Tick-Borne Disease, Lyme Disease, Rocky Mountain Spotted Fever (RMSF) & Ehrlichiosis

00:00 In this lecture, we’ll discuss tick-borne illnesses in the United States. So, there are different species of tick that can spread different types of diseases. So, for example the deer tick is most commonly implicated in Lyme disease whereas the lone star tick is more implicated in Rocky Mountain Spotted Fever. So, it’s important to know different types of ticks are associated more typically with certain diseases. Prevention is important and in all of the tick-borne illnesses we’re going to talk about today, that is the key thing. Oftentimes in endemic areas, we do tick checks at night. The kids all line up, the parents look them up and down and make sure there's no ticks. Patients in tick-borne illness areas should wear long clothing, socks over pants, they can put permethrin on their clothes if there is a very high rate of tick infestation. Insect repellent is effective against these especially those with DEET and animal control is important too, so we should put anti-tick collars on our dogs. So, let’s briefly review the common tick-borne infections in the United States. We’re going to talk today about Lyme disease, Rocky Mountain Spotted Fever, human monocytic ehrlichiosis, and human granulocytic ehrlichiosis, and then very rarely you might see a case of tularemia. So, there are other diseases in the United States that are very rare that are also spread by ticks. Babesia is found in the northeast along the shore and causes high fevers, it’s somewhat similar to malaria. Tick paralysis is a disease where a patient will become acutely flaccidly paralytic and as soon as you remove the tick, the patient starts improving and can walk home. Colorado tick fever is fairly rare as is Southern Tick Associated Rash Illness or STARI and tick-borne relapsing fever but let’s talk about the common ones.

02:00 One of them is Lyme disease. Lyme disease is endemic mostly in the Eastern United States and has 3 major stages of disease. There’s the early local disease, which usually happens 1 to 2 weeks after the bite of the tick. This presents with the classic rash of erythema migrans or erythema chronicum migrans. Patients will have fever, myalgias, arthralgias, fatigue, headache, and may have some lymphadenopathy. In early disseminated disease, which may happen about a month after the tick, the patients may have a disseminated erythema chronicum migrans rash as well as as meningitis, perhaps a facial palsy, carditis which usually presents as prolonged PR interval or heart block and then a radiculopathy is a rare finding in the US although it’s more common in Europe. Lastly, there is a late stage disease. This usually happens between 2 and 12 months later, so ironically can show up in the winter when you don’t think of seeing any ticks and this is usually just the arthritis of the disease, which is a polyarticular or monoarticular migrating arthritis. So, Lyme disease. It’s diagnosed by testing blood titers which is an ELISA test and a a confirmatory western blot. We do a confirmatory western blot because the Lyme titers have a high false positive rate. For example, a patient with Epstein-Barr virus may test positive for Lyme disease erroneously but the western blot will typically be negative. We don’t recommend testing for Lyme disease if you see early or early disseminated disease. In other words, if you see the rash of erythema chronicum migrans which has a classic bull’s eye like appearance and is rapidly spreading outward, you should not test for Lyme disease. You should not test for Lyme disease because early on, it’s very likely that that test will be falsely negative and you may be misled away from the diagnosis. In general, we can count on patients having Lyme meningitis if they satisfy the Rule of Sevens. So, if we see a patient with Lyme disease or suspected Lyme disease, and they seem to have signs or symptoms of meningitis, we will sometimes do a spinal tap to see what’s going on. When we get that spinal tap, we can use those numbers and the patient’s history to figure out whether this patient is likely to have Lyme meningitis. If they satisfy the Rule of Sevens, this confers a 95% chance that they have Lyme meningitis in endemic areas where this is done. So, what are the Rule of Sevens? The patient should have 7 days of headache, they may have a seventh cranial nerve palsy, or they may have more than 70% of the monocytes on that CSF white blood cell count. So, if a patient has meningitis with a lot of white cells in their spinal tap, and they satisfy either 70% monos, seventh nerve palsy, or 7 days of headache, you can presume that they have Lyme meningitis and treat accordingly while you're awaiting your Lyme titers or any other testing you might do.

05:07 The treatment of Lyme disease has changed a little bit fairly recently, and we now can do some oral antibiotics for patients with meningitis.

05:15 Let's go through it together.

05:17 If the patient's presenting with Lyme erythema migrans, we just need doxycycline for ten days.

05:23 If they're presenting with acute Lyme with meningitis, or neurologic findings, we will typically do doxycycline for 14 to 21 days.

05:33 Or if they are severe ceftriaxone, either be nicely or intramuscularly for 14 to 21 days, if severe.

05:42 For acute Lyme with carditis, we will provide children with doxycycline for 14 to 21 days, or ceftriaxone IV or IM for 14 to 21 days if it is severe.

05:55 Further therapy for late Lyme arthritis would be doxycycline for 28 days.

06:00 And this is key.

06:02 There are patients who come in complaining of chronic Lyme disease, and indeed it is true that there are some patients who get Lyme disease who can have very chronic long dwelling symptoms.

06:13 We call this post-treatment Lyme disease syndrome.

06:17 We don't call it chronic Lyme because a lot of these patients are inappropriately receiving prolonged antibiotics, and that is shown to be absolutely not effective.

06:26 These patients require psychiatric care for their psychiatric illness and support, but antibiotics are not helpful.

06:34 Let's switch minds now to Rocky Mountain Spotted Fever.

06:39 Rocky Mountain Spotted Fever is not actually so prevalent in the Rocky Mountains. It’s perhaps a misnomer. It’s really more found on the eastern seaboard of the United States especially in the Carolinas. Symptoms include fever, thrombosis, and disseminated intravascular coagulation. These patients are sick and they have a high mortality rate. They may complain of severe frontal headache or what we call retroorbital eye pain and they often have CNS involvement. What’s key is the rash. It will be a petechial rash. It generally starts on the hands and feet and then spreads inward. This happens 80 to 90% of the time. Note: There are several classical lab findings with Rocky Mountain Spotted Fever. These include a low level or high level hepatitis, a low white count and low platelets, and these patients may get SIADH or hyponatremia. So, petechial rash hands and feet spreading inward, retroorbital eye pain, hepatitis, low white cells, low platelets, low sodium. If you see this picture, you should be concerned about Rocky Mountain Spotted Fever. So, this is a severe disease, if untreated has a 25% fatality rate. The problem and the reason why I emphasized detecting it clinically is that serologic testing is possible but you need to look for a rise of six-fold over so many weeks and so we can’t make the diagnosis serologically until long after the patient is actually better. So, this is a clinical diagnosis, and if missed, results in fatality in 25% of cases.

08:23 So, we have to be able to recognize this clinical entity. It’s rare, but we can’t miss it. We treat it with doxycycline and you continue the doxycycline until the patient is no longer febrile for 3 days.

08:36 Let’s shift now to ehrlichia or ehrlichiosis. This is similar to Rocky Mountain Spotted Fever but very rare. Generally, fewer patients get the rash only about 20% of the time, and serologic testing is often delayed until after the treatment is completed.

08:54 You have to have a high index of suspicion in this case and we’re going to generally treat with doxycycline. So that’s the summary of the most common of the tick-borne illnesses in the United States. Thanks for your attention.