Life history data of four populations of Triatoma mexicana (Hemiptera: Reduviidae) from Central Mexico.

Triatomine bugs are vectors for the Trypanosoma cruzi Chagas parasites, the etiological agent for Chagas disease. This study evaluated 6 epidemiologically significant behaviors (development time, number of blood meals required for molting to the next instar, mortality rate, aggressiveness, feeding duration, and defecation delay) across 4 populations of Triatoma mexicana Herrich-Schaeffer (Heteroptera: Reduviidae), a major T. cruzi vector in Central Mexico. We collected triatomines from areas characterized by high (HP), medium (MP), medium-high (MHP), and low (LP) prevalence of human T. cruzi infection. The MHP population had the shortest development time, <290 days. Both the HP and MP populations required the most blood meals to molt to the next instar, with a median of 13. Mortality rates varied across all populations, ranging from 44% to 52%. All of the tested populations showed aggressive behavior during feeding. All populations shared similar feeding durations, with most exceeding 13 min and increasing with each instar. Quick defecation, during feeding, immediately after or less than 1 min after feeding, was observed in most nymphs (78%-90%) from the MP and MHP populations and adults (74%-92%) from HP, MP, and MHP populations. Though most parameters suggest a low potential for T. mexicana to transmit T. cruzi, unique feeding and defecation behaviors in 3 populations (excluding the LP group) could elevate their epidemiological importance. These population-specific differences may contribute to the varying prevalence rates of T. cruzi infection in areas where T. mexicana is found.

Trypanosoma cruzi in Wild and Synanthropic Mammals in Two Regions of Mexico: A Fieldwork and Genetic Discrete Typing Unit Review.

Background: Marsupials and rodents are the most important wild and synanthropic hosts of Trypanosoma cruzi due to the high frequency of infection, maintenance of diverse genetic populations of the parasite, and their close proximity to interact with both transmission cycles, sylvatic and peridomestic. Our aim was to identify the discrete typing units (DTU) of T. cruzi from different wild and synanthropic hosts in two regions of Mexico and to carry out a review of historical data focusing on current knowledge on the diversity and T. cruzi DTUs of host species. Materials and Methods: One hundred fifteen samples were obtained from two areas in Tabasco and Nayarit state. The presence of T. cruzi was evaluated by PCR. Results: The 12.6% (12/95) of samples from Tabasco and 65% (13/20) from Nayarit were found to be positive for parasite DNA. All the sequences analyzed were grouped in T. cruzi DTU I; low nucleotide diversity was observed in Tabasco (π = 0.00566, and Ï´ = 0.00632), while high genetic diversity was observed in Nayarit sequences, up to 8.63 (π) to 11.10 (Ï´) times greater than Tabasco sequences. Genetic flow and migration between Tabasco, and Nayarit were scarce (FST = 0.37329 and Nm = 0.42), and genetic exchange was observed only between nearby areas. The bibliographic review of hosts in Mexico, together with our data, shows a heterogeneous T. cruzi prevalence in Chiroptera and domestic animals. For Atelidae and Canids, prevalence is generally below 25%. However, a high prevalence, greater than 25% and up to 100%, was recorded in Didelphimorphia, and Rodentia. Few studies in regions of Mexico have been described as infected with the parasite; in these, the genetic group with the highest prevalence is the DTU I. Conclusion: Marsupials and rodents are important reservoirs of T. cruzi; DTU I was frequently reported; however, recent genetic and reservoir studies have demonstrated the presence of greater diversity of genetic groups.

Behavioral and biological parameters of six populations of Triatoma pallidipennis (Heteroptera: Reduviidae) from areas with high and low prevalence rates of Trypanosoma cruzi human infection.

