Mites Flashcards
What are the differences between insects and arachnids?
- Insects have 3 pairs of legs, arachnids have 4 (except larval stage of tick, has 3)
- Arachnids have hemimetabolic life cycles, lice have hemimetabolic, other insects have homometabolic
What is the scutum?
Hard shield or plate on dorsum of “hard” or Ixodid tick
What is the hypostome?
- Mouthpart of tick, used to anchor tick in position while feeding
- Also serves to form gutter for blood and saliva
How can mites and ticks be distinguished from one another?
Mites do not have hypostome or scutum
How can the presence of mites be confirmed?
- Hair pluck
- Skin scrape
- Coat brush
- Serological test
What are the 2 types of mites?
- Burrowing
- Surface
List the important species of burrowing mites
- Sarcoptes
- Trixacarus
- Notoedres
- Knemidocoptes
- Demodex
Describe the apperance of burrowing mites
- Rounder
- Short legs
Describe the appearance of Demodex
- Long, thin
- Short legs in one area near head (look a little like rings)
Describe the life cycle of mites
- Eggs laid by female
- Larvae hatch
- Become nymphal stage
- Develop into adults
Describe Sarcoptes scabei
- One species, find host-adapted strains in most mammals
- Highly contagious, zoonotic
- Entire life cycle on host
- Intense pruritus caused by hypersensitivity to mite faecal material
How is infestation with Sarcoptes scabei diagnosed?
Deep skin scraping in 12 or more affected areas
Describe Trixicarus caviae
- Guinea pigs
- Burrowing
- Intense pruritus, alopecia, dermaitis
- May show secondary infectionand stres
How is infestation with Trixicarus caviae diagnosed?
Examination of hair shafts or skin scrapings to identify mite
Describe Notoedres cati
- Mainly in cats
- Burrows into skin
- May produce pruritus, alopecia and dermatitis
- Especially on head and around ears
Describe Knemidocoptes
- Scaly face, scaly foot, tassel food in birds
- Highly contagious
- Inflammation and exudate that dries
- Appears similar to papilloma or pox virus
- Intense hypersensitivity reaction
Describe the appearance of infestation with Knemidocoptes
- Inflammation
- Exudate that dries
- Hyperkeratosis lameness, deformities
- Rock hard, crumbly lesions
- Pruritus, scratchin
Describe Demodex
- Highly specialised
- Lives in hair follicles and sebaceous glands
- Host specific
- Infest meibomian glands as commensals
- Disease mainly in dogs
Where does the life cycle of Demodex take place?
Entire life cycle in one sebaceous gland/hair follicle
Describe Demodex in dogs
- Very common
- Often underlying disease
- Often secondary to Staphylococcal pyoderma
- Localised or generalised
- Chronic and difficult to treat
Describe localised demodicosis
Commonly on face and forelegs of young animals
Describe generalised demodicosis
More severe, widespread from onset, often underlying disease
How is infestation with Demodex diagnosed?
Hair pluck and deep skin scrape
What are the important families of surface mites?
- Psoroptidae
- Cheyetiellidae
- Trombiculidae
- Dermanyssidae
- Macronyssidae
- Listrophoridae
What are the important genera of Psoroptidae?
- Psoroptes
- Chorioptes
- Otodectes
What is the important genera of Cheyletiellidae/
Cheyletiella
What is the important genera of Trombiculidae?
Trombicula
What is the important genera of Dermanyssidae?
Dermanyssus
What is the important genera of Macronyssidae?
Ornithonyssus
What are the important genera of Listrophoridae?
- Chirodiscoides
- Listrophorus
What are the only free living mites?
Trombicula - only parasitic in larval stages, jump on, bite, then off again
What is infestation by Sarcoptes scabei known as?
Mange
What is infestation by Psoroptes ovis known as?
Sheep scab
Name the important strains of Psoroptes and their host species
- P. ovis: sheep, cattle
- P. equi: horses
- P. cuniculi: rabbits
Describe Sheep Scab
- Psoroptes ovis
- Severe pruritus, hypersensitivity, self trauma
- Economically important
- Used to be notifiable, no longer the case
Describe infestation with Psoroptes
- Very irritant
- Causes rubbing and trauma
- Especially in winter
- Can be zoonotic
How is infestation with Psoroptes diagnosed?
