High Prevalence of Hepatitis E Virus in Swedish Moose – A Phylogenetic Characterization and Comparison of the Virus from Different Regions

Abstract

BackgroundHepatitis E virus (HEV) infects a range of species, including humans, pigs, wild boars and deer. Zoonotic transmission may contribute to the high HEV seroprevalence in the human population of many countries. A novel divergent HEV from moose (Alces alces) in Sweden was recently identified by partial genome sequencing. Since only one strain was found, its classification within the HEV family, prevalence in moose and zoonotic potential was unclear. We therefore investigated samples from 231 moose in seven Swedish counties for HEV, and sequenced a near complete moose HEV genome. Phylogenetic analysis to classify this virus within the family Hepeviridae and to explore potential host specific determinants was performed.Methods and FindingsThe HEV prevalence of moose was determined by PCR (marker for active infection) and serological assays (marker of past infection) of sera and 51 fecal samples from 231 Swedish moose. Markers of active and past infection were found in 67 (29%) animals, while 34 (15%) were positive for HEV RNA, 43 (19%) were seropositive for anti-HEV antibodies, and 10 (4%) had both markers. The number of young individuals positive for HEV RNA was larger than for older individuals, and the number of anti-HEV antibody positive individuals increased with age. The high throughput sequenced moose HEV genome was 35-60% identical to existing HEVs. Partial ORF1 sequences from 13 moose strains showed high similarity among them, forming a distinct monophyletic clade with a common ancestor to HEV genotype 1-6 group, which includes members known for zoonotic transmission.ConclusionsThis study demonstrates a high frequency of HEV in moose in Sweden, with markers of current and past infection demonstrated in 30% of the animals. Moose is thus an important animal reservoir of HEV. The phylogenetic relationship demonstrated that the moose HEV belonged to the genotype 1-6 group, which includes strains that also infect humans, and therefore may signify a potential for zoonotic transmission of this HEV.

Zoonotic Hepatitis E Virus: Classification, Animal Reservoirs and Transmission Routes

“…Only one partial genome with complete ORFs is available. A phylogenetic analysis with partial sequences has shown high similarities between different moose strains from the same geographic region (>91% nt identity) [24]. They form a distinct group within the Orthohepevirus genus and are close to the Orthohepevirus A species (63% nt identity).…”

“…In the Orthohepevirus A species, two other strains of HEV, classified as genotype 5 and 6 (HEV-5 and HEV-6), have also been identified in wild boar in Japan [8,22] and more recently, HEV-7 has been detected in faecal samples from camels [23]. An HEV strain has been characterised in Swedish moose [24] but it is still not assigned to any HEV species.…”

Seroprevalence of hepatitis E virus in Lithuanian domestic pigs and wildlife

“…Lack of scientific studies on seroprevalence in moose and European bison makes comparisons difficult. In Sweden, 19% (231/43) of moose were seropositive for HEV antibodies (Lin et al 2015). We noticed seroprevalence of 11.76% in moose and no positive samples of 3 European bison.…”

Hepatitis E virus in humans, farm animals and animals from the sylvatic environment

“…Infekcje HEV u fretek, podobnie jak u innych gatunków zwierząt są bezobjawowe (35,54). Analiza sekwencji nukleotydowych szczepów HEV fretek wskazała na ich pokrewieństwo filogenetyczne do szczepów HEV gryzoni (70).…”

“…Nowym sylwatycznym rezerwuarem wirusa jest łoś. Szczepy HEV identyfikowane u tych zwierząt posiadały zaledwie 35-60% podobieństwo sekwencji nukleotydowych do szczepów HEV człowieka i innych gatunków zwierząt wrażliwych na zakażenie (35). Pomimo że zakażenia u zwierząt wykazują gatunkowo specyficzne szczepy HEV, to niektóre gatunki, jak np.…”