Strongyloides tumefaciens

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Strongyloides tumefaciens Price and Dikmans 1941

(Figures 4-05 through 4-08)

ETYMOLOGY:Strongyl = round and oides = like for the genus and tumefaciens to reflect the tumor-like nodules induced by the parasite.


HISTORY: Price and Dikmans first reported lesions caused by this parasite in 1929 from a cat from Louisiana. They provided a description of the lesions and worms from the original cat and an additional case from Florida in 1941 and named the parasite Strongyloides tumefaciens.

GEOGRAPHIC DISTRIBUTION: Strongyloides tumefaciens has been found in a small number of domestic cats from the Southeastern United States in Louisiana, Florida, Texas, and Georgia (Price and Dikmans, 1941; Malone et al., 1977; Lindsay et al., 1987). It also has been observed in 2 wild cats, Felis chaus, in India (Dubey and Pande, 1964). A Strongyloides sp., most likely S. tumefaciens, has been observed in 3 Florida bobcats, Felis rufus, and a Florida panther, Felis concolor coryi, (Forrester, 1992).

LOCATION IN HOST: Adult Strongyloides tumefaciens, eggs, and larvae are found in grossly visible tumor-like nodules in the large intestine. Migrating larvae may be observed in various tissues during migration to the large intestine.

IDENTIFICATION: Parthenogenic females os Strongyloidestumefaciens dissected from formalin fixed nodules are about 5 mm long (Price and Dikmans, 1941); the species of Strongyloides present in the small intestine of the cat tend to be around 3.5 mm or less in length. Eggs from females of Strongyloidestumefaciens are embryonated and measure 114 to 124 by 62 to 68 µm. Fecal cultures of larvae at room temperature will result in third-stage larvae that have a “split tail” appearance (typical for Strongyloides sp.) and a filariform esophagus (Malone et al., 1977).

LIFE CYCLE: The life cycle is unknown. Infections are probably acquired by oral ingestion or skin penetration by third stage larvae. Parthenogenic females are found in grossly visible tumor-like nodules in the large intestine. Eggs and larvae are also present in the nodules. Eggs hatch in the nodules and larvae are excreted in the feces. No parasitic males exist.

CLINICAL PRESENTATION AND PATHOGENESIS: Abdominal palpation of cats with S. tumefaciens may reveal a firm and fibrotic colon (Malone et al., 1997). Strongyloides tumefaciens produces characteristic tumor-like nodules in the large intestine. Grossly, white, glistening nodules present on the mucosal surface are elevated 1 to 3 mm above the mucosa and are 2 to 3 mm in diameter (Fig 4-05). These nodules may be visualized on colonoscopy. A central depression may also be present. Microscopically, hyperplastic nodules of crypt epithelium are present in the submucosa (Fig 4-06). A connective tissue capsule surrounds the nodules. The mucosal epithelium covering the nodules may be degenerative and infiltrated by neutrophils and lymphocytes. Parthenogenic females are present and confined to the nodules (Fig 4-07). Eggs can be observed within the females and free in the nodules (Fig 4-08). Rhabditiform larvae can be found in the nodules, in adjacent submucosal tissues and free in the lumen.

TREATMENT: Thiabendazole is effective in treating cats with S. tumefaciens when administered orally at 125 mg daily for 3 days (Malone et al., 1977). The feces become normal and larvae are eliminated by day 4 post-treatment.


HAZARD TO OTHER ANIMALS: Unknown. A similar lesion containing Strongyloides was observed in the jejunum of a chimpanzee (Blacklock and Adler, 1922).


Blacklock B, Adler S. 1922. The pathological effects produced by Strongyloides in a chimpanzee. Ann. Trop. Med. Parasitol. 16: 383-290.

Dubey JP, Pande BP. 1964. On helminthic lesions encountered in the alimentary canal of the Indian wild cat (Felis chaus). Agra Univ. J. Res. Sci. 13:169-184.

Forrester DJ. 1992. Parasites and Diseases of Wild Mammals in Florida. University of Florida Press, Gainesville, Fla. pp.174-203.

Lindsay DS, Blagburn BL, Stuart BP, Gosser HS. . 1987. Strongyloides tumefaciens infection in a cat. Compan. Anim. Pract. 1:12-13.

Malone J. B., A. B. Butterfield, J. C. Williams, B. P. Stuart, and H. Travasos. 1977. Strongloides tumefaciens in cats. J. Am. Vet. Med. Assoc. 171:278-280.

Price EW, Dikmans G. 1929. Multiple adenomata of the large intestine of a cat caused by a species of Strongyloides. J. Parasitol 16: 104.

Price EW, Dikmans G. 1941. Adenomatous tumors in the large intestine of a cats caused by Strongloides tumefaciens, n. sp. Proc. Helminthol. Soc. Wash 8:41-44.


Figure 4-05. Strongyloides tumefasciens. Transverse section through a nodule in the colon of a cat showing the hyperplatic mucosa and muscularis containing numerous worms.

Figure 4-06. Stongyloides tumefasciens. Transverse section showing several sections through the parthenogentic female.

Figure 4-07. Strongyloides tumefasciens. Section through a female worm at the level of the ovary.

Figure 4-08. Strongyloides tumefasciens. Section through the worm at the level of the uterus. Also present are laid eggs in various states of development.

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