Parasitic Mites

Sarcoptes Scabiei

Believe it or not, mites are one of my favourite topics in parasitology. WHY???  Well they look like little round footballs, at least Notoedres which is found in cats does. I'll post a picture later and you can see what I mean. Plus, they're really important in DOGS. So why wouldn't I like the topic eh.... Scabies... 

Picture from giant microbes- an
amazing site for vet students/medics!

Sarcoptes Scabiei

• The entire life cycles takes place on the host.
• The fertilised female creates winding tunnels parallel to the skin surface and feeds on the fluid between cells. This is an example of a burrowing mite. 
• Tunnels are 1-2 big and contain a single female mite. Mites can lay up to 3 eggs/day and these hatch in 3-4 days. 
• Larvae exit the tunnels and moult to eight legged protonymphs and then tritonymphs and finally. Larvae have six legs whilst adults have eight legs. This also applies to tick species.
• 14 day life cycle. 
• Diagnosis requires several deep skin scrapings. 

Significance

• Intense pruritis (itchiness) and scratching.
• Papular lesions which can rupture leading to hair loss and crusting.
• Most severe on the head and neck but can spread to all over the body. 

Cattle- rare. Head, neck and tail. Leads to hair loss, thickened skin, scaling and secondary trauma.

Sheep- rare & notifiable.

Dog- on the face and ears. Treat with selamectin or fipronil. 

Cat- rare.

Pigs- ears, back and legs. 

Horses- rare & notifiable. 

Diagnosis-> itchy dog. Can cause transient dermatitis in humans. 

Notoedres 

• Face, head and ears of cat.
• Severe mange which can be fatal.
• Selamectin treatment. 
• Burrowing mite.

Knemidocoptes

• K.mutans- foot and leg of poultry. Leads to extensive crusting.
• K.pilae- budgies and parrots. Light feathered areas affected and present with a scaly face.
• K.laevisgallinae- poultry and pheasants 'depluming itch.' 
• Treat topically. 

Demodex

Demodex in H & E stain.

• Demidecosis in the dog. Follicle dwelling mites. 
• Usually exist as harmless commensals.
• 18-24 day life cycle.
• Eggs-> two larval stages-> two nymphal stages-> adults.
• Transmission is via mammary skin whilst suckling. 
• Localised-> young dogs where lesions may spontaneously resolve.
• Generalised-> severe and complicated by secondary bacterial infections. Presents with thickened skin, pustules and crusts. 
• Diagnose via several deep skin scrapings.
• Treatment may be difficult. Use a mixture of antibiotics and selamectin/amitraz. 

Psoroptes Ovis

• Non-burrowing mite.
• Feeds on skin scales/lymph.
• Sheep scab and cattle mange. Withers, neck, tail and other parts of the body. Treat with ivermectin.
• Prevalent in winter.
• Horses- tail and neck.
• Psoroptes Cuniculi- rabbits ear mange. Sometimes seen in sheep.Treat with ivermectin/moxidectin. 
• Species differentiated by jointed pedicels and trumpet shaped suckers. 

Chorioptes 

• Non-burrowing.
• Mange due to the chewing activity, less severe than psoroptes or sarcoptes but more common. 
• Winter.
• Unjointed pedicels and cup shaped suckers. Differentiate from psoroptes ovis in sheep. 
• Cattle-> neck, head, udder and base of tail. Hair loss, itching, scaling and mild mange.
• Sheep-> all areas. Hair loss, thickened skin and scaling. Causing stamping.
• Horses-> lower limbs in the feathered fetlocks. Causes stamping. 
• Treatment with fipronil or selenium sulphide. 

Otodectes Cynotis

• Dog & cat.
• Feed on ear debris with a 3 week life cycle. Transmission is by direct contact. Deep in ear near drum. Cat= brown waxy exudate and crusting. 
• Intense itching and head shaking.
• Secondary bacterial infection- purulent otitis externa. 50-80% cases.

Cheyletiella 

• Fur commensal.
• Scaling dermatosis.
• Lesions dorsal on the rump and shoulders.
• Dog, cat & rabbit.
• Large claws on the palps.
• Papules on the arms and abdomen in humans.
• Treat with fipronil for dogs and cats and ivermectin for rabbits.

Trombicula

• Parasitic larvae.
• Autumn.
• Lower limbs of animals
• Groups of pale orange patches.
• Mild pruritis, erythema (reddening) and crusting. 
• Treat with fipronil. 

Dermanyssus Gallinae

• Birds.
• Poultry red mite.
• Nocturnal- hidden in accommodation structure in daylight.
• Bright red.
• Survives for month in empty accommodation.
• Rapid population build up. 
• Pruritis, papules and crusting.
• Acaracides for treatment. Treat accommodation- eradication difficult.
• Not seen on bird generally.
• D shaped anal plate. 

Ornithonyssus Sylviarum 

• Permanent blood sucking mite.
• Found on birds themselves.
• Anal plate= pear shaped.