There Are Eleven Diseases Which Humans Can Get from Ticks in North America. One Is Caused

Tick Talk

There are eleven diseases which humans can get from ticks in North America. One is caused by a neurotoxin, one by Rickettsia, two by Ehrlichia, two by viruses, and four by bacteria. These diseases, which we will discuss here, are Tick Paralysis, Babesiosis, Rocky Mountain Spotted Fever, Human Monocytic Ehrlichiosis, Human Granulotic Ehrlichiosis, Powassan Encephalitis, Colorado Tick Fever, Lyme Disease, Tularemia, Southern Tick Associated Rash Illness, and Relapsing Fever.

When travelling or working in tick infested areas there are a few basic precautions which should be taken. Wearing long sleeved shirts with snug cuffs, long pants (preferably with snug cuffs or bloused), using a 20% or better DEET based repellent (such as 3M Ultrathon-33%, Ben’s 30 – 30%, or Sawyer’s controlled release lotions – 20%) on exposed skin, and treating clothing and bedding with a Permethrin based compound. Sawyer products offers a “shake n’ bake kit for clothing which is based upon the military treatment kit. This method of clothing treatment can last through up to 50 washings! Aerosol spray treatments are available from many manufacturers and usually last through 6 washings.

Tents, sleeping bags, hammocks, and bug netting can be treated with Permethrin sprays to minimize infestations. Permethrin is safe to use as it stays on the material and does not absorb into the body. DEET has been under scrutiny for absorption and most DEET products now available in the USA and Canada have been proven safe. A good rule is to avoid applying on your lips, in the eyes, or on open wounds.

Lately wrist bands with DEET or Permethrin in them have appeared under various brands…these The same goes for insect collars designed for use on animals, they can be harmful when worn by humans. Eating match heads will not reduce the risk of tick bites, nor will swallowing a half of a cigarette (good field treatment for intestinal worms though).

Most ticks wander around on your body for a while before finding a suitable place to set up camp. It should become a regular practice to inspect your body each day for these little hitch hikers. Most tick borne diseases are not transmitted until 24 hours have passed so quick discovery and removal is paramount. Grab a “tick buddy” and carefully inspect each other for any ticks. Use an adhesive lint roller or wrap tape around your hand (sticky side out) to remove small, hard to see ticks from your clothes. Wash your clothes regularly to remove insects and their eggs (not to mention improving insulative value).

Remove attached ticks immediately:

· Grasp the tick’s mouthparts as close to the skin as possible with fine-tipped tweezers; pull back slowly and steadilywith firm force until the barbed mouthparts can be eased out of the skin. Be patient.

· DO NOT squeeze the body of the tick or apply any substance, including petroleum jelly, finger nail polish, fingernail polish remover, repellents, pesticides, or a lighted match to the tick, while it is attached. These materials ormethods are either ineffective, or worse, might force more infective fluid into the bite site.

· After removal, wash the bite site and apply an antiseptic.

· Save the tick for future identification should you develop disease symptoms. Preserve the tick by placing it in aclean, dry jar (or other sturdy container) and keeping it in the freezer. You may discard the tick after about onemonth, as tick-borne diseases will generally display symptoms within this time period.

· If you develop flu-like illness or rashes, or otherwise feel sick after the tick bite, seek medical attention immediately.Take the tick with you to the clinic. Prompt diagnosis and treatment will likely speed your recovery and preventlingering symptoms.

The Rogue’s Gallery

Not all ticks are guilty of disease transmission. These little mugs are the ones we really have to be on the lookout for:

Ixodes Cookei Ornithodoros Hermsii

American Dog Tick – Female above, Male below

Well, let’s get on with the diseases…

Neurotoxin - Tick Paralysis.

Tick paralysis is a tick-borne disease affecting both humans and other animals, and it is characterized by the sudden onset of a progressive, ascending (starting in the lower body and moving up) paralysis. Unlike other tick-borne diseases, such as Rocky Mountain spotted fever, tick paralysis is not caused by an infectious agent (pathogen) but rather, is induced by a chemical substance that attacks the nervous system (neurotoxin). This neurotoxin is secreted by the salivary glands of certain tick species as they feed. Tick paralysis is relatively rare, but it can be fatal if the attached tick is not found and removed. The majority of cases occur in children.

