Malaria and Entamoeba histolytica Quiz

Microbiology & Parasitology RNB 10102

• Topic: Parasites - Internal
• Learning Outcomes:
  • Students should be able to discuss the morphology of protozoan infections in humans, such as Entamoeba histolytica, Trichomonas, and Malaria.
  • Students should be able to describe the life cycle of these protozoan parasites.
  • Students should be able to describe the methods of transmission for these parasites (Entamoeba histolytica, Trichomonas, and Malaria).
  • Students should describe the clinical manifestations of Entamoeba histolytica, Trichomonas, and Malaria.
  • Students should state the medical management of patients with these diseases and the potential side effects of medications.
  • Students should describe the preventive measures for these infections.
  • Students should discuss complications of these infections.

Common Protozoa

• Entamoeba histolytica - Amoebiasis
• Trichomonas
• Malaria parasite
• Toxoplasma gondii

Entamoeba histolytica

• Important human pathogen causing amebic dysentery and hepatic amebiasis.
• Human infection with amebae is known as amebiasis.
• Seen more in tropical countries with poor sanitation conditions.
• Approximately 1/10th of the world population is infected with E. histolytica.
• Causes 40,000 - 100,000 deaths worldwide.
• Trophozoites reside in the mucosa and submucosa of the large intestine.
• Exists in three morphological forms:
  • Trophozoite (active)
  • Precyst (intermediate)
  • Cystic (inactive)
• Morphology of Trophozoite: Measures 10-60 µm (average 15-30 μm) with a single nucleus (4-6 μm). Moves by pseudopodia. Division by binary fission once in about 8 hours.
• Morphology of Precystic stage: Colourless, round or oval, measuring 10-20 µm in diameter, endoplasm free of red blood cells and other food particles, no change in nucleus.
• Morphology of Cyst: Size varies from 10-15 μm, surrounded by a thick chitinous wall making it resistant to gastric acid and adverse environmental conditions. May contain 1-4 nuclei. Mature cyst is the infective form of the parasite.
• Life cycle:
  • Cysts and trophozoites are passed in feces.
  • Cysts are found in formed stool, trophozoites are found in diarrheal stool.
  • Infection occurs by ingestion of mature cysts in fecally contaminated food, water, or hands.
  • Excystation occurs in the small intestine, releasing trophozoites that migrate to the large intestine.
• Transmission and pathogenesis: Ingestion of food or water contaminated with E. histolytica fecal matter, flies on food, soiled hands of infected food handlers, oral-anal sexual contact. Severe infections in children, pregnant mothers, and the elderly
• Clinical Features:
  • Amoebic dysentery: abdominal pain, fever and chills, nausea and vomiting, watery diarrhea with blood, mucus, or pus, painful stools, fatigue, intermittent constipation.
  • Hepatic amoebiasis: onset sudden or gradual, fever and pain in the right hypochondrium, pain and tenderness, chills, rigor, sweating, fever intermittent or absent.
• Complications: Liver abscess, brain abscess, intestinal bleeding, intestinal perforation leading to peritonitis, appendicitis.
• Laboratory diagnosis: stool examination to detect trophozoites or cysts. Serological testing (IHA, ELISA, IFA) for extraintestinal infections as needed. Radiological examinations (ultrasonography, CT scans) are used to confirm involvement of other tissues. Culture of stool and aspirated tissue (if needed) may be necessary.
• Treatment: Metronidazole (750 mg) thrice daily for 5-10 days. Severe cases may require IV treatment and different antibiotics, such as Tinidazole or Paromomycin.
• Preventive measures: Personal hygiene, frequent hand washing, avoiding eating raw food, avoiding eating raw vegetables or fruits that aren't properly washed or peeled, drinking only properly boiled or filtered water, proper sewage disposal systems, and treatment of carriers.

Trichomonas Vaginalis

• Three main species infecting humans: Trichomonas vaginalis, Trichomonas tenax, Trichomonas hominis.
• Morphology: Trophozoite is 8-23 micrometers in length and 5-12 micrometers in width. Rounded anterior end and tapered posterior end. Resides on the mucus membrane of vagina and feeds on bacteria and white blood cells; prevalent in prostate glands and urethral epithelium. Multiplication by binary fission
• Transmission: Typically transmitted through sexual contact.
• Clinical manifestation: infected women may be asymptomatic, or experience burning, itching, and irritation of the vagina plus a copious foul-smelling, yellowish discharge. Red lesions on vaginal mucosa. Infected men are often asymptomatic or have urethritis, tenderness, and swelling of the prostate.
• Treatment: Metronidazole (Flagyl) 200 mg three times a day for one week; treatment of sexual partners recommended.
• Prevention: Avoidance of unprotected sexual contact, prompt treatment of symptomatic and asymptomatic individuals.

