The aim of this study was to estimate the frequency of seropositivity to IgM and IgG antibodies in pregnant women against T. gondii treated in the health services of the “Lagunera” region of Durango State, since there were no data of the prevalence of toxoplasmosis in the “Lagunera” region of Durango State. The low seroprevalence of this study is possibly due to climatic conditions, type of food consumption and behavioral habits of the population. Climatic conditions affect oocyst survival.
In our study three seropositive pregnant woman belong to urban and one to rural area this difference can´t be considered as important due to the “Lagunera” region of Durango being a cattle and agriculture zone where meat consumption is very frequent and generally local meat is consumed. Rural and urban areas in the “Lagunera” region of Durango are very similar, both are characterized by dust swirls which cover the area, raising and spreading oocysts through, making it difficult to know their main source; this will be considered for a future study.
T. gondii infection in general, and in pregnant women in particular, has been previously studied in Mexico. In 1992 a national survey of the general population showed that infection by T. gondii is present throughout the country (6). The prevalence varied according to the geographical area, with the northern zone being the lowest in relation to the prevalence. In the present study, a seroprevalence of IgG antibodies against T. gondii of 0.91% was determined, a result much lower than that found in 1992 by Velasco et al. (6) in the northern region of the country, where they obtained an 11.5% prevalence for an active infection; specifically in the State of Durango, a prevalence of 9.6% was found with a prevalence of 22.1%, similar only to Tamaulipas State. In 2012 Caballero-Ortega et al. (7) took a serum bank provided for the National Health Survey 2000 and the National Health and Nutrition Survey 2006 contrasting with the national toxoplasmosis prevalence of 1987, and the climatic changes in Mexico during 1987, 2000 and 2006 but no correlation was found with temperature and precipitation. Nonetheless, a significantly positive correlation with temperature and seroprevalence was found in 21 states, which adjusted prevalence in 2000 and 2006 Durango State had 20-29% and 60-69% respectively. This is particularly interesting since this study’s seroprevalence was 0.94% in a small area of Durango State, differing from the global prevalence in the State in 2006 of 60-69%. This could be due to Durango having a geographical diversity, since in its territory sits west in the plateau region, a sub-humid weather with abundant rains and forests; in the north, a desert zone, where the “Lagunera” region is located; and to the east plains which has a dry semi-warm and semi-dry temperature, where Durango city is located. The different climates could explain the great differences in prevalence among this State.
In 2006 a similar study was carried out in the city of Durango, Durango by Alvarado-Esquivel et al. (10), seroprevalence of antibodies against T. gondii in pregnant women was reported in the general hospital of Durango city; sample size was 343 pregnant women unlike this study with 434 pregnant women. The seroprevalence of IgG and IgM antibodies were 6.1% and 0% respectively. Alvarado-Esquivel et al. argues low prevalence of antibodies IgM and IgG type against T. gondii is due to low socioeconomic level, low consumption of meat and high temperatures of Durango city during the day. However, the risk factors evaluated were living in houses with soil floor, living in rural areas and consuming turkey meat; unlike his study where the majority of the population studied were living in houses with firm floor, belonged to an urban area and consumed dried meat and other types of meat; where consumption of dry meat and consumption of other types of meat turned out to be a risk factor associated with this disease in the studied population. It should be noted that distance between Gómez Palacio and Durango is approximately 200 kilometers, which results in differences such as habits of the population of Durango that differ from this study in the consumption of turkey meat, number of people who had a soil floor and weather. Durango is in a valley unlike the “Lagunera” region of Durango, which is a semi-desert zone, that could explain the difference in the frequency of IgG antibodies with respect to this study affecting possibly survival of T. gondii by the increase in temperature of environment which implies a subsequent investigation to this work.
Recently, in a study carried out in 2016 by Alvarado-Esquivel et al. (11) in the city of Aguascalientes, Aguascalientes on pregnant women in three health services centers of Aguascalientes State, a seroprevalence of IgG and IgM antibodies against T. gondii was found of 6.2% and 4.8% respectively. The sample size of that study was 338, unlike our sample of 434 pregnant women; and the variables studied were very similar, differing from having abdominal pain, memory loss, hearing loss and had suffered from hepatitis. One of the possible explanations that the authors give to the low seroprevalence is due to the climatic conditions of the city of Aguascalientes, which has a semi-arid climate and an annual rainfall of 500 mm; an explanation very consistent with this study since, very similarly, the city of Gómez Palacio has a semi-arid climate but an average annual rainfall of 250 mm, which contributes greatly to the survival of T. gondii in the soil. The risk factors evaluated were white ethnicity, low educational level (0 - 6 years), not eating out of home, not washing hands and using latrines. It should be noted that in this study, prevalence was associated with consumption of dry meat and other types of meat, which indicates that toxoplasmosis is acquired by the consumption of tissue cysts, unlike Alvarado-Esquivel et al. 2016 study, where association of seroprevalence of toxoplasmosis was due to habits of population, which suggests that there is an infection directly by land containing sporulated oocysts; the authors argue that not washing hands before eating (7.1%) and the use of latrines (2.36%) are risk factors that reflect poor hygiene and cleanliness of the studied population, facilitating ingestion of T. gondii oocysts; risk factors found in this study represent 2.53% of people who had bad HCI, which means that their homes had a soil floor, use of latrines, public hydrant water and/or overcrowding, as well as 12.9 % of people who do not wash their hands before eating (not showed data), however in this study there was no association to these risk factors with T. gondii infection.
