Review On: Seroprevalence of Toxoplasma gondii Infection in Women of Child-Bearing Age Volume 53- Issue 4

Afrida Tabassum Trina, Priyanka Barua and Hamida Khanum*

• Department of Zoology, University of Dhaka, Bangladesh

Received: November 01, 2023; Published: November 13, 2023

*Corresponding author: Hamida Khanum, Department of Zoology, University of Dhaka, Dhaka 1000, Bangladesh

DOI: 10.26717/BJSTR.2023.53.008446

Abstract PDF

Toxoplasmosis is a zoonotic disease transmitted by the protozoan parasite Toxoplasma gondii. The disease is common worldwide due to its ability to infect a wide range of warm-blooded animals including humans. Areas with poor hygiene and infrastructure along with climatic conditions where the parasites tend to exist and most importantly unawareness of the presence of asymptomatic condition has caused a persistent prevalence of infection in women of childbearing age. This persistency later becomes the principal cause for congenital toxoplasmosis. Since more than 80% of immunocompetent individuals remain asymptomatic or exhibit only flu-like symptoms, a measure of seroprevalence can help to find any exposure to infection by identifying specific IgG and IgM antibodies. So, this review has been summarized to assess the prevailing seropositivity of T. gondii infection among women who are going through childbearing age of 15- 49 years and the possible associated factors behind this prevalence rate.

Keywords: Toxoplasma gondii; Congenital Toxoplasmosis; Seroprevalence; IgG; IgM Antibodies; Child-Bearing Age; Seropositivity; Rural Residency

Toxoplasmosis is a disease caused by the protozoan Toxoplasma gondii, which affects practically all warm-blooded animals, including humans, domestic animals, and terrestrial and marine wild animals. Susceptible hosts can be infected by T. gondii through the following primary forms: transplacental transmission, ingestion of animal tissues containing infective cysts, and the ingestion of water and food contaminated with cat feces containing sporulated oocysts. Toxoplasma gondii has a complex, facultatively heteroxenous life cycle that involves several stages of development and a range of hosts and environments. In humans, toxoplasmosis is often subclinical in immunocompetent adults; however, in immunosuppressed individuals, it can cause encephalitis and retinochoroiditis. In pregnant women, the parasite can be transmitted to the fetus, causing miscarriage or the development of chorioretinitis, intracranial calcifications and hydrocephalus in the fetus. In animals, T. gondii is responsible for causing miscarriage, fetal mummification, stillbirth and congenital disease, leading to economic losses and increasing production costs (Deganich, et al. [1]). It can also occur subclinically in immunocompetent animals. This characteristic, in addition to making diagnosis difficult, puts human health at risk since it allows the presence of chronically infected animals and facilitates the slaughter of infected animals for human consumption. The consumption of raw or undercooked meat and raw milk is a source of infection for humans.

Because of this, it is important to know the spread of this protozoan, which can be identified through seroprevalence surveys. Furthermore, the description of the genetic variability of T. gondii with genotypic characterization studies is also very important for understanding its pathogenicity and virulence. The importance of this genetic knowledge is justified to try to establish a relationship between the genotype and the clinical manifestations, as well as possible associations such as the biological potential of the species, virulence, infectivity, and drug and vaccine resistance. One of the most successful intracellular apicomplexan protozoan parasites is Toxoplasma gondii, responsible for causing the worldwide zoonotic infection toxoplasmosis. The parasite is capable of infecting warm-blooded animals with more than 30 species of birds and 300 species of mammals (Flegr, et al. [2]) as well as humans. All of them serve as intermediate hosts while cats and other animals belonging to the family Felidae act as the definitive hosts. The non-infectious oocysts shed by the felids in their feces become infectious after sporulation and persist in water or soil for a prolonged period of time (Schluter, et al. [3]). Infection occurs from ingestion of contaminated soil, water or plant material by the intermediate hosts that helps the oocysts to settle in the neural and muscular tissue where they transform into tissue cysts. Cats acquire infections by consuming the intermediate hosts or directly by ingesting the sporulated oocysts.

