Tick-borne disease

# Overview
Tick-borne diseases are diseases or illnesses transmitted by ticks. As the incidence of tick-borne illnesses increases and the geographic areas in which they are found expand, it becomes increasingly important that health professionals be able to distinguish the diverse, and often overlapping, clinical presentations of these diseases.

# Tick-borne disease Classification

# Pathophysiology
Tick-borne illnesses are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. Because ticks can harbor more than one disease-causing agent, patients can be infected with more than one pathogen at the same time, compounding the difficulty in diagnosis and treatment.

## Life Cycle and Spread of Disease

### General Tick Life Cycle
- A tick's life cycle is composed of four stages: hatching (egg), nymph (six legged), nymph (eight legged), and an adult.
- Ticks require blood meal to survive through their life cycle.
- Hosts for tick blood meals include mammals, birds, reptiles, and amphibians. Ticks will most likely transfer between different hosts during the different stages of their life cycle.
- Humans are most often targeted during the nymph and adult stages of the life cycle.
- Life cycle is also dependent on seasonal variation.
- Ticks will go from eggs to larva during the summer months, infecting bird or rodent host during the larval stage.
- Larva will infect the host from the summer until the following spring, at which point they will progress into the nymph stage.
- During the nymph stage, a tick will most likely seek a mammal host (including humans).
- A nymph will remain with the selected host until the following fall at which point it will progress into an adult.
- As an adult, a tick will feed on a mammalian host. However unlike previous stages, ticks will prefer larger mammals over rodents.
- The average tick life cycle requires three years for completion.
Different species will undergo certain variations within their individual life cycles. 
- Different species will undergo certain variations within their individual life cycles. 
Spread of Tick-borne Disease
- Ticks require blood meals in order to progress through their life cycles.
- The average tick requires 10 minutes to 2 hours when preparing a blood meal.
- Once feeding, releases anesthetic properties into its host, via its saliva.
- A feeding tube enters the host followed by an adhesive-like substance, attaching the tick to the host during the blood meal.
- A tick will feed for several days, feeding on the host blood and ingesting the host's pathogens.
- Once feeding is completed, the tick will seek a new host and transfer any pathogens during the next feeding process. 

# Epidemiology and Demographics

## Incidence
- Tick based infections are generally non-specific in regards to age, race, or gender. (However babesiosis is more frequently observed in older, male populations. An explanation for this has not yet been formulated.) 
- Certain tick-borne illnesses will vary within patient populations when an auto-immune deficiency is present.
- Tick bites are more frequently reported during the spring and summer months which are noted to be in correlation with high tick activity.
- Higher risks are associated with individuals traveling within endemic areas.
- Inoculation within endemic areas is usually the result of a tick bite however transmission has been identified as a result of transfusions or transplantation.

## Species and Regions

### United States
American Dog Tick (Dermacentor Variabilis) 
- Pacific Coast and east of the Rocky Mountains.
- Transmits tularemia and rocky mountain spotted fever.
- Primarily infects humans during the spring and summer months.
Blacklegged tick (Ixodes Scapularis) 
- Northeastern and upper Midwest.
- Transmits Lyme disease, babesiosis, anaplasmosis, and Powassan disease.
- Primarily infects humans during the spring, summer, and fall months.
Brown dog tick (Rhipicephalus Sanguineus) 
- Widespread throughout the United States.
- Transmits Rocky mountain spotted fever.
Gulf Coast Tick (Amblyomma Maculatum) 
- Atlantic Coast and Gulf of Mexico (Along the coast of Northeastern Virginia until the Southern most portions of Florida. From Southeast Florida through the Gulf of Mexico into Texas).
- Transmits Rickettsia parkeri rickettsiosis (spotted fever).
Lone Star Tick (Amblyomma Americanum) 
- Southeastern and Eastern United States.
- Transmits Ehrlichiosis, tularemia, STARI and Bourban virus.
Rocky Mountain Wood Tick (Dermacentor Andersoni) 
- Colorado, Nevada, eastern California, eastern Oregon, eastern Washington, Idaho, Montana, Wyoming, and Utah.
- Transmits Rocky mountain spotted fever, Colorado tick fever, and tularemia.
Western Blacklegged tick (Ixodes Pacificus) 
- Pacific Coast
- Transmits Anaplasmosis and Lyme Disease.

### International
Hyalomma Marginatum 
- Widespread: North Africa, Europe, and Asia.
- Transmits Crimean-Congo hemorrhagic fever.
Ixodes Ricinus 
- Widespread throughout Europe and parts of North Africa.
- Transmits encephalitis and Lyme Disease.
Ixodes Persulcatus 
Dermacentor Reticulatus 

# Differentiating Tick-Borne Diseases from other Diseases

# Risk Factors
- The greatest risk factor associated with tick-borne diseases is actually being bitten by a tick.
- Traveling or residing within endemic regions will increase chances of infection.
- Tick activity is generally heightened during certain the spring and summer months.
- Within endemic regions, tick may choose an animal host, including a domesticated animal such as a dog or cat.
- Although rare, cases of blood transfusion and organ transplantation have been recorded as methods of transmission.
- All together, individuals who spend time outdoors and/or have pets that go outdoors in endemic regions are at risk for tick-borne disease. 

# Diagnosis
Physical Examination
A round red rash with a 2-5 mm central black area (eschar, an area of dead tissue) as shown in the photo is suggestive of a tick bite.
Laboratory Findings
In general, specific laboratory tests are not available to rapidly diagnose tick-borne diseases. Serological tests are frequently performed, but may be unreliable in differentiating acute from chronic conditions.

# Treatment

## Medical Therapy
- Antibiotic treatment is often justified based on clinical presentation alone. However all clinical treatments must be tailored according to a patients personal profile; considering age, immunocompetance, pregnancy, allergen profile, splenic function, and current medical status. 
- If there is a collection of pus, the area will need to be incised and drained.

# The best way to remove a tick
- Use fine-tipped tweezers or notched tick extractor, and protect your fingers with a tissue, paper towel, or latex gloves. Persons should avoid removing ticks with bare hands.
- Grasp the tick as close to the skin surface as possible and pull upward with steady, even pressure. Do not twist or jerk the tick; this may cause the mouthparts to break off and remain in the skin. (If this happens, remove mouthparts with tweezers. Consult your health care provider if illness occurs.)
- After removing the tick, thoroughly disinfect the bite site and wash your hands with soap and water.
- Do not squeeze, crush, or puncture the body of the tick because its fluids may contain infectious organisms. Skin accidentally exposed to tick fluids can be disinfected with iodine scrub, rubbing alcohol, or water containing detergents.
- Save the tick for identification in case you become ill. This may help your doctor to make an accurate diagnosis. Place the tick in a sealable plastic bag and put it in your freezer. Write the date of the bite on a piece of paper with a pencil and place it in the bag. 

# Gallery
- Tick bite. Adapted from Dermatology Atlas.
- Tick bite. Adapted from Dermatology Atlas.
- Tick bite. Adapted from Dermatology Atlas.