Ectoparasites + Other Blood Feeding Insects as Vectors

M.7, W.4

what is an ectoparasite?

parasite that lives on surface of host, feeding on blood or tissue

what does an ectoparasite never do?

never goes into internal organs of host

What is arbovirus?

virus transmitted by arthropods to humans or animals

where is an arbovirus replicated and how is it transmitted?

virus replicated within arthropod

transmitted to host through bite

what is a DNA virus?

- virus has DNA as genetic material

- replicate in host cell’s nucleus

- more stable; less prone to mutations

what is a RNA virus?

- virus carries RNA

- replicates in cytoplasm

- mutates more frequently

What is biological transmission?

virus replicates inside vector, then transmitted to new host

What is mechanical transmission?

Vector carriers virus on body or mouthparts (no replication in vector)

- vector carries + transmits virus from one host to another without becoming infected itself

What is vertical transmission?

virus passed from parent to offspring

What is horizontal transmission?

virus passed between individuals (typically arthropod vector to host)

List three species of mosquitoes.

1. Aedes

2. Anopheles

3. Culex

What diseases do Aedes mosquitoes spread?

Dengue, Zika, Chikungunya, Rift Valley Fever, Yellow fever

What time of day do aedes mosquitos feed?

Day time - early morning, late afternoon

What is the ideal breeding environment for aedes mosquitoes?

Small water containers + urban environments

What diseases do anopheles mosquitoes spread?

Malaria, O'nyong-nyong

What time of day do anopheles mosquitos feed?

Dusk to dawn

What is the ideal environment for anopheles mosquitoes?

Clean, still bodies of water (ponds, marshes, rice fields)

What diseases do culex mosquitoes spread?

West Nile Virus, Japanese encephalitis, Lymphatic Filariasis

what time of day do culex mosquitos feed?

at night

what is the primary host for culex mosquitos?

birds

What is the ideal environment for culex mosquitoes?

Polluted, stagnant water

list 5 reasons why mosquitos are good disease vectors?

1. wide host range

2. blood meals = increase contact time w/ host

3. some pathogens complete lifecycle w/in host

4. travel over large areas

5. breeding habitats near humans

list some control methods for mosquitos

• Chemical - Indoor Residual Spraying (IRS)

• Biological and Genetic - Predators (fish)

• Environmental - remove standing water

• Physical - fine mesh screens

Lists 5 species of ticks

Hard Ticks: Ixodes, Rhipicephalus, Amblyomma, Dermacentor

Soft Tick: Argasidae

What diseases do Ixodes ticks spread?

Lyme, Tick Borne Encephalitis (TBE)

What disease do rhipicehalus ticks spread?

East Coast Fever - cattle

Rocky Mountain Spotted Fever - humans

What disease do Amblyomma ticks spread?

Ehrlichiosis, Heartland virus

What disease do Dermacentor ticks spread?

Rocky Mountain Spotted Fever, Tularemia

What disease do Argasidae ticks spread?

Tick-borne Relapsing Fever (TBRF), African swine fever

what species of Argasidae ticks spread African swine fever to pigs?

Ornithodoros moubata

How long do Ixodes ticks attach?

Several days

How long do rhipicephalus ticks attach?

Long periods of time

How long do amblyomma ticks attach?

Long periods

How long do argasidae ticks attach?

Feed quickly, only minutes

What is the ideal environment for Ixodes ticks?

Forested, grassy areas, high humidity

What is the ideal environment for rhipicephalus ticks?

Warmer climates

What is the ideal environment for amblyomma ticks?

warm, tropical + subtropical climates

What is the ideal environment for Dermacentor ticks?

Grassy, brushy, wooded areas + temperate climates

What is the ideal environment for Argasidae ticks?

live in close proximity to hosts

what are the hosts for Rhipicephalus ticks?

livestock (mainly cattle), dogs

what are the hosts for Amblyomma ticks?

wide range of hosts

what are the hosts for Dermacentor ticks?

humans, dogs, wild animals

list reasons why mosquitos are good disease vectors?

