Disease caused by tick bites, or not?

De eigenaresse moest regelmatig een teek bij Sytske verwijderen na een buitenrit in het bos. (Foto: Sanne Ramkema)

May 17, 2021
After hacking out in the woods the owner frequently needed to remove a tick from Sytske. (Photo: Sanne Ramkema)

The owner of Sytske, an 8-year-old Friesian mare, had been referred to the Animal Clinic De Lingehoeve for further examinations. Their own veterinarian had treated the mare for Lyme disease. Sytske was suspected to have contracted Lyme disease because blood- and dung tests had only revealed a deviation for slightly increased antibody titration of Lyme disease. After a three-week treatment with antibiotics Sytske had not recovered, her condition had in fact deteriorated.

Borrelia bacterium

Equine veterinarian Myrthe Hofstra from De Lingehoeve explains: ‘Lyme disease is transmitted by the Borrelia burgdorferi bacterium. The disease is transmitted by infected sheep ticks that, depending on temperatures, can be active throughout the whole year. Contamination can take place when the tick has been attached for a minimum of 24 hours. Infections with Borrelia can trigger a variety of complaints, like underperforming, on-and-off lameness, fever, night-blindness and abortion’.

Tricky to diagnose

‘To diagnose Borrelia a blood sample is taken from the horse which is then tested for antibodies against the Borrelia bacterium,’ Myrthe continues. ‘Increased antibody titration often leads to the diagnosis ‘Lyme disease’. The tricky bit is that this increased antibody titration is only an indication that the horse has, at some point, been in contact with Borrelia but not if this happened recently and if the clinical symptoms are indeed caused by the Borrelia infection. Important fact is that 44% of healthy Dutch horses have antibodies against Borrelia in their blood.’

Stomach ulcers

Along with the existing problems, the mare was also found to yawn excessively and became a bit oversensitive to the girth. The nature of these complaints was cause to examine the horse for stomach ulcers at de Lingehoeve. She says: ‘Since Lyme disease manifests itself in so many different ways it is difficult to arrive at a correct diagnosis. In Sytske’s case the focus was initially too much on the increased antibody titration. This led to the wrongful assumption that Sytske had fallen ill as a result of a Borrelia infection.’

Other causes

Myrthe Hofstra emphasises that when suspecting Lyme disease, it is key to do a thorough examination into possible other causes that could explain the symptoms: ‘Once these have been ruled out, the symptoms match Lyme disease, there is an increased antibody titration and the horse is known to have had a recent tick bite, then it may be assumed that the diagnosis ‘Lyme disease’ is correct. If the horse responds well to subsequent treatment with antibiotics this is extra confirmation of the diagnosis.’

Read the full real-life story by veterinarian Myrthe Hofstra in the June edition of Phryso

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