Download Pet ownership in immunocompromised children—A review

ARTICLE IN PRESS
European Journal of Oncology Nursing (2006) 10, 117–127
www.elsevier.com/locate/ejon
Pet ownership in immunocompromised
children—A review of the literature and survey
of existing guidelines
S. Hemsworth, B. Pizer
Oncology Unit, Royal Liverpool Children’s NHS Trust, Eaton Road, Liverpool, UK
KEYWORDS
Animals-domestic;
Zoonoses;
Animals;
Immunocompromised-host;
Disease;
Risk
Summary Pet ownership has been associated with both emotional and physical
health benefits. However, owning pets may also pose health risks to immunocompromised patients through zoonotic transmission of disease. Our initial impression
was that there is a lack of any evidence base in information given by health care
professionals regarding these risks. We therefore aimed to produce evidence-based
guidelines addressing this issue. A Pubmed search was undertaken and a variety of
literature on zoonoses reviewed. Existing guidelines were evaluated and a survey of
all Paediatric Oncology Centres in the UK performed. There is a paucity of level 1 and
2 data addressing this issue and clearly more studies, particularly Randomised
Controlled Trials (RCTs), are required. Nevertheless, general themes emerged and
certain specific guidance was produced based on that produced by the Centres for
Disease Control and Prevention in the US. Animal-associated pathogens of concern
include Toxoplasma gondii, Cryptosporidium spp., Salmonella spp., Campylobacter
spp., Giardia lamblia, Rhodococcus equi, Bartonella spp., Bordetella bronchiseptica, Chlamydia psittaci and dermatophytes. Despite this, the literature would suggest
that with the exception of Bartonella henselae and dermatophytes only a relatively
small number of infections in people are likely to be associated with pet contact.
The majority of pet species do not appear to pose a major risk to immunocompromised children. Some animals, particularly reptiles, should be avoided because of
the high risk of salmonellosis. Guidelines include general advice on good hygiene
practices, veterinary care, pet foods, purchasing of new pets and age restrictions.
Health care professionals should actively enquire about household pets and provide
accurate information and practical advice on how to minimise the risk of infection.
However, the overall benefits of the human–animal bond must be considered and
with proper handling and husbandry immunocompromised patients should be able to
continue to enjoy the significant benefits of pet ownership.
& 2005 Elsevier Ltd. All rights reserved.
Corresponding author. Tel.: 0151 252 5971; fax: 0151 252 5676.
E-mail address: [email protected] (S. Hemsworth).
1462-3889/$ - see front matter & 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ejon.2005.08.001
ARTICLE IN PRESS
118
S. Hemsworth, B. Pizer
Zusammenfassung Der Besitz eines Haustieres hat offenkundig positive Auswirkungen auf den psychischen und körperlichen Gesundheitszustand des Haustierbesitzers. Bei Patienten mit abgeschwächtem Immunsystem stellen Haustiere jedoch
aufgrund möglicher Übertragungen zoonotischer Krankheitserreger potentielle
Gesundheitsrisiken dar. Wir haben festgestellt, dass es für Informationen, die von
Medizinern bezüglich dieser Risiken erteilt werden, bislang nahezu keine wissenschaftlichen Belege gibt. Daher haben wir uns zum Ziel gesetzt, evidenzbasierte
Richtlinien zu dieser Fragestellung zu entwickeln. Es wurde eine PubMed-Recherche
durchgeführt und die Fachliteratur über Zoonosen gesichtet. Des weiteren wurden
vorhandene Richtlinien evaluiert, und es erfolgte ein Survey sämtlicher kinderonkologischer Zentren in Großbritannien. Es besteht ein Mangel an Level-1- und
Level-2-Daten zu dieser Fragestellung. Ohne Zweifel sind weitere Studien
erforderlich, insbesondere randomisierte kontrollierte Studien. Nichtsdestoweniger
kristallisierten sich einige allgemeine Leitgedanken heraus, und es wurden relativ
präzise Anleitungen erarbeitet, welche auf denjenigen der US-amerikanischen
Centers for Disease Control and Prevention basieren. Zu den Infektionserregern, die
bei Tierkontakten übertragen werden können, zählen Toxoplasma gondii, Cryptosporidium spp., Salmonella spp., Campylobacter spp., Giardia lamblia, Rhodococcus
equi, Bartonella spp., Bordetella bronchiseptica, Chlamydia psittaci sowie
Dermatophyten. Aus der Fachliteratur geht jedoch hervor, dass abgesehen von
Infektionen durch Bartonella henselae und Dermatophyten wahrscheinlich nur
wenige menschliche Infektionen durch Kontakte mit Haustieren verursacht werden.
