Potential impacts of climate change on geographical distribution of three primary vectors of African Trypanosomiasis in Tanzania’s Maasai Steppe: G. m. morsitans, G. pallidipes and G. swynnertoni

In the Maasai Steppe, public health and economy are threatened by African Trypanosomiasis, a debilitating and fatal disease to livestock (African Animal Trypanosomiasis -AAT) and humans (Human African Trypanosomiasis—HAT), if not treated. The tsetse fly is the primary vector for both HAT and AAT and climate is an important predictor of their occurrence and the parasites they carry. While understanding tsetse fly distribution is essential for informing vector and disease control strategies, existing distribution maps are old and were based on coarse spatial resolution data, consequently, inaccurately representing vector and disease dynamics necessary to design and implement fit-for-purpose mitigation strategies. Also, the assertion that climate change is altering tsetse fly distribution in Tanzania lacks empirical evidence. Despite tsetse flies posing public health risks and economic hardship, no study has modelled their distributions at a scale needed for local planning. This study used MaxEnt species distribution modelling (SDM) and ecological niche modeling tools to predict potential distribution of three tsetse fly species in Tanzania’s Maasai Steppe from current climate information, and project their distributions to midcentury climatic conditions under representative concentration pathways (RCP) 4.5 scenarios. Current climate results predicted that G. m. morsitans, G. pallidipes and G swynnertoni cover 19,225 km2, 7,113 km2 and 32,335 km2 and future prediction indicated that by the year 2050, the habitable area may decrease by up to 23.13%, 12.9% and 22.8% of current habitable area, respectively. This information can serve as a useful predictor of potential HAT and AAT hotspots and inform surveillance strategies. Distribution maps generated by this study can be useful in guiding tsetse fly control managers, and health, livestock and wildlife officers when setting surveys and surveillance programs. The maps can also inform protected area managers of potential encroachment into the protected areas (PAs) due to shrinkage of tsetse fly habitats outside PAs.

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Epidemiology of tsetse flies in the transmission of trypanosomiasis: technical review of The Gambia experience

International Journal of Biological and Chemical Sciences ◽

10.4314/ijbcs.v14i3.35 ◽

2020 ◽

Vol 14 (3) ◽

pp. 1093-1102

Author(s):

Alpha Kargbo ◽

Rex A. Kuye

Keyword(s):

Climate Change ◽

Anthropogenic Activities ◽

Control Program ◽

The Gambia ◽

Tsetse Fly ◽

Extreme Weather Events ◽

Tsetse Flies ◽

Insect Vector ◽

Relative Significance ◽

River Region

Climate change has posed serious health threats on both man and animals. This ranges from effects of progressive temperature rises from global warming to extreme weather events and anthropogenic activities and this has affected insect-vector distributions worldwide. Tsetse fly species transmit Trypanosomes but relative significance depends largely on the strength of their interactions with susceptible hosts. Tsetse flies are the main vectors of Trypanosomiasis and their existence pose a threat to the survival of cattle, small ruminates and equines in The Gambia. It is known to be one of the most vital parasitic diseases affecting livestock productivity in The Gambia and equines are very susceptible. Central River Region is mainly infested with the tsetse fly Glossina morsitan submorsitan a major vector of Trypanosomiasis among animals in the country and it is mainly found in dry, canopied, savannah woodland. Glossina palpalis is also present, but are more limited to riverine vegetation in the area. This work seeks to show the havoc caused by trypanosomiasis and the urgency for more studies to investigate the patterns of transmission of this disease especially in the context of climate change in other for a better control program for this zoonosis in The Gambia.Keywords: Climate Change, Glossina, Trypanosome, Cattle, Equine.

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Livestock, pathogens, vectors, and their environment: a causal inference-based approach to estimating the pathway-specific effect of livestock on human African trypanosomiasis risk

10.1101/2022.01.13.22268994 ◽

2022 ◽

Author(s):

Julianne Meisner ◽

Agapitus Kato ◽

Marshall Lemerani ◽

Erick Mwamba Miaka ◽

Acaga Ismail Taban ◽

...

