Choose 1 species of protozoa and 2 species fungi/yeast/mold that you find interesting and DRAW its pathogenesis. Write its pathological effects, diagnosis and prevention

Plasmodium falciparum

• Pathogenesis

  • Transmission occurs when an infected female Anopheles mosquito injects sporozoites into the human bloodstream during a blood meal

  • Sporozoites invade hepatocytes and undergo exoerythrocytic schizogony, producing thousands of merozoites that are released into the circulation

  • Merozoites invade red blood cells and develop through ring, trophozoite, and schizont stages, culminating in erythrocyte rupture and release of new infective forms

  • Infected erythrocytes express PfEMP1, promoting cytoadherence to endothelial receptors and sequestration in microvasculature, leading to microvascular obstruction and local inflammation

  • Pro‑inflammatory cytokines such as TNFα and IL‑1 are released, driving fever, endothelial activation, and systemic inflammatory response

• Pathological effects

  • Periodic high‑grade fevers, rigors, and chills corresponding to synchronous schizont rupture

  • Hemolytic anemia, jaundice, and splenomegaly due to massive destruction and clearance of parasitized erythrocytes

  • Cerebral malaria characterized by seizures, altered consciousness, and high mortality from brain microcirculatory obstruction

  • Acute kidney injury, metabolic acidosis, and hypoglycemia arising from microvascular dysfunction and high parasite biomass

• Diagnosis

  • Thick and thin Giemsa‑stained blood smears remain the gold standard for detecting ring forms, trophozoites, schizonts, and gametocytes

  • Rapid diagnostic tests targeting HRP2 antigen provide point‑of‑care detection with high sensitivity for P. falciparum

  • PCR assays enable species‑specific identification and quantification of parasitemia in reference laboratories

• Prevention

  • Insecticide‑treated bed nets and indoor residual spraying reduce mosquito‑human contact and transmission risk

  • Chemoprophylaxis with atovaquone‑proguanil, doxycycline, or mefloquine is recommended for travelers to endemic regions

  • RTS,S vaccine implementation in high‑burden areas has been shown to decrease clinical malaria incidence

Candida albicans

• Pathogenesis

  • Normally a commensal yeast on mucosal surfaces, it undergoes a morphological switch to pseudohyphae and true hyphae under immunocompromised or dysbiotic conditions, facilitating tissue invasion

  • Adhesin proteins Als3 and invasin Ssa1 mediate tight binding to epithelial and endothelial cells, triggering endocytosis of the fungus

  • Secretion of hydrolytic enzymes, including secreted aspartyl proteases (SAPs) and phospholipases, degrades host tissues and promotes deep invasion

  • Biofilm formation on indwelling medical devices generates a protected environment resistant to antifungal therapy

• Pathological effects

  • Oropharyngeal candidiasis presents as white adherent plaques on the tongue and buccal mucosa, often painful and bleeding on scraping

  • Vulvovaginal candidiasis manifests with intense itching, erythema, and thick cottage‑cheese‑like discharge

  • Invasive candidiasis in immunosuppressed patients can lead to candidemia, endocarditis, hepatosplenic microabscesses, and septic shock

• Diagnosis

  • Microscopic examination of 10 % KOH wet mounts or Gram‑stained smears reveals budding yeast cells and pseudohyphae

  • Germ tube test in human serum at 37 °C yields true germ tubes within 2 hours, confirming C. albicans

  • Culture on Sabouraud dextrose agar produces creamy smooth colonies and green colonies on CHROMagar for presumptive identification

  • 1,3‑β‑D‑glucan assay and mannan antigen detection aid in early diagnosis of invasive disease

• Prevention

  • Maintain good mucosal hygiene and manage predisposing factors such as uncontrolled diabetes and antibiotic overuse

  • Employ strict aseptic technique and timely replacement of catheters and central lines to prevent device‑associated biofilm infections

  • Consider prophylactic fluconazole or echinocandins in high‑risk neutropenic or transplant patients

Aspergillus fumigatus

• Pathogenesis

  • Small airborne conidia (2–3 μm) are inhaled and deposit in alveoli, where they are normally cleared by alveolar macrophages in immunocompetent hosts

  • In immunocompromised individuals, conidia evade phagocytosis, germinate into hyphae, and penetrate pulmonary epithelium

  • Hyphal angioinvasion damages vascular endothelium, induces tissue factor expression, thrombosis, and tissue infarction

  • Secretion of gliotoxin impairs neutrophil and macrophage function, facilitating unchecked fungal proliferation

  • Host airway epithelial cells release cytokines and chemokines that drive neutrophil recruitment and contribute to pulmonary inflammation

• Pathological effects

  • Invasive pulmonary aspergillosis presents with fever, pleuritic chest pain, cough, and hemoptysis, often rapidly progressive

  • Allergic bronchopulmonary aspergillosis occurs in atopic individuals, leading to bronchospasm, eosinophilia, and bronchiectasis

  • Aspergilloma or fungus ball forms within preexisting lung cavities, causing chronic cough and hemoptysis

  • Chronic pulmonary aspergillosis leads to weight loss, fatigue, productive cough, and progressive respiratory failure

• Diagnosis

  • Chest CT imaging reveals the halo sign in early invasive disease and the air crescent sign during recovery

  • Microscopy and culture of respiratory specimens show septate hyphae with acute angle (45°) branching

  • Detection of galactomannan antigen in serum or bronchoalveolar lavage fluid enables early diagnosis

  • Aspergillus‑specific PCR assays on blood or BAL fluid increase sensitivity, especially in neutropenic patients

• Prevention

  • HEPA‑filtered air systems and protective isolation units reduce environmental spore exposure in high‑risk wards

  • Limit patient exposure to construction, gardening, and compost during periods of profound immunosuppression

  • Prophylactic antifungal therapy with voriconazole or posaconazole is recommended for hematopoietic stem cell transplant recipients and prolonged neutropenia