On-line version ISSN 1678-9199
J. Venom. Anim. Toxins incl. Trop. Dis vol.9 no.1 Botucatu 2003
Epidemiological study of scorpion stings in Saudi Arabia between 1993 and 1997
M. K. Al-Sadoon; B. M. Jarrar
Department of Zoology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
This investigation evaluated the epidemiological aspects of scorpion stings in different areas of Saudi Arabia. A total of 72,168 cases of scorpion stings recorded in Ministry of Health Medical Centers in 11 selected areas of Saudi Arabia were analyzed based on area, age, sex, time of sting, sting site, treatment outcome, time of year, and scorpion species. Stings occurred throughout the year; the highest frequency was in June (15.08%), the lowest in February (2.52%). Most patients were male (61.8%); the majority of which were more than 15 years old (65.4%). Nocturnal envenomation (47.74%) was more common than diurnal (43.91%); most stings were in exposed limbs (90.95%), mainly in the lower limbs (63%). Most envenomings were mild (74.48%) and all evolved to cure, except for one death. Envenomation was characterized by local pain, erythema, headache, vomiting, and anxiety. This study found that the Leiurus quinquestriatus (Ehrenberg 1828), Androctonus crassicauda (Olivier 1807), and Apistobuthus pterygocercus (Finnegan 1807) were responsible for most of the stings, indicating their medical importance in Saudi Arabia. The study shows low threat to life despite the high number of stings; this is a result of the availability of medical facilities and the multi-center antivenom use in different areas of Saudi Arabia.
Keywords: scorpion envenomation, epidemiology, Saudi Arabia.
Scorpion envenomation is a medical problem and a real threat in many parts of the world. Considerable epidemiological studies on scorpion stings have been performed in several countries, such as Morocco (19), Tunisia (10), Algeria (22), Iran (17), Brazil (13), and Mexico (21). Information about scorpion envenomation in Saudi Arabia is scarce and fragmentary (1,4,5,7,11,14,16) and very little is known about the rate of scorpion stings in different areas of the Kingdom.
In this study, the risk of scorpion envenomation was evaluated in different areas of Saudi Arabia over a five-year period between January 1993 and November 1997.
MATERIALS AND METHODS
The incidence and frequency of scorpion stings in different areas of Saudi Arabia were reviewed over a five-year period beginning in 1993. Data were collected from records of Ministry of Health Medical Centers in the following areas: Riyadh, Qasieum, Al-Madina Al-Munawara, the Eastern Province, Najran, Hail, Qurayat, Baha, Bisha, Hafr Al-Batin, and Jazan. Information was analyzed on the following basis: area, age, sex, time of sting (month and time of day), sting sites, scorpion species, and treatment outcome. A considerable number of scorpion stings went unreported with no medical treatment of any kind.
Rate and distribution of stings. The total number of scorpion stings in the eleven selected areas of Saudi Arabia between 1993 and 1997 was 72,168. Table 1 shows that the highest rate of scorpion stings was in Al-Madina Al-Munawara with 24,053 recorded cases (33.33%) followed by Baha area with 11,058 cases (15.32%); the lowest number of cases was in Hafr Al-Batin area with 1,844 cases (2.56%).
|Table 1. Rate and relative frequency of scorpion stings in 11 regions of Saudi Arabia between 1993 and 1997.|
Distribution of stings throughout the year. Monthly sting incidence peaked from May to October. The highest rate of scorpion stings was in June; the lowest rate was in February.
Table 2 shows that spring (March and April) and autumn months (October and November) showed a similar rates; December through April accounted for only 12.8% of total stings.
|Table 2. Distribution of scorpion stings in Saudi Arabia between 1993 and 1997.|
Distribution of stings according to sex. Male-female sting ratio was 44,590 (61.79%) and 27,578 (38.21%), respectively; males exceeded females in all months throughout the study period. The highest male sting rate was in June (6,731 cases); the lowest in February (1,125). The highest and lowest female rates were recorded in the same two months, June and February, with 4,150 and 693 cases, respectively.
Distribution of stings according to age. The highest sting rates were in the over fifteens with 44,923 recorded cases (65.46%). Stings in under fives were 6.6%, those in 5 to 15 years old were 18,529 cases (27.94%)
Time of stings. Sting rates were higher at night for all months of the year, except for March, July, and October where the day stings were slightly higher. There were 34,456 nocturnal cases (47.74%), 31,689 diurnal (43.91%), and 6,023 (8.35%) others. Data analysis showed that the highest nocturnal stings were recorded in the summer months of May-September (Table 3).
|Table 3. Time of scorpion stings in Saudi Arabia between 1993 and 1997.|
Sting sites. Most stings were on the exposed areas of the limbs, with 40,831 stings (56.58%) in the lower limbs and 21,604 (29.9%) in the upper limbs. There were 1,312 cases (1.8%) of neck and head stings, while the rest were on the body.
Scorpion species. Most medical records of stung patients described the scorpions as black or yellow. The yellow scorpions were recorded in 29,343 cases (40.66%); the black scorpions in 28,657 cases (39.71%). There were 14,118 cases (19.56%) when the color was not described. Data analysis showed that black scorpion stings were higher than the yellow ones in the summer months; yellow scorpion stings predominated in the other three seasons. The scorpions brought to the Medical Centers by the patients or their relatives were identified as Leiurus quinquestriatus (Ehrenberg 1828), Androctonus crassicauda (Olivier 1809), and Apistobuthus pterygocercus (Finnegan 1932).
