The wet summer has created ideal conditions for footrot in sheep and many have had to spend extra time paring their sheep's hooves and running them through a footbath containing chemicals to kill off the bacteria that cause the infection.

Footrot is reckoned to cost British farmers between £25 and £30m a year and that has led to the development of experimental programmes to breed sheep that are resistant to the disease.

Researchers have established that there is a wide range of susceptibility to footrot in the progeny of different rams, where some breed lambs that aren't affected while others have up to 25 per cent succumbing to the disease.

In New Zealand they have developed a footrot test that can identify more tolerant or resistant animals and there are now millions of sheep bred out of rams that have been DNA-screened for footrot.

Arable farmers have already led the way in breeding crop varieties with disease resistance.

There can be little doubt that breeding animals that are resistant to disease is far better than being dependent on expensive chemicals and drugs that can lose their efficacy if not used properly.

Currently, control of parasitic infections relies almost exclusively on anti-parasitic drugs, which are not a sustainable option due to the increasing development of drug resistance among parasites, as well as consumer concerns about chemical residues in food.

We have all read the publicity surrounding the development of bugs that are resistant to antibiotics, but farmers are experiencing a similar problem with the drugs they use to control stomach worms in their livestock.

Scientists have developed some very good wormers, or anthelmintics, that for years have effectively killed off those parasites. Ever since I was a lad it was accepted good practice to regularly dose cattle and sheep with these wormers to keep them healthy and growing at their maximum potential.

About twenty years ago we became aware of stomach worms in sheep developing resistance to various groups of anthelmintics in New Zealand that rendered them ineffective - we now have the same problem in the UK.

Scientists believe that a viable alternative to anthelmintics is to develop vaccines to help prevent disease and reduce the impact of parasite infection in food animals, providing a more sustainable and safer approach to disease control.

Vaccine development against multi-cellular parasites is a major challenge in human and veterinary medicine, with only two commercial veterinary vaccines currently available. Despite the hurdles, a number of proto-type multi-cellular parasite veterinary vaccines have shown promise recently.

I never cease to be amazed at the tenacity for life shown by the parasites, pests and diseases that attack crops and livestock. Despite our best efforts to kill them off, they always seem to bounce back.

Scientists have developed genetically modified (GM) varieties of crops that are resistant to pests and diseases, but it seems that there are just about always a small proportion of pest and disease populations that can overcome a plant's defences.

When you sow a GM crop that is resistant to a disease or pest it will kill off 99.9 per cent, but the remaining 0.1 per cent rapidly reproduces to develop a new strain against which the plant has no defences. As a result, years of research and development, never mind the vast amounts of money invested by plant breeders, is wasted.

To overcome that problem, farmers using GM seed now mix it with a small amount of ordinary seed from non-GM plants of the same variety. That way, those organisms that can overcome the GM crop's resistance will interbreed with the ordinary strains that are thriving on the non-GM plants, thus slowing down the development of resistant strains and prolonging the useful life of the GM variety.

Using the same principle, many livestock farmers alternate the types of wormers they use every season to slow down the development of anthelmintic-resistant stomach worms.

Wouldn't it be nice to have easy-care sheep that were immune to stomach worms as well as resistant to scab, footrot and fly-strike?

We should never forget that sick animals cost the farmer money.

An extreme example was the 2001 outbreak of foot-and-mouth disease. During the epidemic 4.2m animals were slaughtered on 1,051 farms. In addition, there was a welfare cull of just under a million sheep, 228,000 pigs, 139,500 cattle and 1,365 goats giving a total killed of 5.57m. The total cost to the taxpayer was more than £8bn.