Following a report on Toxoplasmosis by the Advisory Committee on the Microbiological Safety of Food (ACMSF) and newspaper reports suggesting a high infection rate from cats, the British Veterinary Association has sought to reassure cat owners.
As quoted in the Veterinary Record (15 September 2012, p262), the BVA said ‘It is not known which the greater source of infection is, but anecdotal advice suggests that meat is likely to be more important than contact with cats’.
It added that, while the parasite posed a greater risk to pregnant women and immunocompromised individuals, ‘as with all infections, common sense and good personal hygiene reduces the risk significantly and there is no reason that families with, or those intending to have, children shouldn't have pet cats’.
Harvey Locke, the BVA's past-president, commented: ‘While the facts are true, the headlines in this story have been quite alarmist and we are very keen to reassure cat owners that the risks can be managed with good basic hygiene and common sense.
‘The biggest threat is to pregnant women and those who are immune-compromised, which we have known for some time. It is useful to reiterate that they should take extra care but there is no need for people to get rid of their pet cats or choose not to have cats as pets.’
The Feline Advisory Bureau (FAB) also sought to reassure cat owners, suggesting that the ‘scare stories’ were unjustified. In a statement, the charity acknowledged that cats were important in the lifecycle and transmission of T gondii and that ‘As a result, headlines and press articles appear from time-to-time suggesting the role of this parasite in human disease and often implicate cats as the major source of infection.
The committee notes that there is a lack of accurate data relating to the burden of disease and its economic impact in the UK, but comments that, on the basis of assessments made in the USA and the Netherlands, it seems reasonable to conclude that ‘the costs of the relatively small proportion of cases with severe disease make toxoplasmosis one of the most costly of gastrointestinal infections’.
The ACMSF notes that the main sources of infection are meat, other foods, water and the environment. Regarding meat, it says that there is a very small amount of data on meat contamination in the UK, and that methods should be developed to assess the number and distribution of viable tissue cysts in a range of edible tissues. The consumption of undercooked meat is likely to be an important risk factor for pregnant women and immunocompromised groups, the report says, and oocyst contamination of the environment is also an important risk factor for infection.
Turning to infection in the animals that serve as intermediate hosts of the parasite, the ACMSF says that seroprevalence data indicate that infection is most common in sheep, pigs and wild game. Cattle appear relatively resistant to infection. It suggests that further data on seroprevalence in farm animals would be useful in monitoring the effectiveness of control measures in animal husbandry and that testing a larger range of meat samples would help to identify the main sources of risk. It recommends that further studies are undertaken to establish seroprevalence in UK livestock species.
Discussing cats, the only definitive host in which sexual reproduction of the parasite occurs in the intestine, the ACMSF says it is thought that approximately 1 per cent of domestic cats are excreting oocysts at any one time and that, globally, the seroprevalence of toxoplasma in cats ranges from 5.4 per cent to 90 per cent, and is higher in wild and stray cats than domestic pets.
The ACMSF concludes that overall surveillance of cases of clinical toxoplasmosis in the UK is ‘suboptimal’ and that any current risk assessment has to be based mainly on estimates rather than reports of disease. It recommends that consideration is given to how the existing data gaps on both the prevalence and burden of disease can be addressed.
The FSA said that it would look carefully at the recommendations made in the report, and would publish a response in due course. The agency's chief scientist, Andrew Wadge, commented; ‘This thorough and detailed report points out key gaps in our knowledge about this parasite and suggests areas where more research is needed which will help us in estimating how much infection is due to food and which foods might be the highest risk. The report also suggests we look again at our advice to vulnerable groups and ensure that it reflects current scientific knowledge.’
This review overlooks many contacts with pets and companion animals as well as animals in exhibitions and contests. Therefore we must consider how much animals are treated as an animal of respect and how much as a living toy for our own satisfaction. We would do best to cut the population of human consumers of animals and give much better treatment to those that are taken for granted. This will have more effect than attention to meat and we should take particular care over animals’ place in our lives.
For instance, cuddling of cats by famous film stars and close companionship with animals should arouse chemists’ and vets’ disquiet and objection. But there must be a place for police dogs, guide dogs and many other animals, whose well-being must be carefully considered. This is a situation that deserves much greater care from the veterinary profession and ‘animal lovers’.