Introduction

Stings and by venomous animals are a concern to health authorities in many countries because of the severity, magnitude, and transcendence of the poisoning they cause (Chippaux et al., 1984). Within this group, scorpions are of major medical importance due to the morbidity/mortality caused by them (González-Sponga, 1984). They pose a serious public health problem in certain regions of the Americas (Dehesa-Dávila, 1989; Biondi-Queiroz et al., 1995). The Buthidae family includes the majority of the species that are hazardous to humans (Broglio & Goyffon, 1980; Illanes, 1981). Amongst other genera, this family is represented in Venezuela by the Tityus genus, which is exclusive to the American Continent and is responsible for most of the cases in Brazil and Venezuela (González-Sponga, 1984; Porras et al., 1994; Biondi-Queiroz et al., 1995). Alterations in cardiovascular and pulmonary functions are the most frequent clinical manifestations and causes of death amongst victims of scorpion stings (Broglio & Goyffon, 1980; Illanes, 1981; Abroug et al., 1991; Amaral et al., 1992, 1994).

In Venezuela, in the endemic zones of Monagas State located in the Turimiquire subregion, scorpion poisoning has been classified as a relevant public health problem (Figueredo et al., 1985). During the 1989-1991 triennium, Velasquez et al., (1992a, 1992b) demonstrated an incidence rate of 2.82‰ (398 cases), establishing the existence of a hyper-endemic zone for scorpion stings. An example of the severity of scorpion poisoning within Venezuela's Northeastern Region was attested by De Sousa et al., (1995a). They describe the case of a nine-year-old child from the Turimiquire subregion of Anzoátegui State, bordering on Monagas State, who developed a cerebral parenchymatous lesion, cardiorespiratory alterations, blood coagulation disorders, and upper digestive hemorrhage following scorpion poisoning.

The scarce epidemiological research on scorpion poisoning to date in Venezuela poses a barrier to adequate understanding of how relevant this problem is for the public health sector. We thus proposed to characterize some epidemiological aspects of scorpion stings in two bordering counties (Acosta and Caripe) of the Turimiquire subregion of Monagas State in Northeastern Venezuela. Our results show that the two are endemic for scorpion poisoning, and thus pose a public health problem.

Methodology

Material and methods

This is a retrospective epidemiological study carried out in Acosta and Caripe counties in the Turimiquire subregion of Monagas State, in Northeastern Venezuela (figure 1). The data cover a longitudinal chronological series from January 1987 to December 1993. All cases within this area, attended and recorded in the daily morbidity records of the emergency service of the county hospitals in the town of San Antonio de Capayacuar (Acosta) and Caripe (Caripe) were included in the study.

Scorpion sting incidence rates were expressed on a base of 10,000 inhabitants per year, considering the population progression. This progression was calculated with figures obtained from the Settlement Population Nomenclator Report of the Northeastern Region of Venezuela, published by the statistics bureau, or Oficina Central de Estadística e Informática (OCEI). For each county, the incidence rates for each year of the study period (1987-1993), the average annual rate (AAR), and the reference period median (RPM) were calculated. The scorpion poisoning index for both counties was obtained as a quotient that relates their average incidence rate values.

Data processing

Statistical analysis of variables was done by applying parametric methods: 1) descriptive measurements for univariate central tendency and dispersion of data; 2) distribution of Student's t differences between means; 3) demonstrations concerning proportions of large samples' inference test with respect to the difference of proportions with independent sampling; and 4) time series analysis test of cyclical fluctuations. A significance value of 95% confidence (p<0.05) was considered.

Results

Cases of scorpion poisoning in Acosta and Caripe counties from 1987 to 1993 are shown in Table 1. Acosta recorded 212 scorpion stings during the study period. The highest frequency of scorpion poisoning was in 1989 and the lowest in 1988. Caripe recorded a total of 86 cases of scorpion poisoning, with 1993 having the most cases and 1990 the least. Cases for Acosta ranged from 2 to 3 per month and about 30 per year. Caripe averages about one patient per month and twelve per year. Comparison of the monthly mean cases of scorpion poisoning for each year among both counties is shown in figure 2; Acosta as compared to Caripe showing statistically significant differences in all years evaluated (p<0.05).

The observed seasonal behavior of poisoning in both counties, accumulated for each month during the 1987-1993 period is shown in figure 3. Acosta County displays a cyclical fluctuation phenomenon that is statistically significant (p<0.05). It presents approximately three cycles a year with three peaks of maximum incidence, in February, June, and September. The month of June accumulates the highest frequency with 27 scorpion stings in the 1987-1993 period. For Caripe, this cyclical fluctuation did not show statistically significant differences (p>0.05), presenting only two peaks of maximum incidence, in the months of March and August; the latter accumulating the most number of cases with 13 scorpion stings. An opposite trend in both counties is observed when comparing the fluctuation trends in the frequency of cases; that is, when the incidence in Acosta increases, it decreases in Caripe, and the months of maximum incidence in each region do not coincide.

