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A cross-sectional study of Trichinella spp. infection in wolves (Canis lupus) reveals first evidence of T. spiralis in the species in Poland

Agnieszka Świątalska

Agnieszka Świątalska

Veterinary Hygiene LaboratoryGdańsk, Poland
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Świątalska, Agnieszka
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Ewa Bilska-Zając

Ewa Bilska-Zając

Department of Parasitology and Invasive Diseases, Bee and Aquatic Animal Diseases, National Veterinary Research InstitutePuławy, Poland
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Bilska-Zając, Ewa
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Weronika Korpysa-Dzirba

Weronika Korpysa-Dzirba

Department of Parasitology and Invasive Diseases, Bee and Aquatic Animal Diseases, National Veterinary Research InstitutePuławy, Poland
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Korpysa-Dzirba, Weronika
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Aneta Bełcik

Aneta Bełcik

Department of Parasitology and Invasive Diseases, Bee and Aquatic Animal Diseases, National Veterinary Research InstitutePuławy, Poland
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Bełcik, Aneta
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Michał Konrad Krzysiak

Michał Konrad Krzysiak

Department of Parasitology and Invasive Diseases, University of Life Sciences in LublinLublin, Poland
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Krzysiak, Michał Konrad
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Magdalena Larska

Magdalena Larska

Department of Virology and Viral Animal Diseases, National Veterinary Research InstitutePuławy, Poland
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Larska, Magdalena
  
Sep 17, 2025
A cross-sectional study of Trichinella spp. infection in wolves (Canis lupus) reveals first evidence of T. spiralis in the species in Poland's Cover Image
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Published Online: Sep 17, 2025
Received: Feb 07, 2025
Accepted: Sep 02, 2025
DOI: https://doi.org/10.2478/jvetres-2025-0046
Keywords
© 2025 Agnieszka Świątalska et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Fig. 1.

Boxplots for the number of Trichinella spp. larvae per gram (lpg) of three types different muscle tissues from 43 infected grey wolves. The line inside the box is the median. The top and bottom lines of the box are the 25th and 75th quartiles, respectively. The top and bottom whiskers mark the 5th and 95th quartiles, respectively. The dots represent outliers. Statistically significant differences with P-value < 0.05 are marked with asterisks
Boxplots for the number of Trichinella spp. larvae per gram (lpg) of three types different muscle tissues from 43 infected grey wolves. The line inside the box is the median. The top and bottom lines of the box are the 25th and 75th quartiles, respectively. The top and bottom whiskers mark the 5th and 95th quartiles, respectively. The dots represent outliers. Statistically significant differences with P-value < 0.05 are marked with asterisks

Fig. 2.

Boxplots for the number of Trichinella spp. larvae per gram (lpg) of three types different muscle tissues divided into T. britovi and T. spiralis from 23 and 20 infected grey wolves, respectively. The line inside the box is the median. The top and bottom lines of the box are the 25th and 75th quartiles, respectively. The top and bottom whiskers mark the 5th and 95th quartiles, respectively. The dots represent outliers. Statistically significant differences with P < 0.05 are marked with asterisks
Boxplots for the number of Trichinella spp. larvae per gram (lpg) of three types different muscle tissues divided into T. britovi and T. spiralis from 23 and 20 infected grey wolves, respectively. The line inside the box is the median. The top and bottom lines of the box are the 25th and 75th quartiles, respectively. The top and bottom whiskers mark the 5th and 95th quartiles, respectively. The dots represent outliers. Statistically significant differences with P < 0.05 are marked with asterisks

Fig. 3.

Distribution of wolves included in the study. Red dot – T. spiralis-positive grey wolf; green dot – T. britovi-positive grey wolf; yellow square – Trichinella-negative grey wolf
Distribution of wolves included in the study. Red dot – T. spiralis-positive grey wolf; green dot – T. britovi-positive grey wolf; yellow square – Trichinella-negative grey wolf

Fig. 4.

