Arbovirus Lesson 24B PDF

OUTLINE # ARBOVIRUS I. Overview A. Transmission B. Pathogenesis and Pathology C. Diseases Caused D. Diagnosis E. Prevention and Control II. Togaviridae A.Chikungunya 1. Characteristics 2. Host response 3. Clinical features 4. Laboratory identification 5. Treatment 6. Prevention and control 7. Epid...

OUTLINE # ARBOVIRUS I. Overview A. Transmission B. Pathogenesis and Pathology C. Diseases Caused D. Diagnosis E. Prevention and Control II. Togaviridae A.Chikungunya 1. Characteristics 2. Host response 3. Clinical features 4. Laboratory identification 5. Treatment 6. Prevention and control 7. Epidemiology III. Bunyaviridae A.Rift Valley Fever Virus 1. Characteristics 2. Epidemiology 3. Transmission 4. Diagnosis 5. Treatment and prevention IV. Flaviviridae A.Yellow Fever Virus 1. Characteristics 2. Clinical features 3. Diagnosis 4. Treatment and prevention B.Japanese Encephalitis 1. Characteristics 2. Clinical features 3. Diagnosis 4. Treatment and prevention 5. Epidemiology DENGUE A. Characteristics B. History C. Epidemiology D. Viral characteristics E. Replication and transmission F. Clinical manifestations G. Phases of Dengue virus infection H. Risk factors for DHF I. Diagnosis J. Treatment K. Prevention and Control L. Vaccine M. Immunity and immune response V. Review questions VI. Appendix 1 1 1 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 7 7 8 8 9 9 10 10 10 10 11 12 SOURCES ● Batch Trans 2024. Arbovirus. https://drive.google.com/drive/u/0/folders/1XUKElR-u5GH 58yi6qg7RSvZumKr7h1pa ● Lacuna, A.R. (2023). Arbovirus [Lecture Video]. https://www.youtube.com/watch?v=91zjwa1ewx8&t=680s ARBOVIRUS OVERVIEW ● Arthropod-borne viruses ● Transmitted by blood-sucking arthropods from one host to another during the viremic stage May cause lifelong infection without signs of damage or disease ● Perpetuates in the environment due to Transovarian transmission in arthropods ● Natural Reservoirs: ○ Animals, birds, and even reptile ● Accidental Hosts ○ Man ● Vectors: ○ blood-sucking arthropods (mosquitoes, sandflies, ticks) that consume the blood of vertebrates (for nutrition and development) ● Found in all tropical and temperate zones, but are more prevalent in hotter than in cooler countries ● Existed even in the olden times ● Dr. Carlos Finlay (1881) proposed the connection between disease and arthropods ● Viruses maintain themselves in nature by going through a cycle between a host (carrier of virus) and an arthropod vector (carrier and transmitter of virus). TRANSMISSION ● Virus is transmitted through the saliva of arthropods that come in contact with the blood of hosts during the biting process ● Undergoes amplification (viral replication) inside the host causing viremia Figure 1. Transmission of Arbovirus [Lacuna, 2023] ● Other possible modes of transmission: ○ Person-to-person (uncommon) ○ Blood transfusion: ■ Food transfusion, use of blood products, and organ transplantation, especially if the virus is present in the donor’s blood/organs ○ Vertical transmission and breastfeeding ■ Rare, but may occur ○ Used needles: ■ Possible, especially if used by infected person or animals) ● There are two cycles, but both may be seen with some arboviruses such as yellow fever. MAN-ARTHROPOD-MAN ● Reservoir hosts may be either man or arthropod vectors (e.g. Mosquito bites a human, and transfers the virus to another human.) ● Also known as the “Urban Cycle” ● Transovarial transmission may occur in arthropods, wherein the vector transfers the virus to offspring, causing outbreaks PH152::MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 1 PATHOGENESIS AND PATHOLOGY ● Viral multiplication occurs in myeloid and lymphoid cells or the in vascular endothelium ● As the virus enters the bloodstream, it is disseminated and different tissues support its replication. ● Multiplication in the CNS depends on its ability to cross the blood-brain barrier and infect the nerve cells. ● Virus infection is usually controlled before neuroinvasion. ● Factors for neuroinvasion (usually immunocompromised): ○ Genetic background of the host ○ Host innate and adaptive response ○ Virulence of the virus ○ Examples: Dengue, Urban yellow fever. Figure 2. Man-Arthropod-Man transmission [Lacuna, 2023] ANIMAL-ARTHROPOD VECTOR-MAN ● Virus is maintained in nature in a transmission cycle involving the arthropod vector and animal ○ The animal is the reservoir host ○ Man becomes infected accidental ● Also called as the “Sylvatic Cycle” or sometimes the “Jungle Cycle” ○ Examples: ■ Japanese Encephalitis (JE) ■ Eastern Equine Encephalitis (EEE) ■ Western Equine Encephalitis (WEE) ■ Jungle Yellow Fever DISEASES CAUSED ● Most arboviral diseases have similar symptoms which appear a few days to two weeks after being bitten by an infected mosquito or tick. ○ Begin