J. Jill Heatley DVM MS DABVP (Avian), DACZM
Associate Professor, Zoological Medicine
College of Veterinary Medicine & Biomedical Sciences
Texas A&M University, College Station

Gray...
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Tassel-eared...Sciurus aberti
Fox
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
Eastern Fox....Sciurus niger
Apache Fox.....Sciurus apache
Tamiascirus



Western - Sciurus griseus
Eastern – Sciuris carolinensis
Arizona ...Sciurus arizonensis
American Red.....Tamiasciurus hudsonicus
Chickaree......Tamiasciurus douglasi
Flying Squirrels –


Northern
Southern and Glaucomys volans

Order Rodentia


Family Sciuridae
All continents

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Except Antarctica, Australia
50 genera, 273 species
Subfamily

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Cyonomys – Prairie Dogs
Spermophilus – Ground squirrels
Marmota – Marmots
Ammospermophilus – Antelope Squirrels
Tamias – Chipmunks
Tamiasciurus – Chickarees
Sciurus – Tree Squirrels
Glaucomys – New World flying squirrels
 Expanding urban
communities
 Parks, neighborhoods

Bird feeders
 Nature
Vacation
 Exotic Pets
 Research
 Rehabilitation
 Hunting
Bacterial
 Fungal
 Parasitic
 Viral
 Prion


Literature review

Toxoplasma gondii


Cryptosporidium parvum

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


Intermediate not
definitive host
Eastern gray squirrel
Chipmunk
Red squirrel
California Gray squirrel
Hymenolepis nana


Dwarf tapeworm of hamsters
Human enteric disease


Praziquantel
Mange in squirrels is
generally notoedric or
demodectic and not
transmissable to
humans
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Lyme Disease
Epidemic Typhus
Tularemia
Plague
Leptospirosis
Rat Bite fever
 Squirrel Bite fever
Streptobaccillus
moniliformis
 Spirillum minus

Campylobacter spp.

Salmonellosis

Pasteurella multocida


Yersinia pseudotuberculosis



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Red legged ground
squirrel
Xerus erythropus
Nigeria
Zoonoses

Red squirrel
White tailed antelope squirrel
 Citellus lecurus
Yersinia enterocolitica

Grey squirrel
Squirrel Disease
Tularemia

Isolated in 1912

Plague like disease of rodents
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Bacterium tularense
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
Plague foci search
Francisella tularensis
Tulare county of origin, CA
Ground squirrels Spermophilus beecheyii
Zoonoses

Sciurus carolinensis


Prairie Dog (BT Cyonomys ludovicianus)



Infant Bite Arkansas
Titer positive
3 y with bite
Fox Squirrel

Skinned/dressed
Magee JS et al. Tularemia trans by Squirrel Bite. Pediatric Infect Dis J.1989Feb8(2):123-5.
Avashia SB at al Emerging Infec Dis 10(3) March 2004
Kirkwood T. Tularemia from the Fox Squirrel JAMA 1931; 96(12);941-942
Leptospirosis
 Multiple species

Isolations - serovars
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Gray squirrel - ballum
Fox squirrel - grippotyphosa
 Zoonosis
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Leptospira kirschneri
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Southern Flying squirrel
 Glaucomys volans
Exported to Japan
 28 29 yo males
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Borrelia burgdorferi sensu latu

Spirochetal bacteria
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Debilitating chronic infection
Tick intermediate
Reservoirs
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Western Gray squirrel
Eastern chipmunk
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Most common tick borne disease
Tamias straitus – eastern & upper midwestern US
Persistent infection, no clinical signs
Ixodes scapularis
European reservoir potential
Gray squirrel Sciurus carolinensis
 European tree squirrel – S. vulgaris


Bacterium


Rickettsia prowazekii
Clinical Signs
Fever, Headache, Muscle
pain
 Rash – trunk spreads to
extremities
 Doesn’t involve the palms or
soles (cf RMSF)
 Mort ~ 40% if untreated


Primary Vector

Human Body Louse

Sporadic cases in Eastern US since 1970s
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
Flying squirrels
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Most cases in winter when squirrels nest in
attics
All non fatal, humans faster recovery with
antibiotics
Glaucomys volans
Handled, squirrels nests, pets in home
Capable reservoirs


Transient inapparent infection
Squirrel human transmission unknown
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Sucking lice (Neohematopinus
sciuropteri)
Fleas transmit to squirrels in lab
Direct contact, inhalation of dried
squirrel excretions
bites of squirrel ectoparasites
 Sucking lice
 Flea


