CAP 8- ENFERMEDADES INFECCIOSAS-PATOLOGÍA ESTRUCTURAL Y FUNCIONAL DE ROBBINS Y COTRAN-RESUMEN

Capítulo 8: Enfermedades Infecciosas

Introducción a la Patogenia Microbiana

• Las enfermedades infecciosas son una causa significativa de mortalidad, especialmente en ancianos y personas inmunodeprimidas.

• En países en desarrollo, las patologías infecciosas, agravadas por la malnutrición y malas condiciones de vida, son responsables de muchas muertes; las afecciones respiratorias y diarreicas infantiles son las más comunes.

Microbioma Humano

• Los humanos albergan un ecosistema complejo de microbios conocido como microbioma, con una cantidad de microbios diez veces mayor que el número de células humanas.

• La mayoría de estos microbios son comensales que no causan daño; sin embargo, pueden provocar infecciones si las defensas del cuerpo disminuyen.

Vías de Penetración de Microbios

• Los microbios acceden al cuerpo a través de diversas barreras protectoras como la piel, mucosas y productos secretorios (ej. lisozima en lágrimas).

• Lesiones o traumas pueden permitir que los microbios penetren y causen infecciones; se mencionan varias vías específicas:

• Piel: Actúa como barrera externa; lesiones permiten infecciones.

• Tubo Digestivo: Barreras incluyen ácido gástrico y enzimas digestivas; debilitamiento puede ocurrir por antibióticos o baja acidez.

• Aparato Respiratorio: Defensas incluyen actividad ciliar y macrófagos alveolares; factores como tabaquismo pueden interferir.

• Tracto Urogenital: Lavado frecuente por orina actúa como defensa; alteraciones pueden favorecer infecciones.

Transmisión de Microbios

• Los microorganismos se transmiten entre individuos a través de rutas respiratorias, fecal-orales, sexuales o transplacentarias.

• También pueden ser transmitidos por contacto directo o vectores (insectos); algunos sobreviven largo tiempo en el ambiente (ej. polvo).

Diseminación y Respuesta Inmune

• La diseminación puede ser local o a través del torrente sanguíneo/linfático/sistema nervioso; algunos microorganismos tienen tropismo específico hacia ciertas localizaciones del cuerpo.

• La propagación depende de la magnitud de diseminación, virulencia del microorganismo y respuesta inmune del anfitrión.

Defensas del Anfitrión

• El cuerpo humano tiene barreras físicas (como la piel) y un sistema inmunitario (innato/adaptativo), que actúan para defenderse contra infecciones.

Understanding Immune Evasion and Damage Mechanisms

Latent Pathogens and Immune Evasion Strategies

• Latent pathogens do not cause immediate harm but can reactivate when the host's immune system weakens, leading to diseases like tuberculosis or viral infections.

• Various strategies exist for pathogens to evade detection by the immune system:

• Antigenic Variation: Some pathogens change their identity to avoid antibodies.

• Resistance to Antimicrobial Peptides: Microbes may alter their surface or produce substances that prevent attacks from body defenses.

• Phagocytosis Resistance: Certain bacteria possess capsules that hinder immune cells from engulfing and destroying them.

• Apoptosis Blocking: Some pathogens prevent infected cells from undergoing programmed cell death, allowing prolonged replication.

• Cytokine Interference: Pathogens can produce proteins that inhibit immune signaling, complicating the body's response.

Negative Effects of Immune Responses

• While crucial for fighting infections, the immune response can also inflict damage on the body:

• Granulomas Formation: In conditions like tuberculosis, immune cells form granulomas that isolate pathogens but may damage surrounding tissues.

• Liver Injury: Infections such as hepatitis B can lead to liver cell destruction by the immune system, resulting in hepatic damage.

• Autoimmune Reactions: Antibodies may mistakenly target the body's own cells, seen in conditions like rheumatic heart disease and glomerulonephritis.

• Chronic Inflammation and Cancer Risk: Chronic inflammation from infections (e.g., Helicobacter pylori) can increase gastric cancer risk.