This heteroxenous life cycle of T. gondii has created quite a number of routes for transmission in humans. Another principal route of infection is transplacental transmission from a newly infected pregnant woman to her fetus resulting in congenital toxoplasmosis (WHO, [4,5]). Congenital toxoplasmosis has devastating effects on the unborn child if left untreated. Miscarriage still births or congenital defects in the eye and the central nervous system are the potential consequences of primary infection in pregnant women (Montoya, et al. [6]) which occurs due to colonization of tachyzoite stages of T. gondii in placental tissues that make their way to the fetal compartment in nearly 30% cases (Robert-Gangneux, et al. [7]). Congenital diseases can later result in cerebral calcification, hydrocephaly, chorioretinitis and mental retardation (Koppe, et al. [8]). More than 80% of immune-competent individuals remain asymptomatic or only show flu like symptoms when they come across an infection (Robert-Gangneux, et al. [7]). So, a measure of seroprevalence can reflect the exposure to infections. Seroprevalence is the detection of the percentage of individuals in a population having antibodies against an infectious pathogen by testing their blood serum. The samples that come out positive for specified antibodies imply the occurrence of previous exposure to that particular pathogen (CDC, [9]). The specific IgG and IgM antibodies are indicative of detecting Toxoplasma infection. Repetitive serological screening for IgG and IgM distinguishes between acute and chronic infections (Robert-Gangneux, et al. [7]).

Centre for Disease Control & Prevention recommends to run a test for IgG antibodies first for detecting immune status as a positive result points out infections of past exposure. Recent infection frequently forms IgM antibody first (Fricker-Hidalgo, et al. [10]) but the lack of specificity in IgM testing makes it difficult to diagnose the precise time of infection acquired. The extent of persistency of IgM antibody can be up to 18 months which lead to the false positive interpretation unless additional specific IgG antibody tests are done (Montoya, et al. [6]). 1-3 weeks later, an IgG antibody test is thus required to follow (Fricker-Hidalgo, et al. [10]). Vaccines for toxoplasmosis are still inaccessible due to a very high degree of antigenic polymorphism displayed by T. gondii. The only commercially licensed is the live attenuated Toxovax vaccine from S48 strain against congenital infection in sheep (Buxton, et al. [11]). But the maximum shelf-life limit of this costly vaccine is 10 days only (Dubey, [12]) with the potential to revert into its virulent form (Chu, et al. [13]). The trials undergone have demonstrated promising results towards the possibility of an effective vaccine development (Liu, et al. [14]). Usual medication guideline involves the use of a combination of Pyrimethamine and Sulfadiazine drugs along with Folinic acid (CDC, [15]). But the gradual increasing tendency of drug resistance is drawing concerns for treatment failure (Montazeri, et al. [16]). So, the best option left is to maintain preventive measures to reduce the chance of infection.

One such measure is the early diagnosis of infected women going through child-bearing age to prevent or monitor the probable congenital toxoplasmosis. The global estimation shows an approximation of 1.5 neonatal cases of congenital toxoplasmosis per 1000 births (Torgerson, et al. [17]). Though gestation period determines the risk and severity of infection (Robert-Gangneux, et al. [7]) in cases of maternal exposure, the asymptomatic nature of the infection leaves most of the women unaware whether they have acquired T. gondii infection or not. This signifies the necessity of prior detection of infection in women of childbearing age (Myla, et al. 2023).

The articles were searched primarily in Google Scholar by using the review title “Seroprevalence of Toxoplasma gondii in women of childbearing age” and other keywords “Toxoplasma gondii prevalence in women”, “Toxoplasmosis status in women”, which later directed to sites BMC infectious diseases, International Journal of Infectious Diseases, Journal of Parasitic Diseases, Parasite Journal, PubMed, Research Gate etc. A total of 10 articles have been reviewed from the publishing year of 2011-2021 and relevant data on seropravelence were collected. Most of these research articles also included associated risk factors and socioeconomic infrastructure related to the prevailing seroprevalence of the infection.

Data extracted from the articles selected for review have been summarized in the following tables of next page. The data have been categorized on the basis of the detected antibody type IgG, IgM or presence of both IgG and IgM in the samples along with statistically significant variables which have been considered to be potential associated factors. An estimation of overall prevalence of the studied areas have been tabulated as well. Seroprevalence data detected in the highest age category has been demonstrated in a separate table (Tables 1 & 2).

Table 1: Global overview of seroprevalence of Toxoplasma gondii in women of childbearing age.

