New Records of Anopheles benarrochi B (Diptera: Culicidae) in Malaria Hotspots in the Amazon Regions of Ecuador and Peru

Impact of climate and land use/land cover changes on malaria incidence in the Ecuadorian Amazon

Malaria transmission is influenced by climate and land use/land cover change (LULC). This study examines the impact of climate and LULC on malaria risk in the Ecuadorian Amazon. Weekly malaria surveillance data between 2008 and 2019 from Ecuador's Ministry of Public Health were combined with hydrometeorological and LULC data. Cross-correlation analyses identified time lags. Bayesian spatiotemporal models estimated annual LULC rates of change (ARC) by census area and assessed the effects on Plasmodium vivax and Plasmodium falciparum incidence. ARC for the five land cover classes (forest, agriculture, urban, shrub vegetation, water) ranged from -1 to 4% with agriculture increasing across areas. Forest and shrub vegetation ARC were significantly associated with both Plasmodium vivax and Plasmodium falciparum. Temperature and terrestrial water content showed consistent negative relationships with both species. Precipitation had varying effects on Plasmodium vivax (null) and Plasmodium falciparum (increase) incidence. Shrubs and forest expansion, increased temperature, and terrestrial water content reduced malaria incidence, while increased precipitation had varying effects. Relationships between malaria, LULC, and climate are complex, influencing risk profiles. These findings aid decision-making and guide further research in the region.

Effect of spatiotemporal variables on abundance, biting activity and parity of Nyssorhynchus darlingi (Diptera: Culicidae) in peri-Iquitos, Peru

BACKGROUND

In malaria endemic regions of the Peruvian Amazon, rainfall together with river level and breeding site availability drive fluctuating vector mosquito abundance and human malaria cases, leading to temporal heterogeneity. The main variables influencing spatial transmission include location of communities, mosquito behaviour, land use/land cover, and human ecology/behaviour. The main objective was to evaluate seasonal and microgeographic biting behaviour of the malaria vector Nyssorhynchus (or Anopheles) darlingi in Amazonian Peru and to investigate effects of seasonality on malaria transmission.

METHODS

We captured mosquitoes from 18:00 to 06:00 h using Human Landing Catch in two riverine (Lupuna, Santa Emilia) and two highway (El Triunfo, Nuevo Horizonte) communities indoors and outdoors from 8 houses per community, during the dry and rainy seasons from February 2016 to January 2017. We then estimated parity rate, daily survival and age of a portion of each collection of Ny. darlingi. All collected specimens of Ny. darlingi were tested for the presence of Plasmodium vivax or Plasmodium falciparum sporozoites using real-time PCR targeting the small subunit of the 18S rRNA.

RESULTS

Abundance of Ny. darlingi varied across village, season, and biting behaviour (indoor vs outdoor), and was highly significant between rainy and dry seasons (p < 0.0001). Biting patterns differed, although not significantly, and persisted regardless of season, with peaks in highway communities at ~ 20:00 h in contrast to biting throughout the night (i.e., 18:00-06:00) in riverine communities. Of 3721 Ny. darlingi tested for Plasmodium, 23 (0.62%) were infected. We detected Plasmodium-infected Ny. darlingi in both community types and most (20/23) were captured outdoors during the rainy season; 17/23 before midnight. Seventeen Ny. darlingi were infected with P. vivax, and 6 with P. falciparum. No infected Ny. darlingi were captured during the dry season. Significantly higher rates of parity were detected in Ny. darlingi during the rainy season (average 64.69%) versus the dry season (average 36.91%) and by community, Lupuna, a riverine village, had the highest proportion of parous to nulliparous females during the rainy season.

CONCLUSIONS

These data add a seasonal dimension to malaria transmission in peri-Iquitos, providing more evidence that, at least locally, the greatest risk of malaria transmission is outdoors during the rainy season mainly before midnight, irrespective of whether the community was located adjacent to the highway or along the river.

Natural Infection of Nyssorhynchus darlingi and Nyssorhynchus benarrochi B with Plasmodium during the Dry Season in the Understudied Low-Transmission Setting of Datem del Marañon Province, Amazonian Peru

The persistence of malaria hotspots in Datem del Marañon Province, Peru, prompted vector control units at the Ministry of Health, Loreto Department, to collaborate with the Amazonian International Center of Excellence for Malaria Research to identify the main vectors in several riverine villages that had annual parasite indices > 15 in 2018-2019. Anophelinae were collected indoors and outdoors for two 12-hour nights/community during the dry season in 2019 using human landing catch. We identified four species: Nyssorhynchus benarrochi B, Nyssorhynchus darlingi, Nyssorhynchus triannulatus, and Anopheles mattogrossensis. The most abundant, Ny. benarrochi B, accounted for 96.3% of the total (7,550/7,844), of which 61.5% were captured outdoors (4,641/7,550). Six mosquitoes, one Ny. benarrochi B and five Ny. darlingi, were infected by Plasmodium falciparum or Plasmodium vivax. Human biting rates ranged from 0.5 to 592.8 bites per person per hour for Ny. benarrochi B and from 0.5 to 32.0 for Ny. darlingi, with entomological inoculation rates as high as 0.50 infective bites per night for Ny. darlingi and 0.25 for Ny. benarrochi B. These data demonstrate the risk of malaria transmission by both species even during the dry season in villages in multiple watersheds in Datem del Marañon province.

