It is known and acknowledged that domestic dogs carry parasites, such as Toxocara canis, Uncinaria stenocephala, and Ancylostoma caninum, that are known to be zoonotic. Transmission of disease can also occur through contact with contaminated soil. Until a recent study of 60 dogs from various parts of Ireland and the United Kingdom, the potential for transmission of eggs from dog hair had not been investigated. During a research project on the epidemiology of T. canis, the species of eggs found in samples of dog hair were identified on the basis of visual characteristics. Seven different species of parasitic helminth eggs were recovered-50% of the sampled dogs had these eggs in their hair. The good condition of most eggs suggested that the microclimate within the dog's hair coat is suitable for egg survival. The discovery of embryonated T. canis eggs was a significant find. Three other species that were not parasitic in dogs were found and probably resulted from contamination of the dog hair from other sources. Some eggs and some free-living nematodes were found but could not be identified. Numerous large oocysts and strongyle eggs were also found.
Almost 37% of the sampled dogs had hookworm eggs in their hair. Viable eggs and larvae were observed; these particular larvae feed on detritus and may mature to "infectivity" on a dog's coat. Maturation of hookworm eggs and larvae was previously believed to occur on the ground: U. stenocephala does not infect dogs through the skin, but it may be a route of infection for cutaneous larval migrans in humans, since these particular larvae do migrate through human skin. These parasitic hookworms occur mainly in subtropical climates, the southern United States, and Central and South America. Dogs in these regions may harbor eggs of A. braziliense and/or A. caninum, posing an unrecognized risk for transmitting cutaneous larval migrans to humans.
Dog hair can trap a wide variety and range of materials-from the sticky eggs of T. canis to the smooth, nonsticky eggs of hookworms and trematodes. The hair coat also traps oocysts, and it is possible that other parasites (Toxoplasma gondii in cats and Cryptosporidium and Giardia species) can be passed by direct contact between people and their pets.
COMMENTARY: Zoonotic diseases are probably more common than formerly recognized and appreciated. In today's litigious society, practitioners need to know every route of transmission and potential transmission of zoonotic disease. The fact that parasite ova are commonly found on the coats of our patients gives cause for serious consideration: do we now recommend bathing as an integral part of parasite prophylaxis?
Parasitic nematode eggs in fur samples from dogs. Wolfe A, Wright IP. VET REC 154:208, 2004.