Introduction
Toxoplasmosis is a zoonotic disease caused by the protozoan parasite Toxoplasma gondii, an
obligate intracellular parasite. This parasite infects a wide range of animals, humans, other
mammals and various bird species.
Toxoplasmosis is of significant clinical importance in pregnant women and in
immunodeficient individuals. An active infection in pregnancy portends a risk of congenital
malformations and chronic carriage of infection with potential for reactivation of disease in
immunosuppression. In the immunedeficient, infection is potentially lethal, most commonly
manifesting as encephalitis, but may also present with chorioretinitis, pneumonitis and
myocardits amongst others. These can manifest as an acute infection or as reactivation of
latent infection acquired in the past.
T. gondii is transmissible via ingestion of food contaminated with oocysts, meat containing
tissue cysts, from pregnant mother to child transplacentally and via blood transfusion and
organ transplants.
The purpose of this study was to assess donated blood samples for the prevalence of
exposure to the infection as well as for the prevalence of recent infection which would cause
infection in susceptible hosts.
Objective
To determine the seroprevalence of acute and chronic Toxoplasma gondii infection in
donated blood at the National Blood Transfusions Service.
Methodology
This was a cross sectional observational study, with a sample size of three hundred and fifty
(350). Donated blood was obtained via random selection from the NBTS in conjunction with
the RBTC’s. All samples were tested for both IgG and IgM via ELISA using the Human
xi
Toxoplasma test kits. Blood samples found to be positive for IgM or that gave indeterminate
values were tested further for IgG avidity using Novatec Toxoplasma test kits.
The blood donors socio-demographic data was obtained from the standard questionnaire filled
in prior to blood donation. The data was entered into a computer data base from which
spreadsheets were generated and transferred to a standard software system for analysis.
Results
None of the blood samples examined via IgM ELISA was found to have acute T.gondii
infection. Latent infection was 42.3% via IgG ELISA. The highest prevalence rates of latent
infection were seen in donor samples from Eldoret (52.9%) and Nakuru (50%) and the lowest
prevalence was in Nairobi (22.9%). There were more blood samples from male donors (81%).
Forty one percent (41%) of blood samples from male donors tested positive for latent T.
gondii infection compared to 29.9% of samples from female donors. Majority of blood donors
were between 20 and 29 years of age. There was an increase in prevalence of latent T.gondii
infection with increasing age of blood donors, with a mean age for positivity to IgG markers
for T.gondii at 29 years and a mean age of negative result of IgG markers at 26.7 years. This
was statistically significant (p value of 0.005). The prevalence of latent infection was higher
in the unemployed (57.7%) and self employed (37.7%) as compared to the employed
(34.3%).This was statistically significant (p value of 0.001).
Conclusion
A large number of the donated blood samples, 42.3%, had markers of previous exposure to
T.gondii infection. These figures are higher than previous studies done in the country and are
much more reflective of the general population for the fact that blood was from healthy blood
donors and that the blood was from different regions of the country. There was a noted rise in
latent infection with increase in age similar to other studies elsewhere and earlier in this
country.