Kristin Wear Prestrud

Direct high-resolution genotyping of Toxoplasma gondii in arctic foxes (Vulpes lagopus) in the remote arctic Svalbard archipelago reveals widespread clonal Type II lineage

Characterization of Toxoplasma gondii genotypes in hosts living in remote, isolated regions is important for elucidating the population structure and transmission mode of this parasite. Herein, we report the results of direct genotyping of T. gondii in brain tissue of arctic foxes (Vulpes lagopus) from the remote, virtually cat-free, high arctic islands of Svalbard. DNA extracts from brains of 167 seropositive arctic foxes (including four cases of fatal toxoplasmosis) and 11 seronegative arctic foxes were genotyped at 10 loci (SAG1, SAG2, SAG3, BTUB, GRA6, L358, c22-8, c29-2, PK1, and Apico) using the polymerase chain reaction-restriction fragment length polymorphism method. Of the 167 samples from seropositive foxes (including toxoplasmosis cases), 31 were genotyped at all 10 loci and 24 were genotyped at four to nine loci. To ensure confidence in T. gondii strain genotyping, samples for which less than four loci were genotyped were not considered positive. None of the 11 samples from seronegative foxes was positive for the 10 markers. Of the 55 samples that genotyped positively, 46 were of the Type II strain, 7 were of the Type III strain, and 2 were of atypical T. gondii strains. Five representative samples of the three genotypes were sequenced at loci SAG2, SAG3, GRA6, PK1, and UPRT-1. The DNA sequences confirmed the genotyping results. This study shows that the archetype Type II T. gondii strain, which is most widely distributed in North America and Europe, also predominates in arctic foxes on the Svalbard archipelago. This suggests that the T. gondii at this location originate from continental Europe and that transmission may be mediated by migrating birds. This study highlights the significance of long-distance transport of T. gondii and demonstrates that high-resolution genotyping protocols are useful for direct genetic studies of T. gondii when isolation of live parasites is infeasible.

Prevalence of antibodies against Toxoplasma gondii in polar bears (Ursus maritimus) from Svalbard and East Greenland.

Abstract Serum samples from 419 polar bears (Ursus maritimus) from Svalbard and the Barents Sea (collected 1990–2000) and 108 polar bears from East Greenland (collected 1999–2004) were assayed for antibodies against Toxoplasma gondii using the modified agglutination test. Antibody prevalences were 3.6% among cubs dependent on their mothers and 21.4% among subadults and adults. Among subadults and adults there was an interaction between population and sex, with similar prevalences among females (Svalbard = 19.5%, Greenland = 18.0%), but a high frequency among Svalbard males (28.7%) as compared to Greenland males (5.8%). The pattern was also significant after correcting for differences in age distribution. The sex-population interaction term is believed to be connected to area- and sex-specific feeding ecology. The prevalences of antibodies against T. gondii in Svalbard and Greenland were high compared to previously reported findings in polar bears from Russian and Alaskan areas.

Toxoplasma gondii in the Subarctic and Arctic

Summary The coccidian protozoan Toxoplasma gondii has a world-wide distribution. It causes toxoplasmosis, a potentially very serious disease to humans and other warm-blooded animals. Infection has in many studies been shown to be rather common in the Nordic countries also, where its prevalence both in domestic animals and wildlife can be explained by contacts with cats and their faeces, cats and wild felids being the only definitive hosts of the parasite known. Before the discovery of the complete life cycle of the parasite, other infection routes to animals were studied e.g. in Russia, where lateral transmission of infection in a reindeer herd was reported. The vehicle of infection was apparently body fluids, such as e.g. saliva and lacrimal fluid containing parasite tachyzoites, which might invade another reindeer via mucosal membranes. According to the finding, toxoplasmosis might be apprehended to be also a sexually transmitted disease. Following the discovery of the pivotal role of the cat in the epidemiology of T. gondii, possible alternative pathways of infection have generally been ignored. In Fennoscandian semi-domesticated reindeer, a clear association of the seroprevalence of antibodies to T. gondii was seen with the degree of domestication, and, thus, with cat contacts [1]. In the high Arctic of Svalbard, there is a considerably high seroprevalence of infection both in polar bears and Arctic foxes [2-4]. The source of infection is unlikely to be found in the seals constituting the major part of the polar bear’s diet, as in one study, antibodies were not found in North Atlantic marine mammals. However, in other, less arctic and remote, cetacean and pinniped populations studied, T. gondii infection has been found. Because Svalbard reindeer and sibling voles studied have been free from T. gondii infection, it can be assumed that sexual stages of infection (in definitive hosts) leading to oocyst production is not a major part of the Svalbard T. gondii life cycle [2]. Then, carnivores probably get the infection with food, anyhow. Cannibalism is considered common in polar bears and Arctic foxes, and probably can explain a lot. One parasite isolate from an Arctic fox proved to belong to the Type II strain, the predominant T. gondii lineage in the world [3]. This somewhat objects to the suggested idea of a specific Arctic life cycle of the parasite, but incorporates the Arctic to the globalT. gondii infection network. Further support to the hypothesis is gained from the finding that Svalbard barnacle geese (Branta leucopsis) are rather commonly infected. They may get the infection when wintering in Scotland. So, perhaps migratory birds are important in T. gondii globalisation. Cats are crucial to T. gondii epidemiology. However, the Arctic example proves that the successful parasite can thrive even in the absence of cats.

Toxoplasma gondii seroprevalence in pet cats in Norway and risk factors for seropositivity

Objectives The aims of the study were to estimate Toxoplasma gondii seroprevalence in pet cats in Norway and to evaluate risk factors for seropositivity. Additionally, serum biochemistry and haematological variables for T gondii seropositive and seronegative cats were compared. Methods A convenience sample of surplus sera submitted to the Central Laboratory, Norwegian University of Life Sciences, was collected. The samples were from healthy cats and cats with a variety of diseases. Analyses for IgG antibodies to T gondii were performed with a commercial direct agglutination test, with 1:40 as the threshold value. For risk factor analysis a logistic regression model of the relationship between predictors and the outcome was applied. Results One hundred and ninety-six of 478 cats were seropositive for T gondii, and the estimated seroprevalence in the study sample was 41.0% (95% confidence interval 36.6–45.4). Compared with domestic cats, pedigree cats had reduced risk for Toxoplasma seropositivity (odds ratio [OR] 0.42). Males had increased risk (OR 1.63) compared with females. The effect of age was highly significant, and an increase in the cats’ age across the interquartile range (IQR; 52–160 months/4–13 years of age) doubled the risk of Toxoplasma seropositivity (OR 2.11). The risk for Toxoplasma seropositivity among cats living in Oslo was significantly reduced (OR 0.51) when compared with the rest of Norway. Conclusions and relevance Pet cats in Norway appear to be commonly exposed to T gondii. Signalment and geographical region influenced the odds of Toxoplasma seropositivity, whereas health status did not.