Fuentes 1 Colors of Doom: What does the tsetse fly see? Alexander Fuentes Stanford University Parks and People: Dilemmas of Protected Area Conservation in East Africa Sophomore College 2017 October 18, 2017 Fuentes 2 Introduction Tourists are often warned to beware exhibiting the colors of blue or black if traveling to the tsetse-infested areas of Sub-Saharan Africa, as these colors may summon the voracious species Glossina, also known as the tsetse fly. Amidst the animal kingdom, many tourists will notice the savannas are occasionally adorned with royal blue and black textiles. In fact, these “flags” are tsetse fly traps, decorated with the “colors of doom” that the tsetse fly is presumed to be most attracted to. Are these colors truly dangerous to display in Figure 1. A tsetse fly trap. the grasslands, or is this merely legend? Background Glossina prefer to dwell in bushes and during the dry season reside in shaded wooded areas. According to the World Health Organization, there are 29 to 31 species and sub-species of tsetse. Like house flies, tsetse flies are 8 to 17 millimeters long, but the tsetse fly is distinguishable in that it folds one wing directly on top of the other in a scissor-like fashion. The tsetse also possesses a long, branched proboscis that extends forward. Tsetse flies are unique vectors in that both the male and female bite. They feed during the day on bloodmeal, with a predilection for swine, cattle and buffalo. The tsetse relies heavily on visual and olfactory cues to find its prey. The tsetse fly is the primary vector for African trypanosomiasis, also known as African sleeping sickness. African trypanosomiasis is caused by two parasite species: Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. T.b. rhodesiense is also known as East Fuentes 3 African sleeping sickness, and T.b. gambiense as West African sleeping sickness (Word Health Organization). The gambiense form of Human African Trypanosomiasis is responsible for 98% of sleeping sickness epidemic cases. The rhodesiense form is found in eastern and southern Africa and affects mostly livestock and wildlife, with humans only being accidentally infected; rhodesiense has been responsible for large outbreaks in the past, however, and this form of the disease is much more rapid and acute (Franco, et al. 2014). This paper will focus on the tsetse flies in Tanzania and nearby countries in East Africa. The tsetse species I will focus in my analysis include G. pallidipes, G. swynnertoni, and G. morsitans. The geographic distributions of these tsetse are as follows: G. pallidipes most oftenly reside in Tanzania, Kenya, Uganda, Zimbabwe, and Ethiopia; G. swynnertoni in Tanzania and Kenya; and G. morsitans in Tanzania, Zambia, and Zimbabwe. Impact on Parks and Peoples The tsetse fly is a prominent vector of African trypanosomiasis, also known as African sleeping sickness, a disease endemic to Tanzania (see Figure 2). Trypanosomiasis is a threat to more than 60 million people throughout Africa. Figure 2. Human African Trypanosomiasis is endemic to Tanzania and demarcated by climatic restrictions. Fuentes 4 Historically, the distribution of pastoralist communities has been shaped by the tsetse. As illustrated in Figure 2, many of the tropical and eastern regions of Africa are tsetse-infested. In these areas, local people have adapted non-milking practices as the cattle would be infected by sleeping sickness and fail to produce milk or reproduce. "A belt defined by tsetse flies" would be created in which it would not be economical to raise cattle (Durham B 2017). Because the tsetse fly is dependent on specific climatic and temperature restrictions, the disease itself has also been restricted between the “14th latitude north and the 29th latitude south on the African continent” (“African Trypanosomiasis”). In a study sampling eight sites in the Ngorongoro Crater Conservation Area, of 193 livestock, 47 % of cattle, 91.7 % of sheep, and Figure 3. Impact of cattle distribution in tsetse 60.8 % of goats were found to harbor a form of infested areas (“Tsetse fly costs agriculture billions every year”). the Trypanosoma brucei parasite (Ruiz et al. 2015). Local sheep and goats in East Africa were found to be carriers of the T. brucei rhodesiense subspecies, which causes acute human trypanosomiasis (Ruiz et al. 2015). Most of these sampled animals belonged to pastoralist (Maasai) herdsmen. The parasite, after invading the nervous system and blood-brain barrier, has vast neurological effects on its victims. Symptoms of sleeping sickness in humans and animals may include intermittent fever, swollen lymph nodes, and aching muscles and joints in the first stages of the Fuentes 5 disease. The disease culminates in progressive mental deterioration, ataxia, a disturbed sleep schedule, and finally death if untreated. Beyond Human African trypanosomiasis’s direct effects on people, both human and animal diseases are detrimental to the economic viability