Acta Tropica 140 (2014) 124–129

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Acta Tropica

jo urnal homepage: www.elsevier.com/locate/actatropica

Biological cycle and preliminary data on vectorial competence of

Triatoma boliviana in laboratory conditions

a,1 a a,b,∗

Pamela Durán , Edda Sinani˜ , Stéphanie Depickère

Laboratorio Entomología Médica, INLASA, Rafael Zubieta No. 1889, Miraﬂores, La Paz, Bolivia

Institut de Recherche pour le Développement (IRD), c/o Embajada Francia, CP 9214 La Paz, Bolivia

a r a

t i b s

c t

l e i n f o r a c t

Article history: With more than 140 potential vectors of Chagas disease, it is important to better know the biology

Received 22 April 2014

and especially the vectorial capacity of the triatomine species which live in the surroundings of human

Received in revised form 4 August 2014

dwellings. In Bolivia where 17 triatomine species are reported, the principal vector is Triatoma infestans.

Accepted 11 August 2014

In some valleys of the department of La Paz where T. infestans is not present, a new species (Triatoma

Available online 20 August 2014

boliviana) was described in 2007. This species lives in a sylvatic environment not far away from the

dwellings, and occasionally some individuals are found inside the houses. This study was carried out to

Keywords:

describe the biological cycle of T. boliviana and to determine its vectorial competence. The development

Chagas disease

of a cohort of 95 nymphs of ﬁrst instar (N1) was followed through nymphal instars and adult stage until

Vectorial competence ◦

death in laboratory (22 C). They were fed twice a week on an immobilized mouse. The median egg-to-

Triatoma boliviana

Life cycle adult development time was 8.4 months. The mortality by nymphal instar was lower than 7% except for

Laboratory rearing N1 (67%) and N5 (18%). All nymph instars needed at least two feedings to molt (until six feedings for N5).

Defecation index The differentiation of a nymph into a female or a male could not be detected until the ﬁfth instar for which

the food intake was greater for a nymph developing into a female. Adults fed about once a week. The adult

life span was around 400 days. The fecundity was 4.2 eggs/female/week, with a hatching rate of 50% and

a hatching time of 39 days. In the same conditions, T. infestans showed a similar fecundity but a greater

◦

hatching rate and hatching time. A trial for rearing the adults at a higher temperature (26 C) showed

a drastic fall in the fecundity and in the hatching rate. The vectorial competence was analyzed for ﬁfth

instars and adults by three parameters: the ability to feed on human beings, the capacity to be infected

by T. cruzi and the postfeeding defecation delay. Results showed a relatively high vectorial competence:

(1) insects fed easily on the tested human being; (2) 100% of the specimens became infected by T. cruzi

just by one infected meal; and (3) although the adults defecated after a median postfeeding delay greater

than that of T. infestans, results on N5 suggest that they could be as good vectors as T. infestans males.

1. Introduction currently recognized species of Triatominae have been shown to be

naturally or experimentally infected with T. cruzi, and all are sus-

Chagas disease is caused by the parasite Trypanosoma cruzi pected to have this capacity. Nevertheless, only 5% of the triatomine

which is mainly transmitted to humans by blood-sucking tri- species is considered to have a great epidemiological importance

atomine bugs (Hemiptera: Reduviidae). Over half of the 141 in the Chagas disease transmission (Telleria and Tibayrenc, 2010).

This can be explained by the vectorial competence which varies

according to the bug species. The heamatophagous diet and the

∗ capacity to be infected by T. cruzi are not sufﬁcient to determine a

Corresponding author at: Institut de Recherche pour le Développement (IRD),

species as a vector; other conditions mainly related to the anthro-

IRD c/o Embajada Francia, La Paz, Plurinational State of Bolivia.

Tel.: +591 2 222 52 80. pophyly degree and the defecation velocity are required (Dujardin

E-mail addresses: [email protected] (P. Durán), et al., 2002; Klotz et al., 2009; Telleria and Tibayrenc, 2010).

[email protected] (E. Sinani),˜ [email protected] (S. Depickère).

