1. Introduction to Tickborne Diseases
Rachel Radcliffe, DVM, MPH
CDC Career Epidemiology Field Officer
Division of Infectious Disease Epidemiology
Good morning.

2. Overview of Tickborne Diseases
Introduction
Lyme disease
Tickborne rickettsial diseases
Babesiosis
Prevention of tickborne diseases
Case ascertainment exercise
In the next two hours, we will present basic clinical and epidemiological information on tickborne diseases. We’ll start out with an introduction to these diseases that includes just general information. Then we will focus more on tickborne diseases most commonly seen in WV with presentations on lyme disease, TBRD, and babesiosis. At the end, we will have discussion on prevention of tickborne diseases. And we will finish with some exercises on case ascertainment.

3. Tickborne Diseases Diseases spread by bites from infected ticks
Can be caused by bacteria, viruses, and parasites
Most infections occur in the spring and summer months
Geographic distribution of tick species impacts location of human infections
Tickborne diseases are spread to humans by bites from infected ticks. There are numerous tickborne diseases that are caused by different pathogens including bacteria, viruses, and parasites. Most tickborne infections occur in the spring and summer months when ticks actively feed on humans. Because various tick species transmit different diseases, the geographic distribution of these tick species impacts the location of human infections.

4. Tick Life Cycle Hard ticks have four life stages Egg Six-legged larvae
Eight-legged nymph
Adult
Most ticks prefer to feed on different hosts at each life stage
Ticks can feed on mammals, birds, reptiles, and amphibians
Hard ticks that transmit tickborne diseases have four life stages: egg, six legged larvae, eight legged nymph, and adults. Most tick species prefer to feed on different hosts at each of these life stages. Ticks can feed on a variety of animals including mammals, birds, reptiles, and amphibians.

5. This diagram shows an example of a tick life cycle
This diagram shows an example of a tick life cycle. The eggs hatch in the spring and develop into larvae. The larvae feed on birds and small mammals. If these birds and small mammals have a pathogen in their bloodstream, the tick will ingest this pathogen as they feed on the animal’s blood. Through the fall and winter the larvae develop further and emerges as nymphs in the following spring. As nymphs, the ticks will feed on larger mammals including deer and humans throughout the spring and summer. If the tick was infected with a pathogen at the larval stage while feeding on a bird or small mammal, it will pass this pathogen on to its next host, such as a human, as it feeds in the nymph stage. The nymph develops into an adult which can also feed on larger mammals and eventually lay eggs to start the life cycle over.
The birds and wild mammals that ticks feed on actually serve as reservoirs for the pathogens of tickborne diseases and are a necessary part in the transmission of these diseases. In contrast, humans generally act as incidental or dead-end hosts and do not further propagate the transmission of tickborne diseases.

6. Symptoms of Tickborne Diseases
Many diseases produce similar symptoms
Asymptomatic or mild to life-threatening illness
Most common symptoms
Fever/chills
Aches and pains
Rash
Proportion of people with rash varies among diseases
Distinctive rash appearance among diseases
Many tickborne diseases produce similar symptoms in humans and can manifest clinically as asymptomatic or mild illness to life-threatening illness. The most common symptoms of tickborne diseases include fever and chills, aches and pains, and rash. Not every person with a tickborne disease will develop a rash and the proportion of people that do varies with each disease. A distinctive rash appearance can be seen among some of the diseases and this will be discussed later in the presentation.

7. Treatment of Tickborne Diseases
Supportive therapy
Antibiotic therapy for bacterial tickborne diseases
Doxycycline commonly used
Duration of therapy varies by disease
Treatment for tickborne diseases varies but generally includes supportive therapy. Antibiotic therapy is useful for those diseases caused by bacteria and doxycycline is commonly used for several diseases. The duration of therapy varies by disease and will be discussed in further detail as this presentation continues.