and the nutritional potential of human populations, decreasing the overall welfare in endemic regions. In Tanzania, tsetse flies pervade about one-third of the 940,000 square miles mainland, accounting to a loss of approximately 4.75 billion USD in agricultural potential (Ruiz et al. 2015). According to the World Health Organization, the parasite is detrimental to both agricultural development and cattle rearing. Trypanosomiasis’ impact is especially critical because of globalization, deforestation, climate change, and loss of blood meal species. Domesticated livestock are becoming a prominent target for the tsetse (Ruiz et al. 2015). In summary, African trypanosomiasis has a very significant influence on both parks and people, and on shaping the boundaries and economic and health prospects of the continent of Africa. Thus, to mitigate the increasing impact of African trypanosomiasis, it is important to understand the mechanics of the disease’s primary vector, and incorporate effective community-based strategies into public health and policy. Hypotheses In this paper I will investigate three hypotheses: 1) The tsetse fly is attracted to dark colors, especially blue and black. Also, the tsetse fly is least attracted to lighter colors of green and yellow. 2) Animals with dark colors suffer higher rates of tsetse bites than animals with lighter colors. Fuentes 6 3) The tsetse fly is repelled from black and white stripes, such as those of the zebra, because the stripes may create an optical illusion to the flies. The second hypothesis follows from the first hypothesis, for if tsetse flies are attracted to darker colors generally, then one would expect animals with dark colors to endure more tsetse bites. Research Question This paper will investigate the question: what colors and patterns are the tsetse fly attracted to and repelled from, and how can this knowledge be used to mitigate the impact of African trypanosomiasis on people, livestock, and wildlife? Methods of Hypothesis #1 Hypothesis 1: The tsetse fly is attracted to dark colors, especially blue and black, and least attracted to lighter colors of green and yellow. When travelling longer distances of up to over 90 meters, tsetse flies are guided by chemical (olfactory) cues to find their blood meal. These include cattle odors, carbon dioxide, and urine. Once within closer range to their hosts, the tsetse relies on visual cues, such as shape, size, movement, contrast vs background, color, pattern (Mehlhorn, 2008). The most attractive color to the tsetse fly is royal blue, with a high reflectivity at 650 nm (mid blue) and low ultraviolet reflectivity. Generally, the attractiveness of a surface is increased by blue and red reflectivity, and diminished by ultraviolet and green-yellow reflectivity (Mehlhorn, 2008). The correlation between color and tsetse fly attraction can be observed in a Zimbabwe Fuentes 7 study, in which colored fabrics and paints were measured using an ultraviolet spectrophotometer to create tsetse traps with 53 different colors (Green, C. H., and S. Flint, 1986). Each trap is a cube of 90 cm side, with the entrance at the base of one side along with a cloth cover (see Figure 4). These traps were positioned 100 m apart from one another. The color of the cloth in each trial is manipulated as the independent variable. The dependent variable is the “trap score,” or the percent of flies trapped in the cubes. Colors were selected based on their reflectivity between 300 and 700 nanometers. Paint was added to specific colored fabrics that reflected specific color radiations. The reflection of blue on the electromagnetic spectrum could be made by mixing paints that reflected more visible blue light (Green, C. H., and S. Flint, 1986). Figure 4. Isometric view of cubed tsetse fly trap (Green, C. H, 1988). Fuentes 8 Figure 5. The relationship between blue reflectivity and trap score was further investigated using a color series made by mixing white and yellow paints, since white Brigh and yellow differ mainly in their blue reflectivity (Green, C. H., and S. Flint. 1986). Here, the lowercase letters represent a spectrum of white and yellow colors (a = most t white and g = most yellow) in which whiter pigments have higher blue reflectivity. royal blue emerged as the “best” trap material. Green and yellow had the lowest trap scores and were considered unattractive to the tsetse (Green, C. H., and S. Flint. 1986). Another study investigating the optimization of the color and fabric of tsetse targets found that the best blue targets attract three times the amount of tsetse because of the cloths’ UV reflectance levels. “Hence selecting fabrics for use in targets must be based on spectral analysis of the fabrics' reflectance across the spectrum visible to tsetse.” In other words, certain pigments of blue make more attractive targets, and this nuance in color variation should be considered when creating tsetse fly traps (Lindh, J.M., et al. 2012).