Introduction

The tick Ixodes uriae White 1852 (Acari: Ixodidae) is widely distributed throughout circumpolar regions (Murray 1967; Health 1977). They are usually associated with seabird colonies, and more than 50 species have been recorded as host of this ectoparasite (Wilson 1970; Eveleigh and Threlfall 1974; Bergström et al. 1999). Tick effects on the host include delay in chick growth (Morbey 1996), chick mortality (Chastel et al. 1987; Bergström et al. 1999) and even adult mortality (Gauthier-Clerc et al. 1998). Changes in population dynamics have been also reported (Boulinier and Danchin 1996). However, other works show that tick infestations had no effect on different traits such as body mass, haematocrit, behaviour of incubating penguins, fidelity of breeding site or survival after 32 months (Gauthier-Clerc et al. 2003). Ixodes uriae transmits different pathogenic agents like the bacteria Borrelia burdogferi responsible of the Lyme disease (Olsen et al. 1993) and some viruses (flavivirus, orbivirus, phlebovirus or nairovirus) as well (Nuttall 1984; Major et al. 2009). Currently, the known distribution of Ixodes uriae in Antarctica is restricted to Sub-Antarctic islands (Barbosa and Palacios 2009 and references therein) and the Palmer Archipelago (Benoit et al. 2007); however, there is no information about its distribution along the Antarctic Peninsula including the South Shetlands.

Information about the presence and distribution of parasite and pathogens in Antarctica is scarce and fragmented (Barbosa and Palacios 2009), and there is a need to know what is normal and aberrant in relation to factors potentially affecting the health of Antarctic wildlife (Kerry et al. 1999). To know the distribution of ticks is of great importance because they cause negative effects on seabird populations (Chastel et al. 1987; Bergström et al. 1999) but also for the possibility of zoonotic transmission. The aim of this note is to describe the distribution of this parasite in several locations along the western coast of Antarctic Peninsula.

Materials and methods

We visited several penguin rookeries located in the South Shetlands and along the Antarctic Peninsula in January of 2007 (Stranger Point, King George Island), 2009 (Devil’s Point, Livingston Island; Hannah Point, Livingston Island; Deception Island) and 2010 [Stranger Point, King George Island; Hannah Point, Livingston Island; Deception Island; George Point, Ronge island; Yalour Island; Avian Island (Fig. 1)]. The penguin species and the population size present in each location is as follows: Stranger Point, King George Island (gentoo penguin—Pygoscelis papua [3,764 pairs, Carlini et al. 2009] and adélie penguin—Pygoscelis adeliae [3,412 pairs, Carlini et al. 2009]); Hannah Point, Livingston Island (chinstrap penguin—Pygoscelis antarctica [754 pairs, Lynch et al. 2008] and gentoo penguin [1,885 pairs, Lynch et al. 2008]); Devil’s Point, Livingston Island (chinstrap [50 pairs, own data] and gentoo penguin [3,000 pairs, own data]); Vapour Col, Deception Island (chinstrap penguin [12,000 pairs, own data]); George Point, Ronge Island (chinstrap [354 pairs, Lynch et al. 2008] and gentoo penguin [2,464 pairs, Lynch et al. 2008]); Yalour Island (adélie penguin [5,558 pairs, Lynch et al. 2008]) and Avian Island (adélie penguin [35,600 pairs, Management plan of ASPA number 117). Ticks were searched for beneath stones located within the penguin colonies. Stones were chosen by its proximity to the penguin colonies (range of distance from the colony 0 to 3 m) and by its size (not too big to be lifted). In 2007 and 2009, ticks were looked for opportunistically turning up stones until the ticks were found. In 2010, a more detailed survey was undertaken lifting between 50 and 100 stones in each location surveyed. During the survey, penguins were during the guard phase in all the locations. Relative abundance was calculated as the number of stone with ticks divided by the total number of stones prospected. The approximated number of ticks under each stone was also recorded.