Die Mehrzahl der Haustierarten stellt für Kinder, die an einer Immunschwäche
leiden, kein größeres Risiko dar. Auf einige Tiere, insbesondere Reptilien, sollten
jedoch wegen des relativ hohen Salmonellose-Risikos verzichtet werden. Die
Richtlinien enthalten unter anderem Informationen zu Hygienefragen, tiermedizinischer Versorgung, Futter für Haustiere, den Kauf neuer Haustiere sowie
Alterseinschränkungen. Mediziner müssen gezielt danach fragen, ob in dem
betreffenden Haushalt Haustiere vorhanden sind. Sie müssen präzise Informationen
und praktische Ratschläge erteilen, wie das Risiko von Infektionen möglichst gering
gehalten werden kann. Dabei sind jedoch die Vorteile der emotionalen Bindung
zwischen Mensch und Tier zu berücksichtigen. Bei adäquatem Verhalten und
korrekter Tierhaltung können auch Patienten mit Immunschwäche die signifikanten
Vorteile nutzen, die sich aus dem Besitz eines Haustieres ergeben.
& 2005 Elsevier Ltd. All rights reserved.
Introduction
Pet ownership has been associated with both
emotional and physical health benefits. The bond
between humans and animals has been recognised
for many years. It has now been widely accepted
that pets bring a unique sense of stability, love and
continuity to people’s lives and some studies
indicate that pets can have a positive influence
on the quality of life (Spencer, 1992). There has
also been an increase in the popularity of urban
(city) farms and petting zoos; the aim of which is to
enable city-dwelling children to become involved
with animals. Whilst the emotional benefits of pet
ownership are recognised, it is also known that
some animals can transmit zoonotic diseases
and these may pose serious health risks especially in young children, the elderly, pregnant
women, organ recipients and immunocompromised
patients. The World Health Organisation defines
‘‘zoonoses’’ (Zoonosis, singular) as ‘‘Those diseases
and infections, which are naturally transmitted
between vertebrate animals and man’’ (WHO,
1959).
With regards to cancer patients, both children
and adults, there are no formal guidelines in the UK
for safe pet handling whilst on chemotherapy and
historically much advice seems to be ‘‘physician’s
preference’’, with little evidence behind such
decisions. We therefore decided to review the
literature on zoonoses and whether they posed any
threat to immunocompromised patients and to look
for any guidelines produced. From our review we
aimed to identify any risks to immunocompromised
patients associated with pet ownership and to
produce guidelines, evidence-based where possible, for staff and families on reducing the risks of
animal acquired infections.
ARTICLE IN PRESS
Pet ownership in immunocompromised children
Methods
Literature search: A Pubmed search was undertaken on zoonoses and studies of zoonotic infections in immunocompromised patients.
UK survey: A survey of paediatric oncology units
in the UK was carried out to establish if there were
any existing written evidence-based guidelines in
use in these units.
Expert advice: In recognition of the importance
of veterinary advice, communication took place
with veterinarian specialists based in the UK and
USA.
Existing guidelines: We looked to see if any
evidence-based guidelines already existed.
Results
Whilst a wealth of information is available on
general zoonoses, there appear to be no randomised controlled trials on the subject. Zoonotic
infections encompass a wide range of viral,
bacterial, parasitic and fungal infections. Over
250 organisms are known to cause zoonotic infections (Greene, 1995) and whilst this list is formidable, many of the diseases are rare and the chances
of humans contracting a zoonotic disease are small.
