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Toxocariasis Disease From Your Pets

By Cerys Erwood

Photo credit: Pixabay

Canids (Dogs, wolves, foxes and coyotes) and felids (cats) can be found on every continent, with Antarctica as an exception. The cause of this wide distribution can be attributed to their use by humans as both domestic and working animals [1]. The relationship between humans and animals has been considered to be mentally and physically beneficial to both parties [2], however the effects of zoonotic disease may cast a shadow over these benefits The CDC (Centre for Disease Control) estimates that 60% of infectious diseases are zoonotic (a disease transmitted from animals to humans), with infamous examples including Rabies, Anthrax and Plague. Despite this, public awareness and understanding of such disease is relatively low [3].

Occurrence of Toxocariasis in the UK is considered to be relatively low and so the disease is generally not considered a priority. However, the apparent rarity of Toxocariasis in the UK may be due to the asymptomatic (without symptoms) manifestation Covert (or Common) Toxocariasis or the fact that cases are often misdiagnosed. Therefore the actual number of Toxocariasis cases in the UK can be assumed to be much higher than previously thought. Therefore, measures must be taken to raise awareness and to prevent transmission of this potentially devastating disease.

The main source of human infection is considered to be soil contamination with infective egg [6,7,8]. Other sources of infection have been considered, but none have yet been shown to be directly proportional to human infection [9]. This may be due to the defecation habits of their hosts and the compulsory soil stage in the parasites’ life cycle. This suggests that environmental contamination must be reduced in order to reduce the risk posed to humans. Currently, there is no way to directly reduce the number of Toxocara spp. eggs in soil – although preliminary studies have suggested the use of specific fungi (Pochonia chlamydiospora and Paecilomyces lilacinus) as bio-controls [10]. Therefore the only route that can be taken is that of reducing infected hosts through de-worming treatments. Regular de-worming of domestic dogs and cats can significantly improve their health while reduce environmental contamination with Toxocara spp. eggs and the risk posed.

However the matter of de-worming is not a simple answer to this problem, it only serves to open another can of parasitic worms. A study performed by Wells [11] showed that only 4.3% of the UK public surveyed were aware of Toxocariasis and its links to dog or cat faeces. Low awareness of zoonotic disease leads to a lack of understanding as to the importance of frequently treating pets for worms and other zoonotic agents. Therefore the only effective way of reducing soil contamination with Toxocara spp. is to raise public awareness through educational programs.


References

  1. Paul, M., King, L. and Carlin, E. P. (2010). Zoonoses of people and their pets: a US perspective on significant pet-associated parasitic diseases. Trends in Parasitology 26:153.
  2. Deplazes, P., van Knapen, F., Schweiger, A. and Overgaauw, P. A. (2011). Role of pet dogs and cats in the transmission of helminthic zoonoses in Europe, with a focus on echinococcosis and toxocarosis. Veterinary Parasitology 182:41-53.
  3. Decker, D. J., Evensen, D. T., Siemer, W. F., Leong, K. M., Riley, S. J., Wild, M. A., ... & Higgins, C. L. (2010). Understanding risk perceptions to enhance communication about human-wildlife interactions and the impacts of zoonotic disease. Ilar Journal, 51(3), 255-261.
  4. Despommier, D. (2003). Toxocariasis: clinical aspects, epidemiology, medical ecology, and molecular aspects. Clinical microbiology reviews 16:265-272
  5. Overgaauw, P. A. and van Knapen, F. (2013). Veterinary and public health aspects of Toxocara spp. Veterinary Parasitology 193:398-403.
  6. Magnaval, J.-F., Glickman, L. T., Dorchies, P. and Morassin, B. (2001). Highlights of human toxocariasis. The Korean Journal of Parasitology 39:1.
  7. Lee, A. C., Schantz, P. M., Kazacos, K. R., Montgomery, S. P. and Bowman, D. D. (2010). Epidemiologic and zoonotic aspects of ascarid infections in dogs and cats. Trends in Parasitology 26:155-161.
  8. Wolfe, A. and Wright, I. (2003). Human toxocariasis and direct contact with dogs. Veterinary Record 152:419-421.
  9. Hoffmeister, B., Glaeser, S., Flick, H., Pornschlegel, S., Suttorp, N. and Bergmann, F. (2007). Cerebral toxocariasis after consumption of raw duck liver. The American journal of tropical medicine and hygiene 76:600-602.
  10. Carvalho, R. O., Araújo, J. V., Braga, F. R., Araujo, J. M., & Alves, C. D. F. (2010). Ovicidal activity of Pochonia chlamydosporia and Paecilomyces lilacinus on Toxocara canis eggs. Veterinary parasitology, 169(1), 123-127.
  11. Wells, D. (2007). Public understanding of toxocariasis. Public Health 121:187-188.

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