
 input data - occurrence data were accumulated from diverse sources , 
 including all known triatomine collection records from the literature for all of north 
 america ( pubmed using the search words  triatominae  and  mexico  and the scientific 
 names of each species known from mexico prior to 2014 ) , publication references from 
 reviews or publications not in pubmed prior to 2002 , grey literature and government 
 reports in mexico , entomological collections [ biology institute / national autonomous 
 university of mexico , national museum of american history / smithsonian institution , 
 global biodiversity information facility ( gbif.org ) ] and personal collections ( jmr ) . 

enms were developed for mexican species for which  10 unique collection data points 
 were available in north america . twenty species met this criterion , but triatoma 
 neotomae had 10 occurrence points divided between two distant regions , 
 producing unsatisfactory models , so this species was not included .
enms were calibrated using all occurrence points in north america because major portions 
 of the species distributions for the lecticularia and protracta complexes fall outside 
 mexican national boundaries ( peterson et al . 

a total of 2,580 occurrence points were available for 38 species and 
 subspecies : belminus ( 1 species ) , dipetalogaster ( 1 
 species ) , eratyrus ( 1 species ) , panstrongylus ( 1 
 species ) , paratriatoma ( 1 species ) and triatoma ( 26 
 species and 7 additional subspecies ) .
based on the range of known occurrences , species 
 were classified according to biogeographic region as neotropical ( 16 species ) , nearctic 
 ( 12 species + 7 subspecies ) or both ( 3 species ) , using regionalisation layers defined by 
 olson et al .
a total of 2,519 
 occurrence points corresponded to the 19 species for which enms were developed .
enms for 
 t. protracta and t. rubida included occurrences of 
 the type subspecies ( t. p. protracta and t. r. 
 rubida ) ; the three hg of t. dimidiata ( hg1 , hg2 and hg3 ) were 
 modelled separately ( table i ) . 

table imexican triatominae , their biogeographic region , occurrence points and 
 accuracy for ecological niche models ( enms ) of 19 speciesidspecies 
 complexspeciessubspeciesregionpointsbackgroundp1lecticularia 
 triatoma incrassata 
 -nearctic5 - -2 
 triatoma indictiva 
 -nearctic5 - -3 
 triatoma lecticularia 
 -nearctic309,230,4646.01 
 4protracta 
 triatoma barberi 
 -nearctic / neotropical36910,069,5673.91 
 5 
 triatoma neotomae 
 -nearctic10 - -6 
 triatoma nitida 
 -neotropical7 - -7 
 triatoma peninsularis 
 -nearctic109,230,4641.45 
 8 
 triatoma protracta 

 t. p. protracta 
 nearctic1779,230,4641.63 
 9 
 t. p. nahuatlae 
 10 
 t. p. woodi 
 11 
 t. p. zacatecensis 
 12 
 triatoma sinaloensis 
 -nearctic5 - -13rubida 
 triatoma rubida 

 t. r. cochimiensis 
 nearctic1219,283,9664.74 
 14 
 t. r. jaegeri 
 15 
 t. r. rubida 
 16 
 t. r. sonoriana 
 17 
 t. r. uhleri 
 18phyllosoma 
 triatoma bassolsae 
 -neotropical1 - -19 
 triatoma brailovskyi 
 -neotropical11652,6556.68 
 20 
 triatoma bolivari 

-neotropical4 - -21 
 triatoma gerstaeckeri 
 -nearctic1649,270,9871.88 
 22 
 triatoma longipennis 
 -nearctic / neotropical23310,069,5671.14 
 23 
 triatoma mazzottii 
 -neotropical80696,1399.36 
 24 
 triatoma mexicana 
 -nearctic / neotropical27110,069,5675.96 
 25 
 triatoma pallidipennis 
 -neotropical291690,7501.79 
 26 
 triatoma phyllosoma 
 -neotropical40650,0954.11 
 27 
 triatoma picturata 
 -neotropical16680,5672.87 
 28 
 triatoma recurva 
 -nearctic339,275,3674.29 
 29dimidiata 
 triatoma dimidiata hg 1-neotropical77650,0954.78 
 30 
 triatoma dimidiata hg 2-neotropical485701,5416.60 
 31 
 triatoma dimidiata hg 3-neotropical42650,0392.71 
 32 
 triatoma hegneri 
 -neotropical6 - -33 
 belminus costaricensis 
 -neotropical2 - -34 
 dipetalogaster maximus 
 -nearctic6 - -35 
 eratyrus cuspidatus 
 -neotropical13650,0951.44 
 36 
 panstrongylus rufotuberculatus 
 -neotropical9 - -37 
 paratriatoma hirsuta 
 -nearctic569,230,4646.69 
 38 
 triatoma gomeznunezi 
 -neotropical1 - -  total---2,580 - - 
 trypanosoma cruzi 
 -nearctic / neotropical66910,069,5674.48 

