Fellow travellers: a concordance of colonization patterns between mice and men in the North Atlantic region

Background

House mice (Mus musculus) are commensals of humans and therefore their phylogeography can reflect human colonization and settlement patterns. Previous studies have linked the distribution of house mouse mitochondrial (mt) DNA clades to areas formerly occupied by the Norwegian Vikings in Norway and the British Isles. Norwegian Viking activity also extended further westwards in the North Atlantic with the settlement of Iceland, short-lived colonies in Greenland and a fleeting colony in Newfoundland in 1000 AD. Here we investigate whether house mouse mtDNA sequences reflect human history in these other regions as well.

Results

House mice samples from Iceland, whether from archaeological Viking Age material or from modern-day specimens, had an identical mtDNA haplotype to the clade previously linked with Norwegian Vikings. From mtDNA and microsatellite data, the modern-day Icelandic mice also share the low genetic diversity shown by their human hosts on Iceland. Viking Age mice from Greenland had an mtDNA haplotype deriving from the Icelandic haplotype, but the modern-day Greenlandic mice belong to an entirely different mtDNA clade. We found no genetic association between modern Newfoundland mice and the Icelandic/ancient Greenlandic mice (no ancient Newfoundland mice were available). The modern day Icelandic and Newfoundland mice belong to the subspecies M. m. domesticus, the Greenlandic mice to M. m. musculus.

Conclusions

In the North Atlantic region, human settlement history over a thousand years is reflected remarkably by the mtDNA phylogeny of house mice. In Iceland, the mtDNA data show the arrival and continuity of the house mouse population to the present day, while in Greenland the data suggest the arrival, subsequent extinction and recolonization of house mice - in both places mirroring the history of the European human host populations. If house mice arrived in Newfoundland with the Viking settlers at all, then, like the humans, their presence was also fleeting and left no genetic trace. The continuity of mtDNA haplotype in Iceland over 1000 years illustrates that mtDNA can retain the signature of the ancestral house mouse founders. We also show that, in terms of genetic variability, house mouse populations may also track their host human populations.

Two new Eimeria species (Protozoa: Eimeriidae) from wild rock ptarmigans, Lagopus muta islandorum, in Iceland

One hundred rock ptarmigans, Lagopus muta islandorum (Faber, 1822), were collected in early October 2006 in northeastern Iceland and examined for coccidian parasites. Two Eimeria species were identified, and each is described as a new species. Sporulated oocysts of one species are ellipsoidal, 24.9 x 16.6 (19.5-30 x 14.5-19) microm. Oocysts have a small micropyle and a two-layered, smooth wall approximately 1.0 microm thick. An oocyst residuum is absent, but one to three polar granules are present. Sporocysts have a rounded end opposite a nipple-like Stieda body and are 14.3 x 6.3 (12-16.5 x 5.5-7) microm. Sporocysts contain one refractile body and a diffuse granular residuum; the entire contents of each sporocyst is enclosed by a thin membrane. Sporulated oocysts of the second eimerian are subspherical, 24.7 x 22.2 (20-28 x 18-24.5) microm. The oocysts are without a micropyle but with a two-layered wall, which is approximately 1.5 microm thick, with the outer layer having a rough surface texture. Oocyst residuum is absent, but one to two polar granules are present. Sporocysts have a rounded end opposite the nipple-like Stieda body atop a prominent sub-Stieda body and are 14.4 x 8.0 (12-15.5 x 6.5-9) microm. Sporocysts contain a diffuse granular residuum, and each sporozoite has two different-sized refractile bodies.

The third newly discovered Eimeria species (Protozoa: Eimeriidae) described from wild reindeer, Rangifer tarandus, in Iceland

Fecal samples from 56 adult reindeer from eastern Iceland were examined for coccidian parasites. One Eimeria species was found in an 8-year-old male. Prevalence of infection was 1.8%; oocyst per gram (opg) value was 150. The coccidium was identified and described as a new species. The sporulated oocysts are ellipsoidal and average size is 30.0 x 21.1 microm. The oocyst has two distinct walls. Wall thickness is approximately 1.0 microm, and the outer wall, approximately four-fifths of total thickness, is generally smooth and appears bicoloured. The outermost portion is light blue, and the innermost portion, yellow to pale brown. The inner wall is dark brown. Oocysts contain a prominent polar granule but are devoid of a micropyle. Oocysts enclose four spindle-shaped sporocysts with a rounded end opposite to the Stieda body. The average size of sporocysts is 15.3 x 6.5 microm. Sporocysts contain a granular sporocyst residuum that usually forms a cluster between the sporozoites and one large refractile body in each sporozoite.