Immunodeficiencies and Susceptibility

• Individuals with weakened immune systems are more prone to infections due to genetic or acquired immunodeficiencies:

• Genetic examples include agammaglobulinemia, where insufficient antibody production heightens vulnerability to bacterial and viral infections.

• Acquired immunodeficiency is exemplified by HIV infection, which destroys lymphocytes and diminishes overall immunity while promoting opportunistic infections. Additionally, malnutrition and organ transplant-related immunosuppression weaken defenses further.

Host Damage Mechanisms in Infectious Diseases

• Infectious diseases result from interactions between microbial virulence factors and host immune responses:

• Direct cellular death occurs when microorganisms invade host cells leading to destruction.

• Toxins released by microbes can kill distant cells.

• Enzymatic degradation of tissue components contributes to cellular damage.

• Vascular injury leads to ischemic necrosis through blood vessel damage.

• The inflammatory response itself may harm tissues during pathogen clearance efforts.

Viral Mechanisms of Damage

• Viruses exhibit specific tropism affecting certain tissues based on several factors:

• Attachment to surface proteins on host cells (e.g., HIV binds CD4 receptors on T lymphocytes).

• Specific transcription factors allow viruses like JC virus to infect only oligodendrocytes.

• Physical/chemical conditions influence viral survival; some viruses withstand acidic environments (e.g., enteroviruses).

Key Characteristics of Viral Damage Mechanisms

• Direct cytopathic effects involve inhibiting cellular synthesis (DNA/RNA/proteins) leading to cell lysis (e.g., influenza virus).

• Induction of apoptosis results in programmed cell death triggered by viral infection.

• An antiviral immune response activates cytotoxic lymphocytes and natural killer cells against infected hosts.

Bacterial Virulence Factors

• Bacterial pathogenicity relies on their ability to adhere, invade host tissues, or release toxins impacting health outcomes significantly.

This structured summary provides a comprehensive overview of key concepts related to pathogen evasion mechanisms, negative impacts of immune responses, immunodeficiencies' role in susceptibility, mechanisms of infectious disease damage including those caused by viruses and bacteria—all anchored with precise timestamps for easy reference within the transcript context.

Mechanisms of Bacterial Virulence

Plasmids and Biofilms

• Plasmids and bacteriophages facilitate the transfer of virulence factors among bacteria.

• Biofilm formation allows bacteria to cluster in viscous layers, providing protection against immune responses and certain antibiotics.

Adhesion Mechanisms

• Adhesins are proteins that enable bacterial adherence to host cells, aiding in evasion from the immune system.

• Variations in pili serve as immune evasion mechanisms for Neisseria gonorrhoeae, preventing elimination by the host's defenses.

Toxins: Endotoxins vs. Exotoxins

• Endotoxins, found in the cell wall of Gram-negative bacteria (e.g., lipopolysaccharides), can induce inflammation and septic shock at high doses.

• Exotoxins are secreted by bacteria to damage tissues and alter cellular functions; examples include neurotoxins like those causing botulism.

Sexually Transmitted Infections (STIs)

High-Risk Groups

• Certain demographics such as adolescents, men who have sex with men, and intravenous drug users are identified as high-risk groups for STIs.

Transmission Dynamics

• STIs require direct contact between individuals for transmission since pathogens do not survive well outside a host; asymptomatic carriers often spread infections.

Co-infection Risks

• Infection with one STI increases susceptibility to others due to shared risk factors; mucosal lesions can facilitate co-infection.

Inflammatory Responses to Infections

Basic Tissue Responses

• Basic tissue responses involve five histological patterns that occur in reaction to diverse microbial threats or physical/chemical injuries.

Types of Inflammation

• Suppurative inflammation is characterized by pus formation due to extracellular Gram-positive cocci or Gram-negative bacilli recruitment of neutrophils.

Mononuclear and Granulomatous Responses

• Mononuclear inflammation typically arises from viral infections or intracellular bacterial infections involving lymphocytes and macrophages.

Cytopathic Reactions

• Cytopathic-cytoproliferative reactions are common in viral infections where there is cellular proliferation with minimal inflammation observed.

