Giardiasis Overview and Risk Factors

Giardiasis

• Causative agent: Giardia lamblia, also known as Giardia intestinalis and Giardia duodenalis.
• Risk factors include travel to endemic areas, wilderness travel (like backpacking), contaminated drinking water, and outbreaks in daycare centers.
• Symptoms may be absent in 50% of cases; when present, include abdominal cramps, bloating, flatulence, steatorrhea, and chronic diarrhea potentially causing malabsorption and weight loss.
• Diagnosis typically involves stool antigen tests or stool microscopy.
• Treatment consists of oral rehydration; Tinidazole is preferred for those over 3 years, Nitazoxanide for ages 1-2, and Metronidazole for infants under 12 months.

Helminths

• Helminths, or worms, are prevalent as free-living organisms or parasites, with zoonotic infections being rare in humans.

Hookworms

• Causative agents include Ancylostoma duodenale and Necator americanus.
• Transmission occurs through human fecal contamination of soil.
• Pathophysiology involves larvae penetrating skin, migrating to lungs, and maturing in small intestines where they feed on blood.
• Clinical manifestations progress through four phases: initial itching, transient pneumonitis, gastrointestinal symptoms, and anemia with hypoalbuminemia.
• Diagnosis includes stool microscopy (Kato-Katz technique) and abnormal lab findings such as eosinophilia and iron deficiency anemia.
• Albendazole is the preferred treatment; Mebendazole serves as a secondary option, with iron supplementation for anemia if needed.

Tapeworms

• Four major species causing human infections: Taenia saginata (beef), Taenia solium (pork), Diphyllobothrium latum (fish), and Hymenolepis nana (dwarf).
• Beef tapeworm (Taenia saginata) transmission is linked to undercooked beef, and symptoms are often asymptomatic with potential worm movement felt.
• Pork tapeworm (Taenia solium) risk factors include undercooked pork, particularly in tropical regions, with possible abdominal pain or diarrhea.

Neurocysticercosis

• Caused by ingestion of T. solium eggs, leading to oncosphere release in the intestines, which can cross into the bloodstream.
• Cysticerci can encyst in human tissues including the brain, causing inflammation, scarring, and seizures.

Diagnosis and Treatment of Cestode Infections

• Diagnosis for T. saginata (beef) relies on stool microscopy; T. solium (pork) diagnosis may also involve antibody tests or MRI if neurocysticercosis is suspected.
• Treatment for T. saginata includes Praziquantel, while T. solium can be treated with Albendazole or Praziquantel; anticonvulsants may be necessary for seizures.

Ascariasis

• Caused by Ascaris lumbricoides, characterized as a giant roundworm infection; usually asymptomatic in low worm loads but can cause complications in high loads.
• Symptoms vary from vague abdominal discomfort, intestinal obstruction, to pancreatic or bile duct obstruction.
• Migrating larvae may lead to pneumonitis, presenting with bronchial spasms and Loeffler’s syndrome, which includes cough, wheezing, and eosinophilia.
• Diagnosis can be based on stool exams or clinical observation of worms.
• Treatment options include Albendazole or Mebendazole.

Enterobiasis (Pinworms)

• Causative agent: Enterobius vermicularis; most prevalent in school-aged children.
• Life cycle involves egg hatching in the duodenum and females laying eggs in the perianal region, causing pruritus, especially at night.
• Diagnosis is done through finding adult worms or eggs via techniques like the cellophane tape test.
• Treatment with Albendazole or Mebendazole is recommended; Pyrantel may be used in pregnant patients.

Trichinosis (Trichinellosis)

• Caused by Trichinella spiralis and other Trichinella species.
• Transmission commonly occurs through raw or undercooked pork.
• Ingested larvae, freed by gastric acid, invade intestinal epithelial cells, develop into adults, and release infectious larvae back into the host.