According to Secretaría de Salud (SSA [Ministry of Health]), “Scorpion sting envenomation [SSE] is a health problem of notable importance in Mexico”¹, and ranks 15^th among the most relevant conditions in the country.²

In Programa Específico de Acción para la Prevención y Control de la Intoxicación por Picadura de Alacrán 2013-2018 (Specific Action Program for the Prevention and Control of Scorpion Sting Envenomation), SSA identified four important aims for the management and control of this medical condition:

1. To improve epidemiological information systems in the states to include updates regarding scorpion stings and the most affected regions.
2. To formulate prevention strategies that consider the risk factors for each specific area of the country.
3. To ameliorate housing conditions in priority areas.
4. To reverse “[...] the annual increase in cases and maintaining the downward trend in deaths from SSE”.²

The high incidence of endemic scorpions has been acknowledged not only in epidemiological research; scorpion distribution studies have gained relevance in the last decade in environmental protection and taxonomy. Mexico accounts for 12% of scorpion species worldwide. Anyhow, the total number of scorpion species is not definitive. Riaño-Umbarila³ et al. claim that Mexico has 280 species; Ponce Saavedra⁴ suggests the existence of 289 species, whereas Ureta, et al.⁵ state that the real number is 294. According to Ponce Saavedra, Francke, Quijano, and Cortés, the 32 states of Mexico have a registry of scorpions, including in total 38 genera.

The scorpions from the family Buthidae are considered medically important in Mexico, specifically the species Centruroides and Chaneke. In Jalisco, the state with the historically highest incidence of SSE, Centruroides elegans, Centruroides infamatus, Centruroides ornatus, and Centruroides tecumanus are the main species to cause envenomations.

Most of the literature on SSE^6-9 emphasizes that the mortality rate due to scorpion sting since 2000 in Mexico has decreased considerably because of the use of fabotherapics, as the main therapeutic approach. Besides, it is commonly accepted that SSE is related to poverty conditions and certain weaknesses in the health system in Mexico; for example, the lack of hospital infrastructure in rural areas. In general, the network of public hospitals in the country —composed of various institutions such as Instituto Mexicano del Seguro Social (IMSS [Mexican Social Security Institute]), the different health services in each state, Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado (ISSSTE [Institute for Social Security and Services for State Workers]), among others— mainly deal with SSE cases.

Unlike envenomation caused by snakebites, SSE has drawn the attention of Mexican health authorities on such a way that they developed Norma Oficial Mexicana (Official Mexican Standard) NOM-033-SSA2-2011 for the surveillance, prevention, and control of scorpion sting envenomation. Likewise, from 2013 to 2018, a series of documents, such as the Specific Action Program and the Standardized Procedures Guidelines for Epidemiological Surveillance of SSE, was published, seeking to establish a framework of action to address this problem.¹ In this context, with an active government infrastructure for the treatment of SSE nationwide, it is appropriate to evaluate the progress in the challenges and aims identified in 2013. For this purpose, it is relevant to analyze the official data regarding new cases of SSE and incidences reported by SSA from 2017 to 2019.

Information regarding new SSE cases was obtained from Boletín Epidemiológico del Sistema Nacional de Vigilancia Epidemiológica from SSA. It provides weekly reports of SSE cases, which are classified in the non-communicable diseases section, specifically with the code CIE-10ª REV. T.63.2, X22. SSE data for the 52 weeks for 2017, 2018, and 2019 were collected.⁹

It is noteworthy to mention that the bulletin reports the state, the number of new cases per week, and a cumulative number that disaggregates the case information by sex.

According to SSA, the data reported include all institutions of the national health system, which by January 2020 consisted of 20,005 public and private care units. The health units report cases based on Manual de Procedimientos Estandarizados para la Vigilancia Epidemiológica de la Intoxicación por Picadura de Alacrán (Standardized Procedures for Epidemiological Surveillance Booklet for Scorpion Sting Envenomation).

Each state is responsible for accounting the cases; the data are processed by a division of SSA (i.e. Dirección General de Epidemiología [General Directorate of Epidemiology], which is responsible for the final publication of Boletín Epidemiológico.