Although tick paralysis is associated with over 40 species of ticks worldwide, only two species are most often to blame in North America. They are Dermacentor andersoni (Rocky Mountain wood tick) in British Columbiaand the northwestern United States, where the largest numbers of human cases are reported, and Dermacentor variabilis (American dog tick) in the southeastern U.S. Other species may occasionally be involved. They include: Ixodes scapularis (blacklegged tick), Ixodes pacificus (western blacklegged tick), and Amblyomma americanum (lone star tick). In Australia, Ixodes holocyclus (Australian paralysis tick) is the culprit. Additional tick species account for the sporadic cases that occur in Europe, Africa, and South America. Only adult female ticks appear to produce the toxin responsible for causing tick paralysis.

Once attached to a host (human or animal), a female tick feeds for many days in order to acquire enough blood to produce her large brood of eggs. It is during this prolonged feeding process that the female tick manufactures a paralysis-inducing toxin in her salivary glands. This chemical is then transmitted to the host in the tick’s saliva. While pathogens can proliferate and continue to cause disease in an individual long after an infective tick has been removed, tick paralysis can only occur while a tick is attached and pumping toxin into the bloodstream. Therefore, once the tick is removed, symptoms resolve and recovery is usually rapid.

Approximately five to seven days after a tick has become attached, a person begins to feel restless, weak, and irritable. Numbness begins to be experienced in the legs, then paralysis rapidly develops and moves from the lower to the upper extremities. This is followed by paralysis of the tongue and face. The most severe complications may include convulsions, respiratory failure as the muscles that control breathing become paralyzed, and death. If the offending tick is not located and removed, tick paralysis may be fatal in approximately 10-percent of cases.

There are no laboratory tests to diagnose tick paralysis. Therefore, diagnosis is based on symptoms and a history of known or likely exposure to ticks (e.g. finding an attached tick; recreational activities such as camping; living in a tick-infested area; or having pets that spend time outdoors). If a tick is found and removed, rapid improvement of symptoms confirms the diagnosis.

There are no specific treatments for tick paralysis, other than supportive care and tick removal. Tick paralysis is cured by quickly finding and removing the tick. Therefore, if exposure to ticks is a possibility, it is crucial to check the body carefully and thoroughly for an attached tick. Ticks are often attached to the head and neck where they may be concealed by hair. If breathing is impaired, oxygen therapy or mechanical ventilation may be necessary. Removing the tick removes the source of the neurotoxin, and symptoms generally improve rapidly.

Protozoa – Babesiosis

Babesiosis is a potentially severe, and sometimes rapidly fatal, tick-borne illness caused by a protozoan parasite that infects anddestroys the red blood cells. Babesia microti appears to be responsible for the majority of cases of human babesiosis in the UnitedStates. It is the most common species in the eastern and Midwestern U. S. where most cases occur. Additional types of Babesia thathave been associated with human disease in limited areas of the U.S., but that have not yet been designated as distinct species, arecurrently known only as Babesia isolate type WA1 parasites (detected on the West Coast) and Babesia isolate type MO1 (detected inMissouri). Babesia divergens is the most common species in Europe. Other Babesia species cause illness in animals.

You can get babesiosis if you are bitten by a tick that is infected withB. microti, or less commonly, another Babesia species. Protozoa in the tick’ssaliva are transmitted to you while the tick is feeding. An infected tick must beattached to you for at least several hours (usually 24-48) in order fortransmission to take place. Occasionally, babesiosis has also beenacquired via blood transfusion from apparently healthy, but nevertheless infected, individuals.

Only certain species of ticks are capable of transmitting Babesia. There are two vectors of Babesia to humans in the United States. Ixodesscapularis, the blacklegged tick (also known as the “deer tick”), is the primaryvector for Babesia in the east and Midwest, while Ixodes pacificus, the westernblacklegged tick, is a presumptive vector along the West Coast. Ixodes ricinus,sometimes referred to as the sheep tick or European castor bean tick, transmits B.

divergens in Europe. Simultaneous infections with both B. microti and Borrelia burgdorferi, the agent of Lyme disease, have beendocumented in ticks, and there is evidence that both organisms may be transmitted during a single tick bite.

