11/9/2017. New and Re-emerging Vector-Borne Diseases and the efforts to stop them through Mosquito Control

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1 New and Re-emerging Vector-Borne Diseases and the efforts to stop them through Mosquito Control José Luis Ramirez Research Entomologist ARS USDA What are Vector-Borne Diseases? Diseases caused by pathogens that are carried and transmitted by a vector (i.e. mosquitoes, ticks). Arthropod vectors: - Transmit a pathogen from a person (or animal) to another person. - Insects: Mosquitoes, fleas, sandflies, kissing bugs - Arachnids : Ticks. Images source: CDC Vector-Borne Diseases Vector-borne diseases account for 17% of all infectious diseases. More than 1 billion cases and more than 1 million deaths / year. Dengue fever: - Globally, more than 2.5 billion people in 100 countries at risk of dengue infection. Malaria : - Causes more than 600,000 deaths annually. - Most of them children under 5 years of age. Photo by Guardian Media Source: WHO

2 Deaths From Vector-Borne Diseases Vector-Borne Diseases Affecting Public Health Around the World Malaria Dengue fever Chikungunya Zika Relapsing fever Japanese encephalitis Yellow fever Rift Valley fever Plague Rickettsiosis Onchocerciasis Relapsing fever Leishmaniasis Chagas disease Lyme disease West Nile fever Sandfly fever Sleeping sickness Rocky Mountain spotted fever Tularaemia Tick-borne encephalitis Lymphatic filariais Crimean-Congo haemorrhagic fever Examples of Vector-Borne Diseases Systems Disease Lyme disease Malaria Filariasis Zika fever PATHOGEN BACTERIA Rickettsia spp. Borrelia spp. Ehrlichia spp. PROTOZOA Babesia spp. Plasmodium spp. Leishmania spp. HELMINTHS Brugia spp. Onchocerca spp. Wuchereria spp. VIRUS Dengue virus Zika Virus Powasan Virus VECTOR Ticks Fleas Mosquitoes Sandflies Kissing bug Mosquitoes Blackflies Tabanid flies Mosquitoes Ticks Images: James Gathany, CDC 2

3 Arboviral Diseases Arbovirus: Arthropod Borne Virus A virus that: - can infect an arthropod, during blood meal, - can multiply in the arthropod body, and - can be transmitted by bite while feeding on the next susceptible vertebrate. About 100 arboviruses infect humans. Important Arboviral Families: Arboviral Diseases Arboviral Vectors Ticks Mosquitoes 3

4 Mosquito Life Cycle Arbovirus Life Cycle (Dengue virus, Zika virus) Extrinsic incubation period Intrinsic incubation period Source: Nature / Citable Virus replication cycle in Ae. aegypti (7-14 days) 4

5 Virus replication cycle in Ae. aegypti (7-14 days) Day 7-14 PBM Virus replication cycle in Ae. aegypti (7-14 days) Day 7-14 PBM Arboviral diseases (potential clinical cases in IL) La Crosse Encephalitis Virus (LACV) West Nile Virus (WNV) Dengue Virus (DENV) Zika Virus (ZIKV) 9

6 La Crosse Encephalitis Virus La Crosse Encephalitis Virus (LACV) Discovered in Isolated from a frozen brain and spinal tissue of a child who died in La Crosse, Wisconsin (1960). Reservoirs: Eastern chipmunk and eastern grey squirrel. Cases occur late spring early fall. CDC La Crosse Encephalitis Virus (LACV) La Crosse Vectors: Aedes triseriatus (tree hole mosquito) Transovarial transmission in mosquitoes. Images: James Gathany, CDC 10

7 La Crosse Encephalitis Virus (LACV) La Crosse virus neuroinvasive disease cases reported by year, La Crosse virus neuroinvasive disease average annual incidence by county,

8 La Crosse virus disease cases for 2016 La Crosse Encephalitis Virus (LACV) Children mostly infected - 75% of cases under 10 yr. of age Symptoms: - Most infections are asymptomatic. - Fever, headache, nausea, vomiting and tiredness. - Severe disease on children under 16 yrs. - Mild febrile to aseptic meningitis - Seizures. - Encephalitis. No vaccine available. West Nile Virus 12

9 West Nile Virus (WNV) Flavivirus. Originated from West Nile Region (UGANDA) 1937 Introduced to the USA in in 4 years spread across the continental USA and Canada. Reservoirs: Birds, (small mammals?, reptiles?). Cases occur during the Summer early Fall. West Nile Virus (WNV) Vectors - More than 40 species of mosquitoes implicated in transmission. - Culex spp. (main vector) Image: James Gathany, CDC West Nile Virus (WNV) Transmission Cycle 13

10 West Nile Virus (WNV) West Nile Virus (WNV) Symptoms: -Most infections are asymptomatic 70 to 80% do not develop symptoms - Flu-like symptoms, rash, encephalitis. - Severe cases (1%) Most severe cases with elderly and immunosuppressed. No vaccine available. Dengue Virus 14

11 DENGUE VIRUS (DENV) Dengue Virus: - One of the most important vector-borne viral disease. - ~400 million people infected yearly. - Break-bone fever - 4 serotypes: DENV1, DENV2, DENV3, DENV4 CDC - No vaccine available (some on the pipeline) DENGUE VIRUS (DENV) VECTORS Aedes aegypti Aedes albopictus 15

12 Natural tree holes: mosquito breeding habitats (Peoria, IL) Dengue Fever Cases Source: Dengue incidence on the rise in the Americas Source: Pan American Health Organization 16

