Incidence of Ascaris ssp in United Mexican States’ population for twenty years (2003-2022) and incidence prediction until 2030

doi:10.21203/rs.3.rs-5953682/v1

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Incidence of Ascaris ssp in United Mexican States’ population for twenty years (2003-2022) and incidence prediction until 2030

https://doi.org/10.21203/rs.3.rs-5953682/v1

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Journal Publication

published 27 Jun, 2025

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Purpose

Soil-transmitted helminth infections affect people who live in areas with poor sanitation, low socioeconomical level. Ascaris lumbricoides is one of the most frequent parasites worldwide and in México. The General Directorate of Epidemiology reports data related to infections weekly, and this study was based on that. The aim of this study was to analyze the SINAVE data for twenty years (2003–2022) to assess the incidence of ascariasis in the United Mexican States.

Methods

We conducted a retrospective observational analysis of ascariasis from January 2003 to December 2022, classifying data by year, age group, state gender, and season. A predictive model was used to estimate the new cases until 2030.

Results

From 2003 to 2022, the total number of new cases registered in the whole country decreased by 81.2%. The geographical distribution of the new cases was more pronounced in the Neotropical region of Yucatan, Tabasco, and Chiapas States. Women and infants from 1 to 9 years old exhibited the highest incidence. The prediction model showed that in 2030, there will be an incidence higher than 15000 new cases in the United Mexican States.

Conclusions

This work indicates that Ascaris infection tends to decrease, which could be related to hands hygiene and the look down during the COVID-19 pandemic.

Ascaris

ascariasis

epidemiology

United Mexican Sates

incidence

Soil-transmitted helminth (STH) is a group of parasites that provoke infections affecting approximately 25% of the global population worldwide, primarily people living in areas deprived of clean water, hygiene, and sanitation. Ascariasis is a tropical disease caused by Ascaris spp., first described by Linnaeus in 1758 (1). Ascaris spp. is an intestinal parasite transmitted by ingesting embryonated eggs from soil (2), water, or food; the eggs can remain infective for years (3). Ascaris spp. is one of the most frequent parasites worldwide, with 4.46 × 10⁶ prevalent infections; in 2019 the global burden was 8.78 × 10⁶. Disability adjusted for life years in low- and middle-income countries. The incidence and prevalence of infections may be underestimated because, in some countries, it is not required to notify public health systems of new infections. A higher prevalence of high-intensity infections has been reported in the Caribbean and Latin American regions (approximately 8.4%). The most common identification method is egg detection using a light microscope. In endemic areas, the World Health Organization (WHO) recommends the Kato-Katz thick smear for STH infection detection (4). The intensity is the number of eggs per gram of stool (EPG) and can be light, moderate, and heavy. The intensity can also be calculated by determining the adult worms expulsed after treatment and is expressed as the number of eggs per gram of excrement. It has been observed that reinfection post-treatment leads to predisposition in some individuals (5) or is linked to a lack of hygiene and poverty (6). Ascaris lumbricoides and Ascaris suum, which infects pigs, are very similar. It is impossible to distinguish between these species by morphological examination; they differ only in their mitochondrial genome (7), rDNA, and the first internal transcribed spacer (8). It has been described that children can have higher worm loads, more than adults, causing stunting, anemia, and fitness reduction (9, 10, 11). Ascaris spp. in children, can provoke obstructions in the ileum but in adults, it block the bile and pancreatic ducts (12, 10). However, infections can be either asymptomatic or accompanied by abdominal pain, anorexia, vomiting, nausea, and, in many cases, intermittent diarrhea (13). United Mexican States has three biogeographic provinces: nearctic, neotropical, and transition zones, which are delimited by the transversal volcanic system. This orography makes it possible to distinguish ecological regions with different temperatures and humidity. Ascaris spp. is a common parasite prevalent in areas with hot climates. Literature reports Ascaris spp., on states located in the neotropical zone of United Mexican States. However, parasites can survive in areas with template climates.

