Factors Affecting the Propensity of Tsetse Flies to Enter Houses and Attack Humans Inside: Increased Risk of Sleeping Sickness in Warmer Climates

Background Sleeping sickness, or human African trypanosomiasis, is caused by two species of Trypanosoma brucei that are transmitted to humans by tsetse flies (Glossina spp.) when these insects take a bloodmeal. It is commonly assumed that humans must enter the normal woodland habitat of the flies to become infected, but recent studies found that tsetse frequently attack humans inside buildings. Factors affecting human/tsetse contact in buildings need identification. Methodology/Principal Findings In Zimbabwe, tsetse were allowed access to a house via an open door. Those in the house at sunset, and those alighting on humans in the house during the day, were caught using hand-nets. Total catches were unaffected by: (i) the presence of humans in the house and at the door, (ii) wood smoke from a fire inside the house or just outside, (iii) open windows, and (iv) chemicals simulating the odor of cattle or of humans. Catches increased about 10-fold with rising ambient temperatures, and during the hottest months the proportion of the total catch that was taken from the humans increased from 5% to 13%. Of the tsetse caught from humans, 62% consisted of female G. morsitans morstans and both sexes of G. pallidipes, i.e., the group of tsetse that normally alight little on humans. Some of the tsetse caught were old enough to be effective vectors. Conclusion/Significance Present results confirm previous suggestions that buildings provide a distinctive and important venue for transmission of sleeping sickness, especially since the normal repellence of humans and smoke seems poorly effective in such places. The importance of the venue would be increased in warmer climates

Costs Of Using “Tiny Targets” to Control Glossina fuscipes fuscipes, a Vector of Gambiense Sleeping Sickness in Arua District of Uganda

Introduction To evaluate the relative effectiveness of tsetse control methods, their costs need to be analysed alongside their impact on tsetse populations. Very little has been published on the costs of methods specifically targeting human African trypanosomiasis. Methodology/Principal Findings In northern Uganda, a 250 km2 field trial was undertaken using small (0.5 X 0.25 m) insecticide-treated targets (“tiny targets”). Detailed cost recording accompanied every phase of the work. Costs were calculated for this operation as if managed by the Ugandan vector control services: removing purely research components of the work and applying local salaries. This calculation assumed that all resources are fully used, with no spare capacity. The full cost of the operation was assessed at USD 85.4 per km2, of which USD 55.7 or 65.2% were field costs, made up of three component activities (target deployment: 34.5%, trap monitoring: 10.6% and target maintenance: 20.1%). The remaining USD 29.7 or 34.8% of the costs were for preliminary studies and administration (tsetse surveys: 6.0%, sensitisation of local populations: 18.6% and office support: 10.2%). Targets accounted for only 12.9% of the total cost, other important cost components were labour (24.1%) and transport (34.6%). Discussion Comparison with the updated cost of historical HAT vector control projects and recent estimates indicates that this work represents a major reduction in cost levels. This is attributed not just to the low unit cost of tiny targets but also to the organisation of delivery, using local labour with bicycles or motorcycles. Sensitivity analyses were undertaken, investigating key prices and assumptions. It is believed that these costs are generalizable to other HAT foci, although in more remote areas, with denser vegetation and fewer people, costs would increase, as would be the case for other tsetse control techniques

We remember… Elders’ memories and perceptions of sleeping sickness control interventions in West Nile, Uganda

The traditional role of African elders and their connection with the community make them important stakeholders in community-based disease control programmes. We explored elders’ memories related to interventions against sleeping sickness to assess whether or not past interventions created any trauma which might hamper future control operations. Using a qualitative research framework, we conducted and analysed twenty-four in-depth interviews with Lugbara elders from north-western Uganda. Participants were selected from the villages inside and outside known historical sleeping sickness foci. Elders’ memories ranged from examinations of lymph nodes conducted in colonial times to more recent active screening and treatment campaigns. Some negative memories dating from the 1990s were associated with diagnostic procedures, treatment duration and treatment side effects, and were combined with memories of negative impacts related to sleeping sickness epidemics particularly in HAT foci. More positive observations from the recent treatment campaigns were reported, especially improvements in treatment. Sleeping sickness interventions in our research area did not create any permanent traumatic memories, but memories remained flexible and open to change. This study however identified that details related to medical procedures can remain captured in a community’s collective memory for decades. We recommend more emphasis on communication between disease control programme planners and communities using detailed and transparent information distribution, which is not one directional but rather a dialogue between both parties

A neglected aspect of the epidemiology of sleeping sickness: the propensity of the tsetse fly vector to enter houses.

BACKGROUND: When taking a bloodmeal from humans, tsetse flies can transmit the trypanosomes responsible for sleeping sickness, or human African trypanosomiasis. While it is commonly assumed that humans must enter the normal woodland habitat of the tsetse in order to have much chance of contacting the flies, recent studies suggested that important contact can occur due to tsetse entering buildings. Hence, we need to know more about tsetse in buildings, and to understand why, when and how they enter such places. METHODOLOGY/PRINCIPAL FINDINGS: Buildings studied were single storied and comprised a large house with a thatched roof and smaller houses with roofs of metal or asbestos. Each building was unoccupied except for the few minutes of its inspection every two hours, so focusing on the responses of tsetse to the house itself, rather than to humans inside. The composition, and physiological condition of catches of tsetse flies, Glossina morsitans morsitans and G. pallidipes, in the houses and the diurnal and seasonal pattern of catches, were intermediate between these aspects of the catches from artificial refuges and a host-like trap. Several times more tsetse were caught in the large house, as against the smaller structures. Doors and windows seemed about equally effective as entry points. Many of the tsetse in houses were old enough to be potential vectors of sleeping sickness, and some of the flies alighted on the humans that inspected the houses. CONCLUSION/SIGNIFICANCE: Houses are attractive in themselves. Some of the tsetse attracted seem to be in a host-seeking phase of behavior and others appear to be looking for shelter from high temperatures outside. The risk of contracting sleeping sickness in houses varies according to house design

