Scab, mange and other mites are very small arachnid parasites. Most of them can be seen only under the microscope. Together with the ticks they form the class of acarina. Other arachnids are e.g. spiders and scorpions. Arachnids are part of the arthropodes, all those animals that have and external skeleton and jointed legs. Other arthropods are insects and crustaceans (e.g. crabs, lobsters, shrimp, etc).
There are about 50'000 mites species worldwide. All mites of veterinary importance are obligate parasites, i.e., they cannot survive off their hosts. A few mite species are bloodsuckers, but all scab and mite species are not. There are also thousands of mite species that are not even parasitic, other species parasitize plants.
Scab and mange mites of veterinary importance have a worldwide distribution but they tend to be more frequent in regions with cold climate a hard winters. Such mites live in the skin of their hosts. Infestations with mites are technically called acariasis.
Other mites, especially certain bird mites (e.g. the red fowl mite, Dermanyssus gallinae) do not live in the skin of the hosts but are bloodsuckers. They behave rather like soft ticks.
Mites affect all kinds of livestock end pets, as well as humans and wildlife. Mites are often quite species-specific, i.e. they are occur only on one type of host and a few closely related species, e.g. on canids such as dogs, wolves and foxes, but not on cats; or on cattle and buffaloes but not on sheep or goats, etc.
Anatomy of mites
Scab and mange mites are minuscule (0,15 a 0,8 mm) and not visible for the naked eye. Infestations are recognized by the symptoms and clinical signs they cause on livestock or pets. To determine the specific agent examination of skin scrappings under the microscope is often required.
Other mites such as fowl mites are slightly larger, especially engorged ones (up to 1 mm) and can be seen by the naked eye.
Anatomically, mites as well as ticks are substantially different from insects. They show no segmentation, i.e. their body is not divided into head, thorax and abdomen. They don't even have a proper head. Instead they have a series of mouthparts grouped into the so-called capitulum (also called false head or gnathosoma). These mouthparts are a pair of palps, a pair of chelicerae and the hypostoma. Scab and mange mites use their mouthparts to burrow under the skin of their hosts. Bloodsucking mites use their mouthparts to penetrate their host's skin and suck blood.
Instead of thorax and abdomen mites have just an abdomen (also called idiosoma). The abdomen contains all the major organs (digestive tract, reproductive organs, nervous system, etc.).Female mites are always larger than males.
As all arachnids, adults have 4 pairs of legs (larvae only 3), whereby those of scab and mange mites are often rudimentary.
Metamorphosis, life cycle and behavior of mites
All mites undergo a so-called metamorphosis, i.e. development to adults does not only require increasing the size, but also changing the shape. Due to the rather rigid exoskeleton, increasing the size is only possible through molting, i.e. getting rid of the old skin and producing a new and larger one. Mites (and most arthropods) go through four major development stages: egg, larva, nymph and adult. The passage from one stage to the next one requires one or more molts.
The complete life cycle (i.e.) from eggs to eggs of the next generation lasts 1 to 4 weeks, depending on the species and the environmental conditions. i.e., it is rather short when compared with ticks.
Scab and mange mites
Scab and mange mites live on the skin of their hosts and/or burrow tunnels in it. The saliva of many species can digest the skin proteins. They feed on skin debris, lymph or other body fluids resulting from their digestive activity or from exudations of the host's organisms as a reaction to the mites burrowing activity. Several mite species can also produce allergic reactions.
Scab and mange mites spend their whole life on the same host. This means that there are no developmental stages living free in the environment that actively spread the infestation to other hosts. Transmission to other hosts is by close contact among infested animals, but not in the sense that mites actively "jump" for one host to another. In fact, scab and mange mites do not jump. Transmission is passive, i.e. a few individuals (larvae, nymphs or adults) are passed to another host "by chance".
Scab and mange mites are typical winter pests in regions with a cold or moderate winter. And they affect mainly stabled livestock, because crowding creates a warm and humid microclimate that favors mite development and transmission.
Bloodsucking mites (mostly bird mites)
Bloodsucking mites do not burrow tunnels in the skin of their hosts but crawl on their surface and pierce the skin to get access to blood. Their blood meals last several hours. Some species, e.g. the red fowl mite, Dermanyssus gallinae, live off their hosts but in their close vicinity, hidden in cracks, crevices and hollow places, in the nests of birds. They visit their hosts only for bloodsucking. Each time a mite wants to suck blood it will search for a host that can be anyone in a poultry house. This means that transmission is through active infestation of other hosts because there are free-living, infective mites in the environment.