Table 2: Seroprevalence based on the highest detected age group.

Most of the participants in these studies did not have prior knowledge about toxoplasmosis. Women living in the rural facilities were more exposed to infection for their involvement in agricultural work and lack the maintenance of proper hygiene and sanitation. The humid climate in some geographical locations is another important fact explaining the persistency of cysts in the environment. Women with history of miscarriage had a high prevalence depicting the severe effect of congenital infection. Socioeconomic infrastructure, lifestyle, housing type, food habits are some influencing factors for rate dissimilarities in different regions. One common issue was high seroprevalence with increasing age. Long time of exposure has been predicted to be the possible reason behind it (Myla et al. 2023). (Molan, et al. [18]) have estimated an overall range of global seroprevalence of human T. gondii infection as 0.5% to 87.7% with highest average rate of 61.4% in African countries. The chronological average seroprevalence rate for other continents are as follows: Oceania 38.5%, South America 31.2%, Europe 29.6%, North America 17.5% & Asia 16.4%. Maximum study sample included women with pregnancy status and child-bearing age. Only a handful number of works on human toxoplasmosis has been published in Bangladesh half of which date back to the 90’s. The most recent studies conducted had a sample size of less than 100. All the researches were narrowed into specified status like pregnancy and gyneco-obstetric problems. None of these fully included all categories of women of the childbearing age range (Rahman, et al. [19-31]).

Most of the studies included sample populations on a small scale and without continuous screening. So the data obtained doesn’t exactly demonstrate the crucial factors behind such seroprevalence. A trend to an increasing age related seropositivity has been observed over recent years but except for long exposure period, other prime cause has not been detected yet. Future studies need to address these points to overcome the knowledge gap. Bangladesh is lagging far behind on human toxoplasmosis research. There was no constant continuation among the works published until now so reliable data on the seroprevalence status of Bangladeshi women are unavailable which needs attention of the researchers.