Necrosis

• Tissue necrosis may occur due to uncontrolled viral infections or secreted bacterial toxins without significant inflammatory response.

Chronic Inflammation

• Chronic inflammation can lead to excessive scarring or dysfunction even when few microorganisms are present, exemplified by conditions like tuberculosis.

Diagnostic Techniques for Infectious Agents

Visualization Methods

Infections and Their Diagnosis

Microorganism Identification

• Tissue or fluid cultures from lesions help identify microorganisms and perform antibiograms.

• IgM antibodies indicate acute infections, while IgG antibodies suggest past or chronic infections.

Nucleic Acid Amplification Tests

• Nucleic acid amplification tests are used to diagnose infections like tuberculosis, Neisseria gonorrhoeae, chlamydia, and monitor HIV treatment.

Viral Infections Overview

• Viral infections can be transient, latent (chronic), or even lead to cellular transformation and malignancies.

• Acute viral infections are caused by diverse viruses that trigger effective immune responses for elimination.

Specific Viral Infections

Measles (Sarampión)

• Caused by an RNA paramyxovirus; transmitted via respiratory droplets with initial replication in respiratory epithelial cells.

• Key features include Koplik spots (oral lesions), lymphatic hyperplasia, and Warthin-Finkeldey cells.

• Complications may include tracheitis, pneumonia, diarrhea, keratitis (risk of blindness), and encephalitis. Vaccination is crucial for immunity.

Mumps (Parotiditis)

• Caused by a paramyxovirus; spreads through respiratory droplets affecting lymph nodes before salivary glands.

• Complications can involve aseptic meningitis (10% of cases), orchitis, pancreatitis, and central nervous system effects.

Poliovirus and Other Viruses

Poliovirus

• An enterovirus RNA transmitted fecal-orally; characterized by fever and viremia potentially leading to paralysis.

• Complications such as poliomyelitis occur in about 1 in 100 infected individuals.

Flavivirus

• Includes West Nile virus; transmitted by mosquitoes with birds as primary reservoirs.

• Initial infection occurs in dendritic skin cells; complications may involve neurological issues like meningitis or encephalitis.

Viral Hemorrhagic Fevers

Characteristics of Hemorrhagic Viruses

• Caused by various RNA viruses including arenaviruses and filoviruses; typically transmitted through infected animals or insects.

• Symptoms include fever, headache, myalgia, rash, thrombocytopenia; severe endothelial infection can lead to hemorrhagic manifestations.

Latent Viral Infections

Herpes Virus Infections

• Latency refers to the persistence of viral genomes without producing infectious virus. Reactivation can cause tissue damage.

Classification of Herpes Viruses

1. Alpha Group: Infect epithelial cells establishing latency in neurons (e.g., HSV1 & HSV2).

2. Beta Group: Infect lymphocytes maintaining latency in various cell types (e.g., CMV).

3. Gamma Group: Cause latency in lymphoid cells (e.g., EBV).

Herpes Simplex Virus (HSV)

Virus Propagation and Pathogenesis

Herpes Simplex Virus (HSV) Infections

• The virus propagates to sensory neurons, transported axonally to sensory ganglia where latency is established. During reactivation, it moves from skin ganglia to mucosal areas.

• Common lesions include self-limiting cold sores and gingivostomatitis due to HSV-1, as well as genital ulcers from HSV-2. Severe complications can lead to disseminated visceral infections like hepatitis and encephalitis.

• HSV-1 is a leading cause of corneal blindness in the U.S., with epithelial keratitis showing cytolysis of corneal epithelium and stromal keratitis characterized by mononuclear cell infiltrates.

• Microscopic findings reveal large intranuclear inclusions with purple birions, A-type Crow inclusions, and multinucleated giant cells.

Varicella-Zoster Virus (VZV)

• VZV spreads via aerosols and hematogenous routes causing skin vascular lesions. Acute infection results in chickenpox; reactivation leads to herpes zoster.

• Similar to HSV, VZV infects mucosae, skin, and neurons establishing latency in sensory ganglia. Reactivation causes painful vesicular lesions in dermatomes.