The vectors of many zoonoses are not necessarily
household pets, only approximately 30–40 vectors
(Wong and Feinstein, 1999). These may include
humans, farm animals, feral and exotic animals
sold as pets; however, of these only a selective few
have been reported with greater frequency in
people with immunodeficiency and AIDS (Greene,
1995).
The various modes of transmission are shown
below:
Ingestion route.
J Faeces.
J Urine.
J Saliva.
J Milk.
Inhalation.
J Aerosol.
Direct contact with animals, bedding, etc.
Blood-borne.
The most common mechanisms of transmission
are by inhalation or ingestion, but transmission may
also occur following bites or scratches or by direct
contact with arthropods. Many zoonotic agents
are found naturally in soil, water or vegetation.
Animals may contaminate the environment but in
119
most cases, people and animals acquire infections
simultaneously and independently of each other
(thus they may not strictly be zoonoses but
diseases that man and animals have in common).
Therefore, it is likely that most zoonotic infections
in immunocompromised patients are acquired from
environmental exposure rather than contact with
pets (Grant and Olsen, 1999).
Table 1 shows an overview, by no means allinclusive, of the more common zoonotic diseases
that may be acquired from pet animals.
The following infections may be of greatest
concern to immunosuppressed people (USPHS,
1997):
Campylobacteriosis.
Bartonellosis (Cat Scratch Disease (CSD)).
Cryptosporidiosis.
Giardiasis.
Salmonellosis.
Toxoplasmosis.
Campylobacteriosis is a disease caused by a
group of Gram-negative rods—Campylobacter
spp., that are commensal flora of animals. Campylobacter jejuni is frequently isolated from dogs or
cats acquired from pet shops, kennels and animal
shelters. However, uncooked meat, particularly
poultry, is probably the main source of infection.
The disease is transmitted via the faecal–oral route
from food or water sources. Contaminated water
supply, from migrating waterfowl or herbivores may
be a source of infection for outdoor pets. Children
less than 5 years old with a newly acquired puppy
have the highest risk of infection (Salfield and
Pugh, 1987). Signs of infection may include intense
abdominal pain, bloody diarrhoea, pyrexial, tenesmus and faecal leukocytosis. Immunocompromised
patients develop recurrent diarrhoea, dehydration
and bacteraemia.
Bartonellosis (CSD) is a bacterial infection caused
by Bartonella henselae. Cats can spread B. henselae to people by bites and scratches. Lymph nodes,
especially those around head, neck and upper limbs
become swollen. Headaches, fatigue and poor
appetite are also reported. Kittens are more likely
to be infected and pass the bacterium to humans
(Angelu et al., 1994; Zangwill et al., 1993). About
40% of cats carry the bacterium and do not show
signs of illness. Immunosuppressed patients are
more likely to have complications of CSD. Although
B. henselae has been found in fleas, there is no
evidence that a bite from an infected flea may lead
to CSD (Koehler et al., 1994; Regenery et al., 1992).
Cryptosporidiosis is an intestinal infection
caused by a parasite Cryptosporidium parvum. It
Animal Species
Rabbits, rodents
Dogs
Cats
Cats
Cats, dogs, ferrets,
farm animals,
horses
Wild birds
(pigeons)
Cats, dogs, farm
animals, ferrets,
horses
Arthropod infections
(Skin mites and ticks)
Ascaridiasis
(Roundworm infection)
Bartonellosis (Cat
scratch disease)
Campylobacteriosis
Cryptococcosis
Cryptosporidiosis
Mycotic
Cryptococcus
neoformans
Parasite
Bacteria
Campylobacter
Faecal–oral route
Isolated from the soil,
usually in association with
bird droppings
Inhalation of airborne
yeast cells and/or
basidiospores
Generally spread by eating
or drinking contaminated
food or water,
unpasteurised milk, and by
direct or indirect contact
with faecal material from
an infected person, animal
or pet (especially puppies
and kittens)
Cat scratch, bite
Ingestion of infective eggs
in environment
Direct contact with
infected animals
Transmission
Watery diarrhoea,
accompanied by abdominal
cramps. Nausea, vomiting,
fever, headache and loss of
appetite may also occur.
