ISRAEL JOURNAL OF
VETERINARY MEDICINE
VOLUME
55 (2) 2000
EFFECTS OF MANAGEMENT, SEASON, VEGETATION ZONE AND
BREED ON THE PREVALENCE OF BOVINE TRYPANOSOMIASIS IN
SOUTHWESTERN NIGERIA
A. O. Ogunsanmi1, B. O. Ikede2 and S. O. Akpavie
2
1. Department of Wildlife and Fisheries Management.
2. Department of Veterinary Pathology, University of Ibadan, Ibadan, Nigeria
Summary
Blood was examined to determine the prevalence of trypanosomiasis on 853 animals from 65
herds kept under modern and traditional management systems in the Ondo, Delta, Edo and
Kwara States of Nigeria. The herds were located either in the rain forest or the derived
savanna zones, which are the two ecological zones of Nigeria. A comparison of trypanosome
infection rates in abattoir blood samples with those of resident herds in these zones was also
carried out. The results indicated that sedentary management of cattle is associated with a
reduced trypanosome infection rate as compared to the semi-sedentary type of management.
The infection rates in sedentary and semi-sedentary herds were 9.8% and 42.8%,
respectively, while the rates in the rain forest and derived savanna were 6.6% and 19.9%,
respectively. The lower infection rates in the rain forest were attributed to increasing human
activity in reducing the habitat for the vector. On the other hand, the high infection rate in the
derived savanna was influenced by proximity to Glossina morsitans belt as well as to an
increasing density of animals and grazing activities. The infection rate of the N’Dama was
lower than those of Muturu, Keteku and Zebu breeds. The predominant species of
trypanosomes trapped in this survey were Trypanosoma congolense and T. vivax, while
Glossina palpalis and G. morsitans were the only trapped tsetse species. None of the tsetse
was positive for trypanosomes.
Introduction
Some of the factors that affect the prevalence of trypanosomiasis in Nigeria include animal
breed, type of management, season of the year and the type of vegetation. Ikeda et al. (1)
observed that some riverine and forest species of tsetse fly are poorer vectors of
trypanosomes than the savanna species. It is also known that nomadism tends to expose
animals to high tsetse challenge and hence trypanosome infection.
In Nigeria, cattle are considered as one of the principal livestock, and their survival and
development are necessary to ameliorate the worsening situation regarding the supply of
animal protein. Cattle production in the country has been restricted to the northern part (Table
1) because of the erroneous belief that the southern part (forest zone) was highly infected by
tsetse flies which transmit trypanosomiasis (2).
Table 1: Prevalence of bovine trypanosomiasis in Northern Nigeria (1952-1995).
Study State
(Location)
# of
Samples
Positive
Cases
No.
%
Trypanosome species number of all
infections
T.
T. congolense
T. brucei
vivax
Ref
Kwara
Benue
10
298
8
80
6
2
0
3
109
36.6
10
79
20
4
Kwara
110
46
42
29
8
9
5
Kaduna
210
16
7.6
16
0
0
6
Plateau
206
20
9.7
11
4
5
7
Benue
268
24
9.0
9
8
7
8
In order to understand the current status of trypanosome infection in southern Nigeria, this
study was undertaken to determine the prevalence of bovine trypanosomiasis in sedentary
and semi-sedentary herds resident in the derived savanna and rain forest zones during the
wet and dry seasons, to compare its prevalence among different breeds of cattle, and
measure the trypanosome infection rate in abattoir blood samples and observe the tsetse
population in the southwestern part of the country.
Materials and Methods
Animals
A total of 853 animals from 65 herds of cattle situated in different parts of Ondo, Delta, Edo
and Kwara States (southwestern Nigeria) were studied. Six hundred and sixty-six animals in
sedentary herds and 187 animals in semi-sedentary herds were examined. Sixty-one herds
were owned by traditional Fulari herdsmen who have settled in these areas for 3 to 10 years
or more. The other four herds were modern herds, which belonged to Government or private
owners. The breeds included Zebu, Muturu and N’Dama. The main preventive measure
against the fly, in herds under intensive management (sedentary herds), were traps and
screens (9). Due to the abundance of water and pasture during the rainy season, animals
were usually kept away from streams and rivers to reduce tsetse contact. There were no
preventive measures against the vector in extensively managed (semi-sedentary) herds.
