Larvae and nymphs of Ixodes loricatus Neumann, 1899 ticks (confirmed by morphological characters and by comparison of 16S mitochondrial rDNA sequences) were collected from Sigmodontinae Wagner, rodents in central and northern Argentina and Uruguay. A total of 100 larvae and 38 nymphs of I. loricatus were collected on the genera Akodon Meyen (n = 36 individuals), Calomys Waterhouse (n = 2), Oligoryzomys Bang (n = 12), Oxymycterus Waterhouse (n = 9), and Scapteromys Waterhouse (n = 13). 72 larvae and 18 nymphs were collected on Akodon. Adults of I. loricatus were found in central Argentina and Uruguay on Didelphimorphia of the genera Didelphis Linnaeus and Lutreolina Thomas. Ixodes loricatus has been considered a species with strict total specificity to Didelphimorphia. Our results show that this statement may not be justified. Sigmodontinae rodents are sympatric and share habitats with the phylogenetically distant Didelphimorphia; infestation with I. loricatus seems to be its consequence. We tentatively consider I. loricatus moderately specific to Didelphimorphia.Centro de Estudios Parasitológicos y de Vectore

Beldomenico, P. M.

Guglielmone, A. A.

Lareschi, Marcela

Mangold, A. J.

Nava, Santiago

Venzal, J. M.

Zerpa, C.

