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(technical, long, detailed)

[4] Cats - public health implications
Date: Thu, 13 Apr 2006
From: ProMED-mail <promed@promedmail.org>
Source: Eurosurveillance weekly release, vol 13,no 4, 13 Apr 2006
[edited]
<http://www.eurosurveillance.org/ew/2006/060413.asp#4>

The natural reservoir of influenza viruses is
generally considered to be wild waterbirds. In
this animal group, many types of influenza
viruses circulate without seeming to cause much
disease, and are therefore known as low
pathogenic avian influenza viruses. As well as
waterbirds, a number of other animals (including
humans) are occasionally infected with influenza
viruses (Table). However, a distinction needs to
be made between species which can occasionally be
infected by a particular influenza [virus] but
who rarely transmit on (so-called dead-end hosts)
and those species in which it seems that the
viruses are better adapted and transmitted
(propagating hosts).

Species/ Some influenza types that infect
Cats / Type A/H5N1
Dogs / Type A/H3N8
Horses / Type A/H7N7 and H3N8
Humans (pandemic and seasonal influenza) / Type
A, H3N2 and H1N1 also Types B and C
Marine Mammals (seals) / Type A/H7N7
Mustelids (including ferrets, mink and wild mustelids) / H3N2, H10N4
and H5N1
Pigs (swine fever)/ Type A / H1N1, H1N2, H3N2

Cats are among the species which can, and have
been, infected with influenza type H5N1. The
first time that this happened, and was reported,
was in December 2003 when a few large cats
(leopards and tigers) died in a zoo in Thailand
after being fed with infected poultry [1]. The
second natural event was a much larger H5N1
outbreak in zoo tigers, also in Thailand, which
had been fed chicken carcasses. Over 140 tigers
died, or were euthanised, and there was
convincing evidence of tiger to tiger
transmission [1,2].

Experimentally, it has been shown that domestic
cats can be infected with H5N1 through eating
infected material and that these infected cats
can transmit influenza to other cats. These
experimentally infected cats, though limited in
number, all became seriously ill when infected
and did not seem to shed the virus until they had
symptoms [3]. To date the only domestic cats that
have been conclusively shown to be infected have
been those found ill or dead in the intense
epizootic of H5N1 in wild birds on Rugen island
in Germany in February 2006 [1,4]. There have
been anecdotal reports of increased mortality in
cats during H5N1 outbreaks in other countries
(China, Iraq and Indonesia) but these have not
been confirmed by laboratory tests [5].

Unconfirmed reports of infections and deaths from
H5N1 in cats elsewhere should always be
interpreted cautiously. A recent preliminary
report of infected cats in Austria was eventually
not confirmed. Reports of positive serology for
H5N1 infection in non-bird species should be
treated with particular caution, especially if
these involve healthy animals and there has been
no actual evidence of H5N1 virus (PCR or viral
isolation). Serology for H5N1 may be helpful but
it needs to be undertaken in laboratories used to
handling H5N1 serology and able to exclude the
cross-reactions that can occur with H5N1 [6].

So what should be the recommended actions for cat
owners when H5N1 is reported in wild birds, and
what is the risk to humans? The Food and
Agriculture Organization has produced guidance
(see Box further). The difficult decision is when
to apply this guidance. This would be highly
recommended and reasonable guidance concerning a
poultry outbreak or in an intense epizoonotic
such as on Rugen Island. However, the actions
would probably be considered unreasonable and
over-cautious where there have perhaps [been]
just one or 2 birds infected. Veterinary
authorities in European Union countries have not
always tried to enforce guidance like this in the
latter circumstances. Also, as cat owners have
pointed out, there are practical difficulties for
some of the guidance -- like trying to keep cats
in houses.

[Box]
FAO Recommended Actions in Areas where H5N1 HPAI
has been diagnosed or is suspected in poultry or
wild birds [1]:
- - Report any evidence of significant bird
mortality (both wild and domestic) to the local
veterinary authority
- - Be especially vigilant for any dead or sick
cats and report such findings to the local vet
- - Make sure contact between cats and wild birds
or poultry (or their faeces) is avoided and/or
keep cats inside
- - If cats bring a sick or dead bird inside the
house, put on plastic gloves and dispense of the
bird in plastic bags for collection by local
veterinary animal handlers
- - Keep stray cats outside the house and avoid contact with them
- - If cats show breathing problems or nasal
discharge, a veterinarian should be consulted
- - Do not touch or handle any sick-looking or dead
cat (or other animal) and report to the
authorities
- - Wash hands with water and soap regularly and
especially after handling animals and cleaning
their litter boxes or coming in contact with
faeces or saliva
- - Dogs can only be taken outside the premises if kept restrained
- - Do not feed any water birds
- - Disinfect (e.g. with bleach 2-3 percent) cages
or other hardware with which sick animals have
been transported or been in contact
- - Wash animal blankets with soap or any other commercial detergent
- - Those living on farms should also be aware of
the risk that semi-domestic cats (feral
domesticated and farm cats) could shed the virus
into poultry feed or housing, leading to exposure
of poultry.

