Aspects of the life cycle of Amblyomma parvum

(Acari: Ixodidae) under natural conditions

Santiago Nava *, Atilio J. Mangold, Alberto A. Guglielmone

Instituto Nacional de Tecnologıa Agropecuaria, Estacion Experimental Agropecuaria Rafaela,

CC 22, CP 2300 Rafaela, Santa Fe, Argentina

Received 6 March 2008; received in revised form 9 May 2008; accepted 22 May 2008

Abstract

Monthly samplings of the rodent Galea musteloides (Caviidae) were carried out from January 2005 to December 2006 in

Quilino, Cordoba Province, Argentina, to determine the seasonal distribution of immature stages of Amblyomma parvum. In the

same locality, cattle and goats were also monthly examined to asses the seasonality of the females of this species. Engorged ticks

collected on their natural hosts were maintained in the laboratory at 25 8C and 83–86% relative humidity to study biological

parameters, and groups of larvae and nymphs were also maintained at three different photoperiods [12 h light (L)–12 h dark (D), 14

L–10 D, and 10 L–14 D]. Larvae were found from late summer to early winter with the peak in autumn, nymphs were collected from

early winter to early spring with the peak in middle winter, and females were detected on cattle and goats during spring and summer,

with the peak in early and middle summer. The pre-moult-period of engorged immature ticks exposed at different photoperiods in

the laboratory show no indication of morphogenetic diapause, being the maximum period 16.4 days for larvae and 21.8 days for

nymphs. The difference in the mean engorgement weight of nymphs moulting to females (6.2 mg � 1.8) and to males

(2.1 mg � 0.1) was statistically significant (P < 0.01), but the difference in the pre-moult period of the nymphs moulting to

females (20.1 days � 2.0) and to males (18 days � 2.0) was not significant (P > 0.01). The average weight of females was

206.1 mg � 23.6, the mean number of eggs laid was 1500.4 � 298.2, the average of pre-oviposition period was 6.5 days � 0.8, and

the minimum incubation period of eggs was 33.1 days � 1.2. There was not significant correlation between the weight of females

and the pre-oviposition period and between weight of immature stages and pre-moult period, but there was significant positive

correlation between weight of females and number of eggs laid. A. parvum has a life cycle under natural conditions with one

generation per year characterized by distinct seasonal peaks of activity for each parasitic stage, where adults are abundant in the

hottest months and the immature stages prevail in the dry season. Apparently, this life cycle is not regulated via diapause. Additional

studies on the life cycle of A. parvum in nature should be performed in other countries to confirm the results obtained in Argentina.

# 2008 Elsevier B.V. All rights reserved.

Keywords: Amblyomma parvum; Seasonality; Life cycle; Argentina

www.elsevier.com/locate/vetpar

Available online at www.sciencedirect.com

Veterinary Parasitology 156 (2008) 270–276

1. Introduction

Amblyomma parvum is a Neotropical tick species

found from southern Mexico to Argentina (Guglielmone

* Corresponding author. Tel.: +54 3492440121;

fax: +54 3492440114.

E-mail address: snava@rafaela.inta.gov.ar (S. Nava).

0304-4017/$ – see front matter # 2008 Elsevier B.V. All rights reserved.

doi:10.1016/j.vetpar.2008.05.029

et al., 2003; Nava et al., 2008). Although the distribution

of this tick species is wide, there is little knowledge of

ecological aspects such as seasonal distribution of

immature stages and biological information of A. parvum

feeding in nature.

Adult of A. parvum feed on several large and

medium-sized mammals species, including domestic

animals (cattle, dog, cat, donkey, goat, horse and sheep)

S. Nava et al. / Veterinary Parasitology 156 (2008) 270–276 271

and man (Nava et al., 2008). Particularly in Argentina,

the findings of adults of A. parvum on domestic animals

such as cattle and goats are frequent (Guglielmone and

Nava, 2006). In contrast, the records of hosts for larvae

and nymphs of A. parvum are less numerous. There are

occasional records of subadults in Argentina on wild

and domestic artiodactyls, on the white-eared opossum

Didelphis albiventris, on the Caviidae (Dolichotinae)

rodent Dolichotis salinicola, and on domestic and wild

carnivores (Ivancovich and Luciani, 1992). Serra Freire

et al. (1996) found immature stages on the Cervidae

Mazama guazoubira in Brazil and Jones et al. (1972) on

the Lagomorpha Sylvilagus brasiliensis in Venezuela.