Data were revised for each state independently and aggregated in regions, using the regionalization proposed by Instituto Nacional de Estadística y Geografía, INEGI [National Institute of Statistics and Geography]), which divides Mexico into four regions: Central region, Central-western region, Northern region and Southeast region.

The information collected was processed using Microsoft Excel, version 16.45. The spatial representation of the incidence of scorpion stings in Mexico was processed in R Studio, version 1.4.11. Incidence and population data for each state were collected from the statistical yearbooks published by INEGI.

For the newly reported SSE cases in the 52 weeks of 2017, 2018, and 2019, there was a difference between the total number of cases calculated based on the total number of incidents reported weekly, and the total SSEs calculated; for example, the sum of the information disaggregated by the sex of the victims. Table 1 compiles the new SSE cases in Mexico from 2017-2019.

Interestingly, in 2017, in seven out of the 32 states (Baja California, Baja California Sur, Campeche, Nuevo León, San Luis Potosí, Tamaulipas, and Yucatán) new SSE cases (both “NC” and “F+M”) were consistent. In 2018, Baja California, Coahuila, and Nuevo León reported equally consistent data. In 2019, Baja California Sur, Campeche, Coahuila, San Luis Potosí, Tamaulipas, Tlaxcala, and Yucatán did not report any difference between these two criteria.

Annually, by 2017, the total number of SSE cases nationwide —according to the “NC” column— was 273,807 cases. In contrast, taking into account the “F+M” data, the total number of cases was 290,516.

In 2018, there was a total of 260,371 “NC” SSE cases; however, when the information was disaggregated by sex, this number increased to 278,605 cases. This phenomenon was also observed in 2019, when the total number of "NC" SSE cases was 273,351, while the "M+F" SSE cases were 292,890.

If only considering the “NC” columns, it would be possible to affirm that, from 2017 to 2019, SSE cases did not increase in Estado de México and that, in 2018, there was a decrease in the number of cases. In contrast, when considering the total number of “M+F” SSE cases, the cases increased during 2017-2019.

When analyzing the columns, indicating the differences between “NC” and “M+F” SSE cases (∆), the differences are not the same in all states. In 2017, the five states with the highest incidences were Durango (∆ 6,149), Puebla (∆ 2,745), Jalisco (∆2,195), Morelos (∆ 1,415), and Oaxaca (∆931).

In 2018, the five states with the highest incidences were Durango (∆ 5,842), Puebla (∆ 3,422), Jalisco (∆ 2,848), Morelos (∆ 1,988), and Michoacán (∆1,692).

In 2019, Durango remained the state with the highest incidence (∆ 6,169), followed by Puebla (∆ 2,764), Morelos (∆ 3,613), Jalisco (∆ 2,100), and Guerrero (∆ 1,707).

The availability of weekly data allowed identifying the weeks with the highest number of registered incidents (see Graphic 1 and Table 2). In 2017, week 32 (August 7-13) had the highest incidence of cases nationwide, with 1,917 cases, followed by week 30 (July 24 -30), with 1,526 cases. In 2018, week 33 (August 13-19) registered the highest incidence of cases (11,362), followed by week 32 (August 6-12), which according to Boletín there were 11,599 fewer “M+F” cases, compared to the number of new cases per week.

Interestingly, week 32 is the only week (out of the ten) with the highest number of cases repeated in 2017, 2018, and 2019.

Regarding the discrepancies in the weekly accounting of new SSE cases, it is also pertinent to use accumulated total cases by sex of the victims. Table 3 shows the SSE cases in ascending order.

In 2017, Jalisco topped the list (51,975 cases), followed by Guanajuato (46,297 cases), Guerrero (41,615 cases), Morelos (27,846 cases), and Michoacán (27,738 cases).

In 2018, Jalisco remained in the first position, with 4,110 fewer cases reported. Guerrero moved to second place, with 41,188 cases (+427), followed by Guanajuato, with 40,651 (-5,646), Michoacán, with 28,175 (+437), and Morelos, with 27,133 cases (-713).

Between 2017 and 2018, nine out of the 32 Mexican states (Jalisco, Nayarit, Puebla, Mexico, Colima, Sonora, Zacatecas, Baja California Sur, and Tlaxcala) kept their position in the list of SSE cases. Notably, in 2017, the five states with the most cases accounted for 67.27% of the total SSE cases; in 2018, they accounted for 66.4%; and in 2019, they accounted for 66%. In the three years analyzed, in 17 out of 32 states, there were fewer than 1,000 SSE cases annually. Graphic 2 shows the distribution of SSE cases in Mexico.

