﻿Influenza A
Pandemic (H1N1)
2009 Virus Infection
in Domestic Cat
Brett A. Sponseller, Erin Strait, Albert Jergens,
Jessie Trujillo, Karen Harmon, Leo Koster,
Melinda Jenkins-Moore, Mary Killian,
Sabrina Swenson, Holly Bender, Ken Waller,
Kristina Miles, Tracy Pearce, Kyoung-Jin Yoon,
and Peter Nara
Influenza A pandemic (H1N1) 2009 virus continues to
rapidly spread worldwide. In 2009, pandemic (H1N1) 2009
infection in a domestic cat from Iowa was diagnosed by a
novel PCR assay that distinguishes between Eurasian and
North American pandemic (H1N1) 2009 virus matrix genes.
Human-to-cat transmission is presumed.
Influenza viruses are typically host specific; aquatic
birds are considered the primary reservoir. However, in-
terspecies transmission does occur (1­9) and occasionally
leads to novel host-adapted strains. Interspecies transmis-
sion of influenza virus has been a public health concern
because of the possibility that, through reassortment, a
novel strain with zoonotic potential could emerge. The re-
cent infection of dogs with equine influenza virus (H3N8)
(2) and of swine with human influenza virus (H1N2) (4)
are particularly intriguing because the former resulted in
influenza becoming endemic in dogs and the latter resulted
in a documented reassortment event between human and
swine influenza viruses. Such concern has escalated with
the recent emergence of the novel quadruple-reassorted in-
fluenza virus (H1N1) [pandemic (H1N1) 2009] in humans
(10). Although infection and transmission of the virus have
occurred primarily among humans, occasional transmission
from infected persons to susceptible animals (e.g., swine,
turkeys, ferrets) has been documented (11). The likeli-
hood of pandemic (H1N1) 2009 infection of domestic pets
has been considered less likely (www.cdc.gov/h1n1flu/
qa.htm, www.avma.org/public_health/influenza/new_vi-
rus/default.asp, www.usda.gov/wps/portal/?navid=USDA_
H1N1); however, we report a confirmed case of pandemic
(H1N1) 2009 virus infection in a domestic cat that had been
in contact with persons who had recently experienced influ-
enza-like illness.
The Case
A 13-year-old, castrated male, domestic cat that lived
indoors in a single-cat household was brought to the Iowa
State University Lloyd Veterinary Medical Center be-
cause of depression, inappetance, and respiratory signs of
4 days' duration. The cat was gregarious and interacted
closely with family members in the household. The fam-
ily members noted that the cat was reluctant to lie in lat-
eral recumbency and instead rested in sternal recumbency
with neck extended, which was indicative of dyspnea. The
cat's vaccination status was up to date. Before the onset of
clinical signs in the cat, 2 of the 3 family members had ex-
perienced an undiagnosed influenza-like illness--an upper
respiratory tract infection characterized by fever, coughing,
and myalgia--that lasted 3 days. Onset of the cat's clinical
signs was noted 6 and 4 days after onset of illness for the
first and second family members, respectively.
At the time of examination, the cat had bilateral ad-
ventitial lung sounds (wheezes), was afebrile, and was
clinically dehydrated. Radiographs of the thorax showed
a bilateral caudodorsal alveolar pattern (Figure). Cytologic
and microbiologic examination of bronchoalveolar lavage
(BAL) fluid showed foamy macrophages (65%), nonde-
generate neutrophils (25%), and small lymphocytes (10%).
Clinicopathologic findings suggested a moderate, predomi-
nantly macrophagic, mixed inflammatory process. Stan-
dard microbial culture of BAL aliquots yielded no substan-
tial growth of aerobic or anaerobic bacteria. Radiographic
and cytologic findings were inconsistent with bacterial or
parasitic pneumonia and not supportive of allergic airway
disease. A viral cause was considered most likely; how-
ever, the cat was given amoxicillin with clavulanate (125
mg orally 2×/day) to reduce the possibility of secondary
bacterial pneumonia. Notable findings from laboratory test-
ing (complete blood count, serum biochemistry, urinalysis,
and total thyroxine measurement) were moderate leuko-
penia characterized by a moderate lymphopenia, modest
hemoconcentration, and a slightly elevated thyroxine level.
Lymphopenia was consistent with acute viral infection.
PCR testing (Feline URD Panel; Idexx Laboratories,
Westbrook, ME, USA) of a BAL sample showed negative
results for Chlamydophila felis, feline calicivirus, feline
herpesvirus-1, Bordetella bronchiseptica, and Mycoplasma
felis. Results of feline immunodeficiency virus (antibody)
and feline leukopenia virus (antigen) testing (Idexx SNAP
FIV/FeLV Combo Test; Idexx Laboratories) were also
negative, ruling out the potential that viral-induced immu-
nosuppression was a concurrent factor. For the following
reasons we included pandemic (H1N1) 2009 on our list of
DISPATCHES
534 Emerging Infectious Diseases · www.cdc.gov/eid · Vol. 16, No. 3, March 2010
Author affiliations: Iowa State University, Ames, Iowa, USA (B. A.