The effect of partial substitution of Moringa oleifera leaf meal on the relative growth performance and incidence of scours in piglets

The effect of Moringa oleifera leaf meal (MOLM) as a scour prophylaxis and on growth parameters of piglets was evaluated. A total of 168 piglets from 15 litters were cross fostered and randomly assigned to three dietary treatments; 0% MOLM (control diet), 4.5% MOLM and 8% MOLM inclusion test diets. The feed conversion ratio (FCR), average daily gain (ADG), body weight (BW) and average daily feed intake (ADFI) and faecal viscosity (FV) were measured. The effect of MOLM inclusion level on FCR, ADG, BW, ADFI and FV was analysed using PROC GLM of SAS. Dietary inclusion of 4.5% MOLM significantly reduced the ADFI of piglets when compared to 0% MOLM, however 8% MOLM had higher ADFI than either 0% or 4.5% MOLM inclusion. There was no effect of MOLM dietary inclusion on ADG; however 8% MOLM dietary inclusion had a higher FCR when compared to 0% or 4.5% MOLM. Piglets in control treatment (0% MOLM) had more incidence of scours than 8% MOLM diet and did not differ from 4.5% MOLM. There was no effect in faecal viscosity between 4.5% and 8% MOLM diets. MOLM dietary inclusion significantly reduced the cost per kilogram weight gain. It was concluded that MOLM can replace soya bean meal up to 4.5% in piglet creep diets

Where, when and why do tsetse contact humans? Answers from studies in a National Park of Zimbabwe

The original publication is available at http://journals.plos.org/plosntdsCITATION: Torr, S.J., Chamisa, A., Mangwiro, T.N.C. & Vale, G.A. 2012. Where, when and why do tsetse contact humans?: Answers from studies in a National Park of Zimbabwe. PLoS Neglected Tropical Diseases, s 6(8):e1791, doi:10.1371/journal.pntd.0001791.Background: Sleeping sickness, also called human African trypanosomiasis, is transmitted by the tsetse, a blood-sucking fly confined to sub-Saharan Africa. The form of the disease in West and Central Africa is carried mainly by species of tsetse that inhabit riverine woodland and feed avidly on humans. In contrast, the vectors for the East and Southern African form of the disease are usually savannah species that feed mostly on wild and domestic animals and bite humans infrequently, mainly because the odours produced by humans can be repellent. Hence, it takes a long time to catch many savannah tsetse from people, which in turn means that studies of the nature of contact between savannah tsetse and humans, and the ways of minimizing it, have been largely neglected. Methodology/Principal Findings: The savannah tsetse, Glossina morsitans morsitans and G. pallidipes, were caught from men in the Mana Pools National park of Zimbabwe. Mostly the catch consisted of young G. m. morsitans, with little food reserve. Catches were increased by 4–8 times if the men were walking, not stationary, and increased about ten times more if they rode on a truck at 10 km/h. Catches were unaffected if the men used deodorant or were baited with artificial ox odour, but declined by about 95% if the men were with an ox. Surprisingly, men pursuing their normal daily activities were bitten about as much when in or near buildings as when in woodland. Catches from oxen and a standard ox-like trap were poor indices of the number and physiological state of tsetse attacking men. Conclusion/Significance: The search for new strategies to minimize the contact between humans and savannah tsetse should focus on that occurring in buildings and vehicles. There is a need to design a man-like trap to help to provide an index of sleeping sickness risk.Financial support: UNICEF/UNDP/World Bank/FAO Special Programme for Research and Training in Tropical Diseases (Project no. A70598)http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0001791Publisher's versio

Percent distribution of ovarian categories of catches at the trap (A), refuges (B) and Houses 1–3 (C).

<p>Based on pooled data for all months. Sample sizes for the trap, refuges and houses were 86, 59 and 98, respectively, for <i>G. m. morsitans</i> and 627, 50 and 307, respectively, for <i>G. pallidipes</i>.</p

Temperature in a refuge and Houses 1–3 at various times of day.

<p>Temperature is expressed as the mean difference between the temperature in the refuge or house and the temperature in a Stevenson screen, so that if the difference is negative the temperature in the refuge or house was lower than in the screen. Vertical bars through the plots indicate the 95% confidence limits of the mean. Some plots are slightly displaced horizontally to ensure that the bars are not confused. Houses 1, 2 and 3 had roofs of thatch, asbestos and tin, respectively.</p

Percent distribution of uterine contents of catches at the trap (A), refuges (B) and Houses 1–3 (C).

<p>L1, L2 and L3 are first, second and third instar larvae, respectively. Sample sizes for the trap, refuges and houses were 80, 54 and 85, respectively, for <i>G. m. morsitans</i> and 601, 47 and 295, respectively, for <i>G. pallidipes</i>.</p

Catches from various treatments of House 1, and from a trap and refuges.

<p>Total catches of each sex and species of tsetse in a number of days in Aug 2009 to Aug 2010, the mean daily catch of all sexes and species combined, and the 95% confidence limits of the mean.</p