Toxoplasmosis refers to the disease caused by T. gondii. In the present study Toxoplasma specific IgG and IgM antibody levels were analyzed using ELISA, one of the standard procedures for detection of antibodies. Detection of both IgG and IgM simultaneously helps establishing exposure to T. gondii and the chronological status of such exposure. In the present study the prevalence rate of anti-T. gondii IgG antibodies in HIV positive pre-ART individuals was significantly higher than in HIV negative blood donors (87.4% versus 70.29%, P=0.003). Similar finding of significantly higher Toxoplasma seropositivity in HIV infected individuals than in HIV-uninfected people was also demonstrated in Addis Ababa. The finding of significant difference between HIV infected and non-infected individuals also agrees with studies done in Bamako, 60% versus 21% and in Nigeria 54% versus 37.5%. These differences might be attributed to the reactivation of latent infection/tissue toxoplasmosis when the host immunity is compromised (reduced cellular immunity) in HIV patients. In addition, variability in results can be due to differences in age among the study groups and differing lifestyles and geographical conditions. In our case, HIV infected patients were older compared to the HIV negative counterparts (median age 23 versus 34 years, p=0.000).
The overall finding of a high seroprevalence of IgG in HIV positive pre-ART individuals was comparable with the study done in Akaki town, suburban of Addis Ababa, in which sera were screened for anti-Toxoplasma IgG antibodies using the Sabin-Feldman test and 80% seroprevalence was reported. Our finding is also consistent with a Venezuelan study which demonstrated 85% prevalence of anti-T. gondii IgG antibody in the HIV-positive adult population. However, our result was much higher than other studies as in Johannesburg 8%. It also differs from a study done in Iran among HIV/AIDs patients which reported prevalence of 58%. The observed differences in prevalence of anti-T. gondii antibodies could be due to differences in geographical distribution and/ or possible risk factors and socioeconomic conditions contributing to acquiring the infection.
In the present study, anti-T. gondii IgM seropositivity rate was 10.7% in HIV infected pre-ART individuals. A similar study in India reported 6% anti-Toxoplasma IgM positivity using double sandwich ELISA. The consumption of undercooked or raw meat and contact with cat were found to be risk factors for the presence of anti-T. gondii IgG in HIV infected pre-ART individuals. Similar results were demonstrated by studies done in Nazaret town, Ethiopia and at Lagos University teaching hospital, Nigeria. On the other hand, no significant association was identified between the history of blood transfusion and anti-T. gondii seropositivity. It is worth mentioning that the number of participants with a history of blood transfusion was only three and all of them were HIV positive. Nonetheless, a similar study in Malaysia has documented the absence of a significant association between a history of blood transfusion and T. gondii seropositivity. Beef, lamb and chicken are eaten in the study area. In the nation raw meat dishes such as "Kitfo" and "kourt" are most favored by the society and eaten raw or lightly cooked. However, HIV positive individuals are advised to eat cooked meat to minimize persistent immune activation as a result of tapeworms and or other secondary infections through meat as immune activation is one of the mechanism of CD4 depletion. HIV negative individuals consume raw and undercooked favorite meat dishes such as "Kitfo" and "kourt" of the Ethiopians. Pork is not consumed at all in the study area.
According to the present findings, no statistically significant difference was observed among different age groups and inhabitants of rural and urban areas of HIV infected and non-infected study participants, and the associated sero-reactivity of anti-T. gondii antibodies. The exception to this is the age group 21–30 in the HIV negatives where individuals are 5.58 times more likely to be seropositive for anti-T. gondii antibodies. This is in agreement with previous studies on the prevalence of anti-T. gondii IgG antibodies from blood donors in Yucatan and seroprevalence of anti-T. gondii antibodies in a healthy population from Slovakia. The prevalence of anti-T. gondii IgG and IgM antibodies in HIV negative blood donors were 70.29% and 2.97%, respectively. Seroprevalence of IgM that we found was comparable to the 2.4% and 1.9% reported from Czech Republic and Mexico blood donors, respectively[34, 35]. The present finding of anti-T. gondii IgG antibodies in blood donors is consistent with the 75% prevalence reported from Brazil and 69% from the Southern Mexican State of Yucatan. Consumption of undercooked or raw meat was found to be a risk factor for the presence of anti-T. gondii IgG in HIV negative individuals. Undercooked meat consumption has been found to be an important factor in parasite transmission in several studies[18, 35]. A similar finding was also demonstrated as risk factor for toxoplasmosis in studies done in Slovakia. Moreover, prevalence of anti-T. gondii IgG from male healthy blood donors was significantly higher than female HIV negative blood donors (p=0.001).
In the present study no significant association was found between the seroprevalence of toxoplasmosis and different educational status. Similar findings were recorded between anti Toxoplasma IgG antibodies and education level and the infection among pregnant women in Turkey.
Generally, IgM antibodies are detectable early after infection and can persist for prolonged times after infection. Therefore, the presence of IgM does not necessarily indicate an acute infection and its presence in subjects with anti T. gondii IgG antibodies could indicate a chronic infection. Hence, though we cannot confirm in this study, the finding of sero-positive anti-T. gondii IgM/IgG antibodies suggests the potential risk of parasite transmission by blood transfusion practices.
Findings on the association of HIV and toxoplasmosis seroprevalence are varied in different parts of the world. Previous studies involving HIV-infected individuals have reported wide variations in T. gondii seroprevalence (3%–22%)[38, 39]. Some authors found higher prevalence of T. gondii specific IgG in HIV-infected patients compared to non-infected individuals[40, 41], whereas others did not find any differences between the two groups. Serologic data provided little information, in extracerebral toxoplasmosis in patients infected with HIV. Previous studies in Ethiopia revealed a higher Toxoplasma seroprevalence in both HIV infected and non-infected individuals that is not statistically significantly different between the two groups. On the other hand, studies from Mozambique found similar higher toxoplasmosis occurrence in the HIV-positive groups as compared to HIV-negative groups that according to the authors could be ascribed to common or associated risk factors for both infections, such as exposure to both sexual contacts and meat consumption. Several explanations for the interaction between both infections resulting in high Toxoplasma infection in HIV patients have been previously proposed. One possibility is an increase in risky behavior in Toxoplasma infected individuals that leads to increased exposure to HIV infection. Such a change in behavior could be due to parasite-driven personality changes, as described in Toxoplasma-infected individuals by others. Another plausible explanation is that Toxoplasma infection is a marker of exposure to risky social contacts or habits, which correlates with early HIV infection.
Regarding the higher prevalence in males than females, Shimelis et al., observed a statistically significantly higher prevalence rate of Toxoplasma infection in males than females in the bivariate analysis, which disappeared in the multivariate analysis. In our case the difference is maintained in the multivariate model and may be attributed to differences in socialization behavior or environmental exposure of males compared to females.