Impact of Trypanosomosis on African Agriculture
Dr. B. Swallow
The direct effects of Trypanosomosis on susceptible cattle are documented as i) reduced calving rates by 11-20% ii) a 10-20% increased calf mortality, iii) a 10-26% reduced milk offtake from trypanotolerant animals, and iv) a 4-38% reduction in reproduction in sheep and goats. At the herd level, it is estimated that the incidence of Trypanosomosis reduces cattle offtake by 5-30%, milk offtake by 10-40%, and the work performance of oxen by 33%. The risk of Trypanosomosis also shapes farmers choices about livestock purchases, sales and overall herd size. The evidence from a small number of field studies suggests that farmers in areas of high risk keep 25-60% as many cattle as nearby farmers in areas of low risk. Impacts on other livestock species vary greatly depending on the management system and level of susceptibility. Overall it has been estimated that Trypanosomosis reduces the density of cattle by 37% in the sub-humid zone and by 70% in the humid zone.
The indirect effects of Trypanosomosis risk on land use and agricultural production can be inferred from focused field studies and aggregate-level studies that have examined the relationship between livestock and crop production more generally. In mixed farming systems where Trypanosomosis is so severe that it constrains the number of oxen that farmers own, it can reduce the average area planted per household by as much as 50%. By generally constraining farmers from the overall benefits of livestock to farming - less efficient nutrient recycling, less access to farm traction, lower income from milk and meat sales, less access to liquid capital - Trypanosomosis reduces both yields and areas cultivated. It is estimated that the elasticity of livestock stock with respect to total agricultural production is about 0.20: a 50% reduction in livestock population would reduce the total production of agricultural output by 10%.
Summary of discussion:
Studies undertaken by the RTTCP indicate similar levels of impact, however, there is need to also consider the longer term implications through grazing pressures and herd offtake as well as the impact on human health and the nutritional effects. These considerations indicate that there may be very considerable gains to be made from integrated crop/livestock production and that it is here that the greatest rewards will result from tsetse control. Tsetse is a land use issue and priority should be directed to the areas with the best potential for success. In recognition of this the meeting recommended that tsetse infested areas meeting these criteria should be identified and selected as priority for disease intervention within on-going and proposed regional programmes funded by the EC (see also section 9).
The implementation of odour bait techniques for the control of tsetse flies in Eastern and Southern Africa
Mr. R. Allsopp
Of the various techniques available for tsetse control, cattle dipping is probably the least expensive. Although figures are not readily available, SIT is probably the most expensive but is environmentally benign. Depending on local situations and strategic objectives (i.e. control or eradication) there is probably little difference in the costs of the three most widely used chemical control methods viz. discriminate ground spraying, aerial spraying and odour bait techniques. Similarly, barring malpractice, all three have no long term, irreversible effects.
Results of a survey conducted in East and Southern Africa suggest that tsetse control efforts are diminishing and this coincides with the proliferation of odour bait techniques. If this trend continues there is a danger that tsetse populations will recover more quickly than they are cleared. The question is thus raised as to whether it is realistic to simply do more of the same and increase the reliance on odour bait techniques.
Odour bait techniques may prove to be less environmentally benign and less economically advantageous than has been assumed. They may be slow to achieve results and may not be able to eradicate some populations but if managed properly they do have a significant effect on tsetse. They are also well suited to community projects. However, they do not appear to have made significant progress in the battle against tsetse flies in recent years thus are unlikely to do so in the future if left to work in isolation. Other well tried methods are available and should be used to complement the targets, to take up some of the slack and to inject a degree of urgency into this persistent and escalating problem. It is time to review our objectives, assess our performance, reconsider our options, mobilise the available resources and, perhaps, revise our strategies.
The paper is controversial, it presents only one conclusion, there are others. It does, however, raise an important point particularly concerning Sleeping Sickness epidemics where bait techniques are not appropriate and other more rapid methods such as aerial spraying should be considered. The paper suggests that the stance taken by the donors in their move away from former methods based on arguments of environmental pollution may not be supported by science. This raises a serious conflict that needs to be resolved. PAAT should undertake the gathering of the data required to present the facts and facilitate the decision processes. Perhaps a specific working group should be formed to investigate and report more fully on this issue as the indications from the paper are that we are not making progress and that in fact tsetse control may actually be losing ground.
Drug management and parasite resistance in African animal Trypanosomosis
Profs. S. Geerts & P.Holmes
Trypanocidal drugs remain the principal method of control in most African Countries. However, there is growing concern that their future effectiveness may be severely curtailed by widespread drug resistance. Although the number of case reports on drug resistance is increasing, there is lack of reliable data at the regional and national level, on the true prevalence and impact of this resistance. In order to compare data on a temporal and spatial basis across Africa there is an urgent need for better standardisation of tests for the detection of drug resistance. The advantages and disadvantages of currently available assays are briefly reviewed and measures suggested to improve the situation. Guidelines are proposed to delay the development of drug resistance as well as measures which may be adopted to control resistance when it occurs. These measures include the avoidance of under-dosing; reducing the number of treatments and withdrawing the use of Quinapyramine for use with cattle.
The meeting agreed on the need for a more systematic approach to drug usage but emphasised that this was jeopardised by the lack of supervision and advice by governments in both their acquisition and administration.It was acknowledged that PAAT may provide the means to address the situation through the issuance of guidelines and through the direct contact of the international organisations in the secretariat with national veterinary services.
Concluding discussion of the session:
Open discussion of the above three papers in the PAAT Session of the ISCTRC resulted in the following conclusions:
The meeting noted the need to consider the overall effects of Trypanosomosis in the context of socio-economic impact at the rural development level and in terms of the evolution of sustainable mixed farming. It is indicated that very substantial gains could be expected from tsetse and Trypanosomosis control in mixed crop/livestock systems and that these areas should constitute the priority focus for control.
