Tick Season – oh my!

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TICK SEASON

Spring is here, and to some people that may mean birds chirping and flowers blooming, but to those who are really outdoorsy that means it’s time for ticks! These disgusting and familiar little bugs are not insects (which, by definition, have 3 body segments and 6 legs in their adult form), but are in the arachnid family alongside spiders and mites (with 2 body segments and 8 legs). The two commonest tick species that are found in Wisconsin are the deer tick AKA black-legged tick (Ixodes scapularis) and the wood tick AKA American Dog Tick (dermacentor variabilis). The deer tick is smaller and can be much harder to see, especially when hidden under fur. Other than the gross-out factor, why do we care about ticks? Unfortunately these pesky little guys are well-known for their role in the transmission of infections such as Lyme Disease.

 

Ticks have a few lifestages. They hatch from an egg into a larval form (which actually only have 6 legs). Larvae are VERY little, smaller than the size of a period. These are also called “seed ticks.” After feeding on the first host (usually a rodent or bird), the tick detaches and falls to the ground where it morphs into a nymph (not a whole lot bigger than the larva). It is inactive over the winter, then in Spring seeks a new host. After feeding on the new host (any variety of wild animal, pet, or human), it again drops to the ground so it can undergo its final stage of development to an adult. The adult will then locate a third host (again, any wild or pet animal or human) to feed from, then mates and falls back to the ground. The male dies, while the female survives until the next Spring when she will lay about 3000 eggs to continue the cycle. Diseases are primarily transmitted from the nymph or adult tick.

 

Deer ticks are the ones we worry about most in Wisconsin because they play the most major role in disease transmission. They are smaller, and have a characteristic black “hood” over the shoulder area of the upper back. Lyme Disease and Anaplasma are the commonest diseases that we encounter in pet dogs (and they both affect humans as well!). Deer ticks can also spread Babesia or cause tick paralysis. Wood ticks rarely transmit diseases in Wisconsin, but they can spread Cytauxzoonosis or can cause tick paralysis. Wood ticks are larger and have a brownish red body that may have streaks or a cape of whitish or silver.

 

Lyme Disease is the most well-known tick-borne infection encountered in Wisconsin for both dogs and humans. Its presentation is variable, from an acute onset of fever and hot swollen joints (causing lameness that often seems to shift from one leg to another as well as lethargy and poor appetite), to a more chronic achiness and stiffness, to infection in the kidneys or heart. Many cases are treatable with antibiotics, anti-inflammatories, and rest; however like in humans, lyme disease will sometimes recur on and off despite treatments, and can be fatal. The organism is excellent at hiding inside of its host’s cells to avoid detection by the immune system and to escape from the circulating antibiotics.

 

Anaplasma also affects dogs, and is characterized by fever, lethargy, and poor appetite as well, but sometimes also low platelet counts or liver inflammation. It usually responds well to antibiotic therapy, although chronic recurrent infections can be seen with this disease.

 

Babesia affects dogs, and most commonly causes anemia by rupture of red blood cells, and can present in an acute form with fever, jaundice, and loss of appetite or in a chronic and relapsing form. This disease is much more difficult to treat.

 

Cytauxzoonosis affects cats and usually causes a severe illness with high fever, jaundice, difficulty breathing, anemia, and loss of appetite. It is usually fatal within about 2 weeks, although in rare cases, cats have been successfully treated for it.
Tick paralysis is seen in dogs but not cats, and is caused by the release of a toxin that some wood ticks (as well as other non-Wisconsin ticks) can carry, and causes a limp paralysis of rear legs, and sometimes the entire body. This can be fatal if the muscles necessary for respiration become paralyzed. Once the ticks are removed (easier said than done if some of the ticks are hidden in the fur) the dog will typically recover from the paralysis.

 

The best way to manage ticks and tick-borne diseases is prevention! This may mean

  1. Avoidance of areas most likely to harbor high numbers of ticks. When avoidance is not a reasonable option, a multimodal approach to tick prevention is your best bet.
  2. A manual “tick check” after possible exposure (for example, every evening during a camping trip) to remove any ticks that can be found from both yourself and your dog/cat is highly recommended. Most ticks must feed for several hours prior to the disease being transmitted, so removing the tick within a few hours of attachment lowers the odds of a disease being acquired.
  3. Using a good quality tick preventive product can help a lot as well (oral forms by prescription, topical forms in both prescription or over-the-counter varieties, or tick collars). Some products are noticeably superior to others in efficacy or safety, so feel free to discuss your options with your veterinarian at your next pet exam.
  4. Vaccination for lyme disease is helpful but not 100% protective against exposure to lyme disease, and there is no vaccination for the other diseases mentioned. So while it is highly recommended for dogs with lifestyles that put them at risk for tick bites, vaccination cannot be relied upon without pairing a preventive product and manual tick checks.

 

Excellent resources for further reading (and pictures!) on ticks in Wisconsin:

http://labs.russell.wisc.edu/wisconsin-ticks/

https://www.dhs.wisconsin.gov/tickborne/index.htm

Or ask your veterinarian!