Browsing by Author "Estes, Anna B."

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Assessing risk factors for Trypanosome infections in cattle in wildlife interface areas in Northern Tanzania
    (Journal of Infectious Diseases and Epidemiology, 2019) Ngongolo, Kelvin; Estes, Anna B.; Hudson, Peter J.; Gwakisa, Paul S.
    Trypanosomosis is a vector-borne, tropical disease that causes mortality and morbidity in livestock and humans. In this study, we investigated the risk factors for trypanosome infection in cattle in the Maasai Steppe of northern Tanzania. We assessed the influence of age, sex, herd size and history of treatment against trypanosomosis as risk factors of trypanosome infection. Cattle blood samples were collected from 150 cattle in three villages in the vicinity of Tarangire National Park, which acts as a reservoir of tsetse flies, the trypanosome vector. Parasite species were identified using a nested Polymerase Chain Reaction (n-PCR). Smaller herd sizes, young age (1-2 years), and male sex significantly increased the risk of trypanosome infections. Efforts to control trypanosome infection should be strategically based on location and season while considering age, treatment and herd size as risk factors.
  • Thumbnail Image
    Item
    Influence of seasonal cattle movement on prevalence o f trypano-some infections in cattle in the Maasai Steppe
    (ClinMed International Library, 2019) Ngongolo, Kelvin; Estes, Anna B.; Hudson, Peter J.; Gwakisa, Paul S.
    Animal African Trypanosomosis is a Neglected Tropical Disease with significant impacts to pastoral community livelihoods. Our study sought to determine the influence of seasonal cattle movements on the prevalence of trypanosome infections in cattle in the pastoral areas of the Maasai Steppe. Identification of spatial and temporal dynamics of trypanosome infections in cattle is essential for designing effective control strategies. To identify potential hotspots of trypanosome transmission, we worked with 5 pastoralists in each of 3 villages in the Maasai Steppe of northern Tanzania, and consecutively sampled 10 of each of their cattle in 3 periods, covering both wet and dry season grazing ranges (July 2017 to January 2018). Each time blood was collected from the cattle, a prophylactic dose of diminazene aceturate was administered to clear any parasites acquired in the previous 3 months. We then used participatory mapping techniques to identify the areas where the pastoralists had grazed their herds since the last sampling period, and interviewed them about any disease control methods they practice. Trypanosome infections in the sampled cattle blood were detected using nested polymerase chain reaction with ITS-1 primers. The overall prevalence of trypanosome infections across all sample periods and villages was 12%, though this varied distinctly by season and grazing area. Prevalence in July 2017 (19.33%) was significantly higher than prevalence in October 2017 (2%) (p < 0.05). A total of 45 grazing areas were identified and cattle acquired trypanosome infections in almost half of these (n =21). Targeted awareness on seasonality and hotspot areas of trypanosome infections will help Maasai pastoralists to plan movement of their cattle strategically to avoid disease risk. These results also suggest enhanced control strategies for Trypanosomosis during the months of the year when cattle are moved further from homesteads to graze in hotspot areas.
  • Thumbnail Image
    Item
    Patterns of tsetse abundance and trypanosome infection rates among habitats of surveyed villages in Maasai steppe of northern Tanzania
    (BioMed Central, 2017) Ngonyoka, Anibariki; Gwakisa, Paul S.; Estes, Anna B.; Salekwa, Linda P.; Nnko, Happiness J.; Hudson, Peter J.; Cattadori, Isabella M.