It was, therefore, concluded that PAAT should identify areas of agricultural potential, with high levels of rural population activity, that may form the focus for the programmes activities and which offered the greatest opportunities for success. These studies should also cover the benefits to be gained from improved human health and nutrition (see section 9).
In considering the use of artificial odour-bait techniques for tsetse control in East and Southern Africa the meeting noted with some concern that the total extent of such operations covered an area of only some 30 00 km. sq.
The achievements obtained from these activities varied from a 50% to a 99% reduction in tsetse populations.
In conclusion the meeting agreed that although the artificial bait techniques have a role to play they may not be appropriate to all situations. There was, therefore, a need to re-consider an integrated approach that may include previous proven techniques such as aerial and ground spraying.
Trypanocidal drugs remain the principle method of control in most African Countries. However, there is growing concern that their effectiveness may be severely curtailed by widespread drug resistance. There is a lack of reliable data on the prevalence and impact of drug resistance and the need for guidelines to help manage the problem were strongly recommended. These guidelines should take into account the measures needed to avoid underdosing, promote a reduction in the number of treatments administered and to advocate that quinapyramine be withdrawn from use in the treatment of cattle.
The meeting acknowledged the important and pivotal role of trypanocides in combating the disease across Africa and agreed that if efficiency was the primary objective then the practices of the past must be revised accordingly.
The social, economic and cultural implication of Trypanosomosis and it's control
Incorporating socio-cultural factors into tsetse control and assessment of its impact.
Dr. J. Ssennyonga
The paper reviews achievements and failures in four major areas. The first, capacity building is examined in terms of knowledge of tsetse biology and ecology, problems of tsetse and methods of solving them, the impact of control, community mobilisation, organisation and management. Evidence shows that not enough investment has been put into capacity building, especially organisation and management. The second issue, methodology, is examined in terms of choice of level and unit of analysis, participation parameters (PP), factors influencing participation (FIP) and the relationship between PP and FIP.
Evidence from literature shows that there is no consensus on PP and FIP, as a result evaluation of achievement is very difficult. Use of the group as the unit of analysis makes it impossible to explain participation at the individual level. The third issue, impact of tsetse control on common property resource use is examined in the context of the widespread conflicts over resource control and use in Africa. To the extent that tsetse control increases the value of resources in tsetse endemic areas, it also heightens the conflict over the control and use of those resources. The paper cites evidence of the occurrence of this phenomenon. the fourth issue, gender, is used to illustrate the three issues discussed. Findings, based on a case study, reveal there are both opportunities for and constraints against women participation.
The socio-economic and cultural impacts of Trypanosomosis and its control
Ms. D. Mwangi
The socio-economic importance of Trypanosomosis is difficult to assess, as the data available are fragmented and frequently only approximate. An investigation of the impacts of past outbreaks to a rural community in Kenya distinguished between direct and indirect impacts. A combination of qualitative methods and a formal household survey were used to collect data. The results indicated that residents in the areas where disease was prevalent attached greater social and economic importance to the disease. Direct effects of Trypanosomosis included: i) mortalities in both humans and livestock and a reduction in livestock production and ii) behavioral changes due to the fear of contracting sleeping sickness which affected normal social activities like visiting relatives, collecting firewood and fetching water. The consequences led to indirect effects including a reduction in family labour and household incomes. An important cultural impact was a shortage of animals for payment of dowry.
A comprehensive position paper on social implications needs to be prepared as this is a neglected area. The sociological aspects need to be considered separate from the economic ones in the PAAT. In these studies there is a need to attempt to predict the longer term effects particularly in view of the continuous changes to lifestyle and social development. Sustainability of tsetse control is a key issue and raises concerns over the dependability of communal participation, this needs to be addressed although it is appreciated that it may be affected by the system of this control.
Integrated Disease Management in Trypanosomosis control
Dr. B. Bauer
The live bait technique, as applied in Burkina Faso, is not intended to strongly suppress tick infestations but is primarily directed against tsetse. However, in certain circumstances there should be an association of insecticide treated artificial baits for more effective control of tsetse. However, the question then arises as to who should pay for these increased inputs. Sustainability and cost recovery schemes are largely dependent on the technique chosen, the insecticidal treatment of livestock being generally considered as the method of choice by the beneficiaries. Individual rationality, i.e. the live bait technique is likely to prevail over collective rationality (or public good) i.e. insecticide treated targets or traps.
Cost-recovery for the live bait technique is largely dependent on the simultaneous efficacy of a given product against ticks. Many pour-on formulations have sub-optimal dispersal and do not control ticks satisfactorily. Sustainability is dependent on a regular and affordable supply of the acaricides and/or insecticides sufficiently close to the demand. The use of GIS in conjunction with sound socio-economic analyses is a pre-requisite for the justification of priority actions in certain areas, tsetse control will remain as a patchwork for the foreseeable future in view of its extent and the lack of effective participation by the beneficiaries.
In order to assess the individual techniques more needs to be done in terms of producing a cost: benefit analysis. Integrating bait technologies generally gives 90%, or more, in terms of Trypanosomosis reduction. This approach may also have application in Sleeping sickness epidemics where livestock are becoming increasingly more important reservoirs. Concern was expressed over disrupting the enzootic stability of livestock to Tick borne disease, as has already been observed in Zimbabwe where 10 years of livestock treatment with deltamethrin has significantly lowered the prevalence of Babesia antibodies in cattle. It was generally agreed that where cattle are available in adequate numbers and distribution then the animal treatment seemed the most convenient and cost effective, however, there is need for more research to further define this potential.