Difference between revisions of "Mites"

From WikiVet English
Jump to navigation Jump to search
(Redirected page to Category:Mites)
 
(39 intermediate revisions by 3 users not shown)
Line 1: Line 1:
{{review}}
+
#REDIRECT[[:Category:Mites]]
 
 
{{toplink
 
|backcolour =
 
|linkpage =Parasites
 
|linktext =PARASITES
 
|pagetype=Bugs
 
|sublink1=Arachnida
 
|subtext1=ARACHNIDA
 
}}
 
<br>
 
 
 
==Astigmata Introduction==
 
 
 
Mites are one of the most successful and diverse vertebrate groups. The species of veterinary importance are parasitic, although a few non-parasitic mites are also important, such as oribatid and forage mites.
 
 
 
Mites are very small, on average under 0.3mm in length and for this reason often go unnoticed. They spend the majority of their life cycle '''on''' the host and cause '''mange'''.
 
 
 
The body shows no segmentation but can be divided into two sections, the '''idiosoma''' and the '''gnathosoma'''. Adult and nymphs have '''four''' pairs of legs, whereas larvae have only '''three''' pairs of legs.
 
 
 
The taxonomy of mites is complex as there are over 8 families. In this article the families are split according to their location on the host into sub-surface (burrowing) and surface (non-burrowing) mites.
 
 
 
==Burrowing Mites==
 
 
 
===Sarcoptidae===
 
====''Sarcoptes''====
 
 
 
'''Recognition'''
 
*Small, round mite
 
 
 
*Short legs
 
**Project only a short distance from body margin
 
 
 
*Dorsal spines
 
**Arranged in rows
 
 
 
*Terminal anus
 
 
 
*Male is about 250μm in length and the female about 400-430μm in length
 
 
 
'''Life Cycle'''
 
*3 weeks life cycle
 
 
 
*Female lays eggs in epidermis in an '''egg laying pocket'''
 
 
 
*Female feeds on liquid oozing from damaged tissue
 
 
 
*The eggs hatch in 1 week
 
 
 
*'''6 legged''' larvae released which crawl to skin surface
 
 
 
*The larvae then burrow back into the epidermis into '''moulting pockets'''
 
 
 
*Larvae moult to become '''8 legged''' nymphs
 
 
 
*Nymphs moult twice before becoming adults
 
 
 
*Adult males emerge and look for females to mate
 
 
 
'''Transmission'''
 
 
 
*Close contact
 
 
 
*Adults and larvae can be transferred from one skin surface to another
 
 
 
'''Pathogenesis'''
 
 
 
*Erythema with papule formation
 
 
 
*Scale and crust formation
 
**Alopecia
 
 
 
*Intense pruritis for one week
 
**Self-inflicted trauma
 
**Scab formation
 
 
 
*Wrinkling and thickening of skin
 
 
 
*Hypersensitivity may develop
 
**Rash develops
 
 
 
*''Sarcoptes scabiei''
 
**In [[Parasitic skin infections - Pathology#Scabies|scabies]]
 
 
 
*Strains of ''S. scabiei'' can be passed between different animals and cause clinical signs although the infection is likely to resolve spontaneously and be unlikely to establish
 
 
 
'''Diagnosis'''
 
 
 
*Skin scraping until capillary blood appears
 
**Adults, eggs, immature mites and faecal pellets can be seen microscopically
 
 
 
*Place material on a microscope slide
 
 
 
*Add 10% KOH
 
 
 
*Warm slide over bunsen flame
 
 
 
'''Treatment'''
 
 
 
*Acaricide
 
**For more information on acaricides click [[Ectoparasiticides|here]]
 
 
 
*Treat both infected and in-contact animals
 
 
 
*Older products have to be given in repeat treatments
 
 
 
*Avermectins are effective in farm animals
 
 
 
*Selamectin is available as a good spot-on for dogs
 
 
 
*Control for pigs:
 
**Treat sows before entering the farrowing pen
 
**Treat boars at 6 month intervals
 
 
 
=====Sarcoptic Mange=====
 
'''Dogs'''
 
*Highly contagious
 
 
 
*Intense pruritus
 
 
 
*First signs appear at edges of ears, then progresses to muzzle, face and elbows
 
 
 
'''Cats'''
 
*Rare
 
 
 
'''Pigs'''
 
*Important condition as 35% pigs are asymptomatic carriers
 
 
 