Rarely, the parasite can cause
an inflammation of the gall
bladder or infect the lining of
the respiratory tract causing
pneumonia
Initial pulmonary infection is
usually asymptomatic. Most
patients present with
disseminated infection,
especially
meningoencephalitis
Mild to severe infection of the
gastrointestinal system,
watery or bloody diarrhoea,
fever, abdominal cramps,
nausea and vomiting. A rare
complication of
Campylobacter infection is
Guillain–Barre syndrome
Skin Lesions, infection at point
of injury, lymphadenopathy
Dependent on organ damaged
during larval
migration—visual, neurologic
or tissue damage
Temporary dermatitis
Human infestation is transitory
as mites do not reproduce on
human skin
Signs and Symptoms
120
Cryptosporidium
Bacteria
Parasite
Parasite
Category
Bartonella henselae
Toxicara canis
Toxicara catis
Toxascaris leonina
Sarcoptes mange mite
Cheyletidae
Dermanyssidae
Macronyssidae
Trixacarus caviae
Organism
Zoonoses potentially transmitted by pets and petting/farm animals.
Disease
Table 1
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S. Hemsworth, B. Pizer
Cats, cows, dogs,
goats, horses, pigs,
rabbits, rodents
Cows
Dogs, ferrets
Cats, dogs
Ferret
Fish
Rabbit rodents
Birds
Horses
Dermatophytosis
(ringworm)
E. coli
Giardiasis
Hookworm
Influenza
Mycobacteriosis
Pasteurellosis
Psittacosis
Rhodococcus equi
Rhodococcus sp
Chlamydia psittaci
Pasteurella multocida
Mycobacterium
marinum
Influenza virus
Ancylostoma caninum
Ancylostoma
braziliense
Ancylostoma
tubaeform
Uncinaria
stenocephala
Giardia intestinalis
(Giardia lambia)
Escherichia coli 0157
Microsporum cani
Trichophyton
mentagrophytes
Bacteria
Bacteria
Bacterial
Bacteria
Viral
Parasite
Parasite
Bacteria
Mycotic
R. equi is readily found in
soil, especially where
domesticated livestock
graze. Infection in humans
derives from
environmental exposure
Inhalation of dried
secretions from infected
birds
Bites/scratches (bacteria
found in mouth of animals)
Aquarium water localised
infections following access
through broken skin
Via aerosol from infected
ferret
Ingestion of infective eggs
or contact with
contaminated soil
Ingestion of contaminated
water or food, faecal–oral
route
Ingestion of contaminated
food, faecal–oral route
Direct or indirect contact
with asymptomatic
animals or with skin lesions
of infected
animals,contaminated
bedding
Pneumonia, pulmonary
abscesses
Fever, headache, muscle
aches, and a dry cough.
Pneumonia
Cutaneous infections,
bacteraemia
Skin Lesions, disseminated
disease in
immunocompromised patients
Fever, muscle aches, headache
Pruritic skin lesions
Intestinal bleeding, swelling
and pain
Diarrhoea, fever, severe
abdominal cramps
Severe, bloody diarrhoea
Kidney failure
Often mild, self limiting;
scaling, redness, and
occasionally vesicles or
fissures
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Pet ownership in immunocompromised children
121
Reptiles, birds,
cats, chicks, dogs
ducklings, ferrets,
fish, horses,
rabbits,
Cats, dogs,
rabbits, rodents
Cats
Salmonellosis
Tapeworm
Toxoplasmosis
Toxoplasma gondii
Parasite
Parasite
Bacteria
Salmonella
Dipylidium
Category
Organism
Ingestion of raw or
undercooked infected
meat, especially pork,
lamb, or raw milk
containing parasite. The
parasite is shed primarily
in the faeces of infected
cats. Humans can become
infected by the ingestion
of food, water, or dirt
contaminated with cat
faeces. Toxoplasmosis can
also be acquired through a
transplacental infection,
when an infected mother
passes the infection to her
foetus
Ingestion of infected flea
Ingestion of foods
contaminated with animal
faeces. Faecal–oral route
Transmission
Flu-like symptoms,
lymphadenopathy
Proglottids are passed in
faeces or are found round anus
causing itching
Acute gastroenteritis with
sudden onset of abdominal
pain, diarrhoea, nausea, and
fever. May lead to septicaemia
Signs and Symptoms
Data contained within this table has been obtained predominantly from the following references: Chomel (1992), University of California Institutional Animal Care and use Committee
(1996), Centers for Disease Control. National Center for Infectious Diseases (2004).
