For those of you who may have missed the most recent press release from the CDC on August 14th, the incidence of the potentially deadly West Nile Virus is back with a vengeance.
Educational Objectives:
After evaluating this article, participants will be able to:
1. Develop strategies to better identify tick borne diseases;
2. Incorporate into practice the current treatment recommendations for many vector borne diseases
For those of you who may have missed the most recent press release from the CDC on August 14th, the incidence of the potentially deadly West Nile Virus is back with a vengeance. A total of 693 cases within 32 states have been identified with preponderance within Texas, Oklahoma, Louisiana, and Mississippi. Thus far, 26 deaths have been reported with 58.6% of patients experiencing neuroinvasive disease. This most recent outbreak represents the highest number of cases since 2004.
After reading this information, I am reminded that you can’t stop vector borne disease (VBD), you can only hope to contain it. But then I ask: What I am supposed to know about VBD regarding patients presenting to my ED? Isn’t every patient just a concoction of a febrile illness with non-specific symptoms that I treat supportively? Perhaps one of the greatest frustrations with VBD is the paucity of literature to make clinical decisions and apply best evidence.
To that end, this article will provide some data on common – and a few less common – VBDs, busting a few common myths along the way.
Tick Borne Disease
The majority of tick borne disease present as febrile illness with constitutional symptoms. Given the duplicative nature of presentation of most TBD, here is a short list of pearls in the history/exam/treatment that may in fact filter the differential. For example, tularemia is associated with pulse-temperature dissociation (relative bradycardia), tick borne relapsing fever with multiple febrile-afebrile periods, Colorado tick fever with a bi/triphasic fever, and Powassan virus with seizures and encephalitis. As erythema migrans is to Lyme disease (90%), a morbilliform rash on the palms and soles is to Rocky Mountain Spotted Fever which places meningococcemia in the differential of those patients. If triage accidently ordered the CBC on this patient with febrile illness and the picture fits one of hemolytic anemia and dare I say, you asked the lab to do a peripheral smear yielding intraerythrocytic parasites, have Babesiosis at the top of your list. Regarding treatment, I remind myself of my medical student days and the Jarisch Herxheimer reaction which is seen in a majority of patients following treatment initiation of tick born relapsing fever (TBRF); and to avoid initiation of anticoagulant usage in patients with RMSF due to the increased risk of hemorrhage.
Similar to WNV, patients presenting with neurologic/cardiac involvement following tick bite/exposure are most concerning for us. Neurologic involvement from ticks can include tick paralysis (ascending flaccid paralysis with gait disturbance – most often truncal ataxia with wide based staggering gait – in absence of sensory abnormalities which is reversible if the tick is removed within 48 hours), cranial nerve palsies (Lyme CN VII), meningitis/encephalitis, and seizures; while cardiac involvement ranges from myocarditis/pericarditis to the notorious conduction disturbances associated with Lyme. Where then is a reasonable approach to the assessment/treatment of these patients for us in the ED? As noted previously, one of the more challenging aspects of treatment of TBD is the lack of high quality studies (most are retrospective reviews) within the literature to guide treatment decisions. Based on the literature here is a strategy utilizing evidence in the evaluation of patients presenting after tick bite exposure to apply to your patients.
Recall 4 Questions
1. Has there been a tick bite? The better question as a result of the fact that less than 50% of patient’s recall a bite as well as the fact that they are small, painless, and present on discrete locations, is whether there has been tick EXPOSURE. This can include both occupational as well as recreational.
2. For how long was the tick attached? Literature is fairly clear that 24 hours of tick attachment are required in order to propagate disease. Some reports use 36/48 hours but general consensus is 24. There is no evidence to support the utilization of antibiotics in an asymptomatic patient.
3. Is this an endemic area for ticks? Despite their higher prevalence in certain regions, tick borne diseases are found throughout the entire US.
4. Is this patient symptomatic? Translation: Does my patient have a fever and/or rash? Either implies disease propagation. A good rule of thumb is every patient presenting with febrile illness should have tick bite within the differential diagnosis.
Case Example
- A 45 year-old male presents to your ED in midsummer after backpacking in Northern California with the following:
- CC: Fever x 3 days
- HPI: (+) myalgias, athralgias, nausea,
- vomiting x2, headache (4/10)
- Pertinent vitals: 102.6
- PE: tachycardic , mild diaphoresis, o/w WNL
Utilizing the strategy and applying it to this case would yield the following:
Question 1: No known bite – however, there was potential tick exposure given his backpacking trip in California.
