Vectors and Zoonotic Diseases

Arboviral Encephalitides (WNV, WEE, SLE)

Mosquito-borne viruses maintained in wild birds; Culex tarsalis bites transmit to humans causing mild flu-like illness that can progress to severe neurological disease, coma, or death.

Chagas Disease

Protozoan Trypanosoma cruzi carried by opossums and woodrats; reduviid (kissing) bugs defecate during feeding, parasites enter skin when scratched; ranges from asymptomatic to acute fever, malaise, eyelid edema, and lymphadenopathy.

Cryptococcosis

Fungus Cryptococcus neoformans grows in pigeon droppings; inhalation of contaminated dust leads to pulmonary infection and potentially fatal meningitis or systemic disease (skin, bone, kidneys).

Hantavirus Pulmonary Syndrome

Sin Nombre virus shed by deer mice; inhalation of aerosolized urine or feces causes 1–2 week flu-like prodrome that rapidly progresses to severe respiratory distress; ~40 % fatality.

Histoplasmosis

Fungus Histoplasma capsulatum found in soil enriched with bat or bird guano; inhaled spores cause asymptomatic infection or acute respiratory disease that may disseminate to liver, spleen, kidneys—mimicking tuberculosis.

Leptospirosis

Over 200 Leptospira serovars harbored by wild & domestic mammals; entry through abraded skin or mucous membranes via urine-contaminated water; presents with fever, chills, myalgia and may involve meningitis or encephalitis.

Lyme Disease

Spirochete Borrelia burgdorferi cycles in wild rodents and deer; transmitted by Ixodes (black-legged) ticks; early expanding erythema migrans rash, flu-like symptoms; untreated cases progress to arthritis and neurologic disorders.

Lymphocytic Choriomeningitis (LCM)

LCM arenavirus carried by house mice; exposure to aerosolized or food-borne urine/feces leads to fever, headache, myalgia, possible meningitis; deaths are rare.

Murine Typhus

Rickettsia typhi maintained in commensal rodents and opossums; fleas transmit via bites or feces; causes fever, headache, myalgia, trunk-centered rash; <1 % fatality.

Psittacosis (Ornithosis)

Chlamydophila psittaci infection from parrots, parakeets, and other birds; inhalation or handling of contaminated feces/secretions leads to fever, headache, chills, and atypical pneumonia with chest pain.

Plague

Yersinia pestis circulates among wild rodents; infected flea bites, contact with tissues, or inhalation of droplets cause bubonic, septicemic, or pneumonic plague marked by painful lymphadenopathy and high mortality if untreated.

Rabies

Lyssavirus spread by bites or saliva of bats, skunks, and other mammals; after 3–12 week incubation, fever and malaise progress to encephalitis, paralysis, and death within days of symptom onset.

Rat-bite Fever

Streptobacillus moniliformis from rat saliva or urine; bite or exposure leads to fever, chills, rash, arthralgia, and potential endocarditis or meningitis.

Rickettsialpox

Rickettsia akari transmitted by mite bites from house mice; local eschar followed by generalized vesicular rash sparing palms/soles and regional lymphadenopathy.

Rocky Mountain Spotted Fever

Rickettsia rickettsii maintained in ticks and wild rodents; tick bite causes high fever, headache, myalgia, and petechial rash (trunk → extremities); untreated fatality up to 80 %.

Salmonellosis

Numerous Salmonella enterica serovars from contaminated food/water or reptile pets; sudden onset diarrhea, abdominal pain, fever, nausea, and headache.

Tick-borne Relapsing Fever

Borrelia hermsii carried by rodents and transmitted by soft (Ornithodoros) ticks; recurring high fevers (up to 106 °F) separated by afebrile periods.

Tularemia

Francisella tularensis infection from rabbits or rodents via handling, ingestion, inhalation, or tick bite; causes ulceroglandular lesions, painful lymphadenopathy, pneumonia, or typhoidal illness.

Zoonoses

Diseases that are naturally transmitted from non-human animals to humans.

Reservoir

The habitat (human, animal, or environment) in which an infectious agent normally lives, grows, and multiplies.

Host

Any susceptible organism that can be invaded by an infectious agent.

Intermediary Host

An organism that harbors a pathogen for a short period before it reaches its definitive host.

Vector

Any living agent, often an arthropod, that carries and transfers a pathogen to another organism.

Symbiosis

A relationship in which two organisms live in close association, which may be beneficial to one or both.

Parasite

An organism that lives on or in a host organism and causes it harm.

Delusional Parasitosis

A psychiatric condition in which a person believes they are infested with living or non-living pathogens.

Epidemiological Triangle

A model describing disease causation with three components: agent, host, and environment.

Biological Transmission

Pathogen spends part of its life cycle in the vector, multiplying before being transmitted (e.g., malaria in mosquitoes).

Mechanical Transmission

Pathogen is physically carried on body parts of the vector without development inside the vector (e.g., flies spreading bacteria).

Arboviral Encephalitis

Inflammation of the brain caused by arthropod-borne viruses such as West Nile virus.

West Nile Virus

A flavivirus transmitted primarily by Culex mosquitoes that can cause fever or encephalitis.

Bubonic Plague

Form of plague caused by Yersinia pestis, characterized by swollen lymph nodes; transmitted mainly by rodent fleas.

Septicemic Plague

Plague infection of the bloodstream caused by Yersinia pestis; can arise from untreated bubonic plague.

Pneumonic Plague

Severe lung infection with Yersinia pestis, transmissible person-to-person via respiratory droplets.

Chagas Disease

American trypanosomiasis caused by Trypanosoma cruzi and spread by kissing bugs (Triatominae).

Schistosomiasis

Parasitic flatworm infection acquired through skin contact with freshwater containing cercariae from snails.

