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Plenty of parasites - too many to choose from?

by
01 November 2016, at 12:00a.m.

Blaise Scott-Morris of Virbac looks at the most recent research and reminds veterinary surgeons not to forget our old familiar friends among the vast array of parasites now confronting us in practice.

WITH A PLETHORA OF PARASITES TO CONSIDER, how do you pick your parasite of importance? Climate change, increased human and pet travel, relaxed entry laws for pets into the UK ... these are some of the many reasons that have been mentioned whilst discussing if, how, and when the parasite and disease profile of the UK will change.

Angiostongylus vasorum (lungworm) was first identified in the UK in 1979 in Cornwall, infecting dogs, red foxes and other carnivores (Jones, 1980). Since then, spread of A. vasorum has been documented within the UK and Europe.

Initially the focus of spread was within the south of the UK; however, more recent studies have identified foci of infection in Northern England and Scotland.

Data from 2005-06 showed a UK prevalence of 7.3% in foxes with large regional variations and no A. vasorum detected in foxes in northern England or Scotland (Morgan, 2008). However, in 2013-14, overall UK prevalence in foxes had risen to 18.3%, with prevalence in all regions significantly higher than the previous survey (Taylor, 2015).

Of particular importance is the appearance of A. vasorum in northern England, where it had not been detected before (Taylor, 2015). Although there can be limitations to prevalence studies, general trends indicate spread and increased awareness.

Ticks in pockets

Historically, ticks in the UK have been predominantly found in pockets such as the south-west and Wales. However, across the UK ticks are becoming more prominent due to warmer winters and wetter summers. 

According to a recent survey, Ixodes ricinus was found to be the most commonly identified tick in the UK, with 89% of ticks found on dogs belonging to this species (The Big Tick Project, 2016). Only 0.17% of the ticks recovered from dogs were identified as Dermacentor reticulatus.

It would seem that despite recently diagnosed cases of babesiosis in Essex, transmitted by D. reticulatus, this tick is still rare in the UK and, although it is always prudent to be vigilant, Ixodes is still the most common genus of tick in the UK.

SAVSNET, based at the University of Liverpool, has not reported any new babesiosis cases since these initial reports. This indicates that the cases were due to locally infected ticks and it is most likely under control (SAVSNET, 2016).

When your clients are travelling abroad with their pets it is necessary to adjust advice and treatment plans with regards to ticks – we don’t want them returning with any unwanted visitors!

In Europe, the brown dog tick, Rhipicephalus sanguineus, is also of importance, especially as it can live indoors and so there is potential for it to survive in our heated homes in the UK. Remember that repellency is the most effective method to decrease disease transmission (Schunack, 2015). 

There are currently no tick treatment or repellency requirements advised by DEFRA under the PETS travel scheme, but owners should be made aware of the risks when travelling and given appropriate medication.

One ectoparasite that we should never forget about is the flea. A resourceful devil that can be the cause of many headaches for both vets and clients, there are some important aspects of the lifecycle that can be used to help tackle and infestation. 

Although it is vital to use an on-animal treatment for cats and dogs, adult fleas only represent about 5% of the whole lifecycle, so it is important to ensure the environment is also treated. Nothing but re can kill the pupal stage but advising owners to vacuum regularly after using an environmental treatment can encourage the pupae to emerge as young adult fleas and speed up resolution of the infestation.

Don’t forget that it is not just the repulsion and bites that owners experience with fleas or the discomfort for their pets: fleas can also transmit disease. They act as the intermediate host for Dipylidium caninum so it is important to treat concurrently for tapeworm when you are treating a flea infestation.

Preventive action

In the long run, as the old saying goes, “prevention is better than cure” so ensure your clients are not only compliant but also administering treatments correctly. Providing environmental protection as a preventive action, such as with Indorex (Virbac) which has action against the developing eggs and larvae for up to 12 months, can be invaluable in preventing flea infestations.

We are all aware of the endoparasites that we need to consider when treating pets in the UK, and it is beyond the scope of this article to discuss the exhaustive list. However, one which is worth highlighting is Echinococcus multilocularis. It’s not a parasite we currently have in the UK but certainly one we want to avoid, due to its zoonotic potential.

Alveolar echinococcosis is considered to be one of the most serious zoonoses in the Northern Hemisphere (Umhang, 2016). E. multilocularis has spread across Europe in recent decades: its lifecycle relies upon predator-prey interactions such as foxes and small rodents (Umhang, 2016).

Data from fox faeces in France show the parasite is expanding its prevalence, identifying a need for surveillance but also continued treatment of dogs before re-entry into the UK (Umhang, 2016).

Despite discussing the risks from Europe and changing parasite and disease patterns in the UK, it is also important not to forget the common parasites we encounter in the UK when deciding upon a treatment regime for your practice. Individuals may have differing requirements depending upon their lifestyle and travel pattern, i.e. are they going to a known tick area or travelling abroad?

By keeping up to date with the current information on parasite and disease prevalence, we can keep our parasite advice as relevant as possible.

References

  • Jones, G. W., Neal, C. and Turner, G. R. (1980) Angiostrongylus vasorum infection in dogs in Cornwall. Veterinary Record 106: 83.
  • Morgan, E. R., Tomlinson, A., Hunter, S., Nichols, T., Roberts, E., Fox, M. T. and Taylor, M. A. (2008) Angiostrongylus vasorum and Eucoleus aerophilus in foxes (Vulpes vulpes) in Great Britain. Veterinary Parasitology 154: 48-57. SAVSNET (2016) https://www. liverpool.ac.uk/savsnet/.com
  • Schunack, E. H. and Fourrie, J. J. (2015) Comparative efficacy of topical applied permethrin/imidacloprid and oral administration of ofoxolaner or uralaner against transmission of Ehrlichia canis by infected Rhipicephalus sanguineus to dogs. Proceedings WAAVP. 
  • Taylor, C. S., Garcia Gato, R., Learmount, J., Aziz, N.A. et al (2015) Increased prevalence and geographic spread of the cardiopulmonary nematode Angiostrongylus vasorum in fox populations in Great Britain.
  • Parasitology 142 (9): 1,190-1,195. The Big Tick Project (2016) MSD Animal Health: www.bigtickproject.co.uk.
  • Umhang, G., Comte, S., Hormaz, V., Boucher, J.M., Raton, V. et al (2016) Retrospective analyses of fox faeces by real time PCR to identify new endemic areas of Echinococcus multilocularis in France. Parasitology Research August.