Other bloodsucking species, e.g. the northern fowl mite, Ornithonyssus sylviarum, spend their whole life on the host, but can easily change the host if their are very closely as it happens in most poultry houses.
Most bloodsucking mites are not that species-specific as scab and mange mites. Many such mite species can infect and survive on several bird species, also on wild birds. This means that wild birds are vectors of such mites and can transmit the infestation e.g. between poultry houses. Even rodents and other domestic and wild animals (e.g. dogs, cats, foxes, etc.) and even workers can be passive vectors and such mites in industrial bird production facilities.
Harm and damage to livestock, dogs and cats caused by mites
Scab and mange mites
The burrowing and skin digesting activity of scab and mange mites causes several clinical symptoms such as local inflammation of the skin that can become dry, reddened, crusty, blistered, cracked, etc. It is usually associated with more or less intense itching (pruritus). If the hair follicles are affected by the mites, hair loss (alopecia) can also occur. The host reacts to itching and inflammation with intense rubbing, scratching, and even biting of the affected parts. This can lead to additional hair loss and skin thickening resulting in the building of large crusts on the naked skin, and even in self mutilation, e.g. of the ears. Rubbing and biting can also produce injuries that become infected with secondary bacteria or attract other parasites such screwworm flies or blowflies that lay eggs on the wounds out of which develop various cutaneous myiases.
Scab and mange mites are particularly damaging for sheep and goats, especially the psoroptic mange mite (Psoroptes ovis). Heavy infestation can be live threatening. The stress caused by the infestations leads to loss o appetite, reduced weight gains and milk production, etc. For cattle and pig, mite infestations are usually not as harmful as for sheep.
Mite infestations are also frequent in dogs and cats, but usually are not perceived as that serious as flea or tick infestations. There is probably a significant psychological component: fleas bite the pet owners as well, and ticks can be seen and are disgusting. Mites are not visible to the naked eye and do not bite the pet owner...
Scab mites are seldom a problem in industrial poultry production facilities.
Most scab and mange mites do not play a significant role in the transmission of microbial diseases to livestock or pets.
Harm to birds by bloodsucking mites is comparable to that of ticks for large livestock. Besides stress and pain caused by itching and inflammation of the skin, blood loss can be considerable, which can cause anemia that can be fatal. Egg production can be substantially reduced.
Bloodsucking mites can be a very serious problem in industrial poultry production, especially in layer houses. Economic loss can be substantial. And the problem is aggravated because several mite species have become resistant to numerous acaricides and it is becoming more and more difficult to keep them under control.
In addition, most bloodsucking mites of birds transmit several microbial diseases.
Mite species of livestock and pets
Unless specified, all species occur worldwide. For specific information on the various mite species as well as for their control click the corresponding link.
- Demodex canis, affects dogs; canine follicular mange mite, red mange mite
- Demodex cati, affects cats; feline follicular mange mite
- Otodectes cynotis, affects mainly cats, seldom dogs; ear mite
- Notoedres cati, affects cats; feline scabies, cat mange mite
- Cheyletiella spp., affects mainly cats, occasionally dogs; walking dandruff
- Pneumonyssoides caninum, affects dogs; nasal mite
- Sarcoptes scabiei var. canis, affects dogs, canine scabies
- Demodex bovis, cattle follicle mite
- Chorioptes bovis, chorioptic mange mite
- Psoroptes ovis, cattle scab mite
- Sarcoptes scabiei var. bovis, itch mite, sarcoptic mange mite
- Chorioptes equi, itchy leg mite
- Demodex equi, horse follicle mite
- Psoroptes equi, horse scab mite
- Sarcoptes scabiei, var. equi, the common mange mite
- Chorioptes ovis, chorioptic mange mite
- Psorergates ovis, sheep itch mite
- Psoroptes ovis, sheep scab mite
- Sarcoptes scabiei var. ovis, itch mite, sarcoptic mange mite
- Demodex phylloides, pig follicle mite
- Sarcoptes scabiei var. suis, pig itch mite, sarcoptic mange
- Cnemidocoptes gallinae, depluming itch mite
- Cnemidocoptes mutans, scaly leg mite
- Dermanyssus gallinae, bloodsucking, red poultry mite, red chicken mite
- Epidermoptes bilobatus, scaly skin mite
- Ornithonyssus bursa, bloodsucking, tropical fowl mite; tropical and subtropical climate
- Ornithonyssus sylviarum, bloodsucking, northern fowl mite; moderate climate