8. Diagnosis of Tickborne Diseases
Can be difficult to diagnose
Clinical signs and symptoms
Patient history
Tick bite or tick exposure
Laboratory findings
Diagnostic tests
Serology
Polymerase chain reaction (PCR)
Immunohistochemistry (IHC)
Culture
The diagnosis of tickborne diseases can be very difficult, particulalry because the symptoms can be non-specific. However, the clinical signs in conjunction with the patient’s history can offer some clues. A history of a tick bite or tick exposure and where this occurred can be helpful. Certain laboratory tests, such as a CBC or metabolic panel, can also offer some good information. Diagnostic tests include serology, PCR, IHC, and culture. These tests will be discussed in more detail as they pertain to each disease.

9. Tickborne Diseases in the United States
Lyme disease
Rocky Mountain Spotted Fever
Other Spotted Fevers
Ehrlichiosis
Anaplasmosis
Babesiosis
STARI
Powassan
Tularemia
Others
Here is a list of some of the tickborne diseases found in the United States. I will briefly give some general information about each of these diseases and several will be covered in more detail later.

10. Lyme Disease Most common tickborne disease in US Bacterial disease
Borrelia burgdorferi
Transmitted by blacklegged tick and western blacklegged tick
Lyme disease is the most common tickborne disease in the United States. This is a bacterial disease caused by the bacteria Borrelia burgdorferi. Lyme disease is transmitted by the blacklegged tick and the western blacklegged tick.

11. Geographic Distribution of Blacklegged Tick
This map shows the geographic distribution of the blacklegged tick as noted by the orange color. Notice that WV is part of this tick’s range. The other tick that transmits Lyme disease, the western blacklegged tick is only found on the western coast, so I will not present a map of its distribution.
I will show several more maps similar to this throughout the rest of the introduction. However, I will only show maps for ticks that are found in WV. For more distribution maps of other tick species not found in WV, please see the CDC’s tickborne disease website.

12. Rocky Mountain Spotted Fever and Other Spotted Fevers
Bacterial diseases
Rickettsia rickettsii
Rickettsia parkeri
Rickettsia phillipi (proposed)
Transmitted by American dog tick, Rocky Mountain wood tick, brown dog tick, Pacific coast tick, and Gulf coast tick
Rocky Mountain Spotted Fever and other spotted fevers are bacterial diseases caused by the bacteria Rickettsia ricketsii, rickettsia parkeri, and rickettsia phillipi. These diseases can be transmitted by the American dog tick, Rocky Mountain wood tick, brown dog tick, pacific coast dog tick, and gulf coast tick.

13. Geographic Distribution of American Dog Tick
Here is the geographic distribution of the American dog tick and WV is completely within this ticks range.

14. Geographic Distribution of Brown Dog Tick
The brown dog tick is found throughout the US. The other tick vectors of spotted fevers are not found in WV so their distributions are not shown here.

15. Ehrlichiosis and Anaplasmosis
Bacterial diseases
Ehrlichia chaffeensis
Ehrlichia ewingii
Anaplasma phagocytophilum
Transmitted by blacklegged tick, lone star tick, and western blacklegged tick
Ehrlichiosis and Anaplasmosis are bacterial diseases caused by the bacteria Ehrlichia chaffeensis, Ehrlichia ewingii, and Anaplasma phagocytophilum. These diseases are transmitted by the blacklegged tick, the lone star tick, and the western blacklegged tick. Notice some of these tick species are the same ones that transmit lyme disease.

16. Geographic Distribution of Lone Star Tick
This map shows the geographic distribution of the lone star tick. Notice the northern border of this tick’s range is around WV.

17. Babesiosis Caused by parasites that infect red blood cells
Species found to infect humans include Babesia microti, B. divergens, and B. duncani
Transmitted by blacklegged tick
Less commonly congenital transmission and blood donor-associated cases have been identified
Babesiosis is caused by parasites that infect red blood cells. Species of this parasite that have been found to infect humans include Babesia microti, babesia divergens, and babesia duncani. Like Lyme disease, babesiosis is transmitted by the blacklegged tick. Less commonly congenital transmission and blood donor-associated cases of babesiosis have been identified.