*First signs of infestation appear on the ears before spreading to the rest of the body
 
 
 
*Transmission from sow to piglets whilst suckling and from boars to gilts at service
 
 
 
*Infestation adversely affects productivity
 
 
 
'''Cattle'''
 
*Most frequently seen in housed cattle
 
 
 
*Notifiable in USA and Canada
 
 
 
*Often called 'neck and tail mange' as lesions most often seen on neck and tail
 
 
 
*Infestation adversely affects productivity
 
 
 
'''Sheep'''
 
*Notifiable in UK
 
 
 
*Lesions on hairy parts of face
 
**E.g. Face, ears, axillae and groin
 
 
 
*Causes considerable hide damage in local African breeds of long haired sheep
 
 
 
'''Horses'''
 
*Notifiable in UK
 
 
 
*Lesions begin on head, neck and shoulders then spread to rest of body
 
 
 
====''Knemidocoptes''====
 
[[Image:Clinical Case 2 03.jpg|thumb|right|150px|''Knemidocoptes'' Mite under Light microscope (Courtesy of C. Antonczyk)]]
 
[[Image:Clinical Case 2 01.jpg|thumb|right|150px|Chicken with Scaly Leg (Courtesy of C. Antonczyk)]]
 
*Only genus of burrowing mites which occurs on avian species
 
 
 
*Life cycle similar to ''Sarcoptes spp.''
 
 
 
*Diagnosis based on clinical signs and discovery of mites
 
 
 
*Repeat treatments with [[Ectoparasiticides|acaricides]] needed
 
**Few products licensed for use in poultry
 
 
 
'''Recognition'''
 
 
 
*Small, round mite
 
 
 
*Short legs
 
 
 
*U-shaped chitinous bar behind head
 
 
 
*Terminal anus
 
 
 
*''K. mutans''
 
**Scaly leg in poultry
 
**Mites burrow beneath leg scales causing them to loosen and rise
 
**Ragged appearance to legs and feet
 
**Distorted claws and feet
 
**Infected birds are usually lame
 
 
 
*''K. gallinae''
 
**Depluming itch in poultry
 
**Burrow into feather shafts
 
**Intense pain and pruritus
 
**Birds pull out body feathers
 
 
 
*''K. pilae''
 
**Scaly face and beak in psittacines
 
**Mites attack bare or lightly feather areas of the face, beak, cere and body
 
**Scaliness at the base of the beak is the first sign which then spreads
 
**Little pruritus
 
 
 
===''Trixacarus''===
 
 
 
*Similar to ''Sarcoptes'' but half the size
 
 
 
*Causes severe pruritus in laboratory rodents
 
 
 
*Burrowing activity causes biting, scratching and irritation
 
**Leads to inflammation, pruritus and alopecia
 
 
 
*Affected areas show acanthosis and hyperkeratosis
 
 
 
*Death can occur within 3-4 months of infection
 
 
 
*Transmission is due to close contact between mother and offspring
 
 
 
===''Demodex''===
 
 
 
*''Demodex'' spp. found on all domestic mammals and in humans
 
**Each host has its own species
 
 
 
*Causes [[Parasitic skin infections - Pathology#Demodicosis|demodecosis]]
 
 
 
'''Recognition'''
 
*Cigar shaped
 
 
 
*Four pairs of stumpy legs on the anterior end
 
 
 
*Long and narrow to fit into hair follicles
 
 
 
'''Life Cycle'''
 
*Live as commensal organisms
 
 
 
*Live in hair follicles and in sebaceous glands
 
 
 
*Life cycle takes 3 weeks
 
 
 
'''Pathogenesis and Epidemiology'''
 
*Initial infection is slight hair loss which may resolve spontaneously or could spread over the body
 
 
 
*Squamous demodecosis
 
**Less serious
 
**Dry reaction
 
**Alopecia, desquamation and skin thickening
 
**Absent to mild pruritus
 
 
 
*Follicular/pustular demodecosis
 
**More serious
 
**Skin invasion by ''Staphylococci''
 
**Skin becomes wrinkled, thickened and contains pustules which ooze serum, blood or pus
 
**Affected animals may be seriously disfigured
 
**Severe pruritus is associated with secondary infection
 
 
 
*Immune factors are important in determining the severity and occurrence of demodecosis
 
**Familial susceptibility
 
**Immunosuppression
 
**Immunosuppressant therapy
 
 
 
'''Cats'''
 
*Rare
 
 
 
