vector-borne diseases of public health importance diseases of public health importance 14 recent...

Biology and Control of Insects and Rodents Workshop – Jan 26-28, 2010Arthropod-borne Diseases of Public Health Importance 1

Dawn H. GougeDawn H. Gouge

University of ArizonaUniversity of Arizona

Vector-Borne Diseases of Public Health Importance

•• A A biological associationbiological association between an arthropod between an arthropod (insect or arachnid)(insect or arachnid) and a pathogen acquired by and a pathogen acquired by feeding on the blood of an infected vertebrate feeding on the blood of an infected vertebrate host or through host or through transovarialtransovarial (TOT)(TOT) or venereal or venereal transmission transmission

•• ArbovirusesArboviruses ((ARthropodARthropod--BOrneBOrneViruses) Viruses)

Definition of Vector-Borne:

?

•• MosquitoMosquito transmitted pathogenstransmitted pathogens

•• VirusesViruses

•• MalariaMalaria

•• FleaFlea transmitted pathogenstransmitted pathogens

•• PlaguePlague

•• TickTick transmitted pathogenstransmitted pathogens

•• Lyme DiseaseLyme Disease

•• Rocky Mountain Spotted FeverRocky Mountain Spotted Fever

•• TularemiaTularemia

•• OtherOther rare pathogens present in the USrare pathogens present in the US


•• West Nile virus West Nile virus (WNV)(WNV)

•• St. Louis encephalitis virus St. Louis encephalitis virus (SLE)(SLE)

•• California group viruses California group viruses (CE & LACV)(CE & LACV)

•• Western equine encephalitis virus Western equine encephalitis virus (WEE)(WEE)

•• Eastern equine encephalitis virus Eastern equine encephalitis virus (EEE)(EEE)

•• Dengue virus Dengue virus (DEN)(DEN)

•• MalariaMalaria

Mosquito Transmitted Pathogens

Arboviruses•• Seasonal Seasonal –– typically occur in warm monthstypically occur in warm months

•• Incidence varies with time and place because Incidence varies with time and place because ecological factors are importantecological factors are important

•• For each of these viruses, the ratio of clinical to For each of these viruses, the ratio of clinical to subclinicalsubclinical infection varies infection varies (number of detected (number of detected cases versus number actually infected)cases versus number actually infected)

•• With the exception of dengue virus, and yellow With the exception of dengue virus, and yellow fever, humans are deadfever, humans are dead--end hosts.end hosts.


West Nile Virus (WNV)•• Most recent mosquito transmitted Most recent mosquito transmitted arbovirusarbovirus in the USin the US

•• Discovered in New York City Discovered in New York City in 1999 and has spread to in 1999 and has spread to every state in the continental every state in the continental US and most other countries US and most other countries south of Canadasouth of Canada

•• Basic cycle: bird to mosquito Basic cycle: bird to mosquito

•• Bird deaths associated with Bird deaths associated with infectioninfection

West Nile Virus•• Most human infection occurs by mosquito Most human infection occurs by mosquito

bite, Maybite, May–– Oct. Oct. (longer season further south)(longer season further south)

•• Blood transfusion, infected tissue donation, Blood transfusion, infected tissue donation, placental, and accidental laboratory placental, and accidental laboratory infectionsinfections

•• 80% of all human infections show no 80% of all human infections show no symptoms symptoms –– of the symptomatic of the symptomatic 20%, most go on to develop 20%, most go on to develop West Nile feverWest Nile fever

West Nile Virus•• After bite of infected mosquito, it takes 2After bite of infected mosquito, it takes 2--14 days for 14 days for

symptoms to occursymptoms to occur

•• Characteristics of WN Fever Characteristics of WN Fever -- fever, headache, fatigue, fever, headache, fatigue, sometimes rash, swollen lymph glands and/or eye painsometimes rash, swollen lymph glands and/or eye pain

•• Severe disease occurs in up to 1% of infected Severe disease occurs in up to 1% of infected individuals individuals -- meningitis and/or encephalitis and/or meningitis and/or encephalitis and/or (sometimes)(sometimes) paralysisparalysis

•• Approximately 10% of Approximately 10% of severesevere cases are fatalcases are fatal


West Nile Virus: Background• First isolated in 1937 in Uganda from blood

of a febrile woman• Family: Flaviviridae• All are

transmissible by mosquitoes, many can cause febrile, sometimes fatal, illnesses in humans.