Abattoir blood samples
Abattoir blood samples were obtained from four local Government abattoirs in Edo, Delta,
Ondo and Kwara States. A total of 138 blood samples were collected from animals
slaughtered at these abattoirs.
Collection blood samples
Animals were randomly selected from each herd as described by Putt et al. (10) and bled
from the jugular vein using anti-coagulant EDTA vacutainer tubes. Abattoir blood samples
were collected in universal bottles containing EDTA at slaughter from the severed jugular
vein. All the samples were kept on ice and taken to the laboratory for examination.
Packed cell volume and parasitaemia
The packed cell volume (PCV%) was determined (11). Trypanosomes were detected and
quantified in the blood samples by darkground/phase contrast buffy coat technique (DG) (12),
and species of trypanosomes identified (13).
Tsetse flies trapping, identification and examination
Flies were caught by biconical trapping (9). Tsetse species were identified according to
Murry et al. (13). Other biting flies were identified according to Davies (2).
Statistics
Data were statistically analyzed by Statistical Analysis System (14).
Results
The results of the trypanosome infection rates are shown in Tables 2 and 3. In the sedentary
herds, 9.8% of the 666 animals were positive while 42.8% of the 187 animals in the semisedentary herds were positive. This difference is highly significant (p<0.001) (Table 2). The
infection rate in the derived savanna zone was 19.8% and that of the rain forest zone, 6.6%
(p<0.001) (Table 3).
The results of the infection rates in the different breeds are presented in Table 4. The
N’Dama had an infection rate of 2.0% while those of Muturu, Keteku and Zebu were 16.0%,
18.5% and 19.7%, respectively (p<0.05).
Of all the animals examined, 17.0% were trypanosome positive, while T. congolense and
T. vivax accounted for 10.6% and 7.6% of the infections, respectively (Table 2).
Table 2: Managment system, trypanosome infection rates and tsetse
catches in southwestern Nigeria.
Positive
No. of cases
samples
No. %
Trypanosome
species
Glossina species
T.congolense T.vivax
G.palpalis G.Tachinoides Crysops Tab
Biting flies
Sedentary
herds
Dry
season
364
42 11.5c
16
16
0
0
3
Wet
season
302
23 7.6d
10
10
1
1
26
Sub total
666
65
9.8*
26
26
1
1
29
Dry
season
42
12 8.6b
9
9
9
12
10
Wet
season
145
68 46.9a
55
55
1
6
49
Semisedentary
herds
Sub total
187
80 42.8*
Grand
total
853
145 17.0
64
64
90 (10.6%) 65(7.6%)
10
18
59
11
19
88
Table 3: Ecological zones and trypanosome infection rates in southwestern
Nigeria.
Ecological No. of
zones samples
Positive
cases
No/
%
Trypanosome
species
Glossina species
Biting flies
T.
T.
G.
G.
Crysops Tabanids Hippob
congolense vivax palpalis tachnoides
Derived
savanna
672
133 19.8a
81
52
8
16
20
5
12
Rain
forest
181
12 6.6b
10
2
3
3
68
18
20
Total
853
145 17.0
91
54
11
19
88
24
32
The packed cell volume (PCV) values are shown in Table 4. The N’Dama had a mean PCV
of 30.2±1.9% while those negative for trypanosomes had a mean PCV of 33.0±2.3%
(p>0.05). The infected Muturu had a mean PCV of 36.3±1.9% while those negative for
trypanosome infection had a mean PCV of 37.1±2.4%. The trypanosome positive Keteku had
a mean PCV value of 21.3±0.6% while the negative had a mean PCV of 24.5±1.0% (p<0.05).
The positive Zebu had a mean PCV of 16.8±1.2% while the mean PCV for negative animals
was 25.6±1.8% (p<0.05). None of the 138 abattoir blood samples was trypanosome positive.
Table 4: Prevalence and mean PCV (%) of different breeds of trypanosomeinfected and non infected cattle in southwestern Nigeria.
Breed
DRY SEASON
Positive
cases
WET SEASON
Negative
cases
Positive
Negative
No.
cases
cases
(No.
Prevalence No. of
of
examined) Rate (%) samples
PCV
PCV cases
PCV
PCV
No.
No.
No.
No.
