Tuesday 13 August 2013

Baboons and MERS-CoV....

This post is based on @dspalten and his interest materials and analyses

Twitter yields all sorts of things to think about. Since the Lancet article on MERS-CoV-like antibody reactivity in dromedary camel sera, one tweeter has been a strong proponent of testing baboons, an African and Arabian old world, omnivorous monkey, for MERS-CoV.

A troup of Hamadryas Baboons (Papio hamdryas) in the
mountains , Saudi Arabia.
Hamadryads live for 30 to 35-years
Image from [3]
While there is probably a very long list of animals that humans may come into contact with that could be the primary or secondary host of MERS-CoV, I've listed some of the points and references (some websites at the bottom) supporting why we should add baboons to that testing list:

  • Baboons roam the horn of Africa (mid-eastern) and the southwestern Arabian peninsula including Yemen and the Kingdom of Saudi Arabia (KSA). They can climb trees.
  • They are highly adaptable to environmental change and will make use of human communities for food
  • They are known to acquire, harbour and suffer from, a number of bacterial and viral infectious diseases that affect humans and their fellow primates. These include tuberculosis, Salmonella , Shigella, Cryptosporidium, and viruses including HIV-2
  • In Africa, humans self-report baboon exposures to include:
    • Baboon to human:  eating baboon leftovers, from contact with faeces, screaming/breathing near humans, contamination of water sources, biting insects/flies
    • Human to baboon: contact with sick people, bad sanitation/hygiene/human wast disposal, insect bites/flies
  • Coronavirus particles were visualized in 1982 by Smith and colleagues baboon faeces from baboons and primates (some with diarrhoea/gastroenteritis, but no association). 
    • Persistent excretion was noted
    • The CoV-like particles did not grow on Vero cells at that time (MERS-CoV does)-because a picornavirus outgrew them (I hate it when that happens!). 
    • Weaned animals had a higher prevalence of CoV particles than unweaned primates
    • Other viruses found in these animals by this group of researchers include adenoviruses, herpesviruses, picornavirusesbacteriophage and an unknown virus particle
  • Signs of a spontaneous CoV outbreak in macaques and baboons was reported in a Russian (non-English) publication in 1994 by Goncharuk and colleagues. The spontaneous monkey CoV outbreak in an animal house was due by a CoV that serologically cross-reacted with the human CoV OC43. Cases were associated with pneumonia and enterocolitis.
  • Another Russian article in 1986 by Shevtsov an colleagues also notes monkey involvement in an animal nursery
  • Memish and colleagues noted in an article about Alkhurma haemorrhagic fever virus (AHFV) in the International Journal of Antimicrobial agents in 2010, that baboons could be found in the populous Makkah  (Mecca) region. While AHFV cases had been noted in this and other regions of the KSA, and may be occurring in baboons, no active surveillance was being carried out  for this virus.
  • Drewe and colleagues described in an article in 2012 in Emerging Infectious Diseases, the infections spread between baboons and baboons and humans in Cape Town, South Africa. These baboons, Papio ursinus, are a tourist attraction, coming into frequent contact with humans. 
    • The animals were seropositive for, or cross reactive to, cytomegalovirus and Epstein Barr virus (herpesviruses) and hepatitis A virus (HAV). 
    • The authors noted concerns about HAV which us transmitted via the faecal-oral route and the fact that 6/7 urban were HAV seropositive while 0/8 forest baboons had antibodies.
    • The data suggested a low risk, but a risk nonetheless  for zoonotic transmission of viruses
So we know that baboons are in the KSA area, they can harbour human or human-like viruses including possible coronaviruses, they adapt well to changes in their environment, they are highly mobile, they are not afraid of humans and they can be found in close contact with humans and areas of human habitation.

Definitely worth considering if anyone is getting around to some serious hunting for the source of MERS-CoV or other viral disease sources...or just for virus hunting in general. Great way to fight of the next pandemic would be to find the virus and source before we become the sentinel species of it's spread (hat tip to Crof). 

This also plays into the concept of "One Health" which recognizes that more than half of human infectious diseases originated in animals.

Just for the record, in case anyone interprets this or my posts on camels in such a way, I do not advocate the culling of an animal species because it is or may be a carrier of MERS-CoV. 

I do advocate quick reactions to create practices that reduce the risk of exposure to such animals. That is something that can be achieved in the interim while more scientific data are collected, even if we are not 100% certain of the transmission picture yet (if one can be 100% certain about anything in a biological system). 

I really don't think we need to go to the other extreme and decry new findings, such as those in camels, when we don't yet have enough data to prove or disprove their role in MERS. 

Education into reducing the risk of exposure may be the quickest and easiest way to minimize new MERS-CoV cases. In the meantime, expanded testing of other animals might help find the source.

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