PharmD Program: Nematodes Lecture

Study Notes

Cylindrical, elongated, smooth, and unsegmented body with a complete digestive system
Body is tapered to a pointed posterior end and a rounded anterior end
No circulatory or respiratory systems
All are unisexual, with females usually larger than males

Classified into two main categories according to their primary location:
- Intestinal nematodes
- Tissue nematodes

Disease: Ascariasis
Habitat: Small intestine of man
Definite host (DH): Man
Infective stage (IS): Embryonated egg (ingestion)
Diagnostic stage (DS): Worm or egg
Worm reaches up to 35 cm in length, the largest nematode of humans
Worldwide distribution, with highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation

Pulmonary phase:
- Larval migration through lungs causes Loeffler's syndrome
- Characterized by fever, asthmatic cough, dyspnea, wheezes, and blood-tinged sputum
Intestinal phase:
- Light infection: Asymptomatic
- Heavy infection: Nausea, vomiting, diarrhea, colic, and weight loss
- Allergic reaction: Bronchial asthma and urticaria

Intestinal obstruction due to worm mass
Adult worms have the tendency of wandering habit if irritated by fever, drugs, or anesthetics
Wandering single worm can cause:
- Migration up and down to be expelled from mouth or anus
- Passage through intestinal orifices (e.g., bile duct, pancreatic duct, appendix)
- Perforation of the alimentary canal, leading to peritonitis

Clinical diagnosis: Non-specific symptoms
Laboratory diagnosis:
- Stool examination for egg (fertilized and unfertilized)
- Sputum examination: In pulmonary phase for larvae
- Blood examination: Eosinophilia

Treatment of infected population
Environmental sanitation (clean water supply and safe sewage disposal)
Health education (hand washing before meals and washing raw vegetables)
Avoid using human excreta as fertilizers before exposure to sunlight or raising temperature to 51°C
Fly control

Ingestion or inhalation of larvated egg
Autoinfection (external) occurs when the host scratches the perianal area and transfers the eggs from the fingers to the mouth
Retroinfection (internal autoinfection)
Transmission between hosts (heteroinfection) occurs when another human handles or touches contaminated items

Irritation and pruritis of anus, especially at night
Nervous irritability, restlessness, and insomnia
Intestinal pain (inflammation of intestinal mucosa)
Appendicitis (worms present in the appendix)
In female patients: the worm may reach the urether, urinary bladder, vagina, and cause urethritis, nocturnal enuresis, and vaginitis

Oral: Flubendazole (Fluvermal) or mebendazole (Vermox)
Topical: 1% white precipitate mercury ointment at night on the anus region to kill the females and relieve itching and avoid secondary bacterial infection

Skin invasion: Itchy papule, edema, and erythema (ground itch)
Pulmonary migration: Loeffler's syndrome
Intestinal attachment: Nausea, vomiting, diarrhea, epigastric pain, and bloody stool (due to laceration of intestinal mucosa)
Polyphagia, puffy face, swollen feet, and general edema (due to malabsorption of protein and hypoproteinemia)
Mental and physical growth retardation in children due to anemia
Hookworm anemia: Due to sucking of blood by the worm and bleeding at the site of attachment