Proceedings of the 3rd International Symposium on Veterinary Epidemiology and Economics, 1982
Available at www.sciquest.org.nz
TRYPANOSOMIASIS IN ETHIOPIA
Zelleke Dagnatchew*
Trypanosomiasis is an important disease of both man and his livestock in
Ethiopia. The human trypanosomiasis is limited only to south-western
administrative regions in distribution. The animal trypanosomiasis on '
About 10
the other hand, is widely spread throughout the country.
million cattle are affected or at risk of infection at any one time.
The trypanosomes are transmitted by cyclical or acyclical means. Most
of the infection is transmitted mechanically by biting flies other than
Glossina species.
The cyclical vectors, i.e. Glossina species (tsetse flies) occupy a vast
area of arable land in the lowlands of Ethiopia. This land has been
calculated to be about 98,000 km. This land cannot be used for a
settlement scheme unless the tsetse flies and the disease which is
transmitted by them are controlled.
The highlands of Ethiopia, on the other hand, are overcrowded. This
resulted in smaller ownership of land, intensive farming, overgrazing
and soil erosion, whose sum-total effect is impoverishment of the land.
Trypanosomiasis in Ethiopia could be controlled by mass treatment in
areas of mechanical transmission and by a combined action of insecticide
application and meticulous alteration of the tsetse fly habitat. At the
moment about 1 million heads of livestock are receiving treatment
annually.
Animal Trypanosomiasis
Trypanosomiasis of livestock, known as Ghendi in Ethiopia, is one of the
major diseases of livestock. This disease is found throughout Ethiopia
with the exception of the highlands where it is very rare or even
absent. Langridge (1976) has calculated the number of cattle which are
affected by nagana, plus those which are at high and low risk of nagana
infection to be 305,000; 1,261,000 and 8,801,000 respectively. In other
words over 10 million heads of cattle are vulnerable to the disease.
The Central Statistical Office (1972) has indicated that there are about
26 million cattle. From this, it can be calculated that about 38.5% of
the national herd of cattle is vulnerable to trypanosomiasis at any one
*Trypanosomiasis Control Services, P.O. Box 241, Debre Zeit, Ethiopia
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Proceedings of the 3rd International Symposium on Veterinary Epidemiology and Economics, 1982
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time. Therefore, the economic loss which follows decreased productivity
and death of livestock is enormous.
Apart from this direct economic loss, a vast area of arable land cannot
be utilized for agricultural purposes due to fear of trypanosomiasis and
other diseases such as malaria.
Another point which should be mentioned here is that trypanosomiasis
contributes its share as a factor for the shortage of animal protein in
the world. This, of course, can be attributed to its direct and
indirect results of decreased productivity and death of livestock and
incapability of utilizing fertile land for agricultural purposes,
respectively.
Human Trypanosomiasis
Human trypanosomiasis was not known to exist in Ethiopia until 1967,
when Dr. Marion of the Presbyterian Mission discovered the existence of
sleeping sickness in Maji, Keffa administrative region (Baker et al.
1969). From 1967-1970 there was an outbreak of sleeping sickness in
Gambella province, Illubabor administrative region in which the disease
is believed to be endemic (Hutchinson 1971).
Hutchinson (1971) has also indicated that there was a possible case of
sleeping sickness in 1969 just south of Lekemte which is the main town
of Wollega administrative region. Another case of the disease was also
reported in 1980 in Mursi-Bodi district in Gamo Goffa administrative
region (Olafsson et al. 1981).
All these reports indicate that the disease appears to be so far
restricted to the tsetse infested areas of the south-western regions of
Ethiopia, particularly in the province of Gambella. Since communications by roads is very poor in this part of the country, adequate
surveys of the disease has not yet been possible. Hence a serious study
has to be conducted in the future on human trypanosomiasis in Ethiopia
to find out the extent of its distribution and the magnitude of the
problem.
Species of Trypanosomes Found in Ethiopia
There are six pathogenic species of trypanosomes which are discovered in
Ethiopia, namely Trypanosoma vivax, T. congolense, T. brucei, T. evansi,
T. equiperdum, and T. rhodesiense.
But the most important trypanosomes in the country are T. vivax and T.
congelense. Both species affect a great number of cattle which are the
most important species of the domestic animals in Ethiopia. Due to its
extensive distribution, T. vivax is more important than T. congolense.
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Proceedings of the 3rd International Symposium on Veterinary Epidemiology and Economics, 1982
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Distribution of the Trypanosomes
Most of the above listed species of trypanosomes are limited in distribution to Africa which is the home of the cyclical vector. But the
mechanically and venereally transmitted trypanosomes have a cosmopolitan
distribution.
In this paper, their geographical distribution in
Ethiopia will be the main concern.
