Over
the past fifty years the number of reported cases of human sleeping sickness in Kenya has
never exceeded 500 a year, and since 1968 there have been fewer than one hundred cases
reported each year. Whilst there is likely to be some under-reporting of sleeping
sickness, these figures pale into insignificance compared with those for malaria, HIV/AIDS
and road traffic accidents.Animal rather than human
trypanosomosis is the primary cause for concern. However, trypanocides are estimated to
account for only about 7% of the total veterinary drug market in Kenya (US$1.9 million out
of a total US$26.5 million), with an estimated 50% of total expenditure going on
acaricides.
Four sites were selected for investigation by staff of the
Kenya Trypanosomosis Research Institute (KETRI): Busia and Olambwe are densely populated,
with a relatively high rainfall and a history of human sleeping sickness. Galana and
Nguruman are thinly populated and are much drier, with limited potential for arable
farming. Galana lies to the east of Tsavo National Park, and is managed as a state owned
cattle ranch. Nguruman is a transhumant pastoral production system in the southern rift
valley, west of lake Magadi.
Case Study Characteristics
| Name |
Busia |
Galana |
Nguruman |
Olambwe |
| Land Area |
1,700 km2 |
6,000 km2 |
600 km2 |
1,400 km2 |
| Annual Rainfall |
750-2,000 mm |
400-600 mm |
400-600 mm |
1,000-1,400 mm |
| Agro-climatic Zone |
Mainly I & II; some III & IV |
IV and V |
IV and V |
Mainly IV |
| Protected Areas Nearby |
None |
Adjacent to Tsavo East National Park |
Magadi Concession, Lake Natron |
Ruma National Park is centrally located |
| Farming Systems |
Mixed |
Commercial Ranch |
Pastoral Group Ranch |
Mixed |
| Human Density 1989 |
230 km-2 |
<1 km-2 |
5 km-2 |
110 km-2 |
| Cattle Density 1996 |
87 km-2 |
2 km-2 |
15 km-2 |
50-75 km-2 |
| Tsetse Species Present |
G.f. & G.p. |
G.p., G.b. & G. l. |
G.p. & G.l. |
G.p. |
| Dry Season Infestation |
10-20% |
25-33% |
<10% |
<10% |
| Form of Disease |
Animal & Human |
Animal |
Animal |
Animal & Human |
| Disease Control Measures |
Ground Spraying, Bush Clearance,
Trypanocides, Community Trapping, and Pour-on |
Trypanocides, Targets and Pour-on |
Trypanocides, Community Trapping, and
Pour-on |
Settlement, Ground Spraying, Bush
Clearance, Trypanocides and Community Trapping |
The
case studies demonstrate wide-ranging and cumulative impacts of human population growth,
agricultural expansion and economic development on the environment, including loss of the
natural habitats and hosts of tsetse. These findings are broadly in line with those of
other studies of environmental change associated with trypanosomosis control in Nigeria
and Zimbabwe. An important distinction, however, is that the Kenya case studies were
selected to reflect a range of environmental conditions, farming systems and
epidemiological circumstances, including densely populated mixed farming areas with a
history of sleeping sickness, and semi-arid rangelands. Assessments of change in the
Kenyan studies have also been over a substantially longer period of time, going back to
the turn of the century, and are based on a combination of air-photo interpretation,
participatory rural appraisal and historical review.
With the continued growth of Kenya's human population and
mounting pressure on limited land resources, future development priorities must focus on
the intensification of agricultural production, and measures capable of achieving greater
productivity in the context of existing farming systems.
Human sleeping sickness no longer ranks as a disease of
major importance in Kenya, compared for instance with malaria, or HIV/AIDS. Trypanosomosis
in animals, however, is common, and a constraint on livestock production in many areas. It
is also a constraint on the use of draught power and, thus, limits the potential for
intensification of agricultural production.
The relative importance of trypanosomosis, compared with
other livestock diseases and other constraints on production (e.g. fodder, water,
management and finance) is difficult to assess. This is because of a general lack of
reliable up to date information about the incidence of major diseases and associated
production losses in different parts of the country. Recent attempts to quantify livestock
production by system have gone some way towards this aim, but have been hampered by
unreliable population figures and limited disease incidence data. Such information is of
paramount importance for strategic planning. A national survey of livestock diseases,
including an assessment of the relative importance of trypanosomosis, is required.
An array of measures are available for controlling animal
trypanosomosis, ranging from vector control by traps and targets, to the use of
trypanocidal drugs, and the application of pour-on insecticides. Compared with those
associated with ongoing expansion of agriculture and rural development, the direct impact
on the environment of these methods is marginal.
The reality of the situation in Kenya today is that
producers make decisions about livestock management and disease control, based on
information and products available, their relative costs, and other calls on limited
household income and labour. If disease control measures are too expensive, too time
consuming, or too complex for the benefits perceived, they will not be adopted.
Studies by KETRI staff at Nguruman suggest that the cattle
of Maasai transhumant pastoralists in the southern rift valley get by on an average of one
trypanocidal drug treatment per animal per year, costing about US$1. Clearly, alternative
methods of disease control must be highly effective to compete with this.
Given the importance of wildlife and tourism to the Kenyan
economy, the problem of tsetse and trypanosomiasis control within and around National
Parks and other protected areas demands particular attention. In years to come, many of
these areas will be surrounded by agricultural land and human settlement (as some are
already) and will be threatened by encroachment, unless local communities see some benefit
from their continued existence.
Kenya Wildlife Service has adopted a policy of encouraging
community participation in wildlife conservation and the integrated development of
peripheral buffer zones around protected areas. Such initiatives should include strategies
for the control of trypanosomosis and other diseases of livestock and wildlife. Successful
interventions of this kind, leading to the long-term co-existence of people, livestock and
wildlife, would have relevance far beyond Kenya's national boundaries.
NB, These case studies were subsequently
included in a more wide ranging assessment of Environmental
change and the autonomous control of tsetse and trypanosomosis in
sub-Saharan Africa.
