Sandflies Flashcards
What is the geographical range for sandflies?
As far north as France and as far south as Argentina. (50N, 40S)
How many spp of sandfly are there and how many transmit human disease?
> 700
>50
Describe the appearance of sandflies.
- Small (1/3 of a mosquito)
- Hairy (scales) (helps conserve water in arid conditions)
- Pointed wings (v shape above abdomen @ rest)
- Long spindly legs
- Parallel veins on wings (look striped)
How long is the sandfly lifecycle?
Quite long- egg to adult in 4-5 weeks.
How many eggs per oviposition?
10-120
How many instars do the larvae have?
4
What state is the pupa in?
Inactive state and has the skin of the 4th instar larvae.
Describe the eggs of sandflies. Where are they oviposited?
Brown or black, very small, species-specific chorion.
Usually oviposited in damp locations with lots of organic material (such as cracks in walls, animal burrows, caves, termite mounds, tree buttresses).
Describe the morphology of sandfly larvae.
0.5 cm 12 segments Strong mandibles to chew organic detritus Caudal bristles (on last segment) Matchstick hairs (characteristic)
What is the posited role of the matchstick hairs?
Locomotion and sensory function.
Describe the morphology of the pupa of sandflies. Where are they located and in what position?
Inactive and can see the skin of the last larval stage. Red/ brown colouration. Cement onto substrates that are away from excessively moist areas. Get glued in an upright positioning
What do adult sandflies feed on?
Both males and females take sugars (plant juices, fallen fruits, aphid booty lmao (aphid honeydew).
Describe what happens to the sugar meal following feeding.
Sugar is diverted to a specialised organ called the crop. The very frist part of the sugar meal passes through the stomodeal valve and the rest is diverted to the crop. It is sterilised (unknown mechanism) and then it is passed to the midgut.
Describe what happens to a blood meal.
Blood passes directly through the stomodeal valve into the midgut. The valve shuts when full to allow digestion.
Describe how sandflies feed on blood.
Are pool feeders- use short serrated mouthparts to break capillaries to form a pool of blood on which they feed.
Only females feed on blood.
Describe the host preferences of sandflies and how this plays a role in vectorial capacity/
host preference is dependent on the species of sandflies and therefore determines which species can be competent vectors e.g. if they do not ever feed on humans they cannot be vectors for human disease.
When do female phlebotomine sandflies feed?
Night/ early evening and just before dawn.
Describe how the structure of sandfly mouthparts are adapted for blood-feeding/ pool feeding.
Laciniae are behind the labarum and move back and forth to saw into the skin. Serrated mandibles push into the skin and saw independently.
Where are leishmania parasites located inside sandflies?
In the gut- they never leave the gut! When parasites are found in the haemolymph, they are thought to be damaged parasites.
Describe the mating of sanflies.
Do NOT swarm like mosquitoes and (most) other Diptera. They aggregate on surfaces that are attractive to females (for oviposition or feeding).
Males land first, secrete pheromones, flap wings to distribute these. Have a species-specific courting song and dance.
Sperm delivered in spermatophore via a sperm pump (like a hypodermic needle) to spermathecae
How are sandfly pheromones useful in identification?
Species specific pheromones have been used to identify cryptic members within a species complex.
How can male genital claspers be used to age a sandfly?
Male genital claspers undergo a 180 tip rotation within 24 hours of birth and so can allow ageing.
What are cibarial teeth?
Teeth before female sandfly stomodeal valve.
How do sandflies disperse? Describe their flying pattern. How does this affect the distribution of disease?
Don’t fly in strong wings but can disperse over 1.5km in light winds.
Flight becomes a characteristic hopping flight when they become close to a blood meal or the ground.
However, disease is focal as in dense vegetation, dispersal is less than 100m: sandflies tend to stay in the same area.
Describe the resting habits of sandflies.
Rest in dark, humid sheltered sites. Can be exo or endophilic depending on the species.
How do we collect sandflies?
This depends on the behaviour of the species of interest.
