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Molecular characterization of putative Hepatozoon sp. from the sedge warbler (Acrocephalus schoenobaenus)

Published online by Cambridge University Press:  30 January 2013

ALEKSANDRA BIEDRZYCKA ,
AGNIESZKA KLOCH ,
MAGDALENA MIGALSKA  and
WOJCIECH BIELAŃSKI
ALEKSANDRA BIEDRZYCKA
Affiliation:
Institute of Nature Conservation, Polish Academy of Sciences, al. A. Mickiewicza 33, 31-120 Kraków, Poland
AGNIESZKA KLOCH*
Affiliation:
Institute of Nature Conservation, Polish Academy of Sciences, al. A. Mickiewicza 33, 31-120 Kraków, Poland
MAGDALENA MIGALSKA
Affiliation:
Institute of Nature Conservation, Polish Academy of Sciences, al. A. Mickiewicza 33, 31-120 Kraków, Poland
WOJCIECH BIELAŃSKI
Affiliation:
Institute of Nature Conservation, Polish Academy of Sciences, al. A. Mickiewicza 33, 31-120 Kraków, Poland
*
*Corresponding author. Tel: +48 608 217 909. Fax: +48 12 632 24 32. E-mail: a.kloch@uj.edu.pl
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Summary

We characterized partial sequences of 18S rDNA from sedge warblers infected with a parasite described previously as Hepatozoon kabeeni. Prevalence was 47% in sampled birds. We detected 3 parasite haplotypes in 62 sequenced samples from infected animals. In phylogenetic analyses, 2 of the putative Hepatozoon haplotypes closely resembled Lankesterella minima and L. valsainensis. The third haplotype grouped in a wider clade composed of Caryospora and Eimeria. None of the haplotypes showed resemblance to sequences of Hepatozoon from reptiles and mammals. Molecular detection results were consistent with those from microscopy of stained blood smears, confirming that the primers indeed amplified the parasite sequences. Here we provide evidence that the avian Hepatozoon-like parasites are most likely Lankesterella, supporting the suggestion that the systematic position of avian Hepatozoon-like species needs to be revised.

Keywords

haemogregarinesHepatozoonLankesterellaavian blood parasitessedge warblerAcrocephalus schoenobaenus
Type
Research Article
Information
Parasitology , Volume 140 , Issue 6 , May 2013 , pp. 695 - 698
Copyright
Copyright © Cambridge University Press 2013

INTRODUCTION

The genus Hepatozoon consists of apicomplexans infecting a wide range of mammals, birds, reptiles and amphibians (Smith, Reference Smith1996). In birds, Hepatozoon has been reported from various families, and altogether 15 species are considered valid (Peirce, Reference Peirce2005). Generally, the sexual reproduction of Hepatozoon occurs in a blood-sucking invertebrate. After ingestion of the invertebrate host by a vertebrate, the sporozoites affect its visceral organs, where they give rise to merogonic stages that later develop into gametocytes circulating in the blood. However, the invertebrate host of most Hepatozoon species remains unknown, particularly in the case of bird parasites, although Bennett et al. (Reference Bennett, Earle and Penzhorn1992a) identified 2 possible intermediate hosts of H. atticorae infecting swallows. The limited knowledge of the Hepatozoon life cycle results from the fact that most infections are light, and the prevalence studies usually lack investigation of the intermediate hosts (Bennett et al. Reference Bennett, Earle and Peirce1992b).

Because the life cycles of many of these parasites are poorly known and their blood stages are morphologically similar (Merino et al. Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006), the systematics of the genus Hepatozoon and other haemogregarines are far from clear (Desser, Reference Desser and Kreier1993). Smith and Desser (Reference Smith and Desser1997) used a detailed phylogenetic analysis based on morphological, morphometric and developmental characteristics to show that Hepatozoon is a paraphyletic group, and suggested that the taxonomy of this group should be modified. A recent analysis of available adeleorinid sequences (Barta et al. Reference Barta, Ogedengbe, Martin and Smith2012) added more weight to that side of the argument, but with no molecular data from birds.

The only published molecular analysis of an avian Hepatozoon-like isolate is from Merino et al. (Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006), who obtained it from the blue tit Cyanistes caeruleus; in their analysis the parasite was closely related to Lankesterella and was grouped outside other Hepatozoon species. No such doubts have been raised about the taxonomy of isolates from other terrestrial vertebrates (Barta et al. Reference Barta, Ogedengbe, Martin and Smith2012). This suggests that the taxonomic position of avian Hepatozoon species should be revised and that more sequences from parasites identified morphologically as hepatozoa in birds need to be examined. Here we give a molecular description of a fragment 18S rDNA from putative H. kabeeni taken from the sedge warbler Acrocephalus schoenobaenus.