*Confined to the periocular region
 
 
 
*Mild squamous type only
 
 
 
'''Cattle'''
 
*Pea-sized nodules in the skin
 
**Each nodule contains several thousand mites
 
 
 
*Affects hide quality
 
**Economically important in Australia
 
 
 
'''Goats'''
 
*Becoming more common in goats
 
 
 
*Disease similar to that in cattle
 
 
 
'''Pigs, Sheep and Horses'''
 
*Rare
 
 
 
'''Diagnosis'''
 
 
 
*Liquid paraffin applied to a skin fold
 
 
 
*Deep skin scraping
 
 
 
'''Control'''
 
*Not easily accessible to acaricides due to their deep location in the skin
 
 
 
*Repeat treatments needed
 
 
 
*Recovery may take several months
 
 
 
*To aid [[Ectoparasiticides|acaricide]] penetration, clipping a dog's coat and washing is recommended
 
 
 
===''Notoedres''===
 
 
 
*Known as feline scabies
 
 
 
*Also common ectoparasites of tropical bats
 
 
 
*Parasite of cats, rats, man and rabbits
 
 
 
'''Recognition'''
 
*Similar to ''Sarcoptes''
 
 
 
*Less distinct angles on body surface
 
 
 
*Females have suckers on legs one and two
 
 
 
*Females are about 225μm in length and males 150μm
 
 
 
*Anal opening is distinctly dorsal (not posterior)
 
 
 
'''Pathogenesis'''
 
*Infection begins on the ear tips and spreads over the body
 
 
 
*''Notoedres cati'' in [[Parasitic skin infections - Pathology#Notoedric mites|notoedric skin infestation]]
 
 
 
*Causes dermatitis
 
 
 
*Burrowing of females damages keratinocytes leading to cytokine release
 
 
 
*Hypersensitivity reaction may occur
 
 
 
'''Diagnosis'''
 
*Superficial skin scraping
 
 
 
*A single nest in a scraping may yield many mites
 
 
 
==Non-Burrowing Mites==
 
 
 
*Live on the skin surface
 
 
 
*Feed on either skin scales and tissue or suck blood
 
 
 
===''Psoroptes''===
 
*In [[Parasitic skin infections - Pathology#Psoroptic mites|psoroptic skin infestation]]
 
 
 
'''Recognition'''
 
*Oval shaped
 
 
 
*Long legs
 
 
 
*Funnel shaped suckers on '''segmented''' pedicels
 
 
 
*1-2mm in length
 
 
 
'''Life Cycle'''
 
*Confined to skin surface
 
 
 
*Feed on serous exudate by siphoning
 
 
 
*Adult female can lay up to 100 eggs during her life time (one month)
 
 
 
*10 day life cycle
 
 
 
*2 nymphal stages
 
 
 
====''Psoroptes cuniculi''====
 
*Parasite of rabbits
 
 
 
*Common among conventional rabbits
 
 
 
*Transmitted via contact
 
 
 
*Adapted to living in an aural environment
 
 
 
'''Pathogenesis'''
 
*The ears are painful and itch intensely
 
 
 
*Affected rabbits shake their heads and scratch their ears
 
 
 
*The inner surfaces of the pinnae are covered with brown, scaly, fetid material, and the skin beneath is raw
 
 
 
*Mites are grossly visible
 
 
 
*Histologically, there is chronic erosive and proliferative eosinophilic dermatitis
 
**The mites are non-burrowing and thus are found only in the exudate, not in the tissue
 
 
 
'''Diagnosis'''
 
*Microscopic examination for mites (low magnification)
 
 
 
*Appearance
 
 
 
'''Control'''
 
*Infestations are difficult to eliminate from a colony
 
**Ivermectin is usually effective
 
 
 
====''Psoroptes ovis''====
 
*Adult females are large mites at 750μm in length
 
 
 
*Males identified by copulatory suckers and paired posterior lobes
 
 
 
*Males attach to deutonymphs (second moult after larval stage) in a process called '''copula'''
 
**Males remain in copula until females moult for the last time
 
**Copulation occurs
 
 
 
*Life cycle last 14 days
 
 
 
*Transmitted by direct contact between sheep
 
 
 
*Indirect transmission can also occur
 
 
 
'''Pathogenesis'''
 
*Economically important ectoparasite of sheep
 
 
 
*Causes '''sheep scab'''
 