Malaria

• A serious tropical disease spread by mosquitoes.

• Can be fatal if not diagnosed and treated promptly.

• Parasite belongs to the Plasmodium genus.

• Aetiological agents: Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale.

• Life cycle: Asexual development (schizogony) in humans; Sexual development (sporogony) in mosquitoes.

• The mosquito (definitive host) transmits the parasite to humans (intermediate host) via the bite of an infected female Anopheles mosquito. -Infective sporozoites infect liver cells, mature into schizonts, which rupture, releasing merozoites into red blood cells (RBC).

• Infection cycle:

  • Cycle in men (schizogony cycle)
    • Malaria infected female Anopheles mosquito to the human host
    • Infective sporozoites infect liver cells and mature into schizonts
    • Schizonts rupture, releasing merozoites that enter RBC -Hypnozoites (in some species) can persist in the liver, causing relapses.
  • Cycle in men (erythrocytic schizogony)
    • RBC stage. The parasites undergo various stages (ring stage, trophozoite stage, schizont stage) in the RBC. The ring stage trophozoites mature into schizonts, rupturing the cell and releasing merozoites to infect other RBC.
    • Blood stage parasites are responsible for the clinical manifestations.
    • Some merozoites become sexual forms (gametocytes) and differentiate into male (microgametocytes) or female (macrogametocytes) gametes.
  • Cycle in mosquito (sporogonic cycle)
    • Gametocytes ingested by Anopheles during blood meal
    • Gametocytes, male and female, unite and form a zygote
    • Zygote turns into ookinetes
    • Ookinetes invade the midgut wall, developing into oocysts
    • Oocysts release sporozoites that migrate to salivary glands.
    • Sporozoites are inoculated in a new human host, initiating another malaria life cycle.

• Vector mosquito species: Only the female Anopheles mosquito.

• Incubation period: P. falciparum: 8-20 days; P. vivax: 12-15 days; P. ovale: 14 days; P. malariae: 24 days

• Clinical manifestation:

  • Primary features: cold stage (shivering, cold, pale skin), hot stage (high fever, headache, palpitations, flushed), sweating stage (profuse sweating, exhaustion). Complicated malaria may include hyperpyrexia, severe anemia, impaired consciousness, deep breathing, respiratory distress, failure to feed, pulmonary edema, renal dysfunction, hypoglycemia, blackwater fever.

• Complications: Severe anemia, cerebral malaria, hyperreactive malarial splenomegaly, hypoglycemia, renal failure. Non-falciparum malaria complications include splenic rupture, hepatic impairment, thrombocytopenia, severe anemia.

  • P. falciparum: high fever, bloody urine, massive hemolysis, brain damage (RBC clumping), blackwater fever, severe renal failure, sudden life-threatening respiratory distress syndrome.

• Diagnosis: Thick and thin Giemsa-stained blood smears. Identifying presence of plasmodium species. Thin films for identification thick smear for detection of light parasites.

• Treatment: Chloroquine (uncomplicated), IV Artesunate (severe Plasmodium falciparum) or IV quinine plus oral doxycycline (severe P. falciparum alternatives)

  • Prophylactic therapy: Chloroquine (500 mg base PO, 1-2 weeks before travel; continue 4 weeks after). Children: 5 mg (base)/kg P.O. weekly. Initial doses may be higher for those exposed to malaria.

• Contraindications: Hypersensitivity to drug, retinal and visual field changes, porphyria.

• Adverse effects: headache, vomiting, confusion, skin rash, retinal injury, (chloroquine); neurological disorders, cardiovascular effects, and gastrointestinal issues as needed.

• Prevention & Control: mosquito control, environmental hygiene, personal protective measures, and prophylactic treatment).