 
an additional dataset was constructed for mexico and the usa for known t. cruzi 
 occurrences using infections in reservoirs , triatomines and human cases 
 georeferenced to communities across mexico from the institute for epidemiologic 
 diagnosis and reference , national center for preventive programs and disease control , 
 published reports and unpublished data of the first author , which totalled 669 records 
 from 1936 - 2014 .
all occurrence data for triatominae and t. cruzi are 
 available on dryad for open access and use by the broader community ( doi : 
 10.5061/dryad.rq120 ) . 

enms - ecological niches were calibrated using desktopgarp ( genetic 
 algorithm for rule set prediction ) ( nhm.ku.edu/desktopgarp/ ) , an evolutionary computing 
 software package available for public download ( stockwell & peters 1999 ) .
specifically , garp relates the ecological 
 characteristics of known occurrence points to those of points randomly sampled from the 
 remaining calibration area , seeking to develop a set of decision rules that best 
 summarise factors associated with the species presence ( peterson et al .
input occurrence data are divided into 
 calibration ( 70% ) and evaluation ( 30% ) subsets ( anderson 
 et al . 2003 ) .
garp works in an iterative process of rule selection , 
 evaluation , testing and incorporation or rejection .
a method is chosen from a set of 
 possibilities ( i.e. , logistic regression , bioclimatic rules ) , it is then applied to the 
 calibration data and a rule is developed or evolved .
rules may evolve by a number of 
 means that mimic dna evolution : point mutations , deletions , crossing over etc . the 
 change in predictive accuracy from one iteration to the next
is used to evaluate whether 
 a particular rule should be incorporated into the model and the algorithm runs either 
 1,000 iterations or until convergence .
we used 13 data layers to characterise ecological 
 landscapes : four layers summarising aspects of topography ( elevation , slope , aspect and 
 topographic index ) from the us geological survey s hydro-1k data set ( usgs.gov/ ) and 
 nine climate variables from worldclim ( bio 1 , 4 , 5 , 6 , 7 , 12 , 13 , 14 , 15 ) 
 ( worldclim.org/ ) selected based on low inter - correlations ( r < 0.75 ) 
 in an analysis of multicollinearity ( moo - llanes et al . 

we assigned species to biogeographic regions for calibration areas if more than 80% of 
 the data points fell inside one region ( neotropical or nearctic ) ; three species 
 ( triatoma longipennis , triatoma mexicana , triatoma barberi ) were 
 classified as nearctic / neotropical because occurrences fell in both regions . 

additionally , species were assigned to biogeographic subgroups based on overall range 
 areas , such that triatoma peninsularis was assigned to subgroup 1 of 
 the nearctic region ( nearctic 1 ) due to its exclusive presence in the baja california 
 peninsula .
neotropical species were also divided into two subgroups based on overall enm areas : 
 smaller than 70,000 km ( neotropical 1 ) or greater than 100,000 
 km ( neotropical 2 ) . to avoid potential modelling bias related to an 
 important component of model calibration , the accessible region 
the occurrences of each species were assessed to determine 
 whether data points were within 100 km of the biogeographic region border : such species 
 were triatoma brailovskyi , t. dimidiata hg2 , triatoma 
 gerstaeckeri , triatoma mazzottii , triatoma pallidipennis , triatoma picturata , t. 
 recurva and t. rubida .
a 100-km radius buffer was created 
 around each occurrence point of these species to extend the limits of the calibration 
 region ( owens et al .
model accuracy was assessed by examining the omission rates associated with the 
 evaluation points ( anderson et al .
enms 
 were thresholded such that at least 95% of the occurrence points were within the 
 predicted area and these thresholds were used to convert model outputs into binary maps 
 ( presence / absence ) . to test model significance , we compared the predictive success of 
 the models against null expectations using a cumulative binomial test ( peterson et al .
the range size of each species modelled was calculated as the number of pixels covered 
 by its suitable area within m ( moo - llanes et al . 

