Snakebites in southern Minas Gerais State, Brazil

SNAKEBITES IN SOUTHERN MINAS GERAIS STATE, BRAZIL

R. L. FRANCO¹, C. C. ROCHA¹, M. T. JORGE²; L.A. RIBEIRO²

1 Centro de Ciências Biomédicas, Faculdade de Medicina da Universidade Federal de Uberlândia (UFU), Uberlândia, Minas Gerais, Brasil; 2 Departamento de Clínica Médica da Faculdade de Medicina da UFU, Uberlândia, Minas Gerais, Brasil.

ABSTRACT: In Brazil, more than 80% of venomous snakebites are caused by Bothrops and about 10% by Crotalus. This study evaluated 133 reported cases that occurred between 1994 and 1996 in the 52 municipalities covered by the Pouso Alegre Regional Health Center in southern Minas Gerais State. Most of the patients were male (89.5%). The most frequently attacked age bracket was that of people in their twenties, and the most frequently bitten anatomical regions were the lower limbs (77.7%), principally the feet (34.6%). Of the 124 cases stating the snake genus, 62.9% were caused by Crotalus and 37.1% by Bothrops. The conclusion of this study is that although the epidemiology of snakebites in Minas Gerais State is similar to other regions of the country, the percentage of Crotalus bites is much higher.

KEY WORDS:Crotalus, snakebite, Brazil.

INTRODUCTION

Venomous snakes in Brazil have been classified into four genera: Bothrops, Crotalus, Lachesis, and Micrurus (2,7). Tens of thousands of envenomings that have been reported to the Ministry of Health were evaluated, and as the epidemiology and clinical manifestations are generally sufficient to differentiate between the snake genus, it was possible to determine that about 90% are caused by Bothrops, less than 10% by Crotalus, and less than 2% by Lachesis and Micrurus (2). In São Paulo State, a more precise evaluation showed that 85.6% of the envenomings were caused by Bothrops, 13.3% by Crotalus, and 1.1% by Micrurus. However, the percentage Crotalus envenomings is quite variable in different regions of the state (19), for instance Botucatu with 20% and Marília with about 10% (6,17).

This study evaluates the epidemiological aspects of snakebites in southern Minas Gerais State, emphasizing the percentage of envenomings by the different venomous snake genera.

PATIENTS AND METHODS

All the 133 recorded cases of envenoming between 1994 and 1996 in the 52 municipalities covered by the Pouso Alegre Regional Health Center in Minas Gerais were studied.

The data was obtained from the epidemiological records. These records were completed by the local health units treating the patients and were then sent to the Central Region, with the intention of informing the Ministry of Health and having the serum replaced. The classification of envenoming (snake genus) was based on epidemiological reports and clinical manifestation data.

RESULTS

The 133 cases occurred in 38 municipalities, most of them near the largest cities of the region. Of the 126 cases with sufficient information, 112 (88.89%) occurred in rural area and 14 (11.11%) in urban area. The majority of the envenomings occurred during the hotter and wetter months of the year (Figure 1). The most common patients were males in their twenties (Table 1).

Figure 1.
Monthly distribution of venomous snakebites in southern Minas Gerais State between 1994 and 1996.

Table 1.
Age as sex distribution of patients bitten by venomous snakes in southern Minas Gerais State between 1994 and 1996.

Patients were laborers/farmers (70.67%), students (6.01%), and domestic (4.51%). The majority of the envenomings occurred at work (84.21%), some during leisure activities (10.52%) or in other (5.26%). The lower limbs, especially the feet, were most frequently affected (Table 2).

Table 2.
Bite site distribution of patients bitten by venomous snakes in southern Minas Gerais State between 1994 and 1996.

The snake genus was identified in 124 cases; 78 (62.90%) were by Crotalus and 46 (37.10%) by Bothrops.

DISCUSSION

According to the data from this study, 10% of the envenomings occurred in urban areas. This reflects the findings from large cities, such as São Paulo, SP (12) and Uberlândia, MG (4). In the studied areas, the distribution of envenomings according to the time of year is similar to that in the southeast of the country (13) and in São Paulo State (15). This distribution seems to depend more on climate-related factors and on people's activities than on the snake species involved (16). The predominance of male envenoming can be seen in practically all regions (13,15), with the age bracket being slightly higher than found in São Paulo State (15).

The high incidence of envenomings involving laborers/farmers had already been reported by Vital Brazil (3) at the beginning of the century. However, data from a prospective study performed in the Vital Brazil Hospital in São Paulo showed that less than 40% of the patients in that region were laborers (16).

In certain areas, bites in groups such as rubber tappers and Indians are more frequent (11). Although one publication in literature states that the number of envenomings in work is about 25% of the total (1), another (16) shows a frequency almost as high (around 60%) as that found in this study. A higher incidence of bites in the lower limbs is caused by Viperidae snakes of the Bothrops (14) and Crotalus genera (9). This is probably due to the fact that the majority of snakes in the region studied live on the ground (5).

In São Paulo State, most envenomings are caused by Bothrops (15). This is the same for the whole of Brazil, if we consider Bothriopsis and Porthidium to be of the same genus as Bothrops (2).

According to data from the Hospital das Clínicas in Uberlândia, MG, which serves the region of the Triângulo Mineiro and a part of the adjoining Goiás State, approximately 80% of the envenomings are caused by Bothrops and 20% by Crotalus (18).

However, according to this study in southern Minas Gerais, there are more envenomings caused by C. durissus than by Bothrops. There are no data in literature to justify this unusual finding. Thus, studies should consider that preventive measures in this region should be different from the other regions. The fact that clinical manifestations and treatment of C. durissus envenomings differ from Bothrops (8) and that C. durissus envenoming is more dangerous than Bothrops (8,14) should also be considered. Envenomings by B. jararacussu are rare, but they are more severe than by C. durissus (10).

The conclusion is that the percentage of C. durissus bites in southern Minas Gerais is far greater than Bothrops bites, although the other epidemiological aspects of snakebites are similar to other parts of the country. It is of utmost importance to perform prospective studies to confirm this percentage of C. durissus bites as well as biological studies to find out the reasons for this difference.

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CORRESPONDENCE TO:

L. A. RIBEIRO - Departamento de Clínica Médica da Faculdade de Medicina da Universidade Federal de Uberlândia, Av. Pará, 1720, CEP 38400-902, Uberlândia, Minas Gerais, Brasil.

Publication Dates

• Publication in this collection
  26 June 2001
• Date of issue
  2001