Ticks Overview Gary Podolsky MD

Ticks are the leading carriers of diseases to humans worldwide, second only to mosquitoes. It is not the tick bite but the toxins or organisms in the tick's saliva transmitted through the bite that cause disease.

Ticks like spiders are arthropods. All tick species have a similar life cycle consisting of four stages: egg, larva (six legs), nymph (eight legs, sexually immature), and adult.

There are more than 800 species of ticks throughout the world. They are responsible for carrying such diseases as Rocky Mountain spotted fever, Lyme's disease, Babeosis (Texas fever), Ehrlichosis, and Tularemia (also transmitted via rabbits), as well as Colorado tick fever and Crimean-Congo Hemorrhagic fever.

In addition to disease transmission, ticks can also cause tick paralysis. This condition occurs when neurotoxins in the tick saliva make you ill; cause paralysis of the body; and in extreme cases, can stop you from breathing in extreme cases.

Tick Biology (What makes Ticks, tick?)

Ticks require blood meals at larval, nymph, and adult stages. If all three feeding stages occur on one host, the tick is referred to as a “one-host” tick. Most Ixodidae are “three-host” ticks—each feeding stage is on a different host. Some ticks are host specific, but most are opportunists and feed on a variety of hosts.

Ticks act as amplifiers or reservoirs for infectious agents. Ticks ingest microorganisms while feeding on an infected host. The organisms replicate in the tick and are carried to the adult tick stage from which they are transmitted to other hosts when the tick feeds. Microorganisms are passed transovarially from one generation of ticks to the next, and depend solely on the tick to survive.

Some major organisms vectored by ticks are borrelia, rickettsia, tularemia, viruses, and protozoan parasites. Ticks may also secrete a neurotoxin that produces tick paralysis.

Ticks are divided into two categories: Ixodidae (hard ticks) and Argasidae (soft ticks).

Ticks are important to humans because of the diseases they can transmit. Understanding the biology of the insect is key to anticipating and preventing diseases.

Hard Ticks (Ixodidae)

Have a hard, shield-like scutum that covers the entire dorsal surface in males but only the anteromedial portion of the females. The head is visible from above and below.

These feed slowly over the course of days. Females may ingest over fifty times their body weight in blood and other fluids.

Hard ticks transmit all of the major tick-borne disease in North America with the exception of relapsing fever.

Disease transmission usually occurs near the end of a meal, as the tick becomes full of blood. Some of the more common hard ticks are: American dog tick; Wood tick; Deer tick (they carry Lyme's disease)and Lone star tick

Soft Ticks (Argasidae)

Soft ticks have more rounded bodies without the hard scutum found in hard ticks. These ticks usually feed for less than 1 hour. Disease transmission can occur in less than a minute. The bite of some of these ticks produces intensely painful reactions. Two common soft ticks found in the United States are the Pajaroello tick and spinose ear tick. Transmit relapsing fever

Outbreaks of tick-related illnesses follow seasonal patterns as ticks evolve from larvae to adults. They hide in low brush to hitch a ride on a potential host. Ticks require a "blood meal" to grow and survive, and they are not very particular upon whom or what they feed. If these freeloaders don't find a host, they may die.

Once a tick finds a host (animal or person) and a suitable site for attachment, the tick begins to burrow with its mouthparts barbed into exposed skin.

Tick attachment and feeding

Ticks secrete "cementum" to more firmly anchor their mouthparts and head to their host. Ticks may secrete or regurgitate small amounts of saliva that contain neurotoxins. These nerve poisons prevent pain and irritation of the bite

Saliva may contain an anticoagulant.

Diseases of Ticks

Babesiosis (Human Babesiosis)

Is caused by a tick borne protozoan infection Babesia microti . After an infected nymph bites a human, the organisms enter the host's red cells, where they multiply and cause hemolysis.

Rodents, wild animals and cattle are its natural reservoir, with humans rarely infected. Symptoms start 1-4 weeks after bit and may be mild to severe. In severe cases - high fever, chills, nausea and vomiting, may even mimic malaria with future complications such as lung edema, anemia, kidney failure and bleeding.

Clinical signs of infection vary considerably; many patients remain asymptomatic.

Symptoms usually appear one to four weeks following a tick bite and at first consist of the gradual onset of malaise, anorexia, and fatigue. Within a week or so, fever that ranges from 37.8 ° to 40.3 ° C (100 ° to 104 ° F) drenching sweats, and myalgia develop.

As with malaria, nausea, vomiting, headache, shaking chills, hemoglobinuria, altered mental status, disseminated intravascular coagulation, anemia with dyserythropoiesis, hypotension, respiratory distress, and renal insufficiency are common. Pulmonary edema is occasionally found, and splenomegaly may occur, but is rather atypical.

There parasites may be seen on a blood smear (as with malaria) and treatment may be supportive or if severe symptoms, several drugs are used. This A number of reports of single patients with concomitant Borrelia and Ehrlichia infection have appeared in the United States and in Canada.

In areas where all three infections are present, laboratory testing of patients with an established diagnosis for the other two infections would not be unreasonable. For patients with Lyme disease, a single thick blood smear could be examined for the morules that typify human granulocytic ehrlichiosis and for the intraerythrocytic parasites that characterize babesiosis. Immunofluorescent immunoassays or PCR testing would be more sensitive procedures. disease often co-exists with Lyme disease in the same ticks, although it is rare.

Patients with only mild clinical manifestations of babesios may require no specific treatment. For those who do need treatment, quinine combined with clindamycin is the treatment of choice. Parasitemia is consistently eradicated and babesial infestation does not recur when treatment is discontinued

Colorado Tick Fever

Colorado tick fever is the most common human arbovirus infection. It is transmitted exclusively by female wood ticks ( Dermacentor andersoni ) in North America.

The distribution of Colorado tick fever virus roughly approximates that of its vector tick, D andersoni . The virus has been isolated from humans and from ticks in California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, and Wyoming, and also in southern Alberta and British Columbia. Physicians should be aware of the possibility of Colorado tick fever in febrile patients returning from these regions.

Mammals involved in the natural cycle of Colorado tick fever virus include the golden mantled ground squirrel, porcupine, chipmunk, deer mouse, and bushy-tailed woodrat. Colorado tick fever virus also is transovarially (adult female to egg) and transstadially (larva to nymph to adult) transmitted in D andersoni ticks.

