Showing papers by "Gereon Schares published in 2018"

Human impact on the diversity and virulence of the ubiquitous zoonotic parasite Toxoplasma gondii.

Abstract: A majority of emerging infectious diseases in humans are zoonoses. Understanding factors that influence the emergence and transmission of zoonoses is pivotal for their prevention and control. Toxoplasma gondii is one of the most widespread zoonotic pathogens known today. Whereas only a few genotypes of T. gondii dominate in the Northern Hemisphere, many genotypes coexist in South America. Furthermore, T. gondii strains from South America are more likely to be virulent than those from the Northern Hemisphere. However, it is not clear what factor(s) shaped modern-day genetic diversity and virulence of T. gondii Here, our analysis suggests that the rise and expansion of farming in the past 11,000 years established the domestic cat/mouse transmission cycle for T. gondii, which has undoubtedly played a significant role in the selection of certain linages of T. gondii Our mathematical simulations showed that within the domestic transmission cycle, intermediately mouse-virulent T. gondii genotypes have an adaptive advantage and eventually become dominant due to a balance between lower host mortality and the ability to superinfect mice previously infected with a less virulent T. gondii strain. Our analysis of the global type II lineage of T. gondii suggests its Old World origin but recent expansion in North America, which is likely the consequence of global human migration and trading. These results have significant implications concerning transmission and evolution of zoonotic pathogens in the rapidly expanding anthropized environment demanded by rapid growth of the human population and intensive international trading at present and in the future.

Detection and dissemination of Toxoplasma gondii in experimentally infected calves, a single test does not tell the whole story.

Abstract: Although the detection of Toxoplasma gondii in bovine tissues is rare, beef might be an important source of human infection. The use of molecular techniques, such as magnetic capture qPCR (MC-qPCR), in combination with the gold standard method for isolating the parasite (mouse bioassay), may increase the sensitivity of T. gondii detection in infected cattle. The risk of transmission of the parasite to humans from undercooked/raw beef is not fully known and further knowledge about the predilection sites of T. gondii within cattle is needed. In the current study, six Holstein Friesian calves (Bos taurus) were experimentally infected with 106 T. gondii oocysts of the M4 strain and, following euthanasia (42 dpi), pooled tissues were tested for presence of the parasite by mouse bioassay and MC-qPCR. Toxoplasma gondii was detected by both MC-qPCR and mouse bioassay from distinct pools (100 g) of tissues comprising: liver, tongue, heart, diaphragm, semitendinosus (hindlimb), longissimus dorsi muscle (sirloin) and psoas major muscle (fillet). When a selection of individual tissues which had been used for mouse bioassay were examined by MC-qPCR, parasite DNA could only be detected from two animals, despite all calves showing seroconversion after infection. It is apparent that one individual test will not provide an answer as to whether a calf harbours T. gondii tissue cysts. Although the calves received a known number of infectious oocysts and highly sensitive methods for the detection of the parasite within bovine tissues were applied (mouse bioassay and MC-qPCR), the results confirm previous studies which report low presence of viable T. gondii in cattle and no clear predilection site within bovine tissues.

Naturally acquired bovine besnoitiosis: Disease frequency, risk and outcome in an endemically infected beef herd

Abstract: The recent spread of bovine besnoitiosis warrants further epidemiological investigations to improve the knowledge on disease development. Thus, a 4-year longitudinal open cohort study was conducted in the first German cattle herd naturally infected with Besnoitia besnoiti. At seven herd-visits between 2008 and 2012, fourteen breeding bulls (>1.5years) and 131 females (>1year) were examined clinically and serologically. In females, clinical and serological prevalences, incidence and remission rates were determined. In addition, the association of age, antibody levels and number of visible parasitic cysts with clinical and serological outcome was investigated. The seroprevalence (89.4%-100%) and serological incidence rate (140.5 per 100 animal-years) were considerably higher than the clinical prevalence (23.5%-36.6%) and clinical incidence rate (16.7 per 100 animal-years). Of 33 new clinical and 12 new serological cases, only 6.7% (3/45) attracted attention with clinical signs of acute bovine besnoitiosis. The apparent serological remission rate (1.9 per 100 animal-years) was considerably lower than the clinical remission rate (37.3 per 100 animal-years). A median cyst score of <1 and mean immunofluorescent antibody test (IFAT) titre of 1,600 over the entire observation period was significantly associated with a negative clinical outcome at the end. Overall cyst score was not significantly associated with serological outcome and age had no significant influence on clinical and serological outcome. Within 4years, there was a significant reduction in cyst scores and IFAT titres in the same animals, leading to eight clinically and serologically negative animals in the end. Two initially negative animals achieved clinical and apparent serological remission in about 2.5years. In bulls, the time between herd entry and seroconversion was 7-30months and the serological incidence rate was nearly identical to the rate in females (142.0 per 100 animal-years). This shows that a high B.besnoiti prevalence leads to infection of bulls within a short time period.

Seroprevalence of Neospora caninum-specific antibodies in German breeding bitches.

Abstract: Neospora caninum is an intracellular obligate apicomplexan parasite responsible for multisystemic lesions in dogs. Being definitive hosts and reservoirs, dogs excrete environmentally resistant oocysts. Breeding bitches represent a susceptible dog group and infected bitches may spread this parasite through transplacental transmission. A total of 218 serum samples of German breeding bitches were collected to determine the presence of N. caninum. Antibodies were detected in 16 (7.33%) bitches using a commercial indirect enzyme-linked immunosorbent assay (ELISA). Immunoblotting analysis confirmed all seropositive samples detected by ELISA, proving that the animals were infected with N. caninum. The owners were interviewed regarding breed, age, environment, type, vaccine status, feeding habits and the presence of reproductive disorders. Seropositive animals were between the ages of two to seven years; three of them were kept in kennels while the others were household dogs, one of which was additionally a hunting dog. Owners of four seropositive bitches reported one gestation, while multiple pregnancies had been recorded for the other twelve bitches. Fourteen bitches were regularly vaccinated and six were fed with fresh raw meat. Although the results confirmed a low incidence of N. caninum seropositive German breeding bitches, further epidemiological and surveillance studies are required to complement our findings regarding the current situation of neosporosis in this specific canine population of Germany.

Neospora caninum-specific antibodies in free-ranging white-lipped peccaries ( tayassu pecari) from the peruvian amazon: detection of antibodies in serum and evaluation of indirect fluorescent antibody test with heterologous secondary antibody.

Abstract: Neospora caninum is a coccidian parasite originally reported in dogs and widely prevalent in numerous species of wild and domestic animals and has as definitive hosts some species of canids. The white-lipped peccary (WLP) (Tayassu pecari) is a Tayassuidae mammal, found from Mexico to south of Brazil and north of Argentina. It is a game species with great economic importance in the Peruvian Amazon. Blood samples from 101 WLPs were collected from near or within three different conservation reserves located in the southeastern region of the Peruvian Amazon. For the detection of antibodies against N. caninum, indirect fluorescent antibody tests (IFAT) were performed using collared peccary (Pecari tajacu) and swine (Sus scrofa domesticus) heterologous secondary antibodies. For both IFAT tests, the cutoff was 1:50. Positive samples were titrated by a two fold serial dilution. In addition to IFAT, samples were also analyzed using an immunoblotting test (IB) with anti-swine conjugate. To confirm the viab...