Arthropod Disease 9_2007

7/29/2019 Arthropod Disease 9_2007

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Arthropod Disease

Surbhi Modi, MD, MPH

Preventive Medicine ResidentEmory University School of Medicine

September 20, 2007


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OBJECTIVES

1. Understand the role of arthropods inhuman disease

2. Recognize arthropods implicated inimportant human diseases

3. Describe important vector-borne

diseases


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WHAT AREARTHROPODS?

Largest phylum of

animals 80% of

described animalspecies arearthropods

Include insects,spiders,crustaceans


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MEDICAL ENTOMOLOGY

Directparasitism orinjury

Indirect injuryas diseasevectors


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DIRECT DISEASEAGENTS


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SCABIES

Caused by the mite Sarcoptes scabei

Mites burrow under the skin takes


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SCABIES


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SCABIES

Clinical diagnosis, but can confirm by microscopy

Treatment: Ivermectin

Lindane, Permethrin, Crotamiton

Prevent Re-infection Treat ALL family & close contacts

Clean environment

Warn patients that itching may continue for 2 4weeks after treatment initiated


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BROWN RECLUSE SPIDERBITES

Found in midwest & south-central US

Reclusive nature Found inside shoes,

clothing, attics, cardboard

boxes, etc. Be careful of misdiagnosis!


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BROWN RECLUSE SPIDERBITES

Painless bite

Followed byerythema,

swelling,tenderness


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BROWN RECLUSE SPIDER BITE

Skin necrosis

Sphingomyelinase D

Rare systemicreactions

Routine treatment

Dapsone? Antivenom not

widely available


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BLACK WIDOW SPIDER BITES

Found throughoutUS & worldwide

Red hourglass Neurotoxic venom

Pain but NO

necrosis Abdominal rigidity

Rx = antivenom


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OTHER ARTHROPODSDIRECTLY CAUSING DISEASE

Allergic reactions

Bites/Stings

Dust mites/Cockroaches

Myiasis


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ARTHROPODS AS

VECTORS


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VECTOR-BORNE

DISEASES

MAJOR VECTORS:1. MOSQUITOS

2. TICKS

3. FLEAS


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MOSQUITO-BORNE

DISEASES


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DENGUE FEVER

Dengue virus is a flavivirus Transmitted by aedes mosquitoes Composed of single-stranded RNA

Has 4 serotypes (DEN-1, 2, 3, 4)


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TRANSMISSION OF DENGUE VIRUS


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CDC Dengue Map


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DENGUE IN THE UNITEDSTATES

Small risk for dengue outbreaks in US endemic & among travelers

Treatment:

Supportive care: fluids, rest, antipyretics

Monitor blood pressure, hematocrit,platelet count, level of consciousness


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YELLOW FEVER

Flavivirus transmitted byAedes

mosquito

Illness varies from flu-like to severehemorrhagic fever

Case fatality rate of up to 20%


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YELLOW FEVER DISTRIBUTION

Endemic areas: Africa/South America


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YELLOW FEVER VACCINE

Effective vaccine is available

Side effects are generally mild, flu-like

symptoms

Rare occurrence of seriouscomplications encephalitis, yellow

fever vaccine-associated viscerotropicdisease (YEL-AVD)


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WEST NILE VIRUS

WNV isolated inUganda in 1937

First identified in theUS in 1999

Important publichealth problem in US

Recent fatality in GAfrom WNV

Culex mosquito laying eggs
http://www.cdc.gov/ncidod/dvbid/westnile/culex-image.htm


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WEST NILE VIRUS:EPIDEMIOLOGY

Peak incidence: August September

Transmission occurs primarily via bite of

infected mosquito Mosquitoes are infected by feeding on

infected birds

Secondary modes of transmission :