In respect to international prevalence of toxoplasmosis in pregnant women, seroprevalence of this study is lower than reported in Zambia by Frimpong et al. in the year 2017 (12) of 5.87% of IgG antibodies and 0% of IgM antibodies. Another study conducted in France by Tourdjman et al. in 2015 (13) reported a prevalence in 2010 of 36.7% higher than reported in this study. In the United States (4) in 2001, the seroprevalence of IgG antibodies against T. gondii was reported in women of reproductive age (15 to 44 years) of 15% and a study conducted from 2011-2014 the same author et al. (14) reported a prevalence of 7.5% of IgG antibodies against T. gondii. In Norway Findal et al. in 2015 (15) they reported a seroprevalence of IgG antibodies against T. gondii of 9.3%. Another study in Korea by Song et al. in the year 2005 (16) showed a prevalence of 0.79%, similar to that reported in this work of 0.92%. In the search for information only the study conducted by Song et al. was the only one who reported a similar prevalence to this study.
Dubey in 1998 examined oocyst survival according to temperature, oocysts were rendered noninfective by storage for 62 days at 35 °C, 28 days at 40 °C, 2 days at 45 °C, 120 min at 50 °C, and 10 min at 55 °C (17). In the “Lagunera” region of Durango, the hot season usually lasts 4.2 months, from April to August, average daily maximum temperature is more than 33 ° C; in 2017 the hottest day had a maximum temperature of 42.6°C. Cool season lasts around 2.5 months, from November to February, and the average daily maximum temperature is less than 24°C. This could be detrimental to oocyst survival in soil and the possible explanation to low seroprevalence. Another possible explanation for the low seroprevalence in this study is due to behavioral characteristics of the population and the possible low prevalence of T. gondii in animals for human consumption, combined with the semi-arid climate of the region and the survival of the parasite in the soil, which are crucial factors for low seroprevalence in the area. For example, a study conducted in Colombia by Gomez-Marin et al. in 2011 (18), which aimed to determine incidence of congenital toxoplasmosis in Colombian newborns from 19 hospitals or health services in seven different cities of five natural geographic regions, had as a finding a significant correlation between precipitation average of each city and incidence of markers for congenital infection. Another study in domestic cats conducted in France by Afonso et al. in 2013 (19), where a correlation was found with the highest prevalence and years with coldest and wettest winters. Another study carried out in France by Morin et al. in 2012 (20) calculated seasonal variations of toxoplasmosis infection in pregnant women; it was observed that in rural areas the seasons with significantly less infections happened in the first half of the year but with maximum risks at the end of summer and at the end of autumn.
With regards to consumption of dried meat and other types of meat, there are studies which have associated the consumption of certain types of meat with T. gondii infection, such as the one carried out by Cook et al. in the year 2000 (21) where probability of infection in pregnant women was associated with consumption of undercooked lamb meat, beef and consumption of cured or dried meat. In another study, in which the objective was to know the risk factors of toxoplasmosis in the United States by Jones et al. (22), the adjusted OR’s were: eat raw beef 6.67, eat lamb 8.39, eat cured meat, dry or smoked 1.97 and work with meat 3.15. Another study, in 2015 carried out by Guo et al. (23) showed that raw fermented sausage, raw cured meat, meat that is not dried in hot air and fresh processed meat were associated with higher risks of exposure, compared to cooked meat and frozen meat. In this study 3 out of 4 pregnant women with IgG antibodies against T. gondii had eaten dried meat, which is consistent with the cited literature that associates the consumption of dried meat with T. gondii infection. To the date, there is no data available of toxoplasmosis studies in animals in the Comarca Lagunera of Durango; it will be very important to consider toxoplasmosis seroprevalence studies in animals like birds and mammals in the Comarca Lagunera of Durango as well to explore general population seroprevalence.
The results showed that pregnant women in the “Lagunera” region of Durango State have a very low seroprevalence of T. gondii infection, possibly due to the climatic conditions of the region and habits of the population. Due to the low seroprevalence, no risk factors were found conclusively associated with the infection in this population, but this work is useful to know some habits that could be considered as a risk in this population. However, this indicates that living in an area with a very low seroprevalence of toxoplasmosis, this population it has a low risk to acquire the infection but, the majority of the population studied is at risk of having a primary T. gondii infection.