EVOLUTION OF SCORPIONISM BY Tityus bahiensis (PERTY) AND Tityus serrulatus LUTZ AND MELLO AND GEOGRAPHICAL DISTRIBUTION OF THE TWO SPECIES IN THE STATE OF SÃO PAULO - BRAZIL

Original paper

EVOLUTION OF SCORPIONISM BY Tityus bahiensis (PERTY) AND Tityus serrulatus LUTZ AND MELLO AND GEOGRAPHICAL DISTRIBUTION OF THE TWO SPECIES IN THE STATE OF SÃO PAULO - BRAZIL.

V. R. D. von EICKSTEDT

, L. A. RIBEIRO , D. M. CANDIDO , M. J. ALBUQUERQUE , M. T. JORGE

1 Laboratory of Venomous Arthropods of the Butantan Institute, State of São Paulo, Brazil; 2 Vital Brazil Hospital of the Butantan Institute, State of São Paulo, Brazil; 3 State of São Paulo Health Department, Brazil; 4 Federal University of Uberlândia, State of Minas Gerais, Brazil.

ABSTRACT: Two scorpion species of medical importance occur in the state of São Paulo: the native brown scorpion Tityus bahiensis (Perty) and the highly toxic yellow scorpion Tityus serrulatus Lutz and Mello, which was brought into the state. The study of accident data of patients admitted to the Vital Brazil Hospital of the Butantan Institute from l982 to l993 revealed a gradual increase in stings by T. serrulatus in contrast to those by T. bahiensis with a variation from 5.2% to 29.7%. Also, an inventory of the scorpions sent to the Laboratory of Venomous Arthropods of the Butantan Institute over the same period showed an expressive growth in the number of T. serrulatus specimens in contrast to that of T. bahiensis. These data suggest a significative proliferation of T. serrulatus in the state of São Paulo over the past 12 years, and a probable interspecific competition between T. serrulatus and the endemic T. bahiensis. The analysis of scorpion accidents reported to the state of São Paulo Health Department (Secretaria de Estado da Saúde de São Paulo) corroborated the higher severity of T. serrulatus envenoming. The results pointed to the possibility of an increase in severe envenoming and deaths by scorpion stings in the state of São Paulo. Aiming to contribute to scorpion prevention and control programs, the present geographical distribution of both dangerous species was mapped, pointing to the areas of higher risk of scorpionism in the state.

KEY WORDS: scorpionism, scorpion control, Scorpiones, Tityus bahiensis (Perty), Tityus serrulatus Lutz and Mello.

INTRODUCTION

Scorpion envenoming is a public health problem in Brazil. From 1988 to 1990,11,574 scorpion stings with 94 deaths were reported to the Ministry of Health. Of the 11,574 cases, 4,792 occurred in the state of Minas Gerais and 2,150 in the state of São Paulo(16). Since the antivenom is administered to less than 10% of the patients, and in general only these cases are notified, the above mentioned official statistics are underestimated. Data on the etiologic agent are even more incomplete. Taxonomic identification of the offending scorpions usually occurs in a few Brazilian medical centers and that restricts the knowledge of dangerous scorpion species distribution in the country. Of the 1,608 scorpion accidents reported in the state of São Paulo in 1993(14), the offending specimen was recognized in 434 cases (27.5%). The two species of medical importance in the state are the endemic brown scorpion Tityus bahiensis (Perty) and the yellow scorpion Tityus serrulatus Lutz and Mello, which was brought into the state(12) and is considered the most dangerous species in Brazil(1,7,8,9) (15,16,18). This study was carried out due to the increase in reported envenomation cases and in records of occurrence of these species in the state of São Paulo. The main objectives were to evaluate the evolution of scorpionism over the past twelve years and to know which is the present geographical distribution of Tityus bahiensis and Tityus serrulatus in the state aiming at scorpion control programs.