In Mexico, more than 30 species of triatomines, vectors of Trypanosoma cruzi, the etiological agent of Chagas disease, have been collected. Among them, Triatoma pallidipennis stands out for its wide geographical distribution, high infection rates and domiciliation. Local populations of triatomines have shown notable biological and behavioral differences, influencing their vectorial capacity. Six behaviors of epidemiological importance, namely, egg-to-adult development time, median number of blood meals to molt to the next instar, instar mortality rates, aggressiveness (delay in initiating a meal), feeding time and defecation delay, were evaluated in this study for six populations of T. pallidipennis. Those populations from central, western and southern Mexico were arranged by pairs with a combination of high (HP) and medium (MP) of Trypanosoma cruzi human infection and most (MFC) and low (CLF) collection frequencies: HP/MFC, HP/CLF, and MP/MFC. The development time was longer in HP/CLF populations (> 220 days). The median number of blood meals to molt was similar (7-9) among five of the six populations. Mortality rates were greater (> 40 %) in HP/CLF and one MP/MFC populations. All studied populations were aggressive but exhibited slight differences among them. The feeding times were similar (≥ 10 min) for all studied populations within instars, increasing as instars progressed. An irregular pattern was observed in defecation behaviors, with marked differences even between the two populations from the same pair. High percentages of young (57.3-87.9 %), and old (62.4-89.8 %) nymphs, of female (61.1-97.3 %) and male (65.7-93.1 %) of all the studied populations defecated quickly (while eating, immediately after finishing feeding or < 1 min postfeeding). Our results indicate that the HP/MFC populations are potentially highly effective vectors for transmitting T. cruzi infections, while HP/CLF populations are potentially less effective vectors T. cruzi infections.

Infection with Trypanosoma Cruzi Chagas and Characterization of Human Habitats of Triatoma Picturata (Usinger) in Western Mexico.

Chagas disease is one of the most important vector-borne diseases in Latin America. Triatoma picturata (Usinger), distributed in western Mexico, is one of the most important vectors of Trypanosoma cruzi Chagas. Knowing the type and materials used for building homes could lead to improved methods for controlling triatomines by focusing efforts on controlling every species of triatomine in its specific microhabitat. Houses in three studied localities of western Mexico that harbored T. picturata were characterized, as well as two entomological indices. Infestation Index values varied from 10.8% to 51.9% in the three localities, whereas Natural Infection Index values varied from 18.1% to 35.2%. Characteristics of houses invaded by T. picturata also varied. In Juan Gil Preciado, with the highest Entomological Index values, most houses were built of adobe walls with a roof of clay tiles and a dirt floor, and included the presence of domestic animals. Our data indicate that the potential risk of infection with T. cruzi differs markedly for inhabitants of the three studied localities, which demonstrates the importance of studying local populations of triatomines. Our study should contribute to decision-making regarding triatomine control efforts by providing profiles of houses that are more susceptible to triatomine invasion.

Crossing experiments detect partial reproductive isolation among populations of Triatoma longipennis (Hemiptera: Reduviidae: Triatominae).

Chagas disease is an important vector-borne disease endemic in Mexico. Of the 33 triatomine species found in Mexico, Triatoma longipennis (Usinger) is considered among the most important because of its infection indices, capacity for transmitting Trypanosoma cruzi (Chagas), and its distribution areas. Here, we describe the results of a reproductive isolation analysis among 5 populations of T. longipennis collected from representative areas of Mexico. Fertility and segregation of morphological characteristics were examined in two generations of hybrids. The percentage of pairs with (fertile) offspring varied from 30% to 100% in the parental crosses, while these values varied from 0 to 100% in the intersite crosses. Our results indicate partial reproductive isolation among these populations. These findings shed light on the potential presence of a cryptic species complex of T. longipennis in Mexico.

Biological aspects of crosses between populations of Triatoma mexicana (Hemiptera: Reduviidae: Triatominae).

