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Elaeophora schneideri

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Elaeophora schneideri
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Chromadorea
Order: Rhabditida
Family: Onchocercidae
Genus: Elaeophora
Species:
E. schneideri
Binomial name
Elaeophora schneideri
Wehr & Dikmans, 1935

Elaeophora schneideri (arterial worm; carotid worm; cause of elaeophorosis, aka "filarial dermatitis" or "sorehead" in sheep; or "clear-eyed" blindness in elk) is a nematode which infests several mammalian hosts in North America. It is transmitted by horse-flies. Infection in the normal definitive hosts, mule deer or black-tailed deer, seldom produces clinical symptoms. In other hosts, such as sheep, elk, moose, and goats, infection with E. schneideri leads to elaeophorosis. Symptoms of elaeophorosis include necrosis of the muzzle, ears, and optic nerves; lack of coordination (ataxia); facial or lower limb dermatitis; horn deformities; blindness; and death.

Discovery

Symptoms of elaeophorosis were first observed in 1933, in sheep (New Mexico) and mule deer (Utah) infested by an unknown nematode worm.[1] Specimens were first described as Macdonaldius sp. in 1934,[2] and later revised to Elaeophora schneideri Wehr and Dikmans, 1935.[3] A more complete description of adults from elk, sheep and deer was published in 1968.[4]

Description

The female adults are 60–120 mm long and 56-89 µm wide, while males are 55–85 mm long and 40-68 µm wide. The microfilariae are 239-279 µm long and 11-15 µm wide.

Hosts and Life cycle

The normal definitive hosts for E. schneideri are the mule deer and black-tailed deer. It has also been found in several other wild mammalian hosts: white-tailed deer, elk, moose, bighorn sheep, Barbary sheep, domestic sheep. Infestation was also found in sika deer on Texas ranches. Infestations of cattle, horses or humans have not been reported. The vectors of E. schneideri are blood-feeding horse-flies of the family Tabanidae, genera Hybomitra, Tabanus, or Silvius.[5]

Life cycle. In the normal definitive host, E. schneideri microfilariae are found in the host's skin, particularly around the forehead and poll areas. When a horse-fly feeds on an infected host, it ingests some of these microfilariae. Within a few weeks, the microfilariae develop into infective third-stage larvae (called L3) in the fly's fat body tissue and haemocoel. The mature L3 larvae migrate to the head and mouth-parts of the fly. When the fly feeds on another host, the L3 larvae enter the host's blood stream through the bite wound. They are carried throughout the host's circulatory system, and embed themselves in the walls of the leptomeningeal arteries. After a 2-week maturation period, they migrate to the carotid artery. About 4–6 months later they become sexually mature and begin to produce microfilariae. The adults live for 3–4 years. The microfilariae are released into the host's bloodstream, which carries them to the small capillaries of the skin in the head region. They become lodged in these narrow spaces, and await the next feeding horsefly.[6][7]

In abnormal definitive hosts, such as sheep and elk, the adults may remain in the smaller arteries of the head and face region, instead of migrating to the carotid artery. In these smaller arteries, they obstruct blood flow to various parts of the head, face, and brain; which leads to the clinical symptoms of elaeophorosis (see below).

Distribution

In the United States, E. schneideri has been reported from various wild hosts in 19 states: Arizona, Arkansas, California, Colorado, Florida, Georgia, Louisiana, Missouri, Montana, Nebraska, New Mexico, North Dakota (in imported animals), Oklahoma, South Carolina, South Dakota, Texas, Utah, Washington and Wyoming.[8][9][10] It has also been reported from elk and black-tailed deer in Canada.[11]

Species of Elaeophora other than E. schneideri infest various mammals in Europe, Asia and Africa. One survey of Red Deer (Cervus e. elaphus), Fallow deer (Dama dama), as well as domestic sheep, cattle and goats in Czechoslovakia yielded no specimens of E. schneideri.[12]

Prevalence

Field surveys of wild mammal populations have shown wide variation in the percentage of animals infested with E. schneideri. Surveys of all hosts in the southeastern United States generally indicate infection rates in the range of 2-15%.[13] Prevalence rates as high as 50% in mule deer near Durango, Colorado; 78% in black tailed deer herd in Mendocino County, California,[14] 90% in mule deer herds at high elevation sites in Arizona and New Mexico,[15] and 100% (14 of 14 animals) in Texas mule deer[16] have been reported. In areas of high abundance in definitive hosts, the fear of spread to commercial livestock is greatest.