Organ transplant

Blood transfusion

Breastmilk/transplacental

Occupational exposure


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WEST NILE VIRUS

Clinical suspicion is key to making earlydiagnosis

80% never develop clinical symptoms

Mild Disease: West Nile Fever

Severe Disease: West Nile Meningitis,

West Nile Encephalitis, and West NilePoliomyelitis


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WEST NILE VIRUS

Supportive treatment

Clinical trials for alpha-interferon

WNV is on the list of nationallynotifiable arboviral encephalitides

GA also investigates dead birds


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OTHER MOSQUITO-BORNEILLNESSES

Malaria

Lymphatic filariasis

Rift Valley fever Other encephalitides:

Eastern equine encephalitis

St. Louis encephalitis Western equine encephalitis

Japanese encephalitis


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PREVENTION OF MOSQUITO-BORNE ILLNESS

Primary prevention relies on measuresto decrease mosquito bites

Insect repellants: Permethrin, DEET,Picaridin, Oil of lemon eucalyptus

Protective clothing

Environmental control


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TICK-BORNE DISEASES


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TULAREMIA

Pathogen: Francisellatularensis

10 organisms cancause disease

Vector: Deer flies,Dermacentor &

Amblyomma ticks Occurs throughout N.

America & Europe
http://www.emedicine.com/cgi-bin/foxweb.exe/makezoom@/em/makezoom?picture=/websites/emedicine/emerg/images/Large/4751_127tickscrapvariab.jpg&template=izoom2http://en.wikipedia.org/wiki/Image:Fliege_auf_Holzbrett.jpg


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TULAREMIA

Multiple clinical syndromes

Clinical course: febrile, flu-like attack

Cutaneous form is most common

Inhalational form is most likely routefor BT attack

Vaccine under FDA review

Treatment = streptomycin


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LYME DISEASE

Pathogen: Borreliaburgdorferi

Vector: Black-legged orDeer Tick (Ixodes)

Occurs throughout the USbut majority of cases inthe Northeast and Great

Lakes area Most common vector-

borne infxn in US
http://upload.wikimedia.org/wikipedia/commons/8/88/Ixodes_scapularis.png


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LYME DISEASE

Stage 1: EarlyLocalized

Stage 2: EarlyDisseminated

Stage 3: LateChronic

Clinical Diagnosis Treatment:

doxycycline
http://upload.wikimedia.org/wikipedia/en/e/ed/BullseyeLymeDiseaseRash.jpg


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SOUTHERN TICK-ASSOCIATEDRASH ILLNESS

Pathogen: BorreliaLonestari??

Vector: Lone StarTick (Amblyommaamericanum)

Southern US &along coast toMaine


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STARI

Erythema migrans No arthritis, neurological or chronic

symptoms

True incidence unknown


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OTHER TICK-BORNE DISEASES

Rocky Mountain Spotted Fever

Ehrlichiosis

Babesiosis

Relapsing Fever

Colorado Tick Fever

Tick-Borne Relapsing Fever

Tick Typhus


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PREVENTION OF TICK-BORNEDISEASE

Proper clothing

Combination of skin & clothing

repellantAvoid grassy areas with shrubs

Perform daily skin checks for ticks


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FLEA-BORNE DISEASES


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PLAGUE

Pathogen: Yersiniapestis

Vector: Oriental ratfleas (Xenopsyllacheopsis)

Occurs worldwide:

1000 3000 casesannually


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PLAGUE

Most common form = bubonic plague(swollen, tender lymph nodes)

Pneumonic plague: high fever, cough,hemoptysis, difficulty breathing

50 - 60% case fatality without abx

Treatment: streptomycin

2nd line: gentamicin, tetracyclines


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THANK YOU!


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SOURCES

The Physicians Guide to Arthropods ofMedical Importance

Introduction to Medical Entomology www.cdc.gov

www.who.int

http://www.wikipedia.org/ (For all thegreat pictures!)
http://www.cdc.gov/http://www.who.int/http://www.wikipedia.org/http://www.wikipedia.org/http://www.who.int/http://www.cdc.gov/

Arthropod Disease 9_2007

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