Trypanosoma vivax: is found in the entire country except in the high
lands, which are 2500 meters above sea level. The highlands include:
The North Central and the Arsi-Bale Massiffs; the Tigrean Plateau, the
Showan Plateau, the South-Western Plateau, and the Harar Plateau. The
wide spread of T. vivax is due to its adaptation to mechanical transmission by biting flies in areas outside tsetse fly belt.
The distribution of T. congolense, and T. brucei, have been limited
nearly to the area of the cyclical vector namely the Angherib, the Baro,
and the Omo lowlands. This is due to the fact that both species of trypanosomes are not adapted to acyclical transmission. Therefore, the
diseases which are caused by T. congolense and T. brucei are limited to
that is Sidamo, Gamo
southern and western administrative regions:
Goffa, Keffa, Illubabor, Wollega, Gojjam, and Shoa.
The distribution of T. evansi coincides with the distribution of camels
in Ethiopia (Langridge 1976). Therefore surra is found in the Barka and
Angherib lowlands; in the Ghenale, Shebelle, Awash and Coastal plains;
and in the Afar Depression.
Trypanosoma equiperdum has been recently discovered in the Arsi-Bale
Massifs (Zelleke et al. 1980), where there are a significant number of
equines. This makes dourine an important disease in the area.
VECTORS OF TRYPANOSOMES IN ETHIOPIA
Mammalian trypanosomiasis can be transmitted from an infected animal to
healthy ones cyclically or mechanically. The sole cyclical vectors of
trypanosomiasis are the species of Glossina, which are commonly known as
tsetse flies. The acyclical transmission of the disease is effected by
means of blood sucking flies which include Glossina, Tabanus,
Haematopota, Chrysops, Hippobosca, and Stomoxys species. The Vampire
bats have been proven to transmit surra in Latin America (Hoare 1972).
Although the mechanical vectors are widely distributed and transmit the
most important trypanosome (T. vivax), the cyclical vectors are much
more important. Because, as long as the tsetse flies are existing, it
would be very difficult to eradicate the disease from the country.
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Impact of Tsetse Flies on Land Utility
Landridge (1976) has worked out the total area which is infested by the
cyclical vector of nagana to be about 98,000 km 2 . Therefore, about 8%
of the total area is estimated to be infested with tsetse flies.
Although it requires soil analysis and detailed studies of other
conditions including the climate, this vast area is suitable for agricultural purposes including livestock industry.
This vast area of arable land is found in southern and western Ethiopia
under 1700 m. in altitude. Whereas people are dwelling in an over
crowded manner on the highlands. For instance, the Central Statistical
Office (1978) has indicated that the population densities of Wolayta,
Kembata and Hadia, Dessie-Zuria, Sidama, Hamasien, Adwa, and Kalu
provinces are 232, 183, 151, 137, 134, 129 and 116 people per Km2.
respectively. The average size of land ownership in these provinces,
therefore, varies from 0.4 to 0.9 hectars per head. The over-crowding
results, not only in small piece of land ownership, but also due to
intensive farming coupled with poor management of farms and,
overgrazing, the soil has been impoverished by soil erosion.
The Central Statistical Office (1978) has also indicated that the population densities of Ghimira, Chilga, Gambella, Metekel, and Arero provinces are 9, 9, 4, 4, and 3 people per Km 2 . respectively. In these
provinces, the average land holdings vary from 11-33 hectars per head.
An individual peasant farmer is entitled to have 10 hectars of land by
proclamation (Provisional Military Administration Council 1975). This
indicates that there is a lot of land which is under utilized in the
lowlands. Therefore, were it not for trypanosomiasis and other
diseases, the overcrowding problem of people and their livestock on the
highlands would have been alleviated by carrying out settlement schemes
in the lowland.
Glossina Species Which are Found in Ethiopia
It is believed that six Glossina species used to be existing in
Ethiopia. But recent work by Langridge (1976) shows that Glossina
brevipalpis could not be found in Ethiopia, even in the lower Omo Valley
where it was reported previously. With the reduction of this species,
there are now only five species of Glossina in Ethiopia, namely Glossina
(G) morsitans, G. pallidipes, G. fuscipes, G. tachinoides, and G.
longipennis.
Distribution of the Glossina Species in Ethiopia
Langridge (1976) has also worked out the distribution of the five
species of Glossina listed above. According to this work, seven of the
14 administrative regions of Ethiopia are infested with one or more
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Proceedings of the 3rd International Symposium on Veterinary Epidemiology and Economics, 1982
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species of Glossina to a lesser or greater extent. The administrative
regions which are affected by Glossina species include Sidamo, Gamo
Goffa, Illubabor, Keffa, Wollega, Gojjam and Shoa.
The distribution of the Glossina species follows the major drainage
systems of the Blue Nile, Baro, Akobo, Omo, and a few of the Rift Valley
lakes. Since basins of the major rivers of Ethiopia are separated by
highland areas which act as natural barriers, there is no apparent
spread of Glossina species from one system of drainage to another.