• Complications may include interstitial pneumonia, encephalitis, transverse myelitis, especially in immunocompromised individuals. Skin lesions evolve rapidly from macules to vesicles resembling dew drops on rose petals.

Cytomegalovirus (CMV)

• CMV transmission occurs through saliva, blood, breast milk; can be congenital or via transfusions. In immunocompetent individuals, infections are often asymptomatic but may present as infectious mononucleosis-like syndromes.

• In immunocompromised patients, CMV can cause severe conditions such as colitis and pneumonitis. Congenital infections may lead to significant health issues despite most infants being asymptomatic at birth.

• Symptoms of congenital CMV infection include growth retardation and neurological deficits like hearing loss or mental retardation.

• Microscopic examination shows enlarged cells with large intranuclear inclusions surrounded by a clear halo.

Chronic Viral Infections

• Some viral infections result in chronic conditions where the immune system fails to eradicate the virus completely leading to persistent viremia.

Epstein-Barr Virus (EBV)

• EBV primarily transmits through close contact such as saliva or sexual contact; initial infection occurs in nasopharyngeal epithelial cells before targeting B lymphocytes in underlying lymphatic tissues.

• The virus binds CD21 receptors on B cells initiating an initial phase followed by lytic and latent phases; lytic phase produces new virions while most B cells establish latency promoting proliferation of B lymphocytes.

Associated Diseases

Infectious Diseases Overview

Characteristics of Infectious Diseases

• Discusses benign infectious diseases characterized by fever, sore throat, lymphadenopathy, splenomegaly, and occasionally hepatitis or skin rash.

• Highlights the role of CD8 T cells in eliminating infected B lymphocytes, contributing to lymphadenopathy and splenomegaly.

Bacterial Infections: Staphylococci

• Introduces common human infections caused by Gram-positive bacteria like staphylococci and streptococci.

• Focuses on Staphylococcus aureus, responsible for various infections including skin infections (furuncles and carbuncles), osteomyelitis, pneumonia, endocarditis, food poisoning, and toxic shock syndrome.

• Mentions virulence factors such as surface proteins for host cell adhesion, enzymes that degrade host proteins for tissue invasion, and toxins damaging cell membranes.

Antibiotic Resistance Concerns

• Notes the growing concern over methicillin-resistant Staphylococcus aureus (MRSA), which poses a significant health risk due to its virulence in community settings.

Streptococcal Infections

• Discusses Streptococcus pyogenes (Group A), known for causing pharyngitis, scarlet fever, impetigo, rheumatic fever, and glomerulonephritis.

• Also covers Streptococcus pneumoniae, an alpha-hemolytic bacterium responsible for pneumonia and meningitis in adults.

Other Notable Bacterial Infections

• Describes Corynebacterium diphtheriae, the causative agent of diphtheria which produces an exotoxin that blocks protein synthesis in host cells leading to severe organ damage.

• Introduces listeriosis caused by Listeria monocytogenes, particularly dangerous for immunocompromised individuals and pregnant women due to its invasive mechanisms using actin filaments.

Anthrax and Nocardiosis

• Explains anthrax caused by Bacillus anthracis, which can manifest in cutaneous forms with necrotic ulcers or systemic forms leading to septicemia from inhalation or ingestion of contaminated meat.

• Discusses nocardiosis caused by Nocardia asteroides affecting respiratory systems primarily in immunocompromised patients.

Meningitis Causing Neisseria Species

• Covers Neisseria meningitidis, a major cause of bacterial meningitis especially in children under 2 years old; transmission occurs via respiratory droplets with colonization rates around 10% in the population.

Gonorrhea: A Common Infection

• Details gonorrhea caused by Neisseria gonorrhoeae, prevalent in the U.S., leading to symptomatic urethritis in men and pelvic inflammatory disease or infertility in women.

Pertussis: Whooping Cough Insights

Bacterial Infections and Their Pathogenic Mechanisms

Overview of Respiratory Bacterial Infections

• Discusses the impact of respiratory cilia paralysis, leading to tracheobronchial mucosal erosions and mucopurulent exudates.