Dunn (1923) and Floch and Fauran (1958) mention

larvae and nymphs of A. parvum parasitizing wild

rodents in Panama and French Guiana. Early reports of

host-association for the subadults stages should be

considered carefully, because some records were made

before the description of larvae and nymphs by

Guglielmone et al. (1990a) and often do not specify

the characters used to identify the specimens. Recently,

in a monthly survey of birds and rodents conducted in

north-western of Cordoba Province, Nava et al. (2006a)

stated that the Caviidae rodent Galea musteloides is the

principal host for A. parvum subadults.

Guglielmone et al. (1981, 1990b) described infesta-

tions of adults on cattle in Argentina from late spring to

early autumn, and Szabo et al. (2007) found similar

results in Brazil, with host-seeking adults of A. parvum

in summer and autumn. Also in Argentina, Guglielmone

et al. (1991) studied the life cycle of A. parvum in the

laboratory using a colony started with the offspring of

two engorged females obtained from cattle naturally

parasitized. The results of this study showed that the

mean duration of the life cycle was 99.6 days, and the

incubation period of the eggs was the longest part of the

cycle.

Fig. 1. Monthly rainfall and temperature at the stud

A. parvum may have public health and veterinary

importance. Adults frequently infest domestic animals

and man and have been reported to harbour a novel

Rickettsia sp. strain belonging to the spotted fever group

(Pacheco et al., 2007). Knowledge of the ecology of

A. parvum is necessary to design appropriate control

strategies and to make epidemiological inferences. In

this work we describe the seasonal distribution of all

stages of this tick and provide knowledge of its biology

under field and laboratory conditions.

2. Materials and methods

The field study was carried out in Quilino (308120S,

648320W; altitude 450 m), Cordoba Province Argentina.

The area corresponds to the Western Chaqueno District

of the Chaco Phytogeogrpahic Province according to

the definition given by Cabrera (1994). This district is

characterized by no permanent watercourses, and the

vegetation consists of forests of Aspidosperma queb-

racho blanco, Prosopis nigra, Prosopis pugionata,

Cercidium australe, Zizyphus mistol and Stetsonia

coryne, bushes belonging to the species Larrea

divaricada, Mymozyganthus carinatus, Senna aphylla,

Mimosa detinens, Celtis pallida and Geoffroea deco-

ticans and a herbaceous stratum formed mainly by

perennial grasses. The study area has a climate with a

mean temperature of 24 8C in summer and 12 8C in

winter, and rainfall concentrated on summer (500–

800 mm annually). Fig. 1 includes the monthly rain and

temperature of the study site along the sampling period.

The seasonal distribution of immature stages of A.

parvum was determined by examining G. musteloides

(Caviidae: Caviinae), which were captured in 50

Tomahawk live-trap-type (32 cm in length, 10 cm in

height and 10 cm in width) placed in the field twice a

month. Traps were set at 5 m intervals baited with

y area from January 2005 to December 2006.

S. Nava et al. / Veterinary Parasitology 156 (2008) 270–276272

carrot, and the captured rodents were processed and

examined for ticks following the methodology detailed

in Nava et al. (2006a).

To assess the seasonality of adults ticks, counts were

performed monthly during 2 years on one side of 5 cows

and 5 goats taken at random in the same properties

where rodents were caught. For the statistical analysis

the number of collected ticks on cows and goats was

duplicated. Cattle and goats were not treated with

acaricides through the study period.

