Vector Biology Flashcards
What are the diseases transmitted by this vector?
Anopholes Mosquito
Malaria
Lymphatic Filariasis
O Nyong Nyong
How long is the lifecycle of a mosquito?
10-14 days
What is a Spermatheca
ball of sperm that a female carries with her for the rest of her life from her first sexual encounter.
She dips in and out of this when she wants to lay more eggs
What is the flight range of mosquitos?
1-3km
What cues help a mosquito to find its prey for a blood meal?
olfactory cues: CO2, synergists: lactic acid, octenol, acetone
other cues: water vapor pressure, warmth, visual cues
NOTE that a proportion of these increase in pregnancy, which is why pregnant women are at an even greater risk of malaria
Which mosquitoes require blood meals?
Females producing eggs
Survival of female is most important in disease epidemiology and control
Which type of mosquito is in each of the pictured resting positions?
A.
B
A. Anopheles
B. Culex/Aedes/Mansoni (culicine spp.)
Re: Anopheles twerk
Based on the photo:
- What mosquito?
- Male or Female?
Anopholes
Male
Palps are LONG and CLUBBED
How do Anopheles lay their eggs?
arranged as Floats
How do Culex lay their eggs?
Arranged as rafts
How do Aedes lay their eggs?
Singularly laid eggs
Resistant to dessication
Which larva is this? How does it breathe?
Anophales
Breathes through spiracles on its sides
What larva is this? How does it breathe?
Culex
Long siphon (compared to Aedes which is short and barrel shaped)
Identify the mosquito
Culex
Identify the Mosquto
Aedes
In regards to mosquitos, what does the term ‘anautogenous development’ mean?
Females require a blood meal to produce eggs
How to Mansonia species of mosquitos lay their eggs?
in a sticky mass that is glued to the underside of floating plants
Which mosquito eggs can handle dessication?
Aedes
Where are you likely to find Aedes eggs?
Water containers, tyres, clay pots, tree wells
What are the resting and feeding habits of Aedes?
Exophagic
Exophilic
(ive and eat outside)
What are the resting and feeding habits of Anopheles?
Endophagic
Endophilic
(Live and eat inside)
What part of the Malaria parasite cycle is injected into people when a mosquito takes a blood meal?
Sporozoites
What time do Anopheles typically feed?
Nighttime (hence why you take night time bloods in Lymphatic Filariasis in areas where Anopheles are the vector)
Which filarial worms are transmitted by Anopheles?
Worms responsible for Lymphatic FIlariasis:
Wuchereria Bancrofti
Brugia Malayi
Brugia Timori
Re: Lymphatic Filariasis, What is the difference between nocturnal periodicity and sub-periodicity?
Nocturnal periodicity = the highest blood parasite count at night
Subperiodic = pretty stable levels throughout the day, highest around midday
What is the most important arbovirus that can be transmitted by Anopheles?
O Nyong Nyong (note that there about 20 other arboviruses that are spread by anopheles, but they are not epidemiologically or clinically important)
How can you manage Anopheles populations?
Larval control
- Mass Insecticide Spraying
(pyrethroid based insecticides)
- BTI (Bacillus thurnigenesisi Israelius)
- Larvicidal Fish
- Draining Swamps and marshes
Adult Control
- Residual House Spraying (also kills bed bugs, cockroaches)
- ITNs
Where do Culex lay their eggs?
Dirty water, ground water, rice fields, sewage
**assocaited with urbanisation, loves filth, dity culex
How can you control Aedes populations?
Elimiante water container
Imtroduce stable sources of water in the community to prevent people from keeping stagnant water at home
Ground-based insecticides
Insecticides that are released with water activation (i.e. when the eggs are activated to hatch)
Daytime sleepers should use bed nets
Which continent contains most cases of Yellow Fever?
Africa (90%)
How can you control Culex populations?
Improve sewage
Insecticides
Polystyrine beads in pit latrines
What is the epidemiology of Aedes Aegypti?
**all global Aegypti have come from Africa via trade routes
So:
SSA
South America
Asia
Australia and the Pacifics
What are the 4 most important arboviruses spread by Aedes Aegypti?
Yellow Fever
Dengue
Chikungunya
Zika Virus
Incidence of arboviruses is increasing - whty?
People are favouring urbanisation, which is preferential breeding ground for Aedes mosquitoes
Insufficient amount of vaccinations
Climate changes –> improve vector survival rates, vector population distribution and density –> the higher the temp the fast the parasite development
Why are vector survival rates important for disease transmission?
