The ectoparasites of zoological companion animals (birds, reptiles, and small mammals) are as diverse as their host species within this group. Ectoparasites are anecdotally less common in these zoological companion animals compared with dogs and cats, likely due to the indoor lifestyle of most of these species. However, several of these parasites can be transmitted outside of their host taxa to dogs, cats, and even humans. Therefore, veterinarians need to be aware of these ectoparasites and the treatment options. This article highlights some of the most common ectoparasites of zoological companion animals but is not an exhaustive discussion due to the diversity of species and their respective parasites. Reptiles Ophionyssus natricis, often called the common snake mite, and the lizard mite (Hirstiella spp.) are the most common mites of reptile species. They are ~1-2 mm and most often found between the scales around the eyes and facial folds (Figure 1). These mites have been hypothesized to transmit several bacteria and viruses within various reptiles.1 Clinical signs of infection include pruritus/excessive rubbing, dermatitis, and difficulty shedding (dysecdysis). Severe infestations, especially in smaller reptiles, can lead to severe anemia. Figure 1. Multiple mites present on the medial aspect of the frill from a juvenile frilled lizard (Chlamydosaurus kingii). Photo courtesy Dr. Olivia A. Petritz The mite’s lifecycle is long (approximately 40 days), and a significant portion of that is spent off the host in the environment, which complicates treatment. Insecticides, including ivermectin (parenterally or topically), topical sprays for the environment, or topical fipronil, have traditionally been used for treatment. It is important to remember ivermectin can cause fatal complications in chelonians, regardless of the route or dose, and should never be used in any turtle or tortoise. Predatory mites (Cheyletus eruditus) have also been successfully used to treat various reptile species.2 According to a recent publication, a single oral dose of afoxolaner (2.5 mg/kg) was 100 percent effective in eradicating Ophionyssus natricis infection in several species of snakes, without any additional environmental treatment.3 O. natricis mite is considered a zoonotic disease, and proper precautions should be taken by anyone who handles the infected reptile or its environment. Birds The most common ectoparasite of companion birds is Knemidocoptes pilae, also called the scaly leg mite, and the cause of “tassel foot” in canaries (Figure 2). It can infect many avian species, including passerines (finches and canaries), psittacines (parrots), and Galliformes (chickens and turkeys). Outside of budgerigars, this infection is rare in other parrot species. Figure 2. Excessive keratin buildup and overgrown nails of a canary infectedwith Knemidocoptes pilae. Photo courtesy Dr. Olivia A. Petritz Clinical signs of infection include hyperkeratosis and crusting of the cere, beak, legs, and feet. These signs are considered pathognomonic, but microscopic examination of skin scrapes can be performed for definitive diagnosis. The most common treatment is ivermectin, either applied topically, orally, or parenterally for one to three treatments. Most commercially available ivermectin formulations will need to be diluted prior to administration in small birds. Topical fipronil has also been used for treatment, but a recent study found topical ivermectin resulted in a faster resolution of clinical signs compared with fipronil in budgerigars.4 Small mammals Rabbits Cheyletiella parasitovorax, or the “walking dandruff” mite, is a common ectoparasite in pet rabbits. Clinical signs include a mild pruritus, alopecia, or uncommonly, oily dermatitis. Young, obese, and immunosuppressed rabbits are predisposed. It is important to note this mite can also infect domestic dogs and cats, which can complicate treatment if those animals are also present in the rabbit’s home. The diagnosis is based on tape preparation and microscopy. The mite life cycle is 21-28 days; therefore, it is recommended rabbits be treated for at least four weeks. Ivermectin or selamectin are common treatments, and the environment and bedding should be changed frequently. This mite is also considered zoonotic, and the owners should be notified to take proper precautions if their rabbit is infected. As there are no pre-formulated tubes of selamectin for rabbits or any small mammal, individual doses must be calculated and appropriate volumes removed from the pre-dosed tubes for small dogs or cats. The rabbit ear mite, Psoroptes cuniculi, typically causes severe crusting of the external ear canal and pinna. Cleaning and/or removing of the crusts is not recommended, due to the extreme pain of such a procedure. Treatment with three doses of topical imidacloprid/moxidectin 30 days apart, or two doses of selamectin 28 days apart, have both proven to be effective in rabbits. A recent paper also described the use of a single oral dose of fluralaner (25 mg/kg) as an effective treatment for rabbit ear mites.5 Similar to most mammals, rabbits can also be infected with fleas (Ctenocephalides spp.), especially if they share a household with an infected dog or cat, or if they are housed outdoors. Topical imidacloprid 10-16 mg/kg every 30 days, or selamectin 20 mg/kg every seven days, are both effective flea treatments in this species. It is imperative clinicians never use fipronil on rabbits as it can lead to seizures and death in this species. Ferrets Ferrets can also become