Page 962 - Problem-Based Feline Medicine

954 PART 11 CAT WITH AN ABNORMAL GAIT

Clinical signs ● One (or more) adult female Ixodes holocyclus tick(s)
or other paralysis ticks are found on the animal.
Acute onset of paresis/ataxia of the hindlimbs is the
● A “crater”, the feeding lesion which remains after
most consistent clinical sign. This rapidly progresses over
the tick has detached, is found on the animal.
several hours to flaccid paralysis and ascends to involve
– Multiple larval or nymphal Ixodes holocyclus
the forelimbs and results in lateral recumbency.
ticks are found on the animal.
Dyspnea accompanies paralysis, and severe dyspnea – A tick or “crater” is not found but the animal
with forced expiration and cyanosis occurs responds to specific treatment for tick toxicity.
terminally.
A change in voice and inappetence may occur early in Differential diagnosis
the course of disease.
Various snake envenomations may present similarly
Pupils are dilated and become non-responsive to light. but are not usually associated with dyspnea.
The nictitating membrane may protrude across the
Visualization of the Ixodes holocyclus tick or other
globe.
paralysis ticks are diagnostic. The brown dog tick,
The gag reflex is impaired and drooling of saliva Rhipicephalus sanguineus, is found in some of the
occurs. same areas as Ixodes holocyclus, but it very rarely par-
asitizes cats and is not associated with paralysis.
Regurgitation/vomiting can occur rarely at any stage.
Death can occur within 24–48 hours of onset of Treatment
signs.
Treatment involves removing the tick(s), administration
Scoring systems to describe the progressive stages of
of specific antitoxin serum and supportive care.
paralysis and respiratory compromise are as follows:
● Gait score system. With Ixodes holocyclus (Australia), often clinical signs
– Score 1: Can walk: able to stand from recum- will progress during the first 24 hours of treatment due
bency and ambulate. to the delayed onset of the toxin’s action. In USA, signs
– Score 2: Cannot walk: requires aid to stand but usually resolve rapidly after tick has been removed, and
can maintain stance. supportive therapy is rarely necessary.
– Score 3: Cannot stand: unable to maintain a
The tick can be removed manually using curved forceps
standing position.
or a pair of partially opened scissors to lever out the tick
– Score 4: Cannot right: unable to maintain sternal
while avoiding any pressure on the tick’s body. Search
recumbency.
thoroughly for additional ticks. Apply tickicides
● Respiratory score system.
(fipronil, pyrethrins) to kill any additional unseen ticks.
– Score A: Normal character and rate (less than 30
breaths per minute). Tick Antitoxin Serum (TAS) for treatment of Ixodes
– Score B: Normal character and increased rate Holocyclus toxicity is manufactured from canine serum
(greater than 30 breaths per minute). so there is a risk of anaphylaxis when administered to
– Score C: Altered character with expiratory cats. TAS can also produce a vagally mediated sys-
sigh/grunt (undefined rate). temic reaction seen clinically as bradycardia, hypoten-
– Score D: Cyanosis and severe dyspnea. sion and circulatory shock (B-J reaction). To minimize
these risks give:
● Acepromazine (0.03 mg/kg SC or IM) to relieve
Diagnosis
anxiety and respiratory distress. Wait 20–30 min-
Diagnosis is made when clinical signs typical of tick utes before giving TAS.
toxicity are observed in an animal in an area where ● Atropine (0.04–0.1 mg/kg SC) to block the B-J
Ixodes holocyclus or other paralysis ticks are endemic reaction, reduce salivation, and produce bronchodi-
and either: lation. Wait 20–30 minutes before giving TAS.