Anu Näreaho

Toxoplasma gondii in wild cervids and sheep in Finland: North-south gradient in seroprevalence

A nationwide seroepidemiological study was conducted to estimate the prevalence of Toxoplasma gondii in selected wild and domestic ruminants in Finland. Serum samples from 1367 game cervids collected during the hunting season in 2008-2009 and 1940 sheep sera collected in 2008 were screened with a commercial direct agglutination test at a serum dilution of 1:40. T. gondii-specific IgG antibodies were detected in 116 (9.6%) of 1215 moose (European elk, Alces alces), 36 (26.7%) of 135 white-tailed deer (Odocoileus virginianus), 3 (17.6%) of 17 roe deer (Capreolus capreolus), and 477 (24.6%) of 1940 domestic sheep. Seropositive sheep were found in 74 (76.3%) of the 97 flocks examined. The odds of seropositivity in the adult moose was 2.9 times higher than the odds in calves; in white-tailed deer, the odds ratio was 3.2. The male moose had a significantly lower seroprevalence than the female, whereas the seroprevalence in the male white-tailed deer was higher than in the female; the odds ratios were 0.6 and 2.5, respectively. A clear geographical gradient in the seroprevalence was revealed in moose and sheep. The seroprevalences were lowest (1.6 and 8.6%, respectively) in the north and highest (24.6 and 36.4%, respectively) in the south-western regions, and ranged between these values in the other regions. In fact, the seroprevalence in moose from the south-west was not significantly different from the prevalence in white-tailed deer from the same area. Thus, the Finnish wild cervids and sheep are commonly exposed to T. gondii, especially in the southern part of the country.

Feline toxoplasmosis in Finland cross-sectional epidemiological study and case series study

Three subgroups of the Finnish cat population underwent investigation for different aspects of feline toxoplasmosis. Blood samples of 445 purebred pet cats and 45 shelter cats were screened for Toxoplasma gondii–specific immunoglobulin G antibodies with a direct agglutination test. The overall seroprevalence was 48.4%; older cats and cats receiving raw meat in their diet were more often seropositive. Fecal samples were obtained from 131 shelters cats; 2 of the cats were found shedding T. gondii–like oocysts, and the oocysts shed by 1 of the 2 were confirmed as T. gondii with polymerase chain reaction. Among 193 cats submitted for necropsy during a 3.5-year period, 6 (3.1%) had been diagnosed with generalized toxoplasmosis and were retrospectively further investigated. The main pathological lesions included acute interstitial pneumonia, acute necrotizing hepatitis, and nonsuppurative meningoencephalitis with glial granulomas. Immunohistochemical staining demonstrated a mild to massive parasite burden in tissues with pathological lesions as well as in unaffected tissues. The results of the direct multilocus genotyping of T. gondii parasites detected were consistent with endemic genotype II, and the causative parasite strains were isolated from 2 of the generalized toxoplasmosis cases. The results indicate that cats in Finland commonly encounter T. gondii and contribute to the environmental oocyst burden, while the endemic genotype II can also prove fatal to the parasite’s definitive host. Preventing feline T. gondii infections is not only of public health importance but also a welfare issue for the cats themselves.

NATURAL TOXOPLASMA GONDII INFECTIONS IN EUROPEAN BROWN HARES AND MOUNTAIN HARES IN FINLAND: PROPORTIONAL MORTALITY RATE, ANTIBODY PREVALENCE, AND GENETIC CHARACTERIZATION

In material examined postmortem in Finland from May 2006 to April 2009, acute generalized toxoplasmosis was the immunohistochemically confirmed cause of death in 14 (8.1%) of 173 European brown hares (Lepus europaeus) and four (2.7%) of 148 mountain hares (Lepus timidus). Sera from 116 of the European brown hares and 99 of the mountain hares were screened with a commercial direct agglutination test for Toxoplasma gondii-specific IgG antibodies at a dilution of 1:40. All sera from cases of fatal toxoplasmosis had high titers of antibodies reactive to T. gondii. In contrast, none of 107 European brown hares and four (4%) of 96 mountain hares that died of other causes were antibody-positive. The proportional mortality rates and the T. gondii antibody prevalences among noncases differed significantly between the two host species (P<0.05). Direct genetic characterization of the causative agent was performed on DNA extracted from formalin-fixed, paraffin-embedded tissue of the hares with fatal toxoplasmosis. Based on the results with six microsatellite markers (B18, TUB2, TgM-A, W35, B17, and M33; all six in 15 cases and four in three cases), all the cases were caused by T. gondii genotype II; the size of the PCR product at the seventh marker (M48) varied (213–229 base pairs). The presence of T. gondii genotype II, which is endemic in Europe, is now confirmed in Finnish wildlife: Natural infections with T. gondii parasites belonging to this widespread genotype caused fatal generalized toxoplasmosis in the two species of wild hares.