Boxplots for the number of Trichinella spp. larvae per gram (lpg) of three types different muscle tissues in relation to the age of wolves. The line inside the box is the median. The top and bottom lines of the box are the 25th and 75th quartiles, respectively. The top and bottom whiskers mark 5th and 95th quartiles, respectively. The dots represent data outliers. No statistically significant differences with P-value < 0.05 were found
Boxplots for the number of Trichinella spp. larvae per gram (lpg) of three types different muscle tissues in relation to the age of wolves. The line inside the box is the median. The top and bottom lines of the box are the 25th and 75th quartiles, respectively. The top and bottom whiskers mark 5th and 95th quartiles, respectively. The dots represent data outliers. No statistically significant differences with P-value < 0.05 were found

Summary of Trichinella spp_ prevalence reports in wolves in North America, Asia and Europe by country, period, parasite species assigned and sample type

Country (region) Source (Reference) Sampling period Sample size Trichinella spp. prevalence (%) Trichinella speciesa Tissueb
Finland (1) 1995–2005 102 39.2 Tn (Tb, Ts) m/d/fl
Finland (53) 2011–2013 85 34.1 Tn (Tb, Ts) no data
Finland (52) 1996–1998 18 33.0 Tn, Tb no data
Sweden (40) 2014–2019 197 5.6 Tn, Tb no data
Latvia (22) 2010–2014 23 100.0 Tb fl
Latvia (6) 2003–2008 no data 69.0 no data no data
Latvia (7) 2010–2012 8 69.7 no data m
Estonia (29) 1992–1999 34 79.4 Tn, Tb m
Romania (Carpathians) (16) 2000–2005 35 31.0 Tb m
Romania (Central) (25) 1991 399 30.5 Tb no data
Romania (Transylvania) (25) 1999–2002 7 71.4 Tb no data
Romania (Transylvania) (25) 2014–2015 3 66.7 Tb no data
USA and Canada (37) 2001–2013 244 51.0 T6, Tn tg
Canada (North) and USA (54) 2022 no data 13–52 T6, Tn no data
Greenland (54) no data no data 50.0 T6, Tn no data
Estonia (54) 1992–1996 no data 75–79 T6, Tn no data
Estonia (54) 1999 no data 63.20 T6, Tn no data
Finland, Norway, Russia (Kola Peninsula), Sweden (54) no data no data 32–39 T6, Tn no data
Russia (54) no data no data 10–65 T6, Tn no data
Russia (60) 1998–2000 82 97.50 Tn, Tb fl
Russia (20) 1998–2000 75 97.30 Tn, Tbc fl
Serbia (81) 2009–2010 116 46.50 Tb, Ts m
Serbia, Bosnia and Herzegovina, Macedonia (74) 2006–2013 116 46.5 Tb tg
Serbia (74) 2011–2022 49.50 Tb no data
Bosnia and Herzegovina (55) 2013–2023 36 38.89 Tb m
Canada (Alberta) (27) 1975–1977 217 5.50 no data tg, m, d
Canada (North) (38) 2001–2015 81 62.00 no data m, tg
Kazakhstan (75) 2020–2023 83 20.50 Tn m, d
Kazakhstan (2) 2013–2023 98 20.40 no data m
Poland (51) 1999–2007 10 40.0 Tb no data
Poland (10) 1999–2015 21 54.50 Tb m, d, fl
Poland (Carpathians) (18) 1996–2004 6 50.00 Tb no data
Italy (24) 2008–2012 67 8.9 Tb m
Italy (4) 2004–2014 218 27.1 Tb m
Italy (71) 1987–1993 48 19.0 Tb d
Italy (69) 1991–1993 25 28.0 Tb d, fl
Italy (61) 1985–1995 81 31.0 Tb m
Italy (3) 2015–2020 213 28.0 Tb d, fl
Italy (Western Alps) (43) 2017–2022 130 11.53 Tb d
Slovakia (Tatras) (28) 2005–2006 4 0 no data d, fl
Spain (67) 1996–1999 47 12.8 Tb m
Croatia (8) 1996–2007 67 31.0 Tb, Ts m
Germany (39) 2007–2014 53 3.70 Tb, Ts d
Germany (30) 2013–2023 545 4.04 Tb, Ts d

Sensitivities of the detection two species of Trichinella and the larvae burden (number larvae per gram - lpg) in three muscle tissues collected from 43 infected grey wolves