• Introduces Pseudomonas aeruginosa, an opportunistic aerobic gram-negative bacillus prevalent in cystic fibrosis patients, burn victims, neutropenic individuals, and contact lens users.

Virulence Factors of Pseudomonas

• Highlights virulence factors such as adhesins, endotoxins, and exotoxins (e.g., phospholipase C), which facilitate infection.

• Explains biofilm formation as a protective mechanism against immune defenses and antibiotics; associated with tissue necrosis and hemorrhagic skin lesions.

Notable Bacterial Pathogens

• Mentions Yersinia pestis as a significant intracellular pathogen causing plague; transmitted via aerosols or flea bites.

• Describes clinical manifestations of plague including buboes, pneumonia, septicemia, and necrosis.

Other Relevant Bacteria

• Discusses Haemophilus ducreyi prevalent in Africa and Southeast Asia; causes painful genital ulcers and acts as a cofactor for HIV transmission.

• Introduces Klebsiella granulomatis responsible for granuloma inguinale characterized by painless ulcers that may lead to urethral or anal obstruction.

Mycobacteria: Characteristics and Tuberculosis

General Characteristics of Mycobacteria

• Defines mycobacteria as aerobic bacilli rich in mycolic acid; classified as acid-fast bacilli due to their resistance to acid treatment.

Tuberculosis Overview

• Notes tuberculosis affects approximately 1 billion people globally with 1.4 million annual deaths; reports around 10,000 new cases annually in the U.S., primarily among vulnerable groups.

Transmission Dynamics

• Explains transmission through aerosols during sneezing; highlights rising cases of multi-drug resistant strains.

Infection vs. Disease

• Distinguishes between tuberculosis infection (presence without symptoms) versus disease (symptomatic presentation); emphasizes virulence linked to cell wall structure rather than toxins.

Host Immunity Response to Mycobacterial Infection

Immune Activation Mechanisms

• Describes initial recognition by host receptors TLR2 and TLR9 leading to TH1-mediated immune response activating macrophages via interferon-gamma.

Microbial Clearance Strategies

• Outlines mechanisms like nitric oxide production and autophagy contributing to microbial death alongside caseating granuloma formation.

Diagnosis and Clinical Evolution of Tuberculosis

Diagnostic Techniques

• Lists diagnostic methods including tuberculin skin test (PPD), sputum smear for acid-fast bacilli, culture techniques for antibiogram development, and PCR testing noted for high sensitivity.

Clinical Progression Stages

Overview of Mycobacterial Infections

Mycobacterium Avium Complex and Tuberculosis

• Discusses symptoms such as night sweats, pulmonary cavitation, and weight loss associated with the Mycobacterium avium complex, particularly affecting immunocompromised individuals.

• Introduces tuberculosis caused by Mycobacterium tuberculosis, highlighting its impact on health.

Leprosy: Causes and Clinical Forms

• Explains leprosy (Hansen's disease), caused by Mycobacterium leprae, transmitted through hematogenous routes after initial macrophage phagocytosis.

• Describes two clinical forms of leprosy: tuberculoid (TH1 response with few bacilli and insensitive skin lesions) and lepromatous (TH2 response with ineffective immune reaction).

Understanding Spirochetes and Syphilis

Characteristics of Spirochetes

• Defines spirochetes as gram-negative bacteria shaped like corkscrews, possessing flagella that can evade host immune responses.

Syphilis: Stages and Pathophysiology

• Details syphilis caused by Treponema pallidum, transmitted sexually or transplacentally (congenital syphilis).

• Outlines primary syphilis symptoms including a painless chancre appearing about three weeks post-exposure.

• Describes secondary syphilis occurring 2 to 10 weeks later with systemic symptoms like lymphadenopathy and skin lesions.

• Discusses tertiary syphilis developing after five years leading to cardiovascular issues, neuro-syphilis, and benign gummas.

Congenital Syphilis Diagnosis

Types of Congenital Syphilis

• Differentiates between early congenital syphilis (with symptoms like nasal discharge and hepatomegaly) versus late congenital syphilis characterized by Hutchinson's triad (notched incisors, deafness, keratitis).