18. STARI (Southern Tick Associated Rash Illness)
Cause is unknown
Rash appearance similar to Lyme disease
Has not been linked to arthritic, neurologic, or chronic symptoms
Transmitted by lone star tick
Most cases found in southeastern US
STARI or Southern Tick Associated Rash Illness is a newly recognized disease and the cause is unknown. The rash seen in this disease has a similar appearance to the rash seen with Lyme disease, however this disease has not been linked with arthritic, neurologic, or other chronic symptoms like those seen with Lyme disease. STARI is transmitted by the lone star tick and most cases have been found in the southeastern part of the US. The distribution of the lone star tick has already been shown.

19. Powassan Arbovirus Causes encephalitis Most cases in northern US
Transmitted by blacklegged tick and a related tick, Ixodes cookei
Powassan is actually an arbovirus that is transmitted by ticks. Similar to other arboviruses, Powassan causes encephilitis and most cases have been identified in the northern US. This virus is transmitted by the blacklegged tick and a related tick called Ixodes cookei.

20. Tularemia Less common tickborne disease Bacterial disease
Francisella tularensis
Transmitted by American dog tick, lone star tick, and Rocky Mountain wood tick
Other transmission routes include deer fly bites, inhalation, ingestion, skin contact with infected animals
Cases found in every state except Hawaii
Tularemia is a less commonly identified tickborne disease and it is caused by the bacteria, Francisella tularensis. It is tranmsitted by the American dog tick, the lone star tick, and the rocky mountain wood tick. Based on the tick distribution maps shown earlier, remember that the American dog tick and the lone start tick have ranges in or around WV. Other transmission routes of tularemia include deer fly bites, inhalation, ingestion, and skin contact with infected animals. Cases of tularemia have been found in every state except Hawaii.

21. Other Tickborne Diseases
Tickborne relapsing fever
Colorado tick fever
Tickborne diseases abroad
Tickborne encephalitis
Crimean-Congo hemorrhagic fever
There are many other tickborne diseases that we don’t have time to cover today. These include Tickborne Relapsing Fever and Colorado tick fever. There are specific tickborne diseases found abroad that travelers should be aware of and take proper precautions to protect themselves while traveling. These include tickborne encephalitis and crimean-congo hemorrhagic fever, both of which are caused by viruses.

22. Summary
Numerous tickborne diseases can infect humans and cause disease
Several tick species transmit tickborne diseases
Found in various geographic regions
Symptoms can be similar among tickborne diseases
Diagnosis can be difficult
This short introduction was intended to show that numerous tickborne diseases can infect humans and cause disease. Several different tick species are responsible for transmitting these diseases and can be found throughout different geographic regions of the United States. In addition, some tick species can transmit more than one disease. Symptoms can be similar among the tickborne diseases and diagnosis of these diseases can be difficult.

23. More Information to Come…
Lyme disease
Tickborne Rickettsial diseases
Rocky Mountain Spotted Fever
Ehrlichiosis
Anaplasmosis
Babesiosis
Prevention of tickborne diseases
Several tickborne diseases are reportable and we will be discussing the surveillance of these diseases as the presentation continues. These include lyme disease, the Tickborne Rickettsial diseases of RMSF, Ehrlichiosis, and Anaplasmosis, and Babesiois. Prevention measures for tickborne diseases will also be discussed.

24. Case Investigation Procedure
Positive lab report received at health department
Call healthcare provider
Collect clinical data, patient history, supplemental labs
Follow up if no response after 3-4 days
If needed, attempt to contact patient
Collect exposure and other relevant information from case
Attempt patient contact for 5-10 days
Enter all data into WVEDSS and send case to regional review
As we talk more about surveillance, here is an example flow chart for case investigation. This may be a good reference as we talk in more detail about surveillance (and should be available as handout in your packet). This chart will appear again in the case ascertainment exercise.
Next up is Jonah Long, the zoonotic disease epidemiologist for our division and he will be speaking about Lyme disease.