The ticks removed from rodents were preserved in

96% ethanol and identified according to Guglielmone

et al. (1990a). The engorged larvae and nymphs

collected on the examined hosts were maintained at

25 8C � 1 and 80–83% relative humidity until moult-

ing, to obtain nymphs and adults to confirm identifica-

tion. Precise determination of immature ticks can be

done with PCR procedures. Therefore, sequences of a

ca. 460 bp fragment of the mitochondrial 16S rDNA

gene were obtained from representative larvae, nymphs

and adults ticks to be compared to each other and with

those of A. parvum from Argentina deposited in

GenBank. DNA extraction and polymerase chain

reaction (PCR) amplification was set-up as described

Table 1

Percentage of prevalence (P) median (M), first and third quartiles (1Q–3Q) of

musteloides between January 2005 and December 2006 in Quilino, Cordob

Month n Larvae

P

January 2005 4 0

February 2005 9 0

March 2005 2 50

April 2005 2 50

May 2005 6 100

June 2005 9 100

July 2005 10 88.8

August 2005 16 0

September 2005 7 0

October 2005 12 0

November 2005 3 0

December 2005 3 0

January 2006 2 0

February 2006 2 0

March 2006 3 33.3

April 2006 7 28.5

May 2006 10 81.8

June 2006 14 86.6

July 2006 8 12.5

August 2006 16 0

September 2006 6 0

October 2006 11 0

November 2006 7 0

December 2006 3 0

The monthly number of hosts examined for ticks (n) is also indicated.

by Mangold et al. (1998a,b). The sequences were edited

using BioEdit Sequence Alignment Editor (Hall, 1999)

and aligned with Clustal W (Thompson et al., 1994). To

the analysis of the sequences the program Mega version

4.0 (Tamura et al., 2007) was used. The adults ticks

were determined following Guglielmone et al. (1990a)

and Guglielmone and Vinabal (1994). The prevalence

(P), median (M), and first and third quartiles (1Q–3Q)

were obtained for each type of infested host, and the site

of attachment of each tick stage was recorded.

Larvae and nymphs were weighed and maintained in

the laboratory at 25 8C and 83–86% relative humidity,

at three daily photoperiods, namely, 12 h light (L)–12 h

dark (D), 14 L–10 D, and 10 L–14 D. Moulting success

and pre-moult period were recorded, and analysis of

variance (ANOVA) was used to test differences among

photoperiodic regimens. A t-test was used to compare

the weight and pre-moult periods of nymphs moulting to

males or females. Due to the fact that most of the

females were observed on cattle and goats in spring and

summer, where the day length is between 13 h and 14 h,

all engorged females were exposed in the laboratory at

14 L–10 D, 25 8C, and 83–86% relative humidity. The

weight, pre-oviposition period, number of eggs laid and

larvae and nymphs of Amblyomma parvum monthly collected on Galea

a Province, Argentina

Nymphs

M (1Q–3Q) P M (1Q–3Q)

0 0 0

0 0 0

1.5 (0–3) 0 0

4.5 (0–9) 0 0

77 (40–92) 0 0

20 (7.5–32.5) 80 3 (0.5–6)

2 (1–4) 100 19.5 (14–25)

0 93.8 21 (9.5–28)

0 100 12 (1–18)

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 (0–5) 0 0

0 (0–10) 0 0

18.5 (10–29) 0 0

2 (1–5) 21.5 0

0 (0–2) 62.5 4 (0–7.5)

0 87.5 3 (1.5–7)

0 50 0.5 (0–2)

0 9.1 0

0 0 0

0 0 0

S. Nava et al. / Veterinary Parasitology 156 (2008) 270–276 273

Table 2

Percentage of prevalence (P) median (M), first and third quartiles (1Q–

3Q) of females of Amblyomma parvum monthly collected on 5 cattle

and 5 goats between January 2005 and December 2006 in Quilino,

Cordoba Province, Argentina

Month Females on cattle Females on goats

P (%) M (1Q–3Q) P (%) M (1Q–3Q)

January 2005 100 12 (10–17) 100 10 (5–20)

February 2005 100 10 (8–19) 100 10 (10–15)

March 2005 100 8 (6–9) 100 6 (4–11)

April 2005 40 0 (0–4) 100 2 (2–5)

May 2005 0 0 0 0

June 2005 0 0 0 0

July 2005 0 0 0 0

August 2005 0 0 0 0

September 2005 0 0 0 0

October 2005 20 0 (0–1) 20 0 (0–1)

November 2005 60 2 (2–4) 100 6 (4–8)

December 2005 100 4 (2–6) 100 6 (4–9)

January 2006 100 8 (8–14) 100 14 (11–20)

February 2006 100 8 (6–14) 100 10 (8–12)

March 2006 100 4 (3–8) 100 8 (4–10)

April 2006 60 2 (0–3) 60 2 (0–4)

May 2006 0 0 0 0

June 2006 0 0 0 0

July 2006 0 0 0 0

August 2006 0 0 0 0

September 2006 0 0 0 0

October 2006 40 0 (0–3) 80 2 (2–2)

November 2006 100 4 (2–7) 100 2 (2–3)

December 2006 100 2 (2–2) 100 6 (4–9)

The monthly number of hosts examined for ticks (n) is also indicated.

minimum incubation periods of the eggs were recorded.

