9. Muscoid flies. Myasis

Question 1

Muscoid flies. General info + species

Answer 1

• Muscidae family
• some are associated with man (synathropic), usually diurnal
• some occur inside the stables (endophilic), some on the pastures (exophilic)
• development in decaying plant or animal tissues
• Musca domestica - housefly
• Fannia canicularis - lesser housefly
• Stomoxys calcitrans - stable fly
• Musca autumnalis - face fly
• Haemotobia irritans - horn fly

Question 2

What muscoid flies are haematophagous?

Answer 2

Stomoxys calcitrans and Haemotobia irritans

Stomoxys calcitrans attacks mostly lower parts of the host and Haemotobia irritans usually around horns, back, sides

Question 3

How to distinguish Musca domestica and Musca autumnalis?

Answer 3

Musca domestica has brownish pupa and Musca autumnalis — white

Question 4

What species of muscoid flies has 7 spots on the abdomen?

Answer 4

Stomoxys calcitrans

Question 5

Myasis. Definition and groups of insects that cause it. Morphology

Answer 5

• infection of living animals with larvae of dipterian flies
• blowflies, fleshflies, warble flies, botflies, sheep nasal botfly

Question 6

Blowflies

Answer 6

• Lucilia and Cochliomyia spp
• up to 1 cm, metallic blue, green or bronze sheen of the body
• pupation in the ground
• Lucilia sericata - mainly in Europe, also in southern hemisphere - facultative
• Lucilia cuprina - Australia, New Zealand, South-Africa - facultative
• Cochliomyia hominivorax - Latin and South-America - obligatory

Question 7

Fleshflies

Answer 7

• Sarcophagidae family, Wohlfahrtia spp
• 12-15 mm, body is grey-black, abdomen with spots
• obligatory
• Wohlfahrtia magnifica
• larvae dig deep into the host tissue -> damage by oral hooks, spines, proteolytic enzymes, manifesting as liquefaction, necrosis, haemorrhage. Wound, odour attracts further flies. Death may follow due to septicaemia. Anorexia, production loss, if recovery -> fibrosis, deformity

Question 8

Warble flies. Hypodermatinae subfamily. Species, morphology

Answer 8

• adults are short-lived
• larvae undergo tissue migration
• Hypoderma bovis, Hypoderma lineatum
• 1,5 cm, bee-like, no functional mouthparts
• larvae: 2-3 cm, stout, whitish

Question 9

Warble flies. Development

Answer 9

1. Females attach the eggs to hairs (singly - bovis, in row - lineatum)
2. 3 larval instars: after hatching the first penetrates the skin and migrates to the spinal canal (bovis) or the diaphragm, oesophageal (lineatum)
3. First moult epidurally (bovis) or submucosally (lineatum)
4. Second moult in the subcutis of the back, where they remain for 3 months
5. 3d stage ;arcade makes a cutaneous perforation through which they breathe
6. Finishing their development lasting altogether 6-9 months mature larvae emerge and fall to the ground to pupate

Question 10

Warble flies. Clinical signs and pathology

Answer 10

• Hypoderma bovis - panicking, paraplegia
• Hypoderma lineatum - faulty regurgitation
• anaphylaxis, production losses
• greenish, gelatinous tissue in the muscles (“butcher’s jelly”)
• hide damage (holes)

Question 11

Botflies. Species, morphology

Answer 11

• subfamily Gasterophilinae: Gasterophilus intestinalis, G. nasalis, G. haemorrhoidalis, G. pecorum
• adults are short-lived, non-feeding
• larvae are found in GIT of equids
• adults 1-2 cm, resemble honey bees, reduced mouthparts
• females’ ovipositor curved under the abdomen
• 3d stage larva ~2 cm, two big oral hooks

Question 12

Botflies. Development

Answer 12

1. Eggs laid on hair (1 - shoulders, 2,3 - around lips) or on the pasture (4)
2. After hatching 1st larval instars crawls into the mouth or are licked off
3. They penetrate the mucosa/tongue, moult and migrate to the stomach
4. After attachment (1 - cardia, 2 - pylorus, duodenum) they moult
5. While developing for 10-12 months, larvae feed on tissue exudates
6. Mature larvae detach, pass in the feces (3 - reattach in the rectum) and pupate in the soil

Question 13

Botflies. Clinical signs, pathology

Answer 13

• clinical signs usually absent (occasionally toxic anaemia, rectal irritation, digestive problems due to stenosis)
• patho: stomatitis, ulcers (tongue, stomach)

Question 14

Sheep nasal botfly. Species, morphology

Answer 14

• Oestrus ovis
• adults are short-lived
• larvae parasitise the nasal and frontal cavities of small ruminants
• adults: 1 cm, having brown hair, big head with vestigial (degenerate, rudimentary) mouthparts and widely separated eyes, small black spots (especially on the thorax)
• 3d larval instars up to 3 cm

Question 15

Sheep nasal botfly. Development

Answer 15

• females are viviparous (give birth to larvae, do not lay eggs), first stage larvae are laid at the nostrils
• larvae migrate through the nasal passages (first moult) to the frontal sinuses (second moult) feeding on mucus, go back to the nostrils when mature
• after remaining for 9-10 months they are expelled by sneezing, pupate in the soil

Question 16

Sheep nasal botfly, Clinical signs, pathology

Answer 16

• nasal discharge, sneezing, rubbing the nose
• circling and in coordination (‘false gid’)
• purulent ethmoiditis (cerebral involvement) when larvae die in the sinuses
• pharyngitis, secondary bacterial invasion