In the Southern Cone of South America, the main vector

Present address: Instituto de Investigación en Salud y Desarrollo (IINSAD),

Triatoma infestans is a domiciled species. In Bolivia which is a high-

Calle Claudio Sanjinez, Ediﬁcio IBBA, Complejo Hospitalario de Miraﬂores, La

endemic country for Chagas disease, this vector is present across

Paz, Bolivia—Cátedra de Parasitología, Departamento de Parasitología, Facultad de

Medicina, Universidad Mayor de San Andrés, Av. Saavedra 2246, La Paz, Bolivia. 60% of the territory (Petherick, 2010). Sixteen other species of

http://dx.doi.org/10.1016/j.actatropica.2014.08.014

P. Durán et al. / Acta Tropica 140 (2014) 124–129 125

Triatominae have been described until now in this country feeding/weight just after the last molting. The feeding speed was

(Martínez et al., 2007). Some of them have a role in the transmis- measured as the amount of ingested blood (mg) per minute. To

sion of Chagas disease to human population (Rhodnius stali: Justi determine the frequency of feeding, the percentage of positive feed-

et al., 2010; Triatoma sordida: Noireau et al., 1997). Some other ing was calculated. The latter is deﬁned as the number of effective

species do not have this vector role although they live near human feeding divided by the number of possibilities to feed and expressed

beings (Eratyrus mucronatus: Depickère et al., 2012; Panstrongylus in percentage. Finally the defecation time (deﬁned as the time

rufotuberculatus: Depickère et al., 2011). between the end of feeding and the defecation act) was determined.

Triatoma boliviana is a new species of Triatominae described in This time was equal to 0 if the bug defecated during feeding. Two

2007 in Bolivia (Martínez et al., 2007). This bug was collected in defecation indexes (ADIt and PDIt), based on the defecation index

narrow valleys of the Department of La Paz, Provinces of Munecas˜ (DI) calculated by Zeledón et al. (1977), were deﬁned in order to

and Larecaja (2100–2600 m asl). It was captured in a sylvatic habi- compare the stages and species:

tat in the surroundings of the dwellings, more precisely in piles t

of stones delimiting the ﬁelds in this region. From time to time ADI = t=0 × D,¯

t N

some specimens are also collected inside or around the houses.

Until now, there is no evidence of Chagas disease transmission to

human population in the region. Nevertheless, it is really important Nt t=0

PDIt = × D,¯

to well understand the biological cycle of the Triatominae species N

− Nno

living near the human dwellings. Therefore, the objectives of this

where Nt is the number of bugs which defecated at time t; N is the

study were to determine the life-cycle of T. boliviana under labo-

total number of individuals; Nno is the number of insects which

ratory conditions and to analyze some parameters of its vectorial

have not defecated during the observation time; and D¯ is the aver-

competence as regards the transmission of T. cruzi.

age number of defecation per insect which have defecated during

the observation time.

2. Material and methods

Data on feeding and defecation behavior were compared with

those obtained on T. infestans (6 pairs of adults) using the same

The colony of T. boliviana was collected in 2007 in the Province of

protocol and conditions of rearing. In view of the usual condition

Munecas,˜ La Paz, Bolivia. From four communities visited during the ◦

of rearing of T. infestans in our laboratory (26 ± 2 C, 55 ± 20% RH,

ﬁeld work, 917 T. boliviana specimens were found in three villages.

12:12 dark:light regime), 6 pairs of adults of T. infestans and 6

Eight bugs were captured in the dwellings (one in the intradomi-

pairs of adults of T. boliviana were also reared in these conditions

cile and seven in the peridomicile at 2 m of the house). The rest

to observe the inﬂuence of the temperature on the fecundity and

of the bugs were captured in piles of stones and stone walls (0.3

mortality.

to 2 m high) delimiting the ﬁelds around the dwellings, generally

Finally, the capacities of T. boliviana to feed on human being and

20–300 m distant from the houses (Martínez et al., 2007). Insects

to be infected by T. cruzi were investigated in order to complete the

were reared in laboratory in La Paz under similar conditions to

◦ data about the vectorial competence of this species:

those of their natural environment: 22 ± 2 C; 60 ± 10% RH; 12:12

light:dark regime in a laboratory oven (Firlabo Meditest 600).

