Non-native Nematode Ashworthius sidemi Currently Dominates the Abomasal Parasite Community of Cervid Hosts in the Czech Republic

Abstract

Ashworthius sidemi is an abomasal nematode typical for Asiatic cervids such as sambar (Rusa unicolor) or sika deer (Cervus nippon). This non-native parasite was introduced into Europe via sika deer in the late 19th and early 20th centuries. The current dynamic spread of this parasite amongst autochthonous wild cervids occurs independently of human activities, and A. sidemi has a negative impact on the health of wild ruminants and may pose a threat to the conservation of endangered wild ungulates and to livestock. This invasive parasite has been previously detected in the Czech Republic, but more accurate information on A. sidemi is required. Only limited information is generally available on the factors influencing the spread of abomasal nematodes in wild ruminants, so more information is necessary for planning effective strategies of parasite control. We therefore conducted a survey on the abomasal nematodes in cervids in both game reserves and hunting grounds across the Czech Republic, taking into account the hosts (species, age, sex) and environmental factors (monthly average temperature). The abomasa of 104 animals belonging to five cervid species originating from various locations of the country were collected. Data on host (species, sex, and age group) and the monthly average temperature in the region were obtained for each animal. The parasitological analyses indicated that 92% of the abomasa were infected by nematodes. Ashworthius sidemi was the most prevalent (72%) and abundant (80% of the total recovered individuals) nematode species and was detected in all cervid species except white-tailed deer. The intensity of A. sidemi was highest in roe deer (Capreolus capreolus) and fallow deer (Dama dama), but A. sidemi abundance did not depend substantially on the host or environmental factors. In contrast, the abundance of nematodes from the subfamily Ostertagiinae was influenced by the host species and temperature. Parasitic load was significantly higher in roe deer and during the warmer periods of the survey. We also detected another non-native nematode species, Spiculopteragia houdemeri. The results of our study suggest that the non-native nematode A. sidemi is now widespread amongst cervid hosts in the Czech Republic, probably due to the high sensitivity of autochthonous cervids to A. sidemi infections as well as adaptation of this parasite to the current climatic conditions of this country.

An alien parasite in a changing world – Ashworthius sidemi has lost its traditional seasonal dynamics

“…In contrast, our results suggest that under the current Central European climate and management conditions at the study location, A. sidemi egg shedding may occur almost year-round from April to January. This finding is consistent with previous studies conducted in the CR that reported the occurrence of A. sidemi adults in wild ruminants and lack of hypobiosis during the winter (15,21). A possible explanation for this shift could be recent higher temperatures that are more favorable for the parasite development than those prevailing during investigations of A. sidemi seasonal dynamics fifteen years ago or earlier.…”

“…Similar results have been previously published (20); only larvae and juveniles of A. sidemi were recovered from the abomasa of sika deer and Maral deer during autumn and winter in the Russian Far East. In contrast to the above mentioned studies, only negligible importance of hypobiosis has been detected in the Czech Republic (CR), indicating a possible modification of seasonal patterns in A. sidemi (15,21). Seasonal dynamics of trichostrongylids can differ based on the climate conditions in different regions and may also shift over time due to global climate changes (22,23).…”

Extended abstracts

“…Wild cervids are known to have a relatively effective immunity against gastro-intestinal nematodes. This phenomenon is attributed to the secondary plant metabolites, which characterise the normal diet of these browser and intermediate grazer ruminants (Magdálek et al 2022). Our study aimed to determine those feed components which could be potent against Haemonchus contortus the most threatening parasite in the small ruminant sector (Adduci et al 2022).…”