People with recreational or occupational exposure to ticks in the period April through June have a higher incidence of infection. Males in general, and people aged 20 to 29 had the highest risk of acquiring the disease.

The incubation period ranges from less than one to nineteen days (average, about four days), possibly dependent on the number of colorado tick fever virions the individual receives from the infecting tick. The onset is usually abrupt and is characterized by high fever, chills, joint and muscle pains, severe headache, ocular pain, conjunctival injection, nausea, and occasional vomiting. The spleen and liver may be palpable. A transitory petechial or maculopapular rash is seen in a few individuals.

No specific signs or symptoms, physical findings, laboratory abnormalities, radiographic or electroencephalographic features define Colorado tick fever. However, the diagnosis of Colorado tick fever is strongly suggested if the illness is interrupted by an afebrile, symptom-free interval that lasts two to three days. Fifty percent of the individuals with clinical illness manifest this interval.

A history of travel to an endemic area suggests the diagnosis. Ninety percent of infected individuals recall having had a tick attached or having seen a tick crawling on their body or clothing.

Colorado tick fever is rarely a life-threatening illness, but may cause severe discomfort, and symptoms may last for weeks. Treatment is symptomatic.

A few individuals have a more severe illness that produces extended prostration, anorexia, continuing fatigue, and convalescence for several more weeks. Children may have hemorrhagic manifestations ranging from a more pronounced rash to a disseminated intravascular coagulopathy and gastrointestinal bleeding. Central nervous system involvement, including aseptic meningitis and encephalitis, has been observed in severely affected children. Rarely, adult orchitis, pericarditis, hepatitis, and symptoms mimicking myocardial infarction have been reported.

Because the illness is relatively mild, extensive diagnostic studies are not usually performed. Leukopenia and, in some instances, thrombocytopenia have been observed, as has toxic granulation of neutrophils. Immature granulocytes may appear in the peripheral blood..

Serologic conversion from a negative, or low titer to a positive or high titer is most often used for confirmatory diagnosis. However, antibody to Colorado tick fever virus is not detected until one or two weeks after the onset. IgM antibody to Colorado tick fever virus does not cross-react with any other North American virus, so that detecting such antibody, even in a single serum, can be considered presumptive evidence of recent infection

Isolating Colorado tick fever virus from the patient is a more dependable basis for laboratory confirmation. Colorado tick fever virus replicates in erythrocytes and is sequestered from antibodies. Viremia may last for several months. Early in the infection, virus can be isolated from both serum and blood clots with about the same frequency, but about a month after onset it is more easily isolated from blood clots.

Crimean Congo Hemorrhagic Fever

Occurs in Africa, Asia, and the Middle East. It is common in many animals but rare, yet serious in people.

It is caused by a virus transmitted by infected ticks or by direct contact with infected animal body fluids. There is no vaccine. Risk to travellers in low. Symptoms start after an incubation period of 1-3 days. Non-specific symptoms like fever, dizziness, headache, neck stiffness; aches, abdominal pain, diarrhea, nausea, sore eyes and photophobia develop. Generalized bleeding can develop. Diagnosis is confirmed with a blood test. Treatment is supportive only.

Ehrlichiosis (Human Erlichoiosis)

Ehrlichiosis is a bacterial infection transmitted by tick bites.

Symptoms are similar to Rocky Mountain spotted fever and Lyme disease. Onset of symptoms occurs 5-10 days after the tick bite with sudden fever, headache, chills, aches and nausea and vomiting. A generalized rash occurs more often in affected children compared to adults. Untreated meningitis, kidney and liver disease may occur, and rarely it is fatal.

Diagnosis is with blood tests, which may take some time. Doxycycline is effective treatment (which will also cover Rocky Mountain Spotted Fever and Lyme disease), while waiting for confirmation of blood work.

The ehrlichia are obligate intracellular bacteria that infect a variety of animals and are usually vectored by ticks.

The first case of human ehrlichiosis in the United States occurred in 1986, and was reported in 1987. Because the organism produces characteristic colonies (morules) in monocytes, the disease was labeled human monocytic ehrlichiosis (HME).

The first case of human granulocytic ehrlichiosis (HGE), so-called because the organisms form morules in granulocytes instead of monocytes, was reported in 1995. (Both organisms will infect stem cells, but maturation into mature cells select against the specific organisms.)

The clinical courses of infections by either organism are quite similar. Typically the first manifestation is an acute febrile illness associated with headache and myalgia. Approximately 75 percent of patients have a history of tick exposure. Laboratory studies usually disclose leukopenia and thrombocytopenia, sometimes anemia, and hepatic aminotransferases are usually elevated. A nonspecific rash occurs in approximately one-third of the patients with HME, but is less common in patients with HE.

The diagnosis is aided by finding typical organisms in peripheral blood smears, but typical morules are found in only about 80 percent of serologically confirmed infections. Infections are most often diagnosed by immunofluorescence assay (IFA), although polymerase chain reaction (PCR) assays are being used more commonly.

Most patients have a mild illness that rapidly responds to Doxycycline (100 mg BID). Defervesence usually occurs in twenty-four to forty-eight hours.

Some older patients, have adult respiratory distress syndrome (ARDS), renal failure, neurologic disorders, and disseminated intravascular coagulation (DIC).

Case-fatality ratios as high as 10 percent for HGE and 5 percent for HME have been reported.

The white-footed mouse (or deer mouse, Peromyscus leucopus) is a significant animal reservoir for the agent associated with HGE

US Army centre for health promotion and preventative medicine

http://chppm-www.apgea.army.mil/ento/erlichio.htm

CDC http://www.cdc.gov/ncidod/dvrd/ehrlichia/

Familydoctor.org http://familydoctor.org/056.xml

Lyme's Disease

Lyme Disease is an infection by the spirochete Borrelia burgdorferi that is associated with variable, complex clinical features. It is transmitted by the bite of Ixodes ticks

Lyme Disease was first recognized after two women called the Connecticut State Health Department's attention to an incidence of juvenile rheumatoid arthritis at least 100 times higher than expected in the vicinity of Lyme, CT, in 1975.

A history of a tick bite from a few patients, close geographic clustering, and a predominant onset in summer or early fall led to suspicion of an arthropod vectored infection. The distribution of subsequent cases was similar to that of the deer tick Ixodes dammini (now named Ixodes scapularis ).