- Directly search resting sites
- Spray catches (spray insecticide and inspect sheet on the ground)
- Human landing catches
- Human bait
- Traps (interceptive sticky traps, attractive traps)
Why are attractive traps better than plain traps? What is the downside of traps?
Plain traps are likely to be stochastic. Traps rely on the LANDING of sandflies on the trap.
Why are human landing catches/ human bait ethically questionable?
Because there is no effective prophylaxis for leishmania.
Which sandflies are important in the old and new world respectively?
Phlebotomine in the old world and Lutzomyia in the new world.
Why are sandfly bites painful?
Damage skin, immune reaction, saliva amplifies sensation of bite.
What does a sensitised sandfly host mean?
Hosts previously exposed to the bite of a sandfly may have more severe irritations from the bite.
What do sandflies spread?
Leishmania, bartonellosis.
Where does Bartonella bacilliformis occur. Describe the course of infection. What is a characteristic feature of this disease? What is the outcome/ prognosis of the disease?
Andean foothills. Acute phase (fever, anaemia as they invade RBC), then chronic phase (>3 weeks, severe joint pain, immunosuppression).
Characteristic wart on the skin filled with the bacteria- allows the vector to bite this and pick up the next “dose”.
50% mortality. Easily treatable with antibiotics if spotted.
Which species causes sandfly fever? What type of pathogen is this caused by? Where does this occur? How many days following an infected meal can a female sandfly become infective? What are the symptoms?
- Phlebotamus papatasi
- A virus
- Africa, Middle East, India
- 6-10 (and eggs can contain virus/ vertical transmission)
- Fever, headaches and sometimes encephalitis.
How many countries are endemic for Leishmania and how many cases are there?
88 countries
~2 million
Where is the majority of VL located?
India Sudan Bangladesh Nepal Brazil
Where is the majority of CL located?
Afghanistan Iran Saudi Arabia Syria Peru Brazil
Which is the species predominantly responsible for VL?
Donnovani
Which is the species predominantly responsible for urban CL?
Tropica
Which is the main vector for L donnovani?
Phlebotomus argentipes
What are the main L species responsible for zoonotic leishmania?
L major and L aetheopica
The fat sand rat acts as a reservoir for which species? And which sandfly infects it?
L major
P. papatasi
How may epidemics of leishmania be caused?
Bringing in naive individuals into endemic areas (human migration or sandfly migration into naive populations).
What is the pathology of leishmania in sylvatic cycles?
Usually asymptomatic. Except in dogs :(((
How does sandfly control influence disease transmission?
A decrease in sandfly population strongly correlates with a decrease in disease incidence.
Which factors affect the control of sandfly populations?
- Whether or not there are zoonotic reservoirs
- Scattered or concentrated breeding sites?
- If the non-domestic transmission is significant? (e.g. mainly indoors or mainly outdoors?)
- If there is insecticide resistance
- If endemic zones are widespread or scattered
Which strategies may be effective to control anthroponotic leishmania?
- IRS and impregnated bednets
- Understanding where sandflies bite and rest
Which strategies may be effective to control zoonotic leishmania?
- IRS/ITN may also be effective here (to control infection acquisition)
- Insecticide-treated dog collars
- Killing reservoir host/ destroying rodent breeding sites.
How have sandflies adapted their behaviour based on human habits and how can understanding their behaviour inform us?
Sandflies accumulate outside during meal times and come in coinciding with our sleeping patterns.
Can inform our behaviour- we can change our timing of eating and going to bed to avoid sandfly activity.
What factor infuences the effectiveness of insecticide treated dog collars?
Whether or not non-domestic dogs/canids are important in transmission e.g. a larger non-domestic reservoir decreases the effectiveness of this technique.
What are endectocides? What are the issues with this?
Orally administered insecticides which give their effects through the animal’s follicles and skin.
Concerns over milk quality in dairy animals etc.
What is a possible reason that insecticide resistance is rarely seen/ is not a problem in sandflies?
Could be due to their slow growth rates which means that there is less time for reflection of benefits against the insecticides in the DNA.