Ticks become infected by feeding on an infected animal known as a reservoir host. Reservoir hosts carry Babesia parasites in theirbloodstream for a prolonged period of time, thus causing ticks that feed on them to become infected. Then, when the infected tick feedson its next host, parasites are passed on to that host and the cycle of infection continues. Rodents, especially the white-footed mouse(Peromyscus leucopus), are the reservoir hosts for B. microti, while in Europe, cattle serve as the reservoir hosts for B. divergens.

Within the United States and Canada, human babesiosis does not appear to be geographically widespread. It is difficult to assess the trueprevalence of the disease because it has not been designated as a nationally reportable illness to the Centers for Disease Control and Prevention (CDC). Also, it is suspected that many cases go undiagnosed because of the lack of symptoms in many individuals. Sincethe first cases were recognized in California in 1966 (unknown Babesia species) and Massachusetts (Nantucket) in 1969 (Babesiamicroti), several hundred cases have been documented. The majority of these cases have occurred in southern New England, especiallyon the coastal islands of Massachusetts (Nantucket, Martha’s Vineyard), Rhode Island (Block Island), and New York (Shelter Island,Long Island). Cases have also been reported in California, Connecticut, Missouri, New Jersey, Washington, and Wisconsin.

Based on serologic (blood) studies, most infections appear to be asymptomatic. Manifestations of symptomatic disease includefever, headache, chills, sweating, muscle aches (myalgias), fatigue, nausea, vomiting, enlarged spleen and liver (sometimes resulting injaundice), and hemolytic anemia (anemia due to the destruction of red blood cells). Symptoms usually occur 1 to 4 weeks following a tick bite, and can last for several days, weeks, or months. The disease is more severe, and sometimes fatal, in patients who areimmunosuppressed (have a weakened immune system), lack a healthy spleen, or who are elderly. In some cases, parasites maycontinue to circulate in the blood of asymptomatic individuals for several months or even years, making transmission of babesiosis byblood transfusion a concern. Because there have been documented cases of transfusion-acquired babesiosis, the American Red Crossdoes not accept blood donations from anyone who has ever had babesiosis, even if they have been treated with appropriate antibiotics.

Co-infection with Lyme disease has been documented in some patients. Co-infection may complicate diagnosis and treatment, and mayresult in more severe illness in the individual.

Most patients do not remember a tick bite. Diagnosis is usually made by examining blood smears under a microscope and detectingBabesia within the red blood cells. Babesia appear as tetrad (cross-shaped) or ring-shaped forms, but may be very difficult todistinguish from the Plasmodium parasites that cause malaria. Therefore, a combination of diagnostic criteria may be useful. Anindirect immunofluorescent antibody assay (IFA) test can be used to detect Babesia-specific antibodies in the blood. Serologicdiagnosis is established by a four-fold or greater rise in the serum titer between the acute (early) phase and the convalescent (late) stage.In addition, patient blood can be inoculated into hamsters to observe resultant infection in these animals after 2 to 4 weeks. In somecases, polymerase chain reaction (PCR) may also be used to detect Babesia DNA in the blood. Because some patients may be coinfectedwith Lyme disease (10-25%), blood tests should also be performed for this infection. It is important to diagnose and treat bothinfections.

There are no standardized treatments for babesiosis. However, the following drug regimens have been found to be useful: quinine(650 mg 3 times/day) plus clindamycin (600 mg 3 times/day or 1.2 g intravenously 2 times/ day) for 7-10 days (the dosages for childrenare quinine 25mg/kg plus clindamycin 20-40 mg/kg, both given in 3 divided oral doses for 7 days), OR azithromycin (600 mg 1time/day) plus atovaquone (750 mg 2 times/day) for 7-10 days (the dosages for children are azithromycin 12 mg/kg 1 time/day plusatovaquone 20 mg/kg 2 times/day, for 7-10 days). Although all of these drugs are approved, the U.S. Food and Drug Administration

currently considers clindamycin, azithromycin, and atovaquone investigational for babesiosis. Patients who exhibit only mild symptomsmay require no specific therapy. Severely ill patients with a high percentage of infected red blood cells, on the other hand, may benefitfrom exchange transfusion (removal of the patient’s infected blood, followed by replacement with clean, donated blood). Dialysis maybe required for patients with kidney failure.

