Sciuridae
Sciurus niger
(fox squirrel)



Page Index:

Viral Diseases
Bacterial Diseases
Fungal
Endoparasites
Ectoparasites

Works Cited

<<  Diseases and Parasites   >>

Viral Diseases

Rabies
(Zoonose)

Rabies can exhibit with aggressive behavior and unprovoked attacks (Cappucci et al., 1972).  In a case in 2009, the squirrel was also occasionally lethargic (Hadish, 2009).  However, rabies is extremely rare in tree squirrels.   From 2002 - 2008 American Center for Disease Control (CDC) reports, confirmed cases of rabies in squirrels (not including marmots) national wide made up only 0.002 % of total cases (1 in 49450).  The CDC commented that “[b]ites by [squirrels and other similar animals] are usually not considered a risk of rabies unless the animal was sick or behaving in an unusual manner and rabies is widespread in your area.” (CDC, 2010).

West Nile
(Zoonose)


Fox squirrels were found positive for west Nile virus in Michigan (Kiupel, 2003), Texas, (Camden, 2004) and Illinois (Heinz-Taheny, 2004) in investigations following outbreaks of squirrels with neurological symptoms such as “weakness, depression, head tilt, torticollis, lateral recumbency, uncoordinated movements, inability to right themselves when pushed over, and scratching of their forehead with both feet and tremors” (Kiupel, 2003).  The infected squirrels had showed no other outward physical signs (Kiupel et al, 2003; Heinz-Taheny, 2004).  In an experiment conducted by Root et al., of fourteen experimentally infected fox squirrels, twelve days post infection, all squirrels except one with hind limb paralysis showed no outward signs of disease (2006).

Squirrel Fibromatosis

Squirrel fibromatosis can present in gray squirrels (Sciurus carolinensis) and American red squirrels (Tamisciurus hudsonicus) and perhaps fox squirrels as multiple skin tumors that form all over the body (Bangari, 2009).  Squirrel fibromatosis can be deadly when the tumors become overpowering, weaken resistance to secondary diseases, or restrict vital activity, but infected animals can recover (Terrell, 2002).  Likely squirrel fibromatosis is spread by mosquitoes (Davis, 1970), fleas (Bangari, 2009), and direct contact with lesions.  Cases have been reported in Indiana (Bangari, 2009), New York (Wild Things Sanctuary, 2009), Texas (Girl Squirrel, 2008), Florida (Terrel, 2002),  and Maryland (Kilham, 1953).

Squirrel fibromatosis may be referred to as squirrel pox, but should not be confused with the squirrelpox virus that is killing Eurasian red squirrels (Sciurus vulgaris) in Britain, even though gray squirrels are asymptomatic carriers of the antibodies in Britain and the United States (McInnes, 2006).

California encephalitis
(Zoonose)

Following a case of a human contracting California encephalitis, Moulton and Thompson (1971) tested animals in a woodlot in Wisconsin for antibodies.  Fox squirrels, among other rodents and largomorphs, were found to have antibodies for the disease, which is probably spread by the mosquito Aedes triseriatus.

Western equine encephalitis
(Zoonose)

Western equine encephalitis virus antibodies has been isolated in the fox squirrel in Colorado (Lennette, 1956; Hutson, 1950).

St. Louis encephalitis
(Zoonose)

St. Louis encephalitis antibodies were found in fox squirrels in Colorado, but incidents of infection were small compared to bird populations (Hutson, 1950).


Bacterial Diseases


Tularemia
- Francisella tularensis
(Zoonose)

Tularemia or rabbit fever has a nearly worldwide distribution (Hopla, 1994).  Although rabbits are the most important host (Hopla, 1994), the fox squirrel (Kirkwood, 1931) and gray squirrel (Hopla, 1994) have transmitted tularemia to humans.  The disease can transfer by contact with the animal or tissues, by ticks or other parasites that have fed on the animal, or aerosols (Hopla, 1994).  Gross symptoms of disease in animals such as rabbits or squirrels may be lacking (Hopla, 1994).

Plague - Yersinia pestis
(Zoonose)

Although plague is not common in fox squirrels, in 1968, 81 urban squirrels in Denver, Colorado were found positive for plague (Hudson, 1971).