Parasite

English

SEDICI - Repositorio de la UNLP

SIGMODONTINAE RODENTS AS HOSTS FOR LARVAE AND NYMPHS 
of  Ixodes  l or icatus N eumann , 1899 (Ac ar i: Ixod id ae)
NAVA S.*. LARESCHI M.*, BELDOMENICO P.M. **, ZERPA C.***, VENZAL J.M.****, MANGOLD A.J.*** *
& GUGLIELMONE A.A.*****
Summary:
Larvae and nymphs of Ixodes loricatus Neumann, 1899 ticks 
(confirmed by morphological characters and by comparison of 
16S mitochondrial rDNA  sequences) were collected from 
Sigmodontinae W agner, rodents in central and northern Argentina 
and Uruguay. A  total of 100 larvae and 38 nymphs of I. loricatus 
were collected on the genera Akodon Meyen (n =  3 6  
individuals), Calomys Waterhouse (n =  2), Oligoryzomys Bang 
(n =  1 2), Oxymycterus Waterhouse (n =  9), and Scapleromys 
W aterhouse (n =  13). 7 2  larvae and 18 nymphs were collected 
on Akodon. Adults of I. loricatus were found in central Argentina 
and Uruguay on D idelphimorphia of the genera Didelphis Linnaeus 
and Lutreolina Thomas. Ixodes loricatus has been considered a 
species w ith strict total specificity to D idelphimorphia. Our results 
show that this statement may not be justified. Sigmodontinae 
rodents are sympatric and share habitats w ith the phylogenetically 
distant D idelphimorphia; infestation w ith I. loricatus seems to be its 
consequence. W e tentatively consider I. loricatus moderately 
specific to D idelphimorphia.
KEY WORDS : Ixodidae, Ixodes loricatus, larva, nymph, hosts, Rodentia, 
Sigmodontinae, Didelphimorphia, Didelphinae, Argentina, Uruguay.
Résumé : R o n g e u r s  sig m o d o n t in a e  h ô t e s  d e s  la rv es e t  d e s  
NYMPHES D’IXODES LORICATUS NeUMANN, 1899 (ACARI : IXODIDAE)
Les larves et nymphes d'Ixodes loricatus Neumann, 18 9 9  
(reconnues par leurs caractères morphologiques et par 
comparaison avec des séquences de l'ADN r 16S mitochondrial) 
ont été recueillies sur les rongeurs Sigmodontinae, au centre et 
nord de l'Argentine et en Uruguay. Un total de 10 0  larves et 
3 8  nymphes de I. loricatus ont été recueillies sur les genres 
Akodon Meyen (n =  3 6  individus), Calomys Waterhouse (n =  2), 
O ligoryzomys Bang (n =  12), Oxymycterus Waterhouse (n =  9), 
et Scapteromys Waterhouse (n =  13 ) . 7 2  larves et 18 nymphes 
ont été recueillies sur Akodon. Des adultes de I. loricatus ont été 
trouvés au centre de l'Argentine et en Uruguay sur des 
Didelphimorphia du genre Didelphis Linnaeus et Lutreolina Thomas. 
L'espèce I. loricatus a été considerée comme spécifique pour les 
Didelphimorphia. Nos résultats montrent que cette notion n'est 
peut-être pas justifiée. Les rongeurs Sigmodontinae partagent leur 
habitat avec les Didelphimorphia, phylogenétiquement éloignés, et 
l'infection par I. loricatus semble en être la conséquence. Nous 
considérons que I. loricatus est modérément spécifique des 
Didelphimorphia.
MOTS CLÉS : Ixodidae, Ixodes loricatus, larve, nymphe, hôtes, Rodentia, 
Sigmodontinae, Didelphimorphia, Didelphinae, Argentine, Uruguay.
N
ew world marsupials (Didelphimorphia) are 
hosts for all parasitic stages of Ixodes loricatus 
Neumann, 1899, a species found in Argentina, 
Brazil, Mexico, Paraguay, Uruguay, Venezuela and 
Guatemala (Guglielmone et al., 2003). Venzal et al. 
(2003) and Beldomenico et al. (2003) reported that 
immature stages of I. loricatus have been found on dif­
ferent species of Sigmodontinae Wagner, rodents in 
Argentina and Uruguay. Lareschi (1996), Lareschi et al.
* Centro de Estudios Parasitológicos y de Vectores, 2 N° 584, CP 1900 
La Plata Argentina.
** Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral, 
Kreder 2805, CP 3080, Esperanza, Santa Fe, Argentina.
*** Facultad de Veterinaria, Universidad Maza, CP 5500 Mendoza, 
Argentina.
**** Departamento de Parasitología Veterinaria, Facultad de Veteri­
naria, Universidad de la República, Alberto Lasplaces 1550, CP 11600 