- 10 N5 and 10 adults (5 females and 5 males) were starved for

30 days and then placed in two different small plastic containers

2.1. Life-cycle

covered on the top with a piece of mosquito net. These contain-

ers were placed directly in contact with the human being skin of

The study began with 95 nymphs of the ﬁrst instar (N1) from

a consenting person of our team, allowing the bite of the bugs.

the ﬁrst generation (F1). The development of this cohort was fol-

The insects’ weight before and after feeding was recorded and

lowed through nymphal instars and adult stage until death. Insects

the weight increase was expressed as the ratio weight after feed-

were weighed just after they hatched. They were reared individu-

ing/weight before feeding. In order to compare the results, 12 N5

ally and fed on immobilized mice for 2 h twice a week. The mouse

and 8 adults (7 females and 1 male) of T. infestans were put in the

was placed inside a thin wire mesh tube which did not wound it in

same conditions of starvation and of feeding on human being.

order to avoid its movements and to let the bug fed on it (similar

- 5 N5 and 7 adults (2 females and 5 males) were fed just once on a

setup to that used in Klotz et al. (2009)). A mouse was used to feed

mouse previously infected with T. cruzi. Using a microscope, the

only one insect every two weeks. Two hours has been observed as

feces of these bugs were observed to look for parasites.

an adequate duration to have a feeding ad libitum of the bugs. The

number of positive feedings, the time of molting and the mortal-

ity rate per instar were measured. Adults were reared in pairs to Results are presented in terms of median (quartile 1 and 3) due

observe the number of eggs laid by females (a male was added just to the small number of insects. Non-parametric tests were used for

after the female molting). Eggs were separated, incubated in the the comparisons: Mann–Whitney U test was used to compare two

same conditions, and observed twice a week up to hatch. Hatching independent samples; Kruskall–Wallis test was performed to com-

time and percentage of hatching were recorded. The fecundity was pare more than two independent samples. All tests were performed

expressed as the eggs number laid by a female during a week. with R (R Development Core Team, 2011).

2.2. Vectorial competence 3. Results

Adults and ﬁfth instar (N5) were weighed with a precision bal- 3.1. Life-cycle

ance (Precisa Instrument Switzerland, XT220A) just before and

after each feeding to determine the amount of ingested blood. The nymph development up to adult stage took a median of 216

Feeding and defecation behavior were observed. The time of the days (205, 230) with a minimum of 192 days and a maximum of

beginning of feeding is deﬁned as the time between the start of 259 days. The mortality rate remained below 3% except for the ﬁrst

◦ ◦

the experiment and the ﬁrst bite of the bug on the mouse. The instar (67%) and the ﬁfth instar (18%) (Table 1). Nymphs of 1 , 2 and

◦ ◦

weight increase was expressed in terms of (i) the ratio: weight 3 instars (N1, N2 and N3) needed two feedings to molt whereas 4

◦

after feeding/weight before feeding; (2) the ratio: weight after and 5 instars needed a greater number of feedings (between three

126 P. Durán et al. / Acta Tropica 140 (2014) 124–129

Table 1

Life cycle of nymphs: mortality rates (number of nymphs), total accumulative mortality, median hatching time and median number of feeding for each instar (quartile 1,

quartile 3). F and M: nymphs which became females and males, respectively (n: number of observed nymphs). Statistical comparison between nymphs becoming males or

females by Mann–Whitney U test; signiﬁcance of the test given by p-value (NS: non signiﬁcant).

Instar Mortality rate Total accumulative Median hatching time (days) Median feeding number

mortality (%)

F (n = 15) M (n = 8) p-Value F (n = 15) M (n = 8) p-Value

N1 67% (95 N1) 67 35.0 (34.0, 39.5) 39.5 (34.0, 41.3) 0.55, NS 2.0 (2.0, 2.0) 2.0 (2.0, 3.0) 0.27, NS

N2 7% (31 N2) 69 30.0 (28.0, 33.5) 28.0 (25.0, 28.3) 0.08, NS 2.0 (1.0, 2.0) 2.0 (1.8, 2.3) 0.51, NS

N3 0% (29 N3) 69 35.0 (30.5, 35.0) 32.0 (28.5, 32.5) 0.15, NS 2.0 (2.0, 3.0) 2.0 (1.8, 2.0) 0.06, NS

N4 3% (29 N4) 71 42.0 (39.0, 45.5) 44.5 (38.8, 46.0) 0.73, NS 3.0 (3.0, 4.0) 4.0 (3.0, 4.0) 0.43, NS

N5 18% (28 N5) 76 69.0 (62.0, 80.0) 78.0 (66.5, 84.0) 0.27, NS 6.0 (5.0, 7.0) 6.0 (5.8, 7.5) 0.55, NS

and six, Table 1). Molting took place after 30–40 days except for the 3.2. Vectorial competence

