Tick paralysis is an acute, progressive, ascending motor paralysis caused by a salivary neurotoxin produced by certain species of ticks.
- Presence of a tick in conjunction with the sudden (12-24 hr) appearance of leg weakness and/or respiratory impairment is diagnostic. The offending tick may no longer be attached, but a tick “crater” (a small hole surrounded by a slightly raised and inflamed area) in the skin confirms the diagnosis.
- unexplained vomiting
- acute left-sided congestive heart failure
In North America, D andersoni (the Rocky Mountain wood tick) and D variabilis (the American dog tick) are the most common causes, but D albipictus, I scapularis, Amblyomma americanum, A maculatum, R sanguineus, and O megnini may cause paralysis.
- Removal of the tick(s) is necessary.
- In North America, removal of all ticks usually results in obvious improvement within 24 hr.
- In cases in which an adult female I holocyclus has been removed but the animal shows no adverse clinical signs, the owner should monitor the animal for 24 hr and return for treatment if signs of tick paralysis develop.
- Canine tick hyperimmune serum, also called tick antiserum (TAS), is the specific treatment for I holocyclus -induced tick paralysis.Minimization of stress and anxiety cannot be overemphasized. Acepromazine may be given SC before any other medication or handling that may upset the animal. However, acepromazine should be avoided or given at a reduced dose if the animal is depressed or hypothermic. Opiates are an alternative. Any procedure (eg, IV injection, searching for ticks) that may excite the animal should be postponed until the animal settles.
The animal’s condition can be expected to deteriorate for the next 24 hr after ticks are removed. Hospitalization, with monitoring and good nursing care, is advised during this period. The animal should be kept in a quiet, dark, comfortable place. Sternal recumbency should be maintained if comfortable; otherwise, the animal should be positioned in lateral recumbency with its shoulder being the highest point. Eye protectants should be used to prevent corneal ulceration or dry eyes, and the bladder expressed once or twice daily. Suction of the pharynx, larynx, and proximal esophagus minimizes respiratory distress caused by saliva pooling and esophageal dysfunction. An esophageal tube may be inserted to provide drainage. General anesthesia may be indicated in animals that are severely dyspneic to allow administration of oxygen, esophageal suction, and pulmonary drainage. Mechanical or manual ventilation may be required for 24 hr.
Nothing should be given PO until paralysis has resolved. IV fluid support is not routinely needed during the first 48 hr of hospitalization. IV fluids may add to pulmonary edema, so they should be used slowly and minimally. If the PCV is > 50%, colloid or heta/penta starch fluids should be considered rather than crystalloids. Furosemide can be given IV to help reduce pulmonary edema.
During hospitalization, regular searches for attached ticks should be done. Long or matted hair should be clipped. Application of an acaricide may kill ticks missed in searching. However, the stress of clipping or bathing can be detrimental in severely affected or nervous animals and may increase hypothermia.
About 5% of animals are likely to die despite all treatment efforts, especially those with advanced paralysis and dyspnea. Older animals or those with pre-existing cardiopulmonary disease are at greatest risk.
For animals that recover, owners should be advised to continue searching for ticks, use appropriate preventive methods to avoid reattachment of ticks, and avoid stressing or strenuously exercising the animal over the next 2 mo.
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