Herpes simplex-like
infection found in a stranded bottlenose dolphin.
In 2001 a deceased stranded bottlenose dolphin was found in
the Canary Islands. It exhibited non-suppurative encephalitis (an inflammation
of the brain without pus,) and the aim of this paper was to discover the cause.
Tissue samples from the brain, liver and lungs were frozen at -80ᵒC, and in
order to determine the presence of viral agents, a RT-PCP was carried out for
morbillivirus and a PCR for herpesvirus.
Products of the PCRs were electrophoresed, and specific
bands were excised and sequenced. The
RT-PCR amplifies 426bp within a conserved region in the phospoprotein gene, and
the PCR amplifies between 215-315bp in the polymerase gene (this technique
produces sequences which are unique to each herpesvirus species). The sequenced
products were then compared to sequences already available in GenBank using the
BLAST search.
A specific band was not observed in the RT-PCR for
morbillivirus, and therefore we may conclude morbillivirus was not the reason for
the non-suppurative encephalitus. However, a herpesviral specific band of 250bp
was found in the lungs and brain. This sequence, referred to as EU003440, obtained
98% homology (with a p-distance of 0.02) with Human herpesvirus 1 (herpes simplex
virus 1, or HSV-1.) There were also similarities between EU003440 and Human
herpesvirus-2 (p-distance of 0.13), and the F-strain of HSV-1 (p-distance of
0.14)
The findings of this paper are spectacular, given that
previous occurrences of bottlenose dolphin herpesvirus show a large genetic
difference to EU003440 (with p-distance of between 0.45-0.69). I have (attempted to) attach the phylogram given in the paper, and it shows the surprising similarities
between this virus (known as EU003440) and human herpesvirus.
It is interesting to note that normally, instances of
herpesvirus which show high genetic relatedness to the human herpesvirus, have
been those which target non-human primates such as Baboon herpesvirus 2 and Cercopithecine
herpes 1.
This paper was coy in drawing a firm conclusion, vaguely
suggesting that “it could be concluded that [EU003440] may be considered a
HSV-like sequence.” Again, most of the reports about HSV-like sequences (HSV
being the Human herpes virus), are restricted to non-human primates – and “the
presence of an HSV-like sequence of possible human origin in a bottlenose
dolphin has not been previously described.”
Whilst this paper was the first to demonstrate the potential
of human herpes virus 1 zoonosis to the bottlenose dolphin, and zoonosis was
one of the key words of the paper – it was never again mentioned. I personally
think that this paper could have better explored the idea that EU003440 was of
a human herpes origin, which had been transmitted to a different species – that
of the bottlenose dolphin. Saying this, it was still an informative and interesting paper to read.
Possibly, the proximity of the Canary Islands to the
surrounding marine environment, could predisposition bottlenosed dolphins to
greater expose to pesticides, industrial pollutants and urban wastes. The
release of human micro-organisms through urban sewage to other environments has
already occurred with species such as the norovirus, and it appears that the
herpesvirus has taken the same route.
Esperon, F., Fernandez,
A., & Sanchez-Vizcaino, J. M. (2008). Herpes simplex-like infection in a
bottlenose dolphin stranded in the Canary Islands.Diseases
of aquatic organisms, 81(1), 73.
Hi Caz. Do you know how the herpes virus would cause non-suppurative encephalitis? Is there a particular product that causes swelling or is it an immune response within the dolphin?
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