The basic steps involved in the treatment of tick paralysis at our hospital are:
1. We do thorough searches of the colony daily and have a prompt response to calls from the community. The sooner the bat can be assessed the better as they are extremely vulnerable on the ground and deteriorate quickly from the tick toxin.
2. Quick assessment to decide the prognosis. Signs (other than moribund) that indicate the bat has little chance of survival and should be euthanased include:
- pulmonary edema – frothy discharge from mouth or nose
- presence of gasping, especially if accompanied by lifting the head and other associated limb movements that aid the muscles of respiration.
- inability to swallow- we use diluted mango and apple juice to test
- severe infestation by maggots
- lack of spark in the eye, eyes slowly closing regularly
- a low, irregular or very fast heart rate (normal is 360 beats per minute)
- a rectal temperature below 34 degrees centigrade
- degree of flaccid paralysis of legs and distress
If unsure of the prognosis, remove the tick but wait to fully asses and treat the bat back at the hospital. Initially the bat can appear to be better than it really is but the stress of the rescue (being handled, carried in a basket and then transported in a vehicle) can then worsen the situation for the bat. The look in the bat’s eyes means a lot to an experienced clinician. We find the adrenaline rush of the bat seeing a human at close quarters can often make the bat seem in better condition than it really is, mainly because they become wide-eyed and fully alert. However they can quickly lose this and then appear worse than they really are mainly through the development of a stress gasp. It is not unusual for bats to deteriorate over the first 24 hours of coming into care before improving.
Find and remove the tick immediately. Remember there may be more than one but be happy with one at the point of rescue. There are many different ideas about how to do this. Some people like to poison or freeze the tick in situ. However this is very difficult in a wild animal with long hair and sharp teeth near the site of the tick. Others like to use various forms of forceps but again there are difficulties. We currently remove the tick very quickly and competently by having finger nails of the right length! The tick is usually (90% of times) around the head and neck as it is the carbon dioxide of expiration that attracts them, but can be anywhere.
In rare cases the tick has fallen off and you will be searching for a small crater where the tick was attached. However if you do not find a tick always consider another diagnosis and in bats lower limb paralysis can be a sign of spinal injury or in worse case scenario Australian Bat Lyssavirus. Of course these can also accompany tick paralysis though we have never knowingly seen it in 20 years and thousands of bats. The lack of any respiratory signs in a ‘tick bat’ without a tick should alert you to an alternative diagnosis. We have found tick paralysis in a bat caught on barbed wire.
It is not is the best interests of the bat to treat the bat when the prognosis is poor. These animals need to return to the wild flying large distances and We proceed with the following steps if the bat seems viable.
3. Keep the bat calm. If the bat is female and has young, we need to make a decision of whether to leave the pup on the mother until we return to the bat hospital. The pup may be more settled, but we take the risk of a pup being bitten on the feet by the distressed mother. If we remove the pup, we tie coloured wool around the ankle of mother and baby for later identification. If the pup is removed from its’ mother, we wrap it in a cloth with a dummy in its’ mouth. We deal with any live maggots on the pup especially if in eyes.
5. Administer tick anti-toxin, about 2.5mls per adult bat mixed with 3-10mls of Hartmann’s fluids depending on the level of dehydration. We warm the mixture, more so if the bat is cold. A paralysed animal on the ground overnight can be cold. We usually inject the mix into the peritoneum with a 21 guage needle as the bat is more comfortable supine, but if the bat is pregnant we inject subcutaneously between the shoulder blades. The risk of infection with the peritoneal route needs to be managed. The tick anti-toxin can only neutralise toxin that is still circulating in the blood. Any toxin that has already bound in the tissues outside the blood vessels must resolve naturally or else continue to cause a deterioration in the animal.
6. We provide the bat with a comfortable supine lying down position and the opportunity to grasp on to something with its thumbs. Our lying-down cages have mesh on the top and front to allow this, but are solid on the sides so the bats cannot get themselves hooked into positions they cannot get out of. The cages are adjustable in height but mostly used at 15 cms. Sometimes they prefer to lie prone (on their stomachs) and we don’t interfere. In a very active bat we will sometimes confine them to a plastic basket because our cages are metal and can get noisy. In these bats watch that they cannot rub themselves raw on any surfaces. We rarely find it necessary to look for a sedative, mostly good handling and housing will keep the bats calm.
7. Offer small amounts (0.5 to 1ml) of diluted mango and apple juice, more if the swallow is normal. This gives the bat some sugar and conditions the bat to be comfortable with you as food is the reward.
7. Monitor the heart rate of the bat. Normally it is a strong 360 beats per minute, but this can drop to be very slow and irregular, or occasionally become extremely rapid. It can be difficult to distinguish between the rapid heart and the normal heart. Do not allow the bat to hang until the heart rate is at least 300 beats per minute.
8. Monitor closely but remember it is a wild animal and will be stressed by too much contact. There may be more than one tick and on admission it may still be climbing through the fur and be very difficult to find until it has engorged slightly. The stress of handling the bat too much at this stage must be weighed up against the risk of there being another tick. Sometimes I will leave this until the next day. Be aware of any deterioration in the bat that could suggest more tick toxin entering their system.
9. Common complications include facial nerve palsy and megaesophagus.
Facial nerve palsy results because the tick embedded itself near the nerve on the side of the face. Look for an inability to close the eye, making it essential to put eye lubricant into the eye regularly. Having tried a number of other brands, we recommend celluvisc. Without this the bat will develop a serious eye ulcer. At the first sign on any opacity in the eye see your veterinarian for an antibiotic ointment such as tricin.
Megaesophagus is the inability of the muscles around the oesophagus to move contents into the stomach and can make swallowing impossible. We try holding the bat vertically with it’s head up so that gravity can assist swallow but it is slow and not always successful.
It may be necessary to administer other drugs under the direction of a veterinarian. We do not have a resident veterinarian but are supervised by the local Tableland Veterinary Service. We have been involved in research with Prof Rick Atwell from the University of Queensland’s Department of Veterinary Sciences. He is one of Australia’s leading veterinary authority on tick paralysis. His visit in November 2001 led to improvements in our approach to the treatment of bats with tick paralysis as well as the publication of a paper in the Australian Veterinary Journal in June 2003. You can read it here Tick paper 2003
This bat is being assessed for tick paralysis – rectal temperature and ability to swallow. For this, we prefer to use a large towel rather than gloves for protection.
Drawings of the various stages of the life cycle of the paralysis tick, Ixodes holocyclus. Tick paralysis is usually caused by a single adult female tick, but every second year or so we get a bat outside of the usual tick season with tick paralysis caused by the nymph stage of the tick. They are always infested with large numbers of nymphs.
In a bad season we find up to 50 tick-paralysed bats a day. These bats, although found dead or euthanased are usually in good condition for researchers. These bats have contributed to a number of important research papers, notably by Drs Sam Fox and David Westcott.
Cluster of larval stage ticks
Severe pulmonary oedema