Date Published: October 16, 2018
Publisher: Public Library of Science
Author(s): Audrey I. Nisbet, Geoffrey Omuse, Gunturu Revathi, Rodney D. Adam, Eileen Stillwaggon.
Relevant seroprevalence data for endemic pathogens in a given region provide insight not only into a population’s susceptibility to acute infection or risk for reactivation disease but also into the potential need for policy initiatives aimed at reducing these risks. Data from sub-Saharan Africa are sparse and since Aga Khan University Hospital Nairobi is an internationally accredited hospital equipped with a laboratory electronic medical record system, analysis of pertinent local seroprevalence data has been made possible.
We have analyzed serology data from laboratory electronic records at a 300 bed tertiary private teaching hospital in Kenya for the dates, 2008 to 2017 for Toxoplasma gondii, cytomegalovirus, and rubella, which were used primarily for antenatal screening. We also analyzed the data from hepatitis A and amebiasis serologies, which were used primarily for diagnostic purposes.
For T. gondii, cytomegalovirus, and rubella, we used IgG serology to determine seroprevalence, finding rates of 32%, 86%, and 89%, respectively. There was no significant age-related difference in the 20 to 49 year old age range for any of these three pathogens. Of the Hepatitis A IgM tests that were ordered, 33% were positive with a peak positive rate of 70% in the five to nine year old age range. The seroprevalence of amebiasis was 4% and all cases of seropositivity were accompanied by compatible clinical illness (hepatic abscess).
These data provide insight into seroprevalence rates of selected pathogens that can be used to guide screening and diagnostic laboratory testing as well as private and public immunization practices.
Seroprevalence data can provide information useful for clinicians when it comes to timely initial empirical treatment, patient education, and evaluation of susceptibility to acute infection or risk for reactivation disease in vulnerable patient populations. These data can also be leveraged by public health officials and policy makers during the formulation of vaccination guidelines, patient screening practices, and health communication initiatives.
AKUHN is a 300 bed university hospital in Nairobi Kenya with a range of post-graduate medical education programs. The patients are primarily from the upper middle and high socioeconomic groups comprised mainly of black African Kenyans, Kenyans of Asian descent, and a small Caucasian population ‒ mostly expatriates. The moderate numbers of HIV-infected patients seen at the hospital reflect the national HIV prevalence of nearly 7%, which is midrange for sub-Saharan Africa. The hospital has about 50 critical beds, including intensive care unit, coronary care unit, cardiothoracic intensive care unit, neonatal intensive care unit, and high dependency units. There is a nine bed outpatient dialysis unit and a cancer center. The hospital conducts approximately 3600 deliveries in a year. The laboratory was the first hospital laboratory in East Africa to become internationally accredited by ISO 15189 standards through the South Africa national accreditation service (SANAS) . The Aga Khan hospitals in Mombasa and Kisumu have bed capacities of approximately 80. The laboratories at these hospitals are also accredited by SANAS and refer their more complex tests, including serologies to the Nairobi facility.
Seroprevalence can be estimated from serologic tests performed as part of routine prenatal care, which is the case for the majority of T. gondii, CMV, and rubella serologic tests. T. gondii seroprevalence differs widely among countries and areas within countries because of climate and multiple human factors. An earlier study on sera from blood donors in four areas of Kenya showed an overall antibody prevalence of 54%, ranging from 43% to 65% in the four areas . Their rate of 45% from Nairobi is higher than our rate of 27% and could reflect a change in seroprevalence over the last three decades or test methodologies. However, we also note that the patients seen at AKUHN are from middle and upper socioeconomic levels and are likely to have lower seroprevalence rates for these pathogens than those from lower socioeconomic groups. The three Aga Khan hospitals represented in this study care for similar patient populations, allowing for a geographical comparison among Kisumu on Lake Victoria, Mombasa on the Indian Ocean, and Nairobi in a central high elevation area. The 27% positive rate in Nairobi is significantly lower than the rates of 52% and 57% we found in Kisumu and Mombasa, respectively. Feral cats are common throughout Kenya and ingestion of undercooked meat is uncommon, suggesting that most human T. gondii infection results from inadvertent ingestion of oocysts passed by feral cats. This could be due to direct contact with contaminated soil or from the ingestion of fruits and vegetables contaminated with oocysts . In addition, infection from drinking water is also possible . Perhaps the reason for the lower seroprevalence in Nairobi is because of a lower humidity, making it less suitable for oocyst maturation after being passed in cat feces. Understanding of local seroprevalence rates for T. gondii is very useful for guiding the approach to HIV-infected patients with space-occupying lesions in the brain . These lesions are nearly always due to reactivation of latent infection; thus, a negative IgG antibody at the time of presentation nearly rules out toxoplasmosis as the diagnosis .
The information presented in this report can be used by clinicians and policy makers in the continued advancement of healthcare in Kenya. Similarities and differences between the data in this report and existing data for Kenya, other African countries, and regions outside of Africa that have been highlighted here provide sound points of comparison and a foundation upon which an examination of current practices in Kenya can be made. It is also worth noting that for these and other pathogens, age of acquisition increases and seroprevalence rates decrease with increasing income. Thus, it is possible that these seroprevalence rates would be higher if lower income patients were included. Continued evaluation of seroprevalence data and the factors that contribute to these data would be a valuable step in continuing to advance the health of Kenya.