DESCRIPTION OF A NEW EIMERIA SPECIES AND REDESCRIPTION OF EIMERIA MAYERI (PROTOZOA: EIMERIIDAE) FROM WILD REINDEER RANGIFER TARANDUS IN ICELAND

Altogether, 195 fecal samples of reindeer calves (Rangifer tarandus) were collected from the ground in 3 distinct areas in eastern Iceland, where geographically isolated reindeer populations graze during the summer months. The samples were examined for coccidian parasites. Two species were found, and all infections were monospecific. Eimeria mayeri was found in calves in all sampling areas, with 1-4% prevalence and 450-167,700 oocysts per gram (opg). The sporulated oocyst lacks a polar granule but has an inconspicuous micropyle, and a small Stieda body is present on sporocysts, which are ovoid but not pointed as reported in the original description. The other coccidian, found in single calves in 2 of the 3 areas (prevalence 1 and 4%, 150 and 500 opg, respectively) is described here as a new species. The oocysts are ovoid, average 34.9 x 27.6 microm, and have 2 distinct walls. Wall thickness is approximately 1.9 microm, and the outer wall, approximately 3/4 of total thickness, is generally smooth and appears bicolored. The outermost portion is pale red and the innermost portion yellow to pale brown. The inner wall is grey to dark brown and separated from the outer wall by a dark brown line. Oocysts contain a prominent micropyle, approximately 5 microm, and enclose 4 spindle-shaped sporocysts, slightly pointed at the end opposite the Stieda body. Average size of sporocysts is 18.6 x 9.2 microm. Sporocysts contain granular sporocyst residuum and usually 2, sometimes 1, large refractile bodies in each sporozoite.

Digeneans from intertidal molluscs of SW Iceland

The fauna of digenean daughter-sporocysts, rediae, cercariae and metacercariae infecting molluscs Littorina spp., Onoba aculeus. Nucella lapillus and Epheria vincta has been studied in the Skerjafjordur and Grindavik regions of SW Iceland. In total, intramolluscan stages of 19 digenean species were recorded; 14 of them are new for Iceland and one of them, a microphallid named Cercaria islandica I, was unknown. A description of this new microphallid cercaria is provided. In addition, the identification and separation of the intramolluscan stages of some microphallid, renicolid and echinostomatid species are discussed. Consideration is given to difficulties encountered when identifying digenean species found on the coasts of European countries. Problems have arisen largely because larval and adult stages have been described and named independently and in isolation, synonyms are common and many "definitive" descriptions are inadequate or incomplete.

Schistosome cercariae as the causative agent of swimmer's itch in Iceland

During late summer in 1995 to 1997, repeated outbreaks of maculopapular skin eruptions were noted on the legs of children after wading in the pond in the Family Park in Laugardalur, Reykjavík, Iceland. Clinical symptoms developing on the legs resembled those of cercarial dermatitis. An examination of Lymnaea peregra snails from this pond and from the adjacent Lake Tjornin resulted in detection of previously undescribed schistosome cercariae. This is the first report of schistosomes in Iceland and also the most northern occurrence of these parasites in Europe.

[On the biology of the pinworm.]

Pinworm Enterobius spp. has probably been an endemic parasite in humans in Iceland since the colonization of the country more than 1100 years ago. A recent survey on pinworm infections in children in playschools indicated that the pinworm is quite common. The results are published in another article in this issue. In this contribution general knowledge on the biology of the parasite (taxonomy, morphology, distribution, life-cycle, transmission, diagnosis and treatment) is reviewed. Recently, dozens of male pinworms found in a stool sample were identified as Enterobius gregorii. Since no other species identifications have been made in Iceland so far, it is not known if the other pinworm species E. vermicularis also occurs in Iceland.

Histological, histochemical, and fine structural observations on the lymph node of the common seal (Phoca vitulina) and the grey seal (Halichoerus grypus)

BACKGROUND

The recent seal death epizootic prompted interest in their immune system, for which no current morphological data were available.

METHODS

Lymph nodes from adult harbor seals (Phoca vitulina) and grey seals (Halichoerus grypus) were investigated by light microscopy, electron microscopy, and lectin histochemistry.

