MERS-CoV Found in Hyalomma dromedarii Ticks Attached to Dromedary Camels at a Livestock Market, United Arab Emirates, 2019

The main mode of transmission of Middle East respiratory syndrome-related coronavirus (MERS-CoV) between dromedaries is likely via the respiratory route. However, there must be other modes to explain how the infection is brought to MERS-CoV-negative closed herds, such as transmission by ticks. Here, we present a study performed at three different locations in the United Arab Emirates (UAE) involving 215 dromedary camels (Camelus dromedarius) and the ticks attached to them. We tested the camels and ticks via RT-(q)PCR for the presence of MERS-CoV nucleic acids, as well as flaviviruses that may be present in the region (e.g., Alkhumra hemorrhagic fever virus). Camel sera were additionally analyzed for evidence of previous exposure to MERS-CoV. In total, 8 out of 242 tick pools were positive for MERS-CoV RNA (3.3%; C_t 34.6-38.3), 7 of which contained Hyalomma dromedarii ticks, and one contained a Hyalomma sp. tick (species not identified). All of the virus-positive ticks' host camels were also positive for MERS-CoV RNA in their nasal swab samples. Short sequences established in the N gene region from two positive tick pools were identical to viral sequences from their hosts' nasal swabs. In total, 59.3% of dromedaries at the livestock market had MERS-CoV RNA in their nasal swabs (C_t 17.7-39.5). While dromedaries at all locations were negative for MERS-CoV RNA in their serum samples, antibodies were detected in 95.2% and 98.7% of them (tested by ELISA and indirect immunofluorescence test, respectively). Given the probably transient and/or low level of MERS-CoV viremia in dromedaries and the rather high C_t values observed in the ticks, it seems unlikely that Hyalomma dromedarii is a competent vector for MERS-CoV; however, its role in mechanical or fomite transmission between camels should be investigated.

MERS-CoV in sheep, goats, and cattle, United Arab Emirates, 2019: Virological and serological investigations reveal an accidental spillover from dromedaries

The recent COVID-19 pandemic has demonstrated again the global threat posed by emerging zoonotic coronaviruses. During the past two decades alone, humans have experienced the emergence of several coronaviruses, such as SARS-CoV in 2003, MERS-CoV in 2012, and SARS-CoV-2 in 2019. To date, MERS-CoV has been detected in 27 countries, with a case fatality ratio of approximately 34.5%. Similar to other coronaviruses, MERS-CoV presumably originated from bats; however, the main reservoir and primary source of human infections are dromedary camels. Other species within the Camelidae family, such as Bactrian camels, alpacas, and llamas, seem to be susceptible to the infection as well, although to a lesser extent. In contrast, susceptibility studies on sheep, goats, cattle, pigs, chickens, and horses obtained divergent results. In the present study, we tested nasal swabs and/or sera from 55 sheep, 45 goats, and 52 cattle, collected at the largest livestock market in the United Arab Emirates, where dromedaries are also traded, for the presence of MERS-CoV nucleic acid by RT-qPCR, and for specific antibodies by immunofluorescence assay. All sera were negative for MERS-CoV-reactive antibodies, but the nasal swab of one sheep (1.8%) repeatedly tested positive for MERS-CoV nucleic acid. Next generation sequencing (NGS) of the complete N gene of the sheep-derived MERS-CoV revealed >99% nucleotide identity to MERS-CoV sequences of five dromedaries in nearby pens and to three reference sequences. The NGS sequence of the sheep-derived MERS-CoV was confirmed by conventional RT-PCR of a part of the N gene and subsequent Sanger sequencing. All MERS-CoV sequences clustered within clade B, lineage 5. In conclusion, our study shows that noncamelid livestock, such as sheep, goats, and cattle do not play a major role in MERS-CoV epidemiology. The one sheep that tested positive most likely reflects an accidental viral spillover event from infected dromedaries in nearby pens.

Crimean-Congo Hemorrhagic Fever Virus Past Infections Are Associated with Two Innate Immune Response Candidate Genes in Dromedaries

Dromedaries are an important livestock, used as beasts of burden and for meat and milk production. However, they can act as an intermediate source or vector for transmitting zoonotic viruses to humans, such as the Middle East respiratory syndrome coronavirus (MERS-CoV) or Crimean-Congo hemorrhagic fever virus (CCHFV). After several outbreaks of CCHFV in the Arabian Peninsula, recent studies have demonstrated that CCHFV is endemic in dromedaries and camel ticks in the United Arab Emirates (UAE). There is no apparent disease in dromedaries after the bite of infected ticks; in contrast, fever, myalgia, lymphadenopathy, and petechial hemorrhaging are common symptoms in humans, with a case fatality ratio of up to 40%. We used the in-solution hybridization capture of 100 annotated immune genes to genotype 121 dromedaries from the UAE tested for seropositivity to CCHFV. Through univariate linear regression analysis, we identified two candidate genes belonging to the innate immune system: FCAR and CLEC2B. These genes have important functions in the host defense against viral infections and in stimulating natural killer cells, respectively. This study opens doors for future research into immune defense mechanisms in an enzootic host against an important zoonotic disease.

Association of Dromedary Camels and Camel Ticks with Reassortant Crimean-Congo Hemorrhagic Fever Virus, United Arab Emirates

We previously detected a potentially novel reassortant of Crimean-Congo hemorrhagic fever virus in camels at the largest livestock market in the United Arab Emirates. A broader survey of large mammals at the site indicated zoonotic transmission is associated with dromedaries and camel ticks. Seroprevalence in cattle, sheep, and goats is minimal.

Crimean-Congo Hemorrhagic Fever Virus Endemicity in United Arab Emirates, 2019

We conducted a cross-sectional survey of Crimean-Congo hemorrhagic fever virus (CCHFV) in dromedary camels and attached ticks at 3 locations in the United Arab Emirates. Results revealed a high prevalence of CCHFV-reactive antibodies in camels and viral RNA in ticks and camel serum, suggesting the virus is endemic in this country.