Parasitic Insects, Mites and Ticks: Genera of Medical and Veterinary Importance/Burrowing mites

Burrowing feeders: Mange mites
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Characters of burrowing mange mites (Sarcoptic-mites and Knemidokoptic-mites)
The legs are short, and may be equipped with terminal suckers or pulvilli. Claws are not well developed. The first segment (coxa) may have a thickened extension (an apodeme) that joins it to the coxae of other legs. Body profile is circular and these are all small mites. Mouthparts are small and do not protrude far from the body margin. Setae are mostly long and protrude from the body margin or ends of some pairs of legs. Dorsal surface has distinct striations and scales, and sometimes spines. Feeding is by burrowing through living layers of the epidermis and the life-cycle is spent entirely within skin of the host.
 * Photograph shows Notoedres mange mite of cats and dogs.


 * Diagram of feeding at skin represents sarcoptic burrowing mites feeding as endoparasites within the living layers of the epidermis of their host.

Glossary

 * Hair follicle = A deep cylindrical pit in the skin of mammals formed by an inversion of the epidermis down to the root tissue forming a hair; sebaceous glands secrete into the space between the hair and epidermis. This space may be infested with Demodex mites (see diagram of Demodex feeding).
 * Pulvillus = An adhesive organ on the ends of some legs of many acarines; similar to a sucker but without the distinctive cup shape of a sucker (4 on Pneumonyssus).
 * Sucker = A cup shaped adhesive organ at the ends of some legs of some mites (3 on Sarcoptes).
 * Zoonotic = Description of an infection or infestation that is transmissible from domestic or wild animals to humans.

Sarcoptes (Sarcoptidae)
Characters: females, dorsal left, ventral right. 1- Dorsal surface has a large area of spines and backward pointing scales. 2- Mouthparts are short. 3- Legs 1 and 2 have small suckers on long plain pedicels. 4- Legs 1 and 2 have the apodemes on their first segment joined in a Y shape. 5- Anus is situated ventrally. 6- Legs 3 and 4 are short and do not protrude beyond body margin; their apodemes are medium length and not joined. 7- Long setae are borne from ends of legs 3 and 4. Also: the profile of an egg is shown lower right.

Hosts: Infestation occurs on pigs, sheep, goats, horses, donkeys, camels, dogs, and humans. Mange caused by Sarcoptes is one of the most damaging diseases of camels, sometimes fatal. Sites of infested skin on a typical host vary but are commonest on ears and head, back, abdomen and groin. Humans are natural hosts with infestation transmitted between themselves. Also humans are easily infested zoonotically, from close contact with infested domestic animals. Signs and symptoms: Sarcoptes scabiei (Scabies-mite) forms tunnels in living layers of host skin (mainly in stratum spinosum) leaving antigenic feces. The host reacts with intense pruritus, inflammation, erythema, and thickening of skin. A secondary rash may appear at non-infested sites. Self-grooming is repeated frequently. Infestations of humans are most often found on either individuals living in severe poverty, or with larger groups of people forced to crowd together under conditions of collapsed social welfare.

Disease: Some infestations are at a low level, with little harm, but intense infestations may lead to loss of appetite and weight, with severe stress and exhaustion.

Notoedres (Sarcoptidae)
Characters: females, dorsal left, ventral right. 1- Dorsal surface has a group of setae shaped like rods, and backward pointing scales. 2- Mouthparts are short. 3- Legs 1 and 2 have small suckers on long plain stalks. 4- Legs 1 and 2 have the apodemes on their first segment joined in a Y shape. 5- Legs 3 and 4 are short and do not protrude beyond body margin; their apodemes are long and not joined. 6- Legs 3 and 4 bear long terminal setae. 7- Anus is situated dorsally.

Hosts: Notoedres cati burrow in living layers of skin on ears and head of cats, and may also infest dogs. Notoedres muris infests rats, including laboratory and pet animals.

Signs and disease: Pruritus, inflammatory and hypersensitive responses are caused, as with Sarcoptes. Dry and crusty lesions form at sites of infestation, together with damage to skin (excoriation) caused by self-grooming.

Knemidokoptes, or Knemidocoptes (Knemidokoptidae)
Characters: females, dorsal left, ventral right, also inset is part of a male. 1- Dorsal surface has a group of irregular blunt scales; there are no spines. 2- Mouthparts are short. 3- Legs of females are without suckers or pulvilli and the setae here are short. 4- Males have all legs with pulvilli on plain stalks, and setae on legs are long. 5- Legs 1 and 2 have the apodemes separated widely (these apodemes on males are joined in a Y shape). 6- Legs 3 and 4 are short and do not protrude beyond body margin; their apodemes are long and not joined. 7- A pair of long setae protrude from posterior body margin. 8- Anus is situated dorsally.