Rickettsial – Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF) is a serious tick-borne illness that is caused by the bacterialorganism Rickettsia rickettsii. You can get RMSF if you are bitten by a tick that is infected with Rickettsia rickettsii. Bacteria in the tick’s saliva are transmitted to you while the tick is feeding. An infected tick must be attached to you for at least several hours in order for transmission to take place.

Only certain species of ticks are capable of transmitting Rickettsia rickettsii. There are two major vectors (transmitters) of R. rickettsii to humans in the United States, the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni). The American dog tick is responsible for transmitting the majority of RMSF cases. This tick is widely distributed throughout the eastern two-thirds of the U.S., as well as in limited areas along the Pacific Coast. The Rocky Mountain wood tick is only found in the western U.S. Both tick species are very similar in appearance.

According to the Centers for Disease Control and Prevention (CDC), approximately 500 cases of RMSF have been reported annually in the United States since 1990. Although the disease was first recognized in 1896 in Idaho, and was a serious illness in the Rocky Mountain states in the early 1900s, it soon became apparent that RMSF is widely distributed throughout most of the United States. Today, the majority of cases occur in the southeastern seaboard and south central states. North Carolina and Oklahoma report the highest incidences of RMSF. R. rickettsii only exists in the western hemisphere, and outside of the U.S., RMSF has been documented in southern Canada, Central America, Mexico, and parts of South America. Closely related organisms cause other types of spotted fever illnesses in other parts of the world.

Prior to the discovery of tetracycline and chloramphenicol antibiotics in the late 1940s, approximately 30% of persons infected with R. rickettsii died. Today, despite modern advances in medical care and the availability of effective drug treatments, the disease still has a fatality rate of 3% to 5%. Severe or fatal illness is linked to advanced age, male gender, African-American race, chronic alcohol abuse, and glucose-6-phosphate dehydrogenase (G6PD) deficiency (a sex-linked condition affecting approximately 12% of the U.S. African-American male population). The majority of patients with RMSF must be hospitalized.

Following an incubation period of 5-10 days after a tick bite, symptoms usually begin suddenly and quickly worsen. Initial symptoms can include moderate to high fever, severe headache, nausea, vomiting, muscle pain, chills, and extreme exhaustion. Within 2-5 days after the onset of fever, a red spotted rash often appears, first on the extremities (wrists, forearms, ankles, soles and palms), and then quickly spreads to cover much of the body, including the face. Abdominal pain, diarrhea, and joint pain may also develop. Since R. rickettsii invade and cause the death of cells that line blood vessels throughout the body, blood leaks through tiny holes in the vessel walls into adjacent tissues.This is the process that causes the rash associated with RMSF, and which can also result in severe damage to the heart, lungs, brain, kidneys, and other major organs and organ systems. Absence, delayed appearance, or failure to detect the typical rash, especially in dark-skinned individuals, and difficulty in distinguishing this illness from otherinfectious and non-infectious conditions, may contribute to more severe illness due to delayed diagnosis and treatment.

There is no widely available laboratory test that provides rapid confirmation of early RMSF. Therefore, treatment decisions should be based on symptoms and should never be delayed while waiting for confirmation by laboratory results. Epidemiological clues may strengthen an early decision to administer antibiotics (e.g. history of tick bite, residence in/travel to an area where RMSF is present, or recent activity in tick habitat, etc.). A blood test known as an indirect immunofluorescence assay (IFA) is the standard test generally used by the Centers for Disease Control and Prevention (CDC) and most state public health laboratories. Blood samples taken early (acute) and late (convalescent) are necessary in order to demonstrate a fourfold rise in antibody level (titer) to R. ricketsii. Other blood findings suggestive of RMSF may include low platelet count, low sodium level, elevated liver enzyme levels, and normal white blood cell count.