|Guide to Health and Hygiene in Agricultural Work (ILO, 1979, 328 p.)|
|4. Occupational diseases in agriculture|
|4.4. Pathology due to snake bites and insect, spider and scorpion stings|
Scorpions are arthropods. They range from 2 to 20 cm in length, and the glands that produce their poison are in the terminal segment. At the end of the tail is a sting by which the poison is injected into the victim. Scorpions do not attack human beings; stings are due to accidental contact.
The majority of scorpions make a non-lethal poison that gives rise only to a pronounced local reaction. In the poison of some species of North African scorpions, two proteins have been found (the scorpamines). Their action is purely neurotoxic and, all other things being equal, they are more toxic than snake venom; however, the quantity injected by the scorpion is much smaller.
The poison of the lethal species of scorpions has an elective action on the nervous system. The fatality rate due to scorpion stings is much higher among children and old people (among children under five years of age it amounts to between 1 and 2 per cent) than among adults.
Pain sets in at the wound and there is a burning sensation. If the sting comes from Centruroide sculpturatus or Centruroide getschi, there is also local hyperaesthesia.
Stings from species with a lethal poison produce general symptoms as a result of their neurotoxic action; this makes itself felt quickly and lasts from 4 to 48 hours and sometimes longer. The victim is agitated, he weeps, his nose runs, he vomits and he suffers from epigastric pains, heightened abdominal sensitivity, fever, profuse sweating and shock.
The convulsions that occur are of the tonic type. They are accompanied by trismus and other muscular spasms. Generalised spasms of the flexor and the extensor muscles cause alternating postures. There are also difficulties in speaking, swallowing, breathing and making movements. In addition, the tongue feels thick and there are mydriasis, diplopia, temporary loss of sight and sphincteric incontinence.
The convulsions resemble those produced by strychnine poisoning, and they may be fatal if they are not treated in time.
Cardiovascular symptoms also occur, including increased heart irate, disturbances of rhythm and very weak pulse. The electrocardiogram shows evidence of myocarditis. Death may ensue from acute pulmonary oedema.
Local treatment consists in applying a tourniquet in order to delay the absorption of poison. It should be loosened every five to ten minutes. An ice-bag can be applied to the wound for at least two hours (the ice must not be applied directly to the skin), again in order to delay absorption.
The pain can be reduced by a local injection of a solution of procaine and adrenaline. Morphine and substances related to it are contra-indicated, as it has been demonstrated that they have a synergistic effect on the activity of the poison and that this effect is proportional to the dose.
Breathing may be improved by oxygen therapy.
The most promising treatment, however, is to administer the immune serum. If no specific antidote is available, one for a related species can be used.
If no immune serum at all is available recourse should be had to local and symptomatic treatment.
Prophylaxis consists essentially in educating the population to avoid infested areas, inspect bedding before retiring and shake clothes and footwear before putting them on.
Prevention also consists in making the house vermin-proof, destroying weeds and removing stones and other objects round about the house. Insecticides such as kerosene and chlordane can be used to spray the surroundings of houses and workplaces.