2013 ) . to calculate the elevational ranges for each species , we combined the 
 elevation layer for each vector with model predictions and the elevation layer for 
 t. cruzi .
the average elevation was calculated as the geometric mean elevation of 
 pixels classified as suitable ( moo - llanes et al . 

land use data from the national forestry inventory ( semarnat - nfi 2007 ) 
 were reclassified into  conserved  and  modified  categories ( table ii ) .
all enms were combined and the binary 
 presence / absence raster was overlaid on the forestry classification data to map and 
 calculate the proportion of pixels in each category . 

table iireclassification of the national forestry inventory for conserved and 
 modified land useland 
 useconservedmodifiedagriculture ( seasonal)-xagriculture ( irrigation and humidity)-xno apparent vegetation - xhuman settlement - xdeciduous and semi - deciduousx - conifersx - conifers - broadleaf evergreen forestx - broadleaf evergreen forestx - xerophilous scrublandx - mesophilous mountainx - mezquitex - other vegetationx - grasslandsx - perennial and sub - perennialx - planted forest - xhydrophilic vegetationx- 
  enms for the 19 mexican triatomine species were combined with that for t. 
 cruzi to develop a map summarising coincidence and the potential for 
 transmission by each species .
each map was combined with the mexican census database 
 ( inegi.gob.mx ) to link to all registered communities in mexico ( 192,246 total ) ( doi : 
 10.5061/dryad.rq120 ) and calculate the resident population at risk for t. 
 cruzi vector transmission for rural ( < 10,000 inhabitants ) and urban 
 ( > 10,000 inhabitants ) categories , as reported in moo - llanes et al .
triatomine species richness and t. cruzi vector - transmission - to 
 estimate current triatomine species richness across mexico , the 19 triatomine enms were 
 adjusted to include only the portion of the enm covered by 100-km buffers surrounding 
 known occurrences ( estimate of m ) for each species , thereby eliminating areas that were 
 likely unoccupied by species ( olson et al .
occurrence point buffers ( 100-km , based on appropriate environmental space models ) were 
 created for the remaining 12 species and seven additional subspecies of t. 
 protracta and t. rubida and these buffers were overlain 
 with the 19 adjusted enms .
a t. cruzi vector transmission map was 
 developed using the triatomine species richness model and the t. cruzi 
 enm .
the two binary models were combined ( arithmetic sum of binary classification ) using 
 the map algebra function of the spatial analyst of arcgis v.10.0 to project the current 
 exposure for t. cruzi vector transmission . 

data analyses - differences for enm mean breadth , mean elevation , 
 modified and conserved land coverage , conserved / modified land cover index , rural / urban 
 population index , rural population , land cover and conserved / modified land cover index 
 among the biogeographic regions were evaluated using one - way anova ( tukey s f for 
 comparison of means ) using r software v.2.15.1 ( r-project.org/ ) .

 enms - the binomial tests of the ability to predict known distributions 
 were significant ( p < 0.05 ) for all but three species : paratriatoma hirsuta , 
 t. lecticularia and t. brailovskyi ( table i ) .
enms for the 19 triatomine species analysed are 
 presented according to biogeographic region , with occurrence data points shown in figs 
 1 - 5 .
the species with the broadest geographic distributions in mexico were those from 
 the nearctic region ( nearctic 2 ) ( fig .
4 ) , with 
 t. protracta s distribution being the largest ( 55.1% of the country ) 
 and t. peninsularis s ( nearctic 1 ) ( fig . 
 5 ) being the smallest ( 1.2% ) ( table 
 iii ) .
1 ) , followed by the principal neotropical group 
 ( neotropical 2 ) ( fig .
3 ) ; the nearctic 2 region 
 had a mean range size that was significantly higher than those of all other groups 
 ( table iv ) ( df = 3 , f = 8.8 , p = 0.0016 ) .
the 
 potential distributions of nearctic 2 species covered the greatest proportion of the 
 country ( average 36.5% ) , whereas species in nearctic / neotropical cover an average 19% 
 and the principal neotropical region 2 , 12.4% of mexico ( table iv ) . generally , all triatoma complexes had similar 
 ranges : the protracta complex species covered between 1.2 - 55.1% of the country , the 
 phyllosoma complex species covered between 1.7 - 43.8% and the dimidiata complex species 
 covered between 3.2 - 20.1% of the country . 