Hosts: Birds are the hosts: Knemidokoptes gallinae (Depluming-mite) burrows into the feather shafts of poultry birds; Knemidokoptes mutans (Scaly-leg mite) burrows into the skin on feet and legs of poultry and other species of bird.

Signs: The Depluming-mite will infest all feathered regions of the body. The resulting pruritus leads to the bird pulling out the feathers and the skin becomes papular and thickened. Scaly-leg mites burrow in skin of the lower parts of legs and the feet leading to deformed leg scales and nodular thickening of skin.

Disease: Heavy infestations cause stress, intensive self-grooming and anorexia, leading to loss of production.

Characters of taxonomically diverse mites infesting sheltered sites within body (a clinical grouping)
Demodex mites infest the space within a hair follicle. This space technically is external to the epidermis, but within the bulk of the skin, so Demodex mites can be considered as ectoparasites. Pneumonyssus and Cytodites mites infest the sheltered habitats of nasal cavities, and airsacs and lungs respectively and thus behave as endoparasites. Laminosioptes mites behave as endoparasites, infesting subcutaneous tissues.
 * Diagram of feeding at skin represents Demodex mites as ectoparasites but deep within the hair follicle of their mammalian host (relative scale of mites exaggerated).

Demodex (Demodicidae)
Characters: adult, ventral. 1- Body profile is uniquely distinctive: elongated to a posterior point, with four pairs of stubby legs protruding. 2- Legs end in blunt claws; pulvilli or suckers are absent. 3- Mouthparts are short and blunt. 4- Setae and similar structures on body surface are very few or absent. 5- Posterior body has many transverse striations. 6- Size of these mites is minute.

Hosts: All species of domestic mammals, also humans and many other mammals that have been investigated become infested with Demodex species soon after birth, by contagion during suckling. Signs and symptoms: In domestic animals inflammatory and hypersensitive reactions to heavy infestations may sometimes lead to a widespread thickening of the skin. This thickening includes the sebaceous glands, which fill with mites and secretion. In cattle, conspicuous flat nodules form in the skin. In dogs, there is a more generalized skin thickening leading to a corrugated and depilated skin surface. Infestations of humans rarely develop into a disease state.

Disease: Most individual animals or humans develop little or no evidence of their chronic low levels of infestation; this is parasitism without clinical pathogenicity. However, often a few individuals of a host population seem immunologically unable to prevent their Demodex infestations expanding. Demodex infestation seems not to cause pruritus, so demodecosis as a veterinary problem relates more to the disgusting appearance of heavily infested animals, especially when bacterial infections develop in the infested skin. Commercial value of cattle hides is reduced.

Pneumonyssus (Halarachnidae)
Characters: adult, ventral. 1- Body profile is a smoothly rounded oval. 2- Mouthparts are short in some species (palps may be distinct in other species). 3- All legs are stout and protrude distinctly from body margin. 4- Legs end in a pair of claws and a pulvillus. 5- A sternal plate is present, of varied shape and with pairs of setae (a dorsal plate is also present). 6- Integument is mostly smooth, without striations and with few setae.

Hosts: Pneumonyssus caninum (Nasal-mite) infests the nasal sinuses of dogs; P. simicola (Lung-mite) infests the lungs of monkeys and baboons.

Signs and disease: Nasal-mites cause head shaking, sneezing, rhinitis and sinusitis. Heavy infestations may lead to the dogs becoming listless, anorexic and partially losing some of their sense of smell. Lung-mites infesting Rhesus monkeys are known to cause coughing and sneezing, but massive infestations sometimes occur with serious consequences.

Cytodites (Cytoditidae)
Characters: female dorsal left, male ventral right. 1- Body profile is broad anteriorly, narrowing posteriorly. 2- Mouthparts are simplified to form a sucking tube. 3- Legs are stout and protrude distinctly from body margin. 4- Legs end in a small pulvillus: in females the pulvillus is on a stalk but in males a stalk is absent. 5- First segment of legs (coxa) of males and females have their apodemes fused to form a Y shape. 6- Integument is generally smooth, without striations; setae are fine and sparse.

Hosts: Cytodites nudus (Airsac-mite) infests the airsacs and lungs of poultry birds and other bird species.

Signs and disease: Light infestations seem to cause little clinical problem, but if the infestation grows massive then the consequences can be fatal.

Laminosioptes (Laminosioptidae)
Characters: female, ventral. 1- Body profile is an elongate oval. 2- Mouthparts are short. 3- All legs are well developed, protrude from body margin and end in stalks. 4- Apodemes of legs 1 are joined into a Y shape. 5- Integument is generally smooth, without striations; setae are distinct but sparse. 6- A pair of long setae extends from posterior margin of body.

Hosts: Laminosioptes cysticola (Fowl cyst-mite) infest the subcutaneous tissues of birds.

Signs and disease: Small cysts develop around the mites, widely distributed on host's body. Severe infestations can develop in some individual hosts.

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