WNV Outbreak in NE U.S. 1999• 62 confirmed human clinical cases• 7 deaths due to West Nile Virus• first occurrence of disease in

Western Hemisphere• majority of clinical cases and deaths were

among elderly • 70% of human cases

occurred within a10km radius of Queens

North Queens Serosurvey Area

West Nile Virus in the US -Some Possible Pathways of Introduction

• Human-transported vertebrate host (mammal or bird)• Legal• Illegal

• Human-transported vector (s)• Storm-transported vertebrate host (bird)• Migration of infected bird less likely (virus

almost identical to Middle Eastern strain)• Infected human host from endemic area overseas


West Nile Virus U.S. 1999-2001West Nile Virus U.S. 1999West Nile Virus U.S. 1999--20012001

West Nile Virus U.S. 1999-2002West Nile Virus U.S. 1999West Nile Virus U.S. 1999--20022002

January 2004January 20042004


2007

2007 WNV in the United States


663 cases (incl. severe and mild) 30 deaths



Primary WNV Vectors•• Northeastern and Northeastern and northcentralnorthcentral US US –– CulexCulex p. p.

pipienspipiens

•• Southeastern US Southeastern US –– CulexCulex p. p. quinquefasciatusquinquefasciatus and and CxCx. . nigripalpusnigripalpus

•• SouthcentralSouthcentral US US -- CulexCulex p. p. quinquefasciatusquinquefasciatusand and CxCx. . salinariussalinarius

•• Mountain west and western US Mountain west and western US –– CulexCulextarsalistarsalis and and CxCx. p. . p. quinquefasciatusquinquefasciatus

West Nile Virus Severe Disease Risk Factors

•• Exposure to infected mosquitoes when > 50 years of Exposure to infected mosquitoes when > 50 years of age age (most fatalities > 75 years)(most fatalities > 75 years)

•• CulexCulex sppspp. mosquitoes . mosquitoes -- but over 60 mosquito but over 60 mosquito sppspp. . have been found naturally infectedhave been found naturally infected

•• Recreational and/or occupational exposure in urban Recreational and/or occupational exposure in urban or rural settingor rural setting

•• Primary and secondary vectors can vary locally and Primary and secondary vectors can vary locally and regionally, so understanding local transmission is regionally, so understanding local transmission is crucialcrucial

St. Louis Encephalitis Virus•• Distribution similar to WNV in New World onlyDistribution similar to WNV in New World only

•• Bird Bird –– mosquito cycle; similar primary mosquito mosquito cycle; similar primary mosquito vectors (vectors (CulexCulex sppspp..) and transmission season to ) and transmission season to WNVWNV

•• Most similar to WNV in Most similar to WNV in urbanurban situations situations –– sparrows sparrows and other and other peridomesticperidomestic birds important for birds important for amplifying virus amplifying virus


During extended spring droughts vector During extended spring droughts vector mosquitoes and nestling, juvenile, and adult mosquitoes and nestling, juvenile, and adult wild birds congregate in selected refuges, wild birds congregate in selected refuges, facilitating epizootic amplification of SLEV.facilitating epizootic amplification of SLEV.