MATERIALS AND METHODS

We collected samples in a sedge warbler population from the Nida marshes (southern Poland) during the 2004–2006 breeding seasons. The birds were mist-netted and blood samples were obtained from the brachial veins of 131 adult birds of both sexes. A drop of blood was used to prepare thin smears, and the rest of the blood was preserved in 95% ethanol for molecular analyses. The smears were air-dried, fixed with 95% methanol and stained with Hemacolor (Merck). The slides were examined microscopically to find blood parasites, including putative Hepatozoon kabeeni according to the description given by Kruszewicz and Drycz (Reference Kruszewicz and Dyrcz2000). For each slide 100 fields at 1600× (Nikon 50i light microscope) were checked. In each of a random subset of 40 smears 1 parasite was measured (length, width, area) using ImageJ v. 1.42 software (Wayne Rasband, National Institutes of Health, USA).

Genomic DNA was extracted with the Nucleospin Tissue Kit (Macherey and Nagel, Germany). Part of 18S rDNA was amplified by PCR using primers Hep800F/Hep1615R as described by Merino et al. (Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006). The PCR reaction contained 10 ng template DNA, 1·5 mm MgCl2, 0·2 mm of each dNTP, 1 mm of each primer, and 0·5 U AmpliTaq (Applied Biosystems, Foster City, CA, USA). The reaction started from initial denaturation for 3 min at 94 °C followed by 40 cycles: 95 °C for 40 s, 60 °C for 1 min, 72 °C for 1 min, and final extension at 72 °C for 10 min. Products were separated on 2% agarose gel to check whether amplification was successful.

All samples indicating infection with the putative Hepatozoon were sequenced in both directions using Hep800F/Hep1615R primers in an automated sequencer (ABI 310, Applied Biosystems). DNA sequences were aligned in CLUSTAL W (Larkin et al. Reference Larkin, Blackshields, Brown, Chenna, McGettigan, McWilliam, Valentin, Wallace, Wilm, Lopez, Thompson, Gibson and Higgins2007) and edited using BIOEDIT (Hall, Reference Hall1999).

The phylogenetic relationship between the putative Hepatozoon and other apicomplexans was analysed using a maximum likelihood (ML) phylogenetic tree based on sequences characterized in the current study and those taken from GenBank. A set of trees was reconstructed in TREEFINDER (Jobb et al. Reference Jobb, von Haeseler and Strimmer2004), and the best-fitting model of nucleotide substitution was selected based on the Akaike information criterion (AIC), using the FindModel web application (http://www.hiv.lanl.gov/content/sequence/findmodel/findmodel.html). The Tamura-Nei plus gamma model had the lowest AIC, and thus it was implemented in subsequent analyses in TREEFINDER. For ML analysis we used the likelihood-ratchet method. Branch confidence values were estimated using the estimated likelihood weights approach (Strimmer and Rambaut, Reference Strimmer and Rambaut2002).

RESULTS

Overall, 3 parasite species were found: the most prevalent Haemoproteus was found in 45·3% of birds, putative Hepatozoon in 32·7% (Fig. 1) and Plasmodium in 1·6%. Infections with single parasites occurred in 29·7% of animals, with 2 parasites in 23·4%, and 3 parasite species were detected in 3 birds (1·6%). The size of the putative Hepatozoon from sedge warbler differed significantly from the measurements of H. kabeeni reported previously in sedge warbler, but it also differed in width and area from H. sylvae and avian Lankesterellid (Table 1).

Fig 1. Hepatozoon-like parasite (arrow) from the sedge warbler, magnification 1600 × .

Table 1. Measurements of the putative Hepatozoon species from the sedge warbler compared with those of H. kabeeni (Kruszewicz and Dyrcz Reference Kruszewicz and Dyrcz2000), H. sylvae (Shurulinkov and Chakarov Reference Shurulinkov and Chakarov2006), and an avian lankesterellid (Merino et al. Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006)

(Measurements given in μm, standard deviations given in parentheses, N denotes number of measured infected cells examined. The Welch t-test shows the difference between measurements of putative Hepatozoon from current paper to those reported by other authors. After Bonferroni correction for multiple comparisons, the P-value corresponding to α = 0·05 is 0·016.)

Based on PCR, we found putative Hepatozoon in 131 sedge warblers (47·3%), and the prevalence was higher than those detected using microscopic examination, which indicates the higher sensitivity of molecular detection. All samples found to be positive by PCR were also identified as infected by microscopic examination.