Clinical signs

Symptoms of Elaeophora schneideri infestation vary among the different mammalian hosts.

In the normal definitive hosts, mule deer and black-tailed deer, infestations are asymptomatic.

In the white-tailed deer, infestation is also often asymptomatic. However, blockage and thickening of coronary, cephalic, brachial and femoral arteries and sublingual food impaction have been reported in this host.[17]

In both moose and elk, infestation can lead to fatality. Blockage of the carotid and other arteries of the head and face region by E. schneideri adults restricts local bloodflow, leading to ischemic damage to the brain, optic nerve, ears, muzzle and other facial areas. The results are often blindness; walking in circles or poor coordination (ataxia); dermatitis or gangrene of the ears, muzzle or nostrils; abnormal antler growth; or death.[18][19][20]

In the domestic sheep, Barbary sheep, bighorn sheep, goats, and sika deer, symptoms are typically dermatological, resulting from inflammatory responses to the microfilariae which accumulate under the skin of the face and ears. The resulting lesions have been described by various authors as "dermal encrustations",[21] "tumorous masses",[22] "raw, bloody dermatitis",[23] or "crusty, scabby lesions"[24] of the head and face. Alopecia, blepharitis, and secondary conjunctivitis have also been observed in sheep. Arterial occulsion may also occur in sheep, but to a lesser degree than in moose and elk.[25]

Diagnosis and treatment

Diagnosis involves recovering either adult worms from the arteries after the death of the infested host, or microcercariae from the skin of the face or head. Treatments have been reported for sheep. A combination of tartar emetic (antimony potassium tartrate) and emetine hydrochloride healed the skin lesions.[26] For elimination of the nematodes, fuadin (stibophen), diethylcarbamazine and piperazine hexahydrate have been suggested.[27] However, repeated administration of diethylcarbamazine runs the risk of fatality due to accumulation of dead worms in the arteries.

