Tick paralysis is a common and life-threatening emergency which caused by a tick bite. There are hundreds of species of ticks worldwide, with as many as 40 of whom are capable of producing paralysis. Most cases of tick paralysis occur in Australia and the United States.
Ixodes holocyclus (commonly referred to as paralysis ticks) are the species capable of producing paralysis in Australia. These ticks live on the east coast from North Queensland to Northern Victoria. They can be found year-round, however, are most prevalent in early spring and summer. Their natural hosts are the long-nosed bandicoot and the short-nosed bandicoot. But they can also parasitise other native animals including the possum, wallaby, and echidna, all of whom have a natural immunity to the tick’s toxin. However, paralysis ticks will infest domestic pets, livestock, and humans. The preferred habitat of ticks is areas of bush and scrub but can be picked up in other areas such as gardens, parklands, and paddocks.
In the United States, there are two main species of tick capable of producing paralysis, Dermacentor variabilis (American dog tick) and Dermacentor andersoni (Rocky Mountain wood tick) with most cases occurring in the Rocky Mountain states, Pacific Northwest and southeastern states between late spring and early summer.
The appearance varies between species, below is an image of the Ixodes holocyclus tick, located in Australia.
Ticks have four stages (moults) of life and require three hosts (either the same or different species) to complete their lifecycle, dropping off their host and re-attaching during each moult. The amount of time this take is dependent on the environmental temperature. The tick is capable of injecting a neurotoxin into the cat during the larval, nymph, and adult stages; however, the largest amount of toxin comes from the adult female.
- Egg – The female tick lays up to 3,000 eggs which hatch within 1-3 months into larva.
- Larvae (6 legged) – Approximately the size of a pinhead, tick larvae attach to their host within a week of hatching, feeding on the blood for up to a week. Once engorged, they drop off the host onto the ground and undergo the second moult, developing into the nymph.
- Nymph (8 legged) – Now, the size of a match head, the nymph finds a host, feeding for between 4-7 days before dropping off and entering the final moult stage.
- Adult (8 legged) – After a week, the adult ticks mate and find a new host to attach to. She finds a host to have one final blood feed, becoming engorged and then falling off the host and laying her eggs and then dies.
Stimuli such as heat and movement alert the tick to a potential host, it climbs onto vegetation, and when an animal passes, it waves its forelegs (known as questing) until it makes contact with the host.
It is the adult female tick who attaches to animals; some male ticks parasitises the female tick. As the tick attaches to the cat and borrows her mouthparts into the skin, she injects saliva, which contains several compounds that help the tick to bypass the host’s natural blood clotting ability so she can feed for over several days. This includes anti-clotting agents, antiplatelet agents, and vasodilator, which relaxes the blood vessel walls.
The saliva also contains a neurotoxin-a toxin which acts on the host’s nervous system-which causes paralysis by disrupting the connection between the nerves and the muscles. Not only are the muscles responsible for movement affected, but also those responsible for blinking, swallowing and breathing.
The tick is small when she attaches to her host, growing in size as she consumes more blood, a fully engorged tick can be as large as 10mm (1/4 inch). Toxic effects don’t occur quickly, as they do with snakes and spider bites and clinical signs can take 3-5 days after attachment. Even removal of the tick at this point will not stop the progression of symptoms.
Ixodes holocyclus symptoms develop between 3-5 days after the tick has attached.
Dermacentor variabilis (American dog tick) and Dermacentor andersoni (Rocky Mountain wood tick), symptoms develop within 5-9 days. The severity of symptoms is greater with I holocyclus than D. andersoni or D. variabilis.
Early symptoms of tick poisoning include:
- Change to meow or complete loss of voice (laryngeal paresis)
- Loss of appetite
- Vomiting or dry retching which may be frothy
- Regurgitation of food
- Excessive salivation
- Difficulty swallowing
- Noisy panting
- Dilated pupils
As symptoms progress, you may notice:
- Limb weakness, starting in the hind legs and progressing to the front legs, which cause incoordination and eventually, the cat will be unable to stand at all.
- Fecal and/or urinary incontinence
- Laboured breathing
- Blue-tinged gums
Remove food and water as poisoning can prevent the cat from swallowing, which can lead to choking and go straight to the veterinarian. Call ahead if possible to let them know you are on your way.
The longer the delay in treatment, the worse the outcome.
The goal of treatment is to counteract the effect of the toxin as well as provide supportive care.
- Affected cats will be treated as an inpatient, during which time the cat will receive tick antiserum (TAS) to treat I. holocyclus. Serum, which is the clear part of the blood which contains antibodies and is obtained from dogs who have been made hyperimmune via repeated exposure to paralysis ticks. Sedation may be necessary before treatment as stress can aggravate symptoms.
- Cats affected by D. andersoni or D. variabilis usually improve within 24-72 hours once the tick has been removed.
- Artificial tears in the case of eyelid paresis to prevent the cornea drying out.
- Regular monitoring of the cat’s temperature to avoid hypothermia or hyperthermia and take action if they do develop.
- Catheterization if the cat is unable to urinate on his own.
- Oxygen therapy for cats who are having difficulty breathing.
- Frequent tick checks to make sure there are none remaining.
- Intravenous fluids to treat or prevent dehydration.
Recovery is dependent upon the severity of symptoms and how quickly treatment commenced. Generally, veterinary treatment takes two-plus days. It will be necessary to care for your cat for some time after discharge from the hospital.
Keep the cat inside for at least two weeks after discharge from hospital.
- Feed small meals 2-3 times a day, and monitor to ensure the cat can swallow normally.
- Keep cats recovering from tick paralysis stress-free.
- Continue to check your cat for ticks at least once a day.
Wear latex gloves when removing a tick. Using tweezers or a tick remover, which you can purchase these for a few dollars from your veterinarian, firmly grasp the tick’s head, as close to the cat’s skin as possible and pull gently to avoid leaving the mouthparts embedded in the skin. Be extremely careful not to squeeze the body of the tick as this will inject more poison and pathogens into the cat’s system. You can also kill the tick while it’s still on the cat by using an appropriate insecticide, such as Frontline spray.
After removal of the tick, there will be a crater where the head was; this will remain for several weeks. Watch for signs of infection.
Even after the removal of a tick, your cat can still develop symptoms associated with tick poisoning, and careful monitoring of your cat will be necessary.
Once removed, save the tick by placing it in a jar of methylated spirit or alcohol so you can take it to your veterinarian for identification.
Start from the tip of the nose and using the tips of your fingers, work your way right down to the tail. Ensure you check between the toes, inside the ears (be careful), and skin folds. Go against the grain of the fur and don’t forget to check underneath collars. Ticks will feel like small bumps on the skin. Common locations include the head, neck, front legs and groin.
Can indoor cats get ticks?
Yes, it is possible that ticks can be brought indoors on clothing or on other pets (usually dogs) who go outside.
Tick preventatives can reduce the risk, but they are not 100% fail-safe. It is important to check pets once a day for ticks (even those on a preventative).
Avoid letting your cat roam in the native bushland.
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Lyme disease is an infection caused by a bacteria known as Borrelia, which is transmitted via tick bites.
Although it has yet to be proven that the paralysis tick passes on Lyme disease to cats in Australia. Lyme disease is passed on via the Deer Tick, also known as the Black-Legged tick (Ixodes scapularis) in North America. You cannot catch Lyme disease from your pet, but humans can become infected from ticks.
The University of Queensland has created a vaccine and is seeking to engage with animal technology companies to co-develop the vacine.