Module 9b Black, Tsetse Flies and Myiasis

Question 1

black flies taxonomy and characteristics

Answer 1

Family Simuliidae
require flowing water (lotic)
3rd biggest arthropod vectors of disease
swarming nature

Question 2

black fly anatomy

Answer 2

suborder Nematocera (long antennae)
well developed compound eyes (male's touch)
telmophage but don't penetrate very deep
only females bite
short mouthparts

Question 3

black fly larva

Answer 3

larvae have distant head with pair of labral fans for filter feeding when attached to rocks in moving water

Question 4

black fly life cycle

Answer 4

adults live less than a month, but must mate, sugar feed, locate a host, blood feed, and lay eggs
larval stage is the longest

Question 5

behavior of adult black flies

Answer 5

notorious human biters
females bite only exposed skin
blood-engorged females must rest until blood meal is digested
anautogenous (need blood meal)

Question 6

Onchoceriasis

Answer 6

“River Blindness”

parasite: Onchocerca volvulus (nematode)
vector: Simulium spp (black fly)

Question 7

onchocera transmission cycle

Answer 7

1. female black fly acquires microfilaria
2. it penetrates gut of fly - thorax - fly’s mouthparts
3. feeds again and deposits microfilaria under host’s skin
4. adults form nodules where mating occurs
5. microfilaria migrate into skin (eyes, lymph nodes, groin)

Question 8

onchocerciasis control programme (OCP)

Answer 8

WHO initiated control program in 1975

• larviciding
• breeding areas (river) dosed weekly w/ insecticide
• drug to kill the microfilariae (ivermectin)
• maintaining vectors at low number

Question 9

tsetse fly taxonomy and characteristics

Answer 9

Suborder Brachyacera
Family Glossinidae
Genus Glossina (tongue fly)
obligate hematophagous, solenophage
found mostly in tropical Africa

Question 10

tsetse anatomy

Answer 10

small
short antennae
long mouthparts that are held in front
hatchet cell in wing, help on top of each other
single larvae that immediately pupates (pupivarious)

Question 11

african sleeping sickness or african trypanosomiasis

Answer 11

parasite: trypanosoma bruci
(t. b. gambiense: west african tryp.)
(t. b. rhodesiense: east african tryp.)
vector: Glossina spp (tsetse fly)

Question 12

african sleeping sickness transmission cycle

Answer 12

1. tsetse fly acquires parasite from infected blood meal
2. develops from bloodstream - midgut - salivary glands
3. also transmitted from mother to child, lab accidents, or blood transfusions
4. deposited in new host thru saliva

Question 13

tsetse control and prevention

Answer 13

IPM: treatment of humans and animals, insecticides, removal of breeding sites, sterile insect technique*

Question 14

myiasis

Answer 14

invasion of living vertebrate animal by fly larva by:

1. accidental - contaminated food
2. facultative - larva is parasitic (wound invasion)
3. obligatory - larva require host for development (i.e. maggots)

Question 15

families of importance in myaisis

Answer 15

1. family Calliphoridae: blow flies and screwworms

2. family Oestridae: bot flies (human bot fly: Dermatobia hominis)

Question 16

screwworm

Answer 16

serious livestock pest
females deposit 200-300 eggs
eradicated in US in 1960s using sterile male technique

Question 17

bot fly transmission cycle

Answer 17

egg deposited on skin by the fly itself or by hijacking a mosquito
bot fly never comes into contact with us
human bot fly: dermatobia hominis

Question 18

blow flies

Answer 18

used in maggot therapy
bucilia sericata (green bottle blow fly)
-used during wars
-eggs treated w/ antiseptic before use
-no need for anesthesia

Question 19

benefits of maggot therapy

Answer 19

1. removes necrotic skin
2. promotes wound healing
3. produces habitat less conductive for bacterial growth
4. healing is very rapid w/ less scarring