Impaired efficacy of ivermectin against Parascaris equorum, and both ivermectin and pyrantel against strongyle infections in trotter foals in Finland.

In order to assess the resistance situation against macrocyclic lactones in Parascaris equorum and against tetrahydropyrimidine derivatives in strongyles in Finnish trotter horses, 112 foals on 18 farms, mostly 1 year old, were examined for these parasites with a modified McMaster faecal flotation method. P. equorum positive foals (n=24) were given ivermectin orally at a dose of 200 μg/kg b.w., while strongyle positive but P. equorum negative foals (n=38) received pyrantel embonate orally at a dose of 19 mg/kg. Sixteen P. equorum infected foals, treated with ivermectin, also harboured strongyles. During the anthelmintic treatment visit to the farm, Faecal Egg Count Reduction Test (FECRT) reference (first) samples were collected. Fourteen days later, the second sampling (reduction samples) was done. The FECR was calculated for each foal/parasite combination. The reduction efficacies of ivermectin against P. equorum (mean 52%, calculated from the individual egg count reductions) and pyrantel against strongyles (43%) were strongly indicative of widespread resistance. Also indication of ivermectin resistance among strongyles was seen. The widespread use of anthelmintics for Finnish horses obviously has resulted in resistance, as has happened elsewhere, too.

Antibodies against Toxoplasma gondii in Fennoscandian reindeer — association with the degree of domestication

To measure the prevalence of antibodies against Toxoplasma gondii in Fennoscandian reindeer, we examined 2577 serum samples collected between 1993 and 1996 from slaughtered reindeer from Finnmark county, Norway, and from several locations in Finland. The overall prevalence in this sample was 0.9%, and the titres of the seropositives in the Direct Agglutination Test (DAT) were between 1:40 and 1:162000. Logistic regression associated seropositivity with the age of the animal, the odds ratio (OR) of adults was four when compared with calves. Seropositivity was also positively associated with corral feeding, which was used in the analysis as an indicator of domestication. No significant association was found with sex, or the frost sum of the pasture area.

Farmed wild boars exposed to Toxoplasma gondii and Trichinella spp.

The meat of wild boar (Sus scrofa L.) can be a source of human infections with zoonotic parasites Toxoplasma gondii and Trichinella spp. We screened 197 wild boar sera collected at slaughter from 25 Finnish farms in 2007-2008 for serological evidence of infections with these parasites. Using a commercial direct agglutination test at a serum dilution of 1:40, T. gondii-specific IgG antibodies were detected in 65 (33.0%) samples, on 14 (56.0%) farms. Females, animals older than 24 months, animals of small herds, and animals originating from south-western parts of Finland were more often T. gondii-seropositive than were males, younger animals, animals of larger herds, and animals originating from the north and east, respectively. Four (2.0%) of the sera, originating from three (12.0%) farms, tested Trichinella-seropositive with an in-house ELISA and a conservative cut-off for seropositivity. One farm had both T. gondii- and Trichinella-seropositive animals. Taken together, an infection source had been present on 16 (64.0%) farms, and 69 (35.0%) of the 197 farmed wild boars intended for human consumption had specific serological evidence of exposure to a zoonotic parasite.

Clinical features of experimental trichinellosis in the raccoon dog (Nyctereutes procyonoides).

Three groups of six raccoon dogs (Nyctereutes procyonoides) were provided for the experiment: the first group was infected with pig-origin Trichinella spiralis, the second with raccoon dog-origin Trichinella nativa, and the third served as controls. Infection dose for both parasite species was 1000 larvae/kg of body weight, which led to intense final infection. Clinical signs, haematology and serum biochemistry with repeated blood samples were monitored up to 12 weeks post-infection. The most significant findings were a short-term eosinophilia in peripheral blood from the end of the first week post-infection until the end of the third week, loss of weight, and mild anaemia. In the early phase of the infection, the animals had gastrointestinal signs, loss of appetite and diarrhoea. No specific differences in clinical findings could be noticed between the groups infected with T. nativa and T. spiralis. In contrast to the symptoms reported in human outbreaks, fever was not observed in any of the infected animals and serum levels of muscle-specific enzymes did not change. No acute-phase response was observed in the enteral or parental phase of the infection. These findings indicate that because Trichinella spp. are very well adapted to the raccoon dog, it thus, could serve as the most crucial reservoir animal for sylvatic trichinellosis in Finland.