Keyword(s):

Environmental Change ◽

Causal Inference ◽

Disease Transmission ◽

Human African Trypanosomiasis ◽

Spatial Epidemiology ◽

Specific Effect ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Change Effect

Livestock are important reservoirs for many diseases, and investigation of such zoonoses has long been the focus of One Health research. However, the effects of livestock on human and environmental health extend well beyond direct disease transmission. In this retrospective ecological cohort study we use pre-existing data and methods derived from causal inference and spatial epidemiology to estimate three hypothesized mechanisms by which livestock can come to bear on human African trypanosomiasis (HAT) risk: the reservoir effect, by which infected cattle and pigs are a source of infection to humans; the zooprophylactic effect, by which preference for livestock hosts exhibited by the tsetse fly vector of HAT means that their presence protects humans from infection; and the environmental change effect, by which livestock keeping activities modify the environment in such a way that habitat suitability for tsetse flies, and in turn human infection risk, is reduced. We conducted this study in four high burden countries: at the point level in Uganda, Malawi, and Democratic Republic of Congo (DRC), and at the county-level in South Sudan. Our results indicate cattle and pigs play an important reservoir role for the rhodesiense form (rHAT) in Uganda, however zooprophylaxis outweighs this effect for rHAT in Malawi. For the gambiense form (gHAT) we found evidence that pigs may be a competent reservoir, however dominance of the reservoir versus zooprophylactic pathway for cattle varied across countries. We did not find compelling evidence of an environmental change effect.

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Tsetse blood-meal sources, endosymbionts and trypanosome-associations in the Maasai Mara National Reserve, a wildlife-human-livestock interface

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0008267 ◽

2021 ◽

Vol 15 (1) ◽

pp. e0008267

Author(s):

Edward Edmond Makhulu ◽

Jandouwe Villinger ◽

Vincent Owino Adunga ◽

Maamun M. Jeneby ◽

Edwin Murungi Kimathi ◽

...

Keyword(s):

Blood Meal ◽

Glossina Pallidipes ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Buffalo ◽

African Trypanosomiasis ◽

African Trypanosomes ◽

Sodalis Glossinidius ◽

Vertebrate Hosts ◽

Blood Meals

African trypanosomiasis (AT) is a neglected disease of both humans and animals caused by Trypanosoma parasites, which are transmitted by obligate hematophagous tsetse flies (Glossina spp.). Knowledge on tsetse fly vertebrate hosts and the influence of tsetse endosymbionts on trypanosome presence, especially in wildlife-human-livestock interfaces, is limited. We identified tsetse species, their blood-meal sources, and correlations between endosymbionts and trypanosome presence in tsetse flies from the trypanosome-endemic Maasai Mara National Reserve (MMNR) in Kenya. Among 1167 tsetse flies (1136 Glossina pallidipes, 31 Glossina swynnertoni) collected from 10 sampling sites, 28 (2.4%) were positive by PCR for trypanosome DNA, most (17/28) being of Trypanosoma vivax species. Blood-meal analyses based on high-resolution melting analysis of vertebrate cytochrome c oxidase 1 and cytochrome b gene PCR products (n = 354) identified humans as the most common vertebrate host (37%), followed by hippopotamus (29.1%), African buffalo (26.3%), elephant (3.39%), and giraffe (0.84%). Flies positive for trypanosome DNA had fed on hippopotamus and buffalo. Tsetse flies were more likely to be positive for trypanosomes if they had the Sodalis glossinidius endosymbiont (P = 0.0002). These findings point to complex interactions of tsetse flies with trypanosomes, endosymbionts, and diverse vertebrate hosts in wildlife ecosystems such as in the MMNR, which should be considered in control programs. These interactions may contribute to the maintenance of tsetse populations and/or persistent circulation of African trypanosomes. Although the African buffalo is a key reservoir of AT, the higher proportion of hippopotamus blood-meals in flies with trypanosome DNA indicates that other wildlife species may be important in AT transmission. No trypanosomes associated with human disease were identified, but the high proportion of human blood-meals identified are indicative of human African trypanosomiasis risk. Our results add to existing data suggesting that Sodalis endosymbionts are associated with increased trypanosome presence in tsetse flies.

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Geographic shifts in Aedes aegypti habitat suitability in Ecuador using larval surveillance data and ecological niche modeling: Implications of climate change for public health vector control

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0007322 ◽

2019 ◽

Vol 13 (4) ◽

pp. e0007322 ◽

Cited By ~ 9

Author(s):

Catherine A. Lippi ◽

Anna M. Stewart-Ibarra ◽

M. E. Franklin Bajaña Loor ◽

Jose E. Dueñas Zambrano ◽

Nelson A. Espinoza Lopez ◽

...

