ARBOVIRUSES AND ZOONOTIC DISEASES

ZOONOTIC DISEASES

• Definition: Zoonotic diseases are infections that can be transmitted between animals and humans.
    - Causative agents include:
      - Viruses
      - Bacteria
      - Parasites
      - Fungi

• Severity varies:
    - Some diseases can be severe and life-threatening (e.g., rabies).
    - Others may be milder, resolving on their own.

ARBOVIRAL ZOONOTIC DISEASES

• Definition: Zoonotic viruses that are capable of being transmitted from animals (arthropods, vertebrates) to humans.

• Transmission: Often via an infected arthropod vector, leading to the classification as arboviruses (arthropod-borne viruses).

Arbovirus Characteristics

• Definition: Arbovirus is not a specific family of viruses; it refers to any virus that is transmitted by certain arthropod species.

• Leading Arbovirus: The West Nile virus (WNV) is the primary cause of domestically acquired arboviral disease in the continental United States.

• Other notable arboviruses include:
    - La Crosse
    - Powassan
    - Jamestown Canyon
    - St. Louis Encephalitis

Arbovirus Diseases

Arbovirus List

• Dengue

• West Nile Virus

• Yellow Fever

• Zika Virus (ZV)

• Arenavirus

• Hantavirus Infection
    - New World hantaviruses cause hantavirus pulmonary syndrome in humans.
    - Old World hantaviruses typically cause hemorrhagic fever with renal syndrome in humans.

• Ebola Virus Infections
    - Transmitted by rats, only Ebola has specific treatment and a vaccine.

• Flavivirus
    - Transmitted by mosquitos.
    - Currently, no specific treatments are available for many arboviral diseases except for Dengue, which has a vaccine.

DENGUE VIRUS (FLAVIRIDAE/FAVIVIRUS)

• Etiological agent: The Dengue virus (DENV) is responsible for Dengue fever and its severe complications termed Severe Dengue.

• Serotypes: There are four distinct serotypes of DENV, differing in geographical distribution and associated diseases.

• Transmission:
    - DENV is vector-borne, transmitted by Aedes aegypti and Aedes albopictus.
    - Despite extensive eradication efforts, DENV remains prevalent in endemic regions.
    - Highest number of infections reported in 2019.

• Statistics:
    - Estimated 100-400 million infections occur yearly, with approximately 80% being asymptomatic.
    - Global warming has altered the traditional geographical distribution of Dengue.

SIGNS AND SYMPTOMS OF DENGUE

• Dengue Symptoms:
    - High fever (> 40°C / 104°F).
    - Severe headache.
    - Pain behind the eyes.
    - Nausea and vomiting.
    - Swollen glands or rash.
    - Muscle, joint pains, and chills.

• Severe Dengue Warning Signs:
    - Severe abdominal pain.
    - Persistent vomiting.
    - Bleeding gums.
    - Vomiting blood.
    - Rapid breathing.
    - Fatigue/restlessness.

• Hospitalization is required for severe cases, as they can lead to plasma leakage, shock, severe bleeding, and organ impairment.

MOSQUITO CONTROL STRATEGIES

• Mosquito Proliferation Control:
    - Eliminate stagnant water.
    - Cover all water tanks.

• Mosquito Bite Prevention:
    - Wear light-colored clothing and long sleeves.
    - Install screens on doors and windows.
    - Apply mosquito repellent per label instructions.

VIRUS PROPERTIES

GENOME AND STRUCTURE

• Viral Components:
    - 5' UTR and genomic RNA leading to different viral proteins including structural and non-structural proteins.

• Viral Lifecycle:
    - Entry: Virus binds to host receptors (e.g. mannose receptor, Fcγ receptor).
    - Replication: Viral RNA is released, translated, and replicated within the host cell.
    - Assembly and Maturation: Newly formed viruses are assembled and released.

HOST IMMUNE RESPONSE

• Initial Immune Activation:
    - Dengue can trigger a local immune response involving mast cells, macrophages, and dendritic cells.

• Adaptive Immunity:
    - Activated dendritic cells migrate to lymph nodes, stimulating further immune cell involvement.

PATHOGENESIS OF DENGUE

• Immunopathogenesis and Manifestations:
    - Virus variation and tropism.
    - Antibody-dependent enhancement.
    - Clinical manifestations like hemorrhage, thrombocytopenia, and plasma leakage.

DISEASE STATES

Dengue Fever

• Symptoms:
    - Flu-like, typically lasting 2-7 days post a 4-10 day incubation. Symptoms include high fever, headaches, and muscle pain.

Severe Dengue

• Critical Phase:
    - Occurs around day 3-7 after initial symptoms. A drop in fever can indicate severe dengue, requiring urgent medical attention.

LONG-TERM EFFECTS OF DENGUE

• Potential for autoimmune diseases and prolonged symptoms, including chronic joint pain and other complications.

DIAGNOSTICS

Testing Methods

• Various methods such as PCR for direct detection of the virus and serology for antibodies (IgM and IgG) are employed for diagnosis.

THERAPEUTICS

• Therapies include treatment aimed at symptom management, with no specific antiviral treatments available.

VACCINATION AND VACCINE CAVEATS

Dengvaxia Vaccine

• First vaccine approved by the U.S. FDA, designed to target all four dengue virus serotypes.

Concerns

• Issues surrounding the rushed development and associated risks in certain populations (e.g., children).

BRAZILIAN DENGUE VACCINE

• Butantan-DV: A single-dose vaccine with high effectiveness against severe dengue.

• Live-attenuated formulation targeting all serotypes, developed in collaboration with NIH.

CAN WE ERADICATE DENGUE VIRUS?

• Innovative strategies like genetically modified mosquitoes aim to suppress mosquito populations effectively.

CHIKUNGUNYA VIRUS

INTRODUCTION

• Known as Chicken Guinea, primarily spread by aggressive daytime-biting mosquitoes (Aedes species).

SYMPTOMS

• Majority symptomatic after infection, with primary symptoms being fever and severe joint pain.

TREATMENT AND CONTROL

• No vaccines available; management focuses on symptom relief.

ZIKA VIRUS

GENERAL INFORMATION

• First discovered in the Zika forest, with transmission primarily via Aedes species.

SYMPTOMS

• Commonly presents with fever, rash, joint pain, and conjunctivitis.

DIAGNOSIS AND TREATMENT

• Diagnosis through RT-PCR and serological tests; no specific treatments available.

COMPLICATIONS

• Linked to congenital microcephaly and Guillain-Barre syndrome.

OVERVIEW OF CURRENT THREATS

Vector-Associated Viruses

CASE STUDY OF DENGUE

• Example of a patient diagnosed with severe dengue complications and secondary infections, underlining challenges in diagnosis and treatment when presentations vary.