Fig. 1
figure 1

Localities where ticks were sampled. Black circles: ticks present from this study. Stars: ticks present taken from literature. White circles: ticks absent from this study. 1. King George Island (Stranger Point, 62º15′S 58º37′W), 2. Livingston Island (Hannah Point, 62º39′S 60º36′W), 3. Livingston Island (Devils Point, 62º40′S 61º13′W), 4. Deception Island (Vapour Col, 63º00′S 60º40′W), 5. Ronge Island (George Point, 64º40′S 62º40′W), 6. Humble island (64º46′S 64º06′W), 7. Doumer Island (64º51′S 63º55′W), 8. Petermann Island (65º11′S 64º10′W), 9. Yalour Island (65º15′S 64º11′W), 10. Avian Island (67º46′S 68º43′W)

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Ticks were collected and preserved in 70% ethanol. Identification was carried out according to keys for this species (Hoogstraal 1954).

Results and discussion

Ticks found were identified as Ixodes uriae. Eggs, larvae, nymphs, gravid females and males were found in Stranger Point (King George Island), Devil’s Point (Livingston Island), Hannah Point (Livingston Island), Vapour Col (Deception Island) and George Point (Ronge Island). No ticks were found in Yalour Island and Avian Island. Mean number of ticks (x ± standard error) found in each location and relative abundance of stones with ticks were as follows: Stranger Point: 48.00 ± 8.18, 9%—9/100; Devil’s Point: 57.00 ± 10.83, 8%—4/50; Hannah Point: 38.57 ± 8.18, 10%—5/50; Vapour Col: 49.16 ± 8.84, 26%—13/50; George Point: 1.00 ± 15.32, 2%—2/100; Yalour Island: 0.00 ± 0.00, 0%—0/100; Avian Island: 0.00 ± 0.00 0%—0/150.

From 2003 till 2010, these rookeries have been visited and penguins captured for different studies. The number of penguins captured ranged from 25 individuals in Devil’s Point to more than a thousand in Vapour Col colony. No birds infected with ticks were found in these locations. In Antarctica, ticks seem to have only one blood meal per year (Lee and Baust 1987), and therefore, it could be difficult to find ticks on the hosts. However, Frenot et al. (2001) found infested penguins early in the breeding period and prevalence and infestation intensity increased rapidly during this period. Nevertheless, these authors carried out their study in Sub-Antarctic islands where the environmental conditions are warmer than in the Antarctic Peninsula. Therefore, it is likely that feeding activity of ticks could be reduced in Antarctic Peninsula making more difficult to find the ticks on the penguins.

In spite of the reported presence of ticks at least since the early 1980s in the Palmer Archipelago (64º46′S 64º03′W) (Lee and Baust 1982; see also Casanueva and Moyano 2000), it has not been published any report on the distribution of this parasite in the western coast of the Antarctic Peninsula. Only recently, Lynch et al. (2010) reported the presence of a tick infestation on Adèlie penguins in Peterman Island during 2006/2007 and 2007/2008 breeding seasons. Therefore, no data exist to track the evolution of the populations of this parasite in Antarctica. This study is therefore the first one to provide results of a survey on the presence of ticks in this Antarctic region. Our results showed that ticks are not distributed evenly along the Antarctic Peninsula being more common and abundant in the northern part and probably absent in the south. This pattern fits with a likely northern origin of the colonization of ticks in Antarctica by means of eggs transport on migratory birds (Health 1977; Smith et al. 1996). This way is also hypothesized for the spreading of Borrelia sp. in the Southern Ocean (Olsen et al. 1995). Conversely, the presence of ticks in Antarctica could be constituted a relic of a Tertiary fauna separated by continental drift (Health 1977). However, detailed molecular studies are needed to account for the colonization and distribution of ticks in Antarctica.

Ticks are vectors of several bacteria and viruses (Olsen et al. 1993; Nuttall 1984). As far as we know excepting three studies carried out in Sub-Antarctic islands (Olsen et al. 1995; Gauthier-Clerc et al. 1999; Major et al. 2009), no other studies give data on the prevalence of these pathogens transmitted by ticks (i.e. Borrelia burdogferi) in continental Antarctica. These pathogens are expected to be present in Antarctica although in some cases in spite of the presence of ticks, B. burdogferi has not been detected (Olsen et al. 1995). Studies on this topic are also needed.

Finally, in Antarctic Peninsula temperatures have risen in the last 50 years (Steig et al. 2009). Ixodes uriae as an ectoparasite might be favoured by this fact as occurs with other tick species (Ogden et al. 2006). In fact, an increase in the number of feeding ticks has been related to higher temperatures in warmer years in Antarctic Peninsula (Benoit et al. 2009). Therefore, ticks could be an excellent indicator organism to track climate change in Antarctica.