with diarrhea, vomiting, and body aches, fever and rashes (uncomplicated). Due to the similarities of these symptoms in the first days or week, the exact infection cannot be determined in this period. Usually, it may also depend on the endemicity of the virus (circulating within a region or location) (Lacuna, 2023). ● If disease progresses, viruses can cause encephalitis (EEE, WEE, St Louis encephalitis, Japanese encephalitis) [From Batch 2024 Trans] ○ headaches, neck stiffness, excessive sleepiness, seizures, or unconsciousness ● Haemorrhagic fever or manifestations (e.g. Dengue, Yellow Fever, Crimean-Congo Hemorrhagic Fever) Figure 3. Animal-Arthropod-Man transmission [Lacuna, 2023] DIFFERENT GROUPS OF ARTHROPOD VECTORS Mosquitoes Ticks Sandflies ● Japanese ● Crimean-Congo ● Sicilian sandfly encephalitis haemorrhagic fever ● Dengue Fever ● Rift valley fever ● Yellow Fever ● Various tick-borne ● St. Louis encephalitis Encephalitis, ● EEE ● WEE ● VEE ● Chikungunya Figure 4. Examples of Arthropod Vectors [Lacuna, 2023] ANIMAL RESERVOIRS Birds Japanese encephalitis, encephalitis, EEE, WEE St Louis Pigs, Buffaloes Japanese encephalitis Monkeys Yellow Fever Rodents VEE, Russian Spring-Summer encephalitis DIAGNOSIS ● Serology - usually used to make a diagnosis of arbovirus infections. ○ IgM detection is indicative of recent infection ○ IgG interpretation needs 2 samples with at least 5 days apart to show a rise in antibody titre. ○ Hemagglutination Inhibition (seldomly used nowadays as technology develops)[From Batch 2024 Trans] ○ ELISA ● Direct detection tests ○ Detection of antigen and nucleic acids: Real Time RT-PCR for dengue, JE, ChikV, YF) ○ Culture - a number of cell lines may be used, including mosquito cell lines (C6/36 cells) ■ Tedious and expensive ■ Need living host ○ Animals- Intracerebral inoculation of suckling mice or hamsters may be used for virus isolation by taking out the brain and identify the propagated virus PREVENTION AND CONTROL ● Surveillance - disease and vector populations ● Control of vector - pesticides, elimination of breeding grounds ● Personal protection - screening of houses, bed nets, insect repellants ● Vaccination - available for a number of arboviral infections Yellow fever, Japanese encephalitis, Russian tick-borne encephalitis ○ There are still many other arboviral infections that have no vaccination ● Gene editing in mosquito (being developed) ● Three most renowned approaches to health. ○ One Health ○ Eco-Health ○ Planetary Health interdisciplinary and holistic PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 2 ● Multiple factors, including socioeconomic, medical (i.e., misdiagnosis and misclassification), and climatic factors such as temperature and humidity influence the constant distribution of arthropod vectors. Research findings underline the need for a holistic approach as the best strategy to mitigate and control arboviruses' transmission (Lacuna, 2023). USE OF WOLBACHIA ● Wolbachia is a common type of bacteria found in insects ■ Not found in Ae. aegypti mosquitoes. ● How mosquitoes with Wolbachia are used to control Ae. aegypti mosquitoes (still not practiced in the Philippines) ○ Wolbachia bacteria are introduced into Aedes aegypti mosquito eggs. Figure 8. A person infected with Chikungunya fever[Lacuna, 2023].. HOST-RESPONSE ● Incubation Period: 1-12 days ● Symptoms: ○ Sudden onset of chills ○ Acute fever (3-7 days) ○ Headache ○ Rash (petechial or maculopapular) on the trunk and occasionally on the limbs ○ Arthralgia that affects the joints of the extremities (up to 3 weeks) Figure 5. Introduction of Wolbachia Bacteria into Aedes aegypti [Lacuna, 2023] ○ When male Aedes aegypti mosquitoes with Wolbachia mate with wild female mosquitoes that do not have Wolbachia, the eggs will not hatch. ○ Male mosquitoes with Wolbachia are released regularly into an area by mosquito control professionals. Figure 9. Rash on trunk of a person infected with Chikungunya [Lacuna, 2023] Figure 6 Breeding of male and female Aedes aegypti mosquito CLINICAL FEATURES ● Children ○ Maculopapular rash ○ Gingival hemorrhage ○ Secondary rise in temperature ○ Severe in infants ● Complications ○ Myelomeningoencephalitis ○ Guillan-barre syndrome ○ Hepatitis ○ Myocarditis ○ Pericarditis [Lacuna, 2023] See Table 1 for the Summary Table of Family of Arboviruses TOGAVIRIDAE ● Spherical, 70 nm diameter ● Icosahedral nucleocapsid: 42 capsomeres ● Genome: (+) sense, ssRNA; 11- 12 kb ● Enveloped; 3 or 4 major structural glycosylated) polypeptides (2 Figure 7. Togaviridae- Alphavirus [Lacuna, 2023] Figure 10. Rashes on trunk of a child infected with Chikungunya [Lacuna, 2023] CHIKUNGUNYA CHARACTERISTIC ● A relatively rare form of viral fever (“Debilitating non-fatal viral illness”) ● Makonde language: “that which bends up” ○ Affected patient’s posture ○ Excruciating pain in the joints ● Found in Africa, India, Southeast Asia ● Vector: Aedes (Aedes aegypti, Aedes albopictus), Culex, and Mansonia species ● Reservoirs: monkeys and other vertebrates LABORATORY FINDINGS ● Clinical findings are not outstanding ● Virus Isolation ○ Most definitive ○ Involves exposing specific cell lines to samples from whole blood and identifying Chikungunya virus-specific responses ● Serological test ○ ELISA - measures Chikungunya-specific IgM levels ● RT-PCR ○ Uses nested primer pairs to amplify several Chikungunya-specific genes from whole blood PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 3 TREATMENT ● Supportive treatment: analgesic and anticonvulsants ○ Self-limiting ○ Mortality rate ○ Absence of antiviral therapy ○ Treatment supportive ○ Some may require hospitalization PREVENTION AND CONTROL ● No vaccines or antiviral available ● Depends on surveillance, early identification of outbreaks, and vector control (insecticides) ● Mosquito repellents and a screened doors and windows ● Public Health measures ○ Monitoring and reporting of fever cases ○ Surveillance and case detection ○ Vector surveillance and control ○ Training of health service providers ○ Media EPIDEMIOLOGY ● Human-mosquito cycle ● Sylvatic cycle-monkeys ● Very few recorded fatalities Figure 12. Rift Valley Fever virus under the microscope[Lacuna, 2023] EPIDEMIOLOGY ● Africa, Middle East ● 1900s: first recognized in sheep ● 1930: agent isolated ● Intermittent outbreaks in Kenya ○ 1950-1951: major epizootic ○ 500,000 sheep abortions ○ 100,000 sheep deaths ● Middle East - Saudi Arabia/Yemen Figure 11. Countries and territories where chikungunya cases have been reported [Lacuna,2023] BUNYAVIRIDAE RIFT VALLEY FEVER VIRUS Figure 13. Epidemiology of the Rift Valley Fever Virus Lacuna, CHARACTERISTICS ● Acute febrile disease ○ Sheep, cattle, goats ○ High abortion rates and death in young ● Can affect humans (fever, headache, myalgia - progress to hemorrhagic symptoms or meningoencephalitis or affect eye associated with heavy rainfall) ● Arthropod vector: mosquito (most common) ● Phlebovirus (Bunyaviridae) ● 3s RNA virus ● Vector: mosquito ● Stable at: ○ -60 C to 23 C ○ 50 to 85% relative humidity ● Inactivation: ○ Lipid solvents ○ Detergents ○ Low pH Figure 14. Distribution of Rift Valley Fever virus [Lacuna, PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 4 TRANSMISSION ● Arthropod vector: Mosquitoes ○ Aedes ○ Anopheles ○ Culex ● Biting flies: possible vectors ● Direct contact with blood/eat of slaughtered animals ○ E.g. cattle/sheep CLINICAL FEATURES ● Classical presentation: ○ Chills ○ Fever ○ Headache ○ Generalized myalgias ○ GI complaints ● Some patients may experience an asymptomatic infection or mild undifferentiated febrile illness ● After 3 to 4 days, severely ill patients with classical Yellow Fever course will develop bradycardia (Faget’s sign), jaundice, and haemorrhagic manifestations ● 50% of patients will develop fatal disease characterized by severe hemorrhagic manifestations, oliguria, and hypotension DIAGNOSIS ● Serology TREATMENT AND PREVENTION ● No specific antiviral treatment ● Live attenuated vaccine is available and used for persons living in or traveling to endemic areas (can last up to 10 years) Figure 15. Aedes (arthropod vector of the Rift Valley Fever virus) [Lacuna, 2023] DIAGNOSIS ● RT-PCR ● Enzyme-linked Immunoassay (ELISA) ● Culture ○ Sample: blood and tissues TREATMENT AND PREVENTION ● No FDA-approved treatment ○ Most cases are mild and self-limiting ● Avoid contact with blood, body fluids, or tissues of infected animals ○ People working with animals in endemic areas should wear appropriate protective equipment ■ Gloves, boots, long sleeves, and a face shield ● Use only safe animals products ○ All animal products (including meat, milk, and blood) should be thoroughly cooked before eating or drinking ● Protect yourself against mosquitoes and other blood-sucking insects ● No vaccines are currently available FLAVIVIRIDAE ● Causes a wide range of clinical symptoms that include hemorrhagic fever and encephalitis ● Spread by a mosquito vector that affects humans and birds Figure 17 Yellow Fever Maps[Lacuna, 2023] JAPANESE ENCEPHALITIS CHARACTERISTICS ● First discovered and originally restricted to Japan ● Large scale epidemics occur in China, India, and other parts of Asia ● Flavivirus: transmitted by Culex mosquitoes ○ Maintained in nature by transmission cycle involving mosquitoes, birds, and pigs Figure 18. Culex mosquito as a transmitter of Flavivirus[Lacuna, 2023] Figure 16. Morphology of Yellow Virus Fever[Lacuna, 2023] YELLOW FEVER VIRUS CHARACTERISTICS ● Flavivirus ● Mainly found in West Africa and South America ● 2 major forms: Urban and Jungle (sylvativ) yellow fever ○ Jungle Yellow Fever: natural reservoir of the disease ○ Urban form: transmitted between humans by the Aedes aegypti mosquito PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 5 EPIDEMIOLOGY Figure 19. Animal-Arthropod Man Cycle [Lacuna, 2023] CLINICAL FEATURES ● Most human infections are subclinical: the inapparent to clinical cases is 300:1. ● In clinical cases, life-threatening encephalitis occurs ● After infection, the virus generally multiplies for 5 to 15 days (incubation period) followed by: ○ Initial symptoms: ■ Fever ■ Headache ■ Vomiting ○ In the next few days, other symptoms develop: ■ Mental status changes ■ Neurologic issues ■ Weakness ■ Movement disorders ■ Seizures (common in children) Figure 22. Geographic Distribution of Japanese Encephalitis Virus Lacuna, 2023] DENGUE CHARACTERISTICS ● “Break-bone fever” ○ Causes severe bone and muscle pain ● Mosquito-borne febrile illness ○ Occurs primarily in tropics but with a worldwide distribution ● Found in tropical and subtropical regions, predominantly in urban and semi-urban areas ● Before, it was absent in Europe and Antarctica but now the disease is currently surging in parts of southern Europe ○ Due to climate change, causing a global increase in temperature ● Vector: Mosquito ○ Aedes aegypti ○ Aedes albopictus 4 MAIN DENGUE SEROTYPES ● Dengue 1, 2, 3, 4 ● Repeated infection with another serotype, especially serotype 2 predisposes one to dengue hemorrhagic fever (DHF) ○ Causes of hemorrhage or shock, especially in children with a mortality rate of almost 10% “Dengue is one disease entity with different clinical presentations and often with unpredictable clinical evolution and outcome.” - Dengue expert consensus groups in Latin America, SEA, and WHO headquarters in Switzerland Figure 20..Clinical Features Representation of Japanese Encephalitis[Lacuna,2023] DIAGNOSIS ● Serology ○ ELISA tests to identify IgM antibodies in serum and CSF TREATMENT AND PREVENTION ● No specific therapy is available ● Vaccine: available Figure 21. Japanese Encephalitis Vaccine Lacuna, 2023 HISTORY ● 1779-1780 ○ First reported epidemics in Asia, Africa, and North America, generally with long intervals (10-40 years) between major epidemics ● After World War II ○ Dengue pandemic began in Southeast Asia ■ Epidemics due to multiple serotypes became more frequent ■ Geographic distribution expanded ■ DHF appeared in 1950 and became a frequent cause of hospitalization and death among children in 1975 EPIDEMIOLOGY ● Present in Africa, the Americas, Asia, the Caribbean, and the Pacific ● In 2020, France and Italy reported autochthonous dengue cases ● In 2020, the five countries reporting the most cases are Brazil, Paraguay, Mexico, Vietnam, and Malaysia ] PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 6 ● 4 serotypes ○ Infection with one provides lifelong immunity for it but only partial protection from the other three ■ DENV-1 ■ DENV-2 ■ DENV-3 ■ DENV-4 ● Severe complications to secondary infections of: ○ DENV-2 or DENV-3 from someone with previous DENV-1 infection; and ○ DENV-2 from previous DENV-3 infection Figure 23. Geographical Distribution of the Four Dengue Serotypes in 1970[Lacuna, 2023].. Albert Sabin speciated dengue viruses in 1944 TWO CYCLES ● Jungle Cycle (Sylvatic/Enzootic) ● Urban Cycle (Epidemic) Figure 24. Geographical Distribution of the Four Dengue Serotypes in 2000-2013[Lacuna, 2023].. Figure 27. Urban and Jungle Cycle of Dengue [Lacuna, 2023]. Figure 25. Geographical Distribution of the Four Dengue Serotypes in 2020[Lacuna, 2023].. ● In the Philippines, during epidemiologic week 2023, 893 new dengue cases were reported ● As of August 26, 2023 a total of 111,813 cases have been reported ○ 26% lower than 2022 of the same period ● A total of 421 death was recorded which was lower than 556 deaths recorded in 2022 of the same period ● Observed as a usual pattern of dengue wherein it would be lower or higher than the previous year Figure 26. Reported Dengue Cases by Morbidity Week Philippines, January 1, 2023 (MW 1) - August 26, 2023 (MW 34) [Lacuna, 2023].. AEDES AEGYPTI ● Dengue transmitted by infected female mosquitoes ○ Lives an average of 30 days ○ Females may lay up to 150-200 eggs at a time (females pass the virus to the eggs) ○ Primarily a daytime feeder and endophagic feeder (indoors) ■ Prefers to bite indoors ○ Lives around human habitation ○ Lays eggs and produces larvae preferentially in artificial containers with water (common in urban settings) ○ Appearance: Small, dark mosquito with white lyre-shaped markings and banded legs See Figure 38 in Appendix for the Comparison of Dengue Vectors REPLICATION AND TRANSMISSION ● When mosquitoes mate ○ Imago Adult Insect: A female mosquito needs to suck blood for egg production which occurs immediately after mating ○ Egg: