Myiasis

Question 1

What is the name of greenbottles? What do they do?

Answer 1

Lucilia seratica. Lay maggots into dogs, humans. Affects the poorest people.

Question 2

What is the old world screw worm?

Answer 2

Chrysoma bezziana.

Question 3

What is the new world screw worm?

Answer 3

Cochliomyia hominovorax

Question 4

How could the eradication of screwworms occur? (I.e. how has this already been achieved in Florida Keys)?

Answer 4

• Animal inspection on highways
• Treatment points for animals
• 2 million sterile flies released twice a week

Question 5

What are the three types of myiasis? (In terms of what they feed on)?

Answer 5

• Accidental: ingestion of eggs or larvae with food
• Facultative: by carrion or live hosts
• Obligate- only on live hosts.

Question 6

Where are the three main locations of pathology in myiasis?

Answer 6

The intestinal tract, urogenital tract, respiratory tract

Question 7

What are the three main families of myiasis causing fies? Are they obligate or facultative?

Answer 7

• Oestridae (botflies)- obligate only
• Calliphoridae (blowflies)- obligate or facultative
• Sarcophagidae (flesh flies)-obligate or facultative

Question 8

What is interesting/ unique about oestridae?

Answer 8

Their alimentary canal is vestigial- their energy, therefore, goes into egg production rather than feeding.

Question 9

What are the infestation sites of oestridae, calliphoridae and sarcophagidae?

Answer 9

Oestridae- skin, respiratory tract (i.e. nasal passages)

Calliphoridae and sarcophagidae- mainly cutaneous

Question 10

What is the lifecycle of myiasis flies?

Answer 10

Egg–> 3 larval instars –> third instar shrinks and adult pupates –> mating following pupation.

Question 11

Which characteristics do we look at to identify the different species of myiasis flies? (Larvae)

Answer 11

• Head end (notches of mouthparts)
• Posterior spiracles (3 in L3 and 2 in L2)
• Spine bands
• Crop with food in

Question 12

Which characteristics do we look at to identify the different species of myiasis flies? (Adults) (How many segments of each part of the body are there?)

Answer 12

• One head segment duh
• 3 thoracic segments
• 8 abdominal segments

Question 13

As well as molecular tools being used for identification, how can landmark analysis separate lineages?

Answer 13

By looking at where veins intersect.

Question 14

Which oestridae is found in the UK and how does it infect sheep?

Answer 14

Oestris ovis. Squirts out larvae in flight into sheeps nostrils, they snort it out and they pupate in the soil.

Question 15

What is the camel nostril fly bot?

Answer 15

Cephalophora titilator.

Question 16

Why/ how can oestridae infect humans? How does human infection present?

Answer 16

As they cannot feed, they must find their host quickly and lay eggs, if they cannot find the primary host, they will simply find a secondary host.

Human infection is usually resolved fairly quickly and may present as mild conjunctivitis.

Question 17

Describe the lifecycle of hyperdermatinae (subfamily of oestridae).

Answer 17

Flies lay EGGS –> eggs attach to hairs of host –> larvae hatch and migrate through the animal –> warble formed in the dermis –> they feed and evacuate and fall out onto the ground –> they then pupate into an adult.

Question 18

Which Oestridae reside in the digestive tract? Why?

Answer 18

Gastrophilinae. For the warm temperature and constant food supply.

Question 19

Describe the lifecycle of gastrophilinae.

Answer 19

Eggs laid on hairs–> larvae get to the mouthparts (e.g. by licking) –> develop in gut –> pass out in faeces–>pupate in soil

Question 20

Which drug is used to treat all horses in the UK for gastrophilinae?

Answer 20

Avermectin.

Question 21

Cuterebra is a new world oestridae that likes dermal tissue. What is its lifecycle?

Answer 21

Drops onto the host –> penetrates skin –> subcutaneous migration –> forms a warble.

Question 22

How does dermatobia hominis indirectly infect humans? How are they removed?

Answer 22

Catches flies and lays their eggs on them (e.g. mosquitos, tabanids) eggs hatch when they detect warmth from the insect landing on a human. Eggs hatch and burrow into host- backwards pointing spines aid in retention.

Surgical removal or occlusion of the wound so the maggot crawls out to breathe.

Question 23

Where do sarcophagidae penetrate? What is an example of a sarcophagidae?

Answer 23

Are cutaneous but can penetrate further.

Wohlfahartia magnifica.

Question 24

What is cordylobia (i.e. what is its common name) and what does it preferably feed on? Where does it lay its eggs?

Answer 24

Is a tumbu fly. Is anthropophagic. Lays eggs on sites of urine contamination. They burrow into soil until animals lie on top.

Question 25

Give one example of an auchmeromyia (genus). What does it feed on?

Answer 25

Auchmeromyia senegalensis. Blood (10 blood meals in larval development). After each blood meal, the larvae drop off and continue development.

Question 26

Other than auchmeromyia, which other flies are sanguinivorous?

Answer 26

Calliphorias and muscias.

Question 27

What conditions does lucilia seratica require from the host for infection?

Answer 27

Needs a predisposing condition e.g. fleece contamination with faeces or urine. They feed on healthy tissue once everything else has run out.

Question 28

What are the three ways we can control myiasis flies?

Answer 28

• Control and eradication (sterile insect technique, insecticide spraying, odour attractants to catch and kill them)
• Avoidance (vaccines?, prophylactically treating animals)
• Treatment (removal of maggots, difficult due to spine bands).

Question 29

Why should we treat animals?

Answer 29

• Pain/ suffering
• Secondary infection
• Death