Additionally, poverty levels in some communities are remarkably high, as seen in houses without clean water on a dirt floor and no wastewater disposal systems. This contributes to the prevalence of Ascaris spp. numerous reports have described the prevalence of Ascaris spp. in United Mexican States. Studies in the localities where the investigations were conducted in the last 25 years, revealed that the prevalence varied between 4.5% and 73.9%. Ascariasis is classified as an infectious parasitic disease of the digestive system, and the positive cases must be documented weekly (NOM-017-SSA2-2012)(14). Zavala et al. analyzed the 2010 data from the National System for Epidemiological Surveillance (SINAVE) and found that the incidence of ascariasis was higher in the country's southeast (15). However, there are also reports of low incidences in communities of Chihuahua State, which have areas with cold or template climates. The present study analyzed data from SINAVE for 20 years (2003–2022) to assess the incidence of ascariasis in the United Mexican States, and a model was built to predict the ascariasis incidence in ten years.

The General Directorate of Epidemiology (GDE) collects data obtained from different sources and publishes weekly epidemiological surveillance reports. Epidemiological data for the study period were obtained from morbidity reports by SINAVE and are publicly available (https://www.gob.mx/salud/acciones-y-programas/anuarios-de-morbilidad-1984-a-2023). All data were statistically analysed by age and state, and a three-way analysis variance was calculated to determine significant differences (16). We used a three-way analysis of variance (ANOVA); for the factors of sex, age, and year and the Ryan–Einot–Gabriel–Welsch multiple F test (13) for data on the number of cases of ascariasis with 440 observations. In all cases, α = 0.05. All statistical data were analyzed using SAS/STAT software version 9.4 (SAS Institute Inc.).

The information provided for the new cases from the year 2003 to 2022 was captured and analyzed using the program OriginPro 2018. Once the data was introduced in the program, and observing its fast-decreasing tendency, an exponential curve fitting was used to obtain a characteristic equation which could model the data and predict the number of new cases in coming years. The exponential curve chosen for the fitting is given by the equation: y = y₀ + Ae^(R0*x). The iteration algorithm used was the Levenberg Marquardt model (17), a standard method used to solve non-linear least square problems. The number of interactions used were 5000 to find convergence with a tolerance of 1e-9 with the objective to minimize the difference between the given data and the model’s curve. Once the fitting was performed a curve was obtained and the values given by the curve fit, the characteristic equation for the model can be written as:

y = 13876.84792 + 2.37482E134* e^(-0.14837x), where y is the number of cases, and x is the given year. The values obtained, were plotted alongside the known data to observe the behavior of the algorithm on a short-term period. Finally, correspondent plot was obtained.

Global cases and incidence of ascariasis

In United Mexican States several studies reported the prevalence of ascariasis. The National Directorate of Health established that notification of ascariasis cases is mandatory. An analysis of 20 years revealed 224884 new cases in 2003, a reduction trend in 2016 (81%), a slight increase of 6% in 2017, and an abrupt decrease to 90% during the pandemic period. A direct relationship was detected between the number of new cases per year and incidence. The incidence decreased from 215.8 in 2003 to 34.91 in 2016, but it was 18.48 in 2022 (Fig. 1). In 2023 were documented 22051 new cases.

Geographic distribution of ascariasis

In this study the geographic distribution of ascariasis was analyzed in the entire country for 20 years. The lowest median incidence was observed in Baja California Norte, which is characterized by arid zones with low precipitation. The highest median incidence (2.49 ± 1.88) was documented in Yucatán, a southeast country state in México. Nayarit, Colima, Guerrero, Oaxaca, and Chiapas are located on the Pacific coast of Mexico, Veracruz, and Tabasco in the Gulf of Mexico, and Campeche, Yucatan, and Quintana Roo in the Yucatán Peninsula. Yucatán and the other nine states with high incidence are located in the neotropical region, where the temperature is generally > 18°C and the mean annual precipitation is > 1800 mm. The northern parts of Veracruz, Tamaulipas, Hidalgo and the north of Puebla, and San Luis Potosí belong to the region named La Huasteca. The climate is: semi-warm, humid with abundant rain in summer, temperate subhumid, and warm subhumid with rain in summer and early autumn. Sinaloa, a state on the Pacific coast, also had a medium to high incidence rate. The climate in these areas is suitable for Ascaris spp. life cycle development. The lowest incidence rate was observed in the northern states belonging to the nearctic region located above the transversal volcanic system, which is characterized by a dry climate (Fig. 2).

