Scabies

General Knowledge

Scabies

Chulalongkorn University

“Scabies” is an infectious skin disease which is common among children in urban communities. In some countries, scabies is significant health problem that its prevalence may be up to 300 million worldwide. Its manifestation is recorded as old as 2,500 years ago. In 1687 it is discovered that scabies is caused by a species of insect by Gio van Cosimo Bonomo, and Italian Physician.

 

What cause scabies?

                Scabies is a species of insect which is in the same group as mites scientifically named “Sarcoptes Scabiei”. It’s a human parasite. It is brown and has 4 pairs of legs and very small in size which makes it unseen by naked eye. It lifecycle starts with after being inoculated with an adult female scabies which holds eggs, the insect will find an appropriate habitat and dig the skin to form a burrow then lay eggs there 2-3 eggs a day. This female scabies will continue digging at the rate of 2-3 mm a day to create a serpentine burrow. This digging only involves the epidermis. The eggs laying period lasts around 1-2 months. Eggs are around 0.1-0.15 mm in size and take 3-4 days to develop into adults which are sized 0.25-0.35 mm for a male and 0.30-0.45 mm for a female. The male adult will climb of its hole into the female’s to mate. After mating, the male adult dies and the female will get out of the hole to find another appropriate place to dig the burrow and lay eggs again.

 

                                    

Is it contagious?

 

                Scabies can spread from human to other human by direct contact. Unlike the fleas, scabies can’t jump. If the insect is without its host, it can only live for another 2-3 days unless the environmental temperature is less than 20 degrees Celcius, which makes it lives longer. In normal affected individual, 5-15 unit of scabies are found. However, the immunocompromised may host up to millions of these insects.

And It’s Symptoms?

 

                The infected may present with maculopapular rash, purulent lesions, or lichenification which is caused by scratching. Lesions are shown as curved elevated lesions with lengths of 5-15 mm which is caused by burrow digging which is specific to scabies. The involved areas are usually the warmer ones such as skinny area bridging the fingers and the toes, the folded side of elbows and knees, around and below the nipples, waist, palm of hand, sole of foot, groin, and genital skins which larger and more severe lesion(and took slower to heal) occurs. In children, the affected areas can also be face, head and both palm of hand and sole of feet. More importantly, the itching will be more severe especially during the night. The itching is caused by hypersensitivity to the female scabies, its eggs and its feces. Among some infected patients such as the immunocompromised, neurologically disabled, nutritional deficits or cancer patients, the lesion may appear in the whole body and become crusted known as “Norwegian scabies” which is different to normal scabies.

           

Picture of a scabies patient with distince lesion around the wrist(Courtesy of Kenneth E. Greer, MD.)

              

The lesion appears to be elevated curved like a short string which is specific to scabies             

             

Rash at the back found in children. Consulting a physician for differential diagnosis is needed.  (Courtesy of Kenneth E. Greer, MD.)

            

      “Norwegian scabies” The lesion is found all over the body in some group of patients. (Courtesy of Kenneth E. Greer, MD.)

What to do if you suspect scabies?

 

If you found above symptoms, consulting a physician is advised for correct diagnosis and treatment. There, the physician will take the history, check at the symptoms and the lesion. In some cases, laboratory examination is needed in order to differential diagnosis with other skin disease such as dermatitis, urticaria and lice infection. When the diagnosis of scabies is confirmed, treatment will be administered. As scabies is an ectoparasite, the treatment with local application of drugs are effective. However, the application of drugs must be done at the whole body with head and face sparing, not only at the lesion. For children age under 3, the facial and neck administration is also needed. However, the drug may be irritable and the sulfur in the drug’s odor is quite strong so facial application in adults should not be done. Oral drugs may be administered in some severe patients such as the elderly, the immunocompromised or the one with thick lesion which the local drugs may not fully function or patients with contraindication to local drugs. However, as the itching is caused by host’s own immune system, the itching may continue to occur 2-4 weeks after the treatment. Patients should follow physicians’ instructions properly for not only their own sake but in order to prevent scabies from infecting others.

How to protect yourself from scabies?

1.       If you’re infected, you have to bring your close ones to the physician’s for treatment at the same time

2.       Eliminate remaining scabies in your environment that can directly contact your skin such as clothes, bed mats, towels by 3 days before treatment. You can do this by washing and filling it with water temperature at least 60 degree Celcius for 20-30 minutes. For objects that can’t be washed, you have to cover it with tightly closed plastic bag for at least 72 hours for the scabies to die. For large objects, vacuums can be used.

 

3.       Avoid direct contact with patients. If needed, use gloves to contact with itchy patients with scabies or unknown cause.

Conclusion

 

Scabies is still a health problem in Thailand. It is an easily contagious disease but easily preventable and treatable as well. Clinically, some patient has delayed diagnosis and treatment because lack of knowledge and understanding of the disease. To prevent this, spreading knowledge to communities is an important solution in decreasing contagibility and disease control.

References

Burkhart, CG. Recent immunologic considerations regarding the itch and treatment of scabies. Dermatology Online Journal; 12(7): 7. 13 Feb. 2009 < http://dermatology.cdlib.org/127/commentary/scabies/burkhart.html>.

Karthikeyan K. Scabies in children. Arch Dis Child Educ Pract 2007; 92: 65-9.

Arlian, L. Biology, Host Relations and Epidemiology of Sarcoptes Scabiei. Ann. Rev. Entomol 1989; 34:139-61. 5 Feb. 2009 <http://arjournals.annualreviews.org/doi/pdf/10.1146/annurev.en.34.010189.001035?cookieSet=1>

Strong M, Johnstone PW. Interventions for treating scabies. Cochrane Database of Syst Rev. 2007; 3: CD000320.

http://emedicine.medscape.com/article/1109204

Photo:     http://www.inderm.go.th/inderm_sai/skin/skin41.html

Courtesy of Kenneth E. Greer, MD.:http://en.wikipedia.org/wiki/Sarcoptes_scabiei

Department of parasite : Faculty of medicine Chulalongkorn memorial hospital.