Week 8

Question 1

House Flies

Answer 1

Muscidae

Question 2

Common housefly

Answer 2

Musca domestica (Family Muscidae)

Question 3

Introduction

Answer 3

• can be vectors of helminths, faecal bacteria, protozoans
  and viruses, resulting in the spread of enteric diseases (e.g. dysenteries
  and typhoid)
• 70 species of flies

Question 4

Important Species

Answer 4

• The bazaar fly (Musca sorbens)
• The notoriously troublesome bush fly (M. vetustissima)
• The face fly (M. autumnalis)

Question 5

Morphologies

Answer 5

• Medium-sized non-metallic flies about 6–9 mm long
• four rather broad black longitudinal stripes
• The mouth parts (proboscis) are specially adapted for
  sucking up fluid or semifluid foods.
• fine channels called
  pseudotracheae through which fluids are sucked up
• pulvilli, which are supplied with glandular hairs.
• sticky hairs enable the fly to adhere to very smooth surfaces

Question 6

Life Cycle

Answer 6

• feed on food of humans, rotting vegetables, carcasses,
  excreta and vomit – in fact almost any organic material
• Female Musca domestica lay their eggs on decomposing materials
• The eggs are creamy-white, 1–1.2 mm long, and distinctly
  concave dorsally
• Egg hatch after only 10–16 hours, but this period is longer in
  cool weather
• Larvae, known as maggots, have a small head followed by an 11-
  segmented cylindrical body
• The puparial stage lasts about 3–5days in warm weather but 7–14 days during cooler periods

Question 7

Medical Importance

Answer 7

can transmit viruses of:
1) polio
2) Coxsackie and infectious
hepatitis
3) rickettsiae of Q fever (Coxiella burnetii)
4) bacteria such as:
- anthrax
- Campylobacter
- cholera (Vibrio cholerae)
- Shigella and Salmonella
- Escherichia coli
- Staphylococcus aureus
- spirochaetes of yaws (Treponemapertenue)
- protozoans including Entamoeba,
Cryptosporidium and Giardia
5) Helminths

Question 8

Control Measures

Answer 8

• Physical and mechanical control
• Environmental sanitation
• Insecticidal control

Question 9

Flies and Myiasis

Answer 9

• Flies are dirty insects with two wings (Diptera)
• Myiasis is defined as an infestation by fly larvae (maggots)

Question 10

Life Cycle (Habitat)

Answer 10

• Obligatory
• Facultative
• Accidental or Pseudomyiasis

Question 10

Life Cycle (Habitat)

Answer 10

• Obligatory
• Facultative
• Accidental or Pseudomyiasis

Question 11

Medical Importance

Answer 11

• Biological
• Sites of infection

Question 12

Types of Myiasis based on sites of infestation:

Answer 12

A. Cutaneous
B. Intestinal
C. Urogenital
D. Ophthalmic, Aural, Nasal and Oral Myiasis

Question 13

Cutaneous Myiasis

Answer 13

Fly eggs hatch on
injured wounds (traumatic myiasis), burn wounds and ulcers, especially if these wounds are exposed.

Question 14

Intestinal Myiasis

Answer 14

This is also called pseudomyiasis. It occurs as a result of accidentally swallowing maggots in food
stuff like fruits (fruit flies) and cheese (cheese skipper. Occasionally, this condition is accompanied by intestinal symptoms like abdominal pain and diarrhea.

Question 15

Urogenital Myiasis

Answer 15

Eggs are laid under the prepuce or vaginal folds and will hatch into maggots. Maggots may occasionally
be found in the urine or vagina

Question 16

Ophthalmic, Aural, Nasal, Oral Myiasis

Answer 16

Any exposed organ such eyes, ears or nose can be infested.

Question 16

Pathogenesis

Answer 16

• deposit their eggs or larvae in the wounds or body orifices (ear, nose) when there is discharge (bloody/serous).

-The larvae penetrate in the tissue

• The wound develops an offensive odor and a foul-smelling liquid oozes out

Question 17

Treatment for Myiasis

Answer 17

• With ethanol or chloroform mixed with vegetable oil.
• Ocular myiasis, and delicate surgery may be needed to remove the larvae.

-covering the hole in the swelling with medicinal liquid paraffin.

• Maggot Debridement Therapy