Search

The impact of climate change on humans is ever greater, ironically because of anthropogenic factors such as globalization. In the case of vectorborne diseases as leishmaniases, the climate change (CC) can affect their epidemiology by shifting the biology and ecology of its vectors, reservoirs and pathogens. In this descriptive review, a search was made in BioMed Central, PubMed and Biblioteca virtual em saúde and aims to provide information available about the effect of CC on incidence and seasonal and spatial distribution of the leishmaniases, the pathogen and its vectors, and how it can impact the emergence and resurgence of this disease in Latin American countries, highlighting the problem in Mexico. Information generated from 2002 to 2021 was collected from scientific data bases. We found 48 articles, including six review articles. The great potential of leishmaniasis to expand its geographic distribution ranges, variation of its transmission cycles, substantial increase in the number of cases and increase in the investment for the exploration of alternatives of its treatment and control, this has caused that leishmaniasis leave the “neglected diseases” status and be re-categorized as “emerging diseases”., El impacto del cambio climático en los humanos es cada vez mayor, irónicamente debido a factores antropogénicos como la globalización. En el caso de enfermedades transmitidas por vectores como las leishmaniasis, el cambio climático (CC) puede afectar su epidemiología al modificar la biología y ecología de sus vectores, reservorios y patógenos. En esta revisión descriptiva, se realizó una búsqueda de información en BioMed Central, PubMed y Biblioteca virtual em saúde y se tuvo como objetivo proporcionar información disponible sobre el efecto del CC en la incidencia y distribución estacional y espacial de la leishmaniasis, el patógeno y sus vectores, y cómo puede impactar en la aparición y resurgimiento de esta enfermedad en los países de América Latina, destacando la problemática en México. Se buscó información de 2002 a 2021, en bases de datos de artículos científicos. Se encontraron 48 referencias, incluyendo seis artículos de revisión. El gran potencial de las eishmaniasis para ampliar sus rangos de distribución geográfica, la variación de sus ciclos de transmisión, el aumento sustancial del número de casos y el aumento de la inversión para la exploración de alternativas de su tratamiento y control, ha provocado que las leishmaniasis sean categorizadas como enfermedades emergentes.

Phlebotomine sandflies are the vectors of different species of the genus Leishmania, which are the aethiological agents of the varied clinical forms of the leishmaniases. The main risk factor for transmission to humans is the contact with vectors, so the activities of vector incrimination and understanding of vectorial capacities are very important aspects in the epidemiology of disease. Therefore, it is very relevant to be able to estimate with precision the presence, abundance, biting-rate, infection-rate, age-structure, etc., to evaluate the risk for transmission of Leishmania spp. and that gathered information could be analyzed and comprehended for those decision-making personnel in relation to public health policies. However, in order for that field information to be useful to the health sector or research proposes, the population estimates would be unbiassed in relation to the captures of species of medical importance or the biological assemblage. The main objective of the present contribution is to present a descriptive review of the most common sampling and monitoring methods for phlebotomine sandflies based on published papers, highlighting field studies conducted in Mexico and discussing each sampling method for advantages and disadvantages as well as interpretations. Lastly, the general aspects of sampling and population inference are discussed, and future research perspectives are mentioned., Los flebotominos son los vectores de diferentes especies de parásitos del género Leishmania, los cuales son los agentes etiológicos de variadas formas clínicas de las leishmaniasis. El principal riesgo de transmisión a humanos es el contacto con los vectores portadores del parásito, por lo que la actividad de incriminación de vectores y el entendimiento de las capacidades vectoriales de las especies son aspectos muy importantes desde el punto de vista epidemiológico. Entonces, es de suma relevancia estimar con precisión la presencia, abundancia, tasa de picadura, tasa de infección, estructura de edades, entre otras. para evaluar los riesgos de transmisión de Leishmania spp. y que la información generada pueda ser analizada y comprendida por los tomadores de decisiones en cuanto a políticas públicas de salud. Sin embargo, para que esta información de campo sea realmente útil al sector salud o para fines de investigación, los estimadores poblacionales deben tener un mínimo de sesgo con relación a las capturas de las especies de importancia médica o bien del ensamble biológico. El principal objetivo de la presente contribución es presentar una revisión descriptiva basada en la literatura publicada sobre los métodos más comúnmente empleados en la captura y monitoreo de flebotominos, haciendo énfasis en los estudios realizados en México y con discusiones acerca de cada método en cuanto ventajas, desventajas e interpretaciones. Así como, los aspectos generales del muestreo e inferencias poblaciones, con mención de las perspectivas futuras de investigación.

