Risk Factors for Middle East Respiratory Syndrome Coronavirus Infection among Camel Populations, Southern Jordan, 2014-2018

MERS-CoV exposure and risk factors for MERS-CoV ELISA seropositivity among members of livestock-owning households in southern Jordan: a population based cross-sectional study

BACKGROUND

Although dromedary camels (Camelus dromedarius) are known to be the host reservoir for MERS-CoV, the virus causing Middle East respiratory syndrome (MERS), zoonotic transmission pathways and camel subpopulations posing highest transmission risk are poorly understood. Extensively managed herds, ubiquitous across the Arabian Peninsula, present a major potential source of primary infection. In this study we aimed to address key knowledge gaps regarding MERS epidemiology among high-risk communities associated with such herds, which is essential information for effective control strategies.

METHODS

We did a cross-sectional study between Sept 27, 2017, and Oct 11, 2018, among members of livestock-owning households in southern Jordan (Aqaba East, Aqaba West, Ma'an East, and Ma'an West regions), with random selection of households (house and tent dwellings) from Ministry of Agriculture lists via computer-generated randomisation lists. Household visits were done, with questionnaires administered to household members regarding potential risk factors for MERS-CoV exposure in the past 6 months and blood samples and nasal and oral swabs collected, alongside physical examination data including blood pressure and blood glucose. Children younger than 5 years and individuals without capacity to provide informed consent were excluded. Serum was tested for IgG antibodies to MERS-CoV spike protein (S1 subunit) and nucleocapsid (N) protein with in-house indirect ELISAs, and viral RNA was detected in nasal and oral samples by RT-PCR. The primary outcome was evidence of MERS-CoV exposure (ascertained by seropositive status on S1 or N ELISAs, or a positive swab sample on RT-PCR); secondary outcomes were potential associations between possible risk factors and seropositive status. RT-PCR data were to be presented descriptively. Seroprevalence estimates were obtained at the individual and household levels, and associations between hypothetical risk factors and seropositive status were assessed with use of mixed-effects logistic regression.

FINDINGS

We sampled 879 household members (median age 27 years [IQR 16-44]; 471 [54%] males and 408 [46%] females) from 204 households. 72 (8%) household members were seropositive on S1 ELISA (n=25, 3%) or N ELISA (n=52, 6%). No positive nasal or oral swab samples were identified on RT-PCR. Within-household clustering was identified for seropositivity on S1 ELISA (intraclass correlation coefficient 0·88 [0·35-0·96]) but not N ELISA (0·00 [0·00-0·27]). On multivariable analysis, S1 ELISA seropositivity was associated with frequently (≥weekly) interacting with young (age <1 year) camels (adjusted odds ratio [ORadj] 3·85 [95% CI 1·41-11·61], p=0·011), with frequent kissing and petting (ORadj 4·56 [1·55-15·42], p=0·0074), and frequent feeding and watering (ORadj 4·97 [1·80-15·29], p=0·0027) of young camels identified as risk activities. Attending camel races (ORadj 3·73 [1·11-12·47], p=0·029), frequently feeding and watering camels of any age (ORadj 3·18 [1·12-10·84], p=0·040), and elevated blood glucose (>150 mg/dL; ORadj 4·59 [1·23-18·36], p=0·021) were also associated with S1 ELISA seropositivity. Among individuals without history of camel contact, S1 ELISA seropositivity was associated with sharing a household with an S1 ELISA-positive household member (ORadj 8·92 [1·06-92·99], p=0·044), and with sharing a household with an S1 ELISA-positive household member with history of camel contact (ORadj 24·74 [2·72-306·14], p=0·0050). N ELISA seropositivity was associated with age (categorical, p=0·0069), a household owning a young camel (age <18 months; ORadj 1·98 [1·02-4·09], p=0·043), and frequently feeding and watering camels of any age (ORadj 1·98 [1·09-3·69]; p=0·025).

INTERPRETATION

The study findings highlight the importance of effective MERS-CoV surveillance and control strategies among camel-owning communities in Jordan and the Arabian Peninsula. Juvenile dromedaries pose increased risk for zoonotic MERS-CoV transmission and should be prioritised for vaccination once such vaccines become available. Among high-risk communities, vaccination strategies should prioritise camel-owning households, particularly individuals engaged in camel husbandry or racing, and household members who are older or diabetic, with evidence to suggest secondary within-household transmission.

FUNDING

UK Medical Research Council and US National Institute of Allergy and Infectious Diseases.