Keyword(s):

Public Health ◽

Climate Change ◽

Aedes Aegypti ◽

Vector Control ◽

Habitat Suitability ◽

Ecological Niche ◽

Ecological Niche Modeling ◽

Niche Modeling ◽

Surveillance Data

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Tsetse Flies (Glossina) as Vectors of Human African Trypanosomiasis: A Review

BioMed Research International ◽

10.1155/2016/6201350 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 18

Author(s):

Florence Njeri Wamwiri ◽

Robert Emojong Changasi

Keyword(s):

Disease Transmission ◽

Human African Trypanosomiasis ◽

Tsetse Fly ◽

Public Health Issue ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Land Use Patterns ◽

Transmission Cycle ◽

Use Patterns ◽

Abundance And Distribution

Human African Trypanosomiasis (HAT) transmitted by the tsetse fly continues to be a public health issue, despite more than a century of research. There are two types of the disease, the chronicgambienseand the acuterhodesiense-HAT. Fly abundance and distribution have been affected by changes in land-use patterns and climate. However, disease transmission still continues. Here, we review some aspects of HAT ecoepidemiology in the context of altered infestation patterns and maintenance of the transmission cycle as well as emerging options in disease and vector control.

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Tsetse blood-meal sources, endosymbionts, and trypanosome infections provide insight into African trypanosomiasis transmission in the Maasai Mara National Reserve, a wildlife-human-livestock interface

10.1101/2020.04.06.027367 ◽

2020 ◽

Cited By ~ 1

Author(s):

Edward Edmond Makhulu ◽

Jandouwe Villinger ◽

Vincent Owino Adunga ◽

Maamun M. Jeneby ◽

Edwin Murungi Kimathi ◽

...

Keyword(s):

Blood Meal ◽

Vector Competence ◽

Glossina Pallidipes ◽

Tsetse Fly ◽

Tsetse Flies ◽

African Buffalo ◽

African Trypanosomiasis ◽

Trypanosome Infection ◽

African Trypanosomes ◽

Blood Meals

AbstractBackgroundAfrican trypanosomiasis (AT) is a neglected disease of both humans and animals caused by Trypanosoma parasites, which are transmitted by obligate hematophagous tsetse flies (Glossina spp.). Understanding of AT transmission is hampered by limited knowledge on interactions of tsetse flies with their vertebrate hosts and the influence of endosymbionts on vector competence, especially in wildlife-human-livestock interfaces. We identified the tsetse species, their blood-meal sources, and the correlation between endosymbiont and trypanosome infection status in the trypanosome-endemic Maasai Mara National Reserve (MMNR) of Kenya.Methodology/Principal FindingsAmong 1167 tsetse flies (1136 Glossina pallidipes, 31 Glossina swynnertoni) collected from 10 sampling sites, 28 (2.4%) were positive by PCR for trypanosomes, majority (17/28) being Trypanosoma vivax. Blood-meal analyses based on high-resolution melting analysis of mitochondrial cytochrome c oxidase 1 and cytochrome b gene PCR products (n = 345) identified humans as the most common vertebrate host (37%), followed by hippopotamus (29.1%), African buffalo (26.3%), elephant (3.39%), and giraffe (0.84%). Trypanosome-infected flies had fed on hippopotamus and buffalo. Additionally, PCR analysis revealed that tsetse flies were more likely to be infected with trypanosomes if they were infected with the Sodalis glossinidius endosymbiont (P = 0.0022 Fisher’s exact test).Conclusions/SignificanceDiverse species of wildlife hosts may contribute to the maintenance of tsetse populations and/or persistent circulation of African trypanosomes in the MMNR. Although the African buffalo is known to be a key reservoir of AT, the higher proportion of hippopotamus blood-meals in trypanosomes-infected flies identified here indicates that other wildlife species may also be important to transmission cycles. No trypanosomes associated with human disease were identified, but the high proportion of human blood-meals identified are indicative of human African trypanosomiasis transmission risk. Furthermore, this work provides data showing that Sodalis endosymbionts can is associated with increased trypanosome infection rates in endemic ecologies.Author summaryHuman and animal African trypanosomiasis are neglected tropical diseases with potential to spread to new areas. Wild animals are important reservoirs for African trypanosomes and crucial in the emergence and re-emergence of AT. Vertebrate host-vector-parasite interactions are integral to trypanosome transmission. We investigated the vertebrate blood-meals and trypanosomes-endosymbionts co-infections in tsetse flies, which have been associated with reservoirs and vector competence, respectively, on AT transmission in Kenya’s Maasai Mara National Reserve. We identified tsetse fly diversity, trypanosome and endosymbiont infection status, and vertebrate blood-meal hosts to infer potential transmission dynamics. We found that Glossina pallidipes was the major tsetse fly vector and that Trypanosoma vivax was the main trypanosome species circulating in the region. Humans, hippopotamus, and buffalo were the most frequented for blood-meals. Buffalo and hippopotamus blood-meals were identified in trypanosome infected flies. Feeding of the flies on both humans and wildlife may potentiate the risk of the human trypanosomiasis in this ecology. Additionally, we found that the endosymbiont Sodalis glossinidius is associated with higher trypanosome infection rates in wild tsetse flies. These findings emphasize the importance of understanding the interaction of tsetse flies with vertebrate blood-meal sources and their endosymbionts in the transmission and control of AT.