19751975

Less than 1% of St. Louis encephalitis viral infections are clinically apparent

SLE Symptoms and Risks•• 0 0 –– 2,000 cases/year 2,000 cases/year (1975),(1975), but usually smaller but usually smaller

outbreaks; average of ~ 130 cases/yroutbreaks; average of ~ 130 cases/yr

•• Most infections asymptomatic or mild, with Most infections asymptomatic or mild, with casecase--fatality ratio of 5 to 15%fatality ratio of 5 to 15%

•• Severe disease Severe disease –– meningitis, encephalitis, coma, meningitis, encephalitis, coma, deathdeath

•• Similar risk to WNV Similar risk to WNV –– increasing age, outdoor increasing age, outdoor exposure in urban or exposure in urban or periurbanperiurban areasareas


California Group ( La Crosse )Encephalitis

•• Distribution in Eastern US and Canada Distribution in Eastern US and Canada –– highly focal highly focal association with mosquito distributionsassociation with mosquito distributions

•• AedesAedes triseriatustriseriatus mosquito and chipmunk/ squirrel mosquito and chipmunk/ squirrel transmission cycle transmission cycle –– also TOTalso TOT

•• Vectors are woodland/suburban container inhabiting Vectors are woodland/suburban container inhabiting speciesspecies

•• Likely secondary or locally important vectors are Likely secondary or locally important vectors are AeAe. . albopictusalbopictus and and AeAe. . japonicusjaponicus

80-100 La Crosse encephalitis virus (LACV) neuroinvasivedisease cases are reported each year

California Serogroup Virus Neuroinvasive Disease CasesReported by State, 1964-2008

LACV Symptoms and Risk•• Approximately 70 cases/yearApproximately 70 cases/year

•• Most infections asymptomatic or mild, with Most infections asymptomatic or mild, with <1% case fatality ratio<1% case fatality ratio

•• Severe disease Severe disease –– encephalitis, seizure, encephalitis, seizure, coma, coma, sequelaesequelae are commonare common

•• Children <16 years Children <16 years -- most severe diseasemost severe disease

•• Woodland areas with containers Woodland areas with containers (natural or (natural or manmade);manmade); rural poorrural poor


Western Equine Encephalitis Virus

•• Distribution in Western US, Canada, Central and South Distribution in Western US, Canada, Central and South AmericaAmerica

•• CulexCulex tarsalistarsalis –– bird transmission cyclebird transmission cycle

•• Vector tends to be associated with Vector tends to be associated with irrigation or other farming practicesirrigation or other farming practices

•• Rural or Rural or periurbanperiurban transmission most transmission most commoncommon

•• Also infects horses Also infects horses –– 50% mortality 50% mortality in unvaccinated animalsin unvaccinated animals

WEE Symptoms and Risk•• 640 confirmed cases since 1964, but less than 640 confirmed cases since 1964, but less than

00--2/year in past 10 years2/year in past 10 years

•• ~ 13% of infections show disease ~ 13% of infections show disease (30% of (30% of infants)infants) with 3% case fatality ratiowith 3% case fatality ratio

•• Severe disease Severe disease -- encephalitis, coma, death; encephalitis, coma, death; seizures common in infantsseizures common in infants

•• Rural areas where the vector is commonRural areas where the vector is common


Eastern Equine Encephalitis VirusEastern Equine Encephalitis Virus•• Distribution in the Eastern US, Canada to Central and Distribution in the Eastern US, Canada to Central and

South AmericaSouth America

•• Bird Bird –– mosquito cycle maintained by bird feeding mosquito cycle maintained by bird feeding mosquito, mosquito, CulisetaCuliseta melanuramelanura in swamp/wetland areasin swamp/wetland areas

•• Transmission to humans and horses by Transmission to humans and horses by ““bridgebridge”” vectors, vectors, AedesAedes, , CulexCulex and and CoquillettidiaCoquillettidia sppspp..

•• High equine mortality if unvaccinatedHigh equine mortality if unvaccinated

EEE Symptoms and Risk•• 257 cases confirmed since 1964, with ~ 5 257 cases confirmed since 1964, with ~ 5

cases/yrcases/yr

•• Rare infection, but 30% mortality rateRare infection, but 30% mortality rate

•• Severe disease Severe disease (encephalitis, coma, death)(encephalitis, coma, death) most most common in <15 or >50 yearscommon in <15 or >50 years

•• 50% of severe disease survivors have 50% of severe disease survivors have permanent neurological damagepermanent neurological damage

•• Risk assoc. with age and residence near Risk assoc. with age and residence near endemic areasendemic areas