The first report of autochthonous non-vector-borne transmission of canine leishmaniosis in the Nordic countries

BackgroundLeishmania spp. are zoonotic protozoans that infect humans and other mammals such as dogs. The most significant causative species in dogs is L. infantum. In dogs, leishmaniosis is a potentially progressive, chronic disease with varying clinical outcomes. Autochthonous cases of canine leishmaniosis have not previously been reported in the Nordic countries.ResultsIn this report we describe the first diagnosed autochthonous cases of canine leishmaniosis in Finland, in which transmission via a suitable arthropod vector was absent. Two Finnish boxers that had never been in endemic areas of Leishmania spp., had never received blood transfusions, nor were infested by ectoparasites were diagnosed with leishmaniosis. Another dog was found with elevated Leishmania antibodies. A fourth boxer dog that had been in Spain was considered to be the source of these infections. Transmission occurred through biting wounds and semen, however, transplacental infection in one of the dogs could not be ruled out.Two of the infected dogs developed a serious disease and were euthanized and sent for necropsy. The first one suffered from membranoproliferative glomerulonephritis and the second one had a chronic systemic disease. Leishmania sp. was detected from tissues by PCR and/or IHC in both dogs. The third infected dog was serologically positive for Leishmania sp. but remained free of clinical signs.ConclusionsThis case report shows that imported Leishmania-infected dogs may pose a risk for domestic dogs, even without suitable local arthropod vectors.

Feline intestinal parasites in Finland: prevalence, risk factors and anthelmintic treatment practices

The aim of this study was to estimate the prevalence of feline intestinal parasites in Finland and to determine the possible risk factors for infection. Altogether 411 feline fecal samples were analyzed with a flotation method to reveal helminth eggs and protozoan oocysts. Of the samples, 402 were also screened for Giardia species antigens with a commercial enzyme-linked immunosorbent assay kit. The cat owners completed a questionnaire. Toxocara cati prevalence was 5.4% and Toxascaris leonina 0.2%. Taenia species eggs were found in 1.5% of the samples and Isospora felis in 0.7%, whilst 3.2% of the samples tested positive for Giardia species antigen. Risk factors for Toxocara/Toxascaris species infection included being a non-pedigree cat, having access to the outdoors, living outside of the cities and receiving home-made food. Pedigree cats were at greater risk of contracting Giardia duodenalis. The majority of the cat owners (62.4%) treated their cat with anthelmintics 2–4 times per year.

Genetic relationships among Trichinella pseudospiralis isolates from Australian, Nearctic, and Palearctic regions

The study of the genetic polymorphism of pathogens is important for phylogenetic and biogeographic studies and, in the case of foodborne pathogens, to trace the origin of food infection. Since its discovery in 1972, the nonencapsulated species Trichinella pseudospiralis has been detected in mammals and birds, and human infection has occurred, in some cases resulting in death. We studied DNA polymorphism among ten T. pseudospiralis isolates from the Palearctic, Nearctic, and Australian regions, screening the sequences of nine genes [18sRNA, a random amplified polymorphism DNA derived sequence, mitochondrial cytochrome oxidase subunit I (COI), cytochrome P450, cynate lyase, epithelial fusion failure-1, and three unknown genes of Tp3, Tp8, and Tp26]. A high identity of sequence for the nine gene loci was obtained among the seven isolates from the Palearctic region and between the two isolates from the Nearctic region. Genetic identity analysis indicated the distinct polymorphism among the three geographical origins. To easily identify T. pseudospiralis genotypes, a polymerase chain reaction-restriction fragment length polymorphism analysis of COI gene was performed, and the results confirmed the DNA polymorphism within T. pseudospiralis, corresponding to the three regions of origin. We have named the three genotypes as “T. pseudospiralis Palearctic genotype” (code T4P), “Nearctic genotype” (code T4N), and “Australian genotype” (code T4A). To further investigate polymorphism among the nonencapsulated Trichinella species, the sequences of four gene loci (COI, P450, cynate lyase, and SB147D) of T. pseudospiralis, T. papuae, and T. zimbabwensis were analyzed, and the results showed high polymorphism among the three species, strongly supporting their classification as separate species.