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Alzheimer's disease and related dementias (ADRD) present a significant global disease burden that is only expected to grow in the future. As such, there is a need to develop and investigate biomarkers that identify individuals at risk of developing ADRD with the goal of providing early interventions and treatments. Non-human primate (NHP) models of neurodegeneration present opportunities to examine such biomarkers in a preclinical model with the ability to control several confounding factors present in research with humans. Baboons naturally develop several ADRD-related neuropathologies that humans also exhibit, including age-related tau and amyloid deposition. However, to our knowledge, there are no data characterizing fluid biomarkers relevant to neurodegeneration or ADRD in baboons. We collected plasma (N = 139) and cerebrospinal fluid (CSF, N = 44) from captive baboons ranging in age from 3-19 years old. We characterized biomarkers as a function of age, sex, and rearing status in baboons using a bead-based bioplex human assay (Thermo Fisher Scientific's Neuroscience 18-Plex Human ProcartaPlex™ Panel). Fluid biomarkers were more detectable in CSF compared to plasma. Additionally, while sex and rearing did not significantly predict biomarkers in baboons, age significantly predicted levels of eight of the 12 biomarkers detected in the assay. Linear regressions showed that CSF levels of total tau, pTau181, NGF-beta, GFAP, NF-H, and S100B were higher in older baboons, as were plasma levels of NGF-beta. Lastly, older baboons showed a higher incidence of co-occurrence of multiple biomarkers as measured in CSF, but not in plasma. These data show that baboons exhibit age-dependent changes in biomarkers used in humans for clinical screening, diagnosis, and prognosis of ADRD, thereby further demonstrating the value of baboons as a model of aging and, possibly, ADRD., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2025 Neal et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Haematological and serum biochemical values are useful guides and biomarkers in health and diseases for reaching a diagnosis, estimating disease prognosis and monitoring treatment progress, in mammals. Reference ranges for some parameters differ among species of mammals and between sexes within a species. There is dearth of information on standard reference value for blood parameters for Nigerian indigenous monkeys. Whole blood and serum samples obtained from 50 apparently healthy adult monkeys in both captivity and from the wild in southwest Nigeria were subjected to haematology and serum biochemistry to obtain preliminary reference values for haematological and serum biochemical analytes for Cercocebus sebaeus (Green monkey), Cercopithecus mona (Mona monkey), Erythrocebus patas (Patas monkey) and Papio anubis (Anubis baboon). Numerical data were summarized as mean and standard deviation and subjected to statistical analysis; Student t test and analysis of variance, to compare values of blood parameters obtained between species and gender. A p-value less than 0.05 was considered significant. The hematocrit of male animals were significantly higher than that of females (P=0.01) in all the 4 species studied but there was no significant difference in other blood parameters such as total white blood cell and the differential counts, platelet count, serum aspartate transferase, alanine transferase, alkaline phosphatase, total plasma protein, albumin, and globulin concentrations between the sexes. Generally, there was no significant difference between total white blood cell and the differential counts, hematocrit, red cell count, haemoglobin concentration, platelet count, serum aspartate transferase, alanine transferase, alkaline phosphatase, total plasma protein, albumin, and globulin concentrations among the monkey species.

Chikungunya virus (CHIKV) is a globally emerging pathogen causing debilitating arthralgia and fever in humans. First identified in Tanzania (1953), this mosquito-borne alphavirus received little further attention until a 2004 re-emergence in Kenya from an unknown source. This outbreak subsequently spread to the Indian Ocean, with adaptation for transmission by a new urban vector. Under the hypothesis that sylvatic progenitor cycles of CHIKV exist in Kenya (as reported in West Africa, between non-human primates (NHPs) and arboreal Aedes spp. mosquitoes), we pursued evidence of enzootic transmission and human spillover events. We initially screened 252 archived NHP sera from Kenya using plaque reduction neutralization tests. Given an overall CHIKV seroprevalence of 13.1% (marginally higher in western Kenya), we sought more recent NHP samples during 2014 from sites in Kakamega County, sampling wild blue monkeys, olive baboons, and red-tailed monkeys ( N = 33). We also sampled 34 yellow baboons near Kwale, coastal Kenya. Overall, CHIKV seropositivity in 2014 was 13.4% (9/67). Antibodies reactive against closely related o'nyong-nyong virus (ONNV) occurred; however, neutralization titers were too low to conclude ONNV exposure. Seroprevalence for the flavivirus dengue was also detected (28%), mostly near Kwale, suggesting possible spillback from humans to baboons. CHIKV antibodies in some juvenile and subadult NHPs suggested recent circulation. We conclude that CHIKV is circulating in western Kenya, despite the 2004 human outbreaks only being reported coastally. Further work to understand the enzootic ecology of CHIKV in east Africa is needed to identify sites of human spillover contact where urban transmission may be initiated.