Dengue Virus•• Distribution worldwide Distribution worldwide (50(50--100 million cases 100 million cases

with ~200,000 severe)with ~200,000 severe) –– not common in US, not common in US, but recent S. Texas casesbut recent S. Texas cases

•• Human Human –– mosquito transmission, mosquito transmission, AedesAedesaegyptiaegypti vectorvector

•• Vector develops in containers Vector develops in containers and feeds during the daytime and feeds during the daytime

•• Typically urban transmission in Typically urban transmission in overpopulated tropical/subtropical areasoverpopulated tropical/subtropical areas

Dengue Virus•• More than oneMore than one--third of the worldthird of the world’’s population s population

live in areas at risk for transmission live in areas at risk for transmission

•• Dengue infection is a leading Dengue infection is a leading cause of illness and death in the cause of illness and death in the tropics and subtropics. tropics and subtropics.

•• As many as 100 million people As many as 100 million people are infected yearly.are infected yearly.

DEN Symptoms and Risk•• There are 4 serotypes There are 4 serotypes (DEN 1(DEN 1--4)4) and all can and all can

cause classical dengue cause classical dengue (sudden fever, headache, (sudden fever, headache, severe aches and rash)severe aches and rash) known as known as ““breakbonebreakbonefeverfever””

•• Following sequential infection with different Following sequential infection with different serotypes, severe hemorrhagic manifestations serotypes, severe hemorrhagic manifestations known as dengue hemorrhagic fever known as dengue hemorrhagic fever (DHF)(DHF) can can resultresult

•• DHF risk highest for <15 years of ageDHF risk highest for <15 years of age


•• 1950 Pan American Health Organization 1950 Pan American Health Organization begins eradication campaign to prevent urban begins eradication campaign to prevent urban yellow fever.yellow fever.

•• Dengue declines. Dengue declines.

•• Eradication program discontinued in the US in Eradication program discontinued in the US in 1970.1970.

•• Geographic distribution Geographic distribution of of AeAe. . aegyptiaegypti in 2009 in 2009 is much wider than is much wider than before eradication.before eradication.

2008

•No dengue vaccine is available. •An effective dengue vaccine for public use will not be available for 5 to 10 years.


Recent Dengue in the US•• Texas Texas –– endemic transmission 6 times between endemic transmission 6 times between

1980 and 20041980 and 2004

•• First local DHF case in south Texas in 2005 First local DHF case in south Texas in 2005 and studies show undetected local DENand studies show undetected local DEN

•• Hawaii Hawaii –– 88 cases in 200188 cases in 2001--02 (02 (AedesAedesalbopictusalbopictus vector)vector)

•• Low but increasing risk for local transmission, Low but increasing risk for local transmission, since 1977, ~ since 1977, ~ 4000 cases imported to US4000 cases imported to US (100(100--200 cases/year)200 cases/year)

Dengue Risk•• Areas in the southern and southeastern US Areas in the southern and southeastern US

where both one or both vectors are present where both one or both vectors are present (especially(especially AedesAedes aegyptiaegypti) are at risk for ) are at risk for sporadic outbreakssporadic outbreaks

•• Increased influx of residents from dengue Increased influx of residents from dengue endemic regions outside the US endemic regions outside the US (as currently (as currently occurs in New Orleans following Hurricane occurs in New Orleans following Hurricane Katrina)Katrina) further adds to the risk of introduction further adds to the risk of introduction and local transmissionand local transmission

Yellow Fever• The last epidemic of yellow fever in North

America occurred in New Orleans in 1905.


Malaria in the US•• 1,337 cases of malaria with 8 deaths, were 1,337 cases of malaria with 8 deaths, were

reported in the US in 2002reported in the US in 2002

•• 5 of those cases were locally acquired5 of those cases were locally acquired

•• Between 1957 and 2003, 63 outbreaks of Between 1957 and 2003, 63 outbreaks of locally transmitted malaria have occurredlocally transmitted malaria have occurred

•• Two species of Two species of AnophelesAnopheles mosquitoes have mosquitoes have been implicatedbeen implicated

•• About 1200 cases of malaria are diagnosed in About 1200 cases of malaria are diagnosed in the United States each yearthe United States each year


Malaria in the US•• "Airport malaria" is a term coined by "Airport malaria" is a term coined by

researchers to explain the more recent spread researchers to explain the more recent spread of malaria to areas such as the United States of malaria to areas such as the United States and Europe, which some scientists credit to and Europe, which some scientists credit to warmer climate changeswarmer climate changes

All but one of these cases were acquired outside of the United States; one was acquired through a blood transfusion.

