Uncinaria stenocephala Railliet, 1884

(Figures 4-11 through 4-12)

ETYMOLOGY:Uncin = hooked + aria referring to the body and steno = narrow + cephala = head

SYNONYMS:Dochmoidesstenocephala, Uncinariapolaris Looss, 1911, Strongylustrigonocephala Gurlt, 1831, Dochmiustrigonocephala Ercolani, 1859, Ankylostomatrigonocephala Linstow, 1885

HISTORY:Uncinariastenocephala was recognized and described as a species of canine hookworm by Railliet in 1884.

GEOGRAPHIC DISTRIBUTION:Uncinariastenocephala is considered to be a parasite that is commonly found in climates that are more temperate or cooler than those where Ancylostoma species are typically found. It is, therefore, confined mainly to the temperate and subarctic climates of the northern and southern hemispheres.

Reports of Uncinariastenocephala in naturally infected cats are rare. Burrows (1968) reported finding Uncinariastenocephala in only 1 of 2,735 cats examined in New Jersey (6% of dogs were infected).

LOCATION IN HOST: The adults of this parasite are found in the small intestine of the feline host.

PARASITE IDENTIFICATION: The adults of Uncinariastenocephala are 3 mm to 12 mm in length. They can be distinguished from the other hookworms found in the cat by the presence of cutting plates within the buccal capsule, as opposed to the teeth that are present in species of Ancylostoma (Fig 4-11). The eggs of this worm can also be differentiated form those of Ancylostoma by their larger sites. The eggs of Uncinariastenocephala are approximately 70 to 90 um long by 40 to 50 um wide, and are especially easy to differentiate form the eggs of Ancylostoma when present in mixed infections (Ehrenford, 1953) (Fig. 4-12).

LIFE CYCLE: Cats are relatively refractory to infection with Uncinariastenocephala (Rohde, 1959, Hurley, 1990). The experimental infection of six cats with larvae cultured from dog feces, produced patent infections in only three of the cats. In these cats athe number of eggs produced were very few, and they were present in the feces only for a very short period of time. In another study in Istanbul, cats were readily infected with larvae cultured from dog feces (Merdivenci, 1966a).

The course of infetion with Uncinariastenocephala has been described in experimentally infected dogs (Gibbs, 1958; Gibbs, 1961; Mihatsch, 1984). When larvae are administered to dogs orally, the larvae undergo a limited somatic migration where they enter the crypts of the gastric glands in the pyloric region of the stomach and the glands of the duodenal mucosa for the first two days after infection. The larvae then reenter the intestinal tract, and as the worms develop, they move in a caudal direction within the intestine. At maturity in the dog, the worms are found in the third quater of the small intestine. The prepatent period can range from 13 to 21 days. Application of larvae to the skin results in lower infection rates. After larvae are applied to the skin, the larvae migrate to the lungs before reentering the gastrointestinal tract through the trachea and esophagus. The prepatent period following percutaneous infection is 15 to 17 days.

Transplacental and transmammary transmission apparently does not occur with Uncinariastenocephala (Mihatsch, 1984). The infection of two bitches, each with 20,000 larvae at the time of conception failed to induce infection in the puppies produced by the pregnancies. The infection of four bitches with 20,000 larvae at the time of whelping also failed to produce infection in the nursing pups. The necropsies of these bitches 28 days fafter infection revealed adult Uncinariastenocephala in the intestines, but no larvae were found in the organs of the body.

It has been reported that adults of Uncinariastenocephala live in the dog for four months (Kalkofen, 1987). A source dog used for experimental infeections at Cornell University was infected for approximately one year. Other investigators have reported that patent infections will persist for about 6 months (Dow et al., 1961). The number of eggs produce by a single female per day has been calculated to by 3,000 to 5,000 eggs per female per day (Rep and Bos, 1979) and 16,000 to 19,000 per female per day (Merdivenci, 1966b).

The larvae of Uncinariastneocephala have been shown to persist within the musculature of orally or percutaneously infected mice (Feilke, 1985). Again, as with the dog, more larvae were recovered following oral infection than following percutaneous infection. It was also shown that very low numbers of larvae could be transmitted from the mothers to the mouse pups if the mothers were percutaneously infected on the day of parturititon.

CLINICAL PRESENTATION AND PATHOGENESIS: Because of the rarity of infections in cats, the description of clinical sings and studies on the pathogenic effects of infection have all been described in dogs.


