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Monday, January 20, 2014

Parasites & Disease

par•a•site [ˈparəˌsīt]
an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host's expense.

dis•ease [diˈzēz]
a disorder of structure or function in a human, animal, or plant, especially one that produces specific signs or symptoms or that affects a specific location and is not simply a direct result of physical injury.

Mites (ectoparasitic arachnids)

MItes are tiny eight-legged creatures belonging to the Order Acarina and are related to spiders and ticks. Some mites live freely and others as parasites. Mites can attack plants and animals, carry disease, and cause allergies.Flying squirrels affected by:
Psorergates glaucomys
Euhaemogamasus ambulans
Trembicula micrati
Haemolaelaps megaventralis
Haemogamasus reidi
Androlaelaps fahrenholzi

Lice (ectoparasitic insects)

Lice are wingless, normally flat-bodied insects with short antennae, complex mouthparts and six short legs adapted for clinging to feathers, hair or fur. There are two basic types of lice: chewing lice (skin, feathers, fur) and sucking lice (blood).

Flying squirrels affected by:
Haploplura trispinosa
Nechaematopinus sciuropteri (this is the louse that transmits typhus fever bacterium Rickettsia prowazekii)from southern flying squirrrels to humans)
Enderleineilus replicatus
Microphthirus ucinatus

Fleas (ectoparasitic insects)
Flying squirrels affected by:
Opisodasys pseudarctomys
Epitedia faceta
Orchopeas howardii (this is the flea that transmits typhus fever bacterium Rickettsia prowazekii)from southern flying squirrrels to humans)
Peromyscopsylla catatina
Conorhinopsylla stanfordi
Leptopsylla segnis

Protozoa (endoparasitic, single-celled micro-organisms)
Flying squirrels affected by:
Eimeria parasciurorum
Eimeria dorneyi
Eimeria glaucomydis
Eimeria sciurorumTrypanosoma denysi

Acanthocephala (endoparasitic, bilaterally symmetrical worm-like organisms)
Flying squirrels affected by:
Moroliformis clarki

Nematoda (endoparasitic, (mostly) microscopically small,eelworms, roundworms, threadworms)
Flying squirrels affected by:
Capillaria americana
Citellinema biturcatum
Enterobius sciuri
Syphacia thompsoni
Strongyloides robustus

Cestoda (endoparasitic tapeworms, all of which lack a gut)
Flying squirrels affected by:
Raillietina bakeri


Flying squirrels in North America are considered to be vectors (carriers) of only ONE disease that affects humans, a form of typhus. The Centers for Disease Control in Atlanta, Georgia state that this flying squirrel-specific typhus (Rickettsia prowazekii) is endemic to parts of the eastern United States, but this disease rarely is passed on to humans (since 1976, only 30 cases have been reported, and not all were confirmed to be passed on by flying squirrels).

Typhus synonyms: epidemic typhus, louse-borne typhus fever, typhus exanthematicus, classical typhus fever, European typhus, Brill-Zinsser disease, jail fever

Flying squirrels are NOT associated with rabies, or any other known disease that affects humans. (Message to the Canadian Food Inspection Agency - there has never, ever been a report of a North American flying squirrel ever having contracted monkey pox. Mmmkay?)
This is not to say that flying squirrels can't contract rabies, just that this disease is a very rare occurrence in flying squirrels. The first ever recorded case of rabies involving flying squirrels as the known carrier was in 1961 (Venters H,D, Jennings, W.L., Rabies in a flying squirrel. Public Health Rep. March, 1962;77:200. PMID: 13925340 [PubMed - OldMedLIne for pre-1966). There have been but a few instances since that time, however, there is a much more prevalent transmissable disease that affects southern flying squirrels, namely epidemic typhus.
Epidemic typhus is a potentially severe, but treatable disease once thought to cycle exclusively between humans and body lice. In the mid-1970s, it was discovered that southern flying squirrels were a reservoir for the typhus pathogen,Rickettsia prowazekii.

No other animal is known to be a host species. In the past 25 years, 39 cases of flying squirrel suspected typhus in humans has been reported. Most occur during the winter months in flyer trappers and individuals removing nest debris from attics or nest sites. Individuals involved in inspection of red-cockaded woodpecker nest are at risk as flying squirrels frequently usurp their tree cavities.

Between 1962 and 1975, investigators demonstrated the typhus pathogen in southern flying squirrels captured in Florida and Virginia. In the decade after this discovery. a number of cases of typhus were documented among persons living in eastern and southern USA, all of whom had some type of contact with flyers.

In human transmission, body lice become infected while obtaining a blood meal from an infected individual and subsequently shed organisms in their feces before the lice themselves die of the infection. Humans then become infected by direct contact with the louse feces via a mucous membrane or dermal abrasion (usually from scratching irritated skin), or by inhaling infectious material (feces). The typhus incubation period is usually 12-14 days before early symptoms appear e.g. headache, chills, fever, nausea, and muscle aches. Fever is often higher in the evenings and does not get better with aspirin. Another common sign is a flat, red rash (typically on the trunk of the body and spreading to the limbs). Later signs are photophobia (bright light hurting the eyes), stupor, vomiting and leg pain. Severe complications are meningitis, encephalitis, pneumonia, renal failure, or gangrene of the extremities due to microvascular damage.

Typhus can also establish latency and reappear years or decades later in a recrudescent form called Brill-Zinsser disease. These symptoms are often milder, but not always less severe that the initial infection. Fatalities are rare.

Effective treatment consists of tetracycline therapy. Laboratory testing is the only definitive way to diagnosis typhus.

Flying Squirrel Reservoirs:

The isolation of the typhus organism in flying squirrels was discovered while studies were being done on the ecology of Rocky Mountain Spotted Fever in Virginia and Florida in the 1970s. Most cases of typhus in humans have been reported from states within the range of the southern flying squirrel. Studies on the epizootiology of infection in wild populations of flyers indicate that the organism responsible for typhus exhibits a stable pattern of infection in animal populations rather than massive epidemic cycles. Flyers populations experience seasonal fluctuations in infection intensity with peak s during the winter and spring months. most new infections were noted in pups experiencing their first cold season.

During these months, there is a corresponding peak in the organisms that transmit typhus. Flyers carry the Rickettsia for 2 to 3 weeks before becoming ill. Flyers are hosts to 2 of the principle vectors of typhus ... fleas and lice.

Of the 39 cases of flyer-associated typhus, all but one case in California came from the Southern flyers range and most occurred during the winter. While many individuals were seriously ill and most hospitalized, no deaths occurred.


The mechanism of transmission from flyer to humans remain speculative. It is thought that the transmission is by inhalation or by skin or mucous membrane inoculation of infected infectious louse or flea feces. Histories of close contact with flyers or flyer nesting material in the days prior to illness onset exist in all cases.
These contact generally involve removal of flyers from a home or other building, or cleaning of an infested area.

The risk of infection to wildlife biologists and others exposed to flyers appear to be greatest during the colder months of the year and in handling flyers and nest material. Wildlife biologists engaged in red-cockaded woodpecker reintroduction are also at risk as are persons who maintain captive animals.

Prevention and Avoidance:

An individual may reduce his probability of developing the disease by protective measures (e.g. wearing gloves, eye protection. mask) when engaging in risky activity with flyers.

Typhus can be a severe disease and persons who are unable to take tetracycline because of pregnancy or allergic reactions are recommended to avoid handling flyers and flyer nests, or to rigidly adhere to the use of protective barrier equipment. This is also recommended for immunocompromised or immunosuppressed individuals.

Dr. Mary G. Reynolds et al., Viral and Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.