We examined the degree of reproductive isolation in four populations of Triatoma mexicana Herrich-Schaeffer from Mexico along with fertility and the segregation of morphological characteristics in two generations of offspring from crosses between these populations. The percentage of couples with (fertile) offspring was high among all sets of crosses between cohorts from Peñamiller, Meztitlán, and Orizabita. It was low in crosses involving a cohort from Tierra Blanca, mainly in crosses with Meztitlán. Among sets of crosses involving Tierra Blanca specimens, whole first-generation (F1) individuals were morphologically similar to the specimens from other locations. All F1 individuals of crosses involving Peñamiller looked like Peñamiller. However, in crosses between F1 and F1 progeny of parental crosses, alleles for size, overall color, length of head, ante and post ocular distance, and humeral angle apparently had Mendelian dominant/recessive relationships. The cohorts from Peñamiller and Meztitlán seemed to be dominant with respect to Orizabita and Tierra Blanca. Results indicated that cohorts from Peñamiller, Meztitlán, and Orizabita were not reproductively isolated. In contrast, Tierra Blanca was reproductively isolated from the other three populations of T. mexicana and is apparently undergoing an early divergence process of speciation for allopatry.

Vital statistics of the introduced species Triatoma infestans (Klug, 1834) (Hemiptera: Reduviidae) in western Mexico under laboratory conditions.

Triatoma infestans, one of the most important vectors of Trypanosoma cruzi to humans, has recently been discovered introduced in Mexico. Some of the most important biological parameters to estimate the vectorial capacity of a triatomine, such as the hatching of eggs, life cycle, feeding and defecation behaviors for each instar of a population of T. infestans introduced into Mexico are reported. The egg-to-adult development times of the three studied cohorts had a mean of 215.7 days. The mean total number of blood meals required to molt from first-instar nymphs to adults was 11.7. The cumulative mortality was 30.8%. The highest mortality rate was recorded for third-instar nymphs (10.3%), whereas the lowest rate (0.8%) was recorded for first-instar nymphs. All studied specimens began feeding as soon as a blood meal source was offered, showing "aggressive" behavior. Feeding times were ˃ 10 min for all instars, increasing according to instar, in a similar pattern to the development times and the required blood meals before molting. Most (57.7 -82.5%) of the studied specimens of the first- to third-instar nymphs and adults of T. infestans defecated when feeding (WF). The average number of eggs laid per female per day was 0.9, with an eclosion rate of 96.4%. The results of most of the studied parameters confirm the importance of T. infestans wherever it is found because of its potential high capacity for transmitting T. cruzi to hosts. Active entomological surveillance should be carried out in the area of the first discovery of the introduced T. infestans and its surroundings to avoid the dissemination of this effective vector species in Mexico.

Influence of blood meal source on the biological parameters of Triatoma pallidipennis (Heteroptera: Reduviidae) from Mexico.

Chagas disease is one of the most important vector-borne diseases in Latin America, including Mexico. Triatoma pallidipennis (Stål) (Hemiptera: Reduviidae) is a Mexican triatomine vector commonly associated with different hosts. The influence of six blood meals (rabbits, rats, mice, dogs, cats and chickens) on six biological parameters of the biology of T. pallidipennis was evaluated. A significant difference was found in the period of egg-to-adult development between the five mammalian feeds (mean 195 days) and the chicken feed (221 days). The probability of survival was significantly lower in the chicken cohort (0.285). The total number of blood meals to moult from the first instar to the adult stage was the highest in the chicken cohort (10-15). This cohort had the significantly highest rate of females at the end cycle. The mean number of eggs laid per female and the egg eclosion rate were similar among the six food sources. Most results seemed to be influenced by the higher nutritional quality of the mammalian blood compared to the bird's blood and the increased energy expenditure required for the digestion of bird blood. These results clearly show that T. pallidipennis, unlike other triatomine species, has a high reproductive capacity when feeding on different hosts.

Impact of home improvements and health education on the transmission of Trypanosoma cruzi Chagas in a rural area of western Mexico.