- The longer a mozzie lives the more likely it is to take two bites (ie sread the disease)
- The mozzie needs to live long enough for the parasite/virus to develop within the gut of the mozzie
What are the hosts of Yellow Fever
Monkeys
Where does Yellow Fever Occur?
Africa (less severe)
South America (more severe –> sylvatic)
Which arboviruses have an Anxootic cycle?
West Nile Virus
Yellow Fever
Dengue
Japanese Encephalitis
Venezuelean Equine Encephalitis
how can you control aedes aegypti?
- Source reduction
- Eliminate vector larval sites
- Eliminate useless containers
- Cover or treat useful ‘domestic’ water containers
- insert stable water source - Larvicides
- Temephos (OPP)
- BTI - Outbreak control
- fogging or space spraying (Pyrethroids; large amount of resistance) - Home improvements
- window and door screens (e.g. difference between vector issues in Southern USA vs Northern Mexico) - Insect growth regulator
- Pyriproxyfen (spread as dust) - Wolbachia
What is pyriproxifen?
An insect growth regulator which prevents the development of larval development into pupae
Why isn’t wolbachia present in Loa Loa?
Loa loa is spread by Deerticks, which are not compatible with wolbachia
What are the three important lice species?
Pediculus humanus
Pediculus capitis
Pthirus Pubis
What spp. are body lice?
Pediculus Humanus
What is the name of the Head Louce
Pediculus capitis
What is the name of the Pubic Louse
Pthirus Pubis
Identify the Louse
Body/Head louse
Identify the Louse
Pubic Louse
Which louse is a nuisance but does not spread disease?
Public Louse (Pthirus Pubis)
Head Louse (Pediculus Capitus)
How do lice spread disease?
Disease is carried in their stools, or in the case of relapsing fever found in the body fluids of the louse and infect you when you crush the body
Which louse acts as a disease vector?
Pediculus Hominus
What three diseases are spread by louse?
Louse borne endemic typhus (Rickettsia Prowazeki)
Trench Fever (Bartonella Quintana)
Epidemic Relapsing Fever (Borrelia Recurentis)
What is the bacteria in Louse Borne Epidemic Typhus?
Rickettsia Prowazeki
How does LBET present?
Headache, prostration, chills, cough, severe muscle pain
What is the case fatality of LBET?
40%
How does LBET transmit?
*Louse picks up Rickettsia in blood meal invade midgut epithelium and multiply rupture⇒ ⇒
into gut lumen (louse dies) enormous number in gut faeces⇒
*infection through rubbing louse faeces in conjuctiva or inhalation
*faeces may be infective for >70 days
What is the epidemiology of LBET?
*Mainly occurs in colder regions of Africa (esp Great Lakes Region) and S/C. America
*Huge pandemics (millions of deaths in 1st half of 20th Century, Burundi 1997- 100,000 cases)
What bacteria causes Trench Fever?
Bartonella Qunitana
How does Trench Fever Spread?
*bacteria remain in gut lumen and do not kill the louse
*infection via faeces
What are risk factors for louse-borne diseases?
Poor sanitation
Crowding
Homeless populations
IDPs/refugees
What bacteria causes endemic relapsing fever?
Borrelia Recurrentis
How is endemic relapsing fever spread?
*spirochaetes in host blood penetrate gut wall into haemocoele where they multiply
in gut lumen and do not kill the louse
*louse must be crushed to infect humans spirochaetes enter through mucosa/cuts
etc
How can you control Head lice?
–washing with soap and water will reduce numbers but will not rid
infestation
–regular use of lice comb (every 3 days for 2 weeks)
–Insecticides (usually pyrethroids with PBO) (3x weekly applications)
–Dimectone lotion or spray
–shaving of head hair
How can you control Pubic Lice?
–Traditionally-shaving of all coarse hair
–Insecticides
–Emulsions and lotions applied to entire body (do not wash for 24 hours
post application)
–For eyelashes
*Vaseline
*0.25% physostigmine opthalmic ointment (10 day course)
How can you control Body Lice?
–Frequent washing/changing of clothes and bedding, drying in direct sunlight
–Delousing using insecticides e.g permethrin dust
What diseases are caused by fleas?
plaque
Murine typhus
tapeworm
There are two types of fleas: combed and combless. Which ones are harmless cat/dog fleas
Combed
What fly causes Jigger infestations
Tunga Penetrans
What is this vector?