Montevideo, Uruguay.
***** Instituto Nacional de Tecnología Agropecuaria, Estación Expe­
rimental Agropecuaria Rafaela, Casilla de Correo 22, CP 2300 Rafaela, 
Santa Fe, Argentina.
Correspondence: Alberto A. Guglielmone.
Fax: #54 3492 440114 -  E-mail: aguglielmone@rafaela.inta.gov.ar
(2003) and Nava et al. (2003) also registered its pre­
sence on Argentinian Sigmodontinae without specifying 
the tick stages found. There are also several Brazilian 
fi ings of I. loricatus immature stages on “house rat”, 
“wild rodent” and Oryzomys Baird spp. (Cooley & 
Kohls, 1945; Barros Battesti & Knysak, 1999).
Rodents may be of importance for the cycle of I. lori­
catus, a species considered with strict total specificity 
to neotropical marsupials by Hoogstraal & Aeschlimann 
(1982). In this article we present results of studies with 
Sigmodontinae rodents to sustain the hypothesis that
I. loricatus is not strict totally dependent on Didelphi­
morphia.
MATERIALS AND METHODS
I
xodes loricatus ticks were collected from rodents 
and marsupials trapped for parasite surveys in cen­
tral (Buenos Aires and Santa Fe provinces) and nor­
thern (province of Salta) Argentina, and Uruguay. Adult 
ticks were diagnosed following Cooley & Kohls (1945)
Parasite, 2004, 11, 411-414 Note de recherche 411
Article available at http://www.parasite-journal.org or http://dx.doi.org/10.1051/parasite/2004114411
NAVA S., LARESCHI M., BELDOMENICO P.M. ETAL.
and Boero (1957) to separate them from the related 
Ixodes luciae  Sénevet, 1940. Nymphs of I. loricatus were 
identified following Cooley and Kohls (1945); these 
authors stated that the nymph of I. loricatus was unk­
nown (p. 10), but provided description and figures of 
the nymph (pp. 188-189). No figures are available for 
the identification of the larva of I. loricatus. All tick spe­
cimens classified as larva or nymph of I. loricatus were 
compared with known material and unpublished redes­
criptions of I. loricatus kindly provided by D.M. Barros 
Battesti (Instituto Butantan, Sao Paulo, Brazil). DNA was 
extracted from specimens of Uruguay and Argentina, 
representing the most southern and northern localities 
of our collection of I. loricatus, to be compared with 
the sequence of I. loricatus 16S mitochondrial rDNA 
deposited in GenBank (accession N° U95892) and also 
with the related species I. luciae  (U95894), following 
Mangold et al. (1998). A difference of 2 % in the base 
pairs sequences of 16S rDNA was considered the 
maximum for intraspecific variation (Kain et al., 1999). 
The tick specimens used in the study are deposited in 
the following collections: Uruguay, Universidad de la 
República, Facultad de Veterinaria, Departamento de 
Parasitología, Montevideo; Argentina, Universidad 
Nacional de La Plata, Centro de Estudio Parasitológicos 
y Vectores, La Plata; Universidad Nacional del Litoral, 
Facultad de Veterinaria, Esperanza and Universidad 
Nacional de Rosario, Facultad de Ciencias Veterinarias, 
Casilda.
RESULTS ____ ____
T he sequence of l6S mithocondrial rDNA of I . lori- 
catus tick from northern Argentina and southern 
Uruguay are deposited in the GenBank under the 
accession numbers AY510268 and AY510269, respecti­
vely. The difference between DNA sequences of Argen­
tinean and Uruguayan tick populations differed by 0.5 % 
and 1.8 % with the sequence of I . loricatus deposited 
in the GenBank, respectively, and both differed 1.3 % 
between themselves. The difference with I . luciae ranged 
from 4.3 % to 4.8 %, further confirming the I .  loricatus 
identity of the specimens studied. See figure 1 for 
nucleotide differences of I. loricatus and I. luciae.
A total of 100 larvae and 38 nymphs of I. loricatus were 
collected from 36 Akodon  Meyen, two Calomys Wate­
rhouse, 12 O ligoryzomys Bang, nine Oxymycterus 
Waterhouse and 13 Scapteromys Waterhouse (Table I). 
