Comprehensive Study Guide for MD Year 6 Examination (2026): Helminthology, Infectious Diseases, and Pathophysiology

How many types of helminths classification?

There are three types of helminths classification: Nematodes (roundworms), Cestodes (tapeworms), and Trematodes (flukes).

Describe cestodes (tapeworms).

Cestodes have a long, flat, segmented body structure, with a scolex (head) featuring suckers or hooks for attachment and proglottids (individual segments containing reproductive organs). Leagth 20-40 m (Tenia saginita )

• Give an example of trematodes.

Examples of trematodes include

• Schistosomiasis caused by Schistosoma species,

• liver flukes like Fasciola hepatica, and

• lung flukes such as Paragonimus species.

• Which larvae can penetrate through the skin?

The larvae that can penetrate through the skin include

• Hookworms,

• Schistosoma,

• Strongiloid

• Filarial larvae.

What is the pathogenesis of helminths?

Helminths cause

• direct damage from

  • Occlusion : blockage of internal organs by paracite growth: Ascaris —> block intestine and Fliatocaria —→ block Lympathic —→ Elephantiasis

  • Granulomas : Schistosome block egg block blood flow to liver —→ Chronic injury and inflammatio —→ Form to granulomas and fibrosis —> Block to portal vein —→ PVH —→ Splenomegally

  • Pressure atrophy : Parasit growth in form of large fluid fill cysts —→ Compression to organ —→

• indirect damage through host responses,: By immune mediated response —→ leading to pathological changes in various body systems.

How is the action of eosinophils on parasites?

Eosinophils kill parasites by:

• releasing toxic proteins,

• produce cytokines to reaction to other immune cells—> Increase Inflammation maker to parasite

• assist in tissue repair after infection : promote tissue repair and restore normal tisssue Function :

What are the signs and symptoms of parasite infection?

Signs and symptoms depend on the affected organ,

• General often including fever, malaise, asthenia , lose weight

• GI : abdominal pain, diarrhea

• Blood : eosinophilia, anemia , Thromcytopena

• Liver : Juancice , Hepatomegaaly

• Lung: hemoptysis

• CNS : Seizure , neulogic deficits

• Skin : itching, Uriticaria ,

• Urinary ; Hematouria or Dysuria

When should we suspect parasite infection?

Parasite infection should be suspected when there is an

• elevation in eosinophils (eosinophilia) and

• relevant clinical symptoms.

• History : ingest fish or contaminated food ….

How to diagnose parasites?

Diagnosis can be made through

• Stool culture,

• Stool examination

• serology tests ( ELISA, IgM, IgG ..)

• Abdominal Ultrasound

• chest X-ray, and

• echocardiogram.

Tell me about the treatment of parasites.

Anti-protozoan:

• Metronidazole , Tinidazole, Sulfanizole , Folinic acid….

• Anti- Helminths : Albendazoel, Mebendazole , Ivermectin …

Give an example of a neglected tropical disease.

Soil-transmitted helminthiasis, which includes intestinal worms such as hookworm and roundworm, is an example of a neglected tropical disease.

What are the causative agents of fascioliasis?

The causative agents of fascioliasis are liver flukes, particularly Fasciola hepatica.

What is the definitive host of fasciola?

The definitive hosts of Fasciola are cattle, sheep, and goats. Human beings can be accidental hosts.

What is the life cycle of fasciola species?

The life cycle includes: 1. Eggs in feces 2. Embryonation in water 3. Hatching and penetration of snails 4. Development through sporocysts, rediae, and cercariae 5. Free-swimming cercariae encyst on vegetation 6. Ingestion by host 7. Immature flukes migrate to liver.

What is the infective stage of fasciola for humans?

The infective stage of Fasciola for humans is the metacercariae present on aquatic vegetation.

How do humans acquire fascioliasis?

Humans acquire fascioliasis by consuming raw watercress or contaminated freshwater plants.

What are the signs and symptoms of fascioliasis?

Signs and symptoms include fever, malaise, nausea, vomiting, abdominal pain, diarrhea, and changes in bowel habits.

What is the drug of choice for fasciola?

The drug of choice for treating fascioliasis is Triclabendazole, administered at $10\,mg/kg$ every 12 hours.

What are the complications of fascioliasis?

Complications can include intermittent abdominal pain, cholelithiasis, cholangitis, obstructive jaundice, and liver fibrosis.

Which group do Opisthorchis and Clonorchis belong to?

Opisthorchis and Clonorchis are both trematodes belonging to the family Opisthorchiidae.

How to diagnose Opisthorchiasis?

Diagnosis of Opisthorchiasis is performed via stool specimen examination, ultrasound, CT, MRI, and serology.

What is the definitive host of Opisthorchis/Clonorchis?

The definitive hosts are humans, dogs, cats, and other fish-eating mammals.

How do humans transmit Opisthorchis/Clonorchis?

Transmission occurs by consuming raw or undercooked freshwater fish.

Which organ is primarily affected by Opisthorchis/Clonorchis?

The liver and bile duct are primarily affected by Opisthorchis and Clonorchis.

What is the drug of choice for treatment of Opisthorchiasis?