Animal Species
Disease
Table 1 (continued )
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S. Hemsworth, B. Pizer
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Pet ownership in immunocompromised children
may be acquired from young domestic herbivores
(calves, lambs, kids and piglets) with diarrhoea or
less commonly pets such as cats and dogs. Environmental exposure is usually from drinking water
contaminated by animal or human sewage (Greene,
1995). Immunocompetent people show signs of
abdominal pain and self-limiting diarrhoea of 5–10
days, whilst immunocompromised patients may
have severe water debilitating chronic diarrhoea
which may be refractory to therapy (Glaser et al.,
1998).
Giardiasis is a gastrointestinal infection caused
by the parasite Giardia intestinalis (Giardia lamblia). The parasite survives outside the body and in
the environment for long periods of time. It is found
in the intestine of animals and is passed on by the
faecal–oral route and is also a common cause of
waterborne disease. Symptoms include watery,
foul-smelling diarrhoea, flatus and stomach
cramps.
Salmonellosis is a gastrointestinal infection typically from food-borne exposure. Severe recurrent
diarrhoea and bacteraemia may result. Contaminated meat and eggs account for many exposures
but animals can carry salmonella and pass it in their
faeces. Reptiles including both wild and pet lizards,
snakes, frogs and terrapins (turtles) are particularly
likely to pass salmonellosis to people (Chomel,
1992; Mermin et al., 1997; Bren, 2004). Salmonella
infection can also be acquired from farm animals
including horses, baby chicks and ducklings (Bren,
2004).
Toxoplasmosis is caused by single cell parasite—
Toxoplasma gondii. Toxoplasmosis can affect all
mammals, including man, as well as birds, amphibians and other reptiles. Certain species appear to
be more likely to transmit the disease e.g. the
pregnant sheep at the time of birth. Immunocompetent people may carry the toxoplasma parasite
but have few symptoms. However, in pregnant
women and immunocompromised patients toxoplasma infections can cause serious infection
(Guay, 2001; CDC, 2004). The cat is the definitive
host most commonly responsible for disease transmission where the disease is acquired by ingestion
of oocysts shed by infected cats. However, shedding
of cysts is unlikely except when the cat has ill
health such as feline leukaemia; cat AIDS, severe
diarrhoea or other debilitating illnesses (it can also
be a cryptic infection in cats where they shed when
first infected). Isolated outbreaks have also been
reported following handling or inhaling of soil dust
contaminated by cat faeces or contact with cat
faeces from a litter tray or flowerbed. It may also
be transmitted by eating raw vegetables, salad or
fruit contaminated by infected material which has
123
not been washed thoroughly, ingestion of raw or
undercooked meats, especially pork, through contamination of utensils, cutting boards and other
foods which have been in contact with raw meat,
drinking water contaminated with toxoplasma.
Manifestations of the disease include ‘‘flu’’-like
symptoms, swollen lymph glands, muscle aches and
pains. Toxoplasmosis in the immunocompromised
may cause damage to the brain or eyes (Riordan
and Tarlow, 1996; Kravetz and Federman, 2002).