**Wool loss, restlessness, biting, scratching of infested area and decreased productivity through decreased weight gain
 
**Usually seen in late autumn and early winter (although may also occur in late summer)
 
**Population numbers decline after shearing due to a change in the microclimate, then build up again as the fleece grows
 
**Notifiable in UK
 
 
 
*Mites found under scabs and in skin folds
 
 
 
*Lesions most common on flanks, neck, back and shoulders
 
 
 
*Causes pruritic condition of cattle
 
 
 
*Active in keratin layer
 
 
 
*Mouthparts abrade the skin
 
 
 
*Antigenic material in mite faeces can lead to hypersensitivity reactions
 
 
 
'''Diagnosis'''
 
*Skin scraping
 
 
 
*KOH added
 
 
 
*Warm slide over a bunsen flame
 
 
 
*Examine under a microscope
 
 
 
===''Chorioptes bovis''===
 
*In [[Parasitic skin infections - Pathology#Chorioptic mites|skin infestation]]
 
 
 
*Surface parasite of horses and cattle
 
 
 
*Less pathogenic than ''Psoroptes''
 
**Mouthparts cannot pierce the skin
 
 
 
*3 week life cycle
 
 
 
'''Recognition'''
 
*Oval body
 
 
 
*Long legs
 
 
 
*Cup shaped suckers on '''unsegmented''' pedicels
 
 
 
*Females about 300μm in length
 
 
 
'''Pathogenesis'''
 
*Chorioptic mange
 
**Often seen in rough-legged horses with heavy feathering
 
**Induce crusty skin and lesions below the hocks and knees
 
 
 
*Mild condition in cattle
 
**Rubbing and scratching
 
**Hide damage
 
**Usually affects the base of the tail, perineum and udder
 
 
 
*Usually found on legs of sheep
 
**Mild condition
 
 
 
===''Otodectes cynotis''===
 
*in [[Parasitic skin infections - Pathology#Otodectic mites|otodectic skin infestation]]
 
 
 
*Commonest mange of dogs and cats in the world
 
 
 
*Inhabits the inner ear
 
 
 
*Also found in the fox and the ferret
 
 
 
*Closed keratinous bars ('''apodemes''') on ventral surface
 
 
 
*3 week life cycle
 
 
 
*Feeds on ear debris
 
 
 
'''Pathogenesis'''
 
*Only a few cats show symptoms
 
**Transmission occurs whilst kittens are suckling
 
 
 
*Common cause of '''otitis externa''' in dogs
 
 
 
*Brown waxy exudate produced
 
 
 
*Can lead to secondary infection
 
 
 
*Clinical signs apparent
 
**Head shaking, ear scratching and aural haematomata
 
 
 
'''Treatment'''
 
*Acaracidal ear drops
 
**Massage base of ear to disperse drops after treatment
 
 
 
*Most treatments need to be repeated in 10-14 days to kill newly hatched mites
 
 
 
*Selamectin can be used as a spot-on treatment
 
**Prolonged duration of action
 
 
 
*Treat all in-contact animals
 
**These may be asymptomatic carriers
 
 
 
===''Cheyletiella'' sp.===
 
 
 
*Surface mite of cats and dogs
 
**Also found on humans and rabbits
 
**''C.yasguri'' (dogs), ''C.blakei'' (cats and humans) and C.parasitivorax (rabbits)
 
 
 
*In [[Parasitic skin infections - Pathology#Cheyletiellosis|skin infestation]]
 
 
 
'''Recognition'''
 
*Waisted body
 
 
 
*Claw like palps on head
 
 
 
*Combs at ends of legs
 
 
 
'''Pathogenesis'''
 
*Highly contagious
 
 
 
*Mild pathogenesis
 
 
 
*Causes very scaly dermatitis
 
 
 
*Can be transferred to humans
 
 
 
'''Diagnosis'''
 
*Clinical signs
 
**E.g. Excess scurf
 
 
 
*Brush scurf onto dark paper
 
**'Walking dandruff' as mites will move when present in large numbers
 
 
 
*Skin scrapings
 
 
 
*Hair pluckings from scaly areas
 
**Eggs may be present
 
 
 
===''Dermanyssus gallinae''===
 
 
 
*'Red mite' of poultry
 
 
 
*Spends most of time '''off''' the host
 
**Adults and nymphs visit poultry at night to feed
 
 
 
*1 week life cycle
 
 
 
*Adults can survive several months without feeding so reservoirs can build up
 
 
 
