Advanced Medical Parasitology, Virology, and Infectious Disease Pathogenesis Study Guide on Infectious Pathogens

How many types of helminths classification?

There are 3 primary types of helminths: Nematodes (roundworms), Cestodes (tapeworms), and Trematodes (flukes).

Please describe cestode (tapeworm).

Cestodes are multisegmented organisms with segments called proglottids, varying from 20-40 meters in length. They consist of a scolex (head), neck, and strobili (chain of segments) and can infect humans like Tenia Saginata (beef) and Tenia Solium (pork).

Give an example of Trematodes.

Examples of Trematodes include Schistosoma species (blood flukes) and Fasciola hepatica (liver fluke).

Which larvae can penetrate through the skin?

Certain larvae, specifically Schistosomas and Strongyloides, can penetrate through the skin.

What is the pathogenesis of helminths?

Pathogenesis involves direct damage from worm activity such as occlusion, granulomas, and pressure atrophy, as well as indirect damage from immune-mediated inflammatory responses.

How is the action of Eosinophil on parasites?

Eosinophils kill parasites by attacking their surface, releasing toxic proteins, producing inflammatory cytokines, and aiding in tissue repair post-infection.

What are the signs & symptoms of parasite infection?

Symptoms include asthenia (weakness), chronic diarrhea, weight loss, and specific systemic symptoms like fever, anemia, and bloating, depending on the parasite involved.

When will we suspect parasite infection?

Suspect parasite infection in cases of chronic GI symptoms, anemia, unexplained eosinophilia, or history of consuming raw or contaminated food.

How to do the diagnosis of the parasites?

Diagnosis involves identifying ova or larvae in stool, detecting adult parasites, conducting serology tests, or using PCR for sensitive and specific detection.

Tell me about the treatment of parasites. (Drug name, dose)

• Antiprotozoal Drugs:   

  • Metronidazole/Tinidazole: Used for Amoeba, Giardia, and Trichomonas.   

  • Quinine: Used for Malaria.   

  • Sulfadiazine: Used for Toxoplasmosis.   

  • Chloroquine: Used for Malaria.

• Anti-helmintic Drugs and Dosages:   

  • Hookworms: Alber $400\,mg$ single dose OR Meben $500\,mg$ single dose OR Pyrentel pamoate $11\,mg/kg$ PO for $3$ days.   

  • Ascaris: Alber $400\,mg$ single dose OR Meben $500\,mg$ single dose OR Everestin $150-200\,ng/kg$ single dose.   

  • Trichuris : Alber $400\,mg$ for $3$ days OR Meben $500\,mg$ single dose OR Ivermectin $150-200\,ng/kg$ for $3$ days.

  • Strongyloides: Alber $400\,mg$ for $7$ days OR Ivermectin $200$ single dose for $2$ days.

• Drug Categories:   - Nematodes (Roundworm): Alber, Meben, Ivermectin, Pyrental Pamoate.   - Cestodes (Tapeworm): Praziquantel, Nickosawide.   - Trematodes (Flukes): Praziquantel, Triclabenda.

Give an example of a Neglected Tropical Disease.

An example of a Neglected Tropical Disease is Lymphatic Filariasis, Schostosoma Mekongiii,

What are the causative agents of fascioliasis?

Fascioliasis is caused by Fasciola hepatica and Fasciola gigantica.

What is the definitive host of fasciola? Accidental host? Intermediate host?

Definitive host: Ruminants (cattle, sheep); Accidental host: Humans; Intermediate host: Snails.

What is the life cycle of fasciola species?

Unembryonated eggs are passed in feces, develop in water, hatch and infect snails, then encyst on water plants as Metacercariae, which humans ingest.

What is the infective stage of fasciola for humans?

The infective stage for humans is the Metacercariae encysted on water plants.

How do humans acquire fascioliasis?

Humans acquire fascioliasis by ingesting contaminated water plants containing Metacercariae.

What are the signs & symptoms of Fasciolasis?

Symptoms include abdominal pain, fever, malaise, nausea, vomiting, eosinophilia, and hepatomegaly.

What is the drug of choice for fasciola?

The drug of choice for fascioliasis is

• Teclabendazzole given as 2 doses of 10 mg/kg. Every 12h

• Bithionol 30-50 mg/kg/dose for 3 time every 8h, and alteration ១ថ្ងៃ លំលង ១ ថ្ងៃ

What is the complication of Fasciolasis?

Complications include

• obstructive jaundice,

• pancreatitis,

• liver fibrosis,

• cholecystitis, Cholelithiasis , Cholongitis

• and intermittent pain.

Which group do Opisthorchis and Clonorchis belong to?

Opisthorchis and Clonorchis are classified as trematodes (flukes).

How to diagnose Opisthorchiasis?

Diagnosis involves a history of raw fish consumption, identifying eggs in stool, and imaging methods like ultrasound or CT.

What is the definitive host of Opisthorchis/Clonorchis?

Humans are the definitive hosts for Opisthorchis viverrini and Clonorchis sinensis.

How do humans get transmitted Opisthorchis/Clonorchis?

Humans contract Opisthorchis/Clonorchis by ingesting undercooked or raw freshwater fish containing Metacercariae.

Which organ is primarily affected by Opisthorchis/Clonorchis?

The primary organ affected is the liver.

What is the drug of choice for the treatment of Opisthorchiasis?

The drug of choice is Praziquantel, given as 25 mg/kg for 2 days.

