Risk factors for infection

In Norway, a case control study has been performed for identification of preventable risk factors for Toxoplasma infection during pregnancy (Kapperud et al. 1996). The case patients were identified through a serologic prenatal screening program. Pregnant women with serologic evidence of recent primary Toxoplasma infection (63 cases) were compared with 128 seronegative controls matched by age, stage of pregnancy, expected date of delivery, and geographic area. Multivariate analyses indicated that the following factors were independently associated with an increased risk of Toxoplasma infection:

a eating raw or undercooked minced meat products (OR = 4.1); b eating unwashed, raw vegetables, or fruits (OR = 2.4); c eating raw or undercooked mutton (OR = 11.4); d eating raw or undercooked pork (OR = 3.4); e cleaning the cat litter box (OR = 5.5); and f washing the kitchen knife infrequently after preparation of raw meat prior to handling of other food items (OR = 7.3).

In an univariate analysis travelling to countries outside Scandinavia was identified as a significant risk factor (Kapperud et al. 1996). However, this was not due to the travel itself, but related to the different modes of infection. Even from Sweden travelling to southern Europe or areas with a significantly higher prevalence is regarded as a risk factor (Evengard et al. 1997). Thus, in the Nordic countries seronegative pregnant women should be advised to stay within the region during pregnancy, especially since preventive measure to avoid Toxoplasma infection may be difficult to apply abroad. Although attempts to avoid undercooked meat and unwashed or raw vegetables, and fruits would reduce the risk of infection, most meals taken while travelling are usually eaten in hotels or restaurants where the traveller has no influence on kitchen hygiene and food handling practices (Kapperud et al. 1996). The risk factors connected to consumption of raw or undercooked meat are directly related to the seroprevalence of Toxoplasma infection in meat-producing animals. In Norway, the highest prevalence of Toxoplasma antibodies has been found in sheep (18%), followed by cattle (5%) and pigs (2.6%) (Skjerve et al. 1996). In Sweden, similar seroprevalence (19%) was found in different flocks of sheep (Lunden et al. 1992).

Some people may have occupations that increase their risk of infection. These include slaughterhouse workers and greenhouse workers. Actually, in Denmark, these workers were found to have remarkably high Toxoplasma antibody prevalence (Lings et al. 1994). In other studies veterinarians and other humans with intimate contact with animals have high antibody prevalence (Asburn 1992). Daily contact with cats or living in a neighbourhood with cats does not represent a risk factor according to a Norwegian study; however, daily contact with kittens less than 1 year of age or living in a household with a cat that uses a cat litter box and especially cleaning the cat litter box were associated with increased risk (Kapperud et al. 1996). Contamination of hands after contact with cat faeces or infected soil, when gardening, may also be a potential hazard (Frenkel 2000).

0 0

Post a comment