Spirochetes were found in the midguts of the ticks by Willy Burgdorfer, thus the name Borrelia burgdorferi .

Subsequently, organisms were recovered from the blood of patients with typical Lyme disease at State University of New York.

The name was changed from Lyme arthritis to Lyme disease, and the disorder was recognized to be identical to a syndrome long known in Europe. Buchwald described the skin lesions known as dermatitis chronica atrophicans in 1883.

Afzelius described erythema chronicum migrans, the typical erythematous rash, in 1921. Spirochetes were found in the skin lesions in 1948, and reports of benefits from penicillin therapy appeared in 1951, 1955, and 1958. Benign lymphocytic infiltration of the skin was reported in 1953. Garin and Bujadoux described the neurologic features in 1922, and the condition has been known in Europe as Barnwarth's syndrome since his 1941 report.

Lyme disease has been reported from at least forty-four states in the United States, including some states in which the tick vectors are not known to exist, and is widespread in Europe, Asia, and Australia. When CDC surveillance started in 1982, only about 500 cases were reported. The incidence has increased steadily. In 2002, 23,763 cases of Lyme disease were reported, and total reported cases is over 157,000. (Approximately 60,000 infections occur each year in Europe.) Some of these cases are undoubtedly erroneous diagnoses, but CDC considers Lyme disease under reported. The overall incidence rate in 2002 was seven infections per 100,000 population.

In the Northeast and Midwest, most cases occur from May to August; in the Pacific region, the incidence is evenly distributed throughout the year. In the Northeast and Midwest have the highest incidence in individuals younger than 15 years; the second highest incidence is in the 25 to 44 year age group, which reflects peridomestic exposure. In California the highest incidence is in the 25 to 44 year age group, which reflects recreational or occupational exposure.

In Canada, the greatest number of confirmed cases (199) has been in Ontario; while no confirmed cases have been reported in Newfoundland, Prince Edward Island, Nova Scotia, the Yukon and the Northwest Territories. http://www.arthritis.ca/types%20of%20arthritis/lyme%20disease/default.asp?s=1
According to the Canadian Lyme Disease Foundation, Lyme disease carrying ticks have been found in every Canadian Province. Ixodes scapularis have been found as far north and west as Slave Lake Alberta. http://www.canlyme.com/
Lyme disease is transmitted largely by Ixodes ticks, Ixodes scapularis in New England and the Midwest, I. pacificus in California, I. ricinus in Europe, I. persulcatus in China.

Ixodes ticks are much smaller than common dog ticks. The nymphs, which are responsible for most human bites, are smaller than the adults — about the size of a poppy seed. As a rule of thumb, arthropods easily identified as ticks by individuals who are not familiar with the appearance of Ixodes ticks are not of that species.

After hatching, ticks go through three stages: larval, nymph, and adult.

Blood meals are required at all three stages and provide opportunities for infection. The larvae attach to mice and acquire the infection.

Nymphs attach to a wide variety of animals and transmit the infection.

Most human bites are by nymphs, which are small and usually undetected.

Only 30 percent of patients with Lyme disease can recall a tick bite.

Nymphs must remain attached for at least twenty-four hours and possibly 48 hours to transmit infection.

Infection rates approach 100 percent only after more than 100 hours attachment.

Adult ticks usually attach to deer. Eliminating the deer population greatly reduces the incidence of Lyme disease.

The white-footed mouse, Peromyscus leukopus , is the most significant host for Lyme disease spirochetes in the Northeastern and north central regions, and provides the reservoir for infection. (Wild animals usually are not affected by the organisms

The clinical aspects of Lyme disease are divided into three stages or phases.

In stage one, the acute localized phase , which is characterized by the typical skin rash, the organisms are limited to the area in which the tick bite occurred.

In stage two, the acute disseminated phase , the organisms are spread throughout the body and produce widespread skin lesions as well as cardiac and neurologic disorders. Stage three, the chronic disseminated phase, is characterized by arthritis.

The typical skin rash of Lyme disease is a single red plaque that has been named, Erythema Chronicum Migrans , or ECM. This plaque usually appears 2-14 d (range: 3-21d) after the tick (nymph) bite.

It starts as a red papule or macule and expands outwardly, often with central clearing. The ultimate diameter is usually 5 to 20 cm but these lesions range from 3 to 68. Usually the plaque is asymptomatic except for its appearance, minor burning, itching, or pain may be present.

The plaque appears at the site of bites, which usually is where clothing, such as underwear on the thigh, groin or the axilla, or a belt at the waist, stopped the tick's progress.

The plaque does not vesiculate, which helps distinguish it from erythema multiforme. If the patient receives no treatment (antibiotics) the plaque fades after four weeks (range: 1 to 14 weeks).

With treatment, it disappears more rapidly. The rash occurs in over 80 percent of infected individuals, and possibly more, particularly individuals who are aware of the possibility of infection and are watching for a plaque.

A flu-like syndrome typically accompanies the skin lesions, and is characterized by malaise, fatigue, a low-grade intermittent fever, arthralgias and myalgias. Tender lymphadenopathy is often present near the ECM.

Serology is usually nonreactive at the time ECM appears, but often becomes positive while the lesion is present.

IgM antibodies appear first; IgG appears later.

Organisms can be cultured from the leading edge of ECM lesions, the only site where organisms can be found with significant frequency. Special culture media is required; few laboratories outside endemic areas stock that media.

The second stage begins 4 wks (Range: 0-10 wks) after ECM appears, but often overlaps the first and third stages.

Manycharacteristic yndromes affecting different systems are described:

Multiple skin lesions termed secondary ECM appear in 10 to 15 percent (as high as 50 percent in some studies) of untreated patients. The secondary skin lesions are smaller than the primary and migrate less. They can be located anywhere, and number from twenty to over one hundred.

Nervous system infection occurs in 15 to 20 percent of untreated patients:

Peripheral nervous system involvement is most common and is characterized by radicular pain most often in the limb that was the site of the bite.

Meningoencephalitis ("Aseptic Meningitis") appears in 8 to 15 percent of untreated individuals and is characterized by a fluctuating headache, photophobia, and meningismus. The cerebrospinal fluid may contain leukocytes (10–100/mm 3 ) and increased protein. Organisms are rarely cultured from the CSF.