Chagas disease is one of the most important vector-borne diseases in Latin America. Instituting home improvement preventive measures and increasing health education contribute to successful control of the triatomine insect vector. The impact of home and road improvements and health education upon the inhabitants of 37 human dwellings in three small towns in western Mexico were studied. Initially, few house roofs were made of concrete and few walls were cement-lined. Almost all houses initially lacked metal window screens and none used barbed wire fences. One year after the intervention, all of these measures were more common, and almost 100% of houses continued to use window screens and barbed wire fences ten years post-intervention. By ten years post-intervention, >75% of houses had cement-lined walls. Initially, 24.3% of human dwellings were infested with Triatoma longipennis Usinger; at one and ten years post-intervention, only 2.7% of dwellings were infested. The abundance of peridomestic opossums decreased after intervention and remained low ten years later. Approximately 10% of dogs were infected in both surveys. Human infections decreased from 2.98% to zero by 13 years post-intervention. Implementation of these intervention measures led to the successful control of Trypanosoma cruzi Chagas transmission in these towns.

New finding of peridomestic Triatoma infestans (Klug, 1834) (Hemiptera: Reduviidae) in Mexico: Molecular approach using cytochrome B and cytochrome oxidase I.

A previous work morphologically identified some specimens colonizing peridomestic sites of Manzanillo Colima, Mexico, as Triatoma infestans (Klug). In the present study, a molecular approach using cytochrome B and cytochrome oxidase I was implemented for the genetic identification and determination of the origin of that population. Phylogenetic analyses positively identified our studied specimens as belonging to the T. infestans clade based on genetic markers with high posterior probability values, and the haplotype network showed Uruguay, Chile and Argentina as probable countries of origin of the populations in Mexico, which was supported by gene flow and migration index analyses. Due to the proximity of the port of Manzanillo to the collection sites, the introduced specimens were hypothesized to have travelled from the countries of origin to Mexico in a seed shipment inside a TEU (twenty-foot equivalent unit) maritime container. The identification of T. infestans in Mexico represents a serious health problem, and the findings presented here indicate a novel pathway for displacing this vector with the possibility of transmission to any other part of the world, which should be further investigated.

Population structure and genetic diversity of Triatoma longipennis (Usinger, 1939) (Heteroptera: Reduviidae: Triatominae) in Mexico.

Triatoma longipennis (Usinger) is an important vector of Trypanosoma cruzi in western, central and northern Mexico, due to its wide distribution, high infection rates, and epidemiological indices. However, its population genetics has not been completely characterized. In this study, the intra-specific relationships between different T. longipennis populations were analyzed from seven states in Mexico using mitochondrial cyt B as a marker. Our results show that the population of Jalisco was the most diverse, with the highest genetic and haplotypic variation (Hd = 0.978, π = 0.099 and θ = 0.079), even 25 times higher than some other populations analyzed. Heterogeneous migration and gene flow were observed without relation to their geographical distribution, that is, nearby populations may present high values of gene flow with low migration. In contrast, remote populations have low gene flow values with high migration. Genetic isolation was apparently present in the Guanajuato population, however, Mantel's analyzes to determine when an isolation by distance is present did not show correlation between genetic (FST) and geographic (Km) distances (P = 0.064). The STRUCTURE analyzes showed that populations such as Chihuahua, Jalisco, Nayarit and Michoacán appear to show a similar population structure, suggesting a common ancestor. Our results suggest two routes of diversification of T. longipennis highly influenced by anthropogenic effects. Elucidation of the population genetic structure of T. longipennis will help to better understand the role of gene flow and migration in the dispersal of this important Chagas disease vector.

Life cycle of Triatoma huehuetenanguensis Lima-Cordón, Monroy, Stevens, Rodas, Rodas, Dorn, Justi 2019 (Hemiptera: Reduviidae: Triatominae) from Mexico.

Several important biological parameters for estimating the vectorial capacity of a triatomine species were determined on a Mexican population of the recently described Triatoma huehuetenanguensis Lima-Cordón, Monroy, Stevens, Rodas, Rodas, Dorn, Justi (Hemiptera: Reduviidae: Triatominae). The biological parameters were the egg-to-adult development time, number of blood meals required for molting, cumulative mortality, onset time for feeding, feeding and defecation behaviors, and fertility and fecundity of T. huehuetenanguensis. The median egg-to-adult development time was 253 days, with 11 blood meals required for molting. A cumulative mortality rate of 47.41% was observed. The time to begin feeding was between 2.5 and 3.5 min. Feeding times were longer than 15 min. The highest percentages of defecation delays were 1 to 10 min in all nymphal instars and also in males. In contrast, significantly (P < 0.01) more females defecated while eating. At the end of the cycle, the percentage of the obtained females was 54.9%. The mean number of eggs laid per day per female for a month was 2.08. These eggs had an eclosion rate of 98.08%, with an incubation period of 19 days. Our results contribute to estimations of the potential role of T. huehuetenanguensis in the transmission of Trypanosoma cruzi in its distribution area.

