Moreover, farm workers may be more susceptible to extreme heat illness due to risk factors such as low-income, male gender, migration status, type of work at the farm, and pre-existing illness, including potentially related cardiovascular disease, kidney disease, and diabetes . These negative impacts of heat on agricultural workers are significant and continue to increase due to a warming climate and growing demand for agricultural labor in fertile agricultural areas of the U.S., particularly during the harvesting months, which coincide with the most extreme conditions. Research shows that the physical work capacity of an agricultural laborer lowers as the air temperature, humidity, and sunlight increase . Thus, as more agricultural laborers are hired to compensate for lost work productivity, a greater number of vulnerable outdoor workers are negatively impacted by heat and require essential coping resources .Despite a burgeoning literature on COVID-19, more research is needed to address the burden of COVID-19 in concert with anomalous heat, labor productivity, and laborers’ health and livelihoods. We discussed potential pathways of how heat can impact COVID-19 morbidity and mortality and vice versa. We argue that this twin burden further impacts labor productivity and farm worker livelihoods in an insidious cycle, exceeding the sum of each illness independently. More research integrating the two topics is warranted. Many largely unanswered questions remain to be examined by researchers. For example, under what circumstances does COVID-19 lead to increased heat health challenges? Specifically, to what extent does mask-wearing, social distancing,vertial sliding shelves and individualized water consumption lead to COVID- 19 heat stress? To what degree may there be a connection between long-haul COVID and heat susceptibility and associated consequences in labor productivity? What other factors may impact heat health challenges?
More research is needed also to address the impacts of heat stress on COVID-19 morbidity and mortality. For example, to what extent does heat stress induced immunodeficiency facilitate COVID-19 infection? To what extent is heat stress likely to reduce mask wearing and therefore increase COVID-19 infection rates? To what degree does extreme heat lead to increased use of air-conditioning, subsequent concentration of aerosols in an enclosed space and ultimately, to potentially increased COVID-19 prevalence? What other heat-related health factors might exacerbate COVID-19 morbidity and mortality? The dearth of data on these topics calls for new empirical field research combining surveys and interviews with climatological data. Beyond the knowledge gap and opportunity for researchers on the topic, direct policy implications result from this dual burden. The similarity of socio-economic and labor impacts of COVID-19 and heat stress, allows policymakers to design and implement policies for both with a broader impact on farm workers’ well being. For example, unemployment benefits, if implemented for farm workers, can have a broader positive impact on the target population as they recover from either or both health conditions. Consideration of the expansion of worksite policies such as expanding paid sick leave for impacted workers could also be useful. Lessons learned from implementing policies related to heat stress may provide guidance for policies related to COVID-19. Therefore, public health policies and workplace, acclimatization protocols can be informed in ways that ameliorate suffering from both COVID-19 and cognate infectious diseases as well as heat stress. These strategies must be place-based to assess and lessen both burdens as they intersect with outdoor labor conditions, farm worker related health needs, and cultural aspects of policy implementation and farm worker outreach. Intervention points or policy levers can be leveraged suitably. For example, the timing of worksite vaccination campaigns can be planned to coincide with workplace heat prevention acclimatization protocols, raising awareness among workers and employers about the dangers of both stressors.
Understanding the intersection of COVID-19 and climate change via heat stress results in an opportunity for policy makers to design and implement policies that may have greater impact when addressing the health and socio-economic impacts of both occurrences.Malaria remains one of the most serious vector-borne diseases, affecting hundreds of millions of people mainly in the sub-Saharan Africa including Ethiopia. Yet unprecedented success has been achieved over the past two decades in reducing the disease burden, averting an estimated 663 million malaria cases in Africa between 2001 and 2015 . Vector control is one of the key elements in achieving the remarkable reduction in malaria, with long-lasting insecticidal nets and indoor residual spraying estimated to have averted 68% and 10% of the cases, respectively . Similarly, morbidity and mortality due to malaria has remarkably declined in Ethiopia over the past decade as a result of large-scale distribution of LLINs and high coverage of IRS, together with nationwide implementation of artemisin in-based combination therapy . Based these gains, the country has set goals to eliminate malaria by 2030 and the elimination program is being implemented in 239 selected low malaria transmission districts encompassing six different regions . More than 11 million LLINs have been distributed through mass campaigns in 2018 alone to further reduce malaria cases and accelerate the progress towards elimination . However, malaria transmission continues to occur and still remains a significant public health problem in Ethiopia despite the progress made in scaling up of the control measures . This transmission could be attributed to several factors including the spread of insecticide resistance and preference of malaria vectors to bite outdoors and in the early evening when people are indoors but unprotected by existing tools . The current indoor-based malaria vector control interventions such as LLINs offer protection from anthropophagic and endophagic vectors, but have little impact on vector species predominantly feeding on animals and humans outdoors . In Ethiopia, the primary vector of malaria is An. arabiensis.
This vector species has a peculiar feature in that it can readily feed on humans to sustain intense malaria transmission , but often enough on animals to evade the effect of LLINs and IRS, and to maintain residual malaria transmission . Such dual feeding preference of An. arabiensis could pose another challenge to malaria control and elimination efforts as malaria transmission may continue even with a high coverage of the current vector control interventions . Moreover,vertical farming supplies the feeding behavior of An. arabiensis could vary in different eco-epidemiological settings depending on several factors including host availability and the genetic structure of the vector itself . In addition to the vector behavior, human habits and sleeping patterns could also be vital determinants of malaria transmission since exposure to malaria vector bites occurs when unprotected people and vector biting activities overlap in time and space . Addressing the challenge of residual malaria transmission on malaria elimination efforts requires better understanding of both the local vector and human behavior. Moreover, quantifying the magnitude of human exposure to infectious mosquito bites which occurs indoors and outdoors is crucial to evaluate the likely success of the current vector control measures . However, most vector surveillance activities in Ethiopia focused mainly on vector behavior with less or no attention to human behavior that also contributes to residual malaria transmission. The aim of this study was to assess vector behavior, patterns of human exposure to mosquito bites and residual malaria transmission in southwestern Ethiopia. The study was carried out in Bulbul kebele , which is located in Kersa district, Jimma Zone 320 km southwest of the capital, Addis Ababa . The inhabitants mostly rely on subsistence farming, with maize and teff being the main cultivated crops in the area. Most houses are mud-walled with roofs made of corrugated iron sheets. Malaria transmission is seasonal in Bulbul area. The transmission peaks from September to October, following the major rains from June to September. Minor transmission occurs in April and May, following the short rains of February to March. Plasmodium falciparum and Plasmodium vivax are the two predominant malaria parasite species co-occurring in the area and are transmitted mainly by An. arabiensis .Adult mosquito collections were carried out monthly from January to December 2018. Host-seeking mosquitoes were collected both indoors and outdoors using human landing catches , Centers for Disease Control and Prevention miniature light traps and human-baited double net traps . Indoor resting mosquitoes were collected using pyrethrum spray catches .For each house, two collectors seated on stools with their legs exposed from foot to knee to capture mosquitoes as soon as they land on the exposed legs before they commence blood-feeding using a flashlight and mouth aspirator .
There were two collection shifts: one team worked from 18:00 to 24:00 hr during each collection night, followed by the second team from 24:00 to 06:00 hr. Each hour’s collection was kept separately in labeled paper cups. A supervisor was assigned to coordinate the collection activities and watch volunteers not to fall asleep during the collection nights. All collectors were provided with anti-malarial prophylaxis to avoid a risk of contracting malaria during the collection period. Mosquitoes were identified to species the next morning. The CDC light traps were set indoors beside human-occupied bed nets in other four randomly selected houses monthly and paired with outdoor HDNT. Details of the HDNT are described elsewhere . Both traps were set from 18:00 to 6:00 hr during each collection night. The PSC was conducted monthly in twenty randomly selected houses from 06:00 to 09:00 hr following standard protocol . All collected mosquitoes were identified morphologically to species or species complexes using a dichotomous key described by Gillies and De Meillon . Female Anopheles mosquitoes were further classified as unfed, freshly fed, half-gravid and gravid. Each mosquito was kept individually in a labeled 1.5 ml Eppendorf tube containing silica gel desiccant. Samples were stored at −20°C freezer at Jimma University Tropical and Infectious Diseases Research Center Laboratory until used for further processing.This study indicated that An. pharoensis was the most abundant anopheline species in the study area followed by An. arabiensis and An. coustani. Previous studies reported that An. arabiensis was the predominant species in different malaria endemic settings of southwestern Ethiopia . The higher abundance of An. pharoensis over An. arabiensis in this study could be attributed to difference in mosquito breeding habitats. The present study area is located in the Omo-Gibe River Basin with abundant aquatic vegetations that might have favoured An. pharoensis. Anopheles pharoensis prefers to breed in vegetated swamps unlike An. arabiensis which typically breeds in small, sunlit temporary water pools . Anopheles arabiensis exhibited exophagic behavior, seeking hosts mostly outdoors rather than indoors. Similar findings were also reported from different parts of Ethiopia . Anopheles arabiensis was shown to be preponderantly exophagic even before the scale up of indoor based vector control interventions in Ethiopia , suggesting that the exophagic behavior of this species might be genetically determined . Moreover, the long-term use of the current vector control interventions might have further enhanced the proportion of outdoor biting fraction of An. arabiensis as observed elsewhere in Africa. For instance in western Kenya, An. arabiensis was more likely to bite outdoors when compared with data collected before the scale-up of LLINs . Likewise, An. pharoensis showed exophagic behavior in the study area. Similar findings were also reported for this species from different parts of Ethiopia . In the absence of personal protection by LLINs, human exposure to An. arabiensis bites occurred mostly indoors despite the outdoor host-seeking preference of this species. This is due to coincidence of humans and the peak biting activities of An. arabiensis since most people spend their time indoors when this species is mostly active . A similar phenomenon was documented for other malaria vector species in Africa . For instance, An. funestus and An. quadriannulatus did not show preference to bite indoors in Zambia, yet a substantial proportion of human contact with both species was shown to occur indoors in the absence of LLIN use in the country . This highlights the need to consider human behavior to determine the actual magnitude of human exposure to mosquito bites which may occur indoors and/or outdoors. For LLIN non-users, 56% of human exposure to An. arabiensis bites occurred at times when using LLINs is feasible, indicating that the maximum possible personal protection that could be provided by LLIN is 56%.