No Serologic Evidence of Middle East Respiratory Syndrome Coronavirus Infection Among Camel Farmers Exposed to Highly Seropositive Camel Herds: A Household Linked Study, Kenya, 2013

Abstract

High seroprevalence of Middle East respiratory syndrome coronavirus (MERS-CoV) among camels has been reported in Kenya and other countries in Africa. To date, the only report of MERS-CoV seropositivity among humans in Kenya is of two livestock keepers with no known contact with camels. We assessed whether persons exposed to seropositive camels at household level had serological evidence of infection. In 2013, 760 human and 879 camel sera were collected from 275 and 85 households respectively in Marsabit County. Data on human and animal demographics and type of contact with camels were collected. Human and camel sera were tested for anti-MERS-CoV IgG using a commercial enzyme-linked immunosorbent assay (ELISA) test. Human samples were confirmed by plaque reduction neutralization test (PRNT). Logistic regression was used to identify factors associated with seropositivity. The median age of persons sampled was 30 years (range: 5-90) and 50% were males. A quarter (197/760) of the participants reported having had contact with camels defined as milking, feeding, watering, slaughtering, or herding. Of the human sera, 18 (2.4%) were positive on ELISA but negative by PRNT. Of the camel sera, 791 (90%) were positive on ELISA. On univariate analysis, higher prevalence was observed in female and older camels over 4 years of age ( < 0.05). On multivariate analysis, only age remained significantly associated with increased odds of seropositivity. Despite high seroprevalence among camels, there was no serological confirmation of MERS-CoV infection among camel pastoralists in Marsabit County. The high seropositivity suggests that MERS-CoV or other closely related virus continues to circulate in camels and highlights ongoing potential for animal-to-human transmission.

A systematic review of MERS-CoV seroprevalence and RNA prevalence in dromedary camels: Implications for animal vaccination

“…Higher in camels > 4yrs p < 0.05 (Munyua et al, 2017) Kenya < 4yrs 36%(n = 319) > 4yrs 80% (n = 830) > 4 < 7yrs 59% (n = 70) > 7yrs 82% (n = 760)…”

“…In a study conducted across Burkina Faso, Morocco and Ethiopia, dromedaries used for milk and meat had higher seroprevalence than those used for transport (Miguel et al, 2017). In most of the studies that stratified by sex, little difference was seen, but in Kenya females had statistically significantly higher seroprevalence than males (93% vs. 81% in one study (Munyua et al, 2017), and 74% vs. 54% in another (Ommeh et al 2018)) whereas males had significantly higher seroprevalence in Egypt and in KSA (72% and 84% in males vs. 66% in females) (Ali et al, 2017b;Kasem et al, 2018b).…”

“…Two other studies in Kenya showed higher seroprevalence in nomadic herds compared with those kept on ranches or those with agro-pastoralist management. However, ranches were in a different region from nomadic herds and the sample size for agro-pastoralist management was very small Munyua et al, 2017).…”

Knowledge and practices regarding Middle East Respiratory Syndrome Coronavirus among camel handlers in a Slaughterhouse, Kenya, 2015

“…While neither the infection status in persons working with camels nor the risk of transmission was evaluated, studies have indicated that slaughterhouse workers are at an elevated risk of exposure relative to the general population (Muller et al, ). A study conducted in Marsabit County, Kenya, showed that despite 90% sero‐prevalence among camels, there was no serological evidence of MERS‐CoV exposure among pastoralists, suggesting localized MERS virus transmission patterns (Munyua et al, ). Further evaluation of exposure status among persons working with camels would inform development of surveillance and prevention guidelines.…”

“…In a study carried out in a single county in Kenya, 47% of camels were found to have antibodies (Deem et al, ). Another study carried out in Marsabit County showed over 90% sero‐prevalence among camels, but none of the humans tested showed presence of antibodies (Munyua et al, ). The true incidence of MERS‐CoV infections in humans may not actually be known, as most patients could be asymptomatic or present with symptoms similar to influenza, the common cold or other infections known to cause respiratory disease.…”