Type of muscle Trichinella britovi cases Trichinella spiralis cases
n/N (%)a Mean number of larvae per g (95% CIb) χ2 (P)c n/N (%) Mean number of larvae per g (95% CI) χ2 (P)c
Forelimb 21/23 (91.3) 0.48 (0.24–0.86) 19/20 (95.0) 0.42 (0.18–0.83)
Diaphragm 19/23 (82.6) 0.26 (0.1–0.57) 4.9 (0.08) 15/20 (75.0) 0.2 (0.05–0.51) 8.3 (0.02)
Tongue 13/17d (76.5) 0.53 (0.24–1.0) 12/16e (75.0) 0.71 (0.36–1.23)

Descriptive statistics of Trichinella prevalence among grey wolves in the study

Variable Trichinella spp. prevalence T. britovi prevalence T. spiralis prevalence
n/Na % (95% CI)b χ2 (P)c n/Na % (95% CI)b,d χ2 (P)c n/Na % (95% CI)b,d χ2 (P-value)c
Origin (province) 30.6 (0.002) 23.9 (0.02) 31.7 (0.002)
Lubelskie 0/3 0 (0–70.8) 0/3 - 0/3 -
Lubuskie 2/2 100 (15.8–100) 1/2 50 (1.2–98.7) 1/2 50 (1.2–98.7)
Łódzkie 0/2 0 (0–84.2) 0/1 - 0/1 -
Małopolskie 1/2 50.0 (12.6–98.7) 1/2 50 (1.2–98.7) 0/2 -
Mazowieckie 0/1 0 (0–97.5) 0/1 - 0/1 -
Podkarpackie 4/5 80.0 (28.3–99.5) 4/5 80.0 (28.3–99.5) 0/5 -
Podlaskie 8/17 47.0 (23.0–72.2) 9/17 47.0 (23.0–72.2) 0/17 -
Pomorskie 13/21 62.0 (38.4–81.9) 4/21 14.3 (3.0–36.3) 9/21 47.6 (25.7–70.2)
Śląskie 1/4 25.0 (0.6–80.6) 1/4 25.0 (0.6–80.6) 0/4 -
Świętokrzyskie 2/8 25.0 (3.2–65.1) 1/8 12.5 (0.3–52.6) 1/8 12.5 (0.3–52.6)
Warmińsko-mazurskie 1/2 50.0 (1.2–98.7) 1/2 50 (1.2–98.7) 0/2 -
Wielkopolskie 0/14 0 (0.0–23.2) 0/14 - 0/14 -
Zachodnio-pomorskie 11/15 73.3 (44.9–92.2) 2/15 13.3 (4.3–48.0) 8/15 53.3 (26.6–78.7)
Sex 1.9 (0.2) 0.01 (0.9) 0.2 (0.7)
Female 20/46 43.5 (29.9–58.9) 11/46 23.9 (12.6–38.8) 9/46 19.6 (9.3–33.9)
Male 23/48 47.9 (33.3–62.8) 12/48 25.0 (13.6–39.6) 11/48 22.9 (12.0–37.3)
Age group 4.5 (0.2) 1.8 (0.6) 4.7 (0.2)
Pups 1/5 20.0 (0.5–71.6) 0/5 0 (0.0-52.2) 1/5 20.0 (0.5-71.6)
Yearlings 4/10 40.0 (12.1–73.8) 3/10 30.0 (6.7–65.2) 1/10 10.0 (0.2–44.5)
Younger adults 19/46 41.3 (27.0–56.8) 10/46 21.7 (10.9–36.4) 9/46 19.6 (9.3–33.9)
Older adults 6/8 75.0 (34.9–96.8) 2/8 25.0 (3.2–65.1) 4/8 50.0 (15.7–84.3)
Body mass class 1.9 (0.4) 0.9 (0.8) 1.6 (0.4)
Lower (14–25 kg) 7/22 31.8 (13.8–54.9) 5/22 22.7 (7.8–45.4) 2/22 9.1 (1.1–29.2)
Medium (26–41 kg) 19/43 44.2 (29.1–60.1) 10/43 23.2 (11.8–38.6) 9/43 20.9 (10.0–36.0)
Higher (42–57 kg) 10/19 52.6 (28.9–75.5) 6/19 31.6 (12.6–56.6) 4/19 21.0 (6.0–45.6)
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