Question 2: Unknown
Question 3: Yes
Question 4: Yes
This patient should be treated – and actually had a bite from an Ixodes tick. Within the Western US, Ixodes scapularis (vector for Lyme disease) is Ixodes Pacificus and a transmitter of Anaplasmosis (previously described as Human Granulocytic Erlichiosis). This brings up a critical point – tick borne disease may present atypically as a result of co-infections since some ticks will carry more than one pathogen. The most prominent example of this is Ixodes which can lead to Anaplamosis, Lyme disease, and/or Babesiosis.
The same is true for the American Dog Tick which can transmit both Tularemia as well as Rocky Mountain Spotted Fever (RMSF).
Tick Myth: Doxycycline should be withheld in children less than 8 years old who have suspected RMSF/Erlichiosis/Anaplasmosis
While doxcycline can be used to treat most tick born infections including RMSF, Erlichiosis, Anaplasmosis, Lyme Disease, Tick borne Relapsing Fever (TBRF), and STARI (Southern Tick Associated Rash Illness), most practitioners have concern regarding the staining of teeth associated with its use in those less than 8 years old. As per the CDC and the American Academy of Pediatrics Committee on Infectious Diseases, unlike older tetracyclines, the recommended dose and duration of medication needed to treat RMSF has not been shown to cause staining of permanent teeth, even when five courses are given before year eight. Use of antibiotics other than doxycycline increases the risk of patient death from both RMSF and Erlichiosis. Thus, if you suspect RMSF/Erlichiosis/Anaplasmosis, initiate doxcycline therapy irrespective of age. In contrast, Lyme/STARI and TBRF can be treated with alternative medications in children less than 8 years old – specifically, Amoxicillin (50mg/kg PO q8h x 14-21 days) and PCN V (25-50 mg/kg/d – max 500mg/dose PO divided in 4 doses x 7 days) or PCN-G (25000-50000 IU/kg/d IV divided in 4 doses x 7 days), re
spectively.
West Nile Virus
As with most VBD, WNV is a seasonal epidemic occurring in the summer and fall through spread of an infected mosquito. While reported cases of transmission have been documented via spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby, these remain the minority. The two types of cases are neuroinvasive and non-neuroinvasive. As EPs, recognition of neuroinvasive disease is by far the most important. Neuroinvasive WNV can present as any of the following: encephalitis, meningitis, or acute flaccid paralysis – sometimes referred to as West Nile poliomyelitis. This flaccid paralysis tends to affect one side of the body more than the other and is not associated with sensory deficit and can occur in absence of encephalitis/meningitis or fever.
West Nile Myth: Like tick born paralysis, if caught early neuroinvasive WNV is reversible
This is one of the contrasting features of paralysis secondary to WNV – paralysis will be persistent in some cases while others will only reveal partial recovery. Irrespective of age and pre-existing medical conditions, all populations are at risk for neuroinvasive disease despite the higher likelihood of it in those over 50.
General Prevention
Short of not going outside for five months or wearing a space suit, the best means to prevent VBD is to decrease the risk of transmission of bites from the two main vectors – ticks and mosquitoes.
This is best accomplished through use of repellents on the skin and clothing. Advising your patients on utilizing any of the following will provide adequate protection: DEET, Picardin, Oil of Lemon Eucalyptus, PMD (synthesized version of lemon eucalyptus), or IR3535. For clothes, bed nets, and camping gear, permethrin can be directly applied and is both an insecticide and repellent.
General Prevention Myth: “I thought that DEET and Picardin are not to be used in children?”
DEET is safe in children older than two months with a marginal risk of toxicity (0.05-0.1%) and Picardin can be used in any child after 2 years.
The bottom line in VBD is simple – while most cases of TBD go undiagnosed, are self limiting, and patients more often than not will never end up in the ED – EPs should keep a heightened sense of awareness. Utilizing a rational, evidence-based approach to pick off the outliers in the face of a wide variety of clinical presentations ranging from dermatologic to constitutional, hematopoietic, cardiovascular and neurologic will help to ensure optimal outcome in these patients.
