Blackflies, midges and sandflies Flashcards
Latin for blackflies
Simulidae
Describe the identifying features of blackflies
Small, black, humpbacked biting flies
1,4 - 6mm long
Large, compound eyes
Brush-like mouth part acting as a filter
What is the taxonomy of simulidae based on
Polytene chromosomes (lack of molecular data)
What are blackflies also called?
Buffalo gnat
Describe the life cycle of black flies
- Eggs
- 150-600 eggs dropped from air/vegetation/substrates into fast flowing water
- hatch after 2-30 days (survive 2-8 months dependent on species and water temperature) - Larvae
- growth temperature dependent (cold = slower, diapause)
- develop in flowing water
- 4-9 larval stages usually 7
- takes 1-6 months
- larvae anchor themselves by spinning small, silken pad with mouth parts and inserting row of hooks from abdomen into the silk pad - Pupae
- housed with air bubble which bursts when adult emerges
- delicate silk cocoon in some species
- 4-7 days - Adult
- males and females feed on nectar and mate
- males die
- females feed on blood and develop an egg mass
What does severity of infection from black flies depend on?
Number of bites
Which disease do blackflies transmit?
Onchocerciasis
Which organism causes onchocerciasis and what is it?
Onchocerca volvulus
Filarial nematode
What is onchocerciasis also called and what does it cause?
African river blindness
Acute + longstanding infection
What other condition can onchocerciasis cause and what are its features?
Blackfly fever (North America)
Relatively mild
- headache
- nausea
- fever
- swollen neck lymph nodes
Describe the life cycle of onchocerca volvulus
Blackfly stages:
1. Blackfly takes blood meal (L3 larvae enter bite wound)
Human stages :
2. Subcutaneous tissues
3. Adults in subcutaneous nodule
4. Adults produce unsheathed microfilariae that are typically found in skin and lymphatics of connective tissue but also occasionally peripheral blood, urine, sputum
Blackfly stages:
5. Blackfly takes blood meal and ingests microfilariae
6. Microfilariae penetrate blackfly’s midgut and migrate to thoracic muscles
7. L1 larvae
8. L3 larvae
9. Migrate to head and blackfly’s proboscis
How long does the blackfly stage last?
1 week
Discuss blackfly control
Difficult
Usually aimed at larval stages
Involves aerial insecticides
Target breeding sites (BTI ingestion via water)
Best defense = repellants (DEET, permithrin treated clothing)
Ivermectin treatment to kill larvae
Doxycycline to kill adult worms
What is the latin for biting midges?
Coulicoides
How do you identify biting midges?
Tiny 1-3mm
Yellow-brown (red when filled with blood)
Spotted wings
Stout-legged flies
Mouth parts consist of fleshy sheath containing 4 cutting blades which cause skin lacerations
What is the latin for the biting midges family?
Ceratopogonidae
Discuss the life cycle of biting midges
2-8 weeks total
1. Eggs
- laid in damp breeding sites
- require water to develop
- require blood to mature
- number depends on species and blood meal size
2. Pupae 2-3 days
3. Adults undergo complete metomorphosis
What does holometabolous mean?
Eggs -> larvae -> pupae -> adults
Which organism do biting midges transmit?
Mansonella perstans (filarial worm)
What are the clinical features of mansonella perstans infection?
Dermatitis
Skin lesions
Why are biting midges important for vets?
Blue tongue (sheep, cattle)
African horse sickness
Discuss the life cycle of mansonella perstans
Midge stages:
1. Midge takes blood meal (L3 larvae enter bite wound)
Human stages:
2. Adults in peritoneal/pleural cavity (sometimes pericardium)
3. Adults produce unsheathed microfilariae that reach bloodstream
Midge stages:
4. Midge takes blood meal (ingests microfilariae)
5. Microfilariae penetrate midge’s midgut and migrate to thoracic muscles
6. L1 larvae
7. L3 larvae
8. Migrate to head and midge’s proboscis
Difference between male and female midges?
Females larger
What are the 3 types of mansonella?
Perstans
Streptocerca
Ozzardi
Discuss biting midge control
Removal trapping using CO2 attractant to insecticide
Repellants (DEET)
Window screens
What is the latin for sandflies?
Phlebotomus
Discuss the identification of sandflies
small
Large black eyes that are continuous with 5th and 6th antennae
Long, slender leggs
Piercing mouthparts for taking blood in FEMALES only
Clear, unmarked, hairy wings
Discuss sandfly flight
Weak fliers
Tend to move via weak hopping flight
Discuss sandfly lifecycle
- Eggs
- hatch after 4-20 days (longer if cold) - Larvae
- undergo 4 instars - Pupae
- 6-13 days - Adult sandflies
What is special about sandfly anatomy?
- Pedicle of male’s antennae contains Johnston’s organ for hearing
- Non-segmented abdomen extends past head
What disease do sandflies transmit?
Leishmaniasis and arboviruses
Discuss the life cycle of leishmaniasis
Mammal stage:
1. Metacyclic promastigotes transferred during feeding
2. Actively invade macrophages, granulocytes or are phagocytosed
3. Promastigotes transform into amastigotes and multiply by simple division
3. Amastigotes leave infected cells
Female sandly stage”
4. Amastigotes transferred during feeding
5. Release in the midgut
6. Transform into procyclic promastigotes
7. Simple division into metacyclic promastigotes
8. Promastigotes migrate to pharyngeal valve and transferred during feeding
Discuss control of sandflies
Residual insecticides (organophosphates, carbamates, pyrethroids)
Breeding/resting site elimination (fill cracks, destroy termite mounds)
Reservoir animal control (dispose of decomposing animal flesh)
What is the difference between midges and sandflies?
Midges
- small, 2 winged fly
- forms swarms
- breeds in moist environments
- belong to several families of non-mosquito
- Nematoceran Diptera
- do not bite
- mansonella perstans
Sandfly
- small, hairy fly
- tropical and subtropical
- Psychodidae subfamily of Phlebotomina
- blood-sucking
- leishmaniasis and poppataci fever
What is Poppataci fever caused by?
Phlebovirus