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African Trypanosomiasis Dynamics: Modelling the Effects of Treatment, Education, and Vector Trapping

International Journal of Mathematics and Mathematical Sciences ◽

10.1155/2020/3690472 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Yustina A. Liana ◽

Nyimvua Shaban ◽

Goodluck Mlay ◽

Anitha Phibert

Keyword(s):

Disease Transmission ◽

Deterministic Model ◽

Reproduction Number ◽

Public Health Education ◽

Tsetse Fly ◽

Control Measures ◽

Effective Control ◽

Tsetse Flies ◽

Model Parameters ◽

African Trypanosomiasis

African trypanosomiasis is a vector-borne disease that is mainly transmitted by infected tsetse flies. A deterministic model of tsetse fly vector, human, and cattle hosts is formulated and analyzed to gain insights into the disease dynamics. The roles of public health education, treatment, and tsetse fly traps are studied. The effective reproduction number, a threshold used to determine whether the disease persists or dies out in the population, is determined. The sensitivity analysis of the model parameters is performed to determine their relationship with the effective reproduction number. The results show that the tsetse fly biting rate is the most sensitive parameter to the effective reproduction number. Furthermore, the model’s numerical simulation shows that a combination of all three interventions has the most significant impact on the control of African trypanosomiasis. Thus, we recommend that these control measures be put concurrently in endemic areas for effective control of the disease transmission.

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Distribution Of Tsetse Flies And Significance To The Control Of African Trypanosomiasis In Busia County, Kenya

10.21203/rs.3.rs-22364/v1 ◽

2020 ◽

Author(s):

Ferdinard Adungo ◽

Tom Mokaya ◽

Olipher Makwaga ◽

Matilu Mwau

Keyword(s):

Capacity Building ◽

Survey Methods ◽

Cross Sectional Study ◽

Tsetse Fly ◽

Sub Saharan Africa ◽

Tsetse Flies ◽

African Trypanosomiasis ◽

Post Intervention ◽

Cross Sectional ◽

Tsetse Control

Abstract Background: Tsetse flies are the cyclical vectors of both human and animal diseases in Sub-Saharan Africa. Since 2012, Kenya has not recorded a case of human trypanosomiasis. However, African animal trypanosomiasis continues to be a major challenge to livestock production despite decades of control efforts. This study aimed to determine the prevalence of tsetse flies in Busia County post intervention and to build the capacity of local inhabitants in vector control activities. Methods: This cross-sectional study was conducted between May 2018 and December 2018 in Teso South and Teso North sub-counties. Odour-baited biconical traps were deployed for 48 hours in each sampling area and captured tsetse flies were analysed for trypanosome infections. Additionally, training and field demonstrations were conducted as part of capacity building to enhance participation of local inhabitants in tsetse control activities. Results: In Teso South sub-county, 62 tsetse flies were captured in Kwangamor, six in Obekai and 14 in Ngelechom sites. All the captured tsetse flies were classified as G. fuscipes fuscipes. In Teso North sub-county sites of Kapesur, three G. pallidipes were captured, while the Ikapolok sites yielded 12 tsetse flies all G. fuscipes fuscipes. The apparent density of tsetse flies was between 0.08 and 1.55 flies-per trap-per-day across the five study areas with G. fuscipes fuscipes being the dominant species. Microscopic examination of 72 G. fuscipes fuscipes identified three T vivax and one T. congolense positive tsetse flies. No trypanosomes were observed in all the G. pallidipes. Overall infection rate of 1.39% and 4.17% was observed for T. congolense and T. vivax respectively. With regards to capacity building, a total of 26 community members were trained on tsetse fly control activities. Out of which five were selected as focal persons and were further trained on integrated vector management techniques and tsetse survey methods. Conclusions: Tsetse flies in Teso South sub-county, albeit low density, harbour trypanosomes. This calls for an urgent attention to stop potential spread and transmission. Moreover, training of local inhabitants in tsetse control activities will help to strengthen and sustain efforts towards elimination of African trypanosomiasis in Busia County.

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