MATERIAL AND METHODS

Records on the species taxonomic identification and origin were analyzed in regard to:

1.- the offending scorpions responsible for the envenomation cases admitted to the Vital Brazil Hospital of the Butantan Institute (HVB-IB) from 1982 to 1993;

2.- the scorpions sent to the Laboratory of Venomous Arthropods of the Butantan Institute (LAP-IB) from different regions of the state of São Paulo over the same period;

3.- the scorpions of the LAP-IB "Arachnological Collection" which have been preserved for systematic studies since l934;

4.- the offending scorpions responsible for the accidents reported to the state of São Paulo Health Department since 1988 when this procedure of reporting became obligatory.

To evaluate the evolution of scorpionism, the envenomation cases by T. bahiensis and those by T. serrulatus admitted to the HVB-IB from l982 to l993 were quantitatively compared every two years. The stings by each species in the two-year periods from 1982 to 1983 and from l992 to 1993 were analyzed considering the" município" (administrative subdivision of the state comparable roughly to the" county" in the United States) in which they occurred, to compare the geographical distribution of the accidents. To estimate the territorial expansion of T. serrulatus, data on the scorpions sent to the LAP-IB were quantitatively and qualitatively compared in the same way as the accidents The geographical distribution of the two species in the state of São Paulo was obtained by comparing the available data on the reported envenomation cases and the records of occurrence.

RESULTS

Table 1 shows that, in all, 3,146 victims of T. serrulatus and T. bahiensis stings were admitted to the HVB-IB from 1982 to 1993. Among the two-year periods analyzed, the total number of envenomations by both species ranged from 459 to 649. There was a percentage increase in stings by T. serrulatus in contrast to those by T. bahiensis, ranging from 5.2% to 29.7%.

TABLE 1.
Cases of scorpion envenoming by Tityus bahiensis and Tityus serrulatus admitted to the Vital Brazil Hospital, Butantan Institute and percentage variation from 1982 to 1993.

In Table 2 one can see that most of the envenomation cases by T. bahiensis admitted to the HVB-IB from 1982 to 1983 and from 1992 to 1993 occurred in the "municípios" of São Paulo, Osasco, Carapicuiba and Guarulhos, all of them located in Greater São Paulo (metropolitan area of the city of São Paulo). Of the 504 victims of T. bahiensis stings from 1982-1983 and of the 354 victims from 1992-1993, respectively, 67.6% and 71.7% were stung in these four "municípios". Most of the envenomings by T. serrulatus also occurred in São Paulo, Osasco and Carapicuiba. In all those "municípios" where there was a marked increase in T. serrulatus envenoming, there was a correlated decrease in that by T. bahiensis. Of the 208 envenomings by the two species that occurred in the city of São Paulo from 1992-1993, 152 were analyzed according to the districts of the city in which the victims were stung, as follows: 74 (48.7%) occurred in the eastern districts of the city (Itaquera, Guaianazes, São Mateus); 31 (20.4%) in the northern districts (Pirituba, Perus); 27 (17.8%) in the southern districts (Morumbi, Santo Amaro); 18 (11.8%) in the western districts (Rio Pequeno, Jaguaré, Butantan) and 2 (1.3%) in the downtown area. In the eastern districts of the city of São Paulo, the highest percentage (94.6%) of T. bahiensis accidents were observed in contrast to those by T. serrulatus, while in the western districts the highest percentage (27.8%) of T. serrulatus accidents were detected.

TABLE 2.
Distribution of envenomation cases by Tityus bahiensis and Tityus serrulatus admitted to the Vital Brazil Hospital, Butantan Institute according to patient's origin from 1982 to 1993.

Table 3 reveals that from 1982 to 1993, the LAP-IB received 36,646 specimens of Tityus bahiensis and Tityus serrulatus captured in the state of São Paulo. From 1992-1993, the total number of T. bahiensis specimens was 5.6 times more than that from 1982-1983, while the number of T. serrulatus specimens was 30.3 times more than that from 1982-1983.

TABLE 3.
Number of scorpions Tityus bahiensis and Tityus serrulatus from the state of São Paulo sent to the Laboratory of Venomous Arthropods, Butantan Institute from 1982 to 1993.