Weil's Disease - Leptospirosis
(Zoonose)

Leptospirosis (Weil's disease) is a wildlife disease mostly effecting rodents, although humans and other animals can become infected when they come in contact with bodily fluids of an infected animal.  Leptospirosis presents first with flu-like symptoms, and after an asymptomatic period, the disease can lead to organ failure, jaundice, and other complications.  Rodents can be free of signs of the disease, and yet continue to produce infected urine.  Leptospire of serotype grippotyphosa was found in the fox squirrel in southwestern Georgia (Shotts, 1975).


Fungal

Dermatophytosis - Sporothrix schenckii
(Zoonose)

After a bite from an unknown squirrel species (probably gray or fox squirrel), a man developed severe arm legions due to the fungus Sporothrix schenckii (Saravanakumar, 1996).  He recovered after several months of antibacterial and antifungals (Saravanakumar, 1996).




Endoparasites

Bot Fly - Cuterebra emasculator

The squirrel Bot fly (Cuterebra emasculator) is found between the Mississippi river and Atlantic coast, and infection of the fox squirrel has been documented in Mississippi (Jacobson, et. al., 1979), and Florida (Slansky, 2006). Typically the bot fly infests adults, but they also rarely effect nestlings (Slansky & Kenyon, 2002).

The bot fly probably lays eggs near nesting sites of host squirrels, and the animal's body heat causes the eggs to hatch (Jaffe et. al., 2005). Once the squirrel comes in contact with the larva, they enter the body through the eyes, nose, mouth (Jaffe et. al., 2005), or wound (Slansky & Kenyon, 2002), and migrate to a location just under the skin where they begin forming their subcutaneous pockets called warbles (Jaffe et. al., 2005). In the warbles, the larvae feed on cellular debris (Payne & Cosgrove, 1966).  Fox squirrels survive low numbers  of warbles if the position of the warble does not obstruct vital activity.

Raccoon Roundworm - Baylisascaris procyonis
(Zoonose)

Raccoons are the primary host of Baylisascaris procyonis, which in its adult stage, lines the walls of the raccoon's small intestines (Sameul, 2001). The worms shed hundreds of thousand of eggs a day into the raccoon's feces, and can remain infective for years after the raccoons defecate at latrine sites, often near or on trees or logs (Sameul, 2001).

The fox squirrel, among other small prey animals, is an intermediate host of raccoon roundworm.  Once fox squirrels ingest the eggs, the larva hatch in the small intestines, but rather than remain there as they do in the raccoon, the larva migrate throughout the squirrel's body (Sameul, 2001). When the larvae enter the central nervous system, neurological symptoms develop, such as arching of the head, body tilts, circling, and so forth (Sameul, 2001). Coma and death may follow (Sameul, 2001).

Because the worm migrates through the body of intermediate hosts, the moribund or dead host is especially infective for the scavenging raccoon. Raccoon roundworm is present in many raccoon popuations, and infected fox squirrels have been found in Indiana and California (Sameul, 2001).

Acanthocephala Worm - Moniliformis clarki
(Zoonose)

Seven Moniliformis clarki were found in one Sherman Fox Squirrel (Sciuris niger shermani) (n=87) in Florida.  None of the 32 Mangrove Fox Squirrels (Sciurus niger avicennia) were infested (Coyner, 1996).

Tape Worm - Raillietina bakeri

An average of five tape worms of the species Raillietina bakeri were found in 32% of the Sherman Fox Squirrels (Scirus niger shermani) (n=87) in Florida, but none of the 32 Mangrove Fox Squirrels surveyed (Sciurus niger avicennia) were infested (Coyner, 1996).

Parasitic Roundworms -
   Strongyloides robustus, Heligmodendrium hassalli

In Florida, of 87 Sherman fox squirrels (Sciuris niger shermani) and 32 Mangrove fox squirrels (Sciuris niger avecinne) surveyed, the animals had the following nematodes. The chart also indicates prevalence percentage (%), average count (A), and intensity range (I) of the nematodes.

