Notoedric mange (feline scabies)

Notoedric mange, also known as feline scabies, is a parasitic, contagious dermatological disease of the cat caused by Notoedres cati. This mite may exceptionally infest other mammals, humans included. The disease is considered rare in most European countries, while it is still common in some areas of Italy, Switzerland, Spain, Slovenia and Croatia, where it can be endemic and epizoic.

MORPHOLOGY AND BIOLOGICAL LIFE CYCLE OF THE PARASITE

Notoedres cati is a 225-250 μm longmite with a nearly circular shape. The rostrum is short and square. The limbs are also short and the two pairs of front limbs, with non-jointed pretarsi, bear a sucker-like structure (pulvillus) at the end. The rear limbs are rudimentary, do not extend beyond the body of the parasite and, in both sexes, carry long bristles without pulvilli. The cuticle of the dorsal surface has concentric, “fingerprint-like” striae, as well as rounded scales imbricated in transverse rows and simple, non-spiny bristles. The anal opening is located dorsally (Fig. 1).

The entire life cycle (14-21 days) of the parasite is carried out on the host, with the mite living in the more superficial layers of the epidermis. The female digs burrows between the keratinocytes of the stratum corneum of the epidermis; she feeds on epidermal debris and tissue fluids and lays two or three eggs a day.

Notoedric mange is an extremely contagious disease and since transmission is by direct contact community life (in shelters, breeding centres) increases the risk of transmission. In favourable conditions the mites may survive in the environment for a few days, hence contagion, although rarely, may also take place via indirect transmission.

CLINICAL SIGNS

The distribution of lesions is quite characteristic: in the initial stages lesions are found on the margin of the pinna, then rapidly extend and involve the skin of the entire pinna (Figs. 2, 3, 4). Other initially involved sites are the face, muzzle and neck. The common grooming behaviour of cats and their habit of sleeping curled up favours the spread of the lesions to the limbs and  to the perineal region (Fig. 5). Initial lesions consist in crusted papulae and scales which, with the progression of the disease, are often substituted by thick, yellowish-grey scabs that adhere firmly to the skin, covering the skin of the pinnae, head and neck and causing the characteristic wrinkled, pleated look (Figs. 6, 7, 8, 9). Pruritus is usually intense and lesions secondary to self-mutilation are, therefore, frequent (alopecia, erosions and ulcerations) (Fig. 10). In non-treated subjects and especially in those immunodepressed because of feline immunodeficiency virus or feline leukaemia virus infection, the lesions often become widespread over the entire body of the patient (Fig. 11).

DIAGNOSIS

The diagnosis of notoedric mange is made by identifying the parasites, their eggs or dejecta under the microscope; dejecta can be recognized from their rounded-oval shape and their dark brown colour.

The technique of choice to collect the material to be examined under the microscope is a superficial skin scraping which, in the case of notoedric mange, and differently from sarcoptic mange, always contains a high number or mites (Figs. 12 and 13).

DIFFERENTIAL DIAGNOSIS

• Other ectoparasitoses
• Atopic dermatitis
• Adverse reaction to food
• Flea bite allergy dermatitis (FAD)
• Dermatophytosis
• Pemphigus foliaceus

THERAPY

No compound is currently registered for the treatment of notoedric mange in the cat; very good results have been obtained using compounds with acaricidal activity, applied both topically (amitraz solution 0.025%, by sponging twice a week for 3 weeks) and systemically, such as spot-on selamectin (two treatments, 1 month apart), injectable ivermectin (two administrations of 0.4 mg/kg s.c. at a 15-day interval) and injectable doramectin (a single administration of 0.2-0.3 mg/kg s.c.).

Suggested readings

1. Albanese F, Leone F. Manuale pratico di parassitologia cutanea del cane e del gatto. Ed. Pfizer 2007.
2. Bowmann DD. Notoedres. In Georgi’s Parasitology for Veterinarians, 8^th edn. Saunders St. Louis, 2003; 64-5.
3. Delucchi L, Castro E. Use of doramectin for treatment of notoedric mange in five cats. J Am Vet Med Assoc 2000; 216(2): 215-6.
4. Fisher MA, Shanks DJ. A rewiew of the off-label use of selamectin (Stronghold/Revolution) in dogs and cats. Acta Vet Scand 2008; 50:46.
5. Foley RH. A notoedric mange epizootic in an island’s cat population. Feline Pract 1991; 19:8-10.
6. Genchi M, Traldi G, Genchi C. Notoedres cati. In Manuale di Parassitologia Veterinaria. Casa Editrice Ambrosiana, Milano 2010; 132-3
7. Gross TL et al. Feline Notoedric acariasis. In Gross TL, Ihrke PJ, Walder EJ, Affolter V. Skin disease of the dog and cat. Clinical and histopathologic diagnosis. 2^nd ed. London, Blackwell Science, 2005; 219-20
8. Guaguère E. Notoedric mange. In Guaguère E, Prelaud P. A Pratical Guide to Feline Dermatology. Ed. Merial, Milan 2000; 3:1.
9.  Itoh N et al. Treatment of Notoedric cati infestation in cats with selamectin, Vet Rec 2004; 154(13):409
10. Leone F, Albanese F, Fileccia I. La gale notoédrique du chat: à propos de 22 cas. Prat Mèd Chir Anim Comp 2003 ; 38 :421-7
11. Leone F, Albanese F, Fileccia I. Epidemiological and clinical finding of notoedric mange in 30 cats. Vet Dermatol 2005; 16(5):359.
12. Leone F. Canine notoedric mange. Vet Dermatol 2007; 18(2):127-9.
13. Page SW. Antiparasitic drugs. In Maddison JE, Page SW, Churh DB. Small Animal Clinical Pharmacology. second edition, Saunders Elsevier 2008; 198-260.
14. Scott DW, Miller WH, Griffin CE. Notoedric mange. In: Muller and Kirk’s Small Animal Dermatology, 6^th edn. WB Saunders Company, Philadelphia 2001: 483-4.
15. TaylorMA, Coop RL, Wall RL. Notoedres cati. In Parassitologia e Malattie Parassitarie degli Animali. EMSI, Roma 2010; 449-50.
16. Wall R, Shearer D. Notoedres. In Veterinary Ectoparasites: biology, pathology & control. Second edition, Blackwell Science, Oxford 2001; 33-4.