Variegated Squirrel – Credit Wikipedia
As it’s been nearly a week since I’ve written about a newly discovered, deadly zoonotic pathogen affecting humans (see CDC & EID Journal On The Recently Discovered Bourbon Virus), allow me to introduce you to a recently identified bornavirus that appears to be behind a cluster of acute fatal encephalitis in three squirrel breeders in Europe.
18.02.2015, 16:28 clock | dpa
In Saxony-Anhalt three Variegated squirrel breeders are apparently died of a previously unknown virus. Scientists from the Friedrich-Loeffler-Institut on the island of Reims discovered in an animal of a deceased person to a novel Borna
Variegated squirrels (Sciurus variegatoides) are a tree squirrels in the genus Sciurus that are native to Central America (yes, I looked it up), and apparently are being imported in Europe. Today the ECDC has published a Rapid Risk Assessment on the possible zoonotic transmission of a new bornavirus from these rodents to humans.
A recently reported cluster of acute fatal encephalitis in three squirrel breeders possibly related to an infection with a newly identified bornavirus is an unusual event. The novel nature of this occurrence requires that additional investigations are undertaken into the role of a new bornavirus in the aetiology of these cases, the identification of natural hosts, reservoir and the transmission route.
Nevertheless, pending the completion of the cluster investigation, it is advised that feeding or direct contact with living or dead variegated squirrels should be avoided, as a precautionary measure.
Further investigations are ongoing to characterise these cases. In addition, testing of cases of human encephalitis for this newly identified bornavirus, especially in areas where the presence of bornavirus is documented in animals, can contribute to a better understanding of the risk of bornavirus infection in humans.
Event background information
On 19 February 2015 Germany posted a message on EWRS, reporting three cases of fatal encephalitis in residents of the state of Saxony-Anhalt. The first clinical case was seen in 2011, and the second and the third in 2013 in different hospitals. Affected persons were males aged 62 to 72 years and of age-typical health status. Each of them was known to breed variegated squirrels (Sciurus variegatoides), a type of tree squirrel common to Central America that can be kept as an exotic outside pet. They knew each other but did not live in close proximity to one another. It is unclear whether they exchanged animals.
During the prodromal phase, which lasted for two weeks or longer, the patients presented with fever and shivering, fatigue, weakness and walking difficulties. Due to increased confusion and psychomotor impairment they were admitted to neurology wards where they developed ocular paresis. They rapidly deteriorated within a few days and died after some time in intensive care, despite mechanical ventilation. Investigations for usual (non-purulent) encephalitis aetiologies performed at the Bernhard Nocht Institute for Tropical Medicine in Hamburg at first did not produce any evidence for known pathogens in cerebrospinal fluid and samples of brain tissue of the deceased.
The Friedrich Loeffler Institute on Riems Island investigated the carcass of one variegated squirrel belonging to the third patient. Genetic analysis of a tissue sample pool of the animal using a metagenomics approach produced sequences of a newly identified type of bornavirus. Further molecular and immunohistochemical analysis of brain tissue from the three deceased patients confirmed presence of this virus in the human cases as well. The newly identified virus is clearly different from all currently known bornaviruses.
Tissue and cerebrospinal fluid collections from bio banks are now being investigated for the identification of additional cases. Previously unresolved cases of encephalitis are being re-evaluated in view of the new virus. Breeders/owners of variegated squirrels will be questioned as to their health condition and asked about anecdotal knowledge of possible fatal cases among breeders/owners. The available evidence is compatible with this virus being a zoonotic pathogen. In limited testing of additional variegated squirrels from one breeder and a zoo no other animal was found to be positive for this infection, but further tests are ongoing. Breeders are asked to send in deceased animals to the Friedrich Loeffler Institute.
This cluster of acute fatal encephalitis in three squirrel breeders possibly related to an infection with a newly identified bornavirus is an unusual event. The role of new bornavirus in the aetiology of these cases, the identification of natural hosts, reservoirs and transmission route require additional investigations.
Nevertheless, pending the completion of the cluster investigation, feeding or direct contact with living or dead variegated squirrels should be avoided as a precautionary measure.
Further investigations are ongoing to characterise these cases. Testing cases of human encephalitis for this newly identified bornavirus, especially in areas where the presence of bornavirus is documented in animals, can contribute to a better understanding of the risk of bornavirus infection in humans.
We’ve seen other exotic diseases brought in via imported animals, including a little over a decade ago – the United States experienced an unprecedented outbreak of Monkeypox - when an animal distributor imported hundreds of small animals from Ghana, which in turn infected prairie dogs that were subsequently sold to the public (see 2003 MMWR Multistate Outbreak of Monkeypox --- Illinois, Indiana, and Wisconsin, 2003).
Now that a virus has been identified and linked to their illness, it will be interesting to see how many unresolved cases of encephalitis end up being due to the same etiology.