Current and future zoonotic threats from cats and dogs - Veterinary Practice
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Current and future zoonotic threats from cats and dogs

David Grant reports on an informative webinar on parasite control

CURRENT and future zoonotic
threats from cats and dogs
was the
title of an informative webinar
presented by Ian Wright at the end
of April.

Mr Wright is a practising vet who has
developed considerable parasitological
expertise by virtue of a master’s
degree in the subject and also by his
role as a member

of the European
Scienti c Counsel
Animal Parasites
(ESCCAP). He was accompanied by
Anthony Chadwick, founder and MD
of The Webinar Vet, and the webinar
was sponsored by Elanco.

I am relatively new to live webinars
but found it to be very easy to
participate. Having had a couple of
reminders from The Webinar Vet, it
just took one click of the mouse and
I was in. The experience was virtually
the same as being in the lecture hall
at a congress except that I was in the
comfort of my own home.

The sound was perfect and the
PowerPoint presentation was clear. Ian
is a very relaxed speaker with a good
sense of humour and the hour’s lecture ew by. The subject is potentially vast
and Ian decided to concentrate on
parasitic zoonoses for much of the

First parasite up for discussion, not
surprisingly, was Toxocara canis. He went
through the life cycle, familiar to most
if not all of us, but then went on to
elaborate on the public health aspects.
Some 3% of people in the UK are
sero-positive for Toxocara. The risk is
higher in households with a dog and
higher still where there is a litter of

The consequences of human
contagion can be devastating. Of
these, ocular infections are perhaps
the most well known but visceral and neurological forms are equally
important. Thus, the potential danger
ranges from loss of sight to CNS
problems such as epilepsy. Other
covert forms exist but it is not easy to
correlate sero positivity with clinical

The true incidence of toxocariasis
is unknown as it is not noti able.

Although adults
can be infected,
it is two to
most at risk – a very sobering thought for parents of
young children. Embryonated eggs are
infectious and it caught my attention
that embryonation can take place in
the coat of the animal, in addition to
the places that we tend to traditionally
think of: soil, sand pits and parks, for

So how can this disease be
prevented? The answers are very
simple. These are regular worming of
pets, picking up faeces and very good
hand hygiene. As a dermatologist I was
particularly interested in the role of
hand hygiene, as this is so important in
the control of multi-resistant bacteria.

It is equally important in
parasitological diseases. The eggs
cannot be destroyed by disinfectants so
removal of them with good old soap
and water is what is required.

Regular worming was discussed at
length and also in the question and
answer session at the end. Worming
twice a year is ineffective in controlling
this parasite. The bare minimum is
four times a year and monthly is to be preferred in higher risk situations
– families with children, for example.
Puppies should be wormed every two
weeks until weaning.

Monthly worming
means zero shedding

In the discussion afterwards, Ian
made the point that zero shedding
of eggs will be achieved by monthly
worming. Surely the way forward was
my thought. In terms of products
available we are spoilt for choice
and consideration should be given
to achieving good compliance and
therefore an individual owner’s ability
to use the products properly. Here,
education is the most important factor.

The next parasite discussed was
Echinoccus granulosus, a tapeworm that is
non-pathogenic in canids but a serious
zoonotic risk to humans, which can
lead to hydatid cysts. Dogs acquire this
parasite from eating infected carcases,
mainly sheep.

The parasite has a well-defined
geographical incidence and in these
areas vets are well aware of the
problem. Advice given is to worm with
praziquantel every 4-6 weeks and there
is a need to persuade owners of this as hydatid disease in humans is very
unpleasant and cases occur every year.
Good compliance is essential.

I had forgotten that it is possible to
acquire the dog tapeworm Dipylidium
. This can occur as a result
of the accidental ingestion of fleas,
including parts of fleas under the fingernails for example. Once again,
regular worming and in this case flea
control allied with hand hygiene should
prevent human infection.

Hand hygiene was a recurrent theme
in this webinar. With a combination of
potential problems from multi-resistant
bacteria and equally nasty parasites, I
would hope that there would be many
practice meetings in
the weeks after this
webinar to hammer
home the importance
of this.