References

  1. ^ Kemper, H.E. (1938) "Filarial dermatosis of sheep." North American Veterinarian 19(9):38-41.
  2. ^ Dikmans, G. (1934) "New records of helminth parasites." Proceedings of the Helminthological Society of Washington 1:63-64
  3. ^ Wehr, E.E. and G. Dikmans (1935) New nematodes (Filariidae) from North American ruminants. Zoologischer Anzeiger 110(7-8):202-208.
  4. ^ Hibler, C.P. and J.L. Adcock (1968) Redescription of Elaeophora schneideri Wehr and Dikmans, 1935 (Nematoda: Filarioidea). Journal of Parasitology 54(6):1095-1098.
  5. ^ Pence, D.B. (1991) Elaeophorosis in wild ruminants. Bulletin of the Society for Vector Ecology 16(1):149-160.
  6. ^ Hibler, C.P. and C.J. Metzger (1974) Morphology of the larval stages of Elaeophora schneideri in the intermediate and definitive hosts with some observations on their pathogenesis in abnormal definitive hosts. Journal of Wildlife Diseases 10(4):361-369.
  7. ^ "Elaeophorosis". The Merck Veterinary Manual. 2006. Retrieved 2007-07-01.
  8. ^ Couvillion, C.E., W.R. Davidson, and V.F. Nettles (1985) Distribution of Elaeophora schneideri in white-tailed deer in the southeastern United States, 1962-1983. Journal of Wildlife Diseases 21(4):451-453.
  9. ^ Pessier, A.P., V.T. Hamilton, W.J. Foreyt, S. Parish, and T.L. McElwain (1998) Probable elaeophorosis in a moose (Alces alces) from eastern Washington state. Journal of Veterinary Diagnostic Investigation 10(1):82-84.
  10. ^ Jacques, C.N., J.A. Jenks, D.T. Nelson, T.J. Zimmerman, and M.C. Sterner (2004) Elaeophorosis in free-ranging mule deer in South Dakota. Prairie Naturalist 36(4):251-254.
  11. ^ Smits, J.E.G. (1991) A brief review of infectious and parasitic diseases of wapiti, with emphasis on western Canada and the northwestern United States. Canadian Veterinary Journal 32(8):471-479.
  12. ^ Worley, D.E., P. Kolár, J. Corba, K. Chroust, and B. Kotrlá (1985) A preliminary survey for the arterial nematode, Elaeophora schneideri Wehr and Dikmans, 1935, in Czechoslovakia. Folia Parasitologica 32(4):371-372.
  13. ^ Pence, D.B. (1991) Elaeophorosis in wild ruminants. Bulletin of the Society for Vector Ecology 16(1):149-160.
  14. ^ Weinmann, C.J., J.R. Anderson, W.M. Longhurst, and G. Conolly (1973) Filarial worms of Columbian black-tailed deer in California. 1. Observations in the vertebrate host. Journal of Wildlife Diseases 9(3):213-220.
  15. ^ Hibler, C.P., J.L. Adcock, R.W. Davis, and Y.Z. Abdelbaki (1969) Elaeophorosis in deer and elk in the Gila Forest, New Mexico. Bulletin of the Wildlife Disease Association 5(1):27-30.
  16. ^ Pence, D.B. and G.G. Gray (1981) Elaeophorosis in Barbary sheep and mule deer from the Texas Panhandle. Journal of Wildlife Diseases 17(1):49-56.
  17. ^ Couvillion, C.E., V.F. Nettles, C.A. Rawlings, and R.L. Joyner (1986a) Elaeophorosis in white-tailed deer: Pathology of the natural disease and its relation to oral food impactions. Journal of Wildlife Diseases 22(2):214-223.
  18. ^ Madden, D.J., T.R. Spraker, and W.J. Adrian (1991) Elaeophora schneideri in moose (Alces alces) from Colorado. Journal of Wildlife Diseases 27(2):340-341.
  19. ^ Pessier, A.P., V.T. Hamilton, W.J. Foreyt, S. Parish, and T.L. McElwain (1998) Probable elaeophorosis in a moose (Alces alces) from eastern Washington state. Journal of Veterinary Diagnostic Investigation 10(1):82-84.
  20. ^ Adcock, J.L. and C.P. Hibler (1969) Vascular and neuro-ophthalmic pathology of elaeophorosis in elk. Pathologia Veterinaria 6(3):185-213.
  21. ^ Jensen, L. and L. Seghetti (1955) Elaeophorosis in sheep. Journal of the American Veterinary Medical Association 130:220-224.
  22. ^ Robinson, R.M., P. Jones, T.J. Galvin, and G.M. Harwell (1978) Elaeophorosis in sika deer in Texas. Journal of Wildlife Diseases 14(4):137-141.
  23. ^ Thorne, E.T., N. Kingston, W.R. Jolley, and R.C. Bergstrom (1982) Elaeophorosis. In: "Diseases of Wildlife in Wyoming". Wyoming Game and Fish Department: Cheyenne, WY. pp. 214-218.
  24. ^ Boyce, W., A. Fisher, H. Provencio, E. Rominger, J. Thilsted, and M. Ahlm (1999) Elaeophorosis in bighorn sheep in New Mexico. Journal of Wildlife Diseases 35(4):786-789.
  25. ^ Hibler, C.P. and C.J. Metzger (1974) Morphology of the larval stages of Elaeophora schneideri in the intermediate and definitive hosts with some observations on their pathogenesis in abnormal definitive hosts. Journal of Wildlife Diseases 10(4):361-369.
  26. ^ Kemper, H.E. and I.H. Roberts (1946) "Treatment of filarial dermatosis of sheep with antimony compounds." American Journal of Veterinary Research 7(24):350-354.
  27. ^ Kemper, H.E. (1957) Filarial dermatosis of sheep. Journal of the American Veterinary Medical Association 130(5):220-224.
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