Lecture 23: Parasitic mites

What is the main structural difference between ticks and mites?

Ticks have a fused two-piece body plan with no constriction between the head and body, while mites sometimes have distinguishable head and body regions.

What is a key size difference between ticks and mites?

Ticks are larger than mites.

What is the difference in the hypostome between ticks and mites?

Ticks have a toothed hypostome, whereas mites have a smooth hypostome.

Do all ticks suck blood?

Yes, all ticks suck blood at all life cycle stages.

Are all mites parasitic?

No, most mites are free-living, but some are parasitic.

How do the respiratory structures of mites differ?

Mites have stigmata/spiracles that vary in location.

What are the three basic morphological groups of mites?

Mesostigmatid, Astigmatid, Prostigmatid.

What are three ways mites cause disease?

1. Some suck blood and may cause anemia.

2. Cause dermatosis—piercing skin, irritation, inflammation, sloughing skin, oozing lymph.

3. Facilitate secondary bacterial infections.

Where are the stigmata located in mesostigmatid mites?

Between the 3rd and 4th pair of legs.

Where are the legs (coxae) located in mesostigmatid mites?

Evenly spaced in the anterior half of the body.

What feature is present at the end of the legs in mesostigmatid mites?

Claws on the end of the tarsi (last segment of the leg).

Are mesostigmatid mites typically parasitic?

Most are free-living, but some are parasitic.

Where is Dermanyssus gallinae commonly found?

In nests and bedding, off the host except when feeding (vampire model).

How does Dermanyssus gallinae affect poultry production?

Causes significant production losses due to anemia from voracious blood-sucking, especially in young birds.

What is the zoonotic impact of Dermanyssus gallinae?

Causes annoyance, irritation, and discomfort in humans.

How do people become infested with Dermanyssus gallinae?

Through contact with mite-infested nests, sometimes leading to near psychopathologic effects.

How is Dermanyssus gallinae diagnosed?

By identifying its needle-like chelicerae.

What is the body structure difference between ticks and mites?

Ticks have a fused two-piece body plan with no constriction between the head and body, while mites sometimes have distinguishable head and body regions.

How does the size of ticks compare to mites?

Ticks are larger than mites.

What is a key difference in the hypostome of ticks and mites?

Ticks have a toothed hypostome, whereas mites have a smooth hypostome.

Are all ticks parasitic?

Yes, all ticks are parasitic at all life cycle stages.

Do all mites live parasitically?

No, most mites are free-living, but some are parasitic.

What is a respiratory difference between ticks and mites?

Mites have stigmata/spiracles that vary in location.

What are three ways mites can cause disease?

1. Some suck blood, which may cause anemia.

2. Cause dermatosis—piercing skin, irritation, inflammation, sloughing skin, oozing lymph.

3. Facilitate secondary bacterial infections.

How are the legs (coxae) positioned in mesostigmatid mites?

Evenly spaced in the anterior half of the body.

Are mesostigmatid mites parasitic?

Most are free-living, but some are parasitic.

What is the main economic impact of Dermanyssus gallinae in poultry?

Causes significant production losses due to anemia from voracious blood-sucking, especially in young birds.

What zoonotic effects does Dermanyssus gallinae have on humans?

Causes annoyance, irritation, and discomfort.

How can people become infested with Dermanyssus gallinae?

Through contact with mite-infested nests, sometimes leading to near psychopathologic effects.

What are the two main species of Ornithonyssus and their hosts?

O. sylviarum (Northern Fowl Mite) - Poultry

O. bacoti - Rodents

Where is Ornithonyssus found on its host?

On the host, unlike Dermanyssus, which is found in nests and bedding.

What clinical signs are associated with Ornithonyssus infestation?

Annoyance, irritation, discomfort.

How can humans be affected by Ornithonyssus?

People can become infested through contact with mite-infested nests, sometimes leading to near psychopathologic effects.

How is Ornithonyssus diagnosed?

By identifying its scissor-like chelicerae.

Do astigmatid mites have stigmata?

No, they respire cutaneously.

How are the legs positioned in astigmatid mites?

The 2nd and 3rd pair of legs are widely separated.

What feature is present at the end of the legs in astigmatid mites?

Suckers on the end of the tarsi (last segment of the leg).

Are most astigmatid mites parasitic?

Yes, most are parasitic—either surface-dwelling or skin-burrowing.

Is Psoroptes ovis a surface-dwelling or burrowing mite?

Surface-dwelling.

Where does the life cycle of Psoroptes ovis occur?

Entirely on the host.

How does Psoroptes ovis feed?

Pierces skin with needle-like chelicerae and feeds on oozing serum.

What is a characteristic lesion caused by Psoroptes ovis?

Psoroptic scab, formed from coagulated serum.

What are clinical signs of Psoroptes ovis infestation?

Hair loss from rubbing and inflammation of the dermis.

How is Psoroptes ovis diagnosed?

By finding mites at the edge of a scab.

What is a key morphological feature of Psoroptes ovis?

Suckers on long pedicles at the end of the tarsi.

Is Psoroptes ovis a reportable disease?

Yes, it must be reported to the State Vet and USDA.

Is Chorioptes bovis a surface-dwelling or burrowing mite?

Surface-dwelling.

Where does the life cycle of Chorioptes bovis occur?

Entirely on the host.

Does Chorioptes bovis pierce the skin?

No, it feeds on sloughed epidermal and epithelial debris.

