Hookworms

(Ancylostoma spp., Uncinaria stenocephala)

Hookworms are nematodes that infect domestic and wild canids and felids. Dogs become infected with ensheathed third stage larvae via the percutaneous (skin), oral or trans-mammary routes (Ancylostoma caninum only). They are zoonotic.

Parasite: Ancylostoma caninum, Ancylostoma ceylanicum,  Ancylostoma braziliense, and Uncinaria stenocephala
Common name: Hookworm
Host: Dogs, cats, wild canids and felids, humans
Pre-patent period: 2 to 4 weeks depending on site of infection
Location of adults: Small intestine
Distribution: Worldwide
Transmission route: Ingestion of third stage larva (all), percutaneous (all) and via trans-mammary route (A. caninum only)
Zoonotic: Yes

Distribution

A.caninum is found in wet and dry regions of the tropics and subtropics. A. ceylanicum is found in the wet tropics and subtropics of Southeast Asia, China, India, and Oceania. A. braziliense is found in the wet tropics of Central and South America, Malaysia, Indonesia, and northern Australia. Uncinaria stenocephala is usually found in temperate, cooler climates in sub-tropical regions.

Clinical signs

In puppies (as young as 10 days old for A. caninum), diarrhoea, often bloody, anaemia, hypoproteinaemia and death may ensue. In older dogs, non-regenerative iron deficiency anaemia may result

Diagnosis

Detection of strongyle eggs (Fig 1) on standard faecal flotation (SOP 1) using saturated salt or sodium nitrate solution (S.G. 1.20). Immature worms may still produce clinical disease (i.e. no eggs observed in faeces). In this case, treatment and examination of expulsed worms is recommended (Figs 2a & b)

Figure 1. Hookworm egg on faecal floatation. (Image credit: Dr Rebecca Traub.)
Figure 2a. Buccal capsule of Ancylostoma caninum containing three pairs of teeth. (Image credit: The University of Melbourne parasite image library.)
Figure 2b. Buccal capsule of Ancylostoma ceylanicum or Ancylostoma braziliense, containing a single pair of teeth. (Image credit: The University of Melbourne parasite image library.)

Treatment

For anthelmintic treatment options refer to Table 1.

Anthelmintic therapy should be combined with supportive care (e.g. fluid and electrolyte therapy, blood transfusion, iron supplementation, high protein diet), where necessary.

Table 1 Routes of application, dose and efficacies of commonly utilised anthelmintics against the primary gastrointestinal parasites of dogs. (Click to magnify)

Control

Puppies should be treated with a registered anthelmintic labelled for use in puppies at 2 weeks of age (to prevent vertically acquired infections becoming patent) and then every 2 weeks until 8 weeks of age. Treat the dam at the same time. Following this, dogs should be dewormed fortnightly or monthly with moxidectin (2.5 mg/kg topically). Refer to Table 1 for details.

Puppies should be tested for parasites (SOP 1) during routine consultations (e.g. vaccinations) and at least every 3 months thereafter to monitor the efficacy of the parasite control regime and owner compliance.

For further control options, refer to General Considerations and Recommendations.

N.B. Off-label use of anthelmintics that significantly reduce the burden of trans-mammary transmission of A. caninum from dam to pups has been described in published literature. These include:

  • a spot-on formulation of imidacloprid 10% plus moxidectin 2.5% topical solution at day 56 of gestation [1].
  • fenbendazole 50mg/kg daily, from day 40 of gestation to 14 days post-whelping [2].
  • ivermectin intramuscular (300 µg/kg) on days 45 and 55 post conception [3].

Public health considerations

All animal hookworms are zoonotic and may cause cutaneous larva migrans in people. Penetration of the ensheathed larvae produce a mild, self-limiting pruritic rash called ‘ground itch’. A. braziliense may produce ‘creeping eruptions’, highly pruritic mobile linear or serpent-like dermal lesions. In Asia and Oceania, dogs act as reservoirs for A. ceylanicum, which produces patent (egg-positive) symptomatic hookworm disease in humans. Non-patent immature A. caninum worms may cause eosinophilic enteritis in humans. Most infections appear asymptomatic.

References

[1]  Kramer F, Hammerstein R, Stoye M, Epe C. Investigations into the prevention of prenatal and lactogenic Toxocara canis infections in puppies by application of moxidectin to the pregnant dog, J. Vet Med. B Infect. Dis Vet Public Health. (2006) 53:218-223.

[2]  Burke TM, Roberson EL, Fenbendazole treatment of pregnant bitches to reduce prenatal and lactogenic infections of Toxocara canis and Ancylostoma caninum in pups, J Am Vet Med Assoc. (1983) 183:987-990.

[3]  Stoye M, Meyer O, Schnieder T, The Effect of Ivermectin on Reactivated Somatic Larva of Ancylostoma caninum Ercolani 1859 (Ancylostomidae) in the Pregnant Dog, Zentralbl Veterinarmed. (1989) 36:271-278.