Toxoplasma gondii

• Protozoan parasite, infecting warm-blooded animals, including humans
• Causes toxoplasmosis.
• Definitive hosts: Cats and their relatives.
• Life cycle: Unsporulated oocysts are shed in the cat's feces, sporulate, becoming infective within 1-5 days. Intermediate hosts become infected after ingesting contaminated soil, water, or plant material. Oocysts transform into tachyzoites, localizing in neural and muscle tissue, and developing into tissue cysts (bradyzoites).
• Transmission: Eating undercooked meat of animals harboring tissue cysts, consuming food or water contaminated with cat feces, blood transfusions or organ transplantations.
• Treatment: Combination of pyrimethamine and sulfadiazine; Alternative medications such as spiramycin, clindamycin, trimethoprim sulfamethoxazole
• Prevention & Control: Freezing meat for a few days at sub-zero temperatures; peeling or thoroughly washing fruits and vegetables, avoiding raw or undercooked seafood, avoiding unpasteurized goat's milk, washing cutting boards and utensils when preparing food or contact with soil, teaching children about hand washing.

Helminths

• Learning Outcomes:
  • Identify clinically significant intestinal nematodes;
  • Describe and compare life cycles of intestinal nematodes;
  • Differentiate between flatworms and roundworms, and between flukes and tapeworms;
  • Identify some common worms;
  • Recognize common features of each worm
• Intestinal Nematodes: Enterobius vermicularis; Ascaris lumbricoides; Trichuris trichuria; Necator americanus/Ancylostoma duodenale; Strongyloides stercoralis.

Enterobius vermicularis (Pinworm)

• Common name: Pinworm, seatworm
• Morphology: Small, white, spindle-shaped worms. Male - 2-4 mm; Female - 8-12 mm, cervical alae (wing-like expansions), laying eggs with thousands of eggs.
• Characteristic eggs: Planoconvex (D-shaped), 50-60 µm in size, colorless, contain tadpole-like larvae, float in saturated salt solution
• Life cycle: Eggs deposited on perineal skin (nocturnal). Ingestion of embryonated eggs, leading to maturation into adult worms in the intestine (30 days).
• Mode of transmission: most common = anus-finger-mouth route, including autoinfection. Also inhalation of airborne eggs, ingestion of eggs in food/water, retrograde infection from perianal region, eggs on clothes, bed linen, or utensils
• Clinical manifestation: Perineal itching, eczema, nocturnal enuresis, appendicitis, abdominal pain, nausea, vomiting, loss of sleep, irritability, vulval irritation in girls.
• Diagnosis: cellophane / Scotch tape test.
• Treatment: Mebendazole (for adults/children ≥2 yrs) 100 mg once daily for one day.
• Prevention: Good hand hygiene, washing hands frequently, keeping nails short, teaching children about hand hygiene. Daily bathing, changing underclothes, avoiding contamination of water, careful washing of clothing, repeated treatment in 2 weeks.

Ascaris lumbricoides (Roundworm)

• Common name Roundworm, large intestinal worm
• Habitat Lives in the lumen of the small intestine, jejunum.
• Morphology Adult roundworms (cylindrical, tapering ends). Female (20-35 cm x 3-6 mm); Male (12-30 cm x 2-4 mm)
• Characteristic eggs Fertilized eggs (60-74 μm x 40-50 μm): Always bile stained, surrounded by a thick coat with prominences (mammillations), contains a large unsegmented ovum; floats in saturated salt solution. Unfertilized eggs (80 μm x 55 μm): Narrower, oval, thinner shell, bile-stained, contain small atrophied ovum, fails to float in salt solution.
• Life cycle: Eggs ingested, hatching in the small intestine, larvae penetrate the intestinal wall, enter the portal circulation, travel to the lungs, break out into the alveoli, migrate up the bronchi, swallowed; mature into adult worms in the intestine; lifespan of an adult is 1 yr.
• Transmission and pathogenesis: Occurs worldwide, transmitted through contaminated food, water, and soil. Contamination by the fecal-oral route.
• Clinical manifestation:
  • Hindering development in children
  • Fever, abdominal pain, urticaria
  • Nausea, vomiting, diarrhea, pneumonitis
  • Acute intestinal obstruction
  • Malnutrition
• Diagnosis: Blood tests to detect eosinophilia, stool specimen examination, X-rays, ultrasounds
• Treatment: Mebendazole, Albendazole, Ivermectin for 1 - 3 days; side effects include mild abdominal pain or diarrhea.
• Prevention: Hand washing, boiling or filtering water, testing food preparation sites, avoiding bathing in unsanitary areas, peeling or cooking vegetables and fruits, avoiding the use of human feces for fertilizer

Ancylostoma duodenale and Necator americanus (Hookworm)