'''Appearance'''
 
*Spider like mite with long legs
 
 
 
*White or grey
 
**Becomes red when engorged with blood after feeding
 
 
 
*Few hairs on body
 
 
 
*Hooks on legs
 
 
 
'''Pathogenesis'''
 
*Blood sucking mite
 
 
 
*Lesions usually found on the breast and legs
 
 
 
*Irritation, restlessness, decrease in egg production
 
 
 
*Anaemia can result if mites are present in large numbers
 
 
 
*Newly hatched chicks can rapidly die if infested
 
 
 
'''Treatment'''
 
*Acaricide
 
 
 
*Environmental treatment
 
 
 
*Remove wild bird nests
 
 
 
===''Ornithonyssus''===
 
 
 
*Also called the 'Northern mite' or 'Northern feather mite'
 
 
 
*Closely related to ''Dermanyssus''
 
 
 
*Hairy
 
 
 
*Spends enitre life cycle '''on''' the host
 
 
 
*Occurs in caged birds and poultry
 
 
 
*Causes feather to become matted and severe scabbing can develop
 
**Scabs particularly seen around the vent
 
 
 
*Decreases egg production
 
 
 
*Grey or black discolouration of feathers when large numbers of mites are present
 
 
 
===''Trombicula autumnalis''===
 
 
 
*In [[Parasitic skin infections - Pathology#Trombiculidiasis|skin infestation]]
 
 
 
*Also called the 'harvest mite'
 
 
 
*Not host-specific
 
**Will parasitise any animal, including humans
 
 
 
*Only the larval stage is parasitic
 
**Nymphal and adult stages are free-living in the soil
 
 
 
*Mite numbers are highest in late summer in temperate climates
 
**Mite numbers are constant all year in tropical regions
 
 
 
'''Recognition'''
 
*Six legs
 
 
 
*Bright orange in colour
 
 
 
*Hairy
 
 
 
*No spiracles
 
**Breath through cuticle
 
 
 
'''Pathogenesis'''
 
*Larvae insert mouthparts into skin and inject cytolytic enzymes
 
 
 
*Feed on partly digested host tissue
 
 
 
*Causes irritation
 
 
 
*Can cause a hypersensitivity reaction
 
 
 
*Mites found on head, ears and flanks of pets
 
 
 
*Mites found on face and limbs of grazing animals (depending upon host height)
 
 
 
'''Control'''
 
*Very difficult
 
 
 
===''Leporacarus''===
 
 
 
*Known as the 'rabbit fur mite'
 
 
 
*Found on rabbits (domestic and wild) and on hares
 
 
 
*Common
 
 
 
*Clings to individual hairs
 
 
 
*Feeds on sebaceous secretions and skin debris
 
 
 
*Non-pathogenic
 
 
 
*May cause dermatitis in humans handling infected animals
 
 
 
===Forage Mites===
 
 
 
*Pests of stored food products, hay and straw
 
 
 
*May cause skin reactions and respiratory/intestinal disturbances in animals and humans
 
 
 
*Control relies upon:
 
**Identifying and destroying infected feed and bedding
 
**Thoroughly cleaning feed storage bins
 
**Keeping feed storage areas clean and dry
 
 
 
===''Varroa destructor''===
 
[[Image:Varroa Mite .jpg|right|150px|thumb|Kika De La Garza Subtropical Agricultural Research Center Weslaco, Texas, USA (Wikimedia Commons)]]
 
[[Image:Varroa Mite on honeybee pupa.jpg|right|150px|thumb|Kika De La Garza Subtropical Agricultural Research Center Weslaco, Texas, USA (Wikimedia Commons)]]
 
*More commonly known as the 'honeybee mite'
 
 
 
*Notifiable disease in the UK
 
 
 
*Oval
 
 
 
*1-1.5mm in length
 
 
 
*Eggs are laid in the hive and develop with the brood cells
 
 
 
'''Pathogenesis'''
 
*Blood-sucking
 
 
 
*Weakens adult bees
 
 
 
*Damages growing larval bees resulting in deformities
 
 
 
'''Control'''
 
*Acaricidal strips hung between combs
 
 
 
*Destoy colonies in apiary (if isolated outbreak)
 
 
 
*Monitor mite numbers and treat if widespread
 
 
 
==Links==
 
 
 
[[Clinical Case 2]]
 

Latest revision as of 21:38, 18 May 2010

Redirect to: