Search USGS⌕ Search
Home/Archive/USGS

USGS · 70159815

Mapping physiological suitability limits for malaria in Africa under climate change

Sadie J. Ryan·Amy McNally·Leah R. Johnson·Erin A. Mordecai·Tal Ben-Horin·Krijn P. Paaijmans·Kevin D. Lafferty
View original source ↗Export metadata ↓

Abstract

We mapped current and future temperature suitability for malaria transmission in Africa using a published model that incorporates nonlinear physiological responses to temperature of the mosquito vector Anopheles gambiae and the malaria parasite Plasmodium falciparum . We found that a larger area of Africa currently experiences the ideal temperature for transmission than previously supposed. Under future climate projections, we predicted a modest increase in the overall area suitable for malaria transmission, but a net decrease in the most suitable area. Combined with human population density projections, our maps suggest that areas with temperatures suitable for year-round, highest-risk transmission will shift from coastal West Africa to the Albertine Rift between the Democratic Republic of Congo and Uganda, whereas areas with seasonal transmission suitability will shift toward sub-Saharan coastal areas. Mapping temperature suitability places important bounds on malaria transmissibility and, along with local level demographic, socioeconomic, and ecological factors, can indicate where resources may be best spent on malaria control.

Explore related subjects

Vector-Borne and Zoonotic DiseasesArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: -35.17380831799957° to 37.85750715625203° latitude; -20.56640625° to 52.64648437499999° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Sadie J. Ryan, Amy McNally, Leah R. Johnson, Erin A. Mordecai, Tal Ben-Horin, Krijn P. Paaijmans, Kevin D. Lafferty. 2015. Mapping physiological suitability limits for malaria in Africa under climate change. https://doi.org/10.1089/vbz.2015.1822

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2021

Epizootic plague in prairie dogs: Correlates and control with deltamethrin

The plague bacterium, Yersinia pestis , is a generalist pathogen of flea (Siphonaptera) vectors and mammalian hosts. In colonies of prairie dogs (PDs, Cynomys spp.), Y. pestis causes occasional epizootics, killing ≥90% of PDs within weeks to several months. We evaluated the effectiveness of deltamethrin, a pyrethroid insecticide, as a tool for preventing plague epizootics among three PD species. Specifically, we studied PD population growth on paired plots treated with deltamethrin for flea control or left untreated as baselines. We also evaluated PD population growth relative to flea abundance and PD density. All epizootics occurred on nontreated plots. Epizootics occurred on plots with very low PD densities as well as high densities. Mean population change, assessed by comparing visual counts of PDs in years before and during epizootics, was +88% for treated plots and −97% for nontreated plots. For comparison, an experimental oral vaccine against plague had an average change in population index or estimate during epizootics of −69% on vaccine plots compared with −83% for associated nontreated (placebo) plots. In our study and on plots not treated with deltamethrin, PD population growth was negatively correlated with flea abundance in the year before the epizootic, lending support to the hypothesis that flea abundance plays a critical role in plague transmission under natural conditions. Generally speaking, deltamethrin is a highly effective tool for plague management on PD colonies. That said, continued study is needed to refine deltamethrin treatments and to develop a more integrated strategy for plague management.

Vector-Borne and Zoonotic Diseases↗
USGS2021

Borreliosis transmission from ticks to humans associated with desert tortoise burrows: Examples of tick-borne relapsing fever in the Mojave Desert

Ticks transmit pathogens and parasitize wildlife in turn causing zoonotic diseases in many ecosystems. Argasid ticks, such as Ornithodoros spp., harbor and transmit Borrelia spp., resulting in tick-borne relapsing fever (TBRF) in people. In the western United States, TBRF is typically associated with the bite of an infected Ornithodoros hermsi tick found in habitats at high elevations (>1500 ft). This report describes the first TBRF cases in people in the Mojave Desert (Clark County, NV). Individuals documented in these case studies were exposed to Ornithodoros ticks during excavation of soil burrows associated with Mojave Desert tortoises ( Gopherus agassizii ), with bacteria from one of the human case's blood sample genetically matching to Borrelia turicatae as determined by quantitative PCR and sequencing. Our findings should serve as a precaution to individuals working with tortoises or animal burrows, or those in contact with Ornithodoros ticks in this region.

California, Nevada↗
USGS2021

Comparison of flea sampling methods and Yersinia pestis detection on prairie dog colonies

Scientists collect fleas (Siphonaptera) to survey for Yersinia pestis , the bacterial agent of plague. When studying fleas parasitizing prairie dogs ( Cynomys spp.), two primary methods are used: (1) combing fleas from live-trapped prairie dogs and (2) swabbing fleas from burrows with cloth swabs attached to metal cables. Ideally, burrow swabbing, the cheaper and easier method, would explain flea burdens on prairie dogs and provide reliable information on plague prevalence. In a linear regression analysis of data from 1-month intervals (June–August 2010–2011) on 13 colonies of black-tailed prairie dogs ( Cynomys ludovicianus , BTPDs) in New Mexico, flea abundance on swabs explained 0–26% of variation in BTPD flea burdens. In an analysis of data (May–August 2016) from six colonies of BTPDs in Montana, flea abundance on swabs explained 2% of variation in BTPD flea burdens. In an analysis of data from a short-term interval (July 23–27, 2019) on four colonies of BTPDs in Montana, flea abundance on swabs explained 0.1% of variation in BTPD flea burdens. In an analysis of data from 1-week intervals (August–October 2000) on four colonies of white-tailed prairie dogs ( Cynomys leucurus , WTPD) in Utah, swabbing data explained 0.1% of variation in WTPD flea burdens. Pools of fleas from two WTPD colonies were tested for Y. pestis by mouse inoculation and isolation; 65% from WTPDs tested positive, whereas 4% from burrows tested positive. Data herein also show that results from burrow swabbing can misrepresent flea species composition and phenology on prairie dogs. Burrow swabbing is useful for some purposes, but limitations should be acknowledged, and accumulated data should be interpreted with caution.

Montana, New Mexico, Utah↗