Subarachnoid Nerve Root Inflammation . Facial nerve palsy is most common and is often bilateral. It lasts from weeks to months, but recovery is usually complete. Other cranial nerves that may be involved: III, IV, and VI are involved more often than V and VIII, which are involved more often than IX through XII.

Chronic Confusional State may interfere with daily cognitive function and memory. It is seen with "some frequency," but more precise incidence data apparently is unavailable. The cerebrospinal fluid, CT and MR scans, and neurologic examination often are completely normal. Only detailed neuropsychological testing discloses cognitive defects, and these are usually reversible with antibiotic therapy.

Multifocal leukoencephalitis resembling multiple sclerosis is extremely uncommon. It may be acute and fulminant or slowly progressive.

Cardiac abnormalities appear in 4 to 8 percent of untreated infected persons. EKG evidence of myocarditis or pericarditis is present in 60 percent. Mild left ventricular dysfunction occurs in half, but congestive heart failure is infrequent. Conduction defects are common, and atrioventricular (AV) block—first to third degree—is most frequent. Hospitalisation is usually required for monitoring, and some patients require transvenous pacing. The cardiac abnormalities usually resolve completely, but three of the four reported deaths resulting from Lyme disease have been caused by cardiac involvement. (The fourth resulted from ARDS.)

Arthritis is common and occurs in 60 percent of untreated patients. It begins up to two years after onset, and is characterized by recurrent, asymmetric, oligoarticular pain and swelling.

Only one joint at a time is involved, but as many as ten joints can be involved at once. The median duration of the arthritic episodes is eight days.

The frequency of joint involvement is: Knee > Shoulder > Elbow > TMJ > Ankle > Wrist > Hip > Hands and Feet.

The diagnosis of Lyme disease is based primarily on clinical findings, and treating patients with early disease solely on the basis of objective signs and a known exposure is appropriate.

B burgdorferi can be cultured from 80 percent or more of biopsy specimens taken from early erythema migrans lesions. However, the diagnostic usefulness of this procedure is limited because of the need for a special bacteriologic medium (modified Barbour-Stoenner-Kelly medium) and protracted observation of cultures.

When serologic testing is indicated, CDC recommends testing initially with a sensitive first test, either an enzyme-linked immunosorbent assay (ELISA) or an indirect fluorescent antibody (IFA) procedure, followed by testing with the more specific Western immunoblot (WB) test to corroborate equivocal or positive results with the first test. Antibodies often persist for months or years following successfully treated or untreated infection. Seroreactivity alone cannot be used as a marker of active disease.

Neither positive serologic test results nor a history of previous Lyme disease assures that an individual has protective immunity. Repeated infection has been documented.

Treatment of Lyme Disease

Treatment of early stage disease (ECM or secondary skin lesions) is almost always successful and stops progression of lesions and prevents development of subsequent disorders.

Doxycycline, except in pregnant patients, or amoxicillin are the antibiotics of choice.

Treatment for arthritis consists of oral or intravenous antimicrobials given for much longer periods. The success rate is much lower—apparently 30 to 60 percent.

Controversies: Chronic Lyme disorder or “Post Lyme Syndrome”

According to a recent report 20 percent of the individuals with a typical erythema migrans skin lesion will get well and have no further problems without any treatment.

Of those treated at this early stage, over 90 percent develop no subsequent evidence of Lyme disease.

Lyme disease ranks behind only AIDS in media coverage and may be greatly overdiagnosed. Only 20 percent of the patients referred to Allen Steere's Lyme disease clinic at New England Medical Center actually have the disease.

Alternative views of diagnostic criteria and treatment strategies have been presented by patient advocacy groups and in newsletters devoted to Lyme disease.

Steere has stated in publications that the chronic fatigue syndrome and fibromyalgia are not part of the spectrum of Lyme disease. This disabling syndrome is similar to chronic fatigue syndrome or fibromyalgia.

Persistent complaints are generally non-specific and include arthralgias, myalgias, cognitive difficulties, fatigue, malaise, dizziness, stiff neck and photophobia.

Some patients are totally disabled. Such persistent disability is most common in individuals who have not been treated in the early stages of their infection. In some the treatment has been delayed for almost a year. Additional patients have had symptoms of early dissemination of the infection to the nervous system.

Does chronic Lyme disease really exist? If so, how should it be treated? At the present time no definite answer can be given and cases should be referred to an Infectious Disease specialist. General treatments for chronic pain should be utilized.

Lyme disease Prevention

A successful Lyme disease vaccine for humans was developed. But the vaccine was expensive and recommendations for its use by the Advisory Committee for Immunization Practices would have limited it to approximately 1 percent of the population. Some concern about its safety apparently existed also, although the available data on outcomes did not support these concerns. Sales of the Lyme vaccine for humans were so small that the product was withdrawn from the market in February 2002.

A Lyme disease vaccine for dogs has been available since 1990. This vaccine, a chemically inactivated, whole-cell preparation of B. burgdorferi formulated with a polymer-based adjuvant, is not considered suitable for humans because it may induce immunopathology through cross-reactions with human antigen

The current status of prophylactic antibiotics is unresolved, but the administration of a single 200 mg oral dose of doxycycline following the discovery of an attached and engorged tick—not just an attached tick—appears reasonable.

Mediterranean spotted fever

Mediterranean spotted fever is also known as Marseille fever, South African tick bite fever, Kenya tick bite fever, India tick typhus, and Boutonneuse fever. It is endemic in the Mediterranean and is caused by Rickettsii conorii. The major vector is the dog tick Rhipicephalus sanguineus.

As so all spotted fevers, it usually occurs during warm weather months. Infections are usually mild in children and young adults. Individuals at greatest risk are the elderly, alcoholics, and individuals with glucose-6-phosphodehydrogenase (G-6-PD) deficiency.

Tick-borne encephalitis

(TBE) is caused by members of the flavivirus family that can affect the central nervous system. Although TBE is most commonly recognised as a meningo-encephalitis, mild febrile illnesses can also occur.

TBE is transmitted to humans by the bite of an infected tick or, less commonly, by ingestion of unpasteurised milk from infected animals, especially goats

The virus is maintained in nature by small mammals, domestic livestock and certain species of birds.

Men tend to be infected than women and most of these infections are caused by leisure activity such as hiking and walking.