Lyme Disease

Tick-borne infection by Borrelia burgdorferi causing erythema migrans and multi-system symptoms.

Malaria

Mosquito-borne disease caused by Plasmodium parasites, transmitted by female Anopheles mosquitoes.

Rocky Mountain Spotted Fever

Rickettsia rickettsii infection transmitted by ticks, leading to fever and spotted rash.

Tularemia

Bacterial disease caused by Francisella tularensis; spread by deer flies, ticks, or contact with infected animals.

Typhus

Group of rickettsial fevers transmitted by lice, fleas, or chiggers; includes epidemic, endemic (murine), and scrub typhus.

Epidemic Typhus

Severe typhus caused by Rickettsia prowazekii and spread by body lice.

Murine (Endemic) Typhus

Milder typhus caused by Rickettsia typhi (or R. felis) transmitted by fleas from rats and other rodents.

Yellow Fever

Acute viral hemorrhagic disease caused by a flavivirus and transmitted by Aedes or Haemagogus mosquitoes.

Hantavirus Pulmonary Syndrome

Severe respiratory disease caused by hantaviruses spread mainly via aerosolized rodent excreta.

Histoplasmosis

Fungal lung infection from inhaling Histoplasma capsulatum spores in soil or bird/bat droppings.

Leptospirosis

Bacterial zoonosis caused by Leptospira species, acquired through contact with water or soil contaminated by animal urine.

Psittacosis

Parrot fever in humans caused by Chlamydia psittaci, transmitted from infected birds.

Rabies

Almost invariably fatal viral encephalitis transmitted through saliva of infected mammals, especially bats and skunks in CA.

Head Louse

Pediculus humanus capitis; small wingless insect causing scalp infestation, spread by head-to-head contact.

Body Louse

Pediculus humanus corporis; lives in clothing seams, can transmit epidemic typhus.

Pubic Louse

Pthirus pubis (‘crab’ louse); infests pubic and coarse body hair.

Bed Bug

Cimex lectularius; nocturnal blood-feeding insect, nuisance pest not known to transmit disease.

House Fly

Musca domestica; common synanthropic fly that can mechanically spread pathogens.

Lesser House Fly

Fannia canicularis; spring species often seen indoors, breeds in organic matter.

Myiasis

Infestation of live human or animal tissue by fly larvae (e.g., botflies).

Order Hymenoptera

Order of insects including wasps, bees, and ants; many species can sting.

Flea

Small wingless blood-sucking insect; vectors of plague (Yersinia pestis) and murine typhus (Rickettsia typhi).

Order Siphonaptera

Taxonomic order comprising all flea species.

Ixodidae

Family of hard ticks characterized by slow feeding and a dorsal scutum.

Argasidae

Family of soft ticks noted for rapid feeding and lack of a dorsal scutum.

Ixodes pacificus

Western black-legged tick; principal vector of Lyme disease in California.

Aedes aegypti

Domestic mosquito species, daytime biter, vector of dengue, Zika, yellow fever, and chikungunya viruses.

Aedes albopictus

Asian tiger mosquito; aggressive daytime biter and potential vector of several arboviruses.

Culex pipiens

Northern house mosquito; key vector of West Nile virus and St. Louis encephalitis in the U.S.

Culex tarsalis

Mosquito species transmitting West Nile, St. Louis encephalitis, and Western equine encephalomyelitis.

Anopheles Mosquito

Genus of mosquitoes that transmit human malaria; rest at a 45° angle to surfaces.

Mosquito Life Cycle

Four stages: egg, larva, pupa, adult; aquatic immature stages, flying adult stage.

Larvicide

Pesticide specifically targeting mosquito (or other insect) larvae.

Juvenile Hormone (JH) Analog

Growth regulator used to disrupt insect development and prevent maturation.

Integrated Pest Management (IPM)

Strategy combining monitoring, prevention, sanitation, exclusion, and minimal pesticide use to control pests.

Five Steps of IPM

Inspection, Identification, Threshold setting, Multiple control measures, Evaluation.

Norway Rat

Rattus norvegicus; large burrowing rat, coarse brown fur, blunt nose, capsule-shaped droppings.

Roof Rat

Rattus rattus; slender arboreal rat, tail longer than body, pointed nose, medium droppings.

House Mouse

Mus musculus; small agile rodent, brown-gray, small droppings up to ¼ inch.

American Cockroach

Periplaneta americana; large reddish-brown roach preferring warm damp sites like sewers.

German Cockroach

Blattella germanica; most common indoor roach, light brown with two dark stripes behind the head.

Brownbanded Cockroach

Supella longipalpa; small light-brown roach with two pale bands across wings; prefers warm, dry areas.

Oriental Cockroach

Blatta orientalis; dark-colored roach favoring cool damp sites like basements and sewers.

Acaricide

Pesticide formulated to kill mites and ticks.

Rodent-Borne Disease

Any infectious disease primarily maintained or transmitted by rodents (e.g., hantavirus, leptospirosis).

Tick

Blood-feeding arachnid that can transmit pathogens such as Borrelia, Rickettsia, and Babesia.

Western Black-Legged Tick

Common name for Ixodes pacificus, vector of Lyme disease in the western U.S.

Vector Control Technician Certification

California state program certifying government employees in public-health vector control.

CDC Light Trap

Battery-powered trap using light and CO₂ to collect adult mosquitoes for surveillance.

Bacillus thuringiensis israelensis (Bti)

Bacterial larvicide producing toxins specific to mosquito and blackfly larvae.

Bacillus sphaericus

Bacterial larvicide effective against Culex larvae; used in biological mosquito control.

Monomolecular Film

Thin surface oil layer that reduces water tension, drowning mosquito larvae and pupae.

Stagnant Water

Standing water that serves as prime breeding habitat for many mosquito species.