PARASITOLOGY - Ectoparasites Flashcards
Which class of ectoparasites incorporates flies?
Insecta
What is the main order of flies that is of veterinary importance?
Diptera
What is ‘fly worry’?
Animals become distressed by the presence of flies swarming around their heads and eyes, causing them to eat less leading to weight and economic loss
What are the three main species of non-biting flies that are of veterinary importance?
Musca domestica (house fly)
Musca autumnalis (face fly)
Hydrotaea irritans (head fly)
What is the main distinguishing feature of Musca domestica (house fly)?
Four longitudinal lines along the thorax
How are the legs of non-biting flies adapted for latching onto surfaces?
Non-biting flies have tarsal claws and pulvilli which allow them to latch onto surfaces
How are the mouthparts of non-biting flies adapted for feeding?
Non-biting flies have sponge-like suction pads that allow for the absorption of liquid food as well as prestomal teeth which act as a rasping device to extend existing wounds
What do Musca autumnalis (face flies) feed on?
Facial secretions such as saliva, tears and mucous as well as open wounds
What do Hydrotaea irritans (head flies) feed on?
Hydrotaea irritans (head flies) congregate around the heads of livestock causing them to and scratch, rub and bite leading to open wounds which the flies will feed on and extend
Give an example of a disease where Musca flies act as a vector
Summer sores
Which nematode causes summer sores?
Habronema nematodes
Describe the lifecycle of Habronema nematodes which cause summer sores in horses
- Horse expels Habronema eggs in their faeces
- Musca flies lay eggs in the faeces
- Musca larvae ingest the Habronema eggs within the faeces
- Habronema larvae develop within the Musca larvae
- L3 Habronema larvae migrate to the mouthpieces of the Musca fly and the L3 larvae are deposited on the horse when the Musca fly is feeding on facial secretions
- L3 are ingested by the horse and migrate to the stomach where they develop into adults and lay their eggs –>
What is the term used to describe the synchronised development between the Habronema and Musca larvae?
Transstadial transmission
What happens to horses if the Habronema L3 larvae are not ingested and instead remain cutaneously deposited?
If the L3 larvae are cutaneously deposited inside an existing wound, this can cause a hypersensitivity reaction causing lesions known as ‘summer sores’
What are two species of biting fly that are of veterinary importance?
Culicoides (midges)
Melophagus ovinus (sheep ked)
(T/F) Male culicoides (midges) feed on blood meals but the females do not
FALSE. Female culicoides (midges) feed on blood meals as their require the protein for egg development
What is a common disease seen in horses that is caused by culicoides (midges)?
Sweet itch
During which months of the year is sweet itch most prevalent?
Sweet itch is a seasonal disease most common between April to September
Which nematode is transmitted by culicoides (midges) as a vector?
Onchocerca cervicalis
Describe the lifecycle of Onchocerca cervicalis seen in horses
- Microfilaria are ingested by culicoides during a blood meal
- Microfilaria develop into L3 larvae within the culicoides
- Culicoides deposit the L3 larvae within the host during another blood meal
- L3 larvae migrate to the nuchal ligament of the horse where they develop into adults and produce more microfilaria
- Microfilaria migrate to the skin and eyes of the horse where they can cause dermatitis –>
Name a virus that is transmitted by culicoides (midges)
Schmallenburg virus (SBV)
How does the Schmallenburg virus (SBV) affect adult animals compared to pregnant animals?
Adults animals exhibit transient clinical signs however trans-placental transmission can cause abortion or severe congenital malformations of the brain, skull and spinal cord
Why are culicoides (midges) so challenging to control?
Culicoides (midges) have an extensive breeding habitat
Which three methods can be used to control culicoides (midges)?
Midge eater machines
Insecticides/screens
House animals during the culicoides most active period
Identify this ectoparasite
Melophagus ovinus (sheep ked)
Hairy, wingless, tarsal claws, robust legs
How are Melophagus ovinus (sheep ked) spread?
Melophagus ovinus are spread via direct contact
Melophagus ovinus (sheep ked) females are viviparous. What does this mean?
Melophagus ovinus (sheep ked) females give birth to live larvae
How often do Melophagus ovinus (sheep ked) females give birth to live larvae
Every 10-12 days
How do Melophagus ovinus (sheep ked) decrease the value of sheep wool?
When Melophagus ovinus (sheep ked) feed on blood meals, their bite causes intense pruritus (itching) causing the host to rub, scratch and bite which damages the wool
What can occur due to heavy Melophagus ovinus (sheep ked) infections?
Loss of body condition
Anaemia
Which two methods can be used to control Melophagus ovinus (sheep ked)?
Shearing
Insecticides
What is myiasis?
Myiasis is the invasion of a living vertebrate animal by fly larvae
What is obligate myiasis?
Obligate myiasis is when the myiasis is an essential part of their lifecycle
What is facultative myiasis?
Facultative myiasis is the exploitation of living tissue by larvae but it is not an essential part of their lifecycle
What are the six possible consequences of myiasis?
Severe tissue damage
Ulceration
Loss of tissue function
Putrid discharge
Secondary infection
Death
Give an example of a fly that causes obligate myiasis
Hypoderma (warble flies)
What are the two main species of Hypoderma (warble flies) that affect cattle?
Hypoderma bovis
Hypoderma lineatum
(T/F) Hypoderma (warble flies) have been eliminated in the UK
TRUE. However imported cattle still have a risk of carrying Hypoderma (warble flies)
Describe the lifecycle of Hypoderma (warble flies)
- Females lay eggs on the hair of the host
- Eggs hatch and L1 larvae penetrate the host skin via hair follicles
- L1 migrate to the spinal canal or oesophageal wall via connective tissue or nerve pathways
- L1 larvae then migrate to the sub-dermal tissue of the back of the host to complete development
- As the larvae develop, they pierce the skin of the host to allow for respiration
- L3 larvae erupt via the skin opening and land on the ground where they will pupate
- Adult Hypoderma emerge from the pupae –>
H. bovis migrate to spinal cord and H. linetum migrate to oesophagus
What is ‘butchers jelly’?
As the Hypoderma L1 larvae migrate through the tissue, they secrete digestive enzymes and macerate the tissue with oral hooks, creating gelatinous tracks known as ‘butchers jelly’
What are ‘warbles’?
‘Warbles’ are lumps on the skin caused by the L2 and L3 Hypoderma larvae
How do Hypoderma (warble flies) cause economic loss?
Fly worry
‘Butchers jelly’ decreases meat value
Hide perforation decreases leather value
(T/F) Hypoderma (warble fly) infestation is a notifiable disease
TRUE.
Give an example of flies that cause facultative myiasis
Blow flies
What are the three species of blow fly that are of veterinary importance in the UK?
Lucilia (green bottle)
Calliphora (blue bottle)
Phormia (black bottle)
What are primary blow flies?
Primary blow flies can initiate myiasis on living animals without the need for existing tissue damage
What are secondary blow flies?
Secondary blow flues cannot initiate myiasis and instead need existing tissue damage or existing fly strike
Which species’ of blow fly are primary flies?
Lucilia (green bottle)
Phormia (black bottle)
Which species of blow fly is a secondary fly?
Calliphora (blue bottle)
What kind of tissue are blow flies attracted to to initiate myiasis?
Moist tissue
Faecal contaminated tissue
Necrotic tissue
Which three species are most commonly associated with myiasis?
Sheep
Poultry
Rabbits