From the RSPB website.
Are cats causing bird declines?
Estimates of how many creatures are killed by cats each year vary significantly.
The most recent figures are from the Mammal Society, which estimates that the UK's cats catch up to 275 million prey items a year, of which 55 million are birds. This is the number of prey items that were known to have been caught; we don't know how many more the cats caught, but didn't bring home, or how many escaped but subsequently died.
The most frequently caught birds, according to the Mammal Society, are probably (in order) house sparrows, blue tits, blackbirds and starlings.
Despite the large numbers of birds killed, there is no scientific evidence that predation by cats in gardens is having any impact on bird populations UK-wide. This may be surprising, but many millions of birds die naturally every year, mainly through starvation, disease, or other forms of predation. There is evidence that cats tend to take weak or sickly birds.
It is likely that most of the birds killed by cats would have died anyway from other causes before the next breeding season
We also know that of the millions of baby birds hatched each year, most will die before they reach breeding age. This is also quite natural, and each pair needs only to rear two young that survive to breeding age to replace themselves and maintain the population.
It is likely that most of the birds killed by cats would have died anyway from other causes before the next breeding season, so cats are unlikely to have a major impact on populations. If their predation was additional to these other causes of mortality, this might have a serious impact on bird populations.
Those bird species that have undergone the most serious population declines in the UK (such as skylarks, tree sparrows and corn buntings) rarely encounter cats, so cats cannot be causing their declines. Research shows that these declines are usually caused by habitat change or loss, particularly on farmland.
Gardens: important habitat
Populations of species that are most abundant in gardens tend to be increasing, despite the presence of cats. Blue tits, for example, the second most frequently caught birds, have increased by over a quarter across the UK since 1966. Of the birds most frequently caught by cats in gardens, only two (house sparrow and starling) have shown declines in breeding population across a range of habitats during the last six years.
Gardens may provide a breeding habitat for at least 20% of the UK populations of house sparrows, starlings, greenfinches, blackbirds and song thrushes four of which are declining across the UK. For this reason it would be prudent to try to reduce cat predation, as, although it is not causing the declines, some of these species are already under pressure.
Cat predation can be a problem where housing is next to scarce habitats such as heathland, and could potentially be most damaging to species with a restricted range (such as cirl buntings) or species dependent on a fragmented habitat (such as Dartford warblers on heathland).
Some sensible facts about cats killing animals. 275million a year of that 55 million were bird kills ,that leaves 220 million which were mice ,rats ,shrews etc . Without cats we would have an extra billion rats , mice etc in the uk over 5 years , that is working on just mathematics , in reality if the cats were all kept in for 5 years , what do you think the rodent population would increase by , the way rats produce young i couldn't hazzard a quess
as to the sum, and as the rodent is the one who passes the infection on to the cat , i believe the number of cases of children getting toxoplazma would rise if cats were confined to barracks.
Facts on toxoplazma.
The most common zoonosis to cause concern is Toxoplasma, especially for pregnant ladies. The details are complex, but the reality is Toxoplasma is a small parasite that lives in the muscle of sheep, rabbits, rats and kangaroos and multiplies in the intestines of young cats if they eat that meat.
It is spread to the herbivores out on the fields and pastures contaminated by feral cats' faeces. Only young cats pass contaminated faeces usually, so once past the kitten stage, very few cats will pass on the eggs (called oocysts) which can infect other mammals, including humans. The upshot of this is that most people in Australia become infected with Toxoplasma oocysts by gardening without gloves, and in France, by eating undercooked lamb or rabbit.
Being infected with the oocysts is only a problem for pregnant women if they have not been in contact with the Toxoplasma oocysts before they got pregnant, because then the baby gets infected as well, with debilitating effects.
So, because cat faeces are involved, it is only right that pregnant women should not handle cat faeces. However, bear in mind it takes a few days for the oocysts to develop enough in the faeces for them to become infective, so daily cleaning of litter trays removes that risk as well.
Toxoplasma oocysts do not hang around on the cat’s coat either (in fact their skin has 30 percent fewer bacteria on it than yours because of all that grooming!). So, the risk to an owner of an adult cat with a regularly cleaned litter tray is low. Interestingly, vets and vet nurses have no higher levels of exposure to Toxoplasma than the general population, which would indicate that cats are actually a low-risk source of infection.
Precautions for women then, are to use gloves when gardening (and wash hands after handling any soil or sand outside) and to cook lamb, rabbit and kangaroo meat well, and wash hands after handling those meats raw. Pretty simple really.
Blood testing your cat for Toxoplasma is not going to be very revealing, as most cats will have been exposed and be immune from quite a young age. The ideal is to actually have both expectant mother and cat having high levels of toxoplasma antibodies prior to the pregnancy! That way, no one is going to be infected!