Tick paralysis is the only
tick-borne disease
Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and proto ...
that is not caused by an infectious organism. The illness is caused by a
neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
produced in the
tick
Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...
's
salivary gland
The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gla ...
. After prolonged attachment, the engorged tick transmits the toxin to its host. The incidence of tick paralysis is unknown. Patients can experience severe respiratory distress (similar to
anaphylaxis
Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follow ...
).
Signs and symptoms
Tick paralysis results from injection of a toxin from tick salivary glands during a blood meal. The toxin causes
symptom
Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
s within 2–7 days, beginning with weakness in both legs that progresses to
paralysis
Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
. The
paralysis ascends to the trunk, arms, and head within hours and may lead to
respiratory failure
Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...
and death. The disease can present as acute
ataxia
Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
without muscle weakness.
Patients may report minor sensory symptoms, such as local numbness, but constitutional signs are usually absent.
Deep tendon reflexes
The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching within the muscle. The reflex functions to maintain the muscle at a constant length. The term deep tendon reflex is ...
are usually
decreased or absent, and
ophthalmoplegia
Ophthalmoparesis refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic, ophthalmologic, and endocrine disease.
Internal o ...
and
bulbar palsy
Bulbar palsy refers to a range of different signs and symptoms linked to impairment of function of the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the accessory nerve (CN XI), and the hypoglossal nerve (CN XII). It is caused by a low ...
can occur.
Electromyographic
Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an medical instrument, instrument called an electromyograph to produce a record called an electromyog ...
(EMG) studies usually show a variable reduction in the amplitude of compound muscle
action potential
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...
s, but no abnormalities of repetitive nerve stimulation studies. These appear to result from a failure of
acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
release at the motor nerve terminal level. There may be subtle abnormalities of motor
nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
conduction velocity and sensory action potentials.
Pathogenesis
Tick paralysis is believed to be due to toxins found in the tick's saliva that enter the bloodstream while the tick is feeding. The two ticks most commonly associated with North American tick paralysis are the Rocky Mountain wood tick (''
Dermacentor andersoni
''Dermacentor andersoni'', commonly known as the Rocky Mountain wood tick, is a hard tick, or member of the Ixodidae family, with three life stages including larvae, nymph, and finally adult, or, more entomologically, imago. This tick is genera ...
'') and the American dog tick (''
Dermacentor variabilis
''Dermacentor variabilis'', also known as the American dog tick or wood tick, is a species of tick that is known to carry bacteria responsible for several diseases in humans, including Rocky Mountain spotted fever and tularemia (''Francisella tul ...
''); however, 43 tick species have been implicated in human disease around the world. Most North American cases of tick paralysis occur from April to June, when adult ''Dermacentor'' ticks emerge from hibernation and actively seek hosts. In Australia, tick paralysis is caused by the tick ''
Ixodes holocyclus
''Ixodes holocyclus'', commonly known as the Australian paralysis tick, is one of about 75 species in the Australian tick fauna and is considered the most medically important. It can cause paralysis by injecting neurotoxins into its host. It is u ...
''. Prior to 1989, 20 fatal cases were reported in Australia.
Although tick paralysis is of concern in domestic animals and livestock in the United States as well, human cases are rare and usually occur in children under the age of 10.
Tick paralysis occurs when an engorged and gravid (egg-laden) female tick produces a
neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
in its salivary glands and transmits it to its host during feeding. Experiments have indicated that the greatest amount of toxin is produced between the fifth and seventh day of attachment (often initiating or increasing the severity of symptoms), although the timing may vary depending on the species of tick.
Unlike
Lyme disease
Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium, which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migran ...
,
ehrlichiosis
Ehrlichiosis is a Tick-borne disease, tick-borne
bacterial infection, caused by bacteria of the family Anaplasmataceae, genera ''Ehrlichia'' and ''Anaplasma''. These Obligate intracellular parasite, obligate intracellular bacteria infect and kill ...
, and
babesiosis
Babesiosis or piroplasmosis is a malaria-like parasitic disease caused by infection with a eukaryotic parasite in the order Piroplasmida, typically a ''Babesia'' or ''Theileria'', in the phylum Apicomplexa. Human babesiosis transmission via ti ...
, which are caused by the systemic proliferation and expansion of parasites in their hosts long after the offending tick is gone, tick paralysis is chemically induced by the tick and therefore usually only continues in its presence. Once the tick is removed, symptoms usually diminish rapidly. However, in some cases, profound paralysis can develop and even become fatal before anyone becomes aware of a tick's presence.
Diagnosis
Diagnosis is based on symptoms and upon finding an embedded tick, usually on the scalp.
In the absence of a tick, the differential diagnosis includes
Guillain–Barré syndrome
Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain often ...
. Early signs of tick poisoning could be a change of an animals' ‘voice’, weakness in the back legs or vomiting.
Prevention
No human
vaccine
A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifie ...
is currently available for any tick-borne disease, except for
tick-borne encephalitis
Tick-borne encephalitis (TBE) is a viral infectious disease involving the central nervous system. The disease most often manifests as meningitis, encephalitis or meningoencephalitis. Myelitis and spinal paralysis also occurs. In about one third ...
. Individuals should therefore take precautions when entering tick-infested areas, particularly in the spring and summer months. Preventive measures include avoiding trails that are overgrown with bushy vegetation, wearing light-coloured clothes that allow one to see the ticks more easily, and wearing long pants and closed-toe shoes. Tick repellents containing
DEET
''N'',''N''-Diethyl-''meta''-toluamide, also called DEET () or diethyltoluamide, is the most common active ingredient in insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection ag ...
(N,N, diethyl-m-toluamide) are only marginally effective and can be applied to skin or clothing. Rarely, severe reactions can occur in some people who use DEET-containing products. Young children may be especially vulnerable to these adverse effects.