Incidence peaks in spring and early summer, but can occur throughout the year

incubation period is from two to 28 days

Tick activity starts when soil temperature rises to 5-70 degrees C in March or April and ends in fall. In Mediterranean countries ticks are more active November-January. Ticks are worse in wet summers and mild winters.

The risk of infection from specific tick bites ranges from 1:200-1:900. People at highest risk of being bitten include agriculture/forestry workers, hikers/ outdoorsmen and collectors of berries and mushrooms. These ticks attach to humans at hair-covered portions of the scalp, ears, arms, knee joints, and hands and feet.

TBE occurs in most or parts of Austria, Germany, southern and central Sweden, Hungary, France (Alsace region), Switzerland, Norway, Denmark, Poland, Croatia, Albania, the Baltic states (Estonia, Latvia and Lithuania), the Czech and Slovak Republics, Hungary, Russia (including Siberia), Ukraine, some other countries of the former Soviet Union, and northern and eastern regions of China.

There are three versions of the disease related to the virus subtypes, namely European, Far Eastern and Siberian types.

European version biphasic with an initial viremic phase of fever and influenza-like symptoms followed in some cases (after an afebrile period of one to 20 days) by central nervous system involvement.

Case fatality rate of the European version is 1% .Long-lasting or permanent neuropsychiatric sequelae are observed in 10–20% of affected patients.

Far Eastern version has a more gradual in onset and normally takes a more severe and longer course with a reported mortality of 5–20%.

Prevention is by wearing appropriate clothing, removing ticks before they start feeding, immunisation (Austria has vaccinated its population and has lower incidence than neighbouring Czech Republic).

Unvaccinated individuals bitten by ticks in endemic areas should seek local medical advice

Unpasteurised milk should not be drunk. The vaccine is recommended particularly for spring and summer travel in warm, forested parts of the endemic areas, when ticks are most prevalent.

Tourists who hike, camp, hunt and undertake fieldwork in endemic forested areas should be vaccinated

TBE vaccine is recommended for those who will be going to reside in an area where TBE is endemic or epidemic and particularly those working in forestry, woodcutting, farming and the military.

Relapsing Fever

Relapsing fever is a bacterial illness called so because of the unresolved recurrent fever in untreated people. There are two types:

Louse-borne variety is found in areas of poverty with epidemic occurring after natural disasters. They live and proliferate in the clothing.

The tick-borne variety is found in Africa, Southern Europe, Middle East, Asia, Western U.S.A. and Canada.

Tick Borne Relapsing Fever

Borreliae, which belong to the order of Spirochaetales, are helical, actively motile spirochetes. Strains are not classified by morphology, but by specificity of the tick­spirochete relationship, the range of animals susceptible to infection, and cross ­immunity. Human Borrelia infections occur almost worldwide and produce epidemic relapsing fever (louse-borne), endemic relapsing fever (tick-borne), and Lyme disease.

Borrelia recurrentis , the organism that causes tick-borne relapsing fever is transmitted to humans by several species of soft ticks (Argasidae) in the genus Ornithodoros. (Louse-borne relapsing fever also is caused by Borrelia recurrentis , but is called epidemic relapsing fever.) They are leathery, wrinkled, or granular organisms, often gray in color, that live in deserts or under dry conditions in wet climates, hiding in crevices in buildings such as huts, log cabins, cattle barns, and uninhabited houses, or burrowing into loose soil.

Soft ticks are adapted for feeding rapidly and leaving promptly; they are rarely found on a host. Since soft ticks generally feed for only a short period (thirty minutes or so), the subject may be unaware of any recent tick bites. They can survive many years without a blood meal.

Rodents and other mammals serve as a natural source of infection for the ticks. The infection is transmitted by the tick bite (saliva), and also sometimes by contamination of the bite wound with infective fluid produced by feeding ticks just before they detach. Transtadial and transovarial transmission of the agent occurs readily; thus, the ticks also are reservoirs of infection.

Relapsing fever is endemic across central Asia, most of Africa, parts of the Middle East, and North and South America. Worldwide, several hundred cases are reported each year. Approximately thirty to fifty cases occur annually in the United States, primarily in Oregon, Washington, and northern California.

Geographic foci of tick-borne relapsing fever infection are restricted to Ornithodoros-infested areas. Known vectors of tick-borne relapsing fever in the western United States include Ornithodoros hermsi, Ornithodoros parkeri, and Ornithodoros turicata. O hermsi is a rodent parasite widespread in the Rocky Mountain and Pacific Coast states. Often found in crevices of vacation or summer cabins. O. turicatais is found in southwestern United States, extending southward into Mexico.

These species are often found in burrows used by rodents or burrowing owls.

In Central and South America, Ornithodoros rudis is considered the most important vector. It feeds on domestic birds and humans. In Africa, Ornithodoros moubata and Ornithodoros erraticus are proven vectors. O moubatafeeds on humans, warthogs, domestic pigs, antbears, and porcupines. It is often found in cracks in walls, and in earthen floors of huts.

Tick-borne relapsing fever is characterized by bouts of fever that alternate with afebrile periods. The onset is usually sudden and is characterized by fever that often is higher than 39ºC . Often accompanying the fever are shaking chills, severe headache, myalgias, arthralgias, nausea and vomiting, muscular weakness, and lethargy. A transitory petechial rash is common during the initial attack. In some cases, meningeal inflammation and peripheral facial palsy have occurred.

In untreated patients, the fever ends in an average of three days (range one to seventeen), an event accompanied by sweats and intense thirst. An average of six to seven days later, but with a considerable range, the fever reappears.

Three relapses is the average, but as many as ten or more can occur. The relapses tend to be progressively less severe.

The relapsing nature of this illness appears to be related to antigenic variation. As an immune response develops to the predominant spirochetal antigenic strain, variant strains multiply and cause a recrudescent infection.

Diagnosis requires a high index of suspicion. After an incubation period of about eight days (range, five to fifteen), individuals with tick-borne relapsing fever may not associate the illness with a visit to a park or similar location where ticks are encountered. Identifying the spirochetes in thick or thin blood films, or dark field preparations of fresh blood usually makes the diagnosis.

Laboratory findings may include neutrophilic pleocytosis of the cerebrospinal fluid, peripheral leukocytosis, thrombocytopenia, and hypophosphatemia.

