Low seroprevalence of antibodies to Toxoplasma gondii in blood donors in central Namibia

Although emphasis has been placed on research relating to human immunodeficiency virus (HIV), tuberculosis and malaria, several researchers in Africa are focusing on other threats to human health, such as neglected tropical diseases. Toxoplasma gondii is a possible neglected tropical disease in Namibia, although the country has a diversity of climate, ranging from tropical in the north to semi-desert in the south. Except for one study in 1978, no recent studies have determined the burden of T. gondii infection in Namibia. Three hundred and twelve convenience samples were collected from volunteer blood donors in central Namibia. Donors provided informed consent to participate in the study, and 5 ml blood was collected. Demographic information was collected by means of a questionnaire. Serum was analysed using Captia^TM T. gondii immunoglobulin G (Ig) G enzymelinked immunosorbent assay (ELISA) kit. Only samples that tested positive or equivocal for IgG antibodies were then tested for IgM antibodies using Captia^TM T. gondii IgM ELISA kit. Of the 312 samples, 3 (0.961%) tested positive for IgG antibodies to T. gondii. One sample (0.3%) tested positive for IgM antibodies to T. gondii. These donors lived in urban areas in central Namibia and interacted regularly with animals, such as cats and dogs. The prevalence of antibodies to T. gondii in Namibian blood donors was found to be considerably lower than that reported in other African countries, but comparable to that in a recent report from South Africa. It is notable that most of the donors lived in the arid central regions of Namibia, where the high altitude could also affect parasite survival.Peer reviewedEntomology and Plant Patholog

Exposure and risk factors to Coxiella burnetii, spotted fever group and typhus group rickettsiae, and Bartonella henselae among volunteer blood donors in Namibia

Background: The role of pathogen-mediated febrile illness in sub-Saharan Africa is receiving more attention, especially in Southern Africa where four countries (including Namibia) are actively working to eliminate malaria. With a high concentration of livestock and high rates of companion animal ownership, the influence of zoonotic bacterial diseases as causes of febrile illness in Namibia remains unknown.Methodology/Principal Findings: The aim of the study was to evaluate exposure to Coxiella burnetii, spotted fever and typhus group rickettsiae, and Bartonella henselae using IFA and ELISA (IgG) in serum collected from 319 volunteer blood donors identified by the Blood Transfusion Service of Namibia (NAMBTS). Serum samples were linked to a basic questionnaire to identify possible risk factors. The majority of the participants (64.8%) had extensive exposure to rural areas or farms. Results indicated a C. burnetii prevalence of 26.1% (screening titre 1:16), and prevalence rates of 11.9% and 14.9% (screening titre 1:100) for spotted fever group and typhus group rickettsiae, respectively. There was a significant spatial association between C. burnetii exposure and place of residence in southern Namibia (P0.012), especially cattle (P>0.006), were also significantly associated with C. burnetii exposure. Males were significantly more likely than females to have been exposed to spotted fever (P<0.013) and typhus (P<0.011) group rickettsiae. Three (2.9%) samples were positive for B. henselae possibly indicating low levels of exposure to a pathogen never reported in Namibia.Conclusions/Significance: These results indicate that Namibians are exposed to pathogenic fever-causing bacteria, most of which have flea or tick vectors/reservoirs. The epidemiology of febrile illnesses in Namibia needs further evaluation in order to develop comprehensive local diagnostic and treatment algorithms.Peer reviewedEntomology and Plant Patholog

Risk assessment of flavivirus transmission in Namibia

The role of arboviruses causing acute febrile illness in sub-Saharan Africa is receiving more attention. Reports of dengue in tourists were published nearly 10 years ago in Namibia, but the current epidemiology of arboviruses is unknown and surveys of mosquito vectors have not been carried out since the 1950s. To begin addressing this knowledge gap, a prospective cross-sectional study was conducted using samples from volunteer blood donors linked to questionnaire. Serum samples were tested using a Dengue IgG Indirect ELISA which measured exposure to dengue virus/flaviviruses. Entomological samples were collected from tires during the rainy season (February-March 2012) in six locations across Namibia's capital city, Windhoek. Among 312 blood donors tested, 25 (8.0%) were positive for dengue virus/flavivirus exposure. The only significant risk factor was age group with high exposure rates among those older than 50 (29%) compared with those below 40 years old (between 2.9% and 8.3%) (P< 0.002). Larvae and pupae of Aedes aegypti and Culex pipiens complex accounted for 100% of the 2751 samples collected, of which only 12.2% (n=. 336) were Ae. aegypti. Each site demonstrated high variability of species composition between sampling times. While the significant dengue virus/flavivirus exposure rate among those above 50 years old is likely indicative of the West Nile epidemic in the 70s and 80s, the low exposure among those under 50 suggests that flaviviruses are still circulating in Namibia. While Ae. aegypti and C. pipiens sp. may play a role in future epidemics, the significance of presence may be reduced due to short rain periods, dry, arid, cold winters and policies and social understandings that limit non-structured storage and use of tires in low income areas. Future studies should further characterize the circulating arboviruses and investigate mosquito ecology nationally to map areas at higher risk for future arbovirus outbreaks.Peer reviewedEntomology and Plant Patholog