From 2018 to 2019, 53% of the states maintained their position in the list concerning the previous year. Although Jalisco reported a decrease of 859 cases in 2019, it remained on top of the list with 46,988 SSE cases, followed by Guerrero for the second year in a row, with 45,690 (+4,502) cases, Guanajuato, with 44,341 cases, Michoacán, with 30,430 cases, and Morelos, with 25,518 cases.

Regarding the incidence of cases in 2017, the five states that reported the highest number of SSE cases per 100,000 inhabitants in Mexico were (see Table 4) Colima (1552.42), Morelos (1433.11), Guerrero (1159.75), Nayarit (1141.54), and Guanajuato (789.510) (see Table 4).

In 2018, Colima topped the list, with 1416.24 cases per 100,000 inhabitants, followed by Morelos (1365.11), Nayarit (1289.24), Guerrero (1136.20), and Guanajuato (682.97). Overall, 40% of the states of Mexico reported a decrease in cases, compared to the previous year. In 2019, the five states with the highest incidence of SSE cases were Colima (1380.61), Nayarit (1343.25), Morelos (1281.440), Guerrero (1253.85), and Guanajuato (718.23).

Graphic 3 displays the variation in the incidence of SSE cases in the 32 states of the country. Table 5 compiles the total SSE cases by region.

In 2017, the nine states that compose the Central-western region (Aguascalientes, Colima, Guanajuato, Jalisco, Michoacán, Nayarit, Querétaro, San Luis Potosí, and Zacatecas), accounted for 56.5% of all cases in the country, followed by the Central region (34.4%), North region (25.5%), and Southeast region (0.22%).

Between 2018 and 2019, the Central-western and North regions reported a slight decrease in cases, while the other regions showed a slight increase.

Out of the 290,516 SSE cases recorded in 2017, 48% (138,606 SSE) were men, and 52% (150,910) were women. In 2018, 49% of SSE cases were men, and 51% were women. In 2019, out of the 292,890 cases, 48% were men, and 52% were women. Although the global aggregate was constant in the years analyzed, the disaggregated SSE and states data revealed differences (see Graphic 4).

In Jalisco and Zacatecas, the proportion of SSE cases was 50% for men and women. In 29 out of the 32 states, most of the cases were women; in Colima, Querétaro, and Yucatán, the cases indicated a higher percentage of male cases (Figure 1).

Programa Específico de Acción para la Prevención y Control de la Intoxicación por Picadura de Alacrán 2013-2018 from SSA defined two main objectives: “to promote prevention and self-care of health among the population to avoid SSE cases” and “to provide specific and timely treatment to reduce mortality”.¹

The same document presented four strategies to control SSE. The first one involved improving the epidemiological surveillance system to include SSE and areas with an endemic presence of scorpions. The second strategy sought to improve housing in the most vulnerable areas by installing protective screens on doors and windows, encouraging the use of mosquito nets, and identifying refuge sites for scorpions in homes and residential areas. The third strategy is the chemical control (insecticides) of scorpions inside and outside houses. The fourth strategy, mainly spread, proposed expanding access to health services, particularly increasing the number of anti-scorpion fabotherapics, and establishing that the treatment of SSE should be carried out in health units along with first and second levels of care.

Although SSE is not a recent health issue, the interest in treating it varies depending on the interests of each current administration. The president-centered nature of the policy aimed at controlling SSE changed direction after Ernesto Zedillo's administration. It had personal expertise with SSE, and promoted the development of a strategy for controlling and treating this acute condition.¹³

Certain common challenges have been identified in most of the literature on the epidemiology of SSE; for example, epidemiological surveillance⁷ and the vulnerability of specific population groups such as infants and adults, and care outside hospitals with home remedies.

