Ixodes ricinus, the castor bean tick, is a chiefly species of hard-bodied tick. It may reach a length of when engorged with a blood meal, and can transmit both bacterial and viral such as the causative agents of Lyme disease and tick-borne encephalitis.
Description
In common with other species of
Ixodes,
I. ricinus has no eyes and is not ornate; it has no festoons (wrinkles along the posterior margin). The
palpi are longer than they are wide, and an anal groove is above the
anus.
It has a hard dorsal shield which covers the entire
opisthosoma (abdomen), but only part of it in females and nymphs.
is the largest of the three common species of
Ixodes in the
British Isles (the other two being
Ixodes canisuga, the British dog tick, and
I. trianguliceps, the vole tick). Adult males are long, and unfed nymphs are long; females are long before feeding and long when engorged.
Distribution
Ixodes ricinus is found across
Europe and into neighbouring parts of
North Africa and the
Middle East, extending as far north as
Iceland and as far east as parts of
Russia.
Its northern limit seems to be determined by environmental factors, including
temperature, since a series of mild winters in
Scandinavia coincided with an expansion northwards in the range of
I. ricinus.
I. ricinus is most frequent in habitats where its hosts are plentiful, including , heaths and .
Lifecycle
Ixodes ricinus has a three-host lifecycle, which usually takes 2–3 years to complete, although it can take from 1 to 6 years in extreme cases.
Adults feed on large mammals such as
sheep,
cattle,
,
deer,
, and
for 6–13 days, before dropping off. An engorged female lays several thousand eggs and subsequently dies.
The
that hatch do not actively seek a host, and usually feed on
Insectivora (order
Eulipotyphla), although they may also find
,
,
,
, or
.
[Mikula, P., Hromada, M., Koleničová, A., Pjenčák, P., Fulín, M., Olekšák, M., 2011. Prevalence of Ticks of birds in Slovak Karst. Folia oecologica presoviensis 5(4): 56-64.] They feed for 3–5 days before dropping off and
ecdysis. The resulting nymphs then ascend
or twigs to seek their next host, but must return to the moist
microclimate at the soil surface if they become
dehydration.
The nymphs feed on small to medium-sized mammals.
Disease transmission
A number of tick-borne diseases can be transmitted by
I. ricinus to a variety of
mammal hosts.
can be infected with
Lyme disease (borreliosis), caused by the
spirochaete bacteria Borrelia burgdorferi,
Borrelia afzelii, and
Borrelia garinii. Cattle can become infected with
babesiosis (from the protozoans
Babesia divergens,
Babesia bovis, and
B. ovis), Lyme disease (from
B. burgdorferi), sheep tick pyemia (
Staphylococcus aureus), cattle tick-borne fever (
Anaplasma phagocytophila),
Q fever (
Coxiella burnetii), Boutonneuse fever (
Rickettsia conorii), and the bacterium
Anaplasma marginale.
may be infected with Lyme disease,
Anaplasma phagocytophila, and the viral infection
louping ill. Humans can become infected with Lyme disease, louping ill, Q fever, and tick-borne encephalitis,
and sensitised
to mammalian red meat (and derived-products), known as alpha-gal allergy.
The reservoir hosts for the predominant Lymes causing bacteria (
Borrelia burgdorferi) are generally smaller vertebrate species - such as birds and rodents - rather than Deer, which are not considered main transmitters of the disease despite the public perception.
It is, therefore, more commonly transmitted to humans during the nymph stage. This does not discount Deer as reservoir hosts for other bacteria, such as
Anaplasma phagocytophila and
Babesia divergens.
Natural enemies
The
parasitic wasp Ixodiphagus hookeri lays its eggs inside castor bean ticks, though the castor bean tick is not
I. hookeri's sole host.
Taxonomic history
The scientific name of the castor bean tick dates back to the starting point of zoological nomenclature, the 1758 tenth edition of
Carl Linnaeus'
Systema Naturae, where it appeared as
Acarus ricinus. Pierre André Latreille split the new genus
Ixodes from Linnaeus'
Acarus (which at that time contained all known ticks and
), and
I. ricinus was chosen as the
type species.
It has subsequently been redescribed under a number of
and subsequent combinations into different genera; these synonyms include
Acarus ricinoides,
Cynorhaestes reduvius,
Cynorhaestes ricinus,
Ixodes megathyreus,
Ixodes bipunctatus,
Cynorhaestes hermanni,
Crotonus ricinus,
Ixodes trabeatus,
Ixodes plumbeus,
Ixodes reduvius,
Ixodes pustularum,
Ixodes fodiens,
Ixodes rufus,
Ixodes sulcatus and
Ixodes sciuri.
See also
-
Ticks of domestic animals
External links
