Sunday, June 17, 2018

EID Journal: Geographic Distribution of MERS-CoV among Dromedary Camels, Africa


Six years ago this week, Dr. Ali Mohamed Zaki - an Egyptian virologist working in Saudi Arabia - collected blood and sputum samples from a 60 year old Saudi male hospitalized with with pneumonia and acute renal failure and began testing to determine the pathogen involved (see Nature Middle East The story of the first MERS patient).
Although he was able to isolate and culture a virus, his laboratory lacked the facilities to sequence its genome. He decided to send a sample to Dr. Ron Fouchier, at the Erasmus Medical Centre in the Netherlands, who had the equipment to do a proper analysis.
Two months later, Dr. Zaki emailed ProMed Mail (see Sometimes They Come Back), announcing the discovery of a new `SARS-like' coronavirus. Dr. Zaki's eventual `reward’ was that he was fired by the Saudis for going public with his discovery, proving once again that no good deed goes unpunished.  

Roughly one year - and 91 confirmed cases MERS Cases later - dromedary camels were pegged as the likely zoonotic conduit of the virus to humans (see Lancet: Camels Found With Antibodies To MERS-CoV-Like Virus).
At first the Saudis were slow to accept the idea that camels - a beloved symbol of their country - could carry a deadly disease (see Saudi Health Minister denies relation between camels, Mers).
In the face of mounting evidence, however, (see EID Journal: MERS Coronaviruses in Dromedary Camels, Egypt & The Lancet: Identification Of MERS Virus In Camels), in May of 2014 the Saudi Ministry Of Agriculture Issued Warnings On Camels, urging breeders and owners to limit their contact with camels, and to use PPEs (masks, gloves, protective clothing) when in close contact with their animals. 

Once camels in KSA were implicated, researchers began testing camels in other regions of the Middle East and Africa. Looking for, and finding, evidence of carriage of the MERS coronavirus going back many years.
EID Journal: MERS Antibodies In Camels – Kenya 1992-2013
Kuwait Tests Camels - Finds 6% Positive For MERS-CoV

EID Journal: Three Decades Of MERS-CoV Antibodies In Camels
Last year, in MERS-CoV In Camels: The Gift That Keeps On Giving, we saw a study that demonstrated that camels can be reinfected by the MERS virus, despite having substantial antibody titers.  A finding that may significantly complicate vaccine creation.
One of the (many) mysteries surrounding MERS-CoV is that while camel infection appears common on the Arabian peninsula, Saudi Arabia accounts for roughly 90% of known human MERS infections in that part of the world.
Even further afield, in early 2017 we saw EID Journal: Serologic Evidence Of MERS-CoV Infection in Pakistani Camels, and in 2015 Eurosurveillance: MERS-CoV In Nigerian Camels, yet South Asia and Africa have never reported a human infection.
Today we can add another study, published in the EID Journal, that further expands the geographic range of MERS-CoV in African camels, and shows its prevalence to be very high.   
I've only posted some excerpts, so you'll want to follow the link to read it in its entirety.  I'll have a bit more when you return. 

Volume 20, Number 8—August 2014
Geographic Distribution of MERS Coronavirus among Dromedary Camels, Africa

Chantal B.E.M. Reusken1 , Lilia Messadi1, Ashenafi Feyisa1, Hussaini Ularamu1, Gert-Jan Godeke, Agom Danmarwa, Fufa Dawo, Mohamed Jemli, Simenew Melaku, David Shamaki, Yusuf Woma, Yiltawe Wungak, Endrias Zewdu Gebremedhin, Ilse Zutt, Berend-Jan Bosch, Bart L. Haagmans, and Marion P.G. Koopmans


We found serologic evidence for the circulation of Middle East respiratory syndrome coronavirus among dromedary camels in Nigeria, Tunisia, and Ethiopia. Circulation of the virus among dromedaries across broad areas of Africa may indicate that this disease is currently underdiagnosed in humans outside the Arabian Peninsula.

