In an era where life expectancy has dramatically increased and modern medicine enables people in developed countries to live well into their eighties and nineties, problems that affect the extreme poor in developing countries are often overlooked. Tungiasis, or infestation by the Chigoe flea, is one such disfiguring and debilitating condition. While people rarely die directly from an infestation, it is common for the affected to suffer from gangrene to the extent that toes and other appendages are lost, and many people are unable to walk due to the pain associated with a superinfection of T. penetrans. The Chigoe flea affects the quality of life for hundreds of millions of people worldwide but has barely been discussed in mainstream media. Organizations such as the Bill and Melinda Gates Foundation and the Carter Center have made great strides in the fight to eradicate diseases that affect quality of life for the world’s extreme poor. For example, the Carter Center has made enormous advances in the past thirty years in eradication of the Guinea Worm, Dracunculus medinesis, from affected regions (Callahan et al. 2013). In fact, as of January 2015, only 126 cases of Guinea worm remain before the parasite disappears from humans entirely (St. Fleur 2015). One of the advantages of attacking these diseases in the modern era has been the efficacy of using GIS as a tool to map the prevalence and treatment efforts of these and other groups (Royal 2013, Royal 2014). Not only do the maps present data visually, the power of the geodatabase is in collecting and linking related data for queries and analysis.
The Chigoe flea Tunga penetrans is a parasitic insect of the order Siphonaptera. Known also as the jigger, the sand flea, the nigua, and bicho de pé, the Chigoe flea is a hematophagic insect and parasitizes multiple species of mammal including humans. It is the smallest member of the flea family at less than 1mm in total length and can only jump about 20cm so most often affects the feet or other skin exposed to soil or sand containing adult fleas. Both sexes require blood meals as adults, but it is the gravid female flea that burrows into the epidermis of its host for nourishment and protection, its abdomen expanding by a factor of 2000 over the next 4 to 6 weeks as it produces hundreds of eggs. The presence of the flea causes the epidermis to becomes irritated, prompting the immune system to release histamines causing inflammation and hardening of the skin. Over time, this squamation accumulates over the embedded fleas, providing ideal conditions for superinfestation. The flea is soon encapsulated in the host’s skin—this stage of ectoparasitic infestation is known as Tungiasis (Heukelbach 2005).
Three to six days after penetration, the swollen abdomen is visible as a white, pea-sized nodule. A dark cone-shaped structure in the middle of the lesion is the flea’s exposed rear end, allowing the embedded parasite to breathe, copulate, defecate, and expel eggs. The flea’s eggs look like grains of white sand and emerge around twenty-one days after initial penetration of the epidermis. After discharging her eggs, the female dies. In a singular infection, the flea is sloughed from the epidermis through tissue repair mechanisms, but in the case of superinfections fleas decompose within the host’s skin (Heukelbach et al. 2005). Intraepithelial abscesses form as the flea and its feces decompose—secondary infections by bacteria such as Staphylococcus sp., Bacillus sp., Streptococcus sp. and Clostridium sp. are well documented and tetanus is a real threat for the unvaccinated (Feldmeier et al. 2002). Infestation is painful and disfiguring; if allowed to continue unchecked, a heavy Chigoe flea infestation can lead to gangrene, loss of appendages, and even death. Unsanitary methods of removing purulent material and flea remains with dirty needles or razor blades may also lead to transmission of blood-borne pathogens such as hepatitis B and C virus and HIV (Feldmeier et al. 2013).
Many critical risk factors associated with T. penetrans infestation are geographic in nature or cyclic in chronon and are uniquely fit for display in a GIS (Ugbomoiko et al. 2007). Land cover, land use, temperature, humidity, rainfall and soil moisture play integral roles in the prevalence of Chigoe flea infestations. Social risk factors such as poverty, literacy, alcoholism, education, sustainable access to water, sanitation and hygiene (WASH), access to medical treatment, housing conditions, population density, and proximity to livestock can also be displayed visually within a GISystem and overlaid to best identify likely hotspots of infestation that can then be targeted for treatment. Pervasiveness of dirt floors and cohabitation with livestock are key in contributing to the perpetuation of infestations, as are lack of shoes, water for washing, and health education (Muehlen et al. 2006). One study in rural Kenya found the following four factors to be associated with tungiasis: living in houses with earthen floors, walking barefooted, having a common resting place outside the house, and presence of rats on the compound (Njau et al. 2012). For unknown reasons, children and elderly people are at greatest risk for superinfestation of T. penetrans (Heukelbach 2005, Feldmeier et al. 2002).i,ii Afflicted children are likely to stop attending school due to painful lesions, insomnia from itching, and fear of persecution and ostracism (Njau et al. 2012, Heukelbach 2005, Feldmeier et al. 2002, Feldmeier et al 2014). According to the 2014 National Policy Guidelines on Prevention and Control of Jigger Infestations, distributed by the Division of Environmental Health in Kenya, 1.4 million Kenyans, or approximately 4% of the total population, suffer from jigger infestation. The total population at risk—10 million—are the very young, elderly, or physically and/or developmentally disabled. Overall, the correlation between poverty and tungiasis is so strong that some argue that tungiasis actually perpetuates poverty.