Sponseller, E. Strait, A. Jergens, J. Trujillo, K. Harmon, H. Bender,
K. Waller, K. Miles, T. Pearce, K.-Y. Yoon, P. Nara); and US De-
partment of Agriculture National Veterinary Services Laboratories,
Ames (L. Koster, M. Jenkins-Moore, M. Killian, S. Swenson)
DOI: 10.3201/eid1603.091737
Pandemic (H1N1) 2009 Virus in Domestic Cat
differential diagnoses: recent history of respiratory disease
in household family members, known widespread com-
munity prevalence of pandemic (H1N1) 2009 influenza
in humans, paucity of common viral infections causing
infectious caudodorsal alveolar pneumonia in adult cats,
and documented susceptibility of felids to avian influenza
(H5N1) (12,13). We therefore submitted a BAL sample to
the Iowa State University Veterinary Diagnostic Labora-
tory for molecular screening and typing for influenza A and
the pandemic (H1N1) 2009 virus.
RNA was obtained from the BAL fluid by using the
MagMAX Viral RNA Isolation Kit (Applied Biosystems,
Austin, TX, USA) and a semiautomated magnetic par-
ticle processor (Kingfisher 96; Thermo Electron Corp.,
Woodstock, GA, USA) according to manufacturer's rec-
ommendations. Molecular testing used a real-time reverse
transcription­PCR (rRT-PCR) influenza A screening as-
say specific for the nucleoprotein gene. Preliminary dif-
ferentiation of pandemic (H1N1) 2009 virus from other
H1 or H3 types of influenza A was performed by using an
in-house rRT-PCR assay that distinguishes between pan-
demic (H1N1) 2009 [Eurasian matrix (10)] and endemic
(to North America) swine H1N1 influenza viruses (North
American matrix). Sequences of primers and probes are
summarized in Table 1. PCRs were conducted by using
the AgPath-ID Multiplex One-Step RT-PCR Kit (Am-
bion/Applied Biosystems) according to manufacturer's
recommendations; 10 units of Multiscribe Reverse Tran-
scriptase (Applied Biosystems) were added per reaction.
Thermocycling was performed by using the Applied Bio-
systems 7500 Fast Real-Time PCR System according to
manufacturer's recommendations.
PCR testing showed the BAL sample to be positive for
influenza A virus (nucleoprotein gene), and the virus was
determined to contain the matrix (M) gene of the pandemic
(H1N1) 2009 virus strain. A BAL sample was submitted to
the US Department of Agriculture National Veterinary Ser-
vices Laboratories (Ames, IA, USA) for confirmatory test-
ing. rRT-PCR confirmed that the BAL sample was positive
for the M gene of influenza A virus and the neuraminidase
(N) gene of pandemic (H1N1) 2009 virus. Sequences of
primers and probes are summarized in Table 2. A cytolytic
virus was isolated by using MDCK cells (8) and was des-
ignated as A/feline/IA/NVSL026991/2009. PCR testing
of the isolate for influenza A virus (M gene) and N1 gene
of pandemic (H1N1) 2009 showed positive results. Se-
quence analyses for hemagglutinin (HA), N, and M genes
confirmed that the virus was pandemic (H1N1) 2009 virus
(GenBank accession nos. GU332630 (for HA), GU332632
(for NA), and GU332631 (for M). Nucleotide homologies
with the first US human pandemic (H1N1) 2009 isolate (A/
CA/04/2009) were 99.4%, 99.4%, and 99.8% for the HA,
NA, and M genes, respectively.
The cat was discharged from the medical center after
diagnostic testing and correction of dehydration. A veteri-
narian (B.A.S.) visited the home to monitor the cat's clini-
cal status and administer subcutaneous fluids (120­160 mL)
until the cat's appetite improved; adventitial lung sounds
resolved within 3 days. Reassessment 1 week later showed
Emerging Infectious Diseases · www.cdc.gov/eid · Vol. 16, No. 3, March 2010 535
Figure. Radiographs of the thorax of a cat with confirmed influenza
A pandemic (H1N1) 2009 virus infection. A) Right lateral view; B)
dorsoventral view.Asymmetric soft tissue opacities are evident in the
right and left caudal lung lobes. An alveolar pattern, composed of air
bronchograms with border-effaced (indistinct) adjacent pulmonary
vessels, is most pronounced in the left caudal lobe. A small gas
lucency in the pleural space appears in the right caudal and dorsal
thoracic cavity. An endotracheal tube is visible at the thoracic inlet
on the lateral view in this moderately obese cat. L, left.
marked improvement of clinical signs but only modest im-
provement of the lymphopenia and radiographic findings.
