Ascariasis and Hookworm Infections

Nematodes: Overview

• Commonly known as intestinal roundworms.
• They are bilaterally symmetrical and elongate.
• Nematodes are typically tapered at both ends.
• Sexes are commonly separate in most species.
• Size ranges from microscopic to 7 meters.
• They possess a complete digestive tract and a muscular pharynx characterized as triradiate.
• Nematodes have sensory organs at the worm's anterior and posterior ends (amphids and phasmids).

Morphology and Life Cycle

• Nematodes come in three basic forms: egg, larvae, and adult worms.
• Eggs vary in size and shape.
• Developing larvae inside fertilized eggs emerge and mature; typically long and slender.
• Sexes are separate.
• Adult female worms are generally larger than males.
• Adults have developed digestive and reproductive systems.
• Nematode life cycles are similar but organism-specific.
• Infection starts with either ingestion of infected eggs or burrowing through the foot's skin.
• Adult worms concentrate in the intestine for nutrition and reproduction.
• Adult females lay eggs in the intestine.
• Eggs are passed in stool.
• Larvae mature in eggs inside warm, moist soil for 2-4 weeks.

Laboratory Diagnosis

• Diagnosis occurs through the retrieval of eggs, larvae, and occasional adult worms.
• Specimens vary by species; can include cellophane tape preparations around the anus, stool, tissue biopsies, and infected skin ulcers.
• ELISA is available for the diagnosis of select nematode organisms.

Pathogenesis and Clinical Symptoms

• Ultimate infection severity depends on the number of worms present, infection duration, and the host’s overall health.
• Most nematodes cause intestinal infection symptoms like abdominal pain, diarrhea, nausea, vomiting, fever, and eosinophilia.
• Additional symptoms include skin irritation, blister formation, and muscle involvement.

Nematode Classifications

• Intestinal nematodes: Ascaris lumbricoides, Capillaria philippinensis, Enterobius vermicularis, Hookworm, and Strongyloides stercoralis .
• Extra-intestinal nematodes: Trichuris trichiura, Filarial worms, and Trichinella spiralis.

Ascaris lumbricoides Quick Facts

• Common names: Large Intestinal Roundworm, Roundworm of Man.
• It is the most common intestinal helminth infection worldwide.
• Warm climates and areas with poor sanitation are more susceptible.

Ascaris Egg Morphology

• Unfertilized eggs range from 85 to 95 µm by 38 to 45 µm, have varying shapes, an unembryonated amorphous protoplasm, a thin shell, and are usually corticated.
• Fertilized eggs range from 40 to 75 µm by 30 to 50 µm, are rounder, chitin-thick shell, with an undeveloped unicellular embryo, and can be corticated or decorticated.

Morphology of Adult Ascaris

• Adult female worms are 22-35 cm long.
• Adult male worms are up to 30 cm long.
• Both female and male worms are creamy-white pink with pencil-lead thickness.
• Males possess prominent incurved tails.

Ascaris lumbricoides Life Cycle

• Adult worms reside in the small intestine lumen; females may produce ~200,000 eggs per day.
• Unfertilized eggs are not infective.
• Larvae develop infectivity in fertile eggs after 18 days-several weeks.
• Infective eggs are swallowed.
• Larvae hatch, invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs.
• Larvae mature further in lungs (10-14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed.
• In the small intestine, they develop into adult worms.

Pathology of Ascaris lumbricoides

• A worm can migrate to the bile duct and liver, damaging the tissue.
• The worm’s body is flexible, so it occasionally perforates the intestine, causing peritonitis with secondary bacterial infection.
• Adult worms depend on constant motion to stay in position w/in bowel lumen; do not attach to the intestinal mucosa.
• Worms migrating to the lungs can cause pneumonitis resembling an asthmatic attack.
• Migration may occur due to fever, non-ascariasis drugs, and some anesthetics.
• Pulmonary issues relate to the hypersensitivity caused from previous infections and exposure intensity, and may involve eosinophilia and O2 desaturation.
• A tangled bolus of worms in the intestines may cause obstruction, perforation, and occlusion of the appendix.