Biological parameters and estimation of the vectorial capacity of two subspecies of Triatoma protracta (Uhler) and their laboratory hybrids in Mexico.

Chagas disease is one of the most important vector-borne diseases in Latin America. Studying the biological parameters of each vector species or subspecies contributes to our understanding of their epidemiologic importance. The aim of our study was to compare the biological parameters and start to estimate the vectorial capacity of Triatoma protracta protracta Ryckman, T. p. nahuatlae Ryckman, and their laboratory hybrids. Specifically, we estimated nine biological parameters to increase knowledge about the potential role of triatomine hybrids in the transmission of T. cruzi to reservoir hosts. Nine biological parameters related to the lifecycle, feeding and defecation patterns, number of females, fecundity, and egg eclosion rates in cohorts of T. p. protracta, T. p. nahuatlae, and their hybrids were evaluated and compared. Eight parameters (exception: number of laid eggs) indicated that T. p. nahuatlae was a potentially effective vector of T. cruzi. Our results showed that the hybrid cohorts had better fitness and could potentially have higher vectorial capacity than the parental cohorts. The outstanding characteristics of the hybrids found in our study could lead to an increase in the epidemiologic risks caused by transmission of T. cruzi to humans.

Behavioral parameters of six populations of Meccus phyllosomus longipennis (Heteroptera: Reduviidae) from areas with high and low prevalences of Trypanosoma cruzi human infection.

Three behaviors of epidemiological importance, namely feeding latency, feeding duration and defecation latency, for six populations of Meccus phyllosomus longipennis (Usinger) from areas of central, western and north-central Mexico with high (HP) and low (LP) prevalence of Trypanosoma cruzi (Chagas) human infection were evaluated in this study. The median feeding latency (the time taken to begin feeding) was highly variable between instars. Within-instar comparisons showed that at least 65% of the LP populations (N3 to adult) started to feed significantly (P < 0.05) later than the HP population, with N1 showing no difference, and N2 from LP populations feeding sooner than those from HP populations. The six populations had similar median feeding durations within instars. A higher (P < 0.05) percentage of the instars from HP populations defecated faster than the respective instars from the three LP populations. Approximately 25% of the young nymphs (N1 to N3) and females in the HP populations defecated < 2 min postfeeding, compared with 4%-6% of the young nymphs and 1.3%-3% of females in the LP populations. Moreover, 17.7%-38.8% of the older nymphs (N4 to N5) in the HP populations and 6.8%-13.4% in the LP populations defecated during or immediately after feeding. Our results indicate that the HP populations have a greater potential than the LP populations to transmit T. cruzi infections, which may underlie the differences in the prevalence of T. cruzi infection in some areas where M. p. longipennis is currently distributed.

Molecular genotyping of Blastocystis spp. in wild mammals from Mexico.

Blastocystis spp. are common intestinal parasites found worldwide in humans and a wide range of animals. They exhibit extensive genetic diversity; currently, 17 subtypes (STs) and some groups called non-mammalian and avian STs (NMASTs) have been proposed. In addition, a large variety of animals have been reported as hosts of the parasite, and new hosts and STs are still being described. In this study, Blastocystis infection of wild animals in two sylvatic areas of Mexico was surveyed. Of one hundred twenty-four fecal samples, six were positive for Blastocystis: specifically, one sample from an opossum, one sample from a bat, and four samples from different species of rodents. ST4, ST17, and nucleotide sequences similar to Blastocystis lapemi were identified based on SSU rDNA sequences. To our knowledge, this is the first report to investigate species poorly or not previously evaluated for Blastocystis infection. Mammals having different niches and geographical distribution were infected with similar genetic type of Blastocystis, so that we suggest that local water or food sources could play an important role in Blastocystis transmission and ST maintenance in wild animals. Additionally, there are STs with scarce genetic variation, suggesting that they could be highly adapted to their hosts. These data contribute to our understanding of the host range and genetic diversity of Blastocystis.