Diagnostic Methods for Syphilis

• Highlights treponemal tests detecting specific antibodies against Treponema pallidum alongside non-treponemal tests like VDRL for variable sensitivity based on disease stage.

Lyme Disease Overview

Causative Agent of Lyme Disease

• Identifies Borrelia burgdorferi as the causative agent of Lyme disease transmitted via Ixodes ticks.

Clinical Stages of Lyme Disease

• Describes Stage 1 presenting erythema migrans along with fever; Stage 2 includes secondary skin lesions and systemic symptoms; Stage 3 involves chronic arthritis and neurological complications over years.

Clostridia Infections

Characteristics of Clostridia

• Notes clostridia as gram-positive anaerobic bacilli capable of producing spores found in various environments.

Diseases Associated with Clostridia

• Discusses Clostridium perfringens causing gas gangrene characterized by edema and necrosis due to enzymatic activity.

Infections and Pathogens Overview

Pseudomembranous Colitis and Anaerobic Abscesses

• Pseudomembranous colitis is caused by an imbalance in intestinal flora, often following antibiotic therapy.

• Mixed bacterial flora from neighboring sites (e.g., intestines, female genital tract) can lead to anaerobic abscesses.

• These abscesses may have foul odors and resemble biogenic infections; bacteria thrive intracellularly with adaptations for nutrient capture.

Chlamydia Infections

• Chlamydia species, such as Chlamydia trachomatis, are small Gram-negative bacteria with a unique life cycle involving elementary bodies (infectious form) and reticulate bodies (metabolically active).

• Diseases caused include trachoma (ocular infection), urogenital infections, conjunctivitis, epididymitis, prostatitis, pelvic inflammatory disease, and pharyngitis.

• Lymphogranuloma venereum is associated with serotypes L1 and L3, causing painful lymphadenopathy with granulomatous responses.

Rickettsial Infections

• Rickettsia are Gram-negative bacilli transmitted by arthropods that primarily affect endothelial cells leading to vascular thrombosis and necrosis.

• Epidemic typhus is transmitted by lice; symptoms include exanthema with hemorrhages and central nervous system involvement.

• Rocky Mountain spotted fever is tick-borne; it presents as hemorrhagic exanthema affecting palms/soles and can cause pulmonary edema.

Fungal Infections

• Eukaryotic fungi possess characteristic cell walls; they can exist as yeasts or molds depending on environmental conditions.

Classification of Mycoses

• Superficial mycoses affect keratinized layers like skin/hair/nails.

• Subcutaneous mycoses impact deeper tissues but rarely disseminate systemically.

• Endemic mycoses involve dimorphic fungi causing severe systemic diseases even in healthy individuals.

• Opportunistic mycoses pose significant risks to immunocompromised patients or those with medical devices.

Candidiasis

Candidiasis and Other Fungal Infections

Virulence Factors of Yeasts

• Candidiasis is associated with virulence factors such as adhesins, invasive enzymes, catalases, and adenosine that inhibits neutrophils and biofilm formation.

Immune Response to Yeast Infections

• The immune response involves phagocytosis by neutrophils and macrophages, specifically a TH17 response activated by Candida glucan.

• Yeast forms induce protective TH1 responses while filamentous forms lead to non-protective TH2 responses.

Clinical Manifestations of Candidiasis

• Candidiasis can manifest in three forms: superficial (e.g., vaginitis), chronic (associated with AIDS or endocrine immunodeficiencies), and invasive (leading to bloodstream dissemination).

• Superficial candidiasis may present as vaginitis with white plaques; chronic cases are linked to severe immunocompromised states.

Cryptococcosis Overview

Characteristics of Cryptococcus Neoformans

• Cryptococcosis is caused by the encapsulated yeast Cryptococcus neoformans, which has polysaccharide capsules that inhibit phagocytosis.

• It produces laccase (an antioxidant pigment) and invasive enzymes.

Clinical Presentation in Different Populations

• In healthy individuals, it may cause pulmonary granulomas; in immunocompromised patients, it can lead to meningitis, encephalitis, and cerebral cysts known as "soap bubbles."