Serologic testing for tick-borne relapsing fever can be carried out with an enzyme-linked immunosorbent assay. This procedure is not widely available.

When tick-borne relapsing fever is untreated, the mortality rate is between 2 and 10 percent, mostly in infants..

Tetracyclines are effective against tick-borne relapsing fever. Oral tetracycline taken for seven days has been reported successful.

Prevention of relapsing fever consists of avoiding tick-infested areas or, when this is not possible, reducing the possibility of tick bites with repellents or insecticides. Additional measures include fumigating rodent nesting sites in human habitations, rodent-proofing buildings in areas where the ticks are endemic, and eliminating rodent access to unnatural food sources

Q Fever

Q Fever is a worldwide zoonosis affecting domestic and wild animals caused by Coxiella burnetii . Tick to human transmission is rare.

The infection presents as a flu-like illness with fever, headache, myalgias and pneumonitis. Infected individuals may have abnormal liver function tests, jaundice, and hepatomegaly. The infection usually resolves in 2 to 4; tetracycline may shorten the course. Infections may become chronic and produce granulomatous hepatitis and culture negative endocarditis. Diagnosis is dependent upon serologic testing. Treatment for chronic disease is not always successful; Tetracycline may be needed for at least twelve months.
Rocky Mountain Spotted Fever

(Choix fever, new world spotted fever, Pink fever, Tick fever)

This is a tick-borne illness and usually affects 600-800 people per year in the United States, mostly in the southeast states (Oklahoma, Tennessee, the Carolinas, Georgia and Virginia). It is also in Central and South America.

The tick responsible is more active in spring and summer. Children between 5-9 years are most commonly bitten. One reason is that they are more likely to brush against tick carrying shrubbery and get bitten.

Rocky Mountain Spotted Fever is related to typhus and caused by a rickettsia (bacteria-like organism) transmitted by ticks (in the eastern U.S it is the deer tick, while in the western U.S it is the wood tick).

Symptoms of Rocky Mountain Spotted start 1-2 weeks after the tick bite and are usually sudden with high fever, chills, muscle aches, severe headache and vomiting. A crusted, raised, lump may be at the with lymph nodes swollen. The characteristic rash of Rocky Mountain spotted fever begins 1-10 days after the onset of fever.

Small red spots begin at the extremities (hands, feet, ankles) and spread centrally (towards the trunk) while usually sparing the face. With progression these rashes became purpuric (bleeding under the skin) so that they will not blanch with pressure. Complications of this disease can lead to brain, kidney, liver, lung failure, and death, if untreated. Treatment is with tetracycline or a suitable alternative.

Diagnosis is on history and collection of symptoms. Serologic tests take days to develop.

It is important to note that although this rash is typical, not all cases have the rash or it may be very faint or hard to see, so its absence does not rule out the disease. Prognosis related to speed of treatment so an antibiotic may be started without a specific diagnosis (many of the tick borne diseases have similar treatments).

Different types of rickettsia cause other “spotted fevers” and their name usually tells of their location.

Avoidance, diagnosis and treatment are similar to Rocky Mountain spotted fever, although the severity of symptoms can vary between them : -Mediterranean Spotted Fever,-Kenyan Tick Typhus,-African Tick Bite Fever,-Israeli Spotted Fever,-Astrakhan Fever (found in the Caspian sea), Siberian Tick Typhus, Indian Tick Typhus, Japanese Spotted Fever, Queensland Tick Typhus,and Flinders Island Spotted Fever (Australia.

Early intervention and treatment can reduce morbidity and mortality. Doxycycline (Tetracycline) is the drug of choice; chloramphenicol is an alternative, particularly for children and during pregnancy. Neither drug is rickettsicidal. Antibiotics inhibit the organism until the body can mount an immune response that eventually eradicates the organism.

The dose of doxycycline is 25 to 50 mg/kg/day orally in four divided doses with a maximun of 2gr/day for adults. Dosage for chloramphenicol is 50 to 75 mg/kg/day orally for adults and children. Treatment should continue until the individual has been afebrile for at least 48 hours, or a minimum of five to seven days. Relapses are uncommon but may be treated with the same medication.

Stari Southern Tick Associated Rash Illness (Master's disease)

In the late 1980's and 1990's, physicians in the southeastern and south central United States began to recognize individuals who developed a rash essentially identical to erythema migrans, the typical earliest stage of Lyme disease. This did not develop other manifestations of that infection. The rash was found to be associated with the bite of the lone star tick, Amblyomma americanum .

This simulator of Lyme disease has been named Southern Tick-Associated Rash illness (STAR Illness or STARI).

The typical clinical finding is a roughly circular erythematous rash centered on the site of the tick bite. Central clearing may be present. The rash is identical to erythema migrans.

Other symptoms that may be present include fatigue (50 percent), headache (43 percent), muscle stiffness including stiff neck (36 percent), and fever (29 percent). However, signs and symptoms of the second or third stages of Lyme disease do not ensue, even in patients who are not treated.

No specific laboratory studies are available. Spirochetes have been seen in lone star ticks with microscopy, and a spirochete has been detected by DNA analysis and given the name Borrelia lonestari .

Lone star ticks, Amblyomma americanum have a life cycle and ecologic requirements are similar to Ixodes ticks.

All three stages—larval, nymph, and adult—aggressively bite people. However, live spirochetes are observed in only 1 to 3 percent of these ticks. Pictures, including size comparisons, are available at ent.iastate.edu/imagegal/ticks

Individuals with the rash have been given a variety of antibiotics, most commonly doxycycline. The treatment has been successful, but the rash and other symptoms disappear without therapy.

Serologic testing for Lyme disease may be advisable. Until the results are received, doxycycline therapy, which is effective in the early stages of that infection, appears reasonable. However, Lyme disease is uncommon in most of the area where lone star ticks are found.

Tick Typhus

Tick Typhus is transmitted to humans by ixodid ticks. An eschar scar develops at the bite site and the rickettsia (small bacteria like organism) incubates for about 1 week. A fever develops with a maculopapular rash (which may be very small). This rash and eschar are very typical of tick typhus but often this illness is confused with malaria or a traveller's diarrhea infection. A headache is also noted.

Usually symptoms are mild but kidney, liver and neurological damage can occur.

Doxycycline is an effective treatment and doxycycline when given daily for the prevention of malaria will prevent typhus.

