Seroprevalence of Toxoplasma gondii IgG and IgM antibodies and associated risk factors in women of child-bearing age in Njinikom, NW Cameroon

Toxoplasmosis is one of the common worldwide parasitic zoonosis, caused by the apicomplexa protozoan Toxoplasma gondii [1]. This parasite has cats as the definitive host, and warm-blooded animals as intermediate hosts [2]. T. gondii infects up to a third of the world’s population [3] and is reported to be an opportunistic parasitic infection in immune compromised hosts [4]. High prevalence of the infection has been reported among pregnant women and women of childbearing age from different parts of the world [5]. The infection occurs widely, and varies depending on social and cultural habits, geographic factors, climate, and route of transmission. It has been reported that the prevalence is higher in warm and humid areas [6].

Toxoplasma gondii is transmitted to humans through ingestion of oocysts in water, food or soil contaminated with cat’s faeces, or by eating raw or undercooked meat containing cysts [7–10], and women can transmit the infection through the placenta to their unborn foetus. Other infectious pathways are blood transfusion, and organs transplantation [11].

In the majority of immune competent subjects, the infection is asymptomatic [3, 12] and frequently results in the chronic persistence of cysts within the host tissues. The cysts normally lie dormant, probably for life [12]. But, in immune compromised states such as in HIV infections, subjects are at risk of developing acute toxoplasmosis due to reactivation of the organism if their CD4 cell count decreases below 200 cells/μL [13–15]. Moreover, in up to 10 % of HIV-infected immune compromised individuals, it causes cervical lymphadenopathy or ocular disease [16]. When the infection occurs in pregnant women, it can cause severe disease symptoms including toxoplasmic encephalitis, blindness, foetal abnormalities, abortion and even stillbirth [3, 17]. Toxoplasmosis has also been proven to be the cause of abortion and infertility in women [18].

In Cameroon, the few studies on toxoplasma have been limited to urban areas. For example, the seroprevalence of T. gondii was shown to be high among HIV/AIDS patients in the Yaoundé teaching hospital (69.9 %) [19] and pregnant women who consulted at the Department of Gynaecology in the Douala general hospital (70 %) [20]. 71.8 % prevalence was also observed among women attending antenatal care in Limbe, along the coastal region of Cameroon [21]. The study in Douala observed that the consumption of raw vegetables and untreated water were the main risk factors associated with toxoplasmosis in pregnant women [20].

The aim of this study was therefore to determine the seroprevalence of anti-T. gondii antibodies in HIV-infected and uninfected women of child-bearing age attending the antenatal clinic and medical check-ups and to identify the risk factors associated with T. gondii infection, within the rural locality of Njinikom, North West Region of Cameroon.

Toxoplasmosis is a curable but potentially fatal disease [22]. Over the years, infection with the protozoan parasite Toxoplasma gondii has been proven to be one of the most common parasitic infections of man and other warm-blooded animals [2]. In this study, we sought to investigate Toxoplasma infection, as evidenced by anti-Toxoplasma antibodies in the serum of women of child bearing age in a rural locality in Cameroon. Our findings revealed that the seroprevalence of anti-T. gondii antibodies among the women of child-bearing age in this study was 54.5 %. This prevalence was similar to that obtained among women of child-bearing age in Timis, Romania (57.6 %) [23], but far lower than that found in women of child-bearing age in Central Ethiopia (81.4 %) [24]. This lower prevalence could be attributed to a lower cat density (10/178, Table 1) and consequent oocysts shedding and a lower consumption of unpasteurised milk in our study area. The seroprevalence obtained in this study is also far lower than that obtained in other parts of Cameroon. Indeed, a prevalence of 77.1 % was observed in pregnant women in Yaoundé [25], 70 % in pregnant women in Douala [20], 69.9 % in HIV/AIDS patients in Yaoundé [19], while a prevalence of 71.8 % was observed among pregnant women in Limbe [21]. These geographic differences in prevalence rates may be explained by differences in rural/urban setting since exposure and the main sources of infection appear to be the same. This might explain differences in risk factors of Toxoplasma seropositivity as well as climatic changes. Our study population was mainly from a rural area.