Skin scrape (if very superficial can use acetone tape)
Describe infestation with Chorioptes
- Chorioptes bovis
- Mange in cattle and horses esp winter
- Irritant, rubbing but rare trauma (some alopecia where rubbing)
- Localised infestations and therefore lesions
- Causes loss of production
What are the main locations for Chorioptes infestation in horses and cattle?
- Horses: lower legs
- Cattle: tail and perineum
Describe Otodectes cynotis
- Ear mites in cats and dogs
- and other carnivores
- Can be zoonotic
- Severe irritations
- Can spread if untreated
Describe the clinical signs of infestation with Otodectes cynotis
- Often subclinical
- Head shaking
- Continual ear scratching
- Ear droop
- Pruritus variable
- Thick red crusts in external ears of hosts
- Characteristic black, crusty wax
How is infestation with Otodectes cynotis diagnosed?
Mites can be seen with otoscope, or microscopic examination of characteristic wax
Name the 3 parasitic species of Cheyletiella and give their host species
- C. yasurgi (dogs)
- C. blakei (cats)
- C. parasitivorax (rabbits)
Describe Cheyletiella
- Largely free living, often predatory
- 3 parasitic species
- Cause sclaing, dermatitis and pruritus (usually mild)
- Aka walking dandruff as move around debris
How is infestation with Cheyletiella diagnosed?
- Characterisic “walking dandruff)
- Diagnosed by acetone strip test
Name the main species of Trombicula
Trombicula autumnalis (chigger or harvest mites)
Describe Trombicula
- Free living, only parasitic in larval stages
- Larvae bright red orange
- Often found on legs, belly or face/head of grazers
- Hypersensitivity to bites
Describe signs of infestation with Trombicula autumnalis
- Hypersensitivity to bites
- Pruritus, erythema, scratching
- Signs contiue after mites have gone as fed mites drop to gound to moult to nymph
Name the guinea pig fur mite
Chirodiscoides
Name the rabbit fur mite
Listrophorus
Describe Chirodiscoides
- Mites on hair rather than skin
- Few clinical signs even with large infestation
- Direct contact, animal bedding or hair and debris for transmission
Describe Listrophorus infestation
- More severe signs if heavily infested
- Problem if already diseased
- Found on hairs rather than skin
Describe Dermanyssus mites
- Chicken red mites
- Live of bird and take blood meal at night
- Causes loss of condition, drop in egg production, severe infestation may lead to death due to anaemia
- Load can build up easily in hutches
What are the signs of Dermanyssus infestation?
- Increased dust bathing
- Balding
- Looking uncomfortable
Describe Ornithonyssus
- Northern fowl mite
- Blood feeder
- May spread several infections, but main problem is direct damage
Describe the life cycle of Ornithonyssus
- Primarily on host for entire life cycle
- Can live off host for 2-3 weeks
Describe the clinical signs of Ornithoyssus infestation
- Greay-black on feathers
- Chewed feathers
- Matting and scabbing
- Reduced production
- Anaemia
- Occasionally death
Compare the appearance of burrowing and surface mites
- Surface: long legs, some hairier than others, hairs point backwards for grip
- Burrowing: rounded, short legs, tuck legs in once burrowed
How can mites be distinguished?
- Host
- Appearance
- Location on host
What are the principles of control of mite infections?
- Removal of host infection
- Treat enviornment in some cases (esp. Ornithonyssus or Dermanyssus)
- Chemical shampoos and systemic treatments
What class and subclass do mites belong to?
- Class: Arachnida
- Subclass: Acari
Compare the body parts of insects and arachnids
- Insects: 3 body parts (head, thorax, abdomen)
- Arachnids: 2 body parts (head/gnathosome and body/idiosoma)
Describe the life cycle of arachnids
- Hemimetabola
- Most are free living and not parasitic
What is mite infestation called?
Acariasis
What are some general direct effects of acariasis?
- Direct epidermal damage e.g. skin erythema, pruritus, scale formation, lichenification, crust formation
- Production of cutaneous hypersensitivity
- Loss of blood or other fluids
What are some general indirect effects of mites?
May be mechaical or biological vectors of pathogens