Biological characteristics of Meccus phyllosomus pallidipennis (Hemiptera: Reduviidae: Triatominae) fed on two different hosts.

INTRODUCTION: Different blood meal sources can affect biology of triatomines. METHODS: We studied the influence of two different blood meal sources (rabbits and hens) on five biological parameters in Meccus phyllosomus pallidipennis and collected biological parameters. RESULTS: The cohort fed on rabbits had a shorter median life-cycle and lower mortality rate than that fed on hens. Both cohorts required a similar number of blood meals to reach adulthood. Median longevity and number of blood meals for adults were similar between both cohorts. CONCLUSIONS: The studied parameters reflect the high grade of adaptation of M. p. pallidipennis feeding on different hosts.

Biological characteristics of Meccus phyllosomus pallidipennis (Hemiptera: Reduviidae: Triatominae) fed on two different hosts

Abstract INTRODUCTION: Different blood meal sources can affect biology of triatomines. METHODS: We studied the influence of two different blood meal sources (rabbits and hens) on five biological parameters in Meccus phyllosomus pallidipennis and collected biological parameters. RESULTS: The cohort fed on rabbits had a shorter median life-cycle and lower mortality rate than that fed on hens. Both cohorts required a similar number of blood meals to reach adulthood. Median longevity and number of blood meals for adults were similar between both cohorts. CONCLUSIONS The studied parameters reflect the high grade of adaptation of M. p. pallidipennis feeding on different hosts.

Life history of two abundant populations of Dipetalogaster maximus (Uhler, 1894) (Hemiptera: Reduviidae: Triatominae) in northwestern Mexico.

We focused on the analysis of biological parameters of two different abundant populations of Dipetalogaster maximus (Uhler) (Hemiptera: Reduviidae: Triatominae) from northwestern Mexico. The biological parameters were related to hatching of eggs, life cycle, and meal needed for molting by each instar of two populations from environmentally similar areas (El Fandango and San Dionisio) with a similar number of available hosts as blood meal sources. The D. maximus populations from the two locations were evaluated and compared. No significant differences (P>0.05) were recorded for the average hatching time of the two cohorts. The median egg-to-adult development time and the number of blood meals at each nymphal group were significantly shorter (P<0.05) for the El Fandango cohort. The number of obtained females at the end of the cycles, number of eggs laid, and rate of egg hatching were significantly higher (P<0.05) for the El Fandango cohort. These results contribute to the estimation of abundances of the studied populations of D. maximus in areas where many tourists go for camping and have an increased risk of being bitten and infected by this species.

Biology of the introduced species Triatoma lecticularia (Hemiptera: Reduviidae) to northwestern Mexico, under laboratory conditions.

The first record of Triatoma lecticularia out of its reported distribution area together with the brief description of the said area is provided in this paper. In addition, some biological parameters related to hatching of eggs, life cycle and feeding and defecation behaviors for each instar of one population of T. lecticularia from its previously reported distribution area (PR) and for each instar of that introduced recently found population (IS) of this species were evaluated and compared. Twenty-eight specimens were collected from IS, mostly (64.29%) from peridomestic areas (mainly chicken coops). No significant (p>0.05) differences were recorded between the two studied cohorts in their average time to hatch, which was close to 19days. The median egg-to-adult development time, the number of blood meals at each nymphal, the instar mortality rates and median time-lapse for beginning of feeding were significantly (p<0.05) shorter for the IS cohort. Median feeding time was higher in PR. Defecation delay was shorter than 10min in both studied cohorts. Given these results, the introduced recently found population of T. lecticularia could be considered an important potential vector of Trypanosoma cruzi to human populations and could replace main triatomine species on its new distribution area.