RESULTS

No significant differences in the lymph node morphology were found between the two species, and the overall organization of the nodes comprises of capsule, trabeculae, cortex, paracortex, and medulla. Capsule and trabeculae are composed of tightly packed collagen and elastic fibrils and are rich in fibroblasts, myofibroblasts, and smooth muscle cells. Unmyelinated nerve fibers are common. The cortex contains numerous secondary follicles with well-developed germinal centers and paracortical areas with high endothelial venules. Antigen-presenting cells and phagocytic macrophages were abundantly present. The medullary cords contain numerous plasma cells. Fibroblastic reticulum cells are common throughout the parenchyma and transverse the sinus. Marginal, radial, and medullary sinuses are lined by littoral cells. The visceral lining of the sinuses is marked by macrophages and by numerous mast cells.

CONCLUSIONS

The morphology of seal lymph nodes does not differ significantly from that of terrestrial mammals. Earlier functional conclusions concerning seal lymph nodes are substantiated by this morphological study.

[Dermatitis in cats and humans caused by Cheyletiella mites reported in Iceland.]

Cheyletiella mites (Acarina) are ectoparasites that infest cats, dogs and rabbits in many countries of the world. Upon contact with infested animals the mites may temporarily produce grouped, erythematous macules on the skin of humans which rapidly develop a central, vesicular papule. These signs are most often found on the arms and the trunk. Recently these typical signs were observed on the skin of the members of two different Icelandic families which both kept a Persian cat. An examination for ectoparasites on the cats revealed that both were infested by Cheyletiellaparasitovorax. It is unknown how and when the parasite was transmitted to Iceland.

[Zoonotic parasites of cats and dogs found in playground sandboxes in the Reykjavik area, Iceland.]

Recent surveys on the parasites of household cats and dogs in Iceland have revealed the zoonotic protozoans Cryptosporidium parvwn and Toxoplasma gondii and the zoonotic nematodes Toxocara cati and T. canis. Furthermore, a Giardia sp., recently found in cats in Iceland, is also suspected to be a zoonotic parasite. In Iceland children frequently play in open sandboxes commonly found at kindergartens, in public areas or in private gardens. During the cold months of the year, when the soil is frequently frozen, cats frequently visit these sandboxes and dig their faeces in the dry and loose sand. To evaluate the risk of zoonotic infections, altogether 32 sandboxes in the Reykjavik area in SW-Iceland were examined for the presence of cat and dog protozoan and helminth parasites. Systematically collected sand samples (30 ml sand from every square meter of each sandbox), altogether 411 samples, were examined by a modified salt flotation technique. Furthermore, cat and dog faeces were collected from the surface of the sandboxes and also by sieving approximately five liters of sand from every square meter of each sandbox. The faecal samples found were examined by salt flotation and the formalin-ethylacetate concentration method.

Infection studies with canine distemper virus in harbour seals

Infection studies in harbour seal (Phoca vitulina) were conducted with the Snyder-Hill strain of canine distemper virus (CDV) that is virulent for dog and mink. The inoculated seals showed clinical symptoms which were to some degree similar to those observed in CDV infections of sensitive species of carnivores. Viral replication in lymphoid cells was followed by an extended period of immunosuppression. The results did not provide conclusive evidence for viral replication in surface epithelia of seals, and accordingly no spread of the infection to contact seals and mink was demonstrated. The pathogenicity of the infection did not increase upon a second viral passage in seal. The serological data showed that CDV-infected seals mounted an early virus specific antibody response. Overall, the results indicated that the harbour seal was not especially sensitive to CDV infection. The differences in the in vivo biological properties of CDV and PDV add to the distinction between these viruses at the genomic and antigenic levels.

Histological investigations on the thyroid glands of marine mammals (Phoca vitulina, Phocoena phocoena) and the possible implications of marine pollution

In 1988 and 1989, thousands of harbor seals (Phoca vitulina) died in the North Sea from phocine distemper infection. The morphology of thyroid glands from 40 harbor seals found dead on the North Sea coastlines of Schleswig-Holstein, Federal Republic of Germany, during an epizootic of phocine distemper, was compared with the morphology of thyroid glands from five healthy harbor seals collected in Iceland. Thyroid glands from seven harbor porpoises (Phocoena phocoena) found dead in 1990 on the North Sea coastlines also were evaluated. Colloid depletion and fibrosis were found in the thyroid glands of harbor seals which died during the epizootic, but not in animals from Iceland. Thyroid glands of the porpoises showed similar lesions, but to a lesser degree, than those observed in the North Sea seals.

A safe method for repeatedly immobilizing seals

Phocid seals were immobilized safely and repeatedly, using a combination of ketamine and diazepam at mean IM or IV dosages of 1.5 mg/kg and 0.05 mg/kg, respectively. Induction and recovery were smoother than with ketamine used alone. Experimentally induced pneumonia did not alter the effects of the drugs, thus attesting to the safety of the ketamine-diazepam combination.