◦

5 instar for which the ecdysis occurred after a longer period (75

days, Table 1). The weight increase between two nymphal instars In the presence of the mouse, females, males and N5 began

diminished according to the succession of instars, being the greatest to feed after a median time interval of 10–17 min for T. boliviana

for N1 and the smallest for N5 (Table 2). and 23–29 min for T. infestans (Table 4). They took blood in a suc-

At emergence, the adults weighed around 200 times the weight cession of feeding periods interrupted by stops whose time was

of a N1 (Table 2). A difference between sexes was pointed out: variable; the number of feeding periods was not different between

a female was signiﬁcantly heavier than a male at emergence, as species and instars (Kruskal–Wallis test: p = 0.06). Post-hoc analysis

showed by the signiﬁcance of the comparisons of the weight ratio showed that males of T. boliviana began to eat statistically quicker

between sexes (weight ratio expressed in terms of adult/N1 as than males and females of T. infestans. After each feeding, the weight

well as in terms of adult/N5, Table 2). The differentiation of a increase (in terms of weight ratio after/before feeding) was not dif-

nymph into a female or a male could not be detected until the ﬁfth ferent between the observed groups (Table 4: Kruskal–Wallis test:

instar. Whereas after the N5 ecdysis all the nymphs had a similar p < 0.005 but post-hoc analysis did not show any statistical differ-

weight, the N5 developing into a female fed a greater quantity of ence between groups at a threshold of 0.05). When the weight

blood than that developing into a male (comparison of the greatest increase was expressed in terms of weight ratio after feeding/at

weight between N5 becoming males and N5 becoming a female: ecdysis, differences appeared (Table 4): post-hoc analysis showed

Mann–Whitney U test: U = 6, p < 0.001). that (1) the weight increase was greater for females than for males

The life span was signiﬁcantly greater for females than for males (signiﬁcant result for T. boliviana, but only a tendency for T. infes-

(Table 3). Males as females chose to feed once a week (Table 3: tans); and (2) ﬁfth instar of T. boliviana had also an important weight

positive feedings of ∼50%). Two females out of 15 never laid eggs increase, not statistically different from the T. infestans adult’s one.

(these two females were put in contact with different males in order The feeding speed was signiﬁcantly greater in T. infestans than in T.

to ensure that the lack of eggs was not a problem related to the boliviana (Table 4). After feeding, less T. boliviana individuals defe-

male). The ﬁrst egg laying occurred after a median lapse time of cated in the observation time compared with T. infestans individuals

35 days (31, 39), with a minimum of 28 days and a maximum of (13% of 67 males, 37% of 134 females, 42% of 31 N5 of T. boliviana;

94 days after the emergence of the female. The median fecundity 63% of 27 males and 68% of 41 females of T. infestans). Moreover,

was 4.2 (3.3, 4.6) eggs/female/week. The median hatching rate was in contrast to T. boliviana, T. infestans specimens often defecated

50% (22–70%); and the median hatching time was equal to 39 days more than once during the observation time. Fig. 1 shows this dif-

(38, 42). In the same condition, T. infestans showed a similar fecun- ference between species: the ADI is greater for T. infestans than for

dity. Nevertheless, the hatching time and the hatching rate were T. boliviana; males having a lower index than females; and N5 index

signiﬁcantly higher in T. infestans (Table 3). being greater than that of T. boliviana females. When the defecation

◦

In laboratory conditions of 26 C, adults of T. boliviana lived occurred, post-hoc analysis showed that adults of T. infestans defe-

signiﬁcantly less time (Mann–Whitney U test: females: U = 76, cated earlier than adults of T. boliviana but not than N5 (Table 4).

