Tsetse flies and trypanosomiasis

Question 1

How many species of Glossina are there? What are they vectors for?

Answer 1

30-31.

Trypanosomiasis.

Question 2

What are the two types of HAT?

Answer 2

Rhodesian and gambian.

Question 3

Describe the life strategy of tsetse flies?

Answer 3

Are K strategists meaning they invest lost in offspring and have few.

Question 4

Describe the unusual feeding of tsetses, what is the advantage of this?

Answer 4

Both males and females feed on blood. This is an advantage as they are vulnerable to blocking feeding interventions.

Question 5

Where do we find HAT? Compare this to the distribution of ATT.

Answer 5

In the tsetse belt which is 11 million squared kilometers.

HAT is not as widespread and more focal whereas AAT is more widespread.

Question 6

What is the ideal temperature for a tsetse fly?

Answer 6

25 degrees, like specific conditions.

Question 7

What does AAT mainly affect and why is this a problem?

Answer 7

Mainly affects cows. Is a huge economic burden.

Doesnt really affect wild animals unless they are stressed.

Question 8

What are the morphological features of the adult tsetse?

Answer 8

• 6 legs
• Head, thorax, abdomen
• 2 pairs of wings (front and halteres).
• Holes for gas exchange
• Proboscis sticks STRAIGHT FORWARD.
• Arista (secondary hairs emerging from primary hairs) is a CLASSIC TSETSE FEATURE.
• Hatchet cell on wings.
• Wings folded across each other “scissor wings”.

Question 9

What are tsetse attracted to for feeding?

Answer 9

(Don’t go looking for people, are more opportunistic feeders).
-Look for large moving objects and are attracted to blue in the long range and blue in the short range.

Question 10

What are the three types of tsetse?

Answer 10

• Fusca
• Palpalis
• Mortisans

Question 11

What is the habitat for fusca tsetse flies and what do they transmit?

Answer 11

Dense forest. Vectors for AAT.

Question 12

What is the habitat for palpalis tsetse flies and what do they transmit?

Answer 12

Wetter vegetation such as banks of rivers and lakes. Gambian HAT.

Question 13

What is the habitat for mortisans tsetse flies and what do they transmit?

Answer 13

Savannah. Transmit Rhodesian HAT despite preferring to bite savannah animals and game.

Question 14

Describe the differences in tarsae in palpalis and mortisans.

Answer 14

Palpalis: dark tarsae.
Mortisans: only end of tarsae are dark.

Question 15

Describe the reproductive process of the tsetse fly. (From conception to birth).

Answer 15

• Mates only once. Males use claspers.
• Females store sperm in spermatheca which is then used to fertilise one egg in the uterus.
• Larvae develops inside female using milk as nourishment which comes from milk glands inside the female.
• Singular third instar larvae is larvaeposited.
• This takes around 50 days

Question 16

What are polypneustic lobes and when in development are they found?

Answer 16

Are respiratory apparatus only found during the larval stage.

Question 17

What is the name of the inflated “balloon” that the fly uses to emerge from the pupae?

Answer 17

Ptilinum.

Question 18

For how long do tsetse flies rest vs search for food?

Answer 18

Rest most of the day and only search for food for one hour a day.

Question 19

What are the feeding cues for tsetse flies?

Answer 19

Carbon dioxide and olfactory cues. Large moving objects and black and blue colouration.

Question 20

Describe ways in which vectors were controlled for rHAT? Why did they use these strategies and why could it not be continued?

Answer 20

• Cut down vegetation
• Killed all the game

Not sustainable. Rest on vegetation and feed on game.

Question 21

What is eradication vs elimination?

Answer 21

Eradication: complete, permanent reduction to 0 cases with no need for control measures.

Elimination: reduction of disease close to zero or at low levels with control measures to maintain this low level.

Question 22

Describe current vector management for tsetse flies.

Answer 22

• Traps (3D, using attractive colouration).
• Impregnated nets (with insecticide).
• Aeriel spraying for epidemics and for hard to reach terrain.
• Sterile insect technique (gamma irradiated males).
• Insecticide-treated cattle
• Tiny traps (good for palpalis).

Question 23

What is a semiochemical? Give examples.

Answer 23

A signalling volatile such as a host odour constituent. Examples include: co2, acetone, butanone, p cresol, 1-octan-3-ol, 4,3-n-propylphenol.

Question 24

Which stage do we target for vector management? Why?

Answer 24

Adult stage because juveniles are inaccessible due to larvae burrowing into the ground.

Question 25

What is the drawback to using gamma-irradiated male technique for vector management?

Answer 25

Need 100 males per kilometer per week to be successful so may only be useful when a point is reached where we are close to eradication.
Need the facilities and infrastructure to breed and irradiate this many flies.
Furthermore, this needs to be done for each individual species as species do not interbreed.