1. Deganich M, Boudreaux C, Benmerzouga I (2023) Toxoplasma infection During Pregnency. Trop Med Infect Dis 8(1): 3.
2. Flegr J, Prandota J, Sovičková M, Israili ZH (2014) Toxoplasmosis–a global threat. Correlation of latent toxoplasmosis with specific disease burden in a set of 88 countries. PloS one 9(3): e90203.
3. Schlüter D, Däubener W, Schares G, Groß U, Pleyer U, et al. (2014) Animals are key to human toxoplasmosis. International Journal of Medical Microbiology 304(7): 917-929.
4. (2015) World Health Organization. Toxoplasmosis Fact Sheet.
5. (2018) Centers for Disease Control and Prevention. Parasites -Toxoplasmosis (Toxoplasma infection) Epidemiology & Risk Factors.
6. Montoya JG, Liesenfeld O (2004) Toxoplasmosis. Lancet 363: 1965-1976.
7. Robert-Gangneux F, Dardé ML (2012) Epidemiology of and diagnostic strategies for toxoplasmosis. Clinical microbiology reviews 25(2): 264-296.
8. Koppe JG, Loewer-Sieger DH, de Roever-Bonnet H (1986) Results of 20-year follow- up of congenital toxoplasmosis. The Lancet 327(8475): 254-256.
9. (2020) Centers for Disease Control and Prevention. What COVID-19 Seroprevalence Surveys Can Tell Us.
10. Fricker-Hidalgo H, Cimon B, Chemla C, Dardé ML, Delhaès L, et al. (2013) Toxoplasma seroconversion with negative or transient immunoglobulin M in pregnant women: myth or reality? A French multicenter retrospective study. Journal of clinical microbiology 51(7): 2103-2111.
11. Buxton D, Innes E A (1995) A commercial vaccine for ovine toxoplasmosis. Parasitology 110(S1): S11-S16.
12. Dubey JP (2009) Toxoplasmosis in sheep—the last 20 years. Veterinary parasitology 163(1-2): 1-14.
13. Chu KB, Quan FS (2021) Advances in Toxoplasma gondii Vaccines: Current Strategies and Challenges for Vaccine Development. Vaccines 9(5): 413.
14. Liu Q, Singla LD, Zhou H (2012) Vaccines against Toxoplasma gondii: status, challenges and future directions. Human vaccines & immune therapeutics 8(9): 1305-1308.
15. (2018) Centers for Disease Control and Prevention. Parasites –Toxoplasmosis (Toxoplasma infection) Treatment.
16. Montazeri M, Mehrzadi S, Sharif M, Sarvi S, Tanzifi A, et al. (2018) Drug resistance in Toxoplasma gondii. Frontiers in microbiology 9: 2587.
17. Torgerson PR, Mastroiacovo P (2013) The global burden of congenital toxoplasmosis: a systematic review. Bulletin of the World Health Organization 91: 501-508.
18. Molan A, Nosaka K, Hunter M, Wang W (2019) Global status of Toxoplasma gondii infection: systematic review and prevalence snapshots. Trop Biomed 36(4): 898-925.
19. Rahman T, Rahman A, Chakraborty S (2018) Infection of Toxoplasma gondii in humans and livestock animals: an emerging silent threat for Bangladesh. Open Journal of Medical Microbiology 8(04): 109.
20. Alvarado-Esquivel C, Corella-Madueno MAG, Hernandez-Tinoco J, Rascon-Careaga A, Sanchez-Anguiano LF, et al. (2018) Sero epidemiology of Toxoplasma gondii infection in women of reproductive age: A cross-sectional study in a Northwestern Mexican city. Journal of clinical medicine research 10(3): 210-216.
21. Doni NY, Simsek Z, Gurses G, Zeyrek FY, Demir C (2015) Prevalence and associated risk factors of Toxoplasma gondii in female farmworkers of southeastern Turkey. The Journal of Infection in Developing Countries 9(01): 87-93.
22. Fanigliulo D, Marchi S, Montomoli E, Trombetta CM (2020) Toxoplasma gondii in women of childbearing age and during pregnancy: seroprevalence study in Central and Southern Italy from 2013 to 2017. Parasite 27: 2.
23. Fricker-Hidalgo H, Cimon B, Chemla C, Dardé ML, Delhaès L, et al. (2013) Toxoplasma seroconversion with negative or transient immunoglobulin M in pregnant women: myth or reality? A French multicenter retrospective study. Journal of clinical microbiology 51(7): 2103-2111.
24. Gebremedhin EZ, Abebe AH, Tessema TS, Tullu KD, Medhin G, et al. (2013) Sero epidemiology of Toxoplasma gondii infection in women of child-bearing age in central Ethiopia. BMC Infectious Diseases 13(1): 1-9.
25. Kareshk AT, Keyhani A, Asadi A, Zia-Ali N, Mahmoudvand H, et al. (2016) Seroprevalence of Toxoplasma gondii infection among childbearing age women in Kerman city, southeastern Iran. Journal of parasitic diseases 40(4): 1544-1547.
26. Lopes AP, Dubey JP, Moutinho O, Gargaté MJ, Vilares A, et al. (2012) Seroepidemiology of Toxoplasma gondii infection in women from the North of Portugal in their childbearing years. Epidemiology & Infection 140(5): 872-877.
27. Mihu AG, Balta C, Marti DT, Paduraru AA, Lupu MA, et al. (2020) Seroprevalence of Toxoplasma gondii infection among women of childbearing age in an endemic region of Romania, 2016–2018. Parasite 27: 59.
28. Montazeri M, Mehrzadi S, Sharif M, Sarvi S, Tanzifi A, et al. (2018) Drug resistance in Toxoplasma gondii. Frontiers in microbiology 9: 2587.
29. Obaidat MM, Al-Sheyab NA, Salman AB, Lafi SQ (2015) Sero epidemiology and risk factors of Toxoplasma gondii infection in undergraduate university female students in Jordan. Epidemiology & Infection 143(9): 1898-1903.
30. Akinwale OP, Gyang VP, Nwafor T, Olukosi AY, Chang JH, et al. (2021) Toxoplasma gondii infection: seroprevalence and associated risk factors for women of childbearing age in Osun State, Nigeria. Pathogens and Global Health 116(1):59-65.
31. Panazzolo GK, Kmetiuk LB, Domingues OJ, Alexander Welker Biondo, Giovani Marino Fávero, et al. (2023) One Health Approach in Serosurvey of Toxoplasma gondii in Former Black Slave (Quilombola) Communities in Southern Brazil and Among Their Dogs. Trop Med Infect Dis 8(7): 377.