Bacterium - Yersinia pestis
Complex flea rodent cycle


Sylvatic reservoir
Human clinical signs
Severe disease
 Fatality rate > 50% if untreated
 Rare - Dozen cases / year


Semiarid West
New Mexico
 Arizona
 Colorado
 California
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Periodic plague outbreaks
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
More susceptible rodent hosts
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Prairie dogs
 Known reservoir
Ground squirrels
Fox squirrels
Human exposure occurs during
outbreaks
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
Flea vector (Flea control!!!)
CS: nonspecific: lethargy, depression, respiratory
distress, lymphadenopathy, anorexia
Serologic testing
Flea bites
Direct contact w nonrodent hosts
Trend of eastward expansion

Epizootic fox squirrels central Texas
 Dermatophytosis
 Sporotrichosis

Sporothrix schenckii



Unknown Sciurid, not captured
Bite 1.5 months earlier in the park
Severe arm lesion responded to 3 months of
antibiotic and antifungal therapy
Lymphocutaneous Sporotrichosis Associated with a Squirrel Bite: Case Report and Review
PS Saravanakumar, P Eslami FA Zar Clinical Infectious Diseases, 23(3)3 Sep 1996) 647-648.
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Dermatomycoses, Tinea,
“Ringworm”
May accompany parapox
fibromas
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Circular shape, scaly raised
border
Patchy hair loss
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Systemic Phycomycosis
Neck , head ,armpits,
abdomen
Skin reddening, thin layer
serous exudate, crusts, skin
nodules
Hair broken off at skin
surface,
Fine stubble broken hair
Lesions
Lewis et
al. JWD
Oct 1975
Urban
Gray
squirrel
mycology
Etiologies

Trichophyton mentagrophytes

Mucor

Candida albicans
Microsporum gypseum,
Scopulaiopsis brevicaulis
Microsporum cookei
Systemic Phycomycosis
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Dermatiaceous Fungi –
pigmented Phaeoannellomyces
wernecklii
Damp weather conditions
Prevalence > 50%

Rule out Alopecia
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Sciurus carolinensis
Glaucomys volans
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Dietary, heritable?
Congenital Alopecia
Dermatophytosis
Louse Bite Lesions
Notoedric Mange
Larval Harvest Mite Lesions
Histology
Fungal organisms in superficial
skin, in and around hairs
 History, Lesions
 Direct examination
 Culture
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
Identify specific fungus
Zoonotic
Young animals more
commonly affected
 One researcher developed
lesions after handling squirrels
 Use gloves, wash with soap
after handling

 Lymphocytic Choriomeningitis Virus
 Gray squirrels serologically positive UK 4/19
 Snowshoe
hare virus (SSHV)
 Arboviruses
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West Nile Virus
Western Equine Encephalitis


Lacross Virus
Eastern Equine Encephalitis
 Rabies

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

Gray squirrel
No human cases associated with squirrel bite
Monkeypox Virus
Encephalomyocarditis virus
White et al. Micro Study of Urban Gray squirrel 1975 JAVMA 167


Alphaviruses, Togaviridae
WEE rare disease in people


Lacrosse Virus, EEE (mort 50%), VEE rare serious disease
Mosquito vector
Hosts (Black tailed jack rabbit, White footed mouse?, ?)
 Lacrosse Encephalitis –
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

WEE Viremia –

Gray squirrels (Sciurus carolinensis), California ground
squirrels, San Joachin antelope ground squirrels,
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

Aggressive, bite people, Usu fatal, may survive overwinter
Richardson’s ground squirrels (Spermophilus richardsonii)

contaminated urine, cannibalism

Experimental Infection
 Weak, depressed, ataxic, limb paralysis prior to death
 Some became hyperexcitable
 Brain, brainstem Necrosis & edema
EEE - Gray squirrels


Tree squirrels and chipmunks primary amplifying hosts
Peripheral inoculation: Encephalitis & death
VEE – Significant viremia, > 50% mort


Mexican ground squirrel - Spermophilus mexicanus
Gray squirrel

Bunyaviridae
Variant of the La Crosse virus
 Encephalitis occasional - NY, Eastern Canada


Antibodies
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Experimental infection ground squirrels
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Artic ground squirrels
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Spermophilus lateralis
Yellow-pine chipmunks
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Spermophilus parryii
Golden mantled ground squirrels
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Symptomless viremia
Eutamias amoenus
Red squirrels

