Immunodiagnosis of primary Toxoplasma gondii infection in sheep by the use of a P30 IgG avidity ELISA

Abstract.: Toxoplasma gondii is a protozoan parasite with a worldwide distribution. In both sheep and humans, if the parasite is encountered during pregnancy, fetal infection and abortion can occur. Therefore, Toxoplasma infection in sheep has a major economic impact upon sheep farming. Clinically, there is a need to distinguish recent (acute) infections from longstanding (chronic) infections. However, current serological techniques, such as detection of anti-T. gondii IgG, cannot discriminate between acute and chronic infections. Increasing immunoglobulin avidity is a good determining factor of how recent an infection is. In this study, we describe the application and validation of a T. gondii IgG avidity ELISA, based on the use of an affinity-purified, native T. gondii P30 antigen. The assay was used to examine sera from eight sheep experimentally infected with T. gondii and found that all seroconverted within 21days post-infection (p.i.), beginning with avidities that were initially low but that increased over time, with all sheep reaching high IgG avidity within 10weeks p.i. In addition, sera from clinically healthy but T. gondii-seropositive lambs and ewes and seropositive ewes with a history of abortion were also subjected to a preliminary serological investigation. High IgG avidities were found in 80% of the seropositive lambs, in 90% of the clinically healthy ewes and in 97% of the ewes with abortion problems. These findings indicate that the animals had most likely contacted the parasite a longer time ag

Toxoplasma gondii in animals used for human consumption

Food-borne toxoplasmosis in humans may result from exposure to different stages of Toxoplasma gondii, in particular from the ingestion of tissue cysts or tachyzoites contained in meat, primary offal (viscera) or meat-derived products of many different animals, or the ingestion of sporulated oocysts that are contained in the environment and may contaminate food and water. Although the potential for transmission of the parasite to humans via food has been known for several decades, it is not known which routes are most important from a public health point of view. It is likely that transmission of the parasite to humans is influenced not only by the potential contamination of various food sources, but also by the individual behaviour of consumers in different ethnic groups and geographical regions. Most current methods for detection of T. gondii in meat-producing animals, in products of animal origin, or in the environment are insufficient because they do not allow quantification of infectious stages. Hence, most studies report only qualitative data from which it is difficult to assess the true risk of infection in individual cases. There is a need for quantitative data so that efficient strategies to reduce food-borne transmission of T. gondii to humans can be developed

Seroprevalence of Babesia Infections in Humans Exposed to Ticks in Midwestern Germany

Babesiosis is considered to be an emerging tick-borne disease in humans worldwide. However, most studies on the epidemiology of human babesiosis to date have been carried out in North America, and there is little knowledge on the prevalence of infection and frequency of disease in other areas. The aim of this study was to investigate the prevalence of Babesia infections in a human population in Germany. A total of 467 sera collected between May and October 1999 from individuals living in the Rhein-Main area were tested for the presence of immunoglobulin G (IgG) and IgM antibodies to antigens of Babesia microti and Babesia divergens by indirect fluorescent-antibody (IFA) tests. These sera were derived from 84 Lyme borreliosis patients suffering from erythema migrans, 60 asymptomatic individuals with positive borreliosis serology, and 81 individuals with a history of tick bite. Cutoff values for discrimination between seronegative and seropositive results in the IFA tests were determined using sera from 120 healthy blood donors and 122 patients suffering from conditions other than tick-borne diseases (malaria, n = 40; toxoplasmosis, n = 22; syphilis, n = 20; Epstein-Barr virus infection, n = 20; and presence of antinuclear antibodies, n = 20). The overall specificities of the IFA tests for B. microti and B. divergens were estimated to be ≥97.5%. Positive IgG reactivity against B. microti antigen (titer, ≥1:64) or B. divergens antigen (titer, ≥1:128) was detected significantly more often (P < 0.05) in the group of patients exposed to ticks (26 of 225 individuals; 11.5%) than in the group of healthy blood donors (2 of 120 individuals; 1.7%). IgG antibody titers of ≥1:256 against at least one of the babesial antigens were found significantly more often (P < 0.05) in patients exposed to ticks (9 of 225) than in the control groups (1 of 242). In the human population investigated here, the overall seroprevalences for B. microti and B. divergens were 5.4% (25 of 467) and 3.6% (17 of 467), respectively. The results obtained here provide evidence for concurrent infections with Borrelia burgdorferi and Babesia species in humans exposed to ticks in midwestern Germany. They also suggest that infections with Babesia species in the German human population are more frequent than believed previously and should be considered in the differential diagnosis of febrile illness occurring after exposure to ticks or blood transfusions, in particular in immunocompromised patients

Prevalence of specific IgG-antibodies against Toxoplasma gondii in domestic turkeys determined by kinetic ELISA based on recombinant GRA7 and GRA8.

International audienceThe protozoan parasite Toxoplasma (T.) gondii is one of the most common zoonotic infectious agents worldwide. Besides its sexual reproduction in cats, T. gondii can also infect a wide spectrum of other warm-blooded animals. These include animals used for human consumption such as pigs or chickens. Nevertheless, the role of turkeys for the epidemiology of T. gondii infections has not been studied thoroughly. We have established a kinetic ELISA (KELA) for the detection of T. gondii-specific IgG antibodies in turkey serum samples. The test is based on the recombinant dense granule antigens GRA7 and GRA8. These proteins were used as an antigen mixture at a concentration of 0.13 μg per well. The overall sensitivity of the assay was between 92.6% and 100% and the specificity ranged from 78.1% to 100%, depending on the method used to calculate these parameters. Using this KELA we examined 1913 turkey serum samples from 14 turkey farms from different areas of Germany. From these sera, 387 produced a signal in the KELA, corresponding to a true seroprevalence of up to 20.2%. The seropositivity rate in individual fattening cycles at individual farms ranged from 0.0% to 77.1%, whereas the rates were highly variable within the individual farms and individual fattening cycles. Consequently, conditions of animal husbandry could not be associated with particular seroprevalence rates. Although seropositivity cannot be linked directly to infectious tissue cysts in the muscle tissue of commercially produced turkey meat, we state that there is a potential risk of being infected by consuming turkey meat products that were not heat treated