Incidence of ascariasis per age group and gender

The analysis according to gender indicates that ascariasis cases were higher in females (p = 0.009) all age groups but in the 10–14 age group. However, in women aged between 25 and 44 years, the difference between men and women was very high, 1635.1 ± 565.08 and 3207.7 ± 1119.84, respectively. The analysis of new cases of ascariasis by age group revealed that infants aged 1–9 years had the highest incidence (p < 0.0001). The median incidence in children aged 1–4, 5–9, and 10–14 years old was 20837.3 ± 15914.58, 21438.95 ± 15486.44, and 13181.25 ± 9722.59 (per 100,000 inhabitants), respectively. In adults, the incidence is higher in people aged 24–49 years, which corresponds to economically active individuals (Fig. 3).

Predictive model

The PAHO aims to end with ascariasis and related conditions by 2030, then to know if it will be possible to reach the goal, we elaborated a prediction’s model. The number of future cases until the year 2030 was estimated with the equation obtained (Fig. 4). By the year 2030, the number of cases estimated will be around 17500, the point in which the model begins to reach an asymptote. The used model was then deemed adequate to predict the number of cases for a short period of time, as the model adjusted itself well to the data sets given, and showing that in years to come, the number of cases won’t decrease by much.

Ascariasis has higher prevalence in areas with subtropical and tropical climates (1). The World Health Organization estimated in 2021 that 5–19 million children in United Mexican States required chemotherapy to prevent these infections. To prevent the transition of ascariasis, the government established the Semana Nacional de Salud (National Health Week), and also communicated that all children aged between two and fourteen years old would receive only one dose of albendazole as preventive action (18). In United Mexican States, the parasitological examination is according to PAHO (19). However, the selection depends of each laboratory and the Kato-Kats is used only eventually, since, this technique is specific for helmits and in our country we also have a high prevalence of protozoan parasites. WHO aims to eliminate the mobility caused by parasites by 2030, including those transmitted by vectors and helminths such as A. lumbricoides, Trichuris trichura, Ancylostoma doudenale, and Necator americanus and Strongyloides spp. Nonetheless, our predictive model showed that in 2030 in our country there will be an incidence higher that 15000 new cases. Ascariasis has a high prevalence in children and causes anaemia, stunting, fitness reduction, and intestinal obstruction in some cases. This 20-year retrospective analysis (2003–2022) shows the prevalence of Ascaris spp as determined by GDE reports in United Mexican States. The number of cases decreased from 224884 to 41,229 between 2003 and 2019. A second wave of reduction was detected from 2019 to 2020; this dramatic decrease could be caused by lockdowns during the COVID-19 pandemic, as observed in Turkey (20), or compliance with hands hygiene as described by Seid et al. (21), who analyzed a patient population with good hygiene attending a hospital during the pandemic and compared with a control group with poor hands hygiene, and it was observed a reduction of intestinal parasitic infections in patients with good hygiene practices. The geographical distribution of new cases showed a higher incidence in the neotropical region. This distribution is similar to the incidence reported in 2010 by Zavala et al. (15). They found the highest values in the southern states. We found that the state with the highest incidence was Guerrero (371.57 ± 205.25). The second higher incidence was detected in Yucatán (354.6 ± 249.89). In 2001, in a cross-sectional study in a village near Merida, it was found 73.9% of samples had A. lumbricoides, and the age group with higher prevalence were children aged 1–10 years (6). We also found a high incidence in Tabasco State, which is located in the neotropical region with a high level of annual precipitation; the weather is warm and humid, conditions that promote helminths egg development. Pous–Gaona et al. (22) reported in a retrospective study (review of medical files) conducted