What are the complications of Opisthorchiasis?

Complications include cholangiocarcinoma, cholangitis, cholecystitis, liver abscess, and pancreatitis.

How to prevent Opisthorchiasis?

Prevent Opisthorchiasis by avoiding raw freshwater fish and ensuring fish are cooked to appropriate temperatures.

How many types of Echinococcosis?

There are two types of Echinococcosis: Cystic Echinococcosis and Alveolar Echinococcosis.

Describe each type of Echinococcosis.

Cystic Echinococcosis is caused by E. granulosus, while Alveolar Echinococcosis is caused by E. multilocularis.

What is the life cycle of Echinococcosis?

The life cycle involves embryonated eggs being ingested by intermediate hosts, leading to the development of hydatid cysts.

How many centimeters does Echinococcosis grow per year?

Echinococcosis cysts grow at a rate of 1-5 cm per year.

Describe the hydatid cyst.

Hydatid cysts have three layers: pericyst (host tissue), laminated layer (acellular barrier), and germinal layer (produces fluid and daughter cysts).

How to diagnose Echinococcosis?

Diagnosis involves imaging, serology tests, and sometimes the PAIR procedure (Puncture, Aspiration, Injection, Reaspiration).

What is the drug of choice for treatment of Echinococcus?

The drug of choice is Albendazole, with specific dosing based on the patient's weight.

Major complication of cyst echinococcus rupture?

Major complications include fever, urticaria, and anaphylactic reactions following cyst rupture.

What is Pneumocystis Jiroveci?

Pneumocystis Jiroveci is a unicellular fungus that causes pneumonia, particularly in immunocompromised individuals.

Which patients are at high risk for pneumocystosis?

High-risk patients include those with HIV/AIDS or those who are immunosuppressed.

Describe the characteristic of alveolar in PJP infection.

In PJP infection, the alveolar walls thicken with protein material and dead organisms, leading to impaired gas exchange.

What is the pathophysiology of PJP?

PJP leads to patchy interstitial pneumonia, impaired gas exchange, and hypoxia due to the accumulation of infections in the alveoli.

What is the route of transmission of PJP?

PJP is transmitted via inhalation of cysts present in the environment.

Clinical manifestations of PJP

Clinical manifestations include cough, dyspnea, fever, and progressive respiratory distress.

How to diagnose PJP?

Diagnosis is made through imaging, bronchoalveolar lavage (BAL), or lung biopsy.

What is the drug of choice for treatment of PJP?

The drug of choice for PJP is TMP-SMX (Co-trimoxazole).

What media do we use for Legionellosis culture?

Legionella requires Buffered Charcoal Yeast Extract (BCYE) agar for culture.

How does Legionella survive in macrophages?

Legionella survives in macrophages by blocking phagolysosome formation and creating a favorable environment for itself.

Name the most common species causing human infection?

The most common species causing human infections is Legionella pneumophila.

What is the mode of transmission of Legionella?

Legionella is transmitted through inhalation of aerosolized water droplets containing the bacteria.

What is Pontiac fever?

Pontiac fever is a self-limiting, flu-like illness caused by Legionella, typically resolving without treatment.

What is the drug of choice for treatment of Legionella?

The drug of choice for treatment of Legionella infection is fluoroquinolones.

What is the imaging finding seen in Covid-19?

Common imaging findings in Covid-19 include bilateral ground-glass opacities and consolidations in the lungs.

Describe the structure of SAR-CoV.

SARS-CoV has a lipid outer membrane, spike protein, helical nucleocapsid, and is approximately 125 nm in diameter.

What is the cytokine storm?

A cytokine storm is an excessive inflammatory response involving abnormal cytokine production, potentially leading to multi-organ failure.

What is the risk factor of SAR-CoV?

Risk factors for SAR-CoV infection include elderly age, chronic diseases, and immunosuppression.

Describe the pathogenesis of SAR-CoV.

Pathogenesis involves SARS-CoV binding to ACE2 receptors, leading to inflammation and impairments in lung function.

What is the complication of SAR-CoV?

Complications of SAR-CoV include ARDS (Acute Respiratory Distress Syndrome) and cytokine storm.

Define Long hold Covid.

Long hold Covid refers to the persistence of symptoms such as fatigue and cognitive dysfunction after recovery from the initial COVID-19 infection.

What is the etiology of toxic shock syndrome?

Toxic shock syndrome is caused by toxins from Staphylococcus aureus or Group A Streptococci.

What is the superantigen?

Superantigens are toxins that activate a large number of T-cells by binding to MHC Class II proteins and T-cell receptors, leading to massive immune responses.

Describe the pathophysiology of toxic shock syndrome.

Pathophysiology involves a cytokine storm that increases vascular permeability and causes hypotension and multi-organ failure.

What is the drug of choice for the treatment of toxic shock syndrome?

Treatment of toxic shock syndrome varies but may include Clindamycin and beta-lactams or Vancomycin for MRSA.

What is refractory shock and signs of shock?

Refractory shock does not respond to standard treatments; signs include fever, hypotension, and tachycardia.

What is the receptor of Adenovirus?

The receptor for Adenovirus is the Coxsackievirus-Adenovirus receptor (CAR).

What is the route of transmission of Adenovirus?

Adenovirus is transmitted via respiratory droplets, fecal-oral route, and conjunctival exposure.

What are the signs & symptoms of Adenovirus?

Symptoms include fever, respiratory distress, pharyngitis, cough, and conjunctivitis.