A novel betacoronavirus, Middle East respiratory syndrome coronavirus (MERS-CoV), was identified as the cause of severe respiratory disease in humans during 2012 (1). In August 2013, dromedary camels (Camelus dromedarius) were implicated for the first time as a possible source for human infection on the basis of the presence of MERS-CoV neutralizing antibodies in dromedaries from Oman and the Canary Islands of Spain (2).

Since then, the presence of MERS-CoV antibodies in dromedaries has been reported in Jordan (3), Egypt (4,5), the United Arab Emirates (6,7), and Saudi Arabia (8,9). In October 2013, analysis of an outbreak associated with 1 barn in Qatar (10) found dromedaries and humans to be infected with nearly identical strains of MERS-CoV.

Further proof of widespread circulation of MERS-CoV among dromedaries was provided by studies from Egypt and Saudi Arabia (5,9). These findings have raised questions about the geographic distribution of MERS-CoV among camel populations elsewhere. Here, we report our assessment of the geographic distribution of MERS-CoV circulation among dromedaries in Africa by serologic investigation of convenience samples from these animals in Nigeria, Tunisia, and Ethiopia.
A question raised by these findings is whether human cases occur outside the Arabian Peninsula and if such cases are currently underdiagnosed in Africa. In addition, for the whole region, the possibility exists that MERS-CoV illness occurred before its discovery in 2012 and that such infection has been overlooked in the areas with evidence for virus circulation among animals during the past 10 years. Retrospective studies of cohorts of humans with respiratory illnesses of unknown etiology should address this notion.
Alternative explanations for the lack of cases in Africa could be the following: a different risk profile, for instance, related to demographics and local practices; or subtle genetic differences in the circulating virus strain.
Full-genome sequencing, virus isolation, and phenotypic characterization of viruses circulating outside the Arabian Peninsula will resolve this issue. Meanwhile, awareness of MERS-CoV infections should be raised among clinicians in Africa.
(Continue . . . )

While it may seem unlikely than any significant number of clinical MERS cases could go undetected in Africa, it isn't as far-fetched of an idea as it may sound.

Despite years of reporting outbreaks of H5N1 in Sub-Saharan African poultry, only one human infection with the virus has ever been confirmed there by the WHO (see 2007’s Nigeria Confirms Human Bird Flu Case).
There were three other suspected cases at the time  - including the mother of the confirmed case in Lagos – but testing was `inconclusive’.
According to local media reports at the time (see The Nigerian Paradox), the only reason we have the one confirmed case is because the husband/father of the two related victims paid for a private autopsy and lab testing when his daughter died two weeks after his wife. 

The reality is, in Nigeria (pop. 175 million) - the average life expectancy is about 53 years - and roughly 6,000 people die each and every day.  Many are never  afforded medical care, and testing for exotic diseases like H5N1 or MERS-CoV is rarely - if ever - done.
According to the CDC, the top 10 causes of death in Nigeria are:
Deaths from lower respiratory infections in Nigeria, which can cover a lot of territory – including novel influenza or MERS-CoV – are second only to malaria.
The story is much the same in many other African nations where MERS has been detected in camels, with lower respiratory infections claiming 4% of lives in Egypt, 10% in Ethiopia, 5.4% in Tunisia, and while good data is hard to come by, at least 10% in Sudan.
Even in Saudi Arabia, where decent medical care is available, and the threat of MERS is well recognized, we've seen estimates that many - perhaps even most - MERS cases go undetected.
In 2016, in EID Journal: MERS-CoV Antibodies in Humans, Africa, 2013–2014, we looked at the results of a seroprevalence study conducted in Kenya, which produced remarkably similar results to what Drosten & Memish et al found in KSA;  
1.52% vs. 1.43% positivity by rELISA and 0.15% vs. 0.18% positivity by PRNT for Kenya vs. Saudi Arabia, respectively.
Whether the MERS virus carried by African dromedaries pose the same human health risks as those on the Arabian peninsula remains an open question - but given the limits of surveillance and testing in the region - we’d be remiss in excluding that possibility simply because we haven't seen any confirmed cases.

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