Page 177 - LECTURE NOTES

ª By causing direct, non-allergic, local tissue damage through stings, bites,

exposure of toxic body fluid (blister beetles), and tissue invasion (sand flea and
brown recluse spider).

ª By causing allergic reactions to their secretions, skins, or scales.
ª By producing systemic toxicity, such as that caused by neurotoxin release (black

widow spider and scorpions).
ª By transmitting diseases.

7.12.7.1 Scabies

Scabies is one of such arthropod associated diseases by the mite, Sarcoptes scabei

varhominis, and characterized by marked itching.

Scabies is a contagious complaint, which is transmitted only by close contact. It is

therefore a family disease spreading amongst those living in close association,
especially when they sleep together in the same bed.

7.12.7.2 Prevention and control of scabies

All cases of scabies can be cured; there are no resistant infections. Methods aimed at
killing the mites will do little to immediately alleviate the nuisance and irritation caused

by the rash, although this will eventually disappear. Separate medical treatment
however, may be necessary especially if secondary infections have become

established. In the past, a common procedure was to give the patient a hot bath and a

vigorous scrubbing with a brush until the patient bled, but this is not very effective at
either removing or killing the mites. However, as many but certainly not all, patients with

scabies are dirty, an ordinary bath before treatment may be advisable for general
hygienic reasons. However, if large numbers of patients suffering from scabies are to be

treated, such as in epidemic situations, bathing may not be practical.

Decreasing the humidity in rooms, improving ventilation and removing dust can control
mites and associated fungi. Bedrooms and living rooms should be aired regularly, or

other measures should be taken to reduce dampness. The shaking of bedclothes and

frequent washing of sheets and blankets reduces the availability of food and therefore

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