biology and control of insects and rodents workshop vector...

Biology and Control of Insects and Rodents WorkshopVector Borne Diseases of Public Health Importance

Copyrighted Material ~ All Rights ReservedCourse Materials for NEHA-CERT Course IRW0601

Vector-Borne Diseases of Public Health Importance

Rudy Bueno, Jr., Ph.D.

Director

Components in the Disease Transmission Cycle

PathogenAgent that is responsible for disease

VectorAn arthropod that transmits a pathogen

ReservoirSum total of all pathogen sources; maintenance host

Susceptible hostHost in which a pathogen can survive with manifestation of clinical symptoms usually



Rodent Borne Diseases of Public Health Importance

Hantavirus: What is It?

Hantavirus is carried in the urine, saliva, or droppings of infected rodents such as deer miceHantavirus may result when the virus is breathed, swallowed, rubbed into the eyes, or touches broken skinThe chance of getting the hantavirus infection increases as contact with rodents or their nesting areas increasesYou cannot get the illness from another person, flies, or insectsCats and dogs do not get the virus



Hantavirus Epidemiology

Earliest known case, 1959Nearly all cases involve close interaction with rodentsEach hantavirus appears to be host specificDeer mouse is highly adaptable but generally not found in urban areasPeak season for hantavirus in U.S. is May through October

Possible Carriers of the Hantavirus

The deer mouse is the primary carrier4 to 9 inches long from head to tailColor from pale gray to reddish brownWhite fur on its belly, feet, and underside of tailPasses through holes as small as a shirt button

Deer Mouse



Healthy Lungs

Diseased Lungs



Plague: What is It?

A flea transmitted disease caused by the bacteria, Yersenia pestisRodents are the primary carriers of plaguePredominately found in the Western states-AZ, NM, CO, CADomestic pets, especially cats, are very susceptible and can be fatal

McDowell et al. 1964.

Plague bacteria, Yersenia pestis



Flea Vector

Rock squirrel host, Spermophilus variegatus

Other rodentsPrairie DogsWoodratsChipmunksField mice

Three Forms of Plague

Bubonic plague-most common form; usually transmitted by a flea bite with characteristic swollen lymph nodesSepticemic plague-bacteria invades the blood stream causing toxic poisoning; difficult to diagnosePneumonic plague-bacteria invade the lung tissue; can be spread from person to person through air droplets; most dangerous form



Plague Symptomology

2-6 day incubation periodHigh feverLethargyLoss of appetiteSwollen lymph nodesAbdominal distressShortness of breathCoughing

Bubonic Plague



What is Tularemia?Bacterial pathogen, Francisella tularensis

Gram-negative coccobacillusRabbit fever, deer fly feverMaintained and amplified in nature

Vertebrate reservoirsArthropod vectors

Ticks, mosquitoes, deerflies, fleas, lice

100-200 cases annually in U.S.



McDowell et al. 1964.

Tularemia Cycle

Human TransmissionInfection from skinningArthropod bitesIngestion-rareInhalation-rare3-5 day incubation5-10% fatality with no treatment

<1% if treated



Plague/Tularemia SimilaritiesBacterialSymptomsSeasonalitySepticemic or pneumonicOverlapping geographic distributionTreatment

Plague/Tularemia Differences

VectorsTicks/deer flies-tularemiaFleas-plague

Primary susceptible hostRabbits-tularemiaRock squirrels-plague

Plague/Tularemia Differences

Susceptible domestic animalsDogs-tularemiaCats and possibly dogs-plague

Human involvementNot common-tularemiaMore Common-plague



Mosquito-Borne Diseases

Important Strains in the U.S.

Eastern Equine Encephalitis

Atlantic and Gulf Coast

LaCross EncephalitisMid-western & mid-Atlantic states

St. Louis EncephalitisVery commonFound nationwide

Western Equine Encephalitis

West of the Mississippi River to Pacific Coast

What is Encephalitis?A virus causing inflammation of and destruction of brain tissuePrimarily transmitted by mosquitoesSeasonal with peaks in midsummer to fallExhibit amplification cycles in susceptible hostsTransmission from year to year depends on overwintering mechanism



Vectors of West Nile Virus in Harris County, TX Cx. quinquefasciatus, the Southern House Mosquito

Aedes albopictus, the Asian Tiger Mosquito



WNV SymptomologyIncubation period, 5-15 daysMost people have no symptoms or have mild symptoms such as

fever, headache, and body-aches (flu-like symptoms), often with a skin rash and swollen lymph glands.

Severe symptoms includehigh fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and in some cases death.

Geographical Information System: Tracking Diseases

Wk.24:6/11-6/15, 2002 (17)

Wks. 21-24:5/20-6/11,2003 (9)

Wks.Wks.22-24:6/3-6/18, 2004 (9)

Wks.6-24:2/12-6/15,2005 (14)



Wks. 18-21:5/2-5/25,2006 (18)

Dengue and Yellow Fever: (Ae. aegypti) and Asian Tiger (Ae. albopictus) Mosquitoes



Water storage container, backyard breeding habitat for Aedes aegypti.

Photo: WHO/TDR/Crump

Change in Distribution of Aedes aegypti in the Americas

PositiveEradicated/Died outStatus unknownIntercepted, not established

CDCCenters for Disease Control

and Prevention

PositiveEradicated/Died outStatus unknownIntercepted, not established

Aedes albopictus, in the United States, 1999



Symptoms of DengueCalled “breakbone fever”Severe headache, pain behind the eyes, backache, pain in the joints, severe rashIncubation period 5 – 6 days4 strains of dengue virusExposure to a second strain may result in dengue hemorrhagic fever

Severe Manifestation of Dengue Hemorrhagic Fever

(Photo: WHO/TDR/STI/Hatz)



Anopheles gambiae, Vector of Malaria

(Photo: WHO/TDR/Stammers)

Anopheles Breeding Site in Rice Paddy Fields, Thailand

(Photo: WHO/TDR/Crump)

Cleaning Weeds and Stagnant Water, Colombia




Sleeping under insecticide treated bednet

Photos: WHO/TDR/Crump

Treating House with Pyrethroids, in Thailand




The End: Questions?????

Links

http://www.dshs.state.tx.us/default.shtm

http://www.harriscountyhealth.com/

http://www.cdc.gov/page.do

http://www.who.int/en/

http://www.cabq.gov/

http://www.health.state.nm.us/

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