Toxoplasmosis can be transmitted transplacentally if a woman is infected with toxoplasmosis
while she is pregnant. Depending on the age of the
foetus when it is infected and the virulence of
the Toxoplasma, this can result in a spontaneous
abortion, a stillborn child, or a child that is born
with some degree of mental or physical retardation. In those foetuses that survive the lesions
observed are predominantly cerebral, caused by
cerebral vasculitis and necrosis.
Whilst each of these infections, with the possible
exception of Bartonella spp, may be acquired from
sources other than pets, these zoonoses are often
identified as affecting common pets and have the
potential to cause severe and potentially fatal
illnesses.
Other considerations
Allergies
Allergens from the hair, saliva or urine of household
pets can cause an allergic reaction in sensitive
individuals affecting the eyes and the airways, like
hay fever, and can potentiate asthma.
The allergens may also cause atopic dermatitis.
Unfortunately, the only way to avoid pet allergies is
to avoid those animals that provoke them, although
this may be difficult in practice. Allergic reactions
may also occur from other peoples’ pets or from
allergens carried by humans who have been in
contact with animals. Studies suggest that animal
exposure during infancy actually reduces subsequent allergic sensitisation (Ownby et al., 2002).
Parvovirus B19 can cause severe illness in people
with certain blood disorders or immunodeficiency.
However, Parvovirus B19 only infects humans; it is
not the same as the animal parvoviruses. Animal
parvoviruses are not transmissible to humans.
Bites and scratches
Whilst most bites and scratches are not thought to
be life threatening, they can cause pain, anxiety,
ARTICLE IN PRESS
124
wound disfigurement, and wound infections. Many
organisms are capable of infecting animal bite
wounds including Pasteurella spp., Capnocytophaga canimorsus, Bartonella henselae and quintana,
Clostridium tetani, Streptobacillus moniliformis,
Spirillum minus, Tularemia, and rabies. Education
on wound hygiene is therefore important.
Pet vaccines
Administration of live vaccines in immunocompromised and siblings of immunocompromised patients
(except MMR and BCG) should be avoided (RCPCH,
2002). However, with regard to pet vaccines,
none of the live attenuated vaccines used in the
conventional dog and cat vaccines should cause
any problems for immunocompromised human
patients. In addition other vaccines such as those
for leptospirosis, rabies and feline leukaemia are
killed vaccines so are non-transmissible and as such
poses no risk of infecting people (Bennett, 2002).
Survey of existing advice in oncology
centres
In February 2003, a written survey was performed
of all 22 paediatric oncology centres within the UK
to establish if they already had written guidelines
for pet ownership and, if they did, on what
evidence those guidelines were based.
Twenty (91%) surveys were returned. Of these,
only four centres said that they used published or
locally developed guidelines. These guidelines are,
however, limited to brief information in FamilyHeld Record (two centres) or Bone Marrow Transplant (BMT) booklets (two centres). Four additional
centres stated that, although they did not have any
formal guidelines on their unit, they did give out
verbal advice regarding pet ownership. The advice
given did not consider specific zoonoses, age of pet
or animals which may/may not be kept but
concentrated mainly on good hygiene practices
such as washing hands, avoiding contact with
excreta and promotion of vaccination/deworming
programmes. In response to the question of
whether they gave different advice for their BMT
patients, two of the centres without formal guidelines advised that they did have such advice. This
included not obtaining a new pet for 6–12 months
post-transplant (one centre) and avoiding reptiles
and birds (two centres). Two centres gave written
advice about pets in their family held record and
two included such advice as part of their post-BMT
S. Hemsworth, B. Pizer
advice. Most centres admitted that advice was
usually based on ‘‘physician’s preference’’ and such
advice varied depending on Consultants and Units.
All respondents said they would welcome national
guidelines.