Outcome of treatment. Local pain, erithema, headache, vomiting, and anxiety were the primary complains of stung people, while local signs were mainly swelling, redness, and tenderness. Anxiety was the most common systemic symptom, while hypertension and tachycardia were the most common systemic signs. There were 43,748 (74.48%) cured patients; 15,985 (24%) were hospitalized; and 1,010 (1.4%) abandoned the hospital against doctors advice and were lost to follow-up.
Only one death was recorded due to scorpion stings in Qassiem area. The victim was a 12-year old boy who died of pulmonary edema, haematemesis, severe neurotoxicity, and circulatory failure.
Thousands of people are stung annually by scorpions with an alarming increase in various semi-arid and arid areas in developing countries with large rural populations (23). This study reflects the intensity of the epidemiological scorpion stings in Saudi Arabia that scored 72,165 cases during this five-year period with an average of 9 cases/10,000 inhabitants annually. Sting variations in different areas of Saudi Arabia may reflect climate variations in these areas.
Despite the high rate of scorpion stings, mortality rate is almost zero. This is in agreement with other scorpion syndrome envenomation in Saudi Arabia (1,5,16), while some other investigations reported deaths following stings in some areas of Saudi Arabia (4,7,9). In some regions of Brazil, more than 6,000 scorpion stings with over 100 deaths were reported during a three-year period, and 1,608 deaths were reported in the Durango city in Mexico in a 30-year period with about 800-1,000 deaths per year in all Mexico (13,21). A recent study conducted on scorpion envenomation in Southwestern Morocco has shown a high rate of scorpion stings with several deaths (19).
Comparing scorpion sting death rate in this study to that of other countries, we can conclude that the scorpion sting syndrome in Saudi Arabia does not carry the same degree of threat that has been reported in other countries despite the high rate of scorpion stings. This may be due to the excellent medical facilities and supportive care developed in recent years in different regions of Saudi Arabia in addition to the comprehensive multi-center evaluation of antivenom use where the overall mortality rate was reduced from 3% between 1985 and 1993 (5,18) to less than 0.05% when antivenom was used, as seen in this study.
This study shows that scorpion stings were frequent in the summer months of May-September, with the maximum frequency in June. This agrees with a previous study on the incidence of scorpion stings between 1986 and 1988 in Riyadh city (1).
The peak of stings incidence was in the summer months and the low incidence in winter could be attributed to the fact that scorpions do not hibernate but become less active in winter. The periods with predominant cases of scorpion stings were reported in different places as follows: Mexico (April-July), Tunisia (July-September) with maximum frequency in August, while in Brazil, stings occurred uniformly throughout the year, with slight increases in August (10,12,15). These variations may be due to environmental conditions especially rainy or dry summer.
This investigation shows that most scorpion sting victims are male (61.79%). This finding is in agreement with the results of previous studies on scorpion stings in Saudi Arabia (1,16) and other studies, such as in Brazil where 62.8% of the patients were male less than 30 years old (12), but in Tunisia, both males and females were equally affected (10). In this study, scorpion stings in males outnumbered females; this may reflect the fact that women in Saudi Arabia, in contrary to men, spend most time indoors with their families. The high rate of scorpion stings in victims less than 30 years old may be explained on the basis that most stings occurred during work where this age category is associated with most outdoor activities.
The results of this study showed the highest sting rates in the lower limbs (63%) and the next in the upper limbs (27.95%). This is similar to Brazil where most stings (46.7%) were in the hands (12). These findings may be explained on the basis that the exposed limbs are usually used in most manual activities and moving or entering the scorpion retreats while stings in other parts of the body, such as neck and head occur when resting or sleeping.
Of the 22 species identified in the Arabian Peninsula, 14 belonging to the Buthidae and Scorpionidae have been indentified in Saudi Arabia (2,8,20). This study points to Leiurus quinquestriatus (Ehrenberg 1828), Andoictonus crassicauda (Olivier 1807), and Apistobuthus pterygocercus (Finnegan 1932) as the species of medical importance in Saudi Arabia. These species are also the most common cause of human stings throughout the Middle East. Other deadly scorpion species are reported in other countries, such as Tityus stigmurus (Thorell 1876), T. serrulatus (Lutz and Mello 1922), and T. brazilae (Lourenço and Eickstedt 1984) in Brazil (6,12,13); Centruroides suffuses (Pocock 1902) in Mexico (18); Hemiscorpion lepturus (Peters 1861) in Iran (17); Centruroides sculpturotus (Ewing 1949) in the United States (18); Mesobuthus tamulus (Fabricius 1798) in India (22); and Androctonus australis (Linnaens 1758) and A. mauretanicus (Pocock 1902) in Algeria and Morocco, respectively (3,19).
We are grateful to the Ministry of Health of the Kingdom of Saudi Arabia for giving us access to their medical records.
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Address to correspondence
M. K. AL-SADOON
Department of Zoology, College of Science
P.O. Box 2455, Riyadh 11451, Saudi Arabia
Fax : 00966-01-4675755. Phone: 00966-01-4675781
Received January 8, 2002
Accepted June 3, 2002