Toxoplasmosis is a major public health problem. It is transmitted from mother to fetus via the transplacental route when acquired during pregnancy. Maternal-fetal transmission increases with gestational age, and the mode of contamination is influenced by lifestyle, the presence of felids in the environment, and the different dietary habits of each individual.

This condition, contracted in utero, can lead to potentially severe clinical sequelae in the fetus, such as cerebral complications (intracranial calcifications; hydrocephalus), ocular complications (chorioretinitis; optic atrophy) or visceral complications (hepatomegaly; jaundice) [1] .

The overall prevalence of Congenital Toxoplasmosis observed in France is around 2.6 per 10,000 births, and the prevalence of Congenital Toxoplasmosis cases diagnosed at birth is 1.35 per 10,000 births [2] .

Worldwide, an estimated 3.5 billion people are affected by toxoplasmosis, the prevalence of which depends on geographical, climatic and socioeconomic conditions [2] - [4] .

However, the size of the cat population, with infection rates ranging from 5.5% to 86%, the survival of oocysts in humid tropical climatic conditions, dietary habits and hygiene conditions, mean that human prevalence is highest in Africa and Latin America. In Africa, prevalence (60 to 80%) varies according to humid and forested areas (>60%) and dry or desert areas (<50%) [5] - [7] .

The worldwide incidence of Congenital Toxoplasmosis is estimated at 190,100 cases [7] . In France, since 2007, the CNR (Centre National de Référence de la Toxoplasmose), in collaboration with the InVS (Institut de Veille Sanitaire), has set up nationwide surveillance of this disease, with notifications of cases of Congenital Toxoplasmosis. In 2013, 204 cases of Congenital Toxoplasmosis were diagnosed in France.

In the Democratic Republic of Congo, seroprevalence among pregnant women was 80.3% in 2014 [8] .

Toxoplasmosis affects livestock and represents a major cause of abortions in cattle and sheep [9] - [11] . The resulting financial losses can be substantial for developing countries with agro-pastoral activities. Worldwide, the consequences of infecting 500 million farm animals with Toxoplasma gondii are estimated to cost around $3 million a year [9] - [11] .

In the United States, the estimated incidence of congenital toxoplasmosis ranges from 1/3000 to 1/10,000 births, and may reach 1.5 to 2.5/1000 births in certain parts of Africa [12] .

In humans, horizontal contamination occurs either through ingestion of oocysts on soiled food, soiled kitchen equipment or in drinking water, or through cysts in raw or undercooked meat [13] - [15] . Vertical, transplacental contamination occurs when tachyzoites infect the fetus during primary infection in pregnant women [16] .

Transplantation or blood transfusion from infected donors, and accidental inoculation via the cutaneous-mucosal route are also routes of contamination [17] .

In the Republic of Congo, several studies have been carried out on the prevalence of toxoplasmosis in pregnant women, including one by M. Makuwa et al. over a 5-year period from 1986 to 1990. This study revealed that the prevalence of toxoplasmosis in the Congo among 2897 women examined was 60% [18] . Another study conducted at Brazzaville University Hospital on the seroprevalence of toxoplasmosis in pregnant women by Sekangue et al. ranging from 2015 to 2016 showed a seroprevalence of 47.2% [19] However, we have no information on the effect that this parasite has on unborn children during toxoplasmosis in pregnant women in Congo Brazzaville, so we set ourselves the goal of assessing the prevalence of congenital toxoplasmosis in Congo Brazzaville.

Surveys in the health facilities showed an overall prevalence of toxoplasmosis in pregnant women of 49.78%.

The results showed that 693 blood samples from pregnant women were seropositive for toxoplasmosis, i.e. a prevalence of 49.78% out of a total of 1392 samples, with frequencies of 53.93%, i.e. 267 positive samples out of 495 blood samples from pregnant women at the Blanche Gomez hospital, 53.76% at the Luiz biomedical analysis laboratory, i.e. 321 positive samples out of 597 blood samples, and a frequency of 35%, i.e. 105 positive samples out of 300 blood samples from pregnant women at the OCH office ( Table 1 , Figure 2 ) The immunological profile found was IgG alone in 48.70 (226/464) of cases and IgG associated with IgM in 1.07% (5/464) of cases Table 1 . The average age of pregnant women was 30.

Seroprevalence of toxoplasmosis according to socio-demographic characteristics was highest among women aged 16 to 25 (57.14%), followed by women aged 26 to 35 (52.77%) ( Figure 3 ), 62.5% of women with anti-toxoplasmic antibodies had been in contact with soil, compared with 37.5% of seronegative women ( Table 2 ).

Among toxoplasmosis-seropositive pregnant women, 52.65% were meat eaters, while 66.66% of women in contact with cats were toxoplasmosis-positive, as shown in Table 2 . Frequency among pregnant women occupation shows that 43.29% were shopkeepers followed by students 35% as shown in Figure 4 .