◦ ◦ ◦ ◦

n26 C = 7, n22 C = 15, p = 0.002; males: U = 48, n26 C = 6, n22 C = 8, The defecation during the feeding act was never observed in T. boli-

p < 0.001). Moreover, the fecundity was very low (only two females viana (although some individuals defecated between two feeding

out of six laid eggs: two and eight eggs) and the hatching rate was periods); in T. infestans, this happened three times (out of 28) for

◦

null in these conditions. In comparison, the condition of 26 C for females and once (out of 17) for males. The PDI defecation index

T. infestans did alter neither the fecundity (Mann Whitney U test: showed that females of T. infestans defecated the fastest after feed-

U = 4, p = 0.26) nor the hatching success (Mann–Whitney U test: ing; at 10 min the difference between females of T. boliviana and

U = 6.5, p = 0.54) but accelerated the hatching (25 days instead of males of T. infestans was very small; and N5 had even a higher PDI

42 days: Mann–Whitney U test: U = 61450, p < 0.001). than males of T. infestans (Fig. 1).

Table 2

Median weight increase at ecdysis for each instar: (1) according to the weight of the anterior instar at ecdysis (ratio weight of instar Ni/weight of instar Ni−1); (2) according

to the weight of the instar N1 after hatching (ratio weight of Ni at ecdysis/weight of the same nymph after egg hatching). F and M: nymphs which became females and males,

respectively (n: number of observed nymphs). Statistical comparison between nymphs becoming males or females by Mann–Whitney U test; signiﬁcance of the test given

by p-value (NS: non signiﬁcant).

Ni Weight ratio (Ni weight/Ni−1 weight) Weight ratio (Ni weight/N1 weight)

F (n = 15) M (n = 8) p-Value F (n = 15) M (n = 8) p-Value

N2 4.4 (3.8, 4.8) 5.1 (4.7, 5.6) 0.07, NS 4.4 (3.8, 4.8) 5.1 (4.7, 5.6) 0.07, NS

N3 3.5 (3.1, 4.2) 3.6 (3.4, 4.1) 0.73, NS 15.4 (13.4, 18.1) 18.5 (16.9, 19.6) 0.04

N4 3.5 (3.0, 3.8) 2.8 (2.4, 3. 0) 0.02 53.2 (46.7, 55.8) 50.5 (44.3, 54.4) 0.55, NS

N5 2.1 (2.0, 2.3) 2.4 (2.1, 2.5) 0.19, NS 113.1 (106.7, 121.4) 118.1 (112.4, 123.1) 0.39, NS

Adult 2.0 (1.9, 2.1) 1.6 (1.4, 1.6) <0.001 220.3 (204.2, 243.9) 187.7 (163.4, 200.3) 0.01

P. Durán et al. / Acta Tropica 140 (2014) 124–129 127

Table 3

◦

Life cycle of adults of T. boliviana and T. infestans reared at 22 C. F: females. M: males. Life span, % of positive feedings, fecundity of females, hatching time and % of hatching

are given in term of median (quartile 1 and 3) (n: number of observed nymphs). Intraspeciﬁc comparison between males and females in each species; and interspeciﬁc

comparison by Mann-Whitney U-test; signiﬁcance of the test given by p-value (NS: non signiﬁcant).

T. boliviana adults T. infestans adults p-Value

Life span (days) F 450 (397, 506) (n = 15) 378 (250, 442) (n = 6) 0.11, NS

M 357 (341, 383) (n = 8) 274 (190, 340) (n = 6) 0.14, NS

p-Value <0.01 0.59, NS

% positive feeding F 53 (46, 58) (n = 15) 43 (33, 54) (n = 6) 0.30, NS

M 49 (45, 54) (n = 8) 34 (26, 41) (n = 6) <0.01

p-Value 0.63, NS 0.24, NS

Eggs #/female/week 4.2 (3.3, 4.6) (n = 13) 4.2 (3.6, 5.0) (n = 6) 0.64, NS

Hatching time (days) 39.0 (38.0, 42.0) (n = 732) 42.0 (39.0, 43.0) (n = 690) <0.001

Hatching rate/female 50 (22, 70) 87 (76, 89) <0.005

Experiment about human being as a source of blood showed mortality of eggs and nymphs (Guarneri et al., 2002; Roca and

that 70% of the N5 and 70% of the adults of T. boliviana (all the Lazzari, 1994). Indeed, an increase of the relative humidity in the

females and two males) fed on the tested human being. The num- rearing conditions of eggs and N1 seems to improve the success

ber of individuals of T. infestans which decided to feed in the of hatching and molting in the colony. Another reason of the low

same conditions was a little bit higher: 92% of the N5 and 88% of survival rate of N1 might be the feeding source. The choice to use

the adults (all the females). In both species, the weight increase mice as a blood source for the colony was determined by the fact

of insects was higher than this obtained in the life-cycle exper- that T. boliviana refused to feed on hens. Moreover, rodents seem

iment conditions (Median and quartiles 1 and 3 for T. boliviana: to be the most likely feeding source of this species in the ﬁeld.