In Table 4 one can observe that of the 89" municípios" of the state of São Paulo which sent scorpions to the LAP-IB from 1982-1983, 41 are located in the geographical macroregion 4 (mr-4), which includes the Paraiba River Valley and the eastern region of the state; 21 are in the mr-1 (Greater São Paulo); 17 in the mr-5 (southern region of the state and Ribeira River Valley); 8 in the mr-3 (Alta Araraquara and Alta Mogiana) and 2 in the mr-2 (Alta Paulista and the Paranapanema River Valley). Of all the "municípios", 72% sent Tityus bahiensis, 11% sent Tityus serrulatus and 17% sent scorpions of both species.

TABLE 4.
Number of "municípios" of the state of São Paulo which sent scorpions Tityus bahiensis and Tityus serrrulatus to the Laboratory of Venomous Arthropods, Butantan Institute according to the state macroregions from 1982 to 1983.

Table 5 shows that from 1992-1993, 133" municípios" of the state of São Paulo sent scorpions to the LAP-IB, as follows: 56 located in the mr-4, 26 in the mr-5, 24 in the mr-l, 14 in the mr-3 and 13 in the mr-2. Of all the "municípios", 51.9% sent Tityus bahiensis, 17.3% sent Tityus serrulatus and 30.8% sent scorpions of both species.

TABLE 5.
Number of "municípios" of the state of São Paulo which sent scorpions Tityus bahiensis and Tityus serrulatus to the Laboratory of Venomous Arthropods, Butantan Institute according to the state macroregions from 1992 to 1993.

The comparison of data from 1982-1983 (Table 4) with that from 1992-1993 (Table 5) pointed to a percentage decrease of "municípios" which sent T. bahiensis in correlation to a percentage increase of those "municípios" which sent T. serrulatus or both species.

In Table 6 one can see that from 1988 to 1993, 6,437 scorpion envenomings with 17 deaths were reported in the state of São Paulo. These data include diagnoses made of the patient's history and clinical evaluation, with or without the identification of the offending scorpion. Of the 17 fatalities, 7 (41.2%) were caused by T. serrulatus, and of the 10 remaining cases, either the scorpion was not identified or it was not captured.

TABLE 6.
Number of scorpion accidents and deaths reported to the state of São Paulo Health Department from 1988 to 1993.

Figure 1 shows the geographical distribution of T. bahiensis and T. serrulatus in the state of São Paulo based on scorpion envenomation cases and records of occurrence. The two species were detected either separately or together in 323 "municípios", as follows: 35 in the mr-1, 56 in the mr-2, 70 in the mr-3, 105 in the mr-4 and 57 in the mr-5. Macroregions 1 and 4 comprising 39 and 126 "municípios", respectively, presented the widest geographical distribution of the two scorpions species. Of all the" municípios", T. bahiensis was detected in 254 (78.6%) and T. serrulatus in 210 (65.0%).

FIGURE 1.
Geographical distribution of Tityus bahiensis (Perty) and Tityus serrulatus Lutz and Mello in the state of São Paulo.

DISCUSSION

The data of the HVB-IB allowed to evaluate the evolution of scorpionism by T. bahiensis and T. serrulatus from 1982 to 1993 in Greater São Paulo, where most of the stung patients came from. It is worth stressing that due to underreporting, and to the fact that these data correspond only to the confirmed cases, the exact number of scorpion stings in this area is a lot higher. The observed yearly declining trend in the number of envenomations is not due to a reduction of scorpion stings in Greater São Paulo, but rather to a decentralized medical service that was established since 1988.