(%)
(%)
(%)
(%)
N'DAMA
(101)
2.0c
56
0
0
56
28.5+/1.8a
45
2
30.2+/33.0+/43
a
1.9
2.3a
MUTURU
(25)
16.0b
8
0
0
8
34.6+/2.2b
17
4
36.3+/37.1+/13
a
1.9
2.4a
KETEKU
(318)
18.5a
168
38
21.3+/24.5+/130
150
b
0.6
1.0a
17
25.3+/25.5+/133
a
0.4
2.2a
ZEBU
(426)
19.7a
191
17
16.8+/25.6+/174
235
c
1.2
1.8a
68
22.4+/26.6+/167
b
1.6
0.8a
Thirty tsetse flies, 11 Glossina palpalis and 19 G. tachinoides, were caught, while 21 (70.0%)
and 9 (30.0%) tsetse were trapped during the dry and wet seasons, respectively. In addition,
24 (80.0%) tsetse were trapped in the derived savanna zone and the other 6 (20.0%) were
caught in the forest zone. None was positive for trypanosomes. Other biting flies caught were
88 Tabanus, 23 Chrysops and 320 Hippobosca species.
Discussion
The results of this study indicate that sedentary management of cattle is associated with a
reduced trypanosome infection rate compared to semi-sedentary management. This
observation agrees with that of MacLennan (15) who also observed that the innate resistance
of cattle was increased by repeated exposure to the same population of trypanosomes in a
given area. The semi-sedentary herds are continuously exposed to new strains of
trypanosomes while other adverse husbandry stress factors predispose them to increased
susceptibility and high infection rate.
In the sedentary herds, the relatively high infection rate observed during the dry season
might be due to higher animal and tsetse contact resulting from the concentration of the flies
on riverbanks where there was green pasture and access to drinking water (15). The lower
infection rate in the wet season may be as a result of the reduced animal and tsetse contact,
abundance of pasture and water, coupled with reduced stress factors.
The higher infection rate observed in the wet season in the semi-sedentary herds might be
associated with a high tsetse risk at the cattle range. The cumulative effects of exposure to
tsetse and new strains of trypanosomes in this season probably account for the observed
infection rate (15).
The results of this study indicated differences in trypanosome infection rates in the different
ecological zones. The low infection rate in the rain forest zone is likely to be due to increasing
human activity in this zone and the presence of few effective vectors. The high trypanosome
infection rate in the derived savanna zone could be linked to its proximity to the morasitans
belt.
The resistance of the N’Dama to trypanosome infection was superior to that of Muturu,
Keteku and Zebu breeds. The trypanotolerance of the N’Dama is well known (16, 17). The
relative resistance of Muturu and Keteku has also been reported (18, 19, 20).
The predominant species of trypanosomes encountered were T. congolense and T. vivax.
Davies (2) attributed the predominance of T. congolense to the fact that drugs used in
Nigeria are better at curing T. vivax infections than those of T. congolense. Single infections
of T. congolense or T. vivax were encountered more frequently than mixed infections.
The PCV is the most reliable indicator of anaemia in trypanosomiasis (21,22). In this study,
there were no significant differences between the PCVs of infected and non-infected N’Dama
and Muturu during the wet season. The reason might be partly due to the high nutritional
status and their relative trypanotolerance.
The low PCV values of the Keteku and Zebu is in agreement with previous findings (23, 24)
who reported that trypanosomiasis caused depressed PCV levels in infected animals. All four
breeds, infected or not, had slightly higher PCV values in the wet season than in the dry
season. This may again be related to seasonal nutritional variations.
Glossina palpalis and G. tachinoides were the most widely distributed species of tsetse flies
in the area studied. None of the dissected tsetse was positive for trypanosomes. The low
infection rates of tsetse could explain the low prevalence of trypanosomiasis observed in the
study area, especially in the rain forest zone. The study revealed that fewer tsetse were
caught compared to the number of biting flies which act as mechanical transmitters of
trypanosomes while the epidemiology of animal trypanosomiasis has not been clearly defined
(25, 26).
The absence of trypanosomes in the abattoir blood samples examined in this study could be
due to the faster and modern mode of transportation of trade cattle from the northern to the
southern cattle markets (27). This has helped to reduce the incidence of tsetse and cattle
contact as well as reduce the stressful effect of trekking, both of which normally result in
higher trypanosome infection rates.
In conclusion, the findings of this study and of previous workers (1, 28) have shown that
trypanosomiasis may not be serious limiting factor to livestock production in sedentary cattle
herds. We are therefore of the opinion that an intensive commercial production of Zebu
breeds coupled with good management could be encouraged in southern Nigeria.
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