Ian is a practicing vet and also has a master’s degree in veterinary parasitology. He is head of the European Scientific Counsel of Companion Animal Parasites (ESCCAP) UK and Ireland and is guideline director for ESCCAP Europe. The ESCCAP website is an invaluable resource for practicing vets.
In this veterinary webinar he brings us up to date on ticks and tick transmitted diseases.
The first slide reminds us of UK tick-borne pathogens. Ixodes spp transmit Borrelia spp, Babesia spp and tick borne encephalitis virus (TBEV). Dermacentor spp transmits Babesia canis
Ixodes are hard inornate (lack coloured enamel -like areas on the body) and in a feature graphically illustrated in the next slide, the nymphs and larvae are very small -2-3 mm. A larva is compared with a 5p piece, demonstrating how easy it is to miss them, whereas females when engorged are very visible. Ixodid ticks are vectors of Lyme disease and tick-borne encephalitis. There is considerable awareness of Lyme disease in the general public, with some well-known celebrities describing their experience. Borrelia burgdorferi has a zoonotic risk, but not directly, although dogs are useful sentinels for infection. Transmission from an attached tick is thought to take at least 16-24 hours. The human incidence of disease has been increasing from 0.38 cases per 100,000 in 2000 to 2.7 cases per 100,000 in 2017. Many think the incidence could be three times higher. Hot spots of the disease occur, Thetford Forest and New Forest for example, although a map shows the ticks to be widespread elsewhere in the UK.
The incidence of human cases is rising, but data for dogs is lacking. This may change soon as EU wide reporting data is about to be published (including the UK?) Recent data suggests 2.37% of ticks found on dogs and 1.8% on cats are carriers of Borrelia. According to UK seroprevalence data there has been no evidence of infection in cats over a 25-year period, backed up by a consensus statement from the ACVIM that Lyme disease has never been definitively diagnosed in a cat.
The principal clinical signs in humans and dogs are listed, including the classical ‘bulls eye’ lesion in people. This appears to be a rare/non-existent sign in dogs and therefore of questionable diagnostic value. C6 serology is sensitive and specific for infection and offers sufficient grounds for treatment if relevant clinical signs are present. Patient side tests include other tick-borne diseases as shown in a Lyme positive case. Recommended treatment is 10 mg/kg for 4 weeks.
There is an update on tick-borne encephalitis (TBEV), transmitted by Ixodes spp. Currently endemic in Russia and parts of Eastern Europe a map shows that it is spreading rapidly in Europe and serological evidence of its presence has been noted in Thetford Forest and in the New Forest. Fatality rates in humans are 1-2%, and although dogs are affected less frequently the fatality rate is higher. There is a list of typical neurological disease signs, and when they are present the disease is often fatal in dogs. The diagnosis is difficult and relies on isolation of the virus from blood or cerebrospinal fluid and/or a fourfold increase in IgG serology titres. Treatment is supportive and symptomatic.
Small Babesia spp, such as B. vulpis, are transmitted by Ixodes spp. Dermacentor reticularis transmits Babesia canis. There is a picture of this tick, demonstrating that it is ornate. There was an outbreak of Babesia canis between November 2015 and February 2016 in Harlow, with the first case presenting to the RVC. There was excellent teamwork involving vets, Harlow council and considerable detective work in tracing where affected dogs had been walked. There have been further outbreaks in Romford (2016), Ware (2017) and infected ticks have been found in Wales, but no further cases have been seen since in untraveled dogs-begging the question ‘is Babesia canis still endemic?’
Babesiosis can be diagnosed via peripheral blood smear, (there are good illustrations), and via serology allowing time to mount a response, but with the added complication of interference from Toxoplasma and Neospora infection. PCR allows speciation. Treatment is summarised, with potential side effects, with the different drugs used for small babesias.
The tricky problem of Rhipicephalus house infection is described next. Its worldwide incidence is depicted, steadily spreading northwards in continental Europe. Its life cycle can be quickly completed and once established in a house there is a significant zoonotic risk. Clinical signs of Ehrlichiosis include anaemia and thrombocytopaenia, lymphadenopathy and neurological signs. The diagnosis is obtained as for Babesiosis.
A map shows the incidence and distribution of ticks in the UK currently. They are present everywhere, with focal distributions in high prevalence areas. Ixodes ricinus accounts for 89% with a small foci of Dermacentor reticularis. Ixodes hexagonus, affecting cats mainly in urban areas, has an incidence of 9.6%. Seasonal fluctuations exist for various species, as shown in a graph. Increased tick numbers have been associated with lots more forest and deer in the last two decades.
Life style risk factors are discussed and colleagues in practice will be well aware of the various means of tick prevention, and treatment. Rapid kill and repellency are vital to reduce transmission, using for example pyrethroids and isoxazolines. As no product is 100% effective, correct removal of ticks is important, and is described. Two useful sites help you to identify ticks:
A final terrifying tick is mentioned at the end of the webinar-it is Hyalomma known as the giant ‘hunter’ tick. It was recently found in Sweden for the first time and has been seen in the UK, probably introduced by migratory birds. It doesn’t rely on questing at the end of vegetation to attach itself but will chase you along the ground in woodland. Stuff of nightmares! Staying on paths and avoiding skin contact with vegetation will increasingly be necessary and advisable.
Ian ends this very good webinar with a justifiable plug for ESCCAP UK & IRELAND:
- Voice and point of cooperation for human tick borne disease groups, government agencies, drug companies and veterinary experts
- Cooperation with PHE, APHA, local councils
- Provides clear and constructive information about effective parasite control
- Brings together some of the UK and Ireland’s leading veterinary parasitological experts
Free and independent advice – www.esccapuk.org.uk