Antibody kinetics and shedding dynamics of MERS-CoV in dromedary camels from different production systems in Kenya : a longitudinal cohort study

Abstract

Understanding long-term antibody kinetics in different camel production systems is crucial for risk assessment for Middle East respiratory syndrome coronavirus (MERS-CoV), a zoonotic pathogen first detected in humans in Saudi Arabia. Though the virus is endemic in dromedary camels across Africa, the Middle East, and parts of South Asia, zoonotic transmission outside of the Arabian Peninsula is undocumented. A retrospective analysis of longitudinal surveillance data of MERS-CoV was conducted on 2460 serum samples collected from 174 camels in three high-risk counties of Kenya from April 2018 to March 2021. Data were analyzed using descriptive statistics, logistic regression, and survival analysis. A total of 93/174 (53.4%) camels were seropositive at least once (animal-level), while 882/2460 (35.85%) of all serum samples tested seropositive (sample-level). Data were analyzed using descriptive statistics, logistic regression and survival analysis. A total of 93/174 (53.4%) camels were seropositive at least once. All camels in the pastoral system seroconverted, exhibiting significantly higher odds of seropositivity (OR: 9.4) compared to ranched camels, and camels above 3 years (OR: 21.2) are more likely to be seropositive compared to young ones. The median duration of seropositivity was 21 days (IQR: 11–53), varying significantly by geographical site. Camels from Garissa and Soysambu have 97% (aOR: 0.03 (CI95%: 0.001–0.79; p = 0.035) and 98% (aOR: 0.02 (CI95%: 0.001–0.48; p = 0.015) longer durations of seropositivity than those from Isiolo. The study demonstrates the spatiotemporal and biological variability of antibody levels, indicative of fluctuations in viral exposure and the resultant immune response among the camel herds. Thus, camel production practices, not just seroprevalence, drive MERS-CoV infection dynamics, demanding surveillance and stewardship strategies that are tailored to specific production systems to effectively mitigate zoonotic risk.