Recording the distribution of supplies and implementation of treatment methods in a geodatabase format permits spatial and statistical analysis upon the collected data, revealing successes and failures in approach. While surgical removal is necessary for those already afflicted, preventative measures are becoming more widespread and cost-effective. Recent studies in Brazil show promise in the twice-daily application of dimethicone to affected parts of the body, effectively suffocating the fleas, while in Madagascar a four-week course of twice-daily application of the plant-based repellant Zanzarin® was shown to reverse tungiasis-associated clinical pathology almost completely (Thielecke et al. 2013, Feldmeier 2006). Another Brazilian study focuses on preemptive veterinary care of other reservoir animals such as dogs (Klimpel et al. 2005). Neem oil, aloe vera, and coconut oil have been shown to be effective repellants as well. Development of tactical distribution of inexpensive antiparasitic treatments, including petroleum jelly, dimethicone, potassium permanganate (KMnO4), and Zanzarin® enable the afflicted to be proactive in their own care.
The Kenyan Ministry of Health suggests the pouring of concrete or plaster to cover exposed dirt floors, and stresses regular cleaning with water to prevent reinfestation.v Equally important is eliminating uncontrolled disposal of human waste, another aspect of vector control for which GIS is uniquely qualified. Recording the location and incidence of pesticide application is a money-saving enterprise in addition to preventing the toxic buildup of pesticides over time. In terms of distribution of humanitarian aid, the provision of closed-toe shoes, clothing, and clean surgical instruments are vital in preventing infestation and secondary infection. Educating residents concerning the causes, cures, and prevention of future infestations is key to helping people help themselves. Teaching water-free methods of personal hygiene in areas where access to fresh water is limited in conjunction with aforementioned topical treatment may be the best option for some afflicted communities. In many communities, the burden of preventative care falls on the women of the community (Winter et al. 2009). In educating these caregivers, the burden on volunteer groups is lessened.
While many charitable organizations provide medical and social services to affected populations, there has been little success in the coordination of efforts between government and nonprofit entities, although a dire need has been documented (Heukelbach 2005, Karunamoorthi 2013, Lefebrve et al. 2011).i,ii Through the use of a targeted GISystem, nonprofit organizations and local and national governments can begin to coordinate efforts for the permanent eradication of the Chigoe flea. Thus, optimal and timely coverage of Kenya’s vast rural areas can be achieved with minimal overlap of resources. Route planning is an inbuilt role of GIS, so the development of more efficient routes and schedules for treatment may be designed.
More than forty charitable organizations already exist to combat the blight of the Chigoe flea in Kenya, a primarily English-speaking country (Feldmeier et al. 2013).vi,vii, Many of these organizations already collect data in order to most wisely divide volunteer time between afflicted areas; appropriating this volunteered geographic information (VGI) for integration into a GISystem would require little change from current organizational practices. Smartphones and cameras, even when not tied to wireless cell networks, contain onboard GPS receivers that can track positional data with an acceptable accuracy and precision relative to the scale of the operation. A geodatabase of the region in which volunteer organizations’ coverage areas can be continuously updated with VGI—such as demographic information, severity of infestation, and dates of treatment—will accommodate the sharing of information for a higher purpose.
Parasitic insects have long been a nuisance and/or threat to humans. Developing a strategic GIS for the identification of infestation and creation of a treatment plan—be it the use of pesticides, distribution of medicines or prophylactics, or scheduling of medical visits—will be essential for combatting the scourge of human ectoparasites that act as disease vectors in densely populated areas. As childhood mortality falls survive due to better nutrition and medical treatment, the concentration of humans within urban areas will continue to rise exponentially. A geographic information science approach to the control of parasites and/or introduced and invasive species has many applications as we continue on the path of becoming a global society. Just as invasive plants, reptiles, and mammals colonize new lands through unintentional introduction, so do pests and parasites. Epidermal parasitic skin diseases (EPSD) occur worldwide but have been widely neglected by the scientific community (Feldmeier et al. 2009). These pests cost us both economically and socially, supporting the need to explore new, effective management strategies for their control and removal. The potential for future use of this model in managing pests that negatively impact human life is wide-ranging in the management and eradication of many economically destructive and disease-propagating pests:
World Health Organization
Wikipedia article about Tropical Diseases
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