A study by Dhaesa-Dávila, who addressed the pharmacological management of SSE in Mexico in the late 1980s, reported that clinical records on scorpion stings were deficient and, in many cases, nonexistent. This observation suggests that the population in regions with the highest incidence of poisonous scorpions has only oral traditions regarding scorpions and prevention and treatment measures.¹⁴

A study by Celis that analyzed mortality due to scorpion stings proposed improving nonfatal attack records and emphasizing treatment measures in the child population because 68% of recorded deaths by SSE are infants younger than 5 years old.⁷

Castillo-Pérez stated that the public health measures implemented in Guanajuato have been exclusively therapeutic; that is, the availability of fabotherapics has been ensured.⁸

Thus, the study points out that no efforts were made to create prevention strategies in this state.8

Chowell, Díaz, Saldaña and Alemán found that most of the health units attached to the health services of Colima do not have personnel trained for the administration of fabotherapics. Likewise, they reported that the long periods between stings and the initiation of treatment is one of the main problems to be addressed in the state.¹⁵

Thus, this research's main objective was to compare the goals and strategies for the control of SSE with the epidemiological data for SSE in 2017, 2018, and 2019. Therefore, the first issue to address will be improving the epidemiological surveillance of SSE.

Based on an comprehensive review of the data regarding new SSE cases, there was a remarkable difference between the total number of cases reported weekly and the total number of SSE cases disaggregated by sex of the victims. This discrepancy was especially apparent in some states of Mexico, for example, in Durango and Puebla. In Durango, the number of cases exceeded 6,000 each year analyzed, reflecting profound deficiencies in the methodology used for SSE reporting SSE in these states and in the dissemination of information received by the administration.

In 26 out of the 32 states in Mexico, the annual cases number was less than 1,000; however, it concerns that the states with the highest incidences are those with the highest number of annual cases. Furthermore, there is a lack of data to conduct a more in-depth analysis of the epidemiology of SSE. Information on the municipalities where incidents are reported, the age of victims and the victim's occupation would be relevant data for future analyses.

Although there have been studies like Castillo-Pérez's, including information on SSE disaggregated by the municipality, these data are not available to the public. Specifically, Castillo-Pérez stated that the data used in his research came from the Unified Updated Epidemiological Surveillance System of Guanajuato; but, after reviewing the Ministry of Health of Guanajuato's website, it was not possible to locate the data. Direct references to this system refer to the national epidemiological surveillance system platform, whose access is limited to SSA staff.⁸ One possible way to obtain this information is disclosure. Instituto Nacional de Transparencia, Acceso a la Información y Protección de Datos Personales (INAI [National Institute of Transparency, Access to Information]) makes this information public and it would be useful for future research on SSE in Mexico.

In Plan Específico de Acción 2013, SSA stated that the main goal was to reduce the incidence of SSE cases by 36.5% by 2018. It was estimated that it was necessary to have fewer than 208,838 cases in 2017 or fewer than 198,396 cases in 2018 to achieve that goal .

The results of this research show that this goal was far from being met. In 2017, there were 69,767 more SSE cases than estimated, and in 2018, there were 94,494 more SSE cases than estimated.

Thus, the government’s strategy for reducing mortality has had a double effect. On the one hand, positive results (decreased mortality) justified the monetary investment in fabotherapics, but on the other, focusing on mortality detracts from the importance of morbidity and, therefore, diverts attention from the failure and abandonment of prevention policies, such as improving housing in areas with higher risk.

Regarding this latter, the initiative of replacing earth floors with concrete floors was abandoned. The work by Silva-Domínguez is especially interesting because it states that the factors increase the risk of SSE, i.e., keeping ducks in the house, the lack of concrete roofs and floors, and child labor.¹⁶ Additionally, the future Plan Específico de Acción should also consider the environmental and climatic factors associated to the increase of SSE. Almaraz-Lira et al. demonstrated that high temperatures and heavy rain affect the incidence of scorpion stings.¹⁷

Finally, it is critical to review the latest strategy of increasing the availability of anti-scorpion fabotherapics in the country. During 2013-2018, different health agencies around the country purchased drugs. Thus, the only publicly available information was found in the IMSS' transparency portal, which reports that in 2018, the Institute bought approximately 194,885 units of anti-scorpion fabotherapics for $182.00 MNX per unit. ¹⁸

Since 2018, this transparency platform has been dismantled due to the new unified purchasing strategy promoted by the federal government. The main problem with IMSS data is that the headquarters made the purchases; therefore, it is not possible to determine how the units were distributed to the states.