The risk to humans from an H5N1-infected cat is
hard to quantify [6]. Cats naturally hunt wild
birds, will choose sick birds and have close
contact with humans as companion animals. Given
that one cat can infect another, the risk to
humans cannot be zero. However, as H5N1 remains
poorly adapted to humans, the cat's infection
will not cross over easily [7]. The present
evidence is that cats with infectious H5N1 are
quite ill, so the risk of acquiring H5N1 from a
[clinically normal] cat may be negligible. Also,
risk will be minimal in areas where there is no
H5N1. While it could be argued that owners should
be cautious around cats with respiratory
infections, cats (like humans) catch many of
these. For example, there are common infections
confusingly called 'cat fluí' which are not
caused by an influenza virus at all but are due
to either a cat calicivirus or herpesvirus.
Humans are actually at considerably greater risk
from other zoonoses in cats such as toxocara,
toxoplasmosis and ringworm, and basic hygiene
measures for handling companion animals are
important to protect against these.

References:
Food and Agriculture Organization . Animal Health
Special Report H5N1 in Cats FAO 2006
(<http://www.fao.org/ag/againfo/subjects/en/health/diseases-cards/avian_
cats.html>)

Thanawongnuwech, R. et al. Emerg Infect Dis 2005; 11: 699-701.

Rimmelzwaan GF, Van Riel D, Baars M et al
Influenza A virus (H5N1) infection in cats causes
systemic disease with potential novel routes of
viral spread with and between hosts. Am J Path
2006; 168: 176-183

European Commission. Statement of the Standing
Committee on the Food Chain and Animal Health
Brussels 1 Mar 2006
(<http://www.europa.eu.int/rapid/pressReleasesAction.do?reference=MEMO/0
6/104&format=HTML&aged=0)#uage=EN&guiLanguage=en>)

Kuiken T, Fouchier R, Rimmelzwaan G, Osterhaus A,
Roeder P. Feline friend or potential foe? Nature
2006: 440; 741-2

Puzelli S, Di Trani L, Fabiani C, Campitelli L,
De Marco MA, Capua I, Aguilera JF, Zambon M,
Donatelli I. Serological analysis of serum
samples from humans exposed to avian H7 influenza
viruses in Italy between 1999 and 2003. J Infect
Dis 2005; 192: 1318-22

European Centre for Disease Prevention and
Control. The Public Health Risk from Highly
Pathogenic Avian Influenza Viruses Emerging in
Europe with Specific Reference to type A/H5N1. 5
Jan 2005.
(<http://www.ecdc.eu.int/avian_influenza/H5N1_European_Risk_Assessment_E
CDC_051019.pdf>)

Articles referenced
- - Article 1: Measles outbreak in Germany: update.
Ref : Euro Surveill 2006;11(4):E060413.1
- - Article 2: Seasonal influenza activity for
2005-2006 season seems to be ending in most
European countries. Ref : Euro Surveill
2006;11(4):E060413.2
- - Article 3: Rise in antimicrobial resistance in
invasive isolates of Escherichia coli and
Enterococcus faecium in Ireland. Ref: Euro
Surveill 2006;11(4):E060413.3
- - Article 4: Rise in antimicrobial resistance in
invasive isolates of Escherichia coli and
Enterococcus faecium in Ireland. Ref: Euro
Surveill 2006;11(4):E060413.3
- - Article 5: H5N1 infections in cats - public
health implications. Ref: Euro Surveill
2006;11(4):E060413.4

Issued by:
Influenza team
European Centre for Disease Prevention and Control
Stockholm, Sweden
(<influenza@ecdc.eu.int>)

- --
ProMED-mail
<promed@promedmail.org>

[The team's advice, recommending the selective
application of the detailed FAO guidelines when
there are H5N1 outbreaks in poultry, or intense
outbreaks in wild birds (e.g. on Rugen Island) --
and not where there have perhaps been just one or
2 birds infected -- is reasonable. However, it
seems advisable also to exercise a critical
approach, if not actually discouraging the
development and maintenance of outdoor
populations of un-owned cats. Such populations
are particularly risky where H5N1 infections have
been detected in domestic or wild avians. -
Mod.AS]