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).
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 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).
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
Western equine encephalitis virus antibodies has been isolated in the fox squirrel in Colorado (Lennette, 1956; Hutson, 1950).
St. Louis encephalitis
St. Louis encephalitis antibodies were found
in fox squirrels in Colorado, but incidents of infection were small
compared to bird populations (Hutson, 1950).
Tularemia - Francisella tularensis
Plague - Yersinia pestis
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
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).
Dermatophytosis - Sporothrix
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).
Bot Fly - Cuterebra emasculator
The squirrel Bot fly (Cuterebra
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).
Raccoon Roundworm - Baylisascaris
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).
Acanthocephala Worm - Moniliformis
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 -
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.
Fleas - Orchopeas howardii
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%
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).
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)
(Randolph, 1946). Of the 54 Sherman fox squirrels (S. n. shermani) in Florida, 7%
had Amblyomma americanum (Coyner, 1996).
Mites - Atricholaelaps sigmodoni,
The mite Atricholaelaps sigmodoni
infects the Texan fox squirrel (S. n.
limitis) in Texas (Randolph, 1946). In a study of
squirrels in Florida, of 54 Sherman fox squirrels (S. n. shermani), 11% were infected
Androlaelaps casalis, and 3% of 32 Mangrove fox squirrels (S. n. avicennia.)
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).
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