It seems clear that like temperament, some aspects of health and illness have a familial basis, and can be passed from generation to generation. When breeding for healthy rats there are various aspects to consider. But first let me say that it would be an unreasonable expectation to assume that a healthy rat will never be ill in any way, and will live a good, long life without a single sniffle or sneeze. That would be wonderful, but in reality all animals will suffer from minor illness during their lives, and rats are no exception.

With that little sprinkling of realism out of the way, I want to look at what breeders can do to aim for health and longevity in their rats. To do that I think we need to look at the most common conditions that rob a rat of it's health, and ultimately its life.

Serious infection can come in many forms, some of which can be life threatening to a rat. Illnesses such active mycoplasma, streptococcal infection and pasteurella can cause morbidity and early death in affected animals. The answer to why some rats develop respiratory infection easily, while others (even living in the same cage) do not, seems to lie in the strength of the individual rats immune system. Those with a weaker system will be unable to resist infection in the same way, or will succumb more rapidly to infective illness. It also seems that the ability to resist these infections is to some degree decided by inheritance. This is not clear cut. A rat's immune system seems to be affected by stress - including environmental stress (dirty cages, home and companion changes etc), and a stressed rat is a rat vulnerable to infection. Immunity can also be boosted by good diet, and certain herbs such as garlic and echinacea. But in general, susceptibility to illness such as active mycoplasma does run through generations in a line of rats. When breeding for health it is wise never to breed from a rat who has shown itself to be prone to infection, or is showing early signs of active mycoplasma (chronic sneezing, transient noisy breathing and excessive porphyrin production).

The more difficult aspects of breeding for health centre around longevity, and those illnesses that occur later in a rats life, certainly well after it has already been used for breeding. Many other illnesses have been found to have a familial influence, and this is true of most of those that affect rats as they age. The most common health problems seen in older rats are tumours, respiratory illness, kidney disease, heart disease, strokes and degenerative disease of the spine. Obviously the only way to be certain of the 'health history' of your rat's ancestors is to own them, or to get them from somebody who is willing to share that information with you.

If you want to breed for health (and longevity), you will need to find out as much as possible about the ancestors of the rats you own. While a rat (like any other animal) has to eventually die of something, diseases that will often lead to an early death should be actively bred away from. The most obvious of these is tumours, and any line that is repeatedly throwing up tumours in rats under 18 months of age is highly suspect. The obvious problem is that until a line is well established many of the health problems may not have come to light. The breeder then has a responsibility to pass on any information she gains about the health of the line to any other owners who might be affected, especially those who have purchased kittens from the line as potential breeding stock. She would also be wise to maintain contact with all those who have bought kittens from her so that she can gather relevant information should problems occur.

Improving the health of fancy rats in the long term is in my opinion dependant upon three interplaying factors
1. Improving understanding about rat diet, so that all rats have the best possible nutrition.
2. Ensuring that rats are kept in appropriate conditions and receive quality care.
3. Breeding only from healthy rats who come from lines where serious illness is uncommon. This can only be achieved if breeders are willing to be open about health problems and share information with each other.

A final cautionary note.
Good breeders, breeding healthy, long-lived rats are not immune from producing some rats with health problems. Even the best pairing from a health point of view can throw up the odd rat with serious or chronic illness. We should do everything we can to avoid a culture of blame, otherwise breeders will feel forced to hide health problems, and that will only serve to threaten the overall health of the fancy rat population. Better to accept the inevitability of illness, and foster openness between breeders that allows for information to be shared, and the courage to stop lines when it becomes obvious that this is necessary.

Alison Campbell