A Strategy for Developing a MERS Camel Vaccine in order to Protect Humans John Lowenthal Deakin University, Australia
Since 2012, there have been 2220 cases of MERS-CoV with 790. Controlling the epidemic is difficult in the absence of approved vaccines and therapeutics. Dromedary camels represent the natural host for MERS and shed the virus asymptomatically. The mechanism of camel to human transmission unclear, but primary cases have been associated with direct camel contact. Humans are a transient terminal host, but there is the potential for mutations that could increase viral transmission, virulence and host range.
A one-health approach has recently been used in Australia to control zoonotic Hendra virus (HeV) outbreaks. HeV was first identified in 1994 during an outbreak of severe respiratory disease in horses and since then there have been over 100 cases in horses (100% fatality) and 7 humans (4 deaths) who contracted HeV directly from horses. HeV vaccine development started in 2005 with animal trials starting in 2010. In late 2012 the vaccine was approved for use in horses for high-risk and outbreak situations and a commercial vaccine was registered for horses in 2015. To date, there have only been 20 cases of HeV in horses since 2013 and no vaccinated horses have contracted HeV. Clinical trials are currently underway for a human HeV vaccine and therapeutic monoclonal antibody. Since MERS epidemiology shares similarities with HeV, a similar one-health approach involving mass vaccination of reservoir hosts to block transmission to humans could be part of zoonotic disease-control strategy.
The most effective way of controlling the MERS epidemic is to provide a multi-pronged attack. Elderly and compromised humans are highly susceptible to MERS infection and are the primary source for human to human transmission. The only current form of treatment is long-term intensive supportive care, resulting in a high-risk environment for viral transmission. Vaccination and therapeutic antibody-treatment of health care workers and family members are needed to limit viral spread from symptomatic human cases. The second component is to prevent viral spread to the human population in the first place by mass vaccination of dromedary camels as the best way of tackling the endemic. There are current trials underway in the Arabian Peninsula that are assessing of two MERS vaccines in camels. Based in the HeV experience, vaccines and therapeutic antibodies may be available in the near future.
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