In 62 sequenced samples we detected 3 haplotypes and submitted the sequences to the GenBank (Accession nos JX218106–JX218108). In the phylogenetic analysis, 2 of the putative Hepatozoon haplotypes closely resembled Lankesterella minima and L. valsainensis (Fig. 2). The third haplotype grouped in a wider clade that also included Caryospora and Eimeria. The analysed haplotypes did not show resemblance to sequences of hepatozoa from reptiles and mammals, which grouped separately in a distinct clade.

Fig. 2. Phylogenetic relationships of the analysed haplotypes, describing relationships between the putative Hepatozoon species from the sedge warbler and other apicomplexans. The sequences reported in the current paper are given in bold.

DISCUSSION

In this work we characterized 18S rDNA of a Hepatozoon-like parasite previously identified as H. kabeeni (Kruszewicz and Dyrcz, Reference Kruszewicz and Dyrcz2000) from the sedge warbler. Little resemblance of the analysed sequences to those of hepatozoa from other mammalian and reptile hosts was found, but PCR gave positive results for the same samples that were found by microscopy to be infected, confirming that the primers we used amplified the right target. The putative H. kabeeni sequences were closely related to Lankesterella, and 1 haplotype grouped in a clade composed of various Eimeriidae. Our results are in accordance with the finding of Merino et al. (Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006) that 18S rRNA sequences from a putative Hepatozoon species from the blue tit closely resemble those of Lankesterella.

The systematics of haemogregarines is problematic, as it is based mostly on morphological descriptions of the parasites, and knowledge of their life cycle is crucial for proper classification (Levine, Reference Levine1982). Generally, 2 groups of avian parasites have circulating blood stages: gamonts of members of the suborder Adeleorina, including Hepatozoon, and circulating zoites (sporozoites or merozoites) of Lankesterellidae and Eimeriidae (Merino et al. Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006). None of them are easy to distinguish by morphology; because certain lankesterellid sporozoites and haemogregarine gamonts are very similar, some species designated as members of one group have later been assigned to the other (Desser, Reference Desser and Kreier1993; Merino et al. Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006). The systematic position of Lankesterella has been tossed around through the decades (Box, Reference Box1975; Desser, Reference Desser1980; Levine, Reference Levine1982; Upton, Reference Upton, Lee, Leedale and Bradbury2000). Addressing the systematics of Hepatozoon, Smith (Reference Smith1996) proposed classifying all haemogregarine infections in birds as Hepatozoon until we have enough data on the life cycle of these parasites to place them in the correct genus.

Hepatozoon kabeeni was described by Kruszewicz and Dyrcz (Reference Kruszewicz and Dyrcz2000) in sedge warblers from Poland. Peirce (Reference Peirce2005) did not list this species in his revision of the genus, and there are no reports of H. kabeeni from any other bird host. In the reed warbler Acrocephalus scirpaceus, a host closely related to the sedge warbler, Shurulinkov and Chakarov (Reference Shurulinkov and Chakarov2006) reported H. sylvae. The parasite we describe here differed in size and shape from both H. kabeeni and H. sylvae, and it was also smaller and longer than the avian lankesterellid that Merino et al. (Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006) described. This suggests that it should not be recognized as a Hepatozoon species and that most likely it belongs to the genus Lankesterella.

The systematic position of this Hepatozoon-like parasite from the sedge warbler should be revised, and presumably the same applies to all Hepatozoon-like parasites of other avian hosts, as the findings of Merino et al. (Reference Merino, Marinez, Martinez-de la Puente, Criado-Fronelio, Tomas, Morales, Lobato and Garcia-Fraile2006) suggest. To do this, more sequences are needed. Knowledge of the parasite life cycle is considered crucial for proper classification of these species, but our results show that phylogenetic molecular analysis is a good alternative tool, particularly helpful when the parasite life cycle proves elusive.

FINANCIAL SUPPORT

This work was supported by a Polish Science Foundation grant (POMOST 2010-2/1) awarded to Aleksandra Biedrzycka.

References

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Figure 0

Fig 1. Hepatozoon-like parasite (arrow) from the sedge warbler, magnification 1600 × .

Figure 1

Table 1. Measurements of the putative Hepatozoon species from the sedge warbler compared with those of H. kabeeni (Kruszewicz and Dyrcz 2000), H. sylvae (Shurulinkov and Chakarov 2006), and an avian lankesterellid (Merino et al. 2006)

(Measurements given in μm, standard deviations given in parentheses, N denotes number of measured infected cells examined. The Welch t-test shows the difference between measurements of putative Hepatozoon from current paper to those reported by other authors. After Bonferroni correction for multiple comparisons, the P-value corresponding to α = 0·05 is 0·016.)
Figure 2

Fig. 2. Phylogenetic relationships of the analysed haplotypes, describing relationships between the putative Hepatozoon species from the sedge warbler and other apicomplexans. The sequences reported in the current paper are given in bold.