Dr Sarah Zito, BVetMed MANZCVS PhD
Q: My friend’s cat was recently diagnosed with hyperthyroidism and I am worried that my cat Tarzan may have the same problem. How would I know and, if he does have it, can it be treated?
A: Hyperthyroidism is a very common disorder of older cats, in which their thyroid glands become overactive and produce excessive amounts of thyroid hormones. These hormones help control the body's metabolic rate and are also involved in the regulation of many body processes. Too much of the thyroid hormones can cause cats to become very ill. Cats with hyperthyroidism tend to lose weight despite having an increased appetite and eating more food. They often also have increased thirst and drink more; increased activity, restlessness or irritability; an increased heart rate; and a poor and scruffy looking hair coat. Some cats get diarrhoea and/or vomiting, and some may pant when they are stressed (which is unusual in cats). Occasionally a cat with hyperthyroidism will show non-typical clinical signs such as generalised weakness, lethargy, and loss of appetite but this is far less common.
If Tarzan is showing signs such as those described above you should take him to your veterinarian. Based on the clinical signs and a physical examination your veterinarian will likely be able to tell you if he or she suspects that Tarzan might be hyperthyroid. A blood test to measure the level of thyroid hormones will be needed to confirm the diagnosis. Sometimes additional tests may be needed. Other tests will likely be performed at the same time to assess other potential concurrent problems (such as kidney disease); there are often abnormalities in other laboratory tests in hyperthyroid cats (particularly an increase in liver enzymes is common). Your veterinarian will be able to advise you on what these mean and whether further investigation is needed.
It is really important that cats with hyperthyroidism are diagnosed and treated appropriately. When hyperthyroidism is uncontrolled it can have important negative consequences in the body including damage to the heart (eventually causing heart failure if untreated) and high blood pressure (which can damage organs such as the eyes, kidneys, heart, and brain).
The good news is that the majority of cats that develop hyperthyroidism can be treated very successfully and make a complete recovery, with complete reversal of all the signs of hyperthyroidism. There are a number of different options available including medical management with anti-thyroid drugs, surgery to remove the overactive thyroid gland, dietary therapy, and radioactive iodine therapy. Each option has its pros and cons and your veterinarian will be able to advise you which is the best option for your cat and circumstances.
Q: Are my cat and dog at risk of poisoning if I use rat bait around my house?
A: Yes. Rodents, humans, dogs and cats are all at risk from rodenticides (rat bait). Rodenticides can affect any mammal and birds in the same way as they affect a rodent.
Most rodenticides are anticoagulants (e.g. warfarin, brodifacoum, bromadiolone, and flocoumafen); these interfere with the ability of the blood to clot and lead to haemorrhage and death from blood loss. There are also some rodenticides that work differently to the anticoagulant poisons (such as cholecalciferol and zinc phosphide).
Rodenticide baits are made to attract animals; non-target species (i.e. animals other than the rodents that are the target of the poison such as pets and wildlife) may also be attracted to the baits and ingest the poison, even children are at risk. Non-target species can be poisoned by ingesting the poison itself or by eating another animal that has ingested the poison. So, if for example a cat could get secondary poisoning from eating a rat that had eaten a brodifacoum (anticoagulant poison) bait. Anticoagulant poisoning can lead to uncontrolled bleeding in any part of the body, but the bleeding is often internal and so the poisoned animal may show signs other than external bleeding. These signs might include: difficulty breathing, weakness, lethargy, coughing, vomiting, blackened tarry faeces, pale mucous membranes, bleeding from the gums, seizures, bruising, shaking, abdominal distention, and pain. It can take some days for signs to develop following exposure.
As well as being a danger to children, pets, and wildlife, all of these poisons are a very cruel way to kill rodents. To safeguard children, pets, and wildlife and avoid cruelty to rodents other, more humane, methods of rodent control should be used rather than rodenticides, where at all possible.
Q: We recently had two Guinea Pigs, Peanut and Flossie, join our family. Somebody told me that for Guinea Pigs to be healthy, it is really important that they have enough vitamin C. Can you tell me why and what I can do to make sure my GPs get enough vitamin C?
Every animal has a requirement for certain essential nutrients; they need a regular dietary supply of these essential nutrients, which they are unable to produce on their own. In guinea pigs and primates, including humans, one key essential nutrient is vitamin C (this is why many sailors historically developed scurvy because they did not have vitamin C containing fresh fruit and vegetables to eat on their long sea voyages). Vitamin C is vital for the healing of wounds, and the normal development and maintenance of skin, joints, and mucousal surfaces (such as the gums). A deficiency of vitamin C can also affect the function of the immune system and make the body more vulnerable to other diseases, infections, and conditions. If a GP has vitamin C deficiency he/she may have a rough hair coat; be lethargic, weak, and/or reluctant to walk; and have a poor appetite, diarrhoea, swollen feet or joints, or haemorrhages and ulcers on his/her gums or skin. The bleeding into muscle, the intestines, and other tissues that is associated with vitamin C deficiency makes this a painful condition.
To avoid vitamin C deficiency in your GPs they should be fed plenty of fresh fruit and leafy green or coloured vegetables every day. Vitamin C is often included in special GP diets but these, and vitamin C liquid supplements (which are added to GPs’ drinking water), are not reliable sources of vitamin C because this essential nutrient is a relatively unstable compound and breaks down or oxidises quickly. Therefore, to make sure they get enough vitamin C, GPs should always have plenty of fresh fruit and vegetables as a large proportion of their diet. Fresh leafy green vegetables (such as kale, parsley, and spinach) are a good source of vitamin C for GPs and you can get even more into their diet by adding small quantities of vitamin C rich food such as oranges, kiwi fruit, and capsicum.