Infective ticks infest domestic and wild animals particularly dogs in cities. Walking in brush is risky. Preventative measures for ticks include wearing the trouser cuffs inside the socks, DEET use, sleeping on elevated cots and checking each other for ticks.

Epidemic typhus is more severe but rarer and is caused by human lice. It is seen in poverty stricken areas (Rwanda, Uganda, and Ethiopia). Travelers are unlikely to experience epidemic typhus even if backpacking.

North Asian Tick Typhus

North Asian tick typhus is also known as Siberian tick typhus. It is endemic in Siberia and is closely associated with steppe landscapes. The causative organism is Rickettsia siberica ; the vectors are several species of Dermacentor and Haemaphysalis ticks. Humans are accidental and dead-end hosts.

Queensland Tick Typhus

Queensland tick typhus is caused by Rickettsia australis , and is endemic in southern and northern Queensland. The vector is the scrub tick Ixodes holocyclus

Tick Typhus links

Masta http://www.masta.info/library/factsheets/tick_typhus_fact_sheet.pdf

CDC http://www.cdc.gov/ncidod/diseases/submenus/sub_typhus.htm

Tick Paralysis

Tick paralysis has been recognized since 1912, and involves humans and animals. This disorder is found world wide, but occurs most often in North America and Australia. The Pacific Northwest and Rocky Mountain areas account for most cases. At least forty-three species of ticks have been reported to cause tick paralysis.

Tick paralysis occurs during the spring and summer when ticks are feeding. Children are affected more often than adults, and girls are affected twice as often as boys, possibly because their long hair hides the tick. Men are affected more often than women, probably because they participate in activities that bring them into contact with ticks more frequently.

Tick paralysis is thought to be caused by an unidentified venom secreted by the tick salivary glands during a blood meal. The disorder first appears five to six days after attachment of the tick. The earliest symptoms are restlessness, irritability, and paresthesias in the hands and feet. Twenty-four to forty-eight hours later, an ascending, symmetric, flaccid paralysis with loss of deep tendon reflexes appears. Weakness typically is initially worse in the lower extremities .

Within one to two days, severe generalized weakness develops. Cerebellar dysfunction with ataxia and in coordination may appear. Dysfunction may progress to bulbar and respiratory paralysis. Isolated facial paralysis may occur in individuals with ticks imbedded behind the ear.

The paralysis resolves after removal of the tick, which establishes the diagnosis. In North America, recovery is usually rapid. It starts within hours and is complete within days. Other than removing the tick, no therapy other than supportive care is needed (or available). However, undiagnosed tick paralysis can be fatal.

Australian tick paralysis may continue to progress for 48 hours after the tick is removed, and total recovery is much more prolonged

Tularemia

The peak incidence is in the summer months, which correlates with the life cycle of the tick vectors, but infections also occur during the winter months in association with hunting. Over 75 percent of the infections are in men, generally in adults over the age of thirty.

Humans are highly susceptible to infection with the organism, which most commonly occurs through the bite of an arthropod. Infections follow bites by ticks, fleas, mites, and deer flies. Infection also is produced by contact with infected animals, most commonly rabbits, which can be reservoirs because they have a high natural resistance to the organism and become carriers. F tularensis infects hundreds of different vertebrates and invertebrates, but most either die or recover and eliminate the organisms. Just a few have a significant role in the transmission of infection to humans. In the United States, these include rabbits, voles, squirrels, muskrats, and beavers. (Less common routes of infection include aerosol droplets, contact with water, and animal bites.) Human-to-human spread does not occur.

Ticks are the most common vector in the United States, particularly in the central and Rocky Mountain states, where most infections occur. Biting flies are responsible for many infections in California, Nevada, and Utah. The most commonly infected ticks are the Lone Star tick ( Amblyomma americanum ), the dog tick ( Dermacentor variabilis ), and the wood tick ( Dermacentor andersoni ).

Hunters contact infected carcasses when skinning, dressing, and eating deer, rabbits, muskrats, beavers, squirrels, and birds. Domestic cats have transmitted the organism to humans, probably by transient colonization of the cat's mouth or claws after killing or feeding on infected prey. F tularensis can survive freezing for months, but thorough cooking of game should minimize the risk of transmission.

Francisella tularensis is a small, gram-negative coccobacillus. It is an intracellular organism and the immune response to it is dependent on cell-mediated mechanisms. The organism enters the body by a local lesion that can vary in location, resulting in different manifestations of the disease. The sites of inoculation include the skin, conjunctiva, oropharynx, respiratory tract, and occasionally, the gastrointestinal tract.

After the bite of an infected arthropod, the incubation period averages about three to five days, but the range can be anywhere from one to twenty-one days. After cutaneous inoculation, F tularensis multiplies at the local site and produces a papule. Ulceration follows two to four days later. At this point, organisms spread locally to regional lymph nodes and then may disseminate through the blood and lymphatics. Bacteremia is thought to be common during this early phase, but is rarely documented.

Six forms of the disease have been described—ulceroglandular, glandular, oculoglandular, oropharyngeal, typhoidal, and pneumonic—based on clinical presentation of the illness. These forms frequently overlap in individual patients.

The ulceroglandular form is most common in the North America, and makes up 48 to 75 percent of the infections. The skin lesion can appear before, during, or after the lymphadenopathy. The initial lesion is a painful papule, usually red in color that becomes necrotic and develops into a tender ulcer with a raised border. Animal bites or scratches usually produce ulcerations on the hands or forearms; tick bites tend to produce ulcerations on the trunk, inguinal area, legs, and the head and neck region. Multiple skin lesions can occur with exposure to more than one animal. If untreated, the ulcer can take weeks or months to heal and frequently leaves a scar.

Typhoidal tularemia resemble acute bacteremia caused by more common gram-negative organisms. The onset usually is abrupt. Fever is as high as 39.4°C (103°F), and chills, headache, generalized aching, vomiting, and occasional photophobia are present. Fever can persist for weeks if the infection is untreated. Hepatosplenomegaly is also reported, but rarely occurs in the acute stages of the infection. Skin rashes are quite common in this form of infections. Exanthems generally are of the maculopapular type and are located on the forearm and hand, including the palm and fingers.

The usual laboratory procedure is a serologiy.Antibodies are usually detected in the second week of illness, and peak between the fourth and fifth week after infection. Routine culturing of this organism is not encouraged , because it is hazardous for laboratory workers.