over 2 years in a hospital in Villahermosa, and they found 1965 cases reporting Giardia intestinalis and A. lumbricoides in children attending kindergarten and elementary school. Chiapas State is in the South of the country. The population is pluricultural and consists of 25% of indigenous people. Areas like these often face educational backwardness and low access to health and essential services. Several studies have been conducted in Chiapas State. A study of children performed in 32 communities near Guatemala’s border showed a 67% of parasitosis prevalence, but 14.5% was for A. lumbricoides (23). Conversely, Gutiérrez–Jiménez (24) analyzed 250 samples from children younger than 5 years and found that A. lumbricoides was a more prevalent parasite (33.6%). Also, Cruz–Cruz detected (106 Scholl–age children) A. lumbricoides and a prevalence of 25.5% (11). Additionally, a study conducted in the Chiapas highlands reported 57.1% (N = 84) of A. lumbricoides prevalence (25). Veracruz State is in the Gulf of Mexico; in many areas, the climate is humid and warm. In Coapeche Veracruz, Flisser et al. analyzed fecal samples and detected them by coproparasitoscopic tests. A. lumbricoides was detected in 9% of the samples (26). Our analysis also found a high incidence on the west coast in Nayarit, Colima, Guerrero, and Oaxaca States, all of which belong to the neotropical region. When Nayarit Indigenous and mestizo populations were analyzed, a prevalence of 6.9% was identified (27). In Colima, a study was performed in three cities in one year, 677 children were selected at random (338 girls and 339 boys), and their faces were analyzed, and the frequency for A. lumbricoides was 12.4% (28). Additionally, in an analytical-cross-over study conducted in Comala Colima, 243 samples were drawn from children, of which, 6.9% had Ascaris lumbricoides (29). Conversely, Quihui et al. compared five communities in a cross-sectional study in Oaxaca State and found a low prevalence of A. lumbricoides (30). In this analysis, new cases of ascariasis were observed all over the country, even in Chihuahua State, located in the North. In a prospective comparative ecological study conducted in 2011, Monárrez–Espino identified Ascaris lumbricoides in boarding schools in Kirare Chihuahua, where the climate is warm (31). Embryonated eggs are believed to survive and develop even in cold climates. This was reported in the USA, where A. lumbricoides was detected in central Appalachia (32). Although the detection of Ascaris spp. should be reported weekly, it may be omitted if the identification is conducted in laboratories that do not belong to the government health system. Additionally, in many indigenous communities, abdominal pains are treated with plant infusions. Further studies need to be done to determine the actual incidence of ascariasis.

Acknowledgments

All the authors thank to CONAHCyT SNI. León-Avila and Nogueda-Torres thank to COFAA and EDI IPN.

Dataset availability

No datasets were generated or analyzed during the current study.

Ethics approval

Non applicable

Consent to participate

Not applicable.

Consent for publication

Not applicable.

Conflict of interest

The authors do not have conflict to declare.

Author contribution

JMHH and GLA analyzed the data and wrote the manuscript. GIC and BNG analyzed the data. MCN, DFD and ACV analyzed the data and performed the statistical analysis.

Funding

This work was supported by A CONAHCyT doctoral scholarship granted to María Elizabeth Reséndiz-Juárez and Ana Laura Rosas-Soto, a postdoctoral scholarship to Fanny Rodríguez-Cruz, SIP20230565, and CONAHCyT CBF2023-2024-2528 granted to Gloria León-Avila.

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You are reading this latest preprint version

Incidence of Ascaris ssp in United Mexican States’ population for twenty years (2003-2022) and incidence prediction until 2030

Status:

Journal Publication

Version 1

Abstract

Purpose

Methods

Results

Conclusions

Figures

INTRODUCTION

MATERIALS AND METHODS

RESULTS

Global cases and incidence of ascariasis

Geographic distribution of ascariasis

Incidence of ascariasis per age group and gender

Predictive model

DISCUSSION

Declarations

References

Additional Declarations

Status:

Journal Publication

Version 1