– Leishmaniases are a group of important diseases transmitted to humans through the bite of sandfly vectors. Several forms of leishmaniases are endemic in Mexico and especially in the Southeast region. In the Northeastern region, however, there have only been isolated reports of cases and scanty records of sandfly vectors. The main objective of this study was to analyze the diversity of sandflies and potential reservoir hosts of Leishmania spp. in the states of Nuevo León and Tamaulipas. Species richness and abundances of sandflies and rodents were recorded. A fraction of the caught sandflies was analyzed by PCR to detect Leishmania spp. Tissues from captured rodents were also screened for infection. Ecological Niche Models (ENMs) were computed for species of rodent and their association with crop-growing areas. We found 13 species of sandflies, several of which are first records for this region. Medically important species such as Lutzomyia anthophora, Lutzomyia diabolica, Lutzomyia cruciata, and Lutzomyia shannoni were documented. Leishmania spp. infection was not detected in sandflies. Nine species of rodents were recorded, and Leishmania (Leishmania) mexicana infection was found in four species of Peromyscus and Sigmodon. ENMs showed that potential distribution of rodent pest species overlaps with allocated crop areas. This shows that Leishmania (L.) mexicana infection is present in the Northeastern region of Mexico, and that previously unrecorded sandfly species occur in the same areas. These findings suggest a potential risk of transmission of Leishmania (L.) mexicana. Résumé – Écologie des phlébotomes et hôtes putatifs de la leishmaniose dans une zone frontalière du nord-est du Mexique : implications pour le risque de transmission de Leishmania mexicana au Mexique et aux États-Unis. Les leishmanioses sont un groupe de maladies importantes transmises aux humains par piqûre des phlébotomes vecteurs. Plusieurs formes de leishmanioses sont endémiques au

Leishmania (Leishmania) mexicana causes cutaneous leishmaniasis, an endemic zoonosis affecting a growing number of patients in the southeastern states of Mexico. Some foci are found in shade-grown cocoa and coffee plantations, or near perennial forests that provide rich breeding grounds for the sand fly vectors, but also harbor a variety of bat species that live off the abundant fruits provided by these shade-giving trees. The close proximity between sand flies and bats makes their interaction feasible, yet bats infected with Leishmania (L.) mexicana have not been reported. Here we analyzed 420 bats from six states of Mexico that had reported patients with leishmaniasis. Tissues of bats, including skin, heart, liver and/or spleen were screened by PCR for Leishmania (L.) mexicana DNA. We found that 41 bats (9.77%), belonging to 13 species, showed positive PCR results in various tissues. The infected tissues showed no evidence of macroscopic lesions. Of the infected bats, 12 species were frugivorous, insectivorous or nectarivorous, and only one species was sanguivorous (Desmodus rotundus), and most of them belonged to the family Phyllostomidae. The eco-region where most of the infected bats were caught is the Gulf Coastal Plain of Chiapas and Tabasco. Through experimental infections of two Tadarida brasiliensis bats in captivity, we show that this species can harbor viable, infective Leishmania (L.) mexicana parasites that are capable of infecting BALB/c mice. We conclude that various species of bats belonging to the family Phyllostomidae are possible reservoir hosts for Leishmania (L.) mexicana, if it can be shown that such bats are infective for the sand fly vector. Further studies are needed to determine how these bats become infected, how long the parasite remains viable inside these potential hosts and whether they are infective to sand flies to fully evaluate their impact on disease epidemiology.

Context and Objective: Chagas disease is considered a worldwide emerging disease; it is endemic in Mexico and the state of Coahuila and is considered of little relevance. The objective of this study was to determine the seroprevalence of T. cruzi infection in blood donors and Chagas cardiomyopathy in patients from the coal mining region of Coahuila, Mexico. Design and Setting: Epidemiological, exploratory and prospective study in a general hospital during the period January to June 2011. Methods: We performed laboratory tests ELISA and indirect hemagglutination in three groups of individuals: 1) asymptomatic voluntary blood donors, 2) patients hospitalized in the cardiology department and 3) patients with dilated cardiomyopathy. Results: There were three levels of seroprevalence: 0.31% in asymptomatic individuals, 1.25% in cardiac patients and in patients with dilated cardiomyopathy in 21.14%. Conclusions: In spite of having detected autochthonous cases of Chagas disease, its importance to local public health remains to be established as well as the details of the dynamics of transmission so that the study is still in progress.