Cat flea - combed and has a merel rod
Name this insect
Tropical Rat flea (xenopsylla)
Meral rods and combless
When meryl streep goes on holiday to the tropics she doesnt bring her comb
What rats are associated with plague?
Rattus norvegicus
Rattus rattus
What is the main flea vector of Plague?
Xenopsylla cheopis
What bacteria causes Murine Typhus?
Rickettsia Typhi (mooseri)
Which tapewrom is spread by fleas?
Dipylidium canium
When controlling flea populations:
Do you kill the fleas or the rats?
The fleas!!
Killing the rats will just make the fleas spread faster
How can you control Xenopsylla?
Residual insecticide spraying of domestic rat runs and burrows
Treat all dwellings <200m within the affected on in an endemic
Insecticides
Bamboo bait boxes
dichlorvos resin strips on container ships
How do you control RODENTS in plague infestation (once you have killed the fleas)
Rodenticides (warfarin)
Rodent cheomsterilisation
Methyl Bromide gas
Where do Tunga Penetrans (Jiggers) exist?
Americas
Africa
India
What is the main vector of Myiasis in Africa?
Cordylobia anthropophaga, also known as Tumbu fly, Mango fly or Putzi fly.
What is the main vector of Myiasis in South America?
Dermatobia hominis, the human botfly.
Unlike the Tumbu fly, this species lays its eggs directly on exposed skin
How does management differ in Cordylobia Myiasis vs. South Dermatobia Myiasis?
Dermatobia usually has spines, which means extraction can be difficult –> needs to be excised using cruciate incision
Cordylobia can be suffocated with petroleum/parrafin
What vector is responsible for Scabies and Norwegian Scabies?
Sarcoptes scabiei
Identify this and state a disease it might spread
Soft Tick
Tick Borne relapsing Fever (B. .Duttoni)
What is this ectoparasite?
Sarcopotes Scabei
Identify the ectoparasite
Chigger Mite
(Looks similar to Scabies, but has an extra set of legs AND is hairy)
What is the ecosystem in which you would find Chigger Fleas
Asia
Jungles, gardens, wood piles
How can you protect against Chigger bites?
- Wear boots and long trousers
- Clothing impregnated with
- repellent (DEET, DMP, benzyl benzoate)
- permethrin
- Avoidance of mite islands
- Clearance or burning of mite islands
- Acaricide spraying (ULV, fogs or emulsions)
- Chemoprophylaxis (200mg weekly doxycycline) of high risk groups, eg soldiers in field
Identify this.
Musca Domestica (house fly)
4 grey stripes on dark thorax
Wing vein 4 bends to meet vein 3
What do houseflies feed on?
Houseflies visit and feed readily on:
* faeces
* vomit
* garbage
* …and food
*** they also really love to breed in dirty things - manure, compost bins, garbage etc.
What diseases do houseflies transmit? (through contamination of food) (3)
Shigella
Salmonella
E. coli
Cholera
Enteroviruses
Including polio
Helminth eggs (?)
How can you reduce the prevalence of flies?
Daltemethrin insecticide
Fly traps around high risk areas
Good waste disposal
Improve food storage
Disposal of human excreta
What fly is responsible for transmitting Trachoma eye infection?
Musca Sorbens
Identify the fly
Stomoxys (stable fly)
Note the large probiscus for biting (house flies do not have a proboscis)
What fly causes Myiasis in Africa?
Tumba Fly (Cordylobia Anthropophagia)
How do humans get Myiasis from the Tumba Fly?
Lays eggs on urine soaked clothes or sandy soil
Myaisis (boil like swellings) typically occur around genitals, buttocks, back
Identify the larve
Tumba Fly (Cordylobia anthropophagia)
How can you manage and prevent Cordylobia myiasis?
REMOVAL: paraffin suffocation of larva –> easy to remove when it pops its little head out to breathe
PREVENTION:
Wash clothes, iron at high heat
What is New World Myiasis?
Infection from Dermatobia larva via eggs being deposited on skin by flys or mozzies
Identify the larva
Dermatobia
Identify the larva.
Describe its clinical significance
Screw worm
Feed on human flesh
* Obligate parasites of living tissues
* Very serious since they consume living tissue
* Can invade natural orifices nose, mouth, eyes, vagina etc
* Severe tissue trauma and pain
* Larvae with spines giving a screw-thread appearance.
What flies cause non-invasive myiasis (ie. only eat dead tissue)?
Blue-bottles (Calliphora) Green Bottles (Lucilia)