Geographic Distribution and Epidemiology of Ascaris lumbricoides

• Infection rates highest in tropical and subtropical regions with inadequate sanitation.
• The infection is rare to absent in developed countries, but may arise sporadically in rural, impoverished regions.

Diagnosis, Treatment, and Prevention of Ascaris lumbricoides

• Stool samples recover the eggs.
• Adult worms may be recovered in several specimen types, varying by infection severity.
• Adult worms can be present in stool, be vomited, or removed from external nares.
• ELISA is also available.
• Treatment: several medications are available.
• Prevention: avoid using human feces as fertilizer and practice proper sanitation and personal hygiene.

Hookworm: Overview

• Ancylostoma of the Old World and New World Hookworm (Necator americanus) are common Hookworm species.
• Necator is primarily found in North and South America and also exists in China, India and Africa.
• Ancylostoma is a parasite of the Old World, found in Europe, China, Africa, South America and the Caribbean.
• Nearly 1/4 of the world population is infected with hookworm.
• Higher frequency occurs where the inhabitants practice poor sanitation.
• Mixed infections involving any combo of hookworm, Trichuris, and Ascaris are possible, because all organisms need the same soil conditions.

Morphology of Hookworm

• Eggs have transparent shells and range from 60-75 µm (Necator) or 55-60 µm (Ancylostoma) in length, and 35-40µm in width.
• Larvae have long buccal cavities and small genital primodium 270 µm x 15µm when hatched and 540-700 µm long by day 5.
• Filariform larvae have short esophaguses and pointed tails.
• Adult hookworms are grayish-white to pink with thick cuticles and conspicuous bends/hooks.
• Female adults range from 9-12 mm long and 0.25-0.50 mm wide.
• Male adults range from 5-10 mm long by 0.2-0.4 mm wide with a prominent posterior copulatory bursa.
• Necator has cutting plates, while Ancylostoma has actual teeth in its buccal capsule.

Hookworm Life Cycle

• Eggs are passed in the stool of an infected person.
• Larvae hatch in 1–2 days and live freely in contaminated soil.
• Released rhabditiform larvae grow in the feces and/or the soil.
• After 5–10 days (and two molts), they become filariform (infective third-stage) larvae.
• Filariform larvae survive 3–4 weeks in favorable environmental conditions.
• They penetrate human skin, are carried through the blood vessels to heart & lungs.
• They penetrate pulmonary alveoli, ascend the bronchial tree to pharynx, and are swallowed.
• Larval maturation occurs in the small intestine (jejunum).
• Mature adults live in jejunum where they attach to the intestinal wall and ingest blood.
• Most worms are eliminated in 1–2 years, but longevity may reach several years
• Ancylostoma larvae can become dormant in tissues and re-enter the small intestine.

Pathology and Diagnosis of Hookworm Infections

• Hookworm life cycles are initiated when the filariform larva penetrates the skin.
• Egg laying is initiated 4-8 weeks post-exposure & may persist for 5 years.
• Rhabditiform larvae develop into filariform w/in 2 weeks using soil.
• Hookworms suck blood from injured intestinal tissue with mouthparts designed for such.
• A. duodenale has chitinous teeth. _ N. americanus has shearing chitinous plates.
• Diagnosis occurs primarily recovery after the recovery of eggs in stool samples.
• Larvae may mature and hatch from eggs in stool left at room temperature without additives
• Recovery & examination of the buccal capsule is necessary to determine the specific hookworm organism.
• Labs offer reverse enzyme immunoassay for specific IgE.

Hookworm: Treatment and Prevention

• Drugs of choice: mebendazole or pyrantel pamoate.
• Asymptomatic infections: iron replacement and/or other dietary therapy (proteins, iron, vitamins).
• Prevention is similar that of Ascaris.

Strongyloides stercoralis Overview

• Common name: Threadworm.
• Geographic distribution: predominantly in the tropics and subtropics.

Strongyloides stercoralis Morphology

• Eggs are generally 48 by 35 µm with well-developed embryos.
• Rhabditiform larvae range around 220 by 15 µm and possesses a short buccal cavity.
• Filariform larvae are around 690 µm.
• The female adults are around 2 by 0.4 mm with striated cuticles, short buccal cavities, and esophagus.