Malaria Symptoms and Risk•• Classic symptoms: fever, chills, sweating, Classic symptoms: fever, chills, sweating,

headaches, muscle pains headaches, muscle pains

•• Severe symptoms: cerebral malaria, Severe symptoms: cerebral malaria, anemia, kidney failure anemia, kidney failure

•• Plasmodium Plasmodium falciparumfalciparum causes most severe causes most severe disease and deathdisease and death

•• Night time biting mosquitoes in rural areas Night time biting mosquitoes in rural areas of southeastern US and southern Californiaof southeastern US and southern California

Tick Transmitted Pathogens

•• Lyme DiseaseLyme Disease

•• Rocky Mountain Rocky Mountain Spotted FeverSpotted Fever

•• TularemiaTularemia

Lyme disease, Babesiosis, Ehrlichiosis.

Western Black-Legged Tick (IxodesPacificus)


Takes 24-48 hours for a tick to transmit bacteria -Rapid removal is important

•Using a pair of pointed (fine-tipped) tweezers, grasp the mouthparts of the tick as close to the skin as possible. •Pull the tick straight out with a firm and steady force. •Wash the area of the bite with soap and water. •Place the tick in a jar of alcohol for ID and testing.•Contact your physician. •Watch the bite for signs of a rash.

Lyme Disease – Borrelia Spp.


Lyme Disease Symptoms and Risks

•• First sign is usually a circular rash.First sign is usually a circular rash. A distinctive feature A distinctive feature of the rash is that it gradually expands over a period of of the rash is that it gradually expands over a period of several days several days

•• Loss of muscle tone on one orLoss of muscle tone on one orboth sides of the face, severe both sides of the face, severe headaches and neck stiffness, headaches and neck stiffness, shooting pains that may shooting pains that may interfere with sleep, heart interfere with sleep, heart palpitations and dizziness, palpitations and dizziness, and pain that moves from and pain that moves from joint to joint. joint to joint.

Rocky Mountain Spotted Fever

(RMSF) - Rickettsia rickettsii•• Rocky Mountain spotted fever was first recognized Rocky Mountain spotted fever was first recognized

in 1896 in the Snake River Valley of Idaho and was in 1896 in the Snake River Valley of Idaho and was originally called "black measles" because of the originally called "black measles" because of the characteristic rash. characteristic rash.

•• Most severe and frequently Most severe and frequently reported reported rickettsialrickettsial illness illness in the US, Mexico, in the US, Mexico, Central and South America. Central and South America.


Initial symptoms include fever, nausea, Initial symptoms include fever, nausea, vomiting, severe headache, muscle pain, lack vomiting, severe headache, muscle pain, lack of appetite.of appetite.

•• The rash first appears 2The rash first appears 2--5 days 5 days after the onset of fever and may be after the onset of fever and may be very subtle. very subtle.

•• Often it begins as small, flat, pink, Often it begins as small, flat, pink, nonnon--itchy spots itchy spots ((maculesmacules)) on the on the wrists, forearms, and ankles.wrists, forearms, and ankles.

•• Later signs and symptoms Later signs and symptoms include rash, abdominal pain, include rash, abdominal pain, joint pain, diarrhea. joint pain, diarrhea.

Rocky Mountain wood tick (Dermacentor andersoni)

Cayenne tick (Amblyomma cajennense)

American dog tick (Dermacentor variabilis)

Brown dog tick (Rhipicephalussanguineus)


Tularemia - Francisella tularensis.•• Tularemia, also known as Tularemia, also known as ““rabbit fever,rabbit fever,”” bacterial bacterial

disease.disease.