4:ecological niche models for mexican triatominae distributed in the 
 nearctic region , subgroup 2 .
colour brown to blue for increasing best subset 
 models , black dots are occurrence points . 
 

5:ecological niche models for mexican triatominae distributed in the 
 nearctic region , subgroup 1 .
colour brown to blue for increasing best subset 
 models , black dots are occurrence points . 
 

table iiiniche breadth and elevation for ecological niche models of the 19 most 
 abundant mexican triatomine speciesidspeciesbiogeographic 
 regionbackground modelniche breadth 
 mexicoenm mexico ( % ) elevation mean 
 ( m)elevation range ( m ) 
 ( min - max)1 
 triatoma peninsularis 
 nearctic 19.23020,8921.2102(0 - 225)2 
 triatoma brailovskyi 
 neotropical 10.65228,7351.7409(39 - 1,041)3 
 triatoma picturata 
 0.68039,4572.31,286(718 - 1,731)4 

triatoma dimidiata hg 30.65055,3913.2658(88 - 1,395)5 
 eratyrus cuspidatus 
 0.65064,9123.8877(342 - 2,289)6 
 triatoma dimidiata hg 1neotropical 20.65099,9695.844(1 - 190)7 
 triatoma phyllosoma 
 0.650144,0828.4832(18 - 1,850)8 
 triatoma pallidipennis 
 0.690153,4148.91,210(622 - 1,781)9 
 triatoma mazzottii 
 0.696321,17018.7838(22 - 1,785)10 
 triatoma dimidiata hg 20.701344,14220.1259(10 - 1,045)11 
 triatoma mexicana 
 nearctic/ 
 neotropical10.069206,127121,371(113 - 2,107)12 
 triatoma longipennis 
 10.069338,87819.71,354(377 - 2,084)13 
 triatoma barberi 
 10.069435,23825.41,751(1,047 - 2,321)14 
 triatoma lecticularia 
 nearctic 29.230166,8379.7433(92 - 975)15 
 triatoma recurva 
 9.275751,62043.8768(14 - 1,587)16 
 triatoma gerstaeckeri 
 9.270434,24225.3792(18 - 1,598)17 
 triatoma rubida 
 9.283832,34548.5607(1 - 1,325)18 
 triatoma protracta 
 9.230945,64355.1946(28 - 1,889)19 
 paratriatoma hirsuta 
 9.230625,62536.5896(48 - 1,642)- 
 trypanosoma cruzi 
 nearctic/ neotropical10.0691,565,39291.2786(10 - 1,900)background model expressed values in millions of pixels .
colour brown to blue for increasing best 
 subset models , black dots are occurrence points . 
 

3:ecological niche models for mexican triatominae distributed in the 
 neotropical region , subgroup 2 .
colour brown to blue for increasing best subset 
 models , black dots are occurrence points . 
 

table ivniche breadth , elevation , population coverage and land use indices for 
 biogeographic regions  biogeographic region 

 nearctic 1neotropical 1neotropical 2nearctic / neotropicalnearctic 2 

 species ( n)14536fp 

 mean breadth ( km)20,89247,124 
 212,555 
 326,748 
 626,052 
 8.791.60 
 coverage for mexico ( % ) 1.22.7 
 12.4 
 19 
 36.5 
 8.781.60 
 mean elevation ( m)102807 
 637 
 1,492 
 740 
 4.502.06 
 total range elevation ( m)2251,317 
 1,196 
 1,658 
 1,469 
 0.685.78 
 rural population ( n)330,2443,980,399 
 11,348,692 
 25,390,610 
 8,844,201 
 3.633.96 
 rural / urban population index0.091.31 
 0.75 
 0.48 
 0.37 
 5.669.40 
 rural communities ( n)4,32021,326 
 55,614 
 116,848 
 64,329 
 10.976.00 
 urban communities ( n)1683 
 251 
 640 
 236 
 20.580modified land cover ( km)70318,725 
 85,670 
 127,948 
 126,098 
 5.001.18 
 conserved land cover ( km)20,07828,399 
 126,671 
 193,957 
 501,454 
 10.208.00 
 conserved / modified index28.561.57 
 1.63 
 1.49 
 3.91 
 19.390 
 a , b : statistically different ( p < 0.05 ) . 