Female mosquito lays eggs, oviposition, slightly above the water level ○ When covered with water, larvae emerge from eggs ○ Larva: first larval stage, second larval stage, third larval stage, and fourth larval stage ■ Moulting between each stage ○ Pupa: Adult emerges from the pupa ○ Mating of adult mosquitoes VIRAL CHARACTERISTICS ● Enveloped, 40-60 nm in diameter ● (+ve) ssRNA Virus ● Genetically similar, but antigenically distinct VIRAL PROPERTIES ● 3 protein molecules that form the virus particle ○ C, prM, E ● 7 other proteins (found in the infected host cell) ○ NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5 Figure 28. Life cycle of dengue virus vector Aedes aegypti [Lacuna, 2023]. PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 7 ● When mosquitoes bite humans ○ Virus transmitted to humans through mosquito saliva ○ Virus replicates in target organs ○ Virus infects white blood cells and lymphatic tissues ○ Virus released and circulates in blood ○ Second mosquito ingests the blood with the virus ○ Virus replicates in mosquito midgut and other organs, infects salivary glands ○ Virus replicates in salivary glands ■ Ready to be injected and inoculated to another person ○ Abdominal Pain ○ Persistent Vomiting ○ Breathing Difficulty ○ Bleeding ○ Potentially lethal complication (mostly in children) ● Early clinical diagnosis and careful clinical management increases survival CATEGORIES OF SYMPTOMATIC DENGUE VIRUS ● Undifferentiated Fever ● Dengue Fever (DF) ● Dengue Hemorrhagic Fever (DHF) ○ Further classified into 4 severity grades (grades III and IV are dengue shock syndromes or DSS) ○ Severe dengue - characterized by plasma leakage, hemoconcentration and abnormalities in homeostasis ● Mechanisms leading to severe illness are not well understood but immune response, genetic background of the patient, and virus characteristics may contribute ○ Severe dengue can be detected through blood tests or CBC ○ Hemoconcentration = high hematocrit [From Batch 2024 Trans] (indicator of plasma leakage) ○ Prolonged bleeding time indicates abnormalities Figure 29. Replication and transmission of dengue in the human body [Lacuna, 2023]. ● Dengue whole cycle in humans and mosquitoes ○ Viremia in infected human (4-6 days) ○ When a mosquito bites an infected human (7-12 days) ■ The virus passes in the intestine in the mosquito where the virus multiplies ■ Virus migrates to the salivary glands ○ Mosquito bites human, starts cycle in human (3-7 days) ■ Until viremia starts again Figure 31. Symptoms of dengue fever [Lacuna, 2023]. Figure 30. Replication and transmission of dengue cycle [Lacuna, 2023]. CLINICAL MANIFESTATIONS ● Febrile illness affecting infants, young children, and adults ○ General symptoms in adults are often neglected or not associated to dengue ● Symptoms appear 3-14 days after the infective bite ● Symptoms range from: ○ Mild fever to incapacitating high fever with severe headache ■ Severe headache prevents patients from falling asleep ○ Pain behind the eyes, ■ Classical symptom of dengue ○ Muscle and joint pain ■ Resonates dengue as "Break Bone Fever" ○ Rash ● Severe Dengue (Dengue Hemorrhagic Fever) ○ Fever PHASES OF DENGUE VIRUS INFECTION 1. FEBRILE PHASE ● Sudden high-grade fever (acute febrile phase) ● Lasts 2-7 days and often accompanied by facial flushing, skin erythema, generalized body ache, myalgia, arthralgia, and headache ● Common Symptoms ○ Anorexia ○ Nausea ○ Vomiting ● Symptoms for some patients[From Batch 2024 Trans] ○ Sore throat ○ Injected pharynx ○ Conjunctival injection ● Difficult to distinguish dengue from non-dengue febrile diseases at this stage ● Enlarged and tender liver after a few days of being febrile ● Progressive decrease in total WBC count 2. CRITICAL PHASE ● Temperature drops to 37.5-38°C or less and remains below this level, usually on days 3-7 of illness ● Increase in capillary permeability with increasing hematocrit levels ○ It is important to monitor hematocrit levels to detect the critical phase of infection when temperature drops ○ Patients without increased capillary permeability will improve while those with increased permeability will become worse ○ Capillary permeability causes plasma leakage PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 8 ● Period of clinically significant plasma leakage lasts 24-48 hours ○ Shock results from critical loss in plasma volume due to leakage ■ Subnormal body temperature ■ Metabolic acidosis and DIC (Disseminated Intravascular Coagulopathy) ■ Leads to severe hemorrhage causing decrease in hematocrit ○ At this point, it should be managed properly ● Chest x-ray and abdominal UTZ are useful for diagnosis at this stage due to presence of pleural effusion and ascites ● Severe organ impairment ○ Severe hepatitis, encephalitis or myocarditis and/or severe