1. long feeding duration

2. multiple life stages feeding on dif. hosts

3. transstadial and transovarial transmission

4. environmental hardiness

5. broad range of hosts

list some control methods for ticks

• chemical - acaricides on livestock/pets

• Biological & Genetic - entomopathogenic fungi targeting tick larvae

• Environmental - clearing vegetation to reduce tick habitats

What is ideal environment for fleas?

Homes, farms, close human-animal contact areas

List 3 important species of fleas.

1. Ctenocephalides Felis (Cat Flea)

2. Pulex Irritans (Human Flea)

3. Xenopsylla Cheopis (Rat Flea)

What diseases are spread by Ctenocephalides felis?

Cat scratch disease, murine typhus

What diseases are spread by pulex irritans?

Yersinia pestis (plague), Murine typhus

what diseases are spread by Xenopsylla Cheopis?

plague

what are the life stages of a flea?

• eggs laid on host then fall off

• larvae and pupae develop in environment then reinfect new host

why are fleas good disease vectors?

1. High repro rates

2. Bite multiple hosts

3. can infest mobile hosts (rats)

4. environmental hardiness

5. can parasitize wide range of hosts

list control methods for fleas

• chemical - topical treatments on pets

• Biological and genetic - nematodes introduced in infested areas

What diseases are spread by culicoides (biting midges)?

Blue tongue virus (cattle), African horse sickness virus

what is the ideal breeding environment for culicoides?

wet, marshy areas

why are culicoides good disease vectors?

1. tiny size + silent feeding

2. large swarms + widespread distribution

3. transmit variety of pathogens

4. rapid repro cycle

5. preference for specific hosts

what are control methods for culicoides?

• chemical - insecticides

• Physical - insecticide treated nets + fine mesh screens

List 3 species of flies.

1. Phlebotomus (Sandflies)

2. Stomoxys calcitrans (Stable Fly)

3. Glossina (Tsetse Fly)

what do Phlebotomus flies transmit?

Leishmaniasis & Sandfly Fever

what time of day do Phlebotomus flies feed?

night time

what is the ideal environment for Phlebotomus flies?

Deserts & semi-arid regions

list methods of control for Phlebotomus flies

Chemical - residual spraying on walls

Physical - Insecticide treated nets & fine mesh screens

why are Phlebotomus flies good disease vectors?

1. feed at night = avoid host defenses

2. broad host range

3. wide geographic range

4. Efficient pathogen transmission

what kind of vector is a Stomoxys calcitrans fly?

mechanical

what diseases do Stomoxys Calcitrans flies transmit?

Anthrax & Equine Infectious Anemia Virus

what is the ideal breeding environment for Stomoxys Calcitrans flies?

decaying organic material on farms

list methods of control for Stomoxys Calcitrans flies

• chemical - insecticide sprays or fly traps

• biological & genetic - release of parasitic wasps

• environmental - manure management to eliminate breeding sites

why are Stomoxys Calcitrans flies good disease vectors?

1. Frequent bites

2. Mechanically transmitted diseases

3. Highly adaptable to environment

4. Widespread breeding in decaying organic matter

what diseases do Glossina flies transmit?

• African Trypanosomiasis (sleeping sickness in humans)

• Nagana (cattle)

what time of day do Glossina flies feed?

Day time

what is the preferred environment for Glossina flies?

Sub-saharan Africa & Riverine + savanna areas

list control methods for Glossina flies

• chemical - insecticide treated targets

• Biological & Genetic - sterile insect technique

• Physical - traps and targets to lure + kill flies

list why Glossina flies are good disease vectors?

1. Exclusively feed on blood

2. long lifespan

3. pass pathogens to offspring

4. influence disease spread by thriving in specific habitats

List several ways to control ectoparasite populations.

Chemical, biological/genetic, environmental/physical