistinguishable from otherparasitic eggs PCR assays serve as a molecular approach for accuratediagnosis of hookworm in the feces.
Let’s sing along!!HookwormInvolve certain treatmentsThe medications, such as albendazolePyrantel pamoate, revapol, vermicolVermidil, vermin, vermoxAnd there is ,For emergency care,It involves the phase, of larval migrationWheezing and cough, Are managed withinhaled beta agonistsAnd when there is established infectionWe use effective antihelminthicAnd as for the early infectionWe may use the thiabendazoleBut some hookworm infectionsAre asymptomaticThat requires little treatmentAnd also nutritionThese are all for the treatmentThat we need to knowAs long as you rememberAll the medicines
TreatmentParasite-killing medications are usually prescribed such as:• Albendazole• Mebendazole• Pyrantel pamoate• Vermox• Revapol• Vermicol• Vermidil• VerminSymptoms and complications of anemia are treated as theyarise. The doctor will likely recommend increasing theamount of protein in diet.
TreatmentOther medications involved are:– AntihelminticsThis difference permits effective treatment using directedpharmacologic agents in relatively small doses.– AlbendazoleDecreases ATP production in worm, causing energy depletion,immobilization and finally death.– Pyrantel pamoateCauses worm paralysis by a depolarizing neuromuscular blockade.
Treatment for emergency care• Larval migration phase• Early infection• Established infection
Prevention and Control
The most important control measures consist of reducing thecontamination of the soil by: Education and improved sanitation. Controlled disposal of human feces. Treatment of infected persons. Health education with improved sanitary latrines and use offootwears. Avoid pollution of soil with human excreta. Don’t use raw house sewage for fertilizing the edible plants andvegetables. Maintain good nutrition and iron intake without being anemic
A 62-year-old Vietnamese man presented with a sore throat and bloodysputum in September 1997. He had arrived in the United States in 1994 with ahistory of bright red blood passed rectally. In early 1995, examination bybarium enema and flexible sigmoidoscopy was unremarkable. His medicalhistory included six years in a re-education camp in northern Vietnam, wherehe had lived in near-starvation conditions. In May 1996, his blood count wassignificant for an absolute eosinophil level of 559 per mm3 (0.6 3 109 per L). Drycough was noted in June 1997.Physical examination revealed a well-developed, well-nourished patient withminimal pharyngeal erythema. The chest radiograph showed a parenchymalopacity at the base of the right lung. The blood count was unremarkable exceptfor an eosinophil level of 1,870 per mm3 (1.9 3 109 per L). Three stool sampleswere negative for occult blood, but all showed hookworm eggs. The patientwas treated with 10 days of oral penicillin, multivitamins and a single 400-mgdose of albendazole.CASE STUDY
EpidemiologyHookworm infection is acquired when larvae from the soil penetrate the skin andenter the circulation. The spread of this nematode infection is aided by poorsanitary practices in which infected persons defecate in areas where others walkwithout shoes.Clinical PresentationPatients may develop dermatitis when filariform hookworm larvae penetrate theskin. Pulmonary symptoms and signs, such as cough, wheezing and pulmonaryinfiltrates, may occur when the larvae pass through the lungs after entering thecirculation. In addition, patients may complain of gastrointestinal discomfort whenthe larvae are coughed up, swallowed and then reach adult form in the smallintestine, where the worms attach and suck blood.EPIDEMIOLOGY AND CLINICALPRESENTATION
DiagnosisThe diagnosis of hookworm infection is based on the presence of ova in stool.Laboratory findings may also include iron-deficiency anemia and eosinophilia.TreatmentAlbendazole is a synthetic nitroimidazole with broad-spectrum antinematodalactivity plus anticestodal activity and some antiprotozoal activity.A single dose of albendazole is effective treatment for most forms of intestinalhelminthiasis. However, the drug is officially labeled in the United States only forthe treatment of neurocysticercosis and Echinococcus infection. Mebendazole(Vermox), another drug used to treat hookworm, must be given for three days.Patients with iron-deficiency anemia related to hookworm infection also requireiron supplementation. Albendazole and mebendazole should not be used inpregnant women.DIAGNOSIS AND TREATMENT