bleeding may develop even without plasma leakage or shock 3. RECOVERY PHASE ● Gradual reabsorption of extravascular compartment fluid takes place in the next 48-72 hours (if the patient survives the 24-48-hour critical phase) ○ At this point, the immune system controls the virus ● Improvement of general well-being, recovery of appetite, stabilization of hemodynamic status, and diuresis happens (usually self-limiting) ● Hematocrit may stabilize or may decrease due to the dilutional effect of reabsorbed fluid ● WBC may start to rise but recovery of platelet count is lesser ● Respiratory distress from massive pleural effusion and ascites may occur at any time if excessive IV fluids have been administered ● Excessive fluid therapy – associated with pulmonary edema or congestive heart failure ○ On the other hand, lack of IV fluids administered may lead to dengue shock syndrome[From Batch 2024 Trans] ○ Major bleeding - almost always associated with profounds shock and is in combination with thrombocytopenia, hypoxia and acidosis, which can lead to multiple organ failure and advanced DIC ● Unusual manifestations: ○ Acute liver failure ○ Encephalopathy ○ Cardiomyopathy (in few dengue cases) ○ Encephalitis (In few dengue cases) ● Most deaths occur in patients with profound shock, especially in cases with fluid overload ● Severe dengue should be considered if the patient is a resident of high-risk area and has 2-7 days fever plus any of the following: ○ Evidence of plasma leakage (high hematocrit, pleural effusions or ascites, circulatory compromise or shock) ○ Significant bleeding ○ Altered level of consciousness (lethargy or restlessness, convulsions, coma) ○ Severe gastrointestinal involvement (persistent vomiting, increasing or intense abdominal pain, jaundice) ○ Severe organ impairment RISK FACTORS FOR DENGUE HEMORRHAGIC FEVER (DHF) ● Virus Strain ● Pre-existing anti-dengue antibody ○ Previous infection ○ Maternal antibodies in infants ● Host Genetics ● Age ● Higher risk in secondary infections ● Higher risk in locations with two or more serotypes circulating simultaneously at high levels (hyperendemic transmission) ○ Surveillance is key NOTE Replacement or administration of IV fluids for management of pleural effusion, capillary permeability, and plasma leakage must be monitored in the recovery phase. It must be decreased in this phase in order to reduce the risk of complications (e.g., major bleeding, profound shock, death).[From Batch 2024 Trans] 4. SEVERE DENGUE ● Occurs if patient has not recovered ● Defined by one or more of the following: ○ Plasma leakage leading to shock and/or fluid accumulation, with or without respiratory distress ■ Severe bleeding ■ Severe organ impairment ● Vascular permeability progresses, hypovolemia worsens, leads to shock (usually takes place around defervescence or days 3-7 of illness) ● Produces tachycardia and peripheral vasoconstriction with reduced skin perfusion, leading to cold extremities and delayed capillary refill time ● Patient is in shock if pulse pressure (difference between systolic and diastolic pressures) is less than or equal to 20 mmHg in children and has cold extremities, delayed capillary refill or rapid pulse rate ○ Adults: pulse pressure of less than or equal to 20 mmHg may indicate a more severe shock ○ Hypotension complicated with major bleeding is associated with prolonged shock ○ The blood pressure of the patient is monitored every 2 hours (every 1 hour if the patient is in the ICU) [From Batch 2024 Figure 32. Increased probability of DHF [Lacuna, 2023] Figure 33. WHO criteria for Dengue and Severe Dengue and Dengue warning signs[Lacuna, 2023] Trans] ● Coagulation abnormalities, but not sufficient to cause major bleeding PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 9 DIAGNOSIS ● Blood pressure ○ Usually low in Severe Dengue ● Evidence of bleeding in the skin or other sites ● Hydration status ○ Increased hematocrit levels ● Evidence of increased vascular permeability ○ Pleural effusion ○ Ascites ● Tourniquet test ○ Positive test: 20 or more petechiae per 1 inch2 (6.25cm2) ○ Apply BP cuff with 20 mmHg for 15 mins. When removed, petechiae are seen below the arm ● Clinical laboratory tests ○ CBC: WBC, low platelets, high hematocrit ○ Albumin ○ Liver function tests ○ Urine: check for microscopic hematuria ● Dengue-specific tests ○ Serology ○ Virus isolation ■ Not usually performed since it is tedious and takes long ■ Mosquito antigen or virus is made to react with an antibody labeled with fluorescent dyes ■ Antigens may be observed under a fluorescent microscope Figure 34. Virus isolation [Lacuna, 2023] ● ELISA ○ Dengue IgG Indirect ELISA: detection of past/active dengue infection ○ Dengue IgM Capture ELISA: diagnosis of active dengue infection ○ Dengue IgG Capture ELISA: diagnosis of secondary dengue infection ○ Test to be used depends on the stage of disease ○ There are kits where IgM and IgG are being detected Figure 35. ELISA [Lacuna, 2023] ● Dengue rapid test strip ○ Results in 15 minutes ○ Presumptive Differentiation between primary and secondary dengue infection ○ Test strips are individually packed ○ No special training required. Simple and easy to use ○ Built-in control zone: there should always be a band to indicate that the test worked properly ○ Buffer solution for better flow ■ G(-), M(-): Negative ■ G(-), M(+): IgM Positive, Primary Dengue ■ G(+), M(+): IgM and IgG Positive, Secondary Dengue ■ G(+), M(-): IgG Positive, Secondary Dengue Figure 36. Dengue rapid test strip [Lacuna, 2023] TREATMENT ● Supportive treatment: ○ Mild cases: oral or intravenous rehydration ○ Severe cases: Intravenous fluids and blood transfusion ■ Blood transfusion and oxygen for patient with severe blood loss ● Drugs to lower the fever and reduce pain ● Bed rest to help the body recover PREVENTION AND CONTROL ● Environmental sanitation ○ Clean or remove breeding sites ● Vector control ○ Insecticides and larvicides ● Personal protection ○ Mosquito repellents, mosquito nets and well-screened doors and windows VACCINE ● Candidate vaccines are still under development ● Vaccine development is difficult because the vaccine must provide protection against all 4 serotypes ● Problems: ○ Viruses grow poorly in cell culture ○ No reliable animal model for DHF ● DengvaxiaⓇ (CYD-TDV) [From Batch 2024 Trans] ○ Developed by Sanofi-Pasteur ○ First dengue vaccine to be licensed ○ First licensed in December 2015 (Mexico) ○ For 9-45 years old (endemic areas) ○ Live recombinant tetravalent dengue vaccine ○ Given in 3 doses (0/6/12 month schedule) IMMUNITY AND IMMUNE RESPONSE PRIMARY INFECTION IMMUNE RESPONSE – 1° ● IgM antibodies ○ Produced approximately 5 days after symptoms appear ○ Rise for 1-3 weeks and may persist for up to 60 days ○ May be detectable for up to 6 months ● IgG antibodies ○ Appear approximately 14 days after onset of symptoms and persists for life SECONDARY INFECTION IMMUNE RESPONSE – 2° ● IgM antibodies ○ May not be produced until 20 days after onset of infection ○ May be produced at low or undetectable levels or for a shorter period than in a primary infection ● IgG antibodies ○ Rise rapidly 1-2 days after onset of symptoms ○ Reach levels above that those found in primary or past infection ○ Persist at high levels for 30-40 days, then decline to levels found in primary or past infection PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 10 B. Figure 37. Immune response to dengue infection [Lacuna, 2023] ANTIBODY-DEPENDENT ENHANCEMENT PHENOMENON ● Virus-antibody complexes are formed few days after second dengue infection where there is already pre-existing antibody from previous infection ● The non-neutralizing enhancing antibodies promote infection of higher numbers of mononuclear cells, followed by the release of cytokines, vasoactive mediators and procoagulants leading to disseminated intravascular coagulation (DIC) seen in severe hemorrhagic syndrome ○ It is not usually the virus that causes the hemorrhagic syndrome or bleeding ● Usually the reason behind severe dengue on a secondary infection ○ This phenomenon explains why primary infections typically cause milder illnesses than secondary infections[From Batch 2024 Trans] REVIEW QUESTIONS 1. Both man and animal may serve as a reservoir host in the animal-arthropod-man arbovirus transmission cycle. It may be observed in diseases such as Japanese Encephalitis (JE), Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), and Jungle Yellow Fever. A. The first statement is correct and the second statement is incorrect. B. The first statement is incorrect and the second is correct. C. Both statements are correct. D. Both statements are incorrect. 2. Which of the four severity grades of Dengue Hemorrhagic Fever (DHF) are associated with Dengue Shock Syndrome (DSS)? A. Grade I and Grade II B. Grade III and Grade IV C. Grade I and Grade IV D. Grade II and Grade III 3. Aedes aegypti are night feeders. They prefer to bite outdoors. A. The first statement is correct and the second statement is incorrect. B. The first statement is incorrect and the second is correct. C. Both statements are correct. D. Both statements are incorrect. 4. For most arbovirus, this arthropod vector typically causes Sicilian fever and Rift valley fever A. Mosquitoes B. Ticks C. Sandflies D. Lice 5. Chills, fever, headache, generalized myalgias, and GI complaints are the clinical features of Yellow Fever Virus. There is no vaccine available for Japanese encephalitis. A. The first statement is correct and the second statement is incorrect. The first statement is incorrect and the second is correct. C. Both statements are correct. D. Both statements are incorrect. 