• Common name: Old hookworm (Ancylostoma duodenale), New hookworm (Necator americanus)
• Habitat Adult worms live in the small intestine, usually in the jejunum, sometimes in the duodenum.
• Morphology: Female hookworms (1.25 cm); Male hookworms (0.8 cm)
• Life Cycle:
  • Eggs passed in feces and deposited in soil.
  • Larvae develop in soil and penetrate the skin causing "ground itch".
  • Larvae migrate to lungs via blood stream, coughed up, and swallowed, mature in the small intestine, and begin feeding.
• Types of hookworm disease:
  • Classic hookworm disease: Gastrointestinal infection, causing chronic blood loss leading to iron-deficiency anemia and protein malnutrition.
  • Cutaneous larva migrans: Infection limited to the skin, often caused by Ancylostoma braziliense with definitive hosts including dogs and cats.
  • Eosinophilic enteritis: GI infection with abdominal pain, no blood loss, caused by Ancylostoma caninum.
• Clinical manifestation:
  • Abdominal pain, diarrhea
  • Loss of appetite, weight loss
  • Fatigue, anemia
  • Severe infections: blood loss, iron deficiency anemia, protein loss, and malnutrition.
• Diagnosis: Examination of stool samples for eggs, blood tests for anemia and nutritional deficiencies.
• Treatment: Albendazole or Mebendazole, iron supplements as necessary.
• Prevention: Reduce soil contact, wear shoes, use barriers (e.g., towels) while seated on the ground. Treat dogs and cats for hookworm.

Trichuris trichuria (Whipworm)

• Common name: Whipworm
• Habitat: Lives in the large intestine, particularly in the cecum.
• Morphology: Adult whipworms (30-50 mm): Male is coiled; female is larger. Eggs are bile-stained, oval or barrel-shaped (45-55 μm in length and 20-23 μm in diameter).
• Life cycle: Embryonated eggs in contaminated soil are ingested. Development takes ~2 weeks in the soil; embryonated eggs containing the first stage larvae are ingested from contaminated hard clay soil. Development occurs in the caecum and duodenum. Takes ~3 months for the adult worms to start laying eggs.
• Transmission: Ingestion of embryonated eggs in contaminated food or water, or directly from soil.
• Clinical manifestation: Asymptomatic, nausea, diarrhea, abdominal pain, weight loss, and blood loss.
• Diagnosis: Stool examination.
• Treatment: Mebendazole.
• Prevention: Good hand hygiene, avoidance of contaminated food or water, avoiding using human feces as fertilizer.

Strongyloides stercoralis (Threadworm)

• Common name: Also known as a threadworm.

• Morphology Adult female threadworm (2-3 mm) with short buccal cavity and long thin oesophagus. Eggs: Thin-walled, transparent, and oval, containing larvae ready to hatch - rhabditiform larva (diagnostic stage) most commonly seen in stool specimen - third stage - filariform larvae (highly infectious).

• Life Cycle: Soil-dwelling infective larvae penetrate skin, enter the bloodstream and migrate to the lungs, coughed up, swallowed, maturing into adult worms in the intestines (~2 weeks).

• Transmission: Penetrating the skin when in contact with soil containing infective larvae.

• Clinical manifestation:

  • intestinal phase: diarrhea, abdominal pain, vomiting, weight loss
  • lung migratory phase: coughing, shortness of breath

• Diagnosis: Stool sample testing for rhabditiform larvae, entero-test (string test), antibody detection.

• Treatment: Thiabendazole.

• Prevention: Wearing shoes, avoiding contaminated soil.

Filariasis

• Aetiological agents: Caused mostly by Wuchereria bancrofti.
• Habitat: adult worms in lymphatic vessels and lymph nodes.
• Morphology: Adult worms are long, hair-like structures. Male: 35-40 mm x 0.1 mm; Female: 90-100 mm x 0.25 mm. Microfilariae (290 μm x 6.7 μm) covered by hyaline sheath; appear in blood at night (10 pm - 4 am); lifespan of ~70 days.
• Life cycle: Mosquitoes act as the vector, ingesting microfilariae, which mature into infective larvae in the mosquito. Mosquito bites transfer these larvae to humans. These larvae mature into adult worms in the lymphatic system, and microfilariae are released back into the blood.
• Transmission: Mosquito bite; definitive host is mosquito
• Treatment: Diethylcarbamazine (DEC)
• Prevention: Sleeping under mosquito nets, wearing long sleeves and trousers, mosquito repellent during dusk and dawn.

Test your knowledge on the life cycle, treatment, and morphological forms of Entamoeba histolytica and malaria. This quiz covers various aspects including drug dosages, treatment forms, and potential side effects. Perfect for students studying microbiology or infectious diseases.