In dogs, it would appear the Uncinariastenocephala is probably the least pathogenic of the hookworm infections. Blood loss caused by Uncinariastenocephala adults within the intestine has been calculated to be 0.3 ul per worm per day (Miller, 1971). This is only7 about 1% to 2% of the amount of blood lost due to the presence of a single Ancylostoma caninum in a dog. In beagle puppoies, the oral inoculation of 1,000 larvae caused no signs of disease (Merdivenci, 1966). The oral inoculation of infective larvae has, however, been reported to induce severe diarrhea and a 10% reduction in plasma protein levels (Miller, 1971). Infections of greyhounds or beagles with 87 to 1,850 adults caused protein-losing enteropathy and suboptimum growth (Walker and Jacobs, 1985). The oral inoculation of adult beagle bitches at the time of conception or whelping with 20,000 larvae caused only slight diarrhea that was on occasion accompanied with bloody mucous and a slight peripheral blood eosinophilia two weeks postinfection. Examination of the tissues of animals within a few days after infection have indicated that there are minimal lesions associated with the larvae that are found in the glands of the stomach and duodenum the first couple days after infection and that the appearance of the fourth-stage larvae in the ileum is marked by the appearance of petechial mucosal hemorrhages (Gibbs, 1958). There is marked inflammation around larvae that penetrate the skin, and the larvae within the lungs are found in focal areas of inflammation (Gibbs, 1958).

TREATMENT:Uncinariastenocephala appears more refractory to treatment with certain compounds than the canine hookworm, Ancylsotomacaninum. Treatment of dogs with ivermectin at a dose of 6 µg/kg was 27% to 51% and 57% to 90% effective against the adults of Uncinariastenocephala and Ancylostomacaninum, respectively (Egerton et al., 1985). Similarly, milbemycin oxime at a dose of 0.5 mg/kg body weight was found to be 100% efficacious in the case of adult Ancylostomnacaninum, but without effect on populations of adult Uncinariastenocephala (Bowman et al., 1991).

Attempts have been made to prevent infections of dogs with Uncinariastenocephla by vaccination with larvae (Dow et al., 1959 and 1961). Dogs that had received infections with normal larvae were found to be refractive to challenge infection when they were challenged 200 days after having being given the primary infection. Dogs receiving larvae irradiated with 40 Krads of gamma irradiation developed patent infections after being inoculated with the irradiated larvae, but with infections produceing much lower egg counts than dogs inoculated with normal larvae. When these dogs that had been vaccianted with irradiated larvae were challenged with normal larvae, there was a marked reduction in the number of adults that developed in these animals compared to unvaccinated controls.

EPIZOOTIOLOGY: For Uncinariastenocephala, a parasite of cooler climates, cooler temperatures preoved the optimum environment for larval development. The ideal temperature for larval development is 68 F (20 C) (Gibbs and Gibbs, 1958). The maintenance of a fecal culutre containing eggs of both Ancylostomacaninum and Uncinariastenocephala at 59 F (15 C) will only produce the larvae of Uncinariastenocephala after eight days of incubation (Hill and Roberson, 1985). The eggs and larvae of Uncinaria can also survive tempereatures of 32 F (0 C) for days to a week, while those of Ancylsotomacaninum die within a few days (Balasingam, 1964).

On the grass exercise paddocks at two large greyhound kennels in England, most of the infective-stage larvae of Uncinariastenocephala were found on the herbage of the paddock in late fall, with substantial numbers vbeing found on the herbage throughout the winter, with a few being present in early spring (Jacobs, 1978). Also,a it has been observed that dogs infected with Uncinariastenocephala that have been kept in substandard housing conditions have developed cutaneous pedal lesions similar to those seen in cases of ground itch in people infected with the human hookworms, Ancylsotoma duodenale and Necator americanus (Smith and Elliiot, 1969)

HAZARD TO OTHER ANIMALS: If a cat were infected with Uncinariastenocephala, it could serve as a source of infection for other animals in the establishment. However, because of the rarity of this infection in cats, it is more likely that cats will be the recipient of an infection from some other infected animal.

HAZARD TO HUMANS: Adult Uncinariastenocephala have not been found in humans. The larvae of this parasite have been shown to cause cutaneous larvae migrans on rare occasions. Fulleborn (1927) showed using his own skin that these larvae were capable of causing cutaneous larva migrans in humans.

CONTROL/PREVENTION: Cats should be protected from sharing space with dogs infected with this parasite.


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Figure 4-11. Uncinaria and Ancylostoma. These are the eggs of these two species of hookworms from the same fecal sample. The larger egg is the egg of Uncinaria.

Figure 4-12. Uncinaria stenocephala. Anterior end of adult worm showing the cutting plates within the buccal capsule.