6. Chikungunya does not require antiviral therapy since it is self-limiting and has rare cases of mortality. Rift valley fever virus has clinical complications of myelomeningencephalitis, Guillan-barre syndrome, hepatitis, myocarditis, and pericarditis. A. The first statement is correct and the second statement is incorrect. B. The first statement is incorrect and the second is correct. C. Both statements are correct. D. Both statements are incorrect. 7. In the recovery phase of Dengue infection, gradual reabsorption of extravascular compartment fluid takes place in the next 48-72 hours if the patient survives the critical phase. At this stage, pleural effusion, capillary permeability, and plasma leakage from the critical phase are controlled by excessive IV fluid therapy. A. The first statement is correct and the second statement is incorrect. B. The first statement is incorrect and the second is correct. C. Both statements are correct. D. Both statements are incorrect. 8. The Dengue primary infection immune response is characterized by IgM antibodies produced approximately 5 days after symptoms appear. The secondary infection immune response is characterized by IgG antibodies rising rapidly 1-2 days after onset of symptoms. A. The first statement is correct and the second statement is incorrect. B. The first statement is incorrect and the second is correct. C. Both statements are correct. D. Both statements are incorrect. 9. This disease is transmitted by the vector, Culex mosquitoes, and is maintained in nature by the transmission cycle involving mosquitoes, birds, and pigs A. Dengue B. Yellow Fever Virus C. Chikungunya D. Japanese Encephalitis 10. Type of virus that is spherical, enveloped with 3 or 4 major structural polypeptides, and has a icosahedral nucleocapsid and (+) sense ssRNA A. Togaviridae B. Bunyaviridae C. Reoviridae D. Flaviviridae Answer Key 1. B (Only the animal is the reservoir host while man becomes the infected accidental) 2. B 3. D (They are DAYTIME feeders and prefer to bite INDOORS) 4. C 5. D (Rift valley fever virus; There is a vaccine available for Japanese Encephalitis) 6. A (2nd statement - Chikungunya) 7. A (No need for excessive IV fluid therapy because there is fluid reabsorption in recovery phase) 8. C 9. D 10. A PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 11 APPENDIX Table 1. Summary Table of Family of Arboviruses (Lacuna, 2023) SUMMARY TABLE Family Genus/Species Togaviridae Alpha virus 1. Western equine encephalitis (WEE) 2. Eastern equine encephalitis (EEE) 3. Venezuelan equine encephalitis (VEE) 4. Chikungunya virus ● ● ● ● ● ● ssRNA (+) Non-segmented Icosahedral symmetry Replicates in the cytoplasm Enveloped Mosquito vector Flaviviridae 1. Yellow fever virus 2. Dengue virus 3. St. Louis encephalitis 4. Japanese encephalitis 5. Hepatitis C virus 6. West Nile Virus 7. Zika virus ● ● ● ● ● ● ssRNA (+) 1. Yellow fever Non-segmented RNA ○ Hepatitis (with jaundice) Icosahedral symmetry ○ Fever Replicates in the cytoplasm ○ Backache Enveloped 2. Dengue fever (“break bone Mosquito vector fever”) ○ Aedes: yellow fever and ○ Painful fever dengue fever ■ High fever ○ Culex: St. Louis ■ Headache Japanese, and West Nile ■ Muscle aches encephalitis ■ Joint pains ■ Backache ○ Dengue hemorrhagic fever ■ Hemorrhage ■ Thrombocytopenia ■ Septic shock 3. St. Louis, japanese, West Nile encephalitis ○ Encephalitis and fever 4. Hepatitis C virus 5. West Nile ○ Fever ○ Meningitis ○ Encephalitis or myelitis that produces flaccid paralysis 6. Zika ○ Mild fever ○ Skin rash ○ Conjunctivitis ○ Muscle and joint pain ○ Malaise ○ Headache ○ Microcephalic babies ■ If pregnant woman is infected 1. California encephalitis virus 2. Rift valley fever virus 3. Sandfly fever virus ● ● ● ● ssRNA (-) Segmented (3 segments) Helical symmetry Arthropod vector (except for Hantavirus) Orbiviruses ● dsRNA 9(-) ● 12 segments. ● Viruses are doughnut-shaped and are approx. 80 nm in diameter. ● Do not possess an envelope ● Tick vector ● Transmitted from small rodents by ticks. ● Seen in the north-western USA and Canada) and in the CIS and eastern Europe Bunyaviridae Reoviridae Morphology Clinical Findings 1. WEE, EEE, and VEE: ○ Headache ○ Fever ○ Altered level of consciousness ○ Focal neurologic deficits 2. Chikungunya ○ Initially: fever, rash, joint pain ○ Chronic arthritis ● Most cause fever and encephalitis ● Rift valley fever can also cause hemorrhagic manifestations ● Colorado Tick Fever (Coltivirus) ○ Febrile illnesses ○ Often with meningitis or meningo-encaphalitis, PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 12 Figure 38. Comparison of Anopheles, Aedes, and Culex mosquitoes [Lacuna, 2023]. PH152:MICROBIO | GROUP D: Beltran, Bernal, Bustos, Cruz 13