Encephalitis virus

Fox squirrel (Sciurus niger)
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Seroconversion late summer early fall
 None in urine, fleas
 Exp: feces and oral cavity
Experimental infection suggests amplifying host
High seroprevalence
Western gray squirrel (S. griseus)
Eastern gray squirrel (S. carolinensis)
3/36 live neurologic tree squirrels viremia

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
similar to WNV-infected birds.
Most squirrels no virus in serum
S. carolinensis

not amplifying hosts
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low viremias, lack of mortality
Low seroprevalence 2%
Useful as sentinels
High seroprevalence
 Tick

1956 epidemic of people and monkeys




borne encephalitis flavivirus complex
Fever,
hypotension hepatomegaly,
hemorrhage/neuro/bronchopneumonia
recovery/late fever
Southern india - 2500 m radius
 Striped

palm squirrels
Funambulus tristriatus


Antibodies
Viremic infective for Ticks

Orthopox virus

Broad primate host range includes humans



Infection via direct contact
Main host African tree squirrels

Tree squirrels
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
Heliosciurus rufobrachium
H. gambianus
Rope Squirrels



Fever rash resembles small pox
 Low mortality high morbidity
Funisciuris anerythrus
F. lemniscatus
Prairie dogs


Poorly competent host
Effective transmitters for veterinary staff
Diseases

Infectious
Monkey Pox
Humans 1-10% mortality
 Contact, respiratory droplets
 CS: fever, cough, conjunctivitis,
lymphadenopathy, nodular rash




No treatment
Strict biosecurity, humane
euthanasia
CDC website

www.cdc.gov/ncidod/monkeypox

Final rule prohibits
 capture, offers to capture,
transport, sale, barter, exchange,
distribution, or release of a listed
animal into the environment.

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
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Prairie dogs (Cynomys sp.)
African Tree squirrels (Heliosciurus
sp.),
Rope squirrels (Funisciurus sp.),
Gambian giant pouched rats
Cricetomys sp.

Encephalomyocarditis Virus

Genus cardiovirus

AKA: Mengovirus
Worldwide/Ubiquitous disease of rodents
 Human: suspected neurologic disease

Now thought to be asymptomatic
Isolated from feces/intestinal contents
 Sciurus spp.



Red squirrels
Wild squirrels (Vizoso et al 1964)
 Where/ how viral persistence between epidemics unclear

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
Acute death due to cardiac necrosis
Important for zoo collection, elephants
Chimpanzee, Orangutan
 Poorly infectious for people
Squirrel brains
 Creutzfeldt-Jakob

“burgoo”



Squirrel brain stew
5 patients 56-78y
Unrelated, Different towns


disease (CJD)
Rural Kentucky
Don’t eat brain unless you want
be a zombie
Summary
 Squirrels are



harbor a plethora of zoonoses
Sentinel
Is it the cute factor?
Thanks for your attention
 Field
Manual of Wildlife Diseases in the
Southeastern United States, 3rd ed

Davidson, WR
 Zoo

& Wild Animal Medicine 5th ed
Sainsbury, Rodent Chapter
 Infectious Diseases of

Wild Mammals
ES Wiliams, IK Barker
 Smithsonian Museum
of Natural History

North American Mammals

http://www.mnh.si.edu/mna/main.cfm
Clostridium botulinum
 Saravanakuma
PS Eslami P Zar FA
 Lymphocutaneous sporotrichosis associated with
a squirrel bite: case report and review.
 Clin Infect Dise 1996 sep 23(3) 647-8
Squirrel Fibroma

AKA Squirrel Pox

Squirrel Pox Virus


Leporipoxvirus


Related to Shope’s Fibroma of rabbits
Range


1953
Range: Maryland, New York, Virginia,
Michigan, North Carolina, Ontario
Host



Gray squirrel
Fox Squirrel
Red squirrel


Significant cause of decline
Experimental infections

Woodchucks, rabbits
Squirrel Fibroma

Lesions

Limited to skin

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Raised flattened nodules
Light colored, little fur
1/16- 1 inch diameter
Single or wide dissemination
Epizootic



Metastasis to the lungs, liver, kidney, and lymph nodes has
been reported.
Secondary infection
Vision obstruction
Lesions on the eyelid
Swelling, discoloration, necrosis of leg or foot
Clinical Signs



Most infections self limiting, spontaneously regress
Debilitation, emaciation, death
Rare epizootics


Morbidity, mortality many squirrels
Florida
www.michigan.gov/dnr
Parasite-mediated competition

Parapoxvirus: Grey
& Red Squirrels
 Mosquito
spread