Conclusions
Because the cat was from a single-animal house-
hold and remained indoors, he was presumably infected
through contact with the family members. Attempts to ret-
rospectively confirm pandemic (H1N1) 2009 infection in
the family members have been unsuccessful, but addition-
al testing of archived biologic samples is being conduct-
ed. Although more surveillance and studies are needed
to determine susceptibility of companion animals to the
pandemic (H1N1) 2009 virus, possible reverse zoonotic
transmission (humans to animals) remains a concern. In-
deed, cases in a domestic dog and other felids have been
confirmed (11) (www.cdc.gov/h1n1flu/qa.htm, www.
avma.org/public_health/influenza/new_virus/default.asp,
www.usda.gov/wps/portal/?navid=USDA_H1N1). Impli-
cations of pandemic (H1N1) 2009 virus infection in com-
panion animals are 1) apparent human-to-animal trans-
mission; 2) broader host range for the virus; 3) potential
endemic establishment of influenza in companion ani-
mals; 4) possible transmission of influenza from compan-
ion animals to other species, including humans; and 5) the
need to reevaluate companion animals as potential reser-
voirs or intermediate hosts for reassortment of influenza
virus. This case emphasizes the need for close monitor-
ing for interspecies transmission of influenza virus and
reinforces the need for collaboration among many disci-
plines, a cornerstone of the One Health Initiative (www.
onehealthinitiative.com).
Acknowledgments
We thank the family members in the cat's household for
their cooperation and Sarah Abate, Wendy Stensland, and Leslie
Bower for technical assistance.
This study was supported by the Iowa State University Of-
fice of the Vice President for Research and Economic Develop-
ment, the Iowa Healthy Livestock Initiative Research Grant, and
the Center for Advanced Host Defenses, Immunobiotics and
Translational Comparative Medicine.
Dr Sponseller is an assistant professor in the Departments
of Veterinary Clinical Sciences and Veterinary Microbiology and
Preventive Medicine, College of Veterinary Medicine, Iowa State
University. His research focuses on viral pathogens of domestic
animals and acquisition of pulmonary immunocompetency.
DISPATCHES
536 Emerging Infectious Diseases · www.cdc.gov/eid · Vol. 16, No. 3, March 2010
Table 1. Oligonucleotide sequences for primers and probes and dye labels used in novel molecular testing for pandemic (H1N1) 2009
virus, Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa, USA, 2009*
Name Sequence (5  3) Description
Influenza A NP screening assay
SIVRTF CGGACGAAAAGGCAACGA NP forward primer
SIVRTR CTGCATTGTCTCCGAAGAAATAAG NP reverse primer
SIVRTP CCGATCGTGCCYTC NP probe, MGB FAM
Pandemic influenza M differentiation assay
M_F TCAGGCCCCCTCAAAGC M forward primer
M_R1 CATTCCATGAGAGCCTCAAGATC M reverse primer 1
M_R1a CACTCCATGAGAGCCTCAAGATC M reverse primer 2
M_R1b CATTCCATGAGTGCCTCAAGATC M reverse primer 3
M_EUPr CAGAGACTGGAAAGTGT EU M MGB, VIC
M_NAPr CAGAGACTYGAAGAYGT NA M MGB, FAM
*Primers and MGB probes were obtained from Integrated DNA Technologies (Coralville, IA, USA) and Applied Biosystems Inc. (Foster City, CA, USA),
respectively. SIV, swine influenza virus; NP, nucleoprotein; M, matrix.
Table 2. Oligonucleotide sequences for primers and probes and dye labels used in confirmatory molecular testing for pandemic
(H1N1) 2009 virus, National Veterinary Services Laboratories, Ames, Iowa, USA, 2009*
Name Sequence (5  3) Description
Influenza A M screening assay
M+25 AGATGAGTCTTCTAACCGAGGTCG AI M forward primer
M-124 TGCAAAAACATCTTCAAGTCTCTG AI M reverse primer
M-124siv TGCAAAGACACTTTCCAGTCTCTG H1N1 M reverse primer
M+64 TCAGGCCCCCTCAAAGCCGA M probe, BHQ, FAM
Pandemic influenza N1 differentiation assay
N1 220F CAACACCAACTTTGCTGC N1 forward primer
N1 330R GGAACCGATTCTTACACTGTTGTC N1 reverse primer
N1 232 CAGTCAGTGGTTTCCGTGAAATTAGC N1 BHQ, FAM
*Primers and probes were obtained from Integrated DNA Technologies (Coralville, IA, USA) and Biosearch Technologies, Inc. (Novato, CA, USA),
respectively. M, matrix; AI, avian influenza; N, neuraminidase.
Pandemic (H1N1) 2009 Virus in Domestic Cat
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Address for correspondence: Brett A. Sponseller, 2134 College of
Veterinary Medicine, Iowa State University, 1600 S 16th St, Ames, IA
50011-1248, USA; email: baspon@iastate.edu
Emerging Infectious Diseases · www.cdc.gov/eid · Vol. 16, No. 3, March 2010 537
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