Of the 9 cases of seroconversion, we diagnosed 6 cases of congenital toxoplasmosis, corresponding to an overall maternal-fetal transmission rate of 66.66% in our study.

we had a total of 6 cases of congenital toxoplasmosis with subclinical forms showing IgG persistence at one year of age, four of whom had thrombocytopenia associated with jaundice, and two others with hepatomegaly associated with hyper transaminase and hyperbilirubinemia. Among women with a negative IgM level, 74% had a high avidity, indicating an old infection, and 3.75% had a low avidity, indicating a recent infection likely within 4 months. In women with a positive IgM level, 3.75% had a low avidity, Table 3 .

Index avidity < 0.200 Recent infection, index avidity > 0.300% = Old infection and index avidity 0.200 - 0.300% Equivocal.

Of the 545 women to be enrolled, only 464 were able to be followed through to delivery. 81 women could not be included because some of them moved during the study period.

An overall seroprevalence of 49.78% was found in our study at the three sites, it is lower than that found by Wakuma, which was 60% [18] and close to that found by Sekangue et al., which was 47.2% at the CHU de Brazzaville [19] , the mean age in our study was 30 years, close to the 27 years found by Sekangue et al. [19] . This may be explained by the longer study period for Wakuma, the different analysis methods and the greater number of pregnant women included in the study, but also by preventive measures and better monitoring of pregnant women with systematic prenatal diagnosis in our health facilities today. It is higher than that found in Dakar in a study conducted by Ibrahim Mahamat Salle [20] which was 38.96%, it was 32.8% in a study conducted in Senegal in Saint Louis in 2012 but similar to that of Coulibaly in 2012 in Dakar which was 50% among women [21] and by Andrée Prisca Ndjoug Ndour in 2012 in Dakar 43.8%. The seroprevalence observed in France by Berger in 2003 was 44% [22] .

Among women with negative IgM and positive IgG, 74% had high avidity, indicating a long-standing infection, while 3.75% had low avidity, indicating a recent infection likely within 4 months. Among IgM-positive women, 3.75% had low avidity. These results are contrary to those found in Madagascar by Randriamahazo et al. [23] , who found that 40% of IgM-negative and IgG-positive women had high avidity, and 16.21% of IgM- and IgG-positive women had low avidity.

The seroprevalence of toxoplasmosis was highest among women aged 16 to 25 (57.14%), followed by women aged 26 to 35 (52.77%) ( Figure 3 ). This may be explained by the socio-economic level of these women, their lack of knowledge and lifestyle hygiene, and their dietary habits, which tend to gravitate towards embers. 62.5% of women with anti-toxoplasmic antibodies had been in contact with soil, compared with 37.5% of seronegative women. The presence of cats in the environment may be responsible for this result. Among toxoplasmosis-seropositive enceintes women, 52.65% were meat eaters, whereas 66.66% of women in contact with cats were toxoplasmosis-positive, contact with host animals, contact with uncooked meat and vegetable was a risk factor of contamination who where also mentioned by Al-Jebouri in Irak [24] and AlRashada in Saudi Arabia among female students [25] . This may be explained by the strong presence of stray cats in the neighborhoods, which are responsible for contaminating the soil, water and vegetables, and by the consumption of undercooked meats, particularly cold cuts and charcoal.

The percentage of seroconversion in our study was 1.07%, which is lower than that found by Sekangue et al. (2.8%), and by Wakuma (5.6%).

Out of 9 cases of seroconversion, 6 cases of congenital toxoplasmosis were confirmed, corresponding to an overall maternal-foetal transmission rate of 66.66% observed in our study. This result is lower than that found by Cyrille Wakieu between 2004 and 2011 [26] , which was 15 cases of congenital toxoplasmosis, also found by W. Ferguson et al. [27] .

This study of pregnant women in Brazzaville confirms the prevalence and activity of Toxoplasma gondii in the city. Unlike other studies based solely on seroprevalence in pregnant women, our study enabled us to diagnose cases of congenital toxoplasmosis linked to seroconversion in pregnant women during pregnancy, thus demonstrating the impact of contamination by the parasite on unborn children. The data obtained from this study have enabled us to gain a better understanding of toxoplasmosis in pregnant women, and to identify the main risk factors linked to contamination, which underlines the vital importance of serological over-surveillance of pregnant women, enabling us to detect and monitor non-immune women and progressive toxoplasmosis as early as possible, so that contaminated children can be cared for.

Congo Brazzaville is a low-income country whose socio-economic status is not conducive to better prenatal care. A diet that is more focused on undercooked meat, ember and dibiterie, which are recipes for dishes that are not well cooked, and the high presence of cats in our environment are risk factors that have an impact on the transmission of congenital toxoplasmosis. It therefore appears that many pregnant women with no anti-Toxoplasma antibodies are highly exposed to the risk of infection during pregnancy in this work 50.22% of women are at risk of primary infection. It is important to advise them to avoid eating undercooked meat, unclean water, unwashed market garden produce and contact with ruminant offspring, cat faeces and soiled soil.

Future studies will enable us to set up a method for diagnosing early congenital toxoplasmosis, in particular, the western blot during maternal and child check-ups, and to genetically characterize strains isolated during maternal and congenital toxoplasmosis.