Permethrin
Permethrin is a medication and an insecticide. As a medication, it is used to treat scabies and lice. It is applied to the skin as a cream or lotion. As an insecticide, it can be sprayed onto clothing or mosquito nets to kill the insects that t ...
, which can only be applied to clothing, is much more effective in preventing tick bites. Permethrin is not a repellent but rather an insecticide; it causes ticks to curl up and fall off the protected clothing.
Treatment
Removal of the offending tick usually results in resolution of symptoms within several hours to days. If the tick is not removed, the toxin can be fatal. A 1969 study of children reported mortality rates of 10 – 12 percent, mostly due to respiratory paralysis. The tick is best removed by grasping it as close to the skin as possible and pulling in a firm steady manner. Because the toxin lies in the tick's salivary glands, care must be taken to remove the entire tick (including the head), or symptoms may persist.
It is important to note that, unlike the toxin of other tick species, the toxin of ''
Ixodes holocyclus
''Ixodes holocyclus'', commonly known as the Australian paralysis tick, is one of about 75 species in the Australian tick fauna and is considered the most medically important. It can cause paralysis by injecting neurotoxins into its host. It is u ...
'' (Australian paralysis tick) may still be fatal even if the tick is removed.
For affected animals, food and water intake can worsen the outcome, as the toxin can prevent the animal from swallowing properly. People who find a tick on their animal, are advised to remove it immediately and seek veterinary assistance if the animal shows any signs of illness. The tick can be placed in a tightly sealed plastic bag and taken to a veterinarian for identification.
Research
Although several attempts have been made to isolate and identify the neurotoxin since the first isolation in 1966, the exact structure of the toxin has still not been published. The 40-80 kDa
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
fraction contains the toxin.
The neurotoxin structure and gene, at least for the tick species
Ixodes holocyclus
''Ixodes holocyclus'', commonly known as the Australian paralysis tick, is one of about 75 species in the Australian tick fauna and is considered the most medically important. It can cause paralysis by injecting neurotoxins into its host. It is u ...
have since been identified and are called holocyclotoxins after the species. At least three members (HT-1, HT-3, and HT-12) trigger paralysis by presynaptic inhibition of neurotransmitter release via a calcium dependent mechanism resulting in a reduction of quantal content, and loss of effective neuromuscular synaptic transmission.
Culture
In the TV show, ''
Hart of Dixie
''Hart of Dixie'' is an American comedy-drama television series that aired on The CW from September 26, 2011, to March 27, 2015. The series, created by Leila Gerstein, stars Rachel Bilson as Dr. Zoe Hart, a New Yorker who, after her dreams of b ...
'', Season 1, Episode 2, a patient is diagnosed with tick paralysis who has been deer hunting.
In the TV show, ''
Emergency!
''Emergency!'' is an American action-adventure medical drama television series jointly produced by Mark VII Limited and Universal Television. Debuting on NBC as a midseason replacement on January 15, 1972, replacing the two short-lived situatio ...
'', Season 5, Episode 4, "
Equipment
Equipment most commonly refers to a set of tools or other objects commonly used to achieve a particular objective. Different job
Work or labor (or labour in British English) is intentional activity people perform to support the needs and ...
" (first aired Oct. 4, 1975), Dr. Joe Early diagnoses a young boy who has fallen from a tree with tick paralysis, after eliminating
polio
Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe s ...
as a cause.
In the TV show, ''
House
A house is a single-unit residential building. It may range in complexity from a rudimentary hut to a complex structure of wood, masonry, concrete or other material, outfitted with plumbing, electrical, and heating, ventilation, and air condi ...
'', Season 2, Episode 16, "
Safe
A safe (also called a strongbox or coffer) is a secure lockable box used for securing valuable objects against theft or fire. A safe is usually a hollow cuboid or cylinder, with one face being removable or hinged to form a door. The body and ...
", Dr House diagnoses a patient (played by
Michelle Trachtenberg
Michelle Trachtenberg (; born October 11, 1985) is an American actress and model. Trachtenberg began her career at age three, appearing in a number of commercials, films, and television series as a child. Her starring role on the Nickelodeon tel ...
) with tick paralysis.
In the TV show, ''
Remedy'', Season 1 Episode 7, "
Tomorrow, the Green Grass", Rebecca is diagnosed with tick paralysis.
In the TV show, ''
Royal Pains
''Royal Pains'' (stylized ℞oyalPains) is an American comedy-drama television series that ran on the USA Network from 2009 to 2016. The series was based in part on actual concierge medicine practices of independent doctors and companies. The ca ...
'', Season 1 Episode 3, "
Strategic Planning
Strategic planning is an organization's process of defining its strategy or direction, and making decisions on allocating its resources to attain strategic goals.
It may also extend to control mechanisms for guiding the implementation of the st ...
", a US Senator's teenage son is diagnosed with and overcomes tick paralysis.
In the TV show, ''
Chicago Med
''Chicago Med'' is an American medical drama television series created by Dick Wolf and Matt Olmstead, and is the third installment of Wolf Entertainment's ''Chicago'' franchise. The series premiered on NBC on November 17, 2015. ''Chicago Med'' ...
'', Season 3, Episode 5, "
Mountains and Molehills", a young girl returning from Australia with increasing paralysis is diagnosed with tick paralysis.
See also
*
Polyneuropathy in dogs and cats
Polyneuropathy in dogs and cats is a collection of peripheral nerve disorders that often are breed-related in these animals. Polyneuropathy indicates that multiple nerves are involved, unlike mononeuropathy. Polyneuropathy usually involves motor ...
for tick paralysis in dogs
*
Tick-borne disease
Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and proto ...
References
External links
{{authority control
Neurological disorders
Tick-borne diseases