York Conference June 2004 - DR David Owen

Tick bites

A few words about tick bites. Most people probably aren’t aware they’ve had a tick bite. They may be what we call ‘silent’. Even if they have they may not think there’s anything significant about it and may not bother going to see the doctor. A lot of people don’t know what ticks are. Some people know because they’ve seen them on their pets and may have seen them on vet programmes on TV. But one thing’s for sure: that the general awareness about the potential for Lyme Disease in the general population is very poor and I’m going to present some data on that later on.

That’s just a photo of a tick feeding, you can see only 2 pairs of legs; head and legs buried under the skin. That’s why of course they are difficult to remove, especially to remove the head which is often left behind. But we think it’s important that the head is removed because there is no doubt that the propensity for Lyme Disease will be dependant on the number of spirochaetes introduced by the tick.

Risk factors for tick bites: exposure of body parts in wild areas of woodland or moorland: walkers, campers, hunters etc are at particular risk and certain occupations such as foresters. But the fact is that anyone who takes a walk in the countryside can be at risk. By far the most common time for tick bites is in the Summer and that may be one reason why the incidence of Lyme Disease is reported to be mainly in the Summer.

So this is a graph showing the reported times of onset in the year for Lyme disease. Now, that may be because people like to go out in the summer but it may in fact be, and I don’t know if anyone has got data on this, that even someone who’s carried Borrelia for a long time tend to become symptomatic during the summer months.

If anyone knows any more about that, please let me know.

Diagnosis

I’ve been diagnosed with Lyme Disease so this is where it gets a bit tricky, but one of the most important things I’m going to say is that Lyme Disease is essentially a clinical diagnosis. The CDC in America acknowledge the fact that serology isn’t helpful as false negatives and false positives occur very frequently. Another misconception is that inflammatory markers are usually raised in Lyme Disease. Certainly the ones quoted for CRP and ESR may be are normal and usually are, and most cases overlooked. But I think that we can safely remove the question mark from that.

One of the other things to bear in mind regarding the diagnosis is that we are often dealing with a chronic condition which may have been there for years and years. This may have been relapsing, it come and goes. Almost always it is multi-systemic, and as a result there can be a huge diversity in the types and the severity of the symptoms.

Lyme Disease may present to any speciality and it may be present early on or it can occur years after a tick bite.

Further points about the diagnosis: I’m not going to go into the CDC criteria, I’m sure this will come up later on. It’s based on a points system and most often we can’t say for certain whether the diagnosis is there. The CDC criteria make it very important to have Erythema migrans but we know that that’s not present in all cases and it is present in less than 50% that’s what the ILAD guidelines quote, but it may be present in less than 10% , we just don’t know.

There are very few other physical findings. Lyme Disease produces a mild encephalopathy and I think the concept of encephalopathy is more developed in the States. Encephalopathy is essentially a brain condition which can produce a diverse variety of symptoms from cognitive impairment to pure mental health symptoms. It is suggested that you should suspect Lyme Disease when arthritides (that’s body pains) are present with mild encephalopathy.

How common is Lyme Disease in CFS and fibromyalgia? Well we don’t know, but it may be very common. Other clues to diagnosis: if someone has a strong Herxheimer reaction with antibiotics- that’s suggestive.

Erythema migrans. It’s very variable, difficult to diagnose. Not all cases are central clearing (bull’s eye rash) and histology isn’t diagnostic. It’s very rarely possible to see spirochaetes, certainly from reports. Common on legs, especially groins, Erythema migrans (EM) may appear anywhere in the body and come in multiples from multiple tick bites. It is quite common for the EM to occur a slight distance away from the tick bite. So these can clear or may be present for very long periods. They used to be called ECM or erythema chronica migrans.