If tularemia is suspected, laboratory personnel should be notified.

Hunters and others who handle wild animals should be instructed not to skin, or dress game without appropriate gloves, masks, and eye covers. Wild game should be well cooked. Exposure to ticks should be controlled.

Overview

Tick bites are common both domestically and in travellers. Severe disease is not commonly considered with the exception of Lyme disease.

A preventative Algorithm for Ticks can be derived from the similar ABC method for control of malaria.

A wareness- The public is generally aware of the possibility of Lyme disease in many areas. Physicians need to keep an open differential diagnosis for other illnesses when confronted with a tick bite. Because the full spectrum of diseases is not seen (i.e. very little rash in Rocky Mt spotted fever) routine serolgies should be ordered on patients with a history of travel to endemic areas. Co-infections with different Tick borne diseases are possible.

B ite avoidance (Clothing, Insect repellent, Insecticide, Behaviours)

Understanding that Ticks don't jump on people but are often acquired from brushing against low-lying shrubbery. Wearing longs leaves and pants will dissuade entry. The tick will migrate to find a suitable feeding site. Ankle and wristbands treated with permethrin insecticide provide a contact kill to the tick.

Protective Clothing Clothing plays a major role in avoiding tick bites. Long sleeves and long pants are best. Pants should be worn with gaiters or tucked into high-top boots or socks. Ticks are more easily seen on such clothing.

Protecting pets with proper flea collars protects both the pet as well as the owner from the ticks.

Insect Repellents The best insect repellent is DEET or N, N-diethyl-meta-toluamide (N, N-diethyl-3-methylbenzamide). It has been reported to be effective against chiggers, ticks, fleas, and biting flies in laboratory studies, but some field studies have found it only about 80 percent as effective for ticks as it is for mosquitoes. It is not effective against flies. DEET is removed by sweating, absorption, evaporation, wiping, and rain, and in its unmodified form must be reapplied several times a day. However, two newer formulations have been developed: a microencapsulated product in which DEET is encased in a protein shell, and a polymerized form. Both persist much longer than standard preparations—at least twelve hours — and absorption through the skin is also greatly reduced.

The American Academy of Pediatrics has recently changed its recommendation to a more concentrated DEET preparation, 30 percent or less rather than, less than 10 percent, and now considers such preparations that are safe for infants as young as two months rather than limiting application at two years.

Insecticides Permethrin® (permanone tick repellent) is a pesticide derived from chrysanthemums that is highly effective against arthropods when used on clothing. This agent can kill insects so rapidly that it sometimes is thought to be a repellant, yet by itself, it has essentially no toxicity for humans.

A number of spray preparations are available. Clothing should be sprayed until damp and allowed to dry. Although sprays are convenient, they last only two to three washings.

Sawyer used to sell a 13.3% Permethrin Solution called PermaKill. Immersing clothing in a 1.5 percent solution and allowing it to dry, provided protection through approximately fifty washings, probably the life of most garments. Permethrin is such an efficient insecticide that hanging treated clothing in a closet effectively eliminates almost all arthropods. (When clothing is first removed from the solution is has a strong organic solvent odor reminiscent of xylene. However, once the clothing dries the odor completely disappears.)

R+C spray contains permethrin.

C ompliance with medications

The antimalarial and antibiotic doxycycline is effective against many Tick borne rickettsia, typhus and Lyme disease. Although chemoprophylaxis against tick bites is not suggested the choice of doxycycline for malarial chemoprophylaxis would have this benefit.

The Lyme disease vaccine Lymerix has been discontinued.

The TBE vaccine is available in Canada and may be considered for high-risk travellers. Travelers should take care against all ticks since of course other diseases share the geographic area with TBE.

D iagnosis

Tick borne diseases are not commonly thought of first line. Many patients with encephalitis present without the clear history of a tick bite.

Early referral to local Infectious disease specialists is recommended to order the correct serology.

Lyme's disease is confusing and the possibility of seronegative Lyme's disease should be acknowledged.

Collecting blood for acute and convalescent serology is important.

Clinicians should be aware on co-infections and be prepared to order additional serolgies and blood smears (babeosis, malaria) even in patients who have a diagnosis and are responding to treatment.

Tick Paralysis is worth looking for in all patients with an unexplained neurological decline and can actually save someone's life by finding the occult tick!

E nvironmental Control Tick Control:

The most effective measure for reducing the number of ticks around residences is to apply acaricides to the vegetation on which ticks live. A single application of agents such as carbaryl, cyfluthrin, or deltamethrin in early May can reduce populations of I. scapularis nymphs on residential properties by 68 to 100 percent. One well-timed application is enough.

These ticks are frequently found along the edges of forests and spill out into adjacent vegetation and lawns. Because the ticks are extremely sensitive to desiccation, increasing exposure to sun and air by removing dead leaves and brush. A border of wood chips where lawns abut forests reduces the number of ticks on lawns, presumably be creating a drying barrier. Adult I. scapularis ticks preferentially feed on deer, and reducing the deer population reduces the number of such ticks. However, all or nearly all deer must be removed to decrease the number of ticks substantially. Fencing that, keep deer out of residential areas is an acceptable alternative in areas where deer removal is not acceptable or practical. Baited devices that lure deer to a site where they can be treated with acaricides are being evaluated.

How to remove a Tick

Because some ticks secrete pathogens at the beginning of feeding it is always better to remove them as soon as possible. But some ticks do not secrete theirs till after several hours of feeding so it makes sense to carefully and deliberately remove the tick and not irritate it so that it might vomit into the wound.

Because of the cementum it may be difficult to remove a tick without pulling skin with it.

Some techniques like smothering it, pouring alcohol on it or poking it with a hot needle will irritate it and should be avoided.

Longitudinal traction is best. Avoid crushing the tick with tweezers or twisting its head off.

Steady traction is best. Inspect the wound for retained body parts.

Send the tick in a urinary specimen bottle. Ticks will quickly desiccate particularly since they may be missing their hypostome that was ripped open. To avoid desiccation in the specimen bottle put a square of moistened paper towel inside. If you find one- look for more!

Special thanks to Dr Jim Wilkerson (Pathology) of Utah who had helped prepare much of this material for me.

Dr Terry Galloway (Entemology) of Winnipeg been a great resource in answering all my bug questions.