Available guidelines
The only written evidence-based guidance was
produced by the Centres for Disease Control and
Prevention (CDC, 1999, 2002).
http://www.cdc.gov/mmwr/preview/mmwrhtml/
rr5108a1.htm The CDC produced guidelines for the
prevention of opportunistic infections in persons
infected with Human Immunodeficiency Virus (HIV)
and opportunistic infections among haematopoietic
stem cell transplant recipients. The CDC is a Federal
Health Agency based in the USA and is part of the
Department of Health and Human Services. Other
American organisations have produced written
advice for people with HIV/AIDS infection (Humane
Society of the United States, 1998; Pets are Wonderful Support, 1998; Pet Owners with HIV/AIDS
Resource Services, 1995) but these also appear to
be based on CDC guidelines or include the same
advice.
Royal Liverpool children’s NHS Trust
guidelines
The 1999 CDC USPHS/IDSA guidelines for the
prevention of opportunistic infections in persons
infected with HIV (Centers for Disease Control
Division of HIV/AIDS prevention, 1999) and CDC
2000 Guidelines for Preventing Opportunistic Infections among haematopoietic stem cell transplant
recipients were the most comprehensive set of
evidence-based guidance we found. We have,
therefore, implemented these at the Royal Liverpool Children’s NHS Trust along with some additional ‘‘local’’ advice. Evidence-based rating
system used to determine strength of recommendations is available on the CDC website.
Pet-related risks
Health-care providers should advise immunocompromised persons of the potential risk posed by pet
ownership. However, they should be sensitive to
the possible psychological benefits of pet ownership and should not routinely advise patients to
part with their existing pets. Specifically, health
ARTICLE IN PRESS
Pet ownership in immunocompromised children
care professionals should advise immunocompromised patients of the following precautions.
Summary of CDC guidelines (reproduced with
kind permission of the CDC).
125
New pets
New pets should be checked by veterinarian
before introducing them to the home as hygienic
and sanitary conditions can vary considerably
between pet stores, animal breeders and animal
shelters.
When obtaining a new pet, immunocompromised
patients should avoid animals aged less than 6
months (or less than 1 year for cats) especially
those with diarrhoea.
Animals aged less than 6 months, especially
those with diarrhoea, should always be examined by a veterinarian for cryptosporidium,
salmonella, and campylobacter.
Immunocompromised patients should avoid stray
animals, reptiles (snakes, lizards, geckos and
terrapins), wild birds and non-human primates
such as monkeys.
When visiting other households with pets, the
same precautions should be taken with those
pets. It is important to let friends/family know
about these precautions.
Pet bedding such as blankets should be cleaned
at least once a week and hutches/cages cleaned
regularly by immunocompetent persons in order
to reduce risk of exposure to faeces.
Pet faeces should be placed in plastic bags and
put in the household rubbish.
Litter trays should be kept away from eating
areas and kitchens and changed daily (bearing in
mind it takes toxoplasmosis 24 h to become
infectious).
An immunocompetent person should change
trays.
Trays should be disinfected at least once a month
by filling with boiling water and leaving to stand
for 5 min, which will kill any toxoplasma organism.
Diet
Pets should not be allowed to hunt or feed from
rubbish bins but maintained on a commercial
diet for their species.
If supplementary food is given, ensure that all
egg, poultry and meat products have been
adequately cooked before feeding.
Pets should be given water that is fit for human
consumption.
Pet health care
Animal-specific advice
Cats
All new pets should be examined by a vet.
Families need to know what vaccinations and
worming/flea control programmes are needed
and these programmes must be kept up to date.
Veterinary care should always be sought whenever
a pet develops diarrhoea or respiratory illness.
Immunocompromised persons should always avoid
contact with animals that have diarrhoea. A
faecal sample should be obtained from animals
with diarrhoea and examined for Cryptosporidium, Salmonella, and Campylobacter.
Hygiene
Pets should be kept cleaned and brushed in order
to keep the skin and coat healthy.
Nails should be clipped short, to minimise risk of
scratches (de-clawing is not recommended).
Patients should wash their hands after handling
pets (especially before eating) and avoid contact
with pets’ faeces to reduce the risk for cryptosporidiosis, salmonellosis, and campylobacteriosis.
Hand washing for immunocompromised children
should always be supervised.
