Oestrus ovis (1) Flashcards
What is the common name?
Sheep Nasal Fly
Warble fly of sheep, goats, and llamas
What are the hosts?
Sheep and goats
Llamas
Possibly humans
Describe adults
Large (up to 1.2 cm)
Grey
Short lived
Describe mature larvae
“Nasal bots”
In nasal passages - up to 3 cm long
Long
Yellowish white
Tapering anteriorly
Prominent stripe posteriorly
Each segment has dark transverse band dorsally
Explain life cycle
Female spurts a jet of liquid containing 25 first stage larvae to nostrils of sheep
- Female delivers during flight
Larvae migrate into nasal cavity
Developing bots feed on mucus, cause irritation
In frontal sinuses develop to 2nd and 3rd instars
Remain in nostrils for 2 weeks in summer to 9 months during colder part of year
- Overwintering stage
Reach 3rd instar stage (3 weeks-several months) before sneezed out to pupate (4-7 weeks)
Adults emerge
- Females survive for 2 weeks - deposits 500 larvae
What is the site of infestation?
Nasal passages and sinuses
Describe the Pathogenesis
Larvae cause irritation and excessive secretion by mucus membranes
- Oral hooks and ventral spines
Infested sheep - copious nasal discharge, sneeze frequently
Secondary bacterial infection common
Animals avoid attacks by pressing noses against ground/in between sheep
Time spent feeding reduced
Sheep panic, stamp feet
Attacks interrupt feeding - animals may lose weight
To avoid attacks animals expend much energy and lose condition and weight
Aberrant migration through soft palette may enter brain cavity
Humans can become infected in the eye or lip, but does not develop further
Copious nasal discharge (snotty nose)
How do you diagnose?
Fly identification
How do you treat and prevent?
MCLs effective against fly
Treatment at beginning of summer - kill newly acquired larvae
- Second at midwinter to kill overwintering larvae
What is important about Oestrus ovis?
It is ZOONOTIC