Nondestructive Methods of Pathogen Detection: Importance of Mosquito Integrity in Studies of Disease Transmission and Control

Mosquitoes are vectors of many pathogens, including viruses, protozoans, and helminths, spreading these pathogens to humans as well as to wild and domestic animals. As the identification of species and the biological characterization of mosquito vectors are cornerstones for understanding patterns of disease transmission, and the design of control strategies, we conducted a literature review on the current use of noninvasive and nondestructive techniques for pathogen detection in mosquitoes, highlighting the importance of their taxonomic status and systematics, and some gaps in the knowledge of their vectorial capacity. Here, we summarized the alternative techniques for pathogen detection in mosquitoes based on both laboratory and field studies. Parasite infection and dissemination by mosquitoes can also be obtained via analyses of saliva- and excreta-based techniques or of the whole mosquito body, using a near-infrared spectrometry (NIRS) approach. Further research should be encouraged to seek strategies for detecting target pathogens while preserving mosquito morphology, especially in biodiversity hotspot regions, thus enabling the discovery of cryptic or new species, and the determination of more accurate taxonomic, parasitological, and epidemiological patterns.

Malaria Resilience in South America: Epidemiology, Vector Biology, and Immunology Insights from the Amazonian International Center of Excellence in Malaria Research Network in Peru and Brazil

The 1990s saw the rapid reemergence of malaria in Amazonia, where it remains an important public health priority in South America. The Amazonian International Center of Excellence in Malaria Research (ICEMR) was designed to take a multidisciplinary approach toward identifying novel malaria control and elimination strategies. Based on geographically and epidemiologically distinct sites in the Northeastern Peruvian and Western Brazilian Amazon regions, synergistic projects integrate malaria epidemiology, vector biology, and immunology. The Amazonian ICEMR's overarching goal is to understand how human behavior and other sociodemographic features of human reservoirs of transmission-predominantly asymptomatically parasitemic people-interact with the major Amazonian malaria vector, Nyssorhynchus (formerly Anopheles) darlingi, and with human immune responses to maintain malaria resilience and continued endemicity in a hypoendemic setting. Here, we will review Amazonian ICEMR's achievements on the synergies among malaria epidemiology, Plasmodium-vector interactions, and immune response, and how those provide a roadmap for further research, and, most importantly, point toward how to achieve malaria control and elimination in the Americas.

A Follow-Up to the Geographical Distribution of Anopheles Species in Malaria-Endemic and Non-Endemic Areas of Honduras

Simple Summary

Malaria is a tropical disease caused by parasites of the genus Plasmodium. The parasite is transmitted to humans through the bite of the female mosquito Anopheles. Honduras is close to the goal of eliminating malaria, but the region called La Moskitia continues to concentrate almost all of the country’s malaria cases. One of the key factors in achieving malaria elimination is a thorough understanding of the mosquito vectors that transmit the disease. There are few studies related to malaria vectors in Honduras. This study aims to contribute to knowing which are the species of vector mosquitoes, mainly in the Department of Gracias a Dios and in other departments in which cases of malaria occur, in addition to describing molecularly for the first time the anophelines of the Bay Islands. The most abundant species found here were Anopheles albimanus, but seven other species were also identified, some of which may contribute to parasite transmission.

Abstract

Anopheles species are the vectors of malaria, one of the diseases with the greatest impact on the health of the inhabitants of the tropics. Due to their epidemiological relevance and biological complexity, monitoring of anopheline populations in current and former malaria-endemic areas is critical for malaria risk assessment. Recent efforts have described the anopheline species present in the main malaria foci in Honduras. This study updates and expands knowledge about Anopheles species composition, geographical distribution, and genetic diversity in the continental territory of Honduras as in the Bay Islands. Outdoor insect collections were carried out at 25 sites in eight municipalities in five departments of Honduras between 2018 and 2021. Specimens were identified using taxonomic keys. Partial COI gene sequences were used for molecular species identification and phylogenetic analyses. In addition, detection of Plasmodium DNA was carried out in 255 female mosquitoes. Overall, 288 Anopheles mosquitoes were collected from 8 municipalities. Eight species were morphologically identified. Anopheles albimanus was the most abundant and widely distributed species (79.5%). A subset of 175 partial COI gene sequences from 8 species was obtained. Taxonomic identifications were confirmed via sequence analysis. Anopheles albimanus and An. apicimacula showed the highest haplotype diversity and nucleotide variation, respectively. Phylogenetic clustering was found for An. argyritarsis and An. neomaculipalpus when compared with mosquitoes from other Neotropical countries. Plasmodium DNA was not detected in any of the mosquitoes tested. This report builds upon recent records of the distribution and diversity of Anopheles species in malaria-endemic and non-endemic areas of Honduras. New COI sequences are reported for three anopheline species. This is also the first report of COI sequences of An. albimanus collected on the island of Roatán with apparent gene flow relative to mainland populations.