N5: 1.65 (1.33–3.06), adults: 1.47 (1.30–1.55); for T. infestans: N5: Nevertheless, it is possible that mice are not the best source of

5.01 (3.82–5.33), adults: 1.69 (1.37–2.09); Mann–Whitney U test feeding for N1. A hypothesis is that they could feed on arthropods

for adults of T. boliviana between feeding on human being (N = 7) in the wild since a lot of arthropods were also encountered in the

and feeding on mouse (N = 672): U = 621, p < 0.001; for adults of T. piles of rocks in the ﬁeld (especially from Blattodea and Coleoptera

infestans between feeding on human being (N = 7) and on mouse Orders). This type of diet was already described for some Tri-

(N = 367): U = 586, p = 0.014). atominae species (haemolymphagy, see i.e. Sandoval et al., 2010).

Experiments about infection of T. boliviana by T. cruzi by feed- It should be very interesting to perform a study of the ingested

ing on infected mouse showed that 100% of T. boliviana individuals blood origin and knowing better the hosts naturally used by this

◦

(adults and N5) had T. cruzi parasites in their feces. species. A warmer condition (26 C), at least for adults, seemed not

to be suitable to rear this species because of the drastic fall of the

4. Discussion fecundity and egg hatching.

The median life span of each instar was about 1–1.5 month (N1

◦

The condition of rearing at 22 C seems to be adequate for this to N4), and up to 2.5 months for N5, leading to a median egg-to-

species as shown by the low mortality rate, except for N1 and N5 adult development time of 8.4 months. This time is similar to the

◦

instars. The ﬁrst instar seems to be very frail: more than 90% of the development time of Triatoma recurva reared on rabbits at 25 C and

death happened before a successful feeding whereas the possibility 50% RH in Mexico (Martínez-Ibarra et al., 2012), equal or shorter

of feeding was offered. The N5 death occurred more frequently than other Triatominae (T. protracta, T. lecticularia and T. gerstaeck-

◦

during molting. This pattern of mortality for nymphal instars eri) reared at 27 C and 30% RH in Mexico (Martínez-Ibarra et al.,

was already reported in other species (e.g. in Triatoma rubida and 2007) but much longer than other Triatoma species (e.g. Bautista

Triatoma recurva: Martínez-Ibarra et al., 2012; Triatoma mexicana: et al., 2001; Martínez-Ibarra et al., 2012) or Rhodnius species (e.g.

Martínez-Ibarra et al., 2008). The egg hatching was also low (50%) Aldana et al., 2005; Arévalo et al., 2007). All the instars required

compared with the value found in T. infestans in the same condi- at least two meals to molt (4 and 6 meals for N4 and N5). The dif-

tion (88%). Two hypotheses could explain these results. First, it is ference between male and female appeared from the N5 instar:

known that humidity has an inﬂuence on the development and the reared in the same conditions, the food intake of the N5 is higher

Fig. 1. Defecation indexes (ADI and DPI) according to the observation time, calculated for T. boliviana (: Males, : Females, : N5) and T. infestans (: Males; ᭹: Females).

Number of observed defecations: 49, 9 and 12, respectively, for females, males and N5 of T. boliviana; and 28 and 17, respectively, for females and males of T. infestans. Time

0 represents the end of the feeding time.

128 P. Durán et al. / Acta Tropica 140 (2014) 124–129

for a nymph developing into a female than into a male. This food

given

reserve brought from the last nymph state should be determinant -Value <0.001 <0.005 <0.001 <0.001 <0.005

KW p

of the ﬁrst oviposition as shown in T. infestans (Asin and Crocco de test

Ayerbe, 1989). the

of The life span of adults of T. boliviana was greater for females than

for males; and similar to the life span of T. infestans. The fecundity 138 146 27

of females (egg production) was also similar in both species. The

= = =

n n n

hatching time was signiﬁcantly lower for eggs of T. boliviana than 27 =

signiﬁcance ◦ = n

for eggs of T. infestans under the condition of 22 C. n

test; The adults of T. boliviana have a feeding behavior similar to the

adults of T. infestans: they ate once a week when the choice is given. (1.07–1.27) (1.44–2.23) (1.52–6.97)