infested with fleas (Ctenocephalides felis or C. canis), especially if housed with these species. Treatment and options are like those in domestic cats, and topical selamectin is commonly used. Imidacloprid is also effective and has recently been labeled specifically for ferrets in the United States. Treatment of other infected animals in the house and environmental eradication is imperative to preclude reinfection. In the author’s experience, ear mites (Otodectes cynotis) are more common than flea infections in indoor-housed pet ferrets. These are often asymptomatic infections, with excessive brown, ceruminous ear debris as the main clinical exam finding. Mites can be diagnosed via microscopic examination of otic swabs, and treatment options are similar to those described for fleas in this species. Guinea pigs Guinea pigs can be affected by several different species of mites, including Trixacarus caviae, Sarcoptes scabiei, Cheyletiella parasitovorax, and others. Of those, T. caviae is the most commonly diagnosed and can lead to significant crusting of the skin globally (Figure 3). Affected animals often have intense pruritus, which can be mistaken for seizures. Infections are more common in younger animals. Figure 3. Severe infection with Trixacarus caviae in an adult guinea pig with significant crusting and pruritis. Photo courtesy Dr. Olivia A. Petritz A previous paper compared topical selamectin vs. injectable ivermectin for treatment of 17 guinea pigs infected with T. caviae—either a single topical dose of selamectin (15 mg/kg) or ivermectin (400 μg/kg SQ every 10 days for four injections) was administered to the animals.6 Periodic skin scrapings were evaluated for both groups for 60 days. The authors found no differences in efficacy between the two treatments; however, topical administration of selamectin is the most common treatment for this condition in guinea pigs. African pygmy hedgehogs The psoroptid mite Caparinia tripilis is the most common ectoparasite of captive hedgehogs, often found on the head and neck region. Clinical signs of infection include spine loss, scaling of the underlying dermis, and pruritus (Figure 4). Figure 4. An African pygmy hedgehog infected with C. tripilis presents with spine loss and crusting along the dorsum. Photo courtesy Dr. Olivia A. Petritz Diagnosis includes a microscopic examination of a skin scrape, which should be performed carefully due to the thin nature of the skin along the dorsum between the spines. Some clinicians recommend the use of toothbrushes or cotton tip applicators to collect samples of the affected dermis and/or crusts. All these techniques can be utilized even with the animal curled into a ball with limited access to their head. Interestingly, many of these infestations develop in solitarily housed animals without an obvious source of infection. Topical selamectin (20-30 mg/kg topically every 21-28 days for two to three doses) is the most common treatment used in the author’s practice, but other topical and oral antiparasitic medications have been reported.7 Ectoparasites are less common in zoological companion animals compared with dogs and cats but are still important to rule out as a differential for animals presenting with dermatologic disease. Several of these ectoparasites are zoonotic, including snake mites in reptiles and Cheyletiella in small mammals. Owners of these infected animals should be notified, and proper precautions should be taken to prevent human transmission. While many of the treatments for ectoparasites are similar to those used in domestic mammals, some notable exceptions should be strictly avoided due to potentially fatal consequences, including the use of ivermectin in chelonians and fipronil in rabbits. Olivia A. Petritz, DVM, DACZM, graduated from Purdue University, and then completed several internships and a residency in the field of zoo and exotic animal medicine. Dr. Petritz became a diplomate in the American College of Zoological Medicine in 2013, specializing in zoological companion animals (exotic pets). Petritz started an exotics service at a specialty hospital in Los Angeles, Calif. following her residency and is currently an associate professor of avian and exotic animal medicine at North Carolina State University. References Aguilar, Graciela, and Mark A. Mitchell. “Reptile Dermatology.” Veterinary Clinics: Exotic Animal Practice 26.2 (2023): 409-424. Schilliger, Lionel H., et al. “Cheyletus eruditus (Taurrus®): An effective candidate for the biological control of the snake mite (Ophionyssus natricis).” Journal of Zoo and Wildlife Medicine 44.3 (2013): 654-659. Mendoza-Roldan, Jairo Alfonso, et al. “Afoxolaner (NexGard®) in pet snakes for the treatment and control of Ophionyssus natricis (Mesostigmata: Macronyssidae).” Parasites & Vectors 16.1 (2023): 6 Akhtar, Serug, et al. “Comparative efficacy of ivermectin and fipronil spot on against Knemidocoptes pilae in budgerigars.” Indian Journal of Animal Research 55.1 (2021): 105-108. Sheinberg G, Romero C, Heredia R, et al. Use of oral fluralaner for the treatment of Psoroptes cuniculi in 15 naturally infested rabbits. Vet Dermatol 2017;28:393–395.1. Eshar, David, and Tali Bdolah-Abram. “Comparison of efficacy, safety, and convenience of selamectin versus ivermectin for treatment of Trixacarus caviae mange in pet guinea pigs (Cavia porcellus).” Journal of the American Veterinary Medical Association 241.8 (2012): 1056-1058. Doss, Grayson A. "Dermatologic diseases of four-toed hedgehogs." Vet Clin North Am Exot Anim Pract 26.2 (2023): 443-53.