72 larvae and 18 nymphs were found on A kodon. In 
our sample, A kodon  appeared to be more parasitized 
than other Sigmodontinae (P = 0.0468, Yate's corrected 
chi-square). Two females of I. loricatus w ere  collected 
from a Lutreolina crassicaudata (Desmarest) at La Balan- 
dra, Argentina (July 2001, collectors: S. Nava & M. Lares- 
chi), one male from a D idelphis albiventris Lund at
Fig. 1. -  N u cle o tid e  d iffe re n c e s  fo u n d  in  th e  16S rD N A s e q u e n c e  o f  
th e  I. loricatus fro m  A rgen tin a, B raz il, U ru g u ay  an d  I. luciae  fro m  
Peru.
A dot indicates that the sequence at that point is identical to the 
top sequence. Numbers (to be read in the vertical) refer to posi­
tions in the alignment.
Funes, Argentina (Oct. 7, 2002, collector: C. Zerpa), six 
females ticks from two D. albiventris at Santa Clara de 
Saguier (June 14, 2003, collector: P.M. Beldoménico) 
and three females from a D. albiventris at Barra del 
Arroyo Maldonado, Uruguay (Nov. 7, 1999, collector: 
J.M. Venzal). No larva or nymph of I. loricatus were 
found on these marsupials.
DISCUSSION
T he findings of I. loricatus on Sigmodontinae com­
prise a wide area of its southern distribution. The 
only known record of I. loricatus further south 
of Barra Arroyo Maldonado is that of an engorged 
female from an unknown host (Tierra del Fuego, 
Argentina; C. Berg's Collection), from the southern tip 
of America (Neumann, 1901). The findings in Argen­
tina and Uruguay appear to indicate that rodents may 
be more than accidental hosts for immature stages of 
this tick species. In this sense, I. loricatus resembles 
the related I. luciae, whose larva and nymphs are fre­
quently found on rodents according to Hoogstraal & 
Aeschlimann (1982).
A compilation (A.A. Guglielmone, unpublished, avai­
lable upon request) of 194 literature host records of
I. loricatus, comprising 180 localities from Mexico to 
Argentina, showed the preference of this tick species 
for Didelphimorphia (82 % of records). However, apart 
from some unusual records on Primates (Keirans, 
1982), Xenarthra (Cooley & Kohls, 1945) or Carnivora 
(Aragão, 1918; Barros & Baggio, 1992) that could be 
considered accidental, 15 % of records of I. loricatus 
(all stages) had Rodentia as hosts.
Most larvae and nymphs of I. loricatus were found on 
A kodon , mainly on A kodon a z a r a e  (Fischer). Previous 
studies in central Argentina stressed that A kodon  is 
more prone to be infested with this tick species than 
other sympatric Sigmodontinae (Lareschi, 1996; Nava 
et al., 2003; Lareschi et al., 2003). It would be of value 
to perform epidemiological studies to quantify level of
412 Note de recherche Parasite, 2004, 11, 411-414
1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 3
7 8 9 2 2 5 8 9 9 9 2 3 3 3 3 6 6 7 7 5
4 4 2 7 8 9 9 2 3 9 3 5 7 8 9 6 7 1 2 8
I . l o r i c a t u s Ar g GTATAGAGGA GTAGTAAAAT
I . l o r i c a t u s B r a .A ...............G.
I . l o r i c a t u s U ru ...............GAA. . . . T . . . G . .
I . l u c i a e  P e r u AAGGGAGAAG A . TAATG. GA
S ig m o d o n tin a e  as h o s ts  f o r  Ixodes loricati's
Coordinates
Tick stage Host Locality S W Date Collector
Argentina, province of Buenos Aires
7 LL 2 NN 5 Akodon azarae Hudson 34°45' 58°06' Apr. 1995 S. Nava & M. Lareschi
1 LL 1 Akodon azarae - - Sep. 1995 _
4 LL 1 NN 2 Akodon azarae INTA Delta del Paraná 34°09' 58°57’ Jan. 1994 M. Lareschi, M. Lopez & S. Nava
1 LL 1 NN 1 Akodon azarae - - Mar. 1994 -
9 LL 3 Akodon azarae - - Apr. 1994 _
1 NN 1 Akodon azarae - - July 1994 _
2 LL 1 NN 1 Akodon azarae - - Jan. 1995 _
2 LL 1 Akodon azarae La Balandra 34°56' 57°42' Dec. 1995 _
2 LL 1 Akodon azarae Punta Lara 34°47' 58°01' Mar. 1990 M. Lareschi
1 LL 1 Akodon azarae - - Sep. 1990 -
2 LL 1 Akodon azarae - - May 1991 _
2 LL 2 Akodon azarae - - June 1991 _
2 LL 2 Akodon azarae - - Oct. 1996 S. Nava & M. Lareschi