13 Dengue Outbreaks in the Americas Dengue Outbreaks in the Americas Dengue Outbreaks in the Americas 17

14 Dengue Outbreaks in the Americas LOCALLY-Acquired Dengue cases in the USA IMPORTED Dengue cases in the USA 18

15 Dengue Fever Symptoms Dengue Fever: - high fever, headache, rash. - Severe pain behind the eyes. - Joint, muscle and/or bone pain. Dengue Hemorrhagic Fever: - Fever last 2-7 days, fever declines but then: - Increased vascular permeability (internal bleeding) - Low platelet count - Vomiting blood, bleeding from nose or gums. Dengue Shock Syndrome: - Circulatory failure - Bleeding (petechial) - Weak rapid pulse, cold clammy skin denguevirusnet Zika Virus ZIKA VIRUS - Ongoing outbreak in the Americas. - Flavivirus. - Discovered in 1947 (Zika Forest, Uganda) - May 2015: 1 st confirmed Zika virus infection in Brazil. - February 1, 2016: WHO declared Zika virus Public Health Emergency of International Concern (PHEIC) - Continues to spread to new areas. 19

16 How is Zika virus transmitted? * Primarily by mosquitoes * From a pregnant woman to her fetus. * Sexual contact. * Blood transfusion. Photo Vectors of DENGUE and ZIKA VIRUS Aedes aegypti Aedes albopictus ZIKA VIRUS Distribution of vectors in the USA (as of October, 2017) Source: 20

17 Zika Virus Infection Symptoms Symptoms: - Mostly asymptomatic: 1 in 5 infected show symptoms. - Mild symptoms: - Fever - Rash - Joint pain - Conjunctivitis - Muscle pain - Headache Zika Pathology - Zika effects on pregnancy: - Zika virus can pass from mother to her fetus during pregnancy or at delivery. - Zika virus infection causes microcephaly. - Baby s head is smaller than normal. - Zika virus infection will not affect future pregnancies. - No reports of transmission through breastfeeding. Source: AP Zika Pathology - Zika infection in adults: -Guillain-Barré Syndrome: A person s own immune system damages the nerve cells. This causes muscle weakness and paralysis Usually triggered following a variety of infections. - It is likely triggered in a small proportion of Zika infections. - Still under investigation. 21

18 Risk of Zika (2016) Zika in the United States Local transmission of Zika virus confirmed in: Miami-Dade County, Florida, and Brownsville, Texas. Miami-Dade County, Florida CDC lifted the yellow area designation for Miami-Dade County on June 2, Brownsville, Texas CDC lifted the yellow area designation for Brownsville, Texas on August 29, USA, Zika cases: January November 1, 2017 US States Travel-associated cases reported: 327 Locally acquired vector-borne cases reported: 1 Sexually transmitted: 3 Total: 331 US Territories Travel-associated cases reported: 0 Locally acquired cases reported: 583 Cases acquired through other routes: 0 Total:

19 Laboratory-confirmed symptomatic Zika virus disease cases* reported to ArboNET by states United States, Pregnant women with lab evidence of Zika Virus infection ( ) (as of October 17, 2017) Source: Pregnancy outcomes- from USA Zika Virus infections ( ) (as of October 17, 2017) Source: 23

20 What to consider when suspecting an arboviral infection Epidemiology: - Travel history (geographical location) - Time of the year (seasons) Photo Source: GE What to consider when suspecting an arboviral infection Epidemiology: - Travel history (geographical location): * Recent trip to a Zika/dengue endemic region? * When did the travel occurred? * How long since the person returned? -If more than 2 weeks most likely not dengue or Zika. Source: GE Epidemiology: What to consider when suspecting an arboviral infection - Time of the year (seasons): Dengue outbreaks are seasonal Mosquito population increase during the rainy season. 24

21 What is done to control vector-borne diseases? No vaccine or drugs available yet for most diseases. Control measures relies mostly on: - Mosquito control by pesticide application. Global News file photo Photo by Marian Galbraith Mosquito Control Approaches Biocontrol: Mosquito-fish, BT capsules,etc. Wolbachia-mosquito: Resistant to arboviruses. Genetically modified mosquitoes: Oxitec s GM mosquitoes: self-limiting gene. USDA- ARS: Fungi and bacteria pathogenic to mosquitoes. Microbe and plant-derived compounds with mosquitocidal activity. Factors Complicating Control Measures Several factors complicate control measures: - Mosquitoes developing resistance - Socio-political-economic problems - Ecological and biological factors - Physical and environmental factors. 25

22 DENGUE and ZIKA VIRUS VECTORS Aedes aegypti Aedes albopictus 26

23 chensiyuan Mexico City, Mexico Photo by: Pablo Lopez Luz Port-au-Prince, Haiti. Photograph: Google Earth/2014 Digital Globe 27

24 Photo: Eoghan Rice / Trócaire Photo: Jonathan McIntosh Alabama,

25 Tampa, Florida RICHARD DANIELSON Times Peoria IL, October 2017 Peoria IL, August

26 SUMMARY Vector-borne pathogens: - Diverse pathogens and vectors -Most of them transmitted by mosquitoes - Many vector-borne diseases on the rise - Increase with globalization (trade and travel) Arboviral diseases: -Some are common to this area: - La Crosse virus.- Encephalitis in children. - West Nile virus. Neuropathology. - Some are imported cases: - Zika virus - Dengue virus. Acknowledgments Molly K. Schumacher MSc. Alejandro Rooney PhD. Agricultural Research Service REFERENCES Dengue Virus: Zika Virus: West Nile Virus: 30