    Background: Changes of land cover modify the characteristics of habitat, host-vector interaction and consequently infection rates of disease causing agents. In this paper, we report variations in tsetse distribution patterns, abundance and infection rates in relation to habitat types and age in the Maasai Steppe of northern Tanzania. In Africa, Tsetse-transmitted trypanosomiasis negatively impacted human life where about 40 million people are at risk of contracting the disease with dramatic socio-economic consequences, for instance, loss of livestock, animal productivity, and manpower. Methods: We trapped tsetse flies in dry and wet seasons between October 2014 and May 2015 in selected habitats across four villages: Emboreet, Loiborsireet, Kimotorok and Oltukai adjacent to protected areas. Data collected include number and species of tsetse flies caught in baited traps, PCR identification of trypanosome species and extraction of monitored Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectrometer (MODIS). Results: Our findings demonstrate the variation of tsetse fly species abundance and infection rates among habitats in surveyed villages in relation to NDVI and host abundance. Results have shown higher tsetse fly abundance in Acacia-swampy ecotone and riverine habitats for Emboreet and other villages, respectively. Tsetse abundance was inconsistent among habitats in different villages. Emboreet was highly infested with Glossina swynnertoni (68%) in ecotone and swampy habitats followed by G. morsitans (28%) and G. pallidipes (4%) in riverine habitat. In the remaining villages, the dominant tsetse fly species by 95% was G. pallidipes in all habitats. Trypanosoma vivax was the most prevalent species in all infected flies (95%) with few observations of co-infections (with T. congolense or T. brucei). Conclusions: The findings of this study provide a framework to mapping hotspots of tsetse infestation and trypanosomiasis infection and enhance the communities to plan for effective control of trypanosomiasis.
  • Thumbnail Image
    Item
    Seasonal variation of tsetse fly species abundance and prevalence of trypanosomes in the Maasai Steppe, Tanzania.
    (PupMed, 2017) Nnko, Happiness J.; Ngonyoka, Anibariki; Salekwa, Linda; Estes, Anna B.; Hudson, Peter J.; Gwakisa, Paul S.; Cattadori, Isabella M.
    Tsetse flies, the vectors of trypanosomiasis, represent a threat to public health and economy in sub-Saharan Africa. Despite these concerns, information on temporal and spatial dynamics of tsetse and trypanosomes remain limited and may be a reason that control strategies are less effective. The current study assessed the temporal variation of the relative abundance of tsetse fly species and trypanosome prevalence in relation to climate in the Maasai Steppe of Tanzania in 2014-2015. Tsetse flies were captured using odor-baited Epsilon traps deployed in ten sites selected through random subsampling of the major vegetation types in the area. Fly species were identified morphologically and trypanosome species classified using PCR. The climate dataset was acquired from the African Flood and Drought Monitor repository. Three species of tsetse flies were identified: G. swynnertoni (70.8%), G. m. morsitans (23.4%), and G.pallidipes (5.8%). All species showed monthly changes in abundance with most of the flies collected in July. The relative abundance of G. m. morsitans and G. swynnertoni was negatively correlated with maximum and minimum temperature, respectively. Three trypanosome species were recorded: T. vivax (82.1%), T. brucei (8.93%), and T. congolense (3.57%). The peak of trypanosome infections in the flies was found in October and was three months after the tsetse abundance peak; prevalence was negatively correlated with tsetse abundance. A strong positive relationship was found between trypanosome prevalence and temperature. In conclusion, we find that trypanosome prevalence is dependent on fly availability, and temperature drives both tsetse fly relative
  • Thumbnail Image
    Item
    Variation of tsetse fly abundance in relation to habitat and host presence in the Maasai Steppe, Tanzania
    (Wiley Online Library, 2017) Ngonyoka, Anibariki; Gwakisa, Paul S.; Estes, Anna B.; Nnko, Happiness J.; Hudson, Peter J.; Cattadori, Isabella M.
    Human activities modify ecosystem structure and function and can also alter the vital rates of vectors and thus the risk of infection with vector‐borne diseases. In the Maasai Steppe ecosystem of northern Tanzania, local communities depend on livestock and suitable pasture that is shared with wildlife, which can increase tsetse abundance and the risk of trypanosomiasis. We monitored the monthly tsetse fly abundance adjacent to Tarangire National Park in 2014–2015 using geo‐referenced, baited epsilon traps. We examined the effect of habitat types and vegetation greenness (NDVI) on the relative abundance of tsetse fly species. Host availability (livestock and wildlife) was also recorded within 100×100 m of each trap site. The highest tsetse abundance was found in the ecotone between Acacia‐Commiphora woodland and grassland, and the lowest in riverine woodland. Glossina swynnertoni was the most abundant species (68%) trapped throughout the entire study, while G. pallidipes was the least common (4%). Relative species abundance was negatively associated with NDVI, with greatest abundance observed in the dry season. The relationship with the abundance of wildlife and livestock was more complex, as we found positive and negative associations depending on the host and fly species. While habitat is important for tsetse distribution, hosts also play a critical role in affecting fly abundance and, potentially, trypanosomiasis risk.