The linear correlation coefficient (r) was used to detect

relationships between the weight of female ticks and the

number of eggs laid and pre-oviposition period, and

between weight of immature and pre-moult period.

Additionally, the deterministic coefficient (r2) for the

significant correlations (P < 0.01) was calculated.

Fig. 2. Seasonal distribution of larvae and nymphs of Amblyomma parvum on

Quilino, Cordoba Province, Argentina, from January 2005 to December 20

3. Results

A total of 829 female (all from cattle and goats), 819

nymphs and 1039 larvae (all from G. musteloides) of A.

parvum were collected. All larvae and 97.5% of nymphs

were attached on the ears of G. musteloides, and more

than 95% of females collected were attached on the

head of cattle and goats, predominantly on ears and

periocular region, where inflammation occurs at the site

of tick attachment.

Divergence in the 16S rDNA sequences among

larvae, nymphs and females of ticks determined as A.

parvum was low, with a maximum difference of 1.1%

and a minimum difference of 0% (GenBank accession

numbers EU306136–EU306138 and EU543570–

EU543572), and the genetic divergence between A.

parvum specimens from Quilino and A. parvum

specimens from other Argentinean localities (GenBank

accession numbers EU306139–EU306156) was also

low, with a maximum difference of 1.1% and a

minimum difference of 0%. These findings support

standard morphological identifications.

Prevalence and M � 1Q–3Q of immature stages

and females of A. parvum collected per month are

shown in Tables 1 and 2, respectively. Analysis of the

monthly distribution of A. parvum demonstrated

distinct peaks of infestation for each of the three

stages (Fig. 2). Larvae were collected from March to

July with a peak of infestation in May in the two study

years; nymphs were found from June to September in

2005 and from June to October in 2006, with a peak of

infestation in August; females were found on cattle

and goats from October to April. Adult infestations

were concentrated principally in spring and summer in

the 2 years of samplings, with a peak in January and

February.

Galea musteloides and females ticks on cattle and goats (combined) in

06.

S. Nava et al. / Veterinary Parasitology 156 (2008) 270–276274

Table 3

Percentage of moulting success (MS), tick weights, and pre-moult periods of engorged larvae and nymphs of A. parvum collected in the field on

Galea musteloides

Photoperiod n MS Weight (mg) Pre-moult period (days)

Mean � S.D. (range) Mean* � S.D. (range)

LARVAE

12 L–12 D 23 95.6 0.36 � 0.05 (0.20–0.40) 14.53b � 0.86 (12–16)

14 L–10 D 23 100 0.39 � 0.07 (0.20–0.60) 12.17a � 0.58 (11–14)

10 L–14 D 23 95.6 0.34 � 0.08 (0.20–0.50) 16.40c � 0.72 (15–17)

NYMPHS

12 L–12 D 22 100 4.00 � 1.45 (1.90–7.00) 18.33a � 0.89 (16–18)

14 L–10 D 22 95.4 3.88 � 1.05 (1.20–6.60) 17.20a � 0.43 (15–19)

10 L–14 D 22 95.4 4.40 � 1.12 (2.20–5.60) 21.80b � 0.32 (21–22)

Ticks were maintained at 25 8C and 83–86% relative humidity, at three daily photoperiods regimens: 12 h light (L)–12 h dark (D), 14 h L–10 D, and

10 h L–14 h D. S.D.: standard deviation.

*ANOVA. Numbers not sharing superscripts are significantly different (P < 0.01).

The weights (mg) and pre-moult periods (days) of

engorged larvae and nymphs of A. parvum collected in

the field on G. musteloides and maintained in the

laboratory at three different photoperiods are shown in

Table 3, together with the results of the ANOVA. The

difference in the mean engorgement weight of the

nymphs moulting to females (6.2 mg � 1.8, n: 34) and to

males (2.1 mg � 0.1, n: 29) was statistically significant

(P < 0.01), but the difference in the pre-moult period of

the nymphs moulting to females (20.1 days � 2.0) and to

males (18 days � 2.0) was not significant (P > 0.01).

