An engorged Australian paralysis tick, Ixodes holocyclus, between the digits of the back foot of a dog.
In my last post on ticks, I decided to leave the treatment aspects for another posting. So I will attempt to cover some ground here. We have had a busy couple of weeks here recently, especially the recent long weekend, hence the delay in updating my blog. The range of signs with which animals present to us after suffering the effects of tick toxin is so vast that the treatment required must be tailored to the individual patient. There is definitely no “one size fits all” and no hard and fast rules apply.
As I mentioned in the previous post, animals suffering from the effects of toxin from the Australian paralysis tick, Ixodes holocyclus, do not recover with removal of the tick alone. Once clinical signs develop, regardless of whether the tick has been removed or not, few animals recover without a dose of tick anti-serum.
An animal arriving to the hospital with early and mild signs of tick paralysis may only need to have a dose of anti-serum, an anti-tick rinse, maybe a haircut to help us find more of the nasties, and some monitoring. Some animals may be given sedation prior to treatment because they can become quite anxious as a result of being paralysed. Some require ongoing sedation for similar reasons.
In general, monitoring for the day or overnight, as a minimum, is strongly advised. The reasons for this are twofold. Some animals will get worse after having a dose of anti-serum. Tick paralysis takes time to develop, and takes time to resolve. The slow action of the toxin means that the anti-serum also takes time to work, so it is not a case of giving the anti-serum and expecting the animal to respond well immediately. For some animals, any deterioration may just be further limb weakness, but for others respiratory weakness can progress. Others may also begin to retch and regurgitate. If they are not able to protect their airway due to respiratory or laryngeal weakness, aspiration (inhaling food or liquids) or airway blockage is a very real risk.
The other reason is rest. Nothing helps an animal recover from tick paralysis more than rest. And tick anti-serum. Most dogs will not get enough rest in the home environment for various reasons and there is always the anxiety of wanting to be with the pack. In hospital, there may be some anxiety at being away from the pack, but if it is causing obvious distress, medication can help. I honestly feel that the majority of animals actually do relax more in the hospital environment away from their owners when recovering from tick paralysis, as harsh as this may sound.
Tick anti-serum may not be all that is required by an animal, even with mild signs. We recommend an anti-tick rinse to kill the ticks that may not be visible and strongly advise clipping or shaving medium to long haired animals (even some with short coats). Finding ticks can be tricky. The majority of affected animals will only have one tick, but where a second, third or fourth (or more) is present, they must be found. Keep in mind that no tick preventative is 100% effective, and we have found live ticks on recently rinsed animals. So clipping may be the only chance we have of finding all the ticks. Tick antiserum has no effect on live ticks, so any remaining following treatment can continue to inject toxin. A relapse in signs will occur and in general is much more difficult to treat second time around in the already weakened animal. Clipping also provides the benefit of helping tick searches in the weeks after treatment, during which time a second exposure may also be more debilitating and the treatment potentially more risky.
Animals with slightly more advanced paralysis, particularly those with poor swallowing and gag reflexes, may benefit from intravenous fluids while in hospital as well. Some may be quite dehydrated already due to delayed presentation or repeated retching or vomiting. Those that have been paralysed for a day or two may already have an aspiration pneumonia brewing and have quite significant needs for fluids.
The vomiting or retching that is seen with tick paralysis is often associated with reduced swallowing ability and weakness of the oesophagus. Saliva continues to be secreted in the mouth and the animal may not be able to swallow it properly down into the stomach. It tends to pool in the pharynx or the oesophagus and the only way the animal can clear it is to vomit or retch it up. For some animals, this becomes an ongoing issue so management of retching in our hospital patients is very important, to reduce the chance they may aspirate this fluid down into the lungs. Aspiration pneumonia can have a severely debilitating effect on these patients and may slow or prevent recovery once it develops.
In discussing the lung aspects, airway management is the next important point. Some animals, particularly cats, will present with significant breathing problems as a result of laryngeal paralysis. Cats have a very sensitive larynx that can readily spasm with only mild insult. Such spasming can obstruct the airway making inhalation very difficult. As a result, these cats come in distressed and almost screaming, to try to open their airways and get a breath in. Dogs can also show severe abdominal sucking movements in trying to inhale, suggesting a collapsed larynx. Some of these animals will respond really well to sedation alone, but others will require a light anaesthetic and passage of an endotracheal tube, as used for delivering anaesthetic agents, just to help open the airway. Often the distress at not being able to breathe sparks a vicious cycle and drugs can be wonderful for interrupting this.
