Patterns of tsetse abundance and trypanosome infection rates among habitats of surveyed villages in Maasai steppe of northern Tanzania

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-economical 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.

The Contribution of Tanzanian National Parks in Controlling the Vectors of Sleeping Sickness

This paper summarises efforts to control Sleeping sickness [Human African Trypanosomiasis (HAT)] by Tsetse flies and Trypanosomiaisis (T & T) control for the 7 consecutive years although started a decade ago in Tanzania National Parks (TANAPA). These efforts are critical for curbing HAT incidences and HAT epidemics. HAT cases have had profound negative impacts on human health, affecting local residents and international travel as well as tourism industry resulting into human and animal health burden and reduction in tourism income. Understanding the current efforts is essential in the proper planning and decision making on developing effective control strategy against T & T control. In this paper, we summarize the recent efforts in the control of T & T in National Parks and discuss the constraints faced. The information will enable TANAPA and other concerned authorities to make informed decision on optimal ways of controlling HAT in National Parks. The results show that much control efforts have so far concentrated in Serengeti, Ruaha, Tarangire and Katavi National Parks where tsetse fly challenges are high. A total 21,143 (average 3020) Insecticide Treated Targets (ITT) were deployed in different areas in the parks and 82,899 (average 20,725) cars entering these parks were sprayed from 2007/2008 to 2014/2015 and 2007/2008 to 2010/2011 respectively. Deployed ITTs lead to a drastic reduction of FTDs of the two dominant tsetse species to 1.3 and 1.4 of G. swynnertoni and G. pallidipes respectively, and the decline was significant at P = 0.011. The major challenges faced include tsetse re-invasion in controlled areas;resurgence of HAT cases when control efforts are relaxed, ITT maintenance and inadequate health education programs. The control strategy should be continuous and scaled up as failure to implement an effective and sustainable system for HAT control will increase the risk of new epidemic that would impede tourism development.

Update of transmission modelling and projections of gambiense human African trypanosomiasis in the Mandoul focus, Chad

Background:In recent years,a programme of vector control,screening and treatment of gambiense human African trypanosomiasis(gHAT)infections led to a rapid decline in cases in the Mandoul focus of Chad.To represent the biology of transmission between humans and tsetse,we previously developed a mechanistic transmission model,fitted to data between 2000 and 2013 which suggested that transmission was interrupted by 2015.The present study outlines refinements to the model to:(1)Assess whether elimination of transmission has already been achieved despite low-level case reporting;(2)quantify the role of intensified interventions in transmission reduction;and(3)predict the trajectory of gHAT in Mandoul for the next decade under different strategies.Method:Our previous gHAT transmission model for Mandoul was updated using human case data(2000-2019)and a series of model refinements.These include how diagnostic specificity is incorporated into the model and improvements to the fitting method(increased variance in observed case reporting and how underreporting and improvements to passive screening are captured).A side-by-side comparison of fitting to case data was performed between the models.Results:We estimated that passive detection rates have increased due to improvements in diagnostic availability in fixed health facilities since 2015,by 2.1-fold for stage 1 detection,and 1.5-fold for stage 2.We find that whilst the diagnostic algorithm for active screening is estimated to be highly specific(95%credible interval(CI):99.9-100%,Specificity=99.9%),the high screening and low infection levels mean that some recently reported cases with no parasitological confirmation might be false positives.We also find that the focus-wide tsetse reduction estimated through model fitting(95%CI:96.1-99.6%,Reduction=99.1%)is comparable to the reduction previously measured by the decline in tsetse catches from monitoring traps.In line with previous results,the model suggests that transmission was interrupted in 2015 due to intensified interventions.Conclusions:We recommend that additional confirmatory testing is performed in Mandoul to ensure the endgame can be carefully monitored.More specific measurement of cases,would better inform when it is safe to stop active screening and vector control,provided there is a strong passive surveillance system in place.