There was not significant correlation between the weights

of females, pre-oviposition period, and between weights

of immature stages and pre-moult periods. A significant

positive correlation was noted between the weight of

Table 4

Correlation (r) of biological parameters of immature stages and

females of Amblyomma parvum collected on the natural hosts and

maintained in the laboratory at 25 8C and 83–86% relative humidity, at

three daily photoperiods: 12 h light (L)–12 h dark (D), 14 h L–10 D,

and 10 h L–14 h D

n Photoperiod r r2

Larvae [x: weight (mg); Y: pre-moult period (days)]

23 12 h (L)–12 h (D) 0.36 NA

23 14 h (L)–10 h(D) 0.25 NA

23 10 h (L)–14 h(D) 0.29 NA

Nymphs [x: weight (mg); Y: pre-moult period (days)]

22 12 h (L)–12 h (D) 0.70 NA

22 14 h (L)–10 h(D) 0.41 NA

22 10 h (L)–14 h(D) 0.23 NA

Females [x: weight (mg); Y: pre-oviposition period (days)]

31 14 h (L)–10 h (D) 0.08 NA

Females [x: weight (mg); Y: number of eggs laid]

31 14 h (L)–10 h (D) 0.86 0.75

The deterministic coefficient (r2) for the significant correlations

(P < 0.01) is indicated. NA: not applicable.

females and number of eggs laid (Table 4). The average

weight of females was 206.1 mg � 23.6, and the mean

number of eggs laid was 1500.4� 298.2. The average of

pre-oviposition period was 6.5 days � 0.8, and the

minimum incubation period of eggs was 33.1 days � 1.2.

4. Discussion

A. parvum had one generation per year, characterized

by distinct sequential seasonal peaks of activity for each

parasitic stage. Larvae are active from late summer to

early winter with the peak in autumn, nymphs are found

from early winter to early spring with the peak in middle

winter, and the females are found during spring and

summer with the peak in early and middle summer

(Fig. 2). The seasonal activity of females appears to be

similar to those recorded in previous studies in

Argentina (Guglielmone et al., 1981, 1990b; Mangold

et al., 1994) and Brazil (Szabo et al., 2007). This

information on its seasonal distribution could be useful

in the design of control strategies. Even through the

development of the immature stages on wild rodents

prevents the implementation of conventional chemical

control, the application of acaricides on cattle and goats

between late spring and middle summer could be

appropriate to reduce infestation of adults. In conse-

quence, it would reduce the number of larvae and

nymphs originating from those adults.

Comparison between climatic data (Fig. 1) and tick

seasonality (Fig. 2) shows that the highest infestations

of the immature stages of A. parvum on G. musteloides

were in months with lower temperatures and rainfall

(autumn and winter). Conversely, the period of highest

activity of adults coincide with the months with higher

temperatures and rainfall, so that the oviposition occurs

in the rainy season. This seasonal distribution is similar

S. Nava et al. / Veterinary Parasitology 156 (2008) 270–276 275

to the pattern reported for another Neotropical species,

Amblyomma cajennense (Mangold et al., 1987;

Guglielmone et al., 1990b; Labruna et al., 2002;

Oliveira et al., 2003).

The pre-moult and pre-oviposition periods and the

minimum incubation period of eggs were similar to the

results obtained in the laboratory by Guglielmone et al.

(1991) where ticks were fed on rabbits. In both studies,

the mean incubation period of eggs was the longest

development phase. The engorged ticks exposed at

different photoperiods in the laboratory show no

indication of morphogenetic diapause as defined by

Belozerov (1982). The pre-moult period of larvae and

nymphs showed statistically significant differences

among groups exposed to different light/dark regimens

(Table 3), but these results are probably of little

biological significance, because the maximum differ-

ences observed was 4.2 days for larvae and 4.6 days for

nymphs. As expected for ticks, nymphs moulting to

females were heavier than those moulting to males, and

there was a significant correlation between weight of

females and number of eggs laid.