Aspergillosis Insights

Pathogen Characteristics

• Aspergillosis is caused by Aspergillus fumigatus which adheres to host proteins and possesses antioxidant defenses like melanin and mannitol.

Clinical Manifestations

• Symptoms include allergies, sinusitis, pneumonia in immunocompromised individuals; it can also lead to aspergillomas in pre-existing lung lesions.

• Severe cases may result in necrotizing pneumonia with vascular thrombosis leading to infarcts.

Zygomycosis Discussion

Pathogen Information

• Zygomycosis is caused by Mucor species; risk factors include neutropenia and diabetes with increased free iron levels.

Infection Sites and Consequences

• Depending on the infection site (nose, lungs, gastrointestinal tract), it can spread from sinuses to the orbit or brain causing vascular necrosis.

Dimorphic Fungi Overview

Types of Dimorphic Fungi

• Dimorphic fungi include Blastomyces, Coccidioides immitis, and Histoplasma capsulatum. Further details will be discussed in Chapter 15.

Parasitic Infections Summary

Introduction to Protozoa

• Protozoa are unicellular eukaryotic parasites primarily affecting humans through intestinal or blood infections transmitted via insects or fecal oral routes.

Malaria Overview

• Caused by Plasmodium spp., malaria transmission occurs through Anopheles mosquitoes. The lifecycle includes sporogony in hepatocytes followed by erythrocytic stages.

Pathogenic Mechanisms of Plasmodium

• Plasmodium falciparum infect erythrocytes indiscriminately causing vascular obstruction and inflammation due to TNF release. Genetic resistance factors include thalassemia traits.

Babesiosis Insights

Overview of Parasitic Diseases

Leishmaniasis

• Leishmaniasis is caused by protozoa transmitted by phlebotomine sandflies, with a life cycle involving extracellular promastigotes in vectors and intracellular amastigotes in macrophages.

• There are three types of leishmaniasis: cutaneous, mucocutaneous, and visceral, each presenting different clinical manifestations based on the species involved.

• Key virulence factors include complement activation/inhibition, reduced acidity in phagolysosomes, and macrophage defense mediated by gamma-interferon.

African Trypanosomiasis

• Caused by Trypanosoma brucei and transmitted by tsetse flies; it presents as fever, lymphadenopathy, encephalitis (known as sleeping sickness), cachexia, and can lead to death.

• Pathogenesis involves antigenic variation of surface glycoproteins known as VSG.

Chagas Disease

• Caused by Trypanosoma cruzi transmitted through triatomine bugs; it has acute and chronic phases.

• The acute phase may cause mild to severe cardiac damage while the chronic phase can lead to dilated cardiomyopathy, arrhythmias, colon dilation, or esophageal dilation.

Strongyloidiasis

• Strongyloides stercoralis causes strongyloidiasis; larvae penetrate skin from soil and can migrate to lungs before being swallowed to establish in the intestines.

• Clinical manifestations vary: immunocompetent patients may experience diarrhea and malabsorption while immunocompromised patients may face autoinfection with massive larval load leading to septicemia.

Cestode Infections

Taeniasis

• Taenia solium causes taeniasis via ingestion of contaminated food; larvae invade organs like the brain causing neurological symptoms.

Echinococcosis

• Echinococcus granulosus leads to hydatid disease through ingestion of eggs from dog feces resulting in cyst formation in liver or lungs.

Trichinosis

• Caused by Trichinella spiralis found in undercooked pork; larvae develop into adults in the intestine then spread to muscle tissue causing fever and myalgia.

Lymphatic Filariasis

• Caused by Wuchereria bancrofti or Brugia malayi transmitted by infected mosquitoes; manifests as chronic lymphatic inflammation leading to lymphedema (lymphatic filariasis).

Bioterrorism Implications

• Bioterrorism involves using biological agents for mass harm. Agents are classified into categories A (high transmission potential), B (easily disseminated), and C (emerging pathogens).

• Class A includes highly transmissible agents like smallpox virus.

• Class B includes less lethal but easily spreadable agents such as Brucella or cholera toxin.