Question about Crusted (Norwegian) Scabies


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What's the difference between Norwegian scabies and regular scabies? If I simply walked into the room of a patient with Norwegian scabies, but did not have direct contact with the patient or anything in their room, what's my risk of becoming infected?

Norwegian scabies was initially described, shockingly enough, in Norway. The first case was reported by Danielssen and Boeck in 1848, who believed the disease to be a variant of leprosy. Hebra reported a similar case in 1851, correctly attributed it to the scabies mite, and named the disease "scabies norvegic Boeckii."

The truth is, the main difference between Norwegian scabies and regular scabies is simply the number of mites present on an infected person. In regular scabies, the number of mites on a host at any one time is, on average, 10 to 15 (with a range of 3-50). Persons with Norwegian scabies, on the other hand, will have thousands to millions of mites. Consequently, their skin manifestations are much more severe, with thick, hyperkeratotic crusts that can occur on almost any area of the body.

The type of mite in both presentations is exactly the same. The difference lies with the host, with those developing Norwegian scabies usually having a compromised immune system. Indeed, a normal host who acquires scabies from a patient with Norwegian scabies will develop only a usual case of scabies.

Clinically, Norwegian scabies differs from regular scabies in two ways: 1. it presents with more severe skin manifestations, and 2. it is usually not very pruritic. The decreased pruritis observed in Norwegian scabies is a bit counterintuitive, but probably reflects the idea that the pruritis in scabies is due to the host's immune response (and this response is muted in patient's with Norwegian scabies, which is why the infection progressed to that point in the first place).

Since Sarcoptes scabei are not able to jump or fly, the only way to acquire the infection is by direct contact with an infected patient or by contact with infected linens, clothing, or furniture. If someone was in the room of a patient with Norwegian scabies and really did not touch the patient or anything else in the room, it is unlikely that person will develop scabies. However, if they touched anything at all, there is a substantial risk of infection. Because patients with Norwegian scabies have such a tremendous parasite burden, they are very infectious. Indeed, one report by Hsueh et al found that 29 of 50 direct and indirect contacts of a patient with Norwegian scabies acquired scabies. Consequently, in order to minimize the chances of a scabies outbreak, the threshhold for prophylactic scabicidal treatment for hospital personnel exposed to a patient with Norwegian scabies should be low.

Interestingly, the incubation period from time of infection to time of symptoms in a normal host is much shorter when one gets infected from a patient with Norwegian scabies than from a patient with regular scabies (10-14 days vs 4-6 weeks). While I was not able to find any explanation for this finding in the literature, I presume it is somehow related to the larger initial parasite burden people become infected with after contact with a patient with Norwegian scabies.

References

Haag ML et al. Attack of the scabies: What to do when an outbreak occurs. Geriatrics 1993;48(10):45-53.

Hsueh P et al. Nosocomial outbreak of scabies. J. Formosan Med Assoc 1992;91:228-32.

Kolar KA and Rapini RP. Crusted (Norwegian) Scabies. Amer Fam Phys 1991;44(4):1317-21.

Sterling GB et al. Scabies. Amer Fam Phys 1992;46(4):1237-41.

Sweitzer SE and Winer LH. Norwegian scabies. Arch Dermatol Syphilol 1941;43:678-81

PHOTO

   

crusted appearance on hands

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Note:  This information not meant to replace your physician and is simply provided as a free educational service to all our visitors. If you feel that you have a skin problem, please see your doctor. 

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