Patients should be aware that cat ownership
increases their risk for toxoplasmosis and Bartonella infection, as well as enteric infections.
Families who choose to obtain a cat should adopt
or purchase an animal that is aged greater than 1
year and in good health to reduce the risk for
cryptosporidiosis, Bartonella infection, salmonellosis, and campylobacteriosis.
To reduce the risk for toxoplasmosis, immunocompromised patients should keep cats indoors,
not allow them to hunt, and not feed them raw
or undercooked meat.
Some of the highly publicised infections shown in
AIDS patients such as toxomplasmosis are due to
reactivation of previous infections acquired from
meat and do not relate to current pet exposures
(Greene, 1995).
Although declawing is not generally advised,
immunocompromised patients should avoid
activities that might result in cat scratches
or bites to reduce the risk for Bartonella
infection.
ARTICLE IN PRESS
126
Patients should wash sites of cat scratches or
bites promptly and should not allow cats to lick
the patients’ open cuts or wounds.
Care of cats should include flea control to reduce
the risk for Bartonella infection.
Testing cats for toxoplasmosis or Bartonella
infection is not recommended.
Birds
Screening healthy birds for Cryptococcus neoformans, Mycobacterium avium, or Histoplasma
capsulatum is not recommended.
Any bird that looks unwell should be checked out
immediately by a veterinary surgeon.
Contact with wild birds and their droppings
should be avoided.
Immunocompetent person should clean the linings of birdcages daily.
Other
Contact with reptiles (e.g., snakes, lizards,
iguanas, and turtles) should be avoided to
reduce the risk for salmonellosis.
Immunocompromised persons should not clean
out aquaria to reduce the risk for infection with
Mycobacterium marinum.
Contact with exotic pets (e.g., non-human
primates) should be avoided.
Additional local advice
S. Hemsworth, B. Pizer
Conclusions
Zoonosis among immunocompromised patients is
an important issue. There is, however, a paucity
of levels 1 and 2 evidence addressing the risks
and clearly further research is required. General
themes have emerged from the available evidence
and certain specific guidance, based on CDC guidelines, has been produced. The majority of pets do
not appear to pose any greater risk to immunocompromised patients than would interaction with
other people or the environment. Misconceptions
about pet-acquired illnesses may cause newly
diagnosed families to get rid of their pets unnecessarily. It may be more detrimental to the well
being of the immunocompromised patient to lose a
beloved pet than to potentially risk acquiring a
zoonotic infection.
Potential risks are made greater by the unique
organisms some animals carry and by poor hygiene
measures. The vectors of many zoonoses are not
necessarily pets but may include humans, farm
animals, exotic and wild animals and whilst there
is no way to completely eliminate exposure or
transmission of zoonotic diseases there are ways to
reduce the possibility of transmission. Educating
pet owners on zoonosis prevention can help them
make more informed decisions about risks and
benefits of owning a pet. However, the overall
benefits of the human–animal bond must be
considered and in general immunocompromised
patients should be able to continue to enjoy the
significant benefits of pet ownership.
Acquisition of new pets
Acknowledgements
Whilst we would not advise families to get rid of
existing pets, we would generally recommend that
new pets are not acquired after diagnosis. If
families do choose to adopt a new pet, an adult
animal is safer.
Families should always consult their Consultant
Oncologist and veterinarian before adopting any
new animal.
The authors would like to acknowledge the expert
help of the following people:
First aid
If bitten or scratched by any animal, the wound or
scratch must be washed straightaway with plenty of
cool running water.
The area should be cleaned with Hibiscrubs
(chlorhexidine glucconate which has both antibacterial/antifungal properties) and dried with clean
dry gauze.
The Oncology Unit should be informed.
Dr Lisa Conti, Director, Division of Environmental
Health, Florida, USA.
Dr Malcolm Bennett, Faculty of Veterinary
Science, University of Liverpool, England.
Dr Ashley Robinson, Associate Dean (Preclinical
Programs), College of Veterinary Medicine, Western University of Health Sciences, California,
USA.
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