The seroprevalence of anti-T. gondii IgG antibody in HIV-positive participants was 47.8 % (43/90). This was not significantly different from the 48.9 % (43/88) obtained in the HIV-negative group in this same study population (X ² = 1.3632, p = 0.1728). This results were similar to the 42.1 % (56/133) obtained among HIV/AIDS patients in the university teaching hospital in Yaoundé [19], although the number of HIV patients in our study was smaller. Similarity in the prevalence of Toxoplasma seropositivity among HIV-infected or uninfected women in our study conforms to what has been reported by researchers in Malaysia [26], United States of America [27], and Ethiopia [28]. However, another study in Ethiopia showed a significantly higher prevalence of anti-Toxoplasma gondii antibodies (87.4 % vs 70.29 %, P = 0.003) in HIV-positive pre-antiretroviral therapy (pre-ART) individuals than in HIV-negative blood donors [10]. Indeed, in our study, up to 84.5 % (76/90) of the HIV positive study participants were on highly active antiretroviral therapy (HAART), and only three participants had CD4 counts less than 200cells/mm3 of whole blood. This indicate the benefit of HAART treatment which helps to decrease the viral load and improve CD4+ cell counts and consequently boosts the immune system of the host, with the added benefit of reducing the likelihood of reactivation of latent T. gondii infections [1, 29, 30]. We found a non-significant higher IgM antibodies in HIV positive women compared to HIV negative women, further confirming this assertion.

The seroprevalence of anti-T. gondii antibodies was higher in non-pregnant women (55.7 %, [49/88]) compared to pregnant women (53.3 %, [48/90]) irrespective of HIV status, although not significantly different. Among the 90 pregnant women enrolled in this study, 48.9 % (44/90) and 13.3 (12/90) were positive for anti-T. gondii IgG and IgM antibodies respectively. These prevalence values were significantly low compared to 71.8 and 67.6 % respectively obtain among pregnant women in the Limbe health district in the South West Region of Cameroon [21].

The consumption of raw or undercooked meat [p = 0.0184] was significant a risk factor associated with T. gondii infection in the univariate and multivariate analysis (Tables 3a and 4). In addition, consumption of unwashed vegetables or fruits was observed to be significantly associated with toxoplasma seropositivity in the univariate analysis, although it was only marginally significant in the multivariable analysis Table 4. Similar results have been observed in studies done in Mexico [31], Ethiopia [10], and Sudan [32], whereas studies done in Douala-Cameroon [20], and Thailand [33], showed a significant association between T. gondii infection and consumption of untreated water only. Although domestic cats are probably the major source of contamination [1, 34], cat ownership and contact with cats were not found to be significantly associated with T. gondii infection [9, 13]. Indeed, only 6 % of the total study population reported having cats at home. Sporulated oocysts survive in moist soil for months to years [35]. Though no significance association was found between T. gondii infection and untreated water, it is likely that oocysts might have been present in some of the untreated water sources in our study area. Poor sanitation methods with the poor quality water used to wash raw meat at abattoirs or vegetables sold in the market, might have led to their contamination with oocysts.

Our study however should be interpreted with some caution. Our sample size was small and conclusions from the present study must be measured. It is likely that we may obtain different results with increased sample size. The number of equivocal results obtained using the selected ELISA technique in some cases was high, and difficult to interpret with the absence of reference testing facilities for toxoplasmosis in or around our study area. This could affect our results by increasing or decreasing the observed prevalences. Secondly, we observed an increase in risk of seropositivity with stage in pregnancy, but we did not follow up those women who were seropositive to study delivery outcomes or health status of their children. Thirdly, we may have obtained a different result if we considered sampling only women of child bearing age at the antenatal service. However, less than 30 % of our study population was sampled among those who came for medical check-up at the hospital, making our results more likely to reflect what we desired to investigate.

Toxoplasma gondii infection appears to be a public health concern in Njinikom, with a global antibody seroprevalence of 54.5 % among women of child bearing age attending antenatal or outpatient medical care in our study area. In this study, recent infections were found in 16.9 % of the study population while up to 10.7 % of patients were reactivating and there was no difference between pregnant and non-pregnant or HIV negative or HIV positive women. Consumption of raw or undercooked meat and of unwashed vegetables were observed to be risk factors for T. gondii infection among women of childbearing age in the locality of Njinikom, North West Region of Cameroon. Only 1.7 % (3/178) of the study participants knew about toxoplasmosis. Education on toxoplasmosis during antenatal care or in HIV treatment centres and screening for recent Toxoplasma exposure may be strategies for primary prevention of toxoplasmosis and its devastating outcomes in pregnancy or among HIV patients.