triatoma peninsularis ( nearctic 1 ) is not included in 
 analyses . the mean elevation for enms varied from 44 m ( t. dimidiata hg1 ) to 
 1,751 m ( t. barberi ) ( table 
 iii ) .
the highest mean elevation was observed for species located in both 
 nearctic / neotropical regions , followed by the neotropical region which had lowest niche 
 breadth ( neotropical 1 ) ; mean elevation of the nearctic / neotropical regions was 
 significantly higher than all others ( table iv ) 
 ( df = 3 , f = 4.50 , p = 0.021 ) .
species of both nearctic regions had the lowest mean 
 elevations . the enms of nearctic 2 triatomine species had predominately conserved land cover ( 79.2% ) 
 ( fig .
6 ) , whereas other regions had equivalent 
 proportions of conserved and modified land cover : 59.9% , 61.2% and 59.1% for conserved 
 land cover in the nearctic / neotropical , neotropical 2 and 1 regions , respectively ( fig . 7 , table 
 iv ) ( df = 3 , f = 10.2 , p = 0.0008 ) .
the conserved / modified land cover index 
 for the nearctic 2 region was significantly different from that of the other three 
 regions ( df = 3 , f = 19.4 , p < 0.0001 ) .
the modified land cover area was similar 
 between the nearctic 2 group and the nearctic / neotropical regions , both of which were 
 slightly lower than that of the neotropical 2 group ( df = 3 , f = 5.0 , p = 0.001 ) . 

t. picturata had the smallest area of conserved land cover ( 0.80 ) , 
 whereas t. peninsularis , which is highly sylvatic and reduced to the 
 baja california peninsula , had the highest conserved / modified land cover ratio 
 ( 28.6 ) . 

6:composite binary map of all triatominae ecological niche models ( enm ) 
 classified according to modified ( red ) or conserved ( green ) landscape 
 cover . 
 
 fig .
7:landscape cover types and conserved / modified index for mexican 
 triatominae ecological niche models . 
 

triatomine exposure of the mexican population - t. cruzis enm was 
 found to cover 91.2% of mexico ( fig .
the total 
 mexican population with vector exposure for at least one bug species was 99,911,867 
 inhabitants , which is 88.9% of the current mexican population .
this coverage was similar 
 for rural ( 88.1% ) and urban populations ( 89.4% ) ( table 
 v ) .
more than 90.1% of the communities in the country are located in potential 
 vector distribution areas .
vector transmission models were overlaid onto the 2010 census 
 database to stratify exposure for all communities in the country ( doi : 
 10.5061/dryad.rq120 ) : the exposed population was highest where triatomines covered both 
 biogeographic regions ( t. longipennis , t. mexicana and t. 
 barberi ) , followed by regions where nearctic 2 and neotropical 2 species 
 occur . the mean exposed populations were significantly different among biogeographic 
 regions ( table iv ) ( df = 3 , f = 3.64 , p = 
 0.04 ) . 
 fig .
black dots are 
 occurrence points for the species from bugs , humans and other mammals . 
 

table vurban and rural population and communities exposed to triatominae in 
 mexicovectortotal population 
 ( n)urban population 
 ( n)rural populationrural / urban 
 population indexurban communities 
 ( n)rural communities 
 ( n ) 
 triatoma peninsularis 
 3,9923,6610.3300.09164,320 
 triatoma brailovskyi 
 1,1320,3390.7922.33115,494 
 triatoma picturata 
 13,4998,5114.9880.5915223,997 
 triatoma dimidiata hg 312,5345,0187.5161.5011441,254 
 eratyrus cuspidatus 
 5,8023,1782.6230.835514,561 
 triatoma dimidiata hg 18,4154,8103.6040.757917,314 
 triatoma phyllosoma 
 16,6349,7836.8500.7015934,431 
 triatoma pallidipennis 
 29,21417,86011.3540.6429052,898 
 triatoma mazzottii 
 42,59824,63917.9580.7341287,962 
 triatoma dimidiata hg 234,71517,74016.9740.9631385,467 
 triatoma mexicana 
 67,00547,51419.4910.4149693,638 
 triatoma longipennis 

triatoma lecticularia 
 22,46016,2756.1840.3816843,740 
 triatoma recurva 
 29,86821,5318.3370.3923060,065 
 triatoma gerstaeckeri 
 38,04726,35011.6960.4427480,422 
 triatoma rubida 

