Trichinella spiralis prevalence among wildlife of a boreal region rapidly reduced in the absence of spillover from the domestic cycle.

Carnivore and omnivore animals are the main reservoir hosts of nematodes of the genus Trichinella. Out of the twelve taxa identified so far in the world, four, namely Trichinella spiralis, Trichinella nativa, Trichinella britovi and Trichinella pseudospiralis, are circulating in Europe. All these four species were detected in Finnish wild animals and T. spiralis also in domestic pigs and synanthropic rats of Finland up to 2004, when the last T. spiralis infection was documented in a domestic pig. In the periods 1993-1997 and 1999-2005, T. spiralis was detected in 13.6% (6/44) and in 14.5% (46/317) of infected wild animals, respectively. The aims of the present study were to investigate the prevalence of Trichinella spp., especially T. spiralis in wild carnivores of Finland, 7-9 years after the eradication of Trichinella infection from Finnish domestic pigs, and to evaluate the impact of the disappearance of domestic cycle of T. spiralis on the sylvatic Trichinella cycle(s). Trichinella spp. larvae were detected in 34.7% (1081/3112) wild animals and 835 (77.2%) Trichinella spp. isolates were identified at the species level. Trichinella spiralis was detected in 9 animals (1.0% of identified infections) as single, double or triple infections; whereas, T. spiralis had been detected in 13.6% and in 14.5% of infected wild animals in the course of the two previous investigations. The reduction of T. spiralis prevalence from 1993-1997 to 2011-2013 is statistically significant (p < 0.001) both per total tested animals and per host species. The results of this study support the hypothesis of spillover from domestic pigs as a source of T. spiralis in wildlife. The eradication of T. spiralis from the domestic cycle in Finland in 2004 has probably established a virtuous cycle reducing the prevalence of this pathogen among wild carnivores. We can expect that within some years and in absence of T. spiralis reintroduction in the domestic habitat, it might even disappear from the Finnish wildlife.

Isolation of Brucella pinnipedialis from Grey Seals (Halichoerus grypus) in the Baltic Sea.

Brucella infection in seals was reported for the first time in 1994 around the coast of Scotland. Since then, marine mammal Brucella infections were found to be widely distributed in the northern hemisphere. Two Brucella species affect marine mammals: Brucella pinnipedialis in pinnipeds and Brucella ceti in cetaceans. We examined the livers of Baltic grey seals (Halichoerus grypus) from the Finnish coast (n=122) hunted, found dead, or killed as by-catch in fishing gear in 2013-15 as part of population health monitoring. We detected B. pinnipedialis in the livers of three grey seals. The bacterium was isolated from livers displaying parasitic cholangitis. We also detected Brucella DNA in liver flukes (Pseudamphistomum truncatum) obtained from a Brucella-infected grey seal, suggesting that flukes might be possible vectors of this pathogen in the marine environment.

High prevalence of zoonotic trematodes in roach (Rutilus rutilus) in the Gulf of Finland.

The intention to increase roach (Rutilus rutilus) consumption is in focus for ecological and economic reasons in Finland. However, its safety as food has not been considered comprehensively. We collected and artificially digested 85 roach halves originating from the south-eastern coast of Finland, and found trematode metacercariae in 98.8% of the samples. Based on polymerase chain reaction (PCR) and sequencing of amplicons generated from the ITS2 gene region, zoonotic parasites of the family Opistorchiidae were identified as Pseudamphistomum truncatum and Metorchis bilis, and also non-zoonotic Holostephanus dubinini (family Cyathocotylidae) and Posthodiplostomum spp. (family Diplostomidae) were identified. The species identity of other trematodes found is currently being investigated. Mixed infections of several trematode species were common. The prevalence of morphologically identified zoonotic P. truncatum was 46%, and zoonotic M. bilis was found in one sequence sample. The high prevalence of zoonotic trematode metacercariae in roach from the Gulf of Finland is alarming. Only thoroughly cooked roach products can be recommended for human or animal consumption from the area.

Dirofilaria repens transmission in southeastern Finland.

BACKGROUND: The spread of vector-borne diseases to new regions has become a global threat due to climate change, increasing traffic, and movement of people and animals. Dirofilaria repens, the canine subcutaneous filarioid nematode, has expanded its distribution range northward during the last decades. The northernmost European locations, where the parasite life-cycle has been confirmed, are Estonia and the Novgorod Region in Russia. RESULTS: Herein, we describe an autochthonous D. repens infection in a Finnish woman. We also present two cases of D. repens infection in imported dogs indicating the life-cycle in the Russian Vyborg and St Petersburg areas, close to the Finnish border. CONCLUSIONS: The most obvious limiting factor of the northern distribution of D. repens is the summer temperature, due to the temperature-dependent development of larvae in vectors. With continuing climate change, further spread of D. repens in Fennoscandia can be expected.

Dirofilaria repens Microfilaremia in Three Dogs in Estonia.

In Europe, the zoonotic parasite Dirofilaria repens continues to spread northward. We describe three likely autochthonous canine microfilaremic D. repens infections from Estonia, an European Union country located in the Baltic region of northern Europe. The parasite species was confirmed with sequencing. These are new northernmost D. repens findings in Europe and show that the zoonotic parasite has spread farther north. Infection with D. repens should be included in the list of differential diagnoses for human and animal hosts also in northern Europe.