Identifying common parasitic mites

Photo: Evgenia Glinskaya/Adobe Stock

A dog's ear is affected by mites.

Richard Gerhold, DVM, MS, PhD, DACVM, associate professor of parasitology at the University of Tennessee’s College of Veterinary Medicine in Knoxville, provided attendees with an overview of common parasitic mites, how to identify them, and how to manage them, during his session, “Itchy Animals & Ectoparasites,” presented at the 2024 Fetch dvm360 Conference in Atlantic City, New Jersey.

Generally, mites are diagnosed empirically, through their collection and direct identification. They are commonly collected through hair combs, brushes or skin scrapes, depending on what mites are suspected to be present. Diagnostics can also turn to skin biopsies or analysis of fecal samples. The best way to preserve a mite, once found, is to place it in 70% alcohol, to later be sent off to a lab for identification, Gerhold noted.

Family Trombiculidae

“So, this first [mite] is probably one of the itchiest ones that I’ve ever had,” Gerhold said. “Hopefully, no one else has had the unloving privilege of having chiggers, but if you have, you know what I’m talking about.”

Commonly known as chiggers or harvest mites, the adults and nymphs are free-living, and the larvae are ectoparasitic on mammals, Aves, reptiles, and amphibians. Gerhold explained that chiggers firmly attach to their hosts, digesting a long and narrow tunnel down through the dermis. He went on to describe the small orange and red dots that appear throughout the area affected by chiggers, because of the skin’s reaction to the saliva material that they secrete.

“So, they attach, and they produce this kind of cement material that causes this severe itching,” he said. “They’re usually transient on [humans], but they do cause that real severe itching, particularly on areas of tight clothing.” There are not many known treatment methods, but Gerhold recommended the use of lime sulfur dips.

Sarcoptes scabiei

Also known as sarcoptic mange mite, Gerhold explains that this is studied in several species, although it is not seen in cats. This parasitic mite causes scabies in humans and can result in a severe red reaction. Gerhold likens S scabiei to Giardia and Cryptosporidium, in the way that there are specific sarcoptic serovars depending on the host species.

“Cattle have their own, horses have their own, sheep have their own,” he said. “So, most are pretty host specific, [but] a canine variety can cause a transient dermatitis on humans.”

The diagnostic process for S scabiei starts with a deep skin scrape, that should show blood. Adults are oval-shaped with rounded short-mouthparts, tarsal suckers on long, un-jointed pedicels, and they often burrow into the skin to carry out their life cycle. Larvae and nymphs are present closer to the surface of the skin and are transmitted to other hosts through either contact or potential fomites, Gerhold noted.

They are typically found where the hair coat is thin, and skin is tender (ie, elbows or ears). For treatment of S scabiei, Gerhold recommended selamectin, isoxazolines, ivermectin, milbemycin oxime, or fipronil spray.

Notoedres cati

Commonly found in cats and rabbits, N cati is rarely seen in dogs or humans. In impacted adults, it can closely resemble S scabiei, although they do not have the dorsal spines that S scabiei have and they are smaller and rounder in shape. N cati burrow into the skin, starting at the tips of the ears, spreading to the face, head, and paws. They are commonly transmitted through direct contact, and they are relatively easy to find, according to Gerhold.

There are no approved drugs for the treatment of N cati, although there are options that are both topical and systemic. Similarly to S scabiei, Gerhold recommended the use of selamectin, moxidectin, ivermectin, or lime sulfur dips.

Psoroptes cuniculi

Primarily a parasite of rabbits, it has been recently recorded in alpacas, goats, and horses, as well. P cuniculi are ear mites, resulting in severe scabbing of the ears. They have long, sharp mouthparts, their third and fourth legs extend beyond their body margin, and their tarsal suckers are on long, jointed pedicels—that joint in the pedicel helps distinguish them from S scabiei. Gerhold advised treatment with ivermectin, and advises against cleaning the ears, and against the use of over-the-counter spot-ons, most dips, collars, and all natural flea products.

Psoroptes ovis

A parasite primarily impacting sheep, P ovis is reportable to the state veterinarian’s office and federal veterinarian in the Animal Disease Eradication Division of the USDA. Identification of this parasite warrants quarantine. It can cause chunks of wool and flesh to exfoliate, and a secondary bacterial infection is often deadly to sheep populations.

Chorioptes bovis

Mostly found in cattle, it also causes chorioptic mange in sheep, goats, horses, and rabbits, and recognized as foot, leg, tail, and scrotal mange. The quality of semen in infected animals is notably worse, and it is noted to increase testicular temperature. The mites themselves have long legs, large tarsal suckers on short, unjointed pedicels, and they are compressed laterally.

Otodectes cynotis

Commonly known as ear mites, O cynotis impacts dogs and cats, but is more common in cats. It is extremely contagious, often through direct contact. In physical examinations, brown debris in ears, reports of ear scratching, head shaking, or circling and tilting the head should all be red flags of O cynotis. Gerhold advises the administration of selamectin and moxidectin in both affected animals, and just those in close contact. Approved ivermectin and milbemycin formulations have also shown positive results in cats, and ear cleansing with an appropriate cerumenolytic agent is also advised.

“You want to make sure you’re treating both the affected animals, as well as any in-contact animals for [O cynotis],” Gerhold said. “You also want to get rid of that wax in the ear as well, because that’s going to be a great hiding place for them and their eggs.”

Reference

Gerhold R. Itchy Animals & Ectoparasites. Presented at: Fetch dvm360 Conference; October 14-16, 2024; Atlantic City, NJ.