Ascaris lumbricoides | Morfología, Ciclo de vida, Patogenia, Clínica, Diagnóstico, Profilaxis

Introduction to Ascaris Lumbricoides

In this section, the speaker introduces the topic of Ascaris lumbricoides, discussing its classification as a geohelminth and providing insights into its historical background.

Description of Ascaris Lumbricoides

• Ascaris lumbricoides is a geohelminth parasite that requires its eggs to pass through the soil for infectivity. It has been described since ancient times by figures like Aristotle and Hippocrates.

• The parasite affects around 25% to 30% of the global population, with humans serving as its primary host. Its distribution is cosmopolitan, indicating a worldwide presence.

• Unlike many parasites transmitted via fecal-oral route, Ascaris lumbricoides' transmission occurs through environmental exposure rather than direct ingestion of eggs. Factors like poor economic conditions and inadequate hygiene contribute to predisposition for infection.

Morphology and Life Cycle of Ascaris Lumbricoides

This section delves into the morphology of both male and female Ascaris lumbricoides, highlighting their physical characteristics and locations within the human body.

Morphology of Male and Female Parasites

• The female parasite is larger than the male, measuring between 15 to 45 cm in length compared to the male's 15 to 30 cm. Both sexes are typically found in the small intestine.

• Ascaris lumbricoides possesses strong musculature allowing it to resist peristaltic movements in the intestines. When expelled from the body, these parasites appear pink or yellowish-white in color.

Reproductive Anatomy

• The female parasite's reproductive system includes a mouth with three dentate lips leading to an esophagus, followed by genital structures such as oviducts and ovaries towards the posterior end containing intestines and anus.

• In contrast, the male parasite features similar anatomical regions but includes testes surrounded by vas deferens towards its central region and cloaca at its posterior end for copulation with females.

Egg Characteristics and Resistance Forms

This part explores different types of eggs produced by Ascaris lumbricoides along with their distinctive features related to fertility status.

Egg Types and Characteristics

• Two main egg types exist: infertile (unfertilized) and fertile (fertilized). Infertile eggs are elongated while fertile ones are more oval-shaped. Infertile eggs measure approximately 85-90 microns in length by 30-40 microns in width.

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This section discusses the characteristics of certain structures and their differences.

Characteristics of Structures

• The structures have a single, thin membrane, which is the external membrane. They lack an internal membrane or capsule.

• Fertile eggs are more complex, with dimensions ranging from 50 to 65 microns in length and 45 to 50 microns in width. They are ovoid and have a thick membrane known as a capsule.

• Fertile eggs consist of three to four distinct layers: the outer mamillated layer for protection, followed by the external layer (proteic nature), middle layer (glucogenic nature), and inner lipid layer.

• Fertile eggs may develop multiple mamillated layers for resistance.

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This part delves into the life cycle of parasites, starting from adult parasites in humans to environmental interactions.

Parasite Life Cycle

• Adult male and female parasites reside in the human small intestine, primarily but not exclusively. They can also be found throughout the digestive system, respiratory system, and circulatory system.

• In the small intestine, approximately 200,000 eggs are laid before being excreted through feces into the environment. These non-infectious eggs require about two weeks on land at temperatures between 15°C to 35°C to become infectious.

• After becoming infectious larvae (L2), they can be ingested by humans. Once ingested, they travel through various body systems until reaching the lungs where symptoms may manifest.

• The larvae then move back through the respiratory tract towards the digestive system where they mature into adolescent larvae capable of surviving gastric juices before completing their cycle within approximately 60 days.

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The transcript discusses the life cycle of Ascaris, a parasitic worm, detailing its journey through the human body and the stages it goes through to cause infection.

Life Cycle of Ascaris

• Ascaris eggs containing L2 larvae are ingested by humans and hatch in the duodenum.

• Larvae migrate to the liver, then to the heart via circulation, reaching the lungs through pulmonary arteries.

• Larvae can break capillaries in lungs, causing symptoms; they may mature into L4 larvae or regress back to pharynx.

• Pathogenic mechanisms include traumatic (lung damage), mechanical (intestinal obstruction), migratory (affecting various organs), inflammatory, and allergic reactions.

Manifestations of Ascaris Infection

This section explores the clinical manifestations of Ascaris infection, correlating with its pathogenic mechanisms and life cycle stages.

Pathogenic Mechanisms

• Traumatic mechanism: L3 larvae cause lung tissue damage leading to lesions.

• Mechanical mechanism: Adult worms in intestines can obstruct causing issues.

• Migratory mechanism: Worm migration can affect different organs beyond intestines.

• Inflammatory and allergic mechanisms contribute to pneumonia-like symptoms.

Clinical Manifestations

• Divided into larval phase (pulmonary symptoms) and adult phase (intestinal symptoms).

• Larval phase presents as lung lesions causing hemorrhage, congestion, inflammation leading to cough, bronchial sounds, expectoration, fever.

Clinical Presentation of Adult Phase

Focuses on manifestations during the adult phase of Ascaris infection including complications like abscesses and obstructions.

Adult Phase Symptoms

• Can lead to abscess formation or enteritis characterized by diarrhea, anorexia, weight loss.

Complications

Desnutrición Infantil y Manifestaciones de Ascaris Lumbricoides

The discussion covers the impact of Ascaris lumbricoides on child development, highlighting how it can lead to malnutrition and various migration patterns within the body due to factors like erratic movements and ingestion of medications.

Impact on Child Development

• Malnutrition in children can be a manifestation of Ascaris lumbricoides infection.

• Erratic migrations occur when the parasite moves to different organs, such as the biliary tract, leading to complications like cholangitis.

• Complications in the biliary tract can cause symptoms like abdominal pain, jaundice, and fever due to bile duct obstruction.

Complications and Migration Patterns of Ascaris Lumbricoides

Explores how Ascaris lumbricoides can migrate through various organs in the body, causing complications such as hepatic abscesses, pancreatitis, peritonitis, and appendicitis.

Organ Migration and Complications

• Parasite migration to the liver may result in hepatic abscesses or granulomas with symptoms like abdominal pain and fever.

• Migration to the pancreas can lead to acute pancreatitis with severe consequences.

• Migration towards the peritoneal cavity may cause peritonitis characterized by diffuse abdominal pain and rigidity.

Diverse Migratory Routes of Ascaris Lumbricoides

Discusses the varied migratory paths of Ascaris lumbricoides within the human body, affecting regions such as lacrimal ducts, auditory canal, urinary system, and even potentially reaching the nervous system or eyes.

Varied Migratory Routes

• The parasite can migrate to lacrimal ducts causing eye-related issues or reach the urinary system leading to infections.

• Passage into circulation allows for potential lodging in the nervous system triggering convulsions or ocular involvement.

Diagnostic Approaches for Ascariasis

Explores diagnostic methods for ascariasis focusing on clinical evaluation alongside laboratory techniques including direct (macroscopy/microscopy) and indirect (imaging/serology) approaches.

Diagnostic Methods

• Clinical diagnosis is complemented by epidemiological considerations while laboratory diagnosis involves direct (macroscopy/microscopy) and indirect (imaging/serology).