The composition and seasonal occurrence of sandflies were investigated in coffee agroecosystems in the Soconusco region of Chiapas, Mexico. Insect sampling was performed on three plantations located at different altitudes: Finca Guadalupe Zajú [1,000 m above sea level (a.s.l.)], Finca Argovia (613 m a.s.l.) and Teotihuacán del Valle (429 m a.s.l.). Sandflies were sampled monthly from August 2007-July 2008 using three sampling methods: Shannon traps, CDC miniature light traps and Disney traps. Sampling was conducted for 3 h during three consecutive nights, beginning at sunset. A total of 4,387 sandflies were collected during the course of the study: 2,718 individuals in Finca Guadalupe Zajú, 605 in Finca Argovia and 1,064 in Teotihuacán del Valle. The Shannon traps captured 94.3% of the total sandflies, while the CDC light traps and Disney traps captured 4.9% and 0.8%, respectively. More females than males were collected at all sites. While the number of sandflies captured was positively correlated with temperature and relative humidity, a negative correlation was observed between sandfly numbers and rainfall. Five species of sandflies were captured: Lutzomyia cruciata, Lutzomyia texana, Lutzomyia ovallesi, Lutzomyia cratifer/ undulata and Brumptomyia sp. Lu. cruciata, constituting 98.8% of the total, was the most abundant species. None of the captured sandflies was infected with Leishmania spp.

Ecological niche models are useful tools to infer potential spatial and temporal distributions in vector species and to measure epidemiological risk for infectious diseases such as the Leishmaniases. The ecological niche of 28 North and Central American sand fly species, including those with epidemiological relevance, can be used to analyze the vector’s ecology and its association with transmission risk, and plan integrated regional vector surveillance and control programs. In this study, we model the environmental requirements of the principal North and Central American phlebotomine species and analyze three niche characteristics over future climate change scenarios: i) potential change in niche breadth, ii) direction and magnitude of niche centroid shifts, iii) shifts in elevation range. Niche identity between confirmed or incriminated Leishmania vector sand flies in Mexico, and human cases were analyzed. Niche models were constructed using sand fly occurrence datapoints from Canada, USA, Mexico, Guatemala and Belize. Nine non-correlated bioclimatic and four topographic data layers were used as niche components using GARP in OpenModeller. Both B2 and A2 climate change scenarios were used with two general circulation models for each scenario (CSIRO and HadCM3), for 2020, 2050 and 2080. There was an increase in niche breadth to 2080 in both scenarios for all species with the exception of Lutzomyia vexator. The principal direction of niche centroid displacement was to the northwest (64%), while the elevation range decreased greatest for tropical, and least for broad-range species. Lutzomyia cruciata is the only epidemiologically important species with high niche identity with that of Leishmania spp. in Mexico. Continued landscape modification in future climate change will provide an increased opportunity for the geographic expansion of NCA sand flys’ ENM and human exposure to vectors of Leishmaniases.

Ecological niche models are useful tools to infer potential spatial and temporal distributions in vector species and to measure epidemiological risk for infectious diseases such as the Leishmaniases. The ecological niche of 28 North and Central American sand fly species, including those with epidemiological relevance, can be used to analyze the vector’s ecology and its association with transmission risk, and plan integrated regional vector surveillance and control programs. In this study, we model the environmental requirements of the principal North and Central American phlebotomine species and analyze three niche characteristics over future climate change scenarios: i) potential change in niche breadth, ii) direction and magnitude of niche centroid shifts, iii) shifts in elevation range. Niche identity between confirmed or incriminated Leishmania vector sand flies in Mexico, and human cases were analyzed. Niche models were constructed using sand fly occurrence datapoints from Canada, USA, Mexico, Guatemala and Belize. Nine non-correlated bioclimatic and four topographic data layers were used as niche components using GARP in OpenModeller. Both B2 and A2 climate change scenarios were used with two general circulation models for each scenario (CSIRO and HadCM3), for 2020, 2050 and 2080. There was an increase in niche breadth to 2080 in both scenarios for all species with the exception of Lutzomyia vexator. The principal direction of niche centroid displacement was to the northwest (64%), while the elevation range decreased greatest for tropical, and least for broad-range species. Lutzomyia cruciata is the only epidemiologically important species with high niche identity with that of Leishmania spp. in Mexico. Continued landscape modification in future climate change will provide an increased opportunity for the geographic expansion of NCA sand flys’ ENM and human exposure to vectors of Leishmaniases.