Strongyloides stercoralis Life Cycle

• In contaminated soil, filariform larvae penetrate human skin and migrate to small intestine.
• The larvae is thought to migrate via the bloodstream and lymphatics to the lungs.
• In the small intestine, larvae molt twice and become adult female worms.
• The female live submucosally of the small intestine, and produce eggs via parthenogenesis, and then yield rhabditiform larvae.
• Rhabditiform either pass in the stool or cause autoinfection.
• Rhabditiform larvae passed in stool can also directly transform into infective filariform larvae.
• Free-living rhabditiform larvae outside the host develop into free-living adult males and females who mate and produce the cycle again.

Strongyloides stercoralis Routes of Infection

• Direct: skin-penetrating larvae enters the circulation and follows the pulmonary course.
  • Adults develop in the small intestine.
  • Adult females burrow into the mucosa of the duodenum and reproduce through parthenogenesis. -Each female produces about one dozen eggs daily that hatch in the mucosa and release rhabditiform larvae into the bowel lumen .
  • Rhabditiform larvae are distinguished from hookworms by short buccal capsules and large genital primodium.
• Indirect: Rhabditiform transform in the soil and transform into the filariform. Several generations repeat cycle.
• Autoinfection
  • Rhabditiform transforms into filariform inside a gut.

Strongyloides stercoralis: Lab Diagnosis, Treatment, and Prevention

• Diagnostics may be indistinguishable from those of hookworm.
• Zinc sulfate is used for stool concentration.
• Treatment: thiabendazole
• Prevention: same as hookworm.

Trichuris trichiuria Overview

• Also called whipworm.
• Incidence of occurrence is the same as ascaris.
• It is the second most common intestinal worm aside from ascaris.
• Typically occurs in moist, warm, tropical region like Asia, Central/South America, Africa, and the Caribbean Islands.

Trichuris trichiura Morphology

• Flesh/pink slender worms.
• Females: 3.5 to 5.5 cm.
• Males: 3.0 to 3.5 cm (males are smaller than females).
• Anterior 3/5 of the worm is a fine, hair-like structure that forms the esophagus is characteristically embedded in glandular cells called stichocytes.
• Posterior 2/5 of the worm contain the intestine and reproductive organs.
• At the tail end, females are straight/blunt, and males are usually curved at 360°.
• Eggs are barrel shaped with a thick, smooth brown egg shell and tow transparent plugs protruding from both poles; measures 50 to 54 microns by 22 to 23 microns.

Trichuris trichiura Life Cycle

• In the cecum, whipworms copulate.
• Eggs are deposited in the stool in unsegmented form and require favorable environmental conditions.
• In 2-3 weeks, eggs become infective with a larval stage.
• Adult whipworms inhabit the large intestine and are deeply inserted, which makes to harder to expel than Ascaris.
• Once swallowed, the infective embryonated eggs hatch to release the larva.
• These then undergo four larval stages to mature and become an adult.
• Note: Does not have migration phases, but it requires two to three months to develop from eggs/larva until seen in stool of infected persons.
• Each female whipworm can produce ~7,000-10,000 eggs/day, and 60 million eggs over an average life span (2 years).

Trichuris trichiura Pathology and Clinical Manifestations

• Light infections are typically asymptomatic.
• Symptoms are due to worms attachment, so it is related to the intensity of the infection.
• Symptoms Include:* diarrhea due to chronic impairmen, hypoalbuminemia, iron deficiencies anemia due to ulceration of colon with heavy worm, prolapse of anus or rectum, and appendicitis.*

Trichuris trichiura: Epidemiology, Diagnosis, and Management

-A prevalence of 80-90% exists that runs almost parallel to Ascaris.
- Lighter infections often occur, with less resistance.
- Diagnosis through Direct Fecal Smear or Cellophane thick smear method.
-Albenzadole/Mebendazole and Oxantel-Pyrantel are used for treatments.

Enterobius vermicularis Nematode: Overview

• Also called Seatworm, Pinworm, or Society Worm.
• Affecting 208 million population.
• Habitat: Cecum, appendix, adjacent ascending colon, and ileum.