A longitudinal study of Middle East respiratory syndrome coronavirus (MERS-CoV) in dromedary camels

BACKGROUND

Middle East respiratory syndrome coronavirus (MERS-CoV) was identified in humans in 2012. Since then, 2605 cases and 937 associated deaths have been reported globally. Camels are the natural host for MERS-CoV and camel to human transmission has been documented. The relationship between MERS-CoV shedding and presence of neutralizing antibodies in camels is critical to inform surveillance and control, including future deployment of camel vaccines. However, it remains poorly understood. The longitudinal study conducted in a closed camel herd in Egypt between December 2019 and March 2020 helped to characterize the kinetics of MERS-CoV neutralizing antibodies and its relation with viral shedding.

RESULTS

During the 100-day longitudinal study, 27 out of 54 camels (50%) consistently tested negative for presence of antibodies against MERS-CoV, 19 (35.2%) tested positive and 8 (14.8%) had both, positive and negative test results. Fourteen events that could be interpreted as serological indication of probable infection (two seroconversions and twelve instances of positive camels more than doubling their optical density ratio (OD ratio) in consecutive samples) were identified. Observed times between the identified events provided strong evidence (p = 0.002) against the null hypothesis that they occurred with constant rate during the study, as opposed to clustering at certain points in time. A generalized additive model showed that optical density ratio (OD ratio) is positively associated with being an adult and varies across individual camels and days, peaking at around days 20 and 90 of the study. Despite serological indication of probable virus circulation and intense repeated sampling, none of the tested nasal swab samples were positive for MERS-CoV RNA, suggesting that, if the identified serological responses are the result of virus circulation, the virus may be present in nasal tissue of infected camels during a very narrow time window.

CONCLUSIONS

Longitudinal testing of a closed camel herd with past history of MERS-CoV infection is compatible with the virus continuing to circulate in the herd despite lack of contact with other camels. It is likely that episodes of MERS-CoV infection in camels can take place with minimal presence of the virus in their nasal tissues, which has important implications for future surveillance and control of MERS-CoV in camel herds and prevention of its zoonotic transmission.

Middle East respiratory syndrome coronavirus-a 10-year (2012-2022) global analysis of human and camel infections, genomic sequences, lineages, and geographical origins

OBJECTIVES

The World Health Organization priority zoonotic pathogen Middle East respiratory syndrome (MERS) coronavirus (CoV) has a high case fatality rate in humans and circulates in camels worldwide.

METHODS

We performed a global analysis of human and camel MERS-CoV infections, epidemiology, genomic sequences, clades, lineages, and geographical origins for the period January 1, 2012 to August 3, 2022. MERS-CoV Surface gene sequences (4061 bp) were extracted from GenBank, and a phylogenetic maximum likelihood tree was constructed.

RESULTS

As of August 2022, 2591 human MERS cases from 26 countries were reported to the World Health Organization (Saudi Arabia, 2184 cases, including 813 deaths [case fatality rate: 37.2%]) Although declining in numbers, MERS cases continue to be reported from the Middle East. A total of 728 MERS-CoV genomes were identified (the largest numbers were from Saudi Arabia [222: human = 146, camels = 76] and the United Arab Emirates [176: human = 21, camels = 155]). A total of 501 'S'-gene sequences were used for phylogenetic tree construction (camels [n = 264], humans [n = 226], bats [n = 8], other [n=3]). Three MERS-CoV clades were identified: clade B, which is the largest, followed by clade A and clade C. Of the 462 clade B lineages, lineage 5 was predominant (n = 177).

CONCLUSION

MERS-CoV remains a threat to global health security. MERS-CoV variants continue circulating in humans and camels. The recombination rates indicate co-infections with different MERS-CoV lineages. Proactive surveillance of MERS-CoV infections and variants of concern in camels and humans worldwide, and development of a MERS vaccine, are essential for epidemic preparedness.

A One Health strategy for emerging infectious diseases based on the COVID-19 outbreak

Coronavirus disease 2019 (COVID-19) is as an emerging infectious disease (EID) that has caused the worst public health catastrophe of the 21st century thus far. In terms of impact, the COVID-19 pandemic is second only to the Spanish Flu pandemic of 1918 in modern world history. As of 7 September 2021, there have been 220 million confirmed cases of COVID-19 and more than 4.5 million deaths. EIDs pose serious public health and socio-economic risks, and 70% of EIDs originate from wildlife. Preventing development of EIDs such as COVID-19 is a pressing concern. Here, taking the COVID-19 pandemic as an example, we illustrate the disastrous effects of EIDs and assess their emergence and evolution from a One Health perspective. We propose a One Health strategy, centered on ‘moving the gates forward’, for EID prevention and control at the human–animal–environment interface. This strategy may be instructive and provide early warnings of EIDs in the future.