Serology of West Nile virus vectors and non-human reservoirs was surveyed at Acapulco, Jose Azueta, and Ometepec, three Pacific Coast localities of Guerrero State, Mexico. The objectives of this study were to use enzyme-linked immnosorbent assay (ELISA) to assess West Nile virus antibodies of bird and equine serum samples and use reverse transcription of polymerase chain reaction (RT-PCR) to detect the virus in field-collected resting mosquitoes. Forty birds trapped using mist nets yielded 10% seroprevalence. Similarly, 18.6% of 102 equine blood samples had West Nile virus. In addition, 4,854 mosquitoes were caught using motorized backpack aspirators and grouped into 116 pools. Of the 16 species and seven genera, no mosquito was positive for West Nile virus. Our study demonstrated West Nile virus seroprevalence on resident birds and equines in Guerrero State, Mexico.

A trap made from low-cost materials and using an attractant of a yeast mixture producing carbon dioxide was designed and evaluated to collect adult Aedes aegypti (L.) mosquitoes. The Trap Mosquito Box prototype was tested against the “standards” BG-Sentinel traps and CDC backpack aspirator in the field. The mean numbers of mosquitoes (± standard deviation) caught by the three different collection methods were: Trap Mosquito Box 2.42 (± 3.08), BG-Sentinel trap 2.86 (± 3.71), and backpack aspirator 0.59 (± 0.90). Statistical tests showed the Trap Mosquito Box and BG-Sentinel trap were equally effective in collecting A. aegypti and both methods were significantly different than the backpack aspirator. Emission of carbon dioxide produced by the yeast mixture was greatest during the first hours after incubation in a laboratory and captured the most mosquitoes in the Trap Mosquito Box. Production of carbon dioxide [Y = -631.24 + 941.26 (log x)] and the rate of mosquitoes captured per time period [Y = 20.29 + 23.50 (log x)] were best explained by logarithmic regressions. Advantages and disadvantages of the Trap Mosquito Box for mosquito surveillance are discussed

A trap made from low-cost materials and using an attractant of a yeast mixture producing carbon dioxide was designed and evaluated to collect adult Aedes aegypti (L.) mosquitoes. The Trap Mosquito Box prototype was tested against the “standards” BG-Sentinel traps and CDC backpack aspirator in the field. The mean numbers of mosquitoes (± standard deviation) caught by the three different collection methods were: Trap Mosquito Box 2.42 (± 3.08), BG-Sentinel trap 2.86 (± 3.71), and backpack aspirator 0.59 (± 0.90). Statistical tests showed the Trap Mosquito Box and BG-Sentinel trap were equally effective in collecting A. aegypti and both methods were significantly different than the backpack aspirator. Emission of carbon dioxide produced by the yeast mixture was greatest during the first hours after incubation in a laboratory and captured the most mosquitoes in the Trap Mosquito Box. Production of carbon dioxide [Y = -631.24 + 941.26 (log x)] and the rate of mosquitoes captured per time period [Y = 20.29 + 23.50 (log x)] were best explained by logarithmic regressions. Advantages and disadvantages of the Trap Mosquito Box for mosquito surveillance are discussed.

Human bait catches were carried out from 5 through 27 March 1994 in an endemic focus of cutaneous leishmaniasis in the state of Campeche, Mexico. Females of Lutzomyia cruciata (Coquillet) were dissected and 67% were parous. The number of total and parous females collected per day was analyzed by time series, but neither the gonotrophic cycle length nor survivorship could be estimated. However, a survival rate per oviposition cycle of 0.68 was estimated from the least square regression of parous on total females. Additional evidence for L. cruciata as a vector of human leishmaniasis is discussed.

Sand flies were caught from December 1993 to November 1994 in an endemic focus of cutaneous leishmaniasis in the state of Campeche, Mexico. A total of 566 sand flies of seven species were collected using emergence funnel-traps, at openings of several mammal burrows. The main species collected were Lutzomyia deleoni and Brumptomyia hamata. Population abundance was found bimodal with the first and higher peak from January to March. A small second peak was found from May to October.