Britons are reputed to be a nation of animal lovers and many a heated dispute has revolved around whether cats or dogs make better pets. Recently the dog lovers have been given a boost by reports that cats can be harmful to humans. While it has been known for some time that toxoplasmosis can be spread by cats, the knowledge that it is not just pregnant women and those who have compromised immunity that are at risk, is fairly recent. The number of people affected is greater than previously believed and the degree of harm is wider than thought.
What is toxoplasmosis?
Toxoplasmosis is a parasitic infection that is usually transmitted by cats, the only animal in which the parasite can mature and reproduce.
So how do people acquire toxoplasmosis? The causative agent is the parasite Toxoplasma gondii. This has a two stage life cycle, the first stage being in cats who act as the primary host. An infected cat sheds oocysts of the parasite in its faeces. If a human (or other mammals or birds) take in these oocysts through eating contaminated fruit or vegetables, handling cat litter and then eating without washing their hands, or eating improperly cooked meat from an infected source, then that person becomes the parasite’s secondary host and is infected. The parasite enters the blood stream from the intestines and is carried round the body.
According to the BBC it is estimated that in the UK 350,000 people a year become infected with toxoplasmosis. Many people, however, show no symptoms or suffer only a mild ‘flu like illness'. Once infected, lifelong immunity develops. It has been known for a while that if pregnant women become infected, the parasite can cross the placenta and foetal harm can occur, resulting in either a miscarriage or a blind or brain damaged baby. Also, infection may have serious consequences for people with weakened immunity.
Recent research at Leeds University suggests that there are other harmful effects of toxoplasmosis which have hitherto not been publicly recognised. Although the research was carried out on rodents it is thought that the effects are similar in humans. Toxoplasma gondii causes the production of much higher levels than normal of the chemical messenger dopamine in infected brain cells. Dopamine relays messages to the brain relating to movement, cognition and behaviour, and changes in dopamine levels are associated with illnesses such as schizophrenia, depression and Parkinson’s disease. Research also links Toxoplasmosis to schizophrenia. It has been found that the incidence of toxoplasmosis among people with schizophrenia is twice that found in people without schizophrenia.PreventionSo how can you avoid acquiring this particular nasty parasite? Much of the measures required are common sense and apply to cat owners and non-cat owners alike. Fruit and vegetables, which you plan to eat raw, should be thoroughly washed. Meat needs to be properly cooked. If you do own cats, try and keep them out of your vegetable plot. If you use litter trays, then put on gloves when you clean them and wash your hands afterwards. It is a good idea to encourage children to wash their hands after handling cats and certainly before they eat.
The Advisory Committee on the Microbiological Safety of Food (ACMSF), which advises the Food Standards Agency, has called for further research to look at the prevalence of toxoplasmosis in UK livestock and food. The Food Standards Agency is to review its guidelines in relation to the condition. Some experts would like to see toxoplasmosis made a notifiable disease in England, Wales and Northern Ireland as it is in Scotland. In that way better statistics could be gathered to inform future policies and plans.
In conclusion, with care this illness can be avoided. While having cats does increase your risk, it should also be remembered that they also confer health benefits on their human friends. Stroking a cat has been shown to lower the blood pressure of the stroker. In short, there is no need to get rid of your cats but basic hygiene is a good idea.