16 LL 6 NN 4 Akodon azarae San Nicolás 33°20' 60°13' Jan. 2001 _
1 NN 1 Oligoryzomys delticola Hudson 34°45' 58°06' Sep. 1995 _
3 LL 1 Oligoryzomys flavescens - - Sep. 1995 -
4 LL 3 Oligoryzomys flavescens Punta Lara 34°47' 58°01' Mar. 1990 M. Lareschi
2 LL 1 Oligoryzomys flavescens - - Aug. 1990 -
1 LL 1 NN 1 Oligoryzomys flavescens - - Apr. 1991 -
1 NN 1 Oligoryzomys flavescens Ramallo 33°32' 59°52' Feb. 2000 S. Nava & M. Lareschi
3 NN 1 Oxymycterus rufus La Balandra 34°56' 57°42' Oct. 1996 -
1 LL 1 Oxymycterus rufus Punta Lara 34°47' 58°01' Mar. 1990 M. Lareschi
1 LL 1 Oxymycterus rufus - - Nov. 1990 -
2 NN 2 Oxymycterus rufus - - Dec. 1990 -
1 LL 1 Oxymycterus rufus - - July 1991 -
1 LL 1 Oxymycterus rufus - - Aug. 1991 -
1 LL 1 Oxymycterus rufus - - Nov. 1991 -
1 LL 1 NN 2 Scapteromys aquaticus - - Mar. 1990 -
1 LL 1 NN 1 Scapteromys aquaticus - - Aug. 1990 -
1 NN 1 Scapteromys aquaticus - - Nov. 1990 -
1 LL 1 NN 2 Scaptemmys aquaticus - - Jan. 1991 -
1 LL 1 Scaptemmys aquaticus - - Apr. 1991 -
1 NN 1 Scapteromys aquaticus - - Sep. 1991 -
4 LL 2 NN 3 Scapteromys aquaticus - - Nov. 1991 -
1 NN 1 Scapteromys aquaticus - - Dec. 1991 -
Argentina, province of Salta
1 NN 1 Akodon  spp Parque Nacional El Rey 24°15' 64°40' Dec. 5, 2000 P.M. Beldomenico
1 NN 1 LL 1 Calomys spp - - Dec. 4, 2000 -
1 NN 1 Calomys spp - - June 6, 2001 -
Argentina, province o f Santa Fe
13 LL 1 NN 3 Akodon azarae Funes 32°55 ' 60°48 ' Oct. 2001 C. Zerpa
4 LL 4NN 3 Akodon azarae - - Oct. 2002 -
3 LL 1 NN 3 Oligoryzomys flavescens - - Ju ne 2001 -
5 LL 1 NN 3 Akodon  spp. Santa Clara de Saguier 31°20’ 6 l°49 ' June 14, 2003 P.M. Beldom énico
Uruguay, department Canelones
1 NN 1 Oligoryzomys flavescens Solymar Norte 34°47' 55°56' Mar. 8, 1998 A. Mignone
Uruguay, department Maldonado
1 LL 1 Oxymycterus nasutus Barra Arroyo Maldonado 34°58' 54°56' May 28, 2000 J.M. Venzal
Parasite, 2004, 11, 411-414 Note de recherche 413
Table I. -  Larvae, nymphs and adults of Ixodes loricatus collected on different types of rodents in central and northern Argentina and Uru­
guay.
infestations with larvae and nymphs of I. loricatus on 
sympatric Sigmodontinae.
Sigmodontinae are separated phylogenetically from 
Didelphimorphia. Its infestation with I. loricatus may 
result from sympatry and sharing of habitat with Didel­
phimorphia. Research on the biotic fitness of I. lorica­
tus feeding on rodents are needed to define more pre­
cisely the index of host specificity of this species
(Poulin & Mouillot, 2003). A kodon a z a r a e  constitutes 
the first target species to this aim in central Argentina. 
In any event, the statement of Hoogstraal & Aeschli- 
mann (1982) considering I. loricatus with strict total 
specificity to Didelphimorphia does not appear justi­
fied. Following the classification of tick host specificity 
proposed by these authors, we tentatively consider I. lori­
catus moderately specific to Didelphimorphia.
NAVA S., LARESCHI M., BELDOMENICO P.M. ETAL.
The study was not conducted to determine the seaso­
nality of I. loricatus; nevertheless, the wide distribu­
tion of records of larvae and nymphs of this species 
along the year becomes evident. Additional studies are 
needed to known seasonalities of all I. loricatus para­
sitic stages.
ACKNOWLEDGEMENTS
W e greatly appreciate the collaboration ofD.M. Barros Battesti who provided valuable unpublished material to identify larvae and 
nymphs of I. loricatus.
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414 Note de recherche Parasite, 2004, 11, 411-414


Sigmodontinae rodents as hosts for larvae and nymphs of Ixodes loricatus Neumann, 1899 (Acari: Ixodidae)

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Sigmodontinae rodents as hosts for larvae and nymphs of Ixodes loricatus Neumann, 1899 (Acari: Ixodidae)

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