•• Typically found in animals, especially rodents, rabbits, Typically found in animals, especially rodents, rabbits, and hares. Usually a rural disease and has been and hares. Usually a rural disease and has been reported in all U.S. states except Hawaii.reported in all U.S. states except Hawaii.

•• People become infected through the bite of infected People become infected through the bite of infected arthropods arthropods (most commonly, ticks and deerflies),(most commonly, ticks and deerflies), by by handling infected sick or dead animals, by eating or handling infected sick or dead animals, by eating or drinking contaminated food or water, or by inhaling drinking contaminated food or water, or by inhaling airborne bacteria. airborne bacteria.

Tularemia Symptoms and Risks•• The signs and symptoms depend on how you are The signs and symptoms depend on how you are

exposed to tularemia: exposed to tularemia:

•• skin ulcers, skin ulcers, swollen and painful swollen and painful lymph glands, lymph glands, inflamed eyes, inflamed eyes, sore throat, sore throat, mouth sores, mouth sores, diarrhea diarrhea pneumonia. pneumonia.

•• If inhaled: abrupt onset of fever, chills, headache, If inhaled: abrupt onset of fever, chills, headache, muscle aches, joint pain, dry cough, and weakness. muscle aches, joint pain, dry cough, and weakness.


Tularemia can be fatal if the person is Tularemia can be fatal if the person is not treated with appropriate antibiotics. not treated with appropriate antibiotics.

Lone star tick(Amblyommaamericanum)

American dog tick(Dermacentor variabilis)

ChrysopsSpp.

3000-4000 eggs

Rare Vector-Borne Infections with Recent US Human Cases

•• ChagasChagas Disease Disease ((triatominetriatomine bugs)bugs)

•• LeishmaniasisLeishmaniasis (sand flies)(sand flies)

•• MurineMurine Typhus Typhus (fleas)(fleas)

Chagas Disease vector in Louisiana, Triatoma sanguisuga

Cases of cutaneousleishmaniasis have been reported in Texas and Oklahoma.


Chikungunya fever

• Chikungunya fever is a disease caused by an Alpha virus spread to people through the bite of infected mosquitoes; primarily primate reservoir species.• Symptoms can include sudden fever, joint pain with or without swelling, chills, headache, nausea, vomiting, lower back pain, and a rash. • Chikungunya mainly occurs in areas of Africa and Asia.• In 2007, limited transmission of chikungunya virus occurred in Italy.•Aedes aegypti, and Aedes albopictus•Biological weapon

Links for Additional Information:

http://www.cdc.gov/ncidod/dvbid(CDC’s NCID/DVBID Home Page)

http://www.cdc.gov/malaria(CDC’s Malaria Home Page)

Also search CDC A-Z listing for Chagas, Leishmaniasis, etc.

AcknowledgementsAcknowledgementsDawn M. Wesson Dawn M. Wesson

&&Mike Lester R.S., M.P.A.

Last 20 years there has been a dramatic global resurgence & emergence of epidemic arboviral diseases affecting humans and domestic animals.

Viruses thought to be under control (dengue, Japanese encephalitis, yellow fever, and Venezuelan equine encephalitis).

Viruses that have expanded their geographic distribution such as West Nile and Rift Valley fever.


Bedbugs may be a vector for hepatitis B1 and in endemic areas for American trypanosomiasis - Chagas disease2. Of note, reports have indicated the risk of insect transmission of HIV, if any, is extremely low and likely nonexistent 3,4.

1 Ogston CW, Wittenstein FS, London WT, Millman I. J Infect Dis. Sep 1979;140(3):411-4.2 Pipkin AC Sr. Int Rev Trop Med. 1969;3:1-47.3 Iqbal MM. J La State Med Soc. Aug 1999;151(8):429-33.4 Webb PA, Happ CM, Maupin GO, Johnson BJ, Ou CY, Monath TP. . J Infect Dis. Dec 1989;160(6):970-7.

vector-borne diseases of public health importance diseases of public health importance 14 recent...

Documents