42,94231,60111.3400.3630179,886 
 triatoma protracta 
 37,46027,22610.2340.3826373,506 
 paratriatoma hirsuta 
 24,89619,6245.2710.2717748,355urban communities are classified as  10,000 inhabitants .
population is 
 expressed in millions of inhabitants . although the average exposed population in urban and rural areas as well as rural and 
 urban communities was the highest for species occurring in both biogeographic regions , 
 the group with the highest rural / urban index was the smaller of the neotropical groups 
 ( neotropical 1 ) ( fig .
more inhabitants from rural than 
 urban communities were exposed ( rural / urban index = 1.31 ) .
none of the other 
 biogeographic groups had an index above 1 , indicating that more inhabitants in urban 
 communities were exposed to vector transmission than those in rural populations in these 
 regions ; the rural / urban index was significantly different among biogeographic groups 
 ( table iv ) ( df = 3 , f = 5.66 , p = 0.009 ) .
the 
 highest proportion of exposed urban population was found in the nearctic 2 region , 
 followed by that from species covering both regions and the neotropical 2 group , which 
 was similar to the trend for niche breadth . 

2:ecological niche models for mexican triatominae distributed in the 
 neotropical region , subgroup 1 .
colour brown to blue for increasing best subset 
 models , black dots are occurrence points . 
 

triatomine species richness and t. cruzi transmission niche - species 
 richness for mexican triatominae based on adjusted enms ( for current and not potential 
 distributions ) was higher in the neotropical region than in the nearctic region ( fig .
the areas of the greatest species richness 
 were the sierra madre oriental , the transverse neovolcanic belt , northern sonora , along 
 the pacific coast and the sierra madre occidental , the balsas basin and the sierra madre 
 del sur and oaxaca coast . 

the vector transmission map suggests that the greatest exposure of human populations to 
 infected triatomine species occurs in nuevo leon , tamaulipas , sinaloa , durango , nayarit , 
 jalisco , guanajuato , michoacan , oaxaca and chiapas ( fig . 

all human communities in nine states ( of 32 ) , aguascalientes , coahuila , 
 guanajuato , hidalgo , morelos , nayarit , quertaro , san luis potosi and tlaxcala , are at 
 risk for the potential vector - borne transmission of t. cruzi by at 
 least one infected bug species ( doi : 10.5061/dryad.rq120 ) . 
 fig .
colours green to red 
 represent increasing number of ecological niche model best subsets . 