Table 2 shows that the scorpion poisoning incidence was higher in Acosta County, with an average annual rate of 18.30‰ , and lower in Caripe County, with a corresponding value of 4.37‰. The reference period median was 30.63^‰ for Caripe and 128‰ for Acosta. The scorpion poisoning incidence coefficient was 4.18 times higher in Acosta County than in Caripe. In Acosta, the years of greatest epidemiological importance for scorpion poisoning were 1989, 1990, and 1993, with incidences of 23.30‰ , 20.54‰, and 19.80‰ respectively, presenting a significantly higher incidence rate than other years in the study period (p<0.05). For Caripe, the most significant epidemiological year was 1993 (p<0.05). As shown in figure 4, incidence rates were higher in Acosta for all the study period, displaying statistically significant differences when compared to those of Caripe (p<0.05).

Discussion

Previous research by Figueredo et al., (1985) in Monagas State shows that scorpion sting morbidity/mortality is relevant in this region. Velasquez et al., (1992a, 1992b) determined an average annual incidence of 2.82‰ in this State for the 1989-1991 triennium. They also established Acosta County as a hyperendemic area (18.30‰) in comparison to the other regions of the same State. Expanding the longitudinal period of study (1987-1993) in Acosta County, our results yield an average annual rate of 18.30‰ and an RPM of 128.00‰. The scorpion poisoning index confirms the conclusions of Velasquez et al., (1992a, 1992b) classifying Acosta County as a hyperendemic zone for such injuries. We observed greater incidence values in 1989, 1990, and 1993 for Acosta, leading us to assume that the frequency of scorpion stings has tended to increase. The incidence for Caripe shows a much greater stability throughout the study period. The significantly greater frequency of cases for Acosta indicates that 2 or 3 reported scorpion stings per month and about 30 per year may be expected in this region. However, we expect one patient per month and around twelve per year within the Caripe area.

Plotting of the frequency of recorded scorpion sting cases shows cycles of maximum and minimum peaks that display an opposite behavior when comparing the two counties; when the number of cases increases in Acosta, it decreases in Caripe. This phenomenon of cyclical fluctuations over time is statistically significant for Acosta. As in other countries, the maximum peaks of scorpion poisoning incidence coincide with the beginning of rainy season cycles (Velasco-Castrejon et al., 1976; Illanes, 1981; Dehesa-Dávila, 1989). The appearance of the maximum peaks in different months for the two counties (Acosta and Caripe) is probably due to the variation in the beginning of the rainy season in these two areas of the Turimiquire subregion of Monagas State.

De Sousa et al. (1995b) describe a scorpion poisoning epidemic in Montes County, Sucre State, during 1993. This county borders on Acosta and shares the same physical-geographic and ecological area of the Turimiquire subregion, located in Venezuela's Northeastern Region. This subregion has several different ecosystems within its area of influence (Manzanilla-Puppo, 1992), including a tropophilous jungle and evergreen woods (rain and misty forests) (González-Sponga, 1984). The tropophilous jungle occupies the foothills region and is characteristic of the three States making up the Turimiquire subregion (Anzoátegui, Monagas, and Sucre). With an average annual temperature between 25 and 28^oC, average annual precipitation between 1,000 and 2,500 mm, vegetation with trees 30 to 40 meters high, scarce epiphytes, and a well-developed herbaceous stratum, this tropophilous jungle is one of the habitats described as harboring the Tityus genus in Venezuela.

In Venezuela, scorpions have a wide geographical distribution (González-Sponga, 1984). Potential risk areas for poisoning coincide with the dispersion of the Tityus genus (González-Sponga, 1984; De Sousa et al., 1996). In the country's central regions, such as the Federal District and Miranda State, cases of scorpion stings are related to the presence of Tityus discrepans (González-Sponga, 1984; Porras et al., 1994). A new species of this genus (Quiroga, 1988) has been reported in Punceres and Bolívar Counties in the Northern-Central Region of Monagas State (Velasquez et al., 1992a, 1992b). This suggests that scorpion poisoning in Acosta and Caripe, especially severe cases, is associated with the presence of this genus. We have collected several specimens of this taxonomic classification in field captures.

In other regions of the Americas, severe stings by these arthropods have also been correlated with different species belonging to this genus. In Brazil, Tityus serrulatus, Tityus bahiensis (Bücherl, 1953, 1969, 1978; Spirandeli-Cruz et al., 1995; Lourenço & Cuellar, 1995), and Tityus stigmurus have been involved in most cases; the latter predominant in the Northeastern Region of Brazil (Eickstedt, 1983/ 84; Azevedo-Marquez et al., 1992). In Bahía State, Biondi-Queiroz et al. (1995) have verified an increase in the scorpion poisoning incidence during the period 1992-1994 in the Greater Salvador Metropolitan Area. In this study, the Tityus genus was identified as the etiologic agent in 98.1% of the cases.

It would be interesting to characterize the geographical distribution of the scorpionic fauna in Acosta and Caripe, determining which species of scorpions are present there. Regarding this, Manzanilla-Puppo (1992), applying a morphometric study, Truss Network and other techniques, characterized in Venezuela the geographical distribution and ecological niches of the Rhopalurus genus. Application of this methodology or its alternatives would help extend the knowledge on the scorpionic fauna of this region and its relation to venomous stings.

We conclude that Acosta County in the Northwestern area of Monagas State is a hyper-endemic zone for scorpion poisoning, thus constituting a public health problem. The results of this study lead us to more detailed research on the epidemiological characterization of such poisoning and the identification of species within the study area.

Acknowledgments

Our special gratitude to Carlos Zamora and Pedro Medina of the Department of Scientific Photography of the IVIC.

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