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WSVA7-0541
ZOETIS
PARASITOLOGY IN THE 21ST CENTURY: WHAT’S NEW AND WHAT’S DIFFERENT?
S. Little1
1Regents Professor and Krull-Ewing Chair in Veterinary Parasitology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, Oklahoma, USA
Acari (ticks and mites) have long presented a common and difficult challenge to companion animal veterinarians worldwide. Although effective acaricides have been widely available for several decades, safety concerns and compliance issues have sometimes led to less
than satisfying results even when best practices were followed. Ticks present a particular health concern not only because of infestation risk but also due to their ability to serve as vectors of serious, sometimes fatal, disease agents. Many tick-borne agents also infect people, creating a zoonotic disease threat.
The geographic distribution of ticks worldwide has dramatically expanded in recent decades, resulting in more pets and more people at risk of both infestation and infection. Fortunately, the advent of the isoxazoline class of systemic acaricides, including sarolaner, fluralaner, and afoxolaner, has provided veterinarians with a safe and highly effective strategy to combat ticks, mites, and the diseases that they cause in addition to providing persistent flea control.
Evolving Challenges Presented by Ticks
Ticks have become a more urgent issue for companion animal health in many areas of Europe, North America, and Australia in recent decades. One reason for this
shift is the wide scale geographic expansion of several tick species into new regions. In Europe, the range of Dermacentor reticulatus has rapidly expanded in several areas1,2 and the Ixodes ricinus range has expanded steadily northward, facilitated by host availability and climate change.3,4 Recent surveys in the UK have similarly shown that both Ixodes ricinus and D. reticulatus have increased in abundance and distribution in recent years.5,6 In North America, climate change and habitat conversion are thought to have resulted in expansion in the range of both Amblyomma spp and Ixodes spp.7-9 A recent nationwide survey in Australia of ticks from dogs and cats suggested that the range of Rhipicephalus sanguineus on this continent has expanded southward,10 and new foci of the kangaroo tick have been established in some areas of South Australia.11 As tick populations spread to new areas, the risk of disease transmission increases. Newly introduced ticks harboring tick-borne infections often catch the local community by surprise, resulting in widespread infection and disease even when vaccines and highly effective tick control
products are available. As veterinarians respond and implement control measures, the incidence of disease decreases. Combining vaccination with tick control has been shown to dramatically reduce the risk of canine Lyme disease in endemic areas. Several acaricides, including systemic isoxazolines, have been shown to reduce or block transmission of tick-borne infections in experimental models.
Tick Myths and Misperceptions
One common misunderstanding among pet owners is that ticks can only be acquired from natural areas outdoors. While ticks are very common in both grassy and wooded areas surrounding homes as well as in urban and suburban parks and more natural, wild areas, one species in particular – the brown dog tick, Rhipicephalus sanguineus – thrives inside homes, kennels, and anywhere frequented by dogs. Due
to the unique ability of brown dog ticks to survive long-term in the low humidity indoor environment,
even dogs that spend no time in nature are at risk of acquiring severe, sometimes fatal tick infestations. Left unchecked, populations of brown dog ticks in a home can dramatically increase in number. All three stages feed on dogs (Figure 1) and, when tick numbers are high, anemia and even exsanguination may result.12 Premise infestations with brown dog ticks are extremely difficult
to eradicate, resulting in a long-lived nuisance for owners and pets alike.13
Figure 1. All stages of Rhipicephalus sanguineus prefer to feed on dogs, including the larva (bottom), nymph (top), and both male (left) and female (right) adult ticks. Image provided by the National Center for Veterinary Parasitology, Oklahoma State University.
Another frequent misimpression held by many pet owners is that cats are not at risk of tick infestation by virtue of their assiduous grooming habits. Although less well studied than ticks on dogs, cats are commonly infested with ticks and benefit from tick control. In the largest survey published to date of feral cats in North America, 19% harbored ticks, and ticks were found on
An Urban Experience
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