Nematode

S. n. shermani S. n. avicennia

%
A
I
%
A
I
Strongyloides robustus
76
58
1-518
09
07
6-10
Heligmodendrium hassalli
49
21
1-068
09
21
7-64
Citellinema bifurcatum
39
34
1-177
03
33
33
Dipetalonema interstitium
04
02
1-003
00
00
0
Physaloptera massion
03
18
6-043
00
00
0
Syphacia thompsoni
03
04
1-006
00
00
0
Gongylonema pulchrum
02
02
2
00
00
0
Trichostrongylus calcaratus
02
14
1-026
03
01
1
Bohmiella wilsoni
01
03
3
03
03
3

(Coyner, 1996)








Ectoparasites


Fleas - Orchopeas howardii

The squirrel flea (Orchopeas howardii) is associated with the fox squirrel, along with a few other animals.  It has been recorded on the Mangrove fox squirrel (Sciurus niger avicennia) and the Sherman fox squirrel (S. n. shermani) in Florida, the reddish fox squirrel (S. n. rufiventer) in Kansas and Wisconsin, the Texan fox squirrel (S. n. limitis) in Texas, and a fox squirrel in Georgia (Coyner 1996; Poorbaugh 1961; Admin, 1976; Randolph 1946; Morlan 1952). 

Fleas are common in fox squirrel populations.  In a study in Georgia, 60% (n=42) of fox squirrels were infested with an average of ten O. howardii fleas each (Morlan, 1952), and in Florida, 57% (n=54) of the Sherman fox squirrels (S. n. shermani), and 16% (n=32) of the Mangrove fox squirrels (S. n. avicennia) studied had the flea O. howardii (Coyner, 1996).

Other fleas may infest fox squirrels as well.  Of four animals examined in Wisconsin, along with O. howardii, the reddish fox squirrel (S. n. rufiventer) also had one chipmunk flea (Megabothris acerbus) (Admin, 1976).  In Oklahoma, the chicken flea, Echidnophaga gallinacea, was found on the Texan fox squirrel (S. n. limitis) (Ellis, 1955).  In Georgia, a southern fox squirrel (S. n. niger) had a cat flea (Ctenocephalides felis) (Morlan 1952).  The flea  Conorhinopsylla stanfordi was found on the reddish fox squirrel (S. n. rufiventer) in Wisconsin (Admin 1976).

In a study of fox squirrels in Florida, the Sherman fox squirrel (S. n. shermani) had a greater prevalence of fleas than the Mangrove fox squirrel (S. n. avicennia), and although prevalence among males sample was uniform, winter females had a lower rate of infestation than spring females (Coyner, 1996). 

Lice - Neohaematopinus sciurinus, Enderleinellus longiceps, Hoplopleura sciuricola

Several species of blood sucking lice are know to infest the fox squirrel.  Enderleinellus longiceps has been found on the Delmarva fox squirrel (S. n. vulpins) in New Jersey (Race, 1956).  The lice species Hoplopleura sciuricola (7% prevalence) and Neohaematopinus sciurinus (40% prevalence) were found on some of the fourty-two southern fox squirrels (S. n. niger) surveyed in southwest Georgia.  Neohaematopinus sciurinus and hoplopleura sciuricola were found on the Texan fox squirrel (S. n. limitis) in Texas (Randolph, 1946).

Ticks - Amblyomma americanum, Ixodes scapularis

The lone star tick, Amblyomma americanum, and deer tick, Ixodes scapularis, infests the Texan fox squirrel (S. n. limitis) in Texas (Randolph, 1946).  Of the 54 Sherman fox squirrels  (S. n. shermani) in Florida, 7% also had Amblyomma americanum (Coyner, 1996).

Mites - Atricholaelaps sigmodoni, Androlaelaps casalis

The mite Atricholaelaps sigmodoni infects the Texan fox squirrel (S. n. limitis) in Texas (Randolph, 1946).    In a study of fox squirrels in Florida, of 54 Sherman fox squirrels (S. n. shermani), 11% were infected with Androlaelaps casalis, and 3% of 32 Mangrove fox squirrels (S. n. avicennia.)   Of the Sherman fox squirrels (S. n. shermani), 2% had Neotrombicula whartoni, and 2% had Eushoengastia diversa where the Mangrove fox squirrels (S. n. avicennia) had none (Coyner, 1996).

Mange mites can cause squirrel fur loss, sometimes leading to their death, as either a primary cause or because mange weakens the squirrel (Allen, 1943).





Works Cited


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Allen, D. L. (1943). Michigan Fox Squirrel Management. Game Division, Department of Conservation.


Bangari, D. S., Miller, M. A., Stevenson, G. W., Thacker, H. L., Sharma, A., and Mittal, S. K. (2009). Cutaneous and Systemic Poxviral Disease in Red (Tamiasciurus hudsonicus) and Gray (Sciurus carolinensis) Squirrels. Veterinary Pathology 46:667-672.


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