The increase in T. serrulatus stings in correlation to a decrease in T. bahiensis stings in São Paulo, Osasco and Carapicuiba suggest competition between the two species with domination of T. serrulatus in these" municípios". Bücherl(4) reported the overlap of Tityus serrulatus, T. bahiensis and T. trivittatus with further domination of one of them in some "municípios" of the states of Minas Gerais and São Paulo. Stutz(17) studied the gradual substitution of T. bahiensis and Bothriurus araguayae (Vellard) for T. serrulatus in Uberlandia, state of Minas Gerais and Lourenço(12) analyzed the fast dissemination of this species in Brasilia, the country's capital, where T. fasciolatus was the dominant species. In regard to Greater São Paulo, although Bücherl(3) reported that by 1957, specimens of T. serrulatus were captured in the surroundings of the city of São Paulo, Rosenfeld(13) only mentioned stings by T. bahiensis in the inventory of scorpion accidents attended at the HVB-IB from 1954 to 1965. Considering the fact that of the patients admitted to this Hospital in 1979, 2.8% of them had been stung by Tityus serrulatus(6), one can assume that a significative proliferation of this species in Greater São Paulo might have started between 1965 and 1979. The fast territorial expansion of T. serrulatus was probably the result of the intense urbanization process which took place in this region since the 1970s. The great plasticity of adaptation to human dwellings, the parthenogenetic reproduction and some other peculiar biological traits(2,5,10,11,12) make T. serrulatus an opportunistic species which readily invades disturbed environments and displaces less plastic endemic species, as it has previously been reported. Taking into account the fact that in the last two-year periods studied (1990-1991 and 1992-1993), the percentage of T. serrulatus stings has almost doubled in Greater São Paulo, one can ascertain that should this tendency be maintained, within a eight-year period around 80% of the scorpion envenomations in this region will be caused by T. serrulatus. However, it is worth emphasizing that in this evaluation, neither unpredictable biological factors nor possible control programs have been considered.

The significant increase in scorpion specimens sent to the LAP-IB from 1982 to 1993 allowed to obtain new records of occurrence of Tityus serrulatus and T. bahiensis in the state of São Paulo, as well as to detect the dispersal of T. serrulatus. The comparision of Table 4 and Table 5 showed a significative percentage increase in" municípios" which sent T. serrulatus, mainly due to a greater number of those "municípios" which sent both species in the last years. Although the geographical area of the second sampling is only 50% coincident with the first, these results suggest a territorial expansion of T. serrulatus in areas originally colonized by Tityus bahiensis. The correlated percentage decrease of" municípios" which sent T. bahiensis probable interspecific competition between the two species, as previously suggested.

In spite of a higher frequency of stings by T. bahiensis in the state of São Paulo, Tityus serrulatus accounted for the 7 deaths reported to the state of São Paulo Health Department from 1988 to 1993, in which the offending scorpion was identified. In addition, the presence of Tityus serrulatus was noticed in all the "municípios" where the remaining 10 fatalities occurred. These results pointed to a higher toxicity of T. serrulatus stings, as mentioned by several authors(1,7,9,15). The suggested expansion of the territorial range of T. serrulatus within the state of São Paulo might, therefore, bring about an increase in severe scorpion envenoming and death in this region.

According to the geographical distribution map the areas of high risk of envenoming by T. bahiensis and T. serrulatus in the state of São Paulo are: 1. Greater São Paulo (mr-1), due to a wide distribution of the two species, high population density and highly favorable environmental conditions; 2. the Paraiba River Valley and the eastern region of the state (mr-4), in which 50% of all the reported accidents and 5 of the 7 deaths caused by T. serrulatus occurred; 3. the northern region of the state (mr-3), the only one which presents a greater number of" municípios" with records of T. serrulatus than with T. bahiensis. These data might be useful in setting up scorpion prevention and control programs and also specific guidance of medical procedure in the areas of high risk of scorpionism.

ACKNOWLEDGEMENTS

The authors are very thankful to Dra. Vera Beatriz Gualtieri for providing useful information on certain reported accidents, and to Regina T.I. Bernal and Claudia von Eickstedt for their technical assistance.

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CORRESPONDENCE TO:

V.R.D. von EICKSTEDT - Laboratório de Artrópodes Peçonhentos, Instituto Butantan, Av. Vital Brasil, 1500, CEP 05503-900, São Paulo, Brasil.

Publication Dates

• Publication in this collection
  08 Jan 1999
• Date of issue
  1996