The drug of choice for treating Opisthorchiasis is Praziquantel, administered at $25\,mg/kg$ orally three times daily for two days.

What are the complications of Opisthorchiasis?

Complications include hepatitis B and C, biliary obstruction, pancreatitis, and an increased risk of bile duct cancer.

How to prevent Opisthorchiasis?

Prevention involves avoiding consumption of raw or undercooked freshwater fish in endemic areas.

How many types of Echinococcosis?

There are two types of Echinococcosis: alveolar echinococcosis and cystic echinococcosis.

Describe each type of Echinococcosis.

Alveolar echinococcosis leads to tumor-like cysts in the liver, while cystic echinococcosis causes fluid-filled cysts, primarily affecting the liver and lungs.

What is the life cycle of Echinococcosis?

The life cycle includes eggs passed in feces, ingestion by intermediate hosts, and development of cysts.

How many centimeters does Echinococcosis grow per year?

Echinococcosis cysts grow from 1 to 5 cm per year.

Describe the hydatid cyst.

The hydatid cyst is a fluid-filled structure that can occur in organs like the liver and lungs.

How to diagnose Echinococcosis?

Diagnosis of Echinococcosis involves imaging, serological tests, and examination of cyst fluid.

What is the drug of choice for treatment of Echinococcus?

The drug of choice for treating Echinococcosis is Albendazole, dosed based on patient weight and divided over cycles.

What is a major complication of cyst echinococcus rupture?

Major complications include fever, urticaria, and serious anaphylactic reactions.

What is Pneumocystis Jiroveci?

Pneumocystis jiroveci is a unicellular fungus associated with pneumonia, particularly in immunocompromised individuals.

Which patients are at high risk for pneumocystosis?

High-risk patients include those with immunosuppression, particularly individuals with HIV.

Describe the characteristics of alveolar in PJP infection.

Alveolar changes include interstitial pneumonia with thickened walls and alveoli filled with proteinaceous material.

What is the pathophysiology of PJP?

PJP causes lung infection through airborne transmission, leading to pneumonia characterized by respiratory dysfunction.

What is the route of transmission of PJP?

PJP is transmitted through airborne routes.

Clinical manifestation of PJP

Clinical manifestations include dyspnea, fever, cough, and chest discomfort.

How to diagnose PJP?

Diagnosis of PJP involves chest X-ray, sputum analysis, blood tests, and bronchoalveolar lavage.

What is the drug of choice for treatment of PJP?

The drug of choice for PJP is TMP-SMX (Trimethoprim-sulfamethoxazole).

What media do we use for Legionellosis culture?

Legionella is cultured on Buffered Charcoal Yeast Extract (BCYE) media.

How does Legionella survive in macrophages?

Legionella survives in macrophages by evading phagocytosis and manipulating the host cell's immune responses.

Name the most common species causing human infection.

Legionella pneumophila is the most common species causing human legionellosis.

What is the mode of transmission of Legionella?

Legionella is transmitted through inhalation of aerosols from contaminated water sources.

What is Pontiac fever?

Pontiac fever is a mild, flu-like illness caused by Legionella, without pneumonia.

What is the drug of choice for treatment of Legionella?

The drug of choice for treating Legionella infection is Fluoroquinolones or Macrolides.

What imaging findings are seen in Covid-19?

Imaging findings in COVID-19 typically show consolidation and ground-glass opacities.

Describe the structure of SARS-CoV.

SARS-CoV is an enveloped, positive-sensed single-stranded RNA virus, approximately 125 nm in diameter.

What is the cytokine storm?

The cytokine storm is an excessive immune response with high levels of cytokines, which can lead to severe inflammation and tissue damage.

What are the risk factors of SARS-CoV?

Risk factors include age over 65, chronic diseases, immunocompromised state, and smoking.

Describe the pathogenesis of SARS-CoV.

SARS-CoV enters the body through respiratory droplets, binds to ACE2 receptors, and triggers a strong immune response that can lead to severe disease.

What are the complications of SARS-CoV?

Complications include ARDS, multi-organ failure, and cardiovascular complications.

Define Long COVID.

Long COVID refers to persistent symptoms such as dyspnea and malaise that last for weeks or months following the acute phase of the infection.

What is the etiology of toxic shock syndrome?

Toxic shock syndrome is mainly caused by Staphylococcus aureus and Group A Streptococci due to superantigen release.

What is the superantigen?

Superantigens are toxins that provoke an intense immune response by activating a large number of T-cells.

Describe the pathophysiology of toxic shock syndrome.

Toxic shock syndrome is characterized by T-cell stimulation leading to a cytokine storm, increased vascular permeability, and tissue injury.

What is refractory shock and signs of shock?

Refractory shock is severe shock that does not respond to treatment, presenting with hypotension, tachycardia, and altered mental status.

What is the receptor of Adenovirus?

Adenoviruses use a variety of receptors for attachment, including the coxsackievirus-adenovirus receptor (CAR).

What is the route of transmission of Adenovirus?

Adenovirus is transmitted via respiratory droplets, conjunctiva, fecal-oral route, and occasionally by the urinary tract.

What are the signs and symptoms of Adenovirus?

Signs and symptoms include fever, sore throat, cough, and conjunctivitis in children.