species distributions of triatomines have been modelled previously in several mexican 
 states : guanajuato ( lpez - crdenas et al .
2008 ) , veracruz 
 ( sandoval - ruiz et al . 2012 ) , aguascalientes , 
 chiapas , guerrero , jalisco , michoacan and oaxaca ( bentez - alva et al . 2012 ) .
however , most of these studies did not use 
 representative occurrence datasets covering the complete range of the species modelled 
 or they failed to specify background areas to calibrate their models , resulting in 
 calibration bias ( owens et al .
the present 
 study separately modelled the 19 most abundant and epidemiologically relevant triatomine 
 vector species in mexico , providing individual species maps and exposure databases , 
 which can be used by mexico s phs vector prevention and control program to stratify 
 t. cruzi transmission .
these maps and demographic exposure 
 predictions reflect the potential geographic distributions for all epidemiologically 
 relevant species and their interactions with t. cruzi and can be used 
 to stratify vector transmission interventions if the political will exists and normative 
 guidelines are followed .
mexico is located in both the neotropical and nearctic regions , which have different 
 topography , vegetation , climates and demography as well as high heterogeneity and 
 landscape types ( olson et al .
we noted significant differences in distribution potential 
 among species occurring in different biogeographic regions , with species in the semiarid 
 and arid nearctic region having the broadest distributions .
however , species richness 
 was highest in the neotropical region , which has greater topographic complexity , 
 particularly along the pacific coast .
it is interesting that the broadest potential 
 vector distributions in the nearctic region coincided with the higher conserved / modified 
 land cover index values , probably owing to vast areas of arid vegetation with low 
 population density , as evidenced by the inverse association with the rural / urban 
 population index .
recent studies on triatomines from the nearctic region of mexico 
 report the domestication of vector species such as t. rubida and 
 t. protracta in urban areas , which was almost unheard of two decades 
 ago ( pfeiller et al .
it is clear that the geographic ranges of three principal triatomine species , t. 
 longipennis , t. mexicana and t. barberi occur at higher 
 elevation and expose more rural and urban communities to t. cruzi , even 
 though the rural / urban population index in this region is the lowest .
for these three 
 species and for the most important species from the neotropical 2 region , these data 
 suggest that the vectors have tolerated landscape modification and urban development and 
 are not limited to rural populations .
this urbanisation process , along with strong cultural ties 
 to ancestral communities , may provide mechanisms for continuous human - assisted vector 
 dispersal .
most mexican vectors have tolerated landscape modification and as true 
 opportunists , take advantage of alternative resources and refuges to maintain 
 populations in human - modified habitats . because the phs vector - borne disease program in 
 mexico is currently almost singularly focused on dengue , which is principally urban , a 
 chagas disease prevention and control program , if it were to become effective in mexico , 
 may not need to shift current personnel or their work areas .
however , this strategy may 
 broaden the gap between urban and rural phs coverage , thereby increasing current 
 inequities in health services access in dispersed and marginalised rural areas where 
 investment in prevention and control is minimal and will be far more costly to 
 maintain .
the present analysis provides an atlas of the current knowledge regarding potential 
 distributions and hence the potential exposure of human populations to t. 
 cruzi - infected vectors in mexico .
this information can be used to engage 
 communities regarding chagas disease and to analyse social , cultural and economic 
 vulnerability components that contribute to vector transmission risk .
we have related 
 triatomine distribution patterns to the most recent demographic census in mexico to 
 provide chagas state program coordinators with a blueprint with which to stratify , study 
 and plan future activities .
stratification should be conducted based on vector capacity , 
 domesticity and the degree of habitat modification .
current models can be improved 
 via a concerted effort to generate distribution and abundance 
 information in communities and in conserved areas .
although information regarding 
 wildlife reservoirs of t. cruzi is increasing and will assist in 
 understanding the ecology of t. cruzi vector - borne transmission , the 
 current information void ( for the mexican population and professionals in phs ) regarding 
 the vectors and the parasite is the primary impediment to understanding vector 
 transmission risk .
the chagas disease transmission map developed herein was adjusted to reflect the current 
 infected vector distributions and hence is immediately applicable to the unaddressed 
 t. cruzi vector transmission problem in mexico .
few areas in mexico 
 do not have the potential for vector transmission exposure and vectors have already 
 demonstrated the capacity to persist in human - modified habitats and communities , which 
 in most nearctic and neotropical regions provide the greatest year - round resources . if 
 this exposure hazard continues and human vulnerability remains unabated , the risk for 
 vector transmission in mexico will continue to rise , affecting economic development and 
 broadening the social inequities already affecting most of the population in both rural 
 and urban areas ( ramsey et al .
this study 
 has developed immediately usable products for the phs to study , plan and intervene 
 against the vector - mediated transmission of t. cruzi .
how many more 
 mexicans must become infected before health agencies abide by their legal mandate to 
 prevent , control and turn their attention to chagas disease in the country ?
 chagas disease is one of the most important yet neglected parasitic diseases in 
 mexico and is transmitted by triatominae . 
 nineteen of the 31 mexican triatomine 
 species have been consistently found to invade human houses and all have been found 
 to be naturally infected with trypanosoma cruzi . 
 the present paper 
 aims to produce a state - of - knowledge atlas of mexican triatomines and analyse their 
 geographic associations with t. cruzi , human demographics and 
 landscape modification . 
 ecological niche models ( enms ) were constructed for the 19 
 species with more than 10 records in north america , as well as for t. 
 cruzi . the 2010 mexican national census and the 2007 national forestry 
 inventory 
 were used to analyse overlap patterns with enms . 
 niche breadth was greatest 
 in species from the semiarid nearctic region , whereas species richness was associated 
 with topographic heterogeneity in the neotropical region , particularly along the 
 pacific coast . 
 three species , triatoma longipennis , triatoma 
 mexicana and triatoma barberi , overlapped with the 
 greatest numbers of human communities , but these communities had the lowest 
 rural / urban population ratios . 
 triatomine vectors have urbanised in most regions , 
 demonstrating a high tolerance to human - modified habitats and broadened historical 
 ranges , exposing more than 88% of the mexican population and leaving few areas in 
 mexico without the potential for t. cruzi transmission . 
MATERIALS AND METHODS
RESULTS
DISCUSSION