(0.3–6.1) (15–48)

Both species began to feed 10–30 min after the mouse was pre-

Males 29 1.14 1.94 2.90 1.8

sented. The weight increase after each feeding was not different

between sexes and similar in both species. Nevertheless, some sta- Kruskal–Wallis

tistical interspeciﬁc differences appeared: adults of T. boliviana (1)

fed slowly; (2) had a lower weight increase after each feeding when 223 40 221

= =

the insect weight is compared to its weight at emergence; (3) defe- 28

n n n

stages =

n cated less often during the observation time and, when defecation

and

was observed, it occurred with a higher postfeeding delay.

The hypothesis presented by Dias (1956) and, later on, sup- (1.07–1.28) (1.95–2.94)

(2.27–6.46)

species ported by Zeledón et al. (1977), points out that triatomines that (0.1–14.4)

(13–48)

infestans

defecate before 10 min postfeeding are potentially effective trans-

T. Females 23 1.13 2.49 4.10 1.3

mitters of T. cruzi. The defecation index was introduced by Zeledón between

et al. (1977), and we extended the concept, deﬁning ADI and DPI

which can be very useful to compare species and conditions. DPI 45 45 33

showed that the defecation of females and N5 of T. boliviana in the = = =

n n n

experimental conditions were not very different from the male pat- 33

n Comparison

tern of T. infestans. Nevertheless, API showed a difference between n

species due to the greater number of T. boliviana individuals which

did not defecate during the experiment. The ﬁfth instar might (1.11–1.38) (1.44–2.25) (0.24–0.73)

(3.4–17.8) (11–29)

be potentially effective vectors of T. cruzi. It seems here that the N5 16 1.22 1.85 0.46 4.9 observations).

amount of food is important to produce a rapid defecation after of

feeding because the weight increase of N5 was greater than that of

the adults and similar to the weight increase of T. infestans adults.

number

The relation between defecation time and food amount was previ-

: 165 67 167

n = = = 9

(

ously observed in different species such as T. infestans (Trumper and

n n n =

Gorla, 1991), T. sordida (Crocco and Catalá, 1996) or T. patagonica 74

(Nattero et al., 2002). In various triatomine species, the youngest n

instars seem to have a higher vectorial capacity (e.g. Meccus pal- parameter

(1.07–1.27) (6.7-42.5)

(0.86–1.01) (0.38–1.25)

lidipennis: Martínez-Ibarra and Katthain-Duchateau, 1999; Meccus (4–24)

each

longipennis and M. picturatus: Martinez-Ibarra et al., 2003a,b; Tri- Males 10 1.15 0.93 0.72 37.1 for

atoma dimidiata: Martínez-Ibarra et al., 2001). Unfortunately, no

data are available about the youngest instar defecation pattern in given

is our study, but it is an issue to explore. Adults of T. boliviana seem not

to feed enough to produce defecation, maybe because of the oppor- 507 513 133

49 1, = = =

= n

n n tunity to feed ad libitum twice a week. It could be very interesting

158 to conduct another experiment with adults submitted to a starva-

n tion period with the aim of producing a higher amount of ingested

(quartile

blood. In these conditions, certainly closer to natural ones where (1.11–1.27) (0.96–1.13) (0.48–1.33) (5.9–22.1)

(7–36) bugs have to ﬁnd food, it could be observed a decrease of the defe-

boliviana

Median

T. Females 17 1.18 0.78 10.5 cation time, or a higher percentage of defecating insects. Finally

nothing is known about the usual behavioral biology between T.

boliviana and its hosts in the wild. Their principal source of blood infestans

T. might be rodents. A hypothesis is that insects usually stay not far

away from their host after feeding. The latter could explain the var- and

molt) 1.03

feeding

ious prolonged interruptions observed during the feeding act. An feeding)

experiment to study the move of the bugs after the blood meal after

boliviana could allow to deﬁne a minimum elapsed time in which the trans-

T. feeding/at

(min) mission can occur to the host (see e.g. T. rubrovaria: Almeida et al., (min)

of 2003). feed (after/before (after

time

(mg/min) Adults and N5 of T. boliviana feed easily on the tested human to

being; they can become infected by T. cruzi with just one infected

speed

begin increase increase

meal; and T. cruzi can complete its development cycle in the bug.