Giardia and

Ian moved on to
zoonotic protozoan
diseases. Those
discussed were Giardia
and Toxoplasma. With
both these diseases
there is no chemical
prophylaxis. Most
important are, as
before, good hand
hygiene and food and
water monitoring.

Giardia in people
is often acquired
abroad from faecally
contaminated food or
water. Giardia duodenalis
is the pathogen
implicated in a wide variety of species
including dogs, cats and man. This
parasite can be transferred from owner
to dog and vice versa. Resistance to
fenbendazole is a potential problem,
making an accurate diagnosis advisable.
There is an ELISA test that is very

Along with Toxocara, Toxoplasma
is a parasite with a high profile
among veterinary practice clients,
mainly because of the risk to pregnant
women. Cats are the definitive host but
shed oocysts only intermittently. The
diagnosis rests on identifying oocysts in
the faeces, which is difficult, and by a
serological test. The problem with this latter test is that it does not necessarily
identify active infection.

Apart from acquiring the disease by
contact with cat faeces, the disease can
occur after eating undercooked meat
and fruit and vegetables that have not
been washed. The consequences in
pregnant women are well known but
there are behavioural implications too,
with a possible link to a whole range of
mental illnesses.

This appears to be a “clever” parasite
as it can affect mouse behaviour, for
example, to the extent of making cat
urine appealing and thus increasing the possibility of a mouse being eaten.
The zoonotic risk can be minimised
by good hand hygiene, disposal of
faeces where possible and ensuring
that meat is properly cooked and fruit
and vegetables washed before eating.
The risk from cats is very much smaller
than from contaminated food.

The final part of
this webinar looked
at future threats. The
diseases discussed
were rabies,
Echinoccus multilocularis
and leishmaniasis.

As far as rabies
is concerned, 95%
of cases worldwide
occur in Africa
and Asia. It is still
endemic in the
USA and Canada.
Although it continues
to be a risk in the
EU, numbers of
cases have declined

The same cannot
be said for E.
. This
is a serious and
significant zoonosis
that is spreading
west and knocking at the UK shores. The definitive host
is the fox and paradoxically success in
diminishing rabies cases has favoured
fox multiplication, and the red fox is the main risk for spread of this

It is important to keep tapeworm
control in place to minimise the risk
of this parasite entering the country,
and with relaxation of entry rules
veterinary advice prior to leaving the
UK is essential. If it were to arrive,
praziquental treatment monthly would
be required, but in Ian’s words “we
would be stuck with it”.

Finally, Leishmania was discussed.
Currently, the sand y vector is not present in the UK, although with
climate change this could quite quickly
alter. At the moment the emphasis is
on advice to be given to clients wishing
to take their dogs abroad.

There is a Leishmania vaccine which
gives approximately 93% protection.
Use of insect repellents as collars or
pyrethroid products should be added
and will reduce the risk further.

Complicated treatment

Although treatment regimes exist,
these are complicated and most
cases will not be cured, thus posing
a continued risk to the owners. The
prognosis in the long term is therefore
guarded. Clearly, considerable risk is
associated with re-homing dogs from
endemic areas in southern Europe.
The disease in humans is most likely in
immune-compromised individuals, in
whom it can be fatal.

Current diagnostic methods were
outlined, including blood smears, fine
needle aspirate of bone marrow and
lymph nodes, skin and lymph node
biopsy and serological tests. These and
treatments were brie y described and
perhaps would be best performed by
those experienced in the disease.

I thoroughly enjoyed this excellent
webinar but more was to come.
Anthony Chadwick, in his very relaxed
style and acting as chairman, passed on
numerous questions.

This is a major advantage of
this form of CPD, compared to a
congress lecture. We had 40 minutes
of questions and anyone who left
the webinar early missed out. And, as
Anthony pointed out, nobody would
notice if you left early! He also cleverly
only mentioned questioners by their first name: no need to worry about
asking a foolish question.

Participants were from all over
the world from places as diverse as
Australia, Egypt, Moscow and most
parts of continental Europe as well as
the UK.

Finally, Ian left us with two useful
websites. It has not been possible
to cover here all that was said in the
webinar but more detail and guidelines
can be found on and
on the BSAVA website

Anthony Chadwick, his team and
Ian Wright are to be congratulated on
a very informative, entertaining and
useful webinar – thanks also to Elanco
Companion Animal Health.

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