Ford et al. (1976) mentioned in their report to the government of
Socialist Ethiopia that Glossina longipennis, G. brevipalpis, G.
pallidipes and G. austeni are found in the Juba Valey lower down in the
Somali territory about 400 km. away from the Ethiopian border. Although
the reason is obscure, it appears that G. longipennis has disappeared
from the Ghenale Basin. Nevertheless, there is a possibility of
advancement or incursion of some of the flies to the Ethiopian territory
in the future.
CONTROL OF TRYPANOSOMIASIS IN ETHIOPIA
To promote animal protein production in Africa at large and in Ethiopia
in particular; to alleviate the problem of over crowding of both people
and livestock in the Highlands; and to improve the fertility of soil
which as been impoverished as a result of soil erosion through mismanagement of farms and overgrazing in the highlands, animal trypanosomiasis should be controlled.
Control of Trypanosomiasis
To control the disease satisfactorily, it requires the development of a
suitable system. In the tsetse areas, prophylactic treatments should be
given at certain intervals. In tsetse free zones, curative mass treatments should be given to relevant animals. This should be coupled with
trypanosomiasis surveillance and control of livestock movement
especially from tsetse areas to the highlands. Sources of infection
from the wild fauna should be arrested. By and large, aside from the
methods mentioned above, the disease could also be suppressed by implementing improved husbandry and management and by selecting breeds of
domestic animals which are more resistant to the disease.
The Ethiopian government has initiated a programme of treatment against
trypanosomiasis by using chemotherapy and chemoprophylaxis. The drugs
which are used for this purpose are isometamidium and diminazene
aceturate in bovines, and suramin and quinapyramine sulphate in equines
and camelines.
The National Revolutionary Development Campaign and Central Planning
(1978/79, 1979/80, 1980/81) has setup a yearly target for treatment of
livestock against trypanosomiasis.
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Proceedings of the 3rd International Symposium on Veterinary Epidemiology and Economics, 1982
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Table 1. Livestock Treatment Against Trypanosomiasis.
Fiscal Year
1978/79
1979/80
1980/81
Target
495,070
1,400,000
700,000
Achievement
414,000
952,100
854,000
84
68
122
% achieved
a The campaign started late in the Ethiopian fiscal year of 1978/79.
Hence the target and achievement show only for the last 6 months of the
fiscal year.
From the above table, it can be seen that a number of livestock were
treated from 1978/79 to 1980/81. The treatments were given weekly at
treatment centers and veterinary clinics where the disease prevails. In
addition to this, treatments were given in coordination with rinder-pest
and contagious bovine pleuro-pneumonia vaccination campaigns and disease
investigation programmes. The interval of treatment for each animal is
unknown.
Control of the Cyclical Vectors
The cyclically transmitted trypanosomes present a problem only in the
area of tsetse belt except T. vivax which covers almost the entire
country.
Here the best policy would be to attack the tsetse flies and the disease
at the same time. The control of tsetse could be launched by taking
active measures against them directly or indirectly. There are a number
of methods of tsetse control which have been put forward by various
authors.
All these methods are not equally practicable in Ethiopia. Therefore,
it would be indispensable to select only a few of the methods and employ
them in the control measures to be taken against the tsetse flies.
The selection of the methods should be based on detailed and systematic
studies of the tsetse ecology in Ethiopia from all angles. But some
experts have already recommended to start the control measures of the
tsetse flies by a combined action of insecticide application and partial
clearing of vegetation (Ford et al. 1976).
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Proceedings of the 3rd International Symposium on Veterinary Epidemiology and Economics, 1982
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Control of Mechanical Vectors
Since most of the biting flies other than tsetse are ubiquitously distributed and numerous in population in both the lowlands and the highlands, it is very difficult to control them.
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Central Statistical Office. 1972. Statistical Pocket Book,
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Central Statistical Office. 1978. Ethiopia, Statistical Abstract,
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Ford, J., Makin, M.J. and Grimble, R.J. 1976. Trypanosomiasis
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Hoare, C.A. 1972. The trypanosomes of mammals. Black-well
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Hutchinson, M.P. 1971. Human trypanosomiasis in Ethiopia.
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Langridge, W.P. 1976. A tsetse and trypanosomiasis survey of
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National Revolutionary Production and Cultural Development Campaign
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NRPCDC. 1973 E.C. Third Year Plan (Amharic ed.), Addis Ababa. 96.
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Olafsson, J. and Aarsland, A. 1981. Ethiopian Med. J. 19, 31.
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Provisional Military Administration Council (PMAC). 1975. Public
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*E.C. stands for Ethiopian calendar which starts in September and it is
less by 7 or 8 years than the Gregorian calendar. For instance 1972
E.C. would be 1979/80 G.C.
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