What are the clinical signs of Chorioptes bovis infestation?

Mildly pruritic, flaky dermatitis affecting legs, tail, and pubic regions.

How severe is Chorioptes bovis infestation?

Generally self-limiting.

How is Chorioptes bovis diagnosed?

By finding mites on the host in areas of dermatitis.

What is a key morphological feature of Chorioptes bovis?

Suckers at the end of the tarsi.

Is Chorioptes bovis a reportable disease?

No, it is not reportable.

Is Otodectes cynotis a surface-dwelling or burrowing mite?

Surface-dwelling.

Where does the life cycle of Otodectes cynotis occur?

In the outer ear canal of the host.

Does Otodectes cynotis pierce the skin?

No, it feeds on sloughed epidermal and epithelial debris.

What are clinical signs of Otodectes cynotis infestation?

Mild pruritus and black, waxy cerumen in the outer ear.

How is Otodectes cynotis diagnosed?

Ear swab of the outer ear canal and observation of mites.

What morphological feature does Otodectes cynotis have at the end of its legs?

Suckers at the end of the legs.

Are Sarcoptes spp. mites surface-dwelling or burrowing?

Burrowing.

What is a distinguishing body characteristic of Sarcoptes spp.?

Chubby body with short legs.

Where does the life cycle of Sarcoptes spp. occur?

Entirely on the host.

How do Sarcoptes spp. mites cause skin damage?

They burrow into and tunnel under the skin.

What areas of the body are most affected by Sarcoptes spp.?

Pinna of the ear, inguinal area, and hairless portions of the body.

What do Sarcoptes spp. mites feed on?

Serum, fluids, and host proteins.

What are the clinical signs of Sarcoptes spp. infestation?

Pruritic, papular erythema related to burrowing, defecation, and egg-laying.

Formation of sarcoptic scabs from oozing serum due to scratching and self-mutilation.

Hair loss from rubbing and inflammation, extending a suitable habitat for more mites.

How is Sarcoptes spp. diagnosed?

Deep skin scrape at the edge of a scab to find mites.

Are livestock infestations with Sarcoptes spp. reportable?

Yes, they are reportable to the State Vet and USDA.

What species does Sarcoptes scabiei var. canis affect?

Dogs (Canine mange mite).

Is Sarcoptes scabiei var. canis easy to demonstrate?

No, it is hard to demonstrate because it burrows.

How is Sarcoptes scabiei var. canis diagnosed?

Deep scrape at the edge of a crusty lesion.

Where does Sarcoptes scabiei var. canis cause alopecia?

In the inguinal areas.

What is the pinna/pedal reflex, and how is it used for diagnosis?

Scratch the underside of the ear flap.

~95% of dogs that exhibit the reflex are infested with Sarcoptes.

Where is the anus located in Sarcoptes scabiei var. canis?

Ventral surface.

What species does Notoedres affect?

Cats (Feline mange mite).

How does Notoedres compare to Sarcoptes in terms of burrowing?

More often found on the surface in fur, making it easier to demonstrate on a skin scrape.

Where is the anus located in Notoedres?

Terminal margin of the ventral surface.

What are the over-the-counter (OTC) treatment options for ear mites?

Pyrethrin-based solutions such as Otomite Plus, applied in the ear at 7-day intervals.

At what age is Otomite Plus safe for use in cats and dogs?

> 4 weeks of age.

What prescription treatment can be used for ear mites as a single application?

Milbemite (same drug as Interceptor)

What must be done before treating ear mites?

Clean the ears first.

What is the efficacy of Revolution (selamectin) in treating scabies?

93-100% efficacy after 2 monthly treatments.

What other drugs are used to treat scabies?

Ivermectin (200-400 μg/kg).

Imidacloprid-Moxidectin (Advantage Multi) at labeled monthly dose, effective after 2 treatments.

Milbemycin oxime / Spinosad (Trifexis) at 2 mg/kg, twice weekly for 3-4 weeks.

How is scabies treated in humans?

5% permethrin cream, applied to affected areas and washed off after 8-14 hours.

Why is 5% permethrin cream not always ideal for human treatment?

It is safe but expensive.

What is unique about the Prostigmatid mite group?

It includes a diverse range of mites, from totally parasitic to free-living species that are only incidentally related to disease.

What are the two body shapes seen in Prostigmatid mites?

Mite-shaped bodies and cigar-shaped bodies.

What are the two forms of demodectic mange?

Localized and Generalized.

Where do lesions commonly occur in localized demodectic mange?

Around the muzzle, eyes, and pinnae.

What is a key risk factor for localized demodectic mange?

Immune naïve animals, typically obtained from nursing mother.

Is localized demodectic mange self-limiting?

Yes, it is generally self-limiting.

What is the common name for generalized demodectic mange?

Red mange.

What are the clinical signs of generalized demodectic mange?

Dry, flaky skin.

Erythema around elbows and bony projections.

Alopecia around eyes and pinnae.

What type of animals are at risk for generalized demodectic mange?

Immunocompromised animals.

Why is generalized demodectic mange difficult to control?

It requires identifying underlying metabolic conditions and is impossible to cure.

What is the common name for Cheyletiella spp.?

Walking Dandruff Mite.

What distinctive morphological feature does Cheyletiella have?

Massive palpal claws.

What animals can be affected by Cheyletiella?

Dogs, cats, and rabbits.

Does Cheyletiella have zoonotic potential?

Yes, it can infect humans.