In Argentina, the life cycle of A. parvum in nature

includes use of wild and domestic animals as hosts of

preimagos and adults, respectively, and the involvement

of G. musteloides as host of larvae and nymphs in the

life cycle of A. parvum also occur in the natural cycle of

Amblyomma tigrinum (Aguirre et al., 2005; Nava et al.,

2006b), a tick species whose distribution is sympatric

with A. parvum in several regions of South America.

Thus, the role of Caviidae rodents as hosts of immature

stages for other Amblyomma species from South

America should be evaluated.

Acknowledgements

We acknowledge to O. Warnke for help in the field

work, and INTA, Fundacion ArgenINTA, Asociacion

Cooperadora INTA Rafaela and CONICET for their

financial assistance.

References

Aguirre, D.H., Mangold, A.J., Cafrune, M.M., Guglielmone, A.A.,

2005. Amblyomma tigrinum (Acari: Ixodidae): new data on hosts

and biology of immature stages and on DNA composition. Vet.

Parasitol. 134, 267–272.

Belozerov, V.N., 1982. Diapause and biological rhythms in ticks. In:

Obenchain, F.D., Galun, R. (Eds.), Physiology of Ticks. Pergamon

Press, Oxford, UK, pp. 469–500.

Cabrera, A.L., 1994. Enciclopedia Argentina de Agricultura y Jardi-

nerıa. Fascıculo 1. Regiones fitogeograficas argentinas. Tomo II.

Editorial ACME, Buenos Aires, Argentina, 85 pp.

Dunn, L.H., 1923. The ticks of Panama, their hosts, and the disease

they transmit. Am. J. Trop. Med. Hyg. 3, 41–104.

Floch, H., Fauran, P., 1958. Ixodides de la Guyane et des Antilles

Francaises. Arch. Inst. Pasteur Guyane 446, 1–94.

Guglielmone, A.A., Vinabal, A.E., 1994. Claves morfologicas dico-

tomicas e informacion ecologica para la identificacion de garra-

patas del genero Amblyomma Koch, 1844 de la Argentina. Rev.

Inv. Agropec. 25, 39–67.

Guglielmone, A.A., Nava, S., 2006. Las garrapatas argentinas del

genero Amblyomma (Acari: Ixodidae): distribucion y hospeda-

dores. Rev. Inv. Agropec. 35, 135–155.

Guglielmone, A.A., Hadani, A., Mangolg, A.J., De Haan, L., Bermu-

dez, A., 1981. Garrapatas (Ixodoidea-Ixodidae) del Ganado

bovino en la provincia de Salta: especies y carga en 5 zonas

ecologicas. Rev. Med. Vet. 62, 194–205.

Guglielmone, A.A., Mangold, A.J., Keirans, J.E., 1990a. Redescrip-

tion of the male and female of Amblyomma parvum Aragao, 1908,

and description of the nymph and larva, and description of all

stages of Amblyomma pseudoparvum sp.n. (Acari: Ixodida: Ixo-

didae). Acarologia 31, 144–159.

Guglielmone, A.A., Mangold, A.J., Aguirre, D.H., Gaido, A.B.,

1990b. Ecological aspects of four species of ticks found on cattle,

in Salta, Northwest Argentina. Vet. Parasitol. 35, 93–101.

Guglielmone, A.A., Mangold, A.J., Garcia, M.D., 1991. The life cycle

of Amblyomma parvum Aragao, 1908 (Acari: Ixodidae) under

laboratory conditions. Exp. Appl. Acarol. 13, 129–136.

Guglielmone, A.A., Estrada Pena, A., Keirans, J.E., Robbins, R.G.,

2003. Ticks (Acari: Ixodida) of the Neotropical Zoogeographic

Region. International Consortium on Ticks and Tick-Borne Dis-

eases (ICTTD-2) Atalanta, Houten, The Netherlands, 173 pp.

Hall, T.A., 1999. BioEdit: a user friendly biological sequence align-

ment editor and analysis program for Windows 95/98/NT. Nucl.

Acids Symp. Ser. 41, 95–98.

Ivancovich, J.C., Luciani, C.A., 1992. Las garrapatas de Argentina.

Monografıa de la Asociacion Argentina de Parasitologıa Veter-

inaria, 95 pp.

Jones, E.K., Clifford, C.M., Keirans, J.E., Kohls, G.M., 1972. The

ticks of Venezuela (Acarina: Ixodoidea) with a key to the species

of Amblyomma in the Western Hemisphere. Brigham Young Univ.

Biol. Ser. Sci. Bull. Biol. Ser. 17, 1–40.

Labruna, M.B., Kasai, N., Ferreira, F., Faccini, J.L.H., Gennari, S.M.,

2002. Seasonal dynamics of ticks (Acari: Ixodidae) on horses in

the state of Sao Paulo, Brazil. Vet. Parasitol. 105, 65–77.

Mangold, A.J., Bermudez, A.C., Kuhne, G.I., Guglielmone, A.A.,

1987. Garrapatas (Ixodoidea-Ixodidae et Argasidae) del ganado

bovino en Santiago del Estero. II. Especies y carga en el noroeste y

sudoeste de la provincia. Rev. Med. Vet. 68, 142–146.

Mangold, A.J., Aguirre, D.H., Gaido, A.B., Guglielmone, A.A.,

1994. Seasonal variation of ticks (Ixodidade) in Bos taurus x

Bos indicus cattle under rotational grazing in forested and

deforested habitats in northwestern Argentina. Vet. Parasitol.

54, 289–395.

Mangold, A.J., Bargues, M.D., Mas-Coma, S., 1998a. 18S rRNA gene

sequence and phylogenetic relationships of European hard-tick

species (Acari: Ixodidae). Parasitol. Res. 84, 31–37.

Mangold, A.J., Bargues, M.D., Mas-Coma, S., 1998b. Mitochondrial

16S rRNA sequences and phylogenetic relationships of Rhipice-

phalus and other tick genera among Metastriata (Acari: Ixodidae).

Parasitol. Res. 84, 478–484.

Nava, S., Mangold, A.J., Guglielmone, A.A., 2006a. The natural hosts

for larvae and nymphs of Amblyomma neumanni and Amblyomma

parvum (Acari: Ixodidae). Exp. Appl. Acarol. 40, 123–131.

S. Nava et al. / Veterinary Parasitology 156 (2008) 270–276276

Nava, S., Mangold, A.J., Guglielmone, A.A., 2006b. The natural hosts

of larvae and nymphs of Amblyomma tigrinum Koch, 1844 (Acari:

Ixodidae). Vet. Parasitol. 140, 124–132.

Nava, S., Szabo, M.P.J., Mangold, A.J., Guglielmone, A.A., 2008.

Distribution, hosts. 16rDNA sequences and phylogenetic position

of the Neotropical tick Amblyomma parvum (Acari: Ixodidae).

Ann. Trop. Med. Parasitol. 102, 409–425.

Oliveira, P.R., Borges, L.M.F., Leite, R.C., Freitas, C.M.V., 2003.

Seasonal dynamics of the Cayenne tick, Amblyomma cajennense

on horses in Brazil. Med. Vet. Entomol. 17, 412–416.

Pacheco, R.C., Moraes-Filho, J., Nava, S., Brandao, P.E., Richtzen-

hain, L.J., Labruna, M.B., 2007. Detection of a novel spotted fever

group rickettsia in Amblyomma parvum ticks (Acari: Ixodidae)

from Argentina. Exp. Appl. Acarol. 43, 63–71.

Serra Freire, N.M., Amorim, M., Gazeta, G.S., Guerim, L., Desiderio,

M.H.G., 1996. Ixodofauna de cervıdeos no Brasil. Rev. Bras.

Cienc. Vet. 3, 51–54.

Szabo, M.P.J., Olegario, M.M.M., Santos, A.L.Q., 2007. Tick fauna

from two locations in the Brazilian savannah. Exp. Appl. Acarol.

43, 73–84.

Tamura, K., Dudley, J., Nei, M., Kumar, S., 2007. MEGA4: molecular

evolutionary genetics analysis (MEGA) software version 4.0. Mol.

Biol. Evol. 24, 1596–1599.

Thompson, J.D., Higgins, D., Gibson, T.J., 1994. CLUSTAL W:

improving the sensitivity of progressive multiple sequence

alignment through sequence weighting, position-specific gap

penalities and weight matrix choice. Nucleic Acids Res. 22,

4673–4680.