Morphology of Enterobius vermicularis

• Shape: spindle-shaped, and whitish/brownish colour.
• Size is very small.
  • Female: ~8-13x0.3-0.5mm.
  • Male: ~2-5x0.1-0.2mm.
• Females have long, sharp posterior ends, while males are ventrally curved with single copulatory Spicule.
• Anterior End: Contains a pair of lateral "wings" of cephalic Alae.

Enterobius vermicularis life cycle

• Eggs, carrying Enterobius vermicularis are swallowed and travel into the small intestines.
• Following egg hatching in small intestines third stage larva can hatch in the duodena.
• Male/Female then can mature as adults into lumen around final destination the large intestines.
• After they finally mate, Gravid females take course to migrate down to the anus to lay eggs on perianal folds.
• In under 6 hours the eggs become fully matured and can re-enter the cycle by being ingested by human touch into the upper digestive organs.

Enrerobius vermicularis Pathology/Symptoms

• Attachment : Leads To development of small wounds and ulcers around.
• Egg Deposition- Intense Itchiness around perianal.
• Migrating Worms: Can lead to vulvovaginitis and infection.

Trichinella spiralis Overview

• AKA "Pork Worm" _ Diseases associated: Frichinosis, Frichiniasis, and Trichmelliasis.

Morphology, Trichinella spiralis

- Small worm
-Threaded like
- Size 22x.3-.4mm

• Contains distinct anterior and posterior portions. Has small.
• The Larvae Has Spear like Burrowing tips and averages 80-120h

Trichinella spiralis Life Cycle

-When eat Viable Meat.
-Larvae Enter Duodenum-

• Enter Small to become Male or Female;
• Eggs begin forming in Uterus of Female.
• Migrate to different blood streams in various systems to lodge in and can turn into cysts.

Trichinella spiralis Pathology & Symptoms

• Divided into three Stages:
  • Incubation or Initial Stage. -Acute -Chronic encased.
• Symptoms of Diarrhea, Fever and Abdominal Crams
  • Swelling of lower regions.
  • Inability to coordinate muscle movements.

Diagnostics , managements and prevention.

- Clinical Diagnosis of eating infected Meat at any point or in the blood as a well.
- Biopsy, Xeno and Bachman test.
- No set form of treatments, use to thiabendazole and steroid applications.
- Avoid meat and garbage; maintain deep freezing of all materials especially pork.

Capilaria Philipinensis Overview

• Pudoc Worm causes disease through malnutrition.
• First Recognizable cases Philippines 1962.
• From Baraccaira Illocos.
• Prevalance to Illocos Norte and Sur, Thailand/Japan/Taiwan.

Capilaria Philipinensis details

 -Adult Form is very thin as eggs are yellow.

• Typical -8/10 embryos are present.
• Atypical -Over 40 Present.

Diagnostic stage

• Adults undergo development at wall. -Eggs Pass through and are produced.
• Larvae will take host and go up digestive tract.
  • Larvae Mature in digestive wall and reenter.
• Pathology.
  • As adults mature, the larvae make their way to jejunum.
  • The patient can experience malnutrition and infection.

Capillaria Diagnosis and Managment:

• Finding eggs.
• Can be difficult in stool.
• Epidemiology First Seen in 1968, 1976. Mebendazole and Albenazole
• Preventation through cooking proper fresh fish.

D. medinensis = Guinea Worm Disease Highlights:

• Transmission through MOT: Consumption of contaminated waters.

• Found in certain parts of Africa and Asia.

• Larvae in water source consumed by the vector Cyclops while human consumption happens.

Life Cycle:

- Laravae are consumed within the gut of intermediate host.

• Moves thru the small intestine, as female is fertile she goes under the skin for about a year.
• As symptoms begin, you often need fluids to expel that will eventually push larvae out of any ulcer it is located by.

Morphology:

  - Has been known to cause issues, and 3 milli embryos can exist in the human hosts..

Explore ascariasis, caused by Ascaris lumbricoides, including migration to the lungs and treatment options. Learn about Necator americanus and Ancylostoma duodenale hookworms, their identification, and preventive measures. Understand the complications and pulmonary involvement associated with these parasitic infections.