In some cases, further support of breathing is required. We see two situations commonly, animals who are working hard to breathe with tiring chest muscles, and those who are having trouble getting enough oxygen into their lungs due to pneumonia or oedema (fluid in the lungs). In both of these cases, additional oxygen can help to reduce the work of breathing. This is often provided by placing a small tube into the nostrils of the animal to deliver a higher concentration of oxygen to the animal, if they tolerate it (occasionally small dogs and cats may become too stressed by this). Alternatively, they can be placed in a perspex box or covered cage which has oxygen piped into, providing a high concentration oxygen environment.
One of our recent tick paralysis survivors who spent 24 hours on a ventilator. Here she is recovering with a nasal oxygen catheter in place to help support her breathing.
Tick paralysis eventually causes paralysis of the respiratory muscles and when animals fail to move air, their blood oxygen levels drop and their blood carbon dioxide levels rise. This quickly leads to death. Once a paralysed patient is heading in this direction, unfortunately there is only one treatment option available and that is artificial ventilation.
Artificial ventilation requires the patient to be appropriately anaesthetised or heavily sedated, so they can have an endotracheal tube placed and be attached to a machine that will do the work of breathing for them. This is not a benign procedure and unfortunately, once an animal goes onto the ventilator, there is no way of knowing how long they will need to be ventilated for. It is an expensive exercise and owners willing to proceed with this option need to be prepared for several days of ventilation in many cases.
Fortunately not all animals require such intensive management and the majority of animals with tick paralysis will require only a couple of days or more of hospital management before they can go home. Other management aspects tend to focus on monitoring bladder function, eyelid function, return of gag reflex and repeated tick searches while the animal is hospitalised to be sure (as sure as we can be) that there are no more ticks on the patient.
The importance of appropriate nursing care can’t be stressed enough. Some animals, being paralysed, have difficulty urinating. At times it appears they are urinating as they may have a wet patch under them, but when the bladder is felt for, a large distended bladder can sometimes be detected. The urine beneath the animal is the overflow that essentially can’t fit in the distended bladder which becomes overstretched running the risk of permanent bladder problems. These patients need assistance to urinate (we express their bladders for them) so that the bladder can stay small and healthy.
The eyelids will occasionally become paralysed also especially when the tick is located on the head or near one of the eyes. If unable to blink, the surface of the eye becomes dry and often small ulcers develop. These ulcers can become quite large and cause severe damage and eye disease if not managed with eye drops. In the worst case scenario, the eye may become permanently injured if the ulcers penetrate deep enough to cause the eye to rupture.
Initial signs of recovery from tick toxin often take about 12 hours to be seen, except in some of the milder cases, with full recovery taking up to several days or longer. Once the animal’s gag reflex improves (tested basically by putting our fingers into the back of the animal’s mouth – if temperament permits of course!) we begin to offer water and small pieces of food. If we see that the patient can swallow without any gagging or retching, we know they are close to being able to go home.
Generally we are happy to send animals home from hospital once we know they are able to eat and drink without gagging or retching, and are able to urinate completely on their own (and empty their bladder). Cats may be the exception, since often they are too nervous to eat in hospital and may not use an unfamiliar litter tray. Individual judgement may be used in these cases.
One other point I will stress is for people to use extreme caution when deciding not to accept appropriate veterinary care for their pets. I once saw a dog suffer and die very quickly of its paralysis as a result of its owners attempting to treat tick paralysis with a homeopathic remedy, bringing the patient to me when it was far too late. Similarly, leaving an animal overnight hoping its signs wont progress quickly is a very risky exercise and many owners have regretted making this decision.
Tick paralysis in Australia can certainly be a severely debilitating disease, and unfortunately, it is very difficult to prevent where animals live or roam in areas where they are found. Where ticks are prevalent, we urge people to consider having pet insurance but be certain to look closely at the insurance policy. Not all policies will cover tick paralysis and some will only cover it once.
The final word on this topic is vigilance. Be vigilant about checking your pets for ticks where you know they exist, even where you are not sure they exist. They are evil little creatures with no good purpose for existence. A true parasite!
The Sleepless Veterinarian 