BSMLS 3F Mycology & Virology 2022-2023 Lecture Notes PDF

BSMLS 3F MYCOLOGY & VIROLOGY 2022 - 2023 MLS 415 | LECTURE | FINALS LESSON 17: TOGAVIRUS & FLAVIVIRUS ARTHROPOD & RODENT-BORNE VIRUSES The virus replicates in the skin then disseminates to Represent ecological groupings of viruses the liver, joints, and blood Have diverse physical and chemical prope...

BSMLS 3F MYCOLOGY & VIROLOGY 2022 - 2023 MLS 415 | LECTURE | FINALS LESSON 17: TOGAVIRUS & FLAVIVIRUS ARTHROPOD & RODENT-BORNE VIRUSES The virus replicates in the skin then disseminates to Represent ecological groupings of viruses the liver, joints, and blood Have diverse physical and chemical properties Incubation period is 2-4 days Classified in several virus families In susceptible vertebrae host, primary viral TOGAVIRUS (CHIKUNGUNYA) multiplication occurs in myeloid and lymphoid cells, and vascular endothelium RNA virus Virus goes to the lymph node and other tissues via Family: Togaviridae the circulatory system. Replication at other tissues Common name: Togavirus lead to the viremic phase of the disease Includes Rubella Virus and Alpha Viruses, a large Multiplication on CNS would depend on the ability of group of mosquito-borne arboviruses the virus to cross the blood-brain barrier CLASSIFICATION & STRUCTURE Viremia may occur for several days then, the virus Genus: Alphavirus would enter the bloodstream, which would lead to Spherical, 70 nm in diameter, nucleocapsid has 42 dissemination capsomeres CHKV indirectly triggers the activation of an innate Genome: positive-sense, single stranded RNA, 11-12 immune response kb in size Type 1 interferon (IFN) is produced via activation of Enveloped non-hematopoietic cells, including primarily Three or four major structural polypeptides, two fibroblasts and the transcription of cytokines and glycosylated chemokines PATHOGENESIS ANTIGENIC STRUCTURE CHKV has two surface proteins: Transmembrane glycoprotein E1 and E2 o Allows the virus to enter the host, spread out, and cause infection in host cells o E1 is a class II viral fusion protein o E2 mediates cell attachment TRANSMISSION CHKV is transmitted in two cycles: URBAN AND SYLVATIC Urban Cycle – from human to mosquito to human transmission Sylvatic Cycle – from an animal (wild animal) to mosquito to human Major Host – Humans Principal Vectors – Aedes aegypti and Aedes albopictus Viral Tropism – Human epithelial cells, endothelial cells, fibroblasts, monocyte-derived macrophages EPIDEMEOLOGY Prior to 2013, Chikungunya virus cases and outbreaks have been identified (E.g., Africa, Asia, Europe, Indian and Pacific Ocean) Transmission is rarely from mother to child, but it may occur through infected blood handling Aerosol exposure in the laboratory – possible to acquire the infection ROUTE OF INFECTION Transmission occurs after a bite by an infected A. aegypti and A. albopictus mosquito CLINICAL MANIFESTATIONS Joint pain (in 92% cases) – disabling o Recovery: 1 week, but may persists INTERN CUTIEE 65 years old), people with o Remove any stagnant water where the underlying conditions mosquitoes can lay their eggs. Once infected, an individual will get immunity FLAVIVIRUS (DENGUE) COMPLICATIONS RNA virus Exposure and infection of pregnant women. Virus Family: Flaviviridae may infect developing fetus causing multiple Common name: Flavivirus congenital anomalies Include viruses that cause arbovirus diseases, such Infections occurs later in pregnancy may result in as Zika (Zika fever or disease), yellow fever, dengue, splenomegaly and osteomyelitis among other birth West Nile viral encephalitis, and Japanese and St. defects. Louis encephalitis Intrauterine infection during first trimester may result CLASSIFICATION AND STRUCTURE in: Low birth weight, mental retardation, deafness, Genus Flavivirus congenital heart disease, and neurologic defects Spherical, 40-60 nm in diameter Death is rare Genome: positive-sense, single stranded RN, 11 kb LABORATORY DIAGNOSIS & IDENTIFICATION in size IDENTIFICATION Genome RNA infectious Viral isolation attempts require appropriate biosafety precautions Envelope For direct detect antigen detection and polymerase Three structural polypeptides, two glycosylated chain reaction (PCR) assays are available PATHOGENESIS ANTIGENIC STRUCTURE Togavirus disease is diagnosed through detection of specific serum IgG and IgM antibodies Composed of antigenically distinct serotypes: DENVSEROLOGY 1 through DENV-4 TRANSMSISSION Detect virus-specific IgM in serum or CSF o ELISA IgM-capture ELISA Transmitted through a bite of an infected female o Microsphere-based immunoassays Aedes mosquito o IgG ELISA Primary reservoir: Humans To confirm a diagnosis, collect 2 serum samples Major Vectors: Aedes aegypti and Aedes albopictus o First sample of serum should be taken as soon ROUTE OF INFECTION after the onset as possible After a bite of an infected female Aedes mosquito, ▪ To identify whether the patient has antibodies DENV has an incubation period of 3-14 days against the causative agent Viral replication takes place within the cells of the o Second sample 2– 3 weeks later mononuclear phagocyte lineage, target dendritic ▪ Identify if the patient was able to create cells, macrophages, hepatocytes, and endothelial antibodies against the causative agent cells Consider cross-reactivity within the alphavirus or Infected cells migrate from the site to the lymph nodes flavivirus group in making the diagnosis because Viremia develops within 24 hours where the virus antibodies to other members may also appear after a travels through the body in severe cases, there is a single infection by one member of the group very high viral load affecting many vital organs TREATMENT Virus infected macrophages produce signaling There is currently no vaccine to treat Chikungunya proteins: Interferons, Cytokines, Chemokines, TNF virus infection. and others Supportive care INTERN CUTIEE