competence

defecation

Although from an experiment with only one tested human being, 4

-value.

p it is difﬁcult to conclude that T. boliviana is able to feed on any

Time Weight Weight Feeding First Table

Vectorial

by human being; these results suggest that if these bugs live in an

P. Durán et al. / Acta Tropica 140 (2014) 124–129 129

environment where T. cruzi circulates and where human beings Guarneri, A.A., Lazzari, C.R., Diotaiuti, L., Lorenzo, M.G., 2002. The effect of relative

humidity on the behaviour and development of Triatoma brasiliensis. Physiol.

live, these bugs could enter in the transmission cycle of Chagas

Entomol. 27, 142–147.

disease to the human population.

Justi, S.A., Noireau, F., Cortez, M.R., Monteiro, F.A., 2010. Infestation of peridomestic

In conclusion, T. boliviana has a well development in our condi- Attalea phalerata palms by Rhodnius stali, a vector of Trypanosoma cruzi in the

Alto Beni, Bolivia. Trop. Med. Int. Health 15, 727–732.

tions. Nevertheless, a study in-situ of the bugs should be realized

Klotz, S.A., Dorn, P.L., Klotz, J.H., Pinnas, J.L., Weirauch, C., Kurtz, J.R., Schmidt, J., 2009.

to know with more details the natural environmental conditions

Feeding behavior of triatomines from the southwestern United States: an update

where they live; and the hosts on which they feed. In the stud- on potential risk for transmission of Chagas disease. Acta Trop. 111, 114–118.

Martínez, E., Chávez, T., Sossa, D., Aranda, R., Vargas, B., Vidaurre, P., 2007. Triatoma

ied conditions, they need various feedings to molt, increasing their

boliviana sp. n. (Hemiptera: Reduviidae: Triatominae) from Sub Andean valleys

possibility to infect with T. cruzi. A good vector of Chagas disease

of La Paz—Bolivia, related to Triatoma nigromaculata Stål, 1859. Rev. Cuad. del

is characterized by (1) a capability to live in a domestic environ- Hosp. Clin. 52, 9–16.

ment, (2) a capability to feed on human beings, (3) the potentiality Martínez-Ibarra, J.A., Alejandre-Aguilar, R., Paredes-González, E., Martínez-Silva,

M.A., Solorio-Cibrián, M., Nogueda-Torres, B., Trujillo-Contreras, F., Novelo-

to be infected by T. cruzi, and (4) a rapid defecation after feeding.

López, M., 2007. Biology of three species of North American Triatominae

The comparison of the feeding/defecation patterns of T. boliviana

(Hemiptera: Reduviidae: Triatominae) fed on rabbits. Mem. Inst. Oswaldo Cruz

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in the same conditions, showed a relative high potential of T. boli-

cation, and development times of Meccus longipennis Usinger, 1939 (Hemiptera:

viana as vector of Chagas disease, particularly for the ﬁfth instar.

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Martínez-Ibarra, J.A., Katthain-Duchateau, G., 1999. Biology of Triatoma pallidipennis

the zone where T. boliviana is described. Nevertheless, the author-

Stal 1945 (Hemiptera: Reduviidae: Triatominae) under laboratory conditions.

ity must take into account these vectorial competence results and

Mem. Inst. Oswaldo Cruz 94, 837–839.

monitors continuously a possible domiciliary invasion process. Martínez-Ibarra, J.A., Miguel-Álvarez, A., Arredondo-Jiménez, J.I., Rodríguez-López,

M.H., 2001. Update on the biology of Triatoma dimidiata Latreille (Hemiptera:

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Martinez-Ibarra, J.A., Novelo Lopez, M., Hernandez Robles, M.R., Guillén, Y.G., 2003b.

Inﬂuence of the blood meal source on the biology of Meccus picturatus Usinger

We thank T. Chavez and G.M. Ramírez Ávila for their helpful

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comments on the manuscript. We thank F. Brenière and F. Lardeux

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for their logistical support. Martínez-Ibarra, J.A., Paredes-González, E., Licón-Trillo, A., Montanez-Valdez,˜ O.D.,

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