W. MULATU, G.D.M. d'IETEREN, W. DUFFERA, T. GIRMA, P. ITTY, S.G.A. LEAK, J.H.H. MAEHL, S.M. NAGDA, R. W. PALING, J.M. RARIEYA, W. THORPE and J.C.M. TRAIL
The prevalence, species and intensity of trypanosome parasitaemias over an eighteen-month period, January 1986 to June 1987, are reported for some 700 East African Zebu cattle managed in ten village herds in four areas around Ghibe, S.W. Ethiopia. Tsetse relative density and trypanosome infection rates in tsetse were estimated over the same period. The cattle received systematic therapeutic treatments. The effects of trypanosome infection on PCV are reported and some preliminary performance results for these East African Zebu cattle are given. The research protocol was that of the ATLN (Murray et al., 1983). The Ghibe site has been described by ILCA (1986) and a summary is given in article 3 of these Proceedings.
Tsetse parameters
Only two tsetse species, Glossina pallidipes and G. fuscipes, were found during the study period. G. pallidipes was detected at a mean relative density of 3.7 and 1.6 flies/trap/day in Tolley and Ghibe/Abelti areas, respectively, while G. fuscipes was detected at a very low density in each area (Table 1). The mean trypanosome infection rate in tsetse was 6.2% at Tolley and 2.3% in Ghibe/Abelti. Tsetse challenge in Tolley was high in comparison with many other Network sites (Leak et al., see article 5 of these Proceedings).
Table 1. Species, mean relative density and trypanosome infection rate of tsetse flies in two areas of Ghibe.
|
Area |
Species |
Mean relative density (flies/trap/day) |
Mean trypanosome infection rate (%) |
|
Tolley
|
G. pallidipes |
3.7 |
6.2 |
|
G. fuscipes |
very low |
not estimable |
|
|
Ghibe/ |
G. pallidipes |
1.6 |
2.3 |
|
Abelti |
G. fuscipes |
very low |
not estimable |
Table 2. Mean monthly trypanosome prevalence and PCV of East African Zebu cattle in four areas of Ghibe, January 1986 to June 1987.
|
Area |
No.a |
Trypanosome prevalence % |
PCV |
||
|
Mean |
Range of herd means |
Mean |
Range of herd means |
||
|
Wonchib |
72 |
0.0 |
- |
29.7 |
- |
|
Ghibe |
384 |
18.8 |
14.4-24.3 |
26.6 |
25.4-27.5 |
|
Abelti |
98 |
19.9 |
18.7-20.6 |
26.5 |
26.3-26.8 |
|
Tolley |
131 |
22.0 |
11.1-32.2 |
26.4 |
24.2-28.9 |
b Number of animals tested per month. July 1986-June 1987.
Trypanosome infection in Fast African Zebu
Mean monthly trypanosome prevalences in the three areas with trypanosomiasis risk were 18.8, 19.9 and 22.0%, with large variation between herds in Tolley (Table 2). There was no marked seasonal effect on trypanosome prevalence (Figure 1). Pre-weaners (0-8 months) in all herds had lower trypanosome prevalences than post-weaners (9-36 months) which in most herds had lower trypanosome prevalences than adult female and male cattle (Table 3). Female physiological status and draught work did not affect trypanosome prevalence.
About 99% of parasitaemic months were single species infections, with 79% caused by T. congolense (Table 4). Pre-weaners had a higher proportion of parasitaemias resulting from T. vivax infection than other age classes. All age classes had similar mean parasitaemia scores, 2.4. Location, season and female physiological status did not affect the species of infection nor the mean parasitaemia score, which was higher in T. congolense and T. vivax infections than in T. brucei infections (Table 4).
Table 3. Mean trypanosome prevalence, PCV and percent depression of PCV in four age classes of East African Zebu cattle infected by trypanosomes.
|
Age class |
No.a |
Trypanosome prevalence (%) |
PCV % |
(%) depression of PCV by trypanosome infection |
|
0-8 mth |
45 |
7.0 |
29.7 |
25 |
|
9-36 mth |
164 |
15.4 |
27.1 |
18 |
|
Female, >36 mth |
240 |
19.5 |
26.5 |
18 |
|
Male, >36 mth |
164 |
26.3 |
25.0 |
17 |
a Average number of animals tested per month.
Systematic Berenil treatments were given when cattle were parasitaemic and had a PCV below 26%, or when trypanosomiasis was suspected from clinical symptoms. As a result 85.5% of the parasitaemias detected at the monthly samplings received Berenil treatments. Of the parasitaemic animals receiving a Berenil treatment, 23% had a parasitaemia detected at the next monthly sampling.
Table 4. Species and intensity of trypanosome parasitaemia in East African Zebu cattle.
|
Species |
No.a |
Mean |
Percent parasitaemia score | |
|
Single infection | ||||
|
|
T. congolense |
1690 |
79.3 |
2.4 |
|
|
T. vivax |
309 |
14.5 |
2.4 |
|
|
T. brucei |
109 |
5.1 |
2.0 |
|
Mixed infection | ||||
|
|
T. congolense |
19 |
0.9 |
2.2 |
|
|
T. vivax |
|
2.3 |
|
|
|
T. congolense |
4 |
0.2 |
(1.3) |
|
|
T. brucei |
|
|
(2.3) |
|
|
T. vivax |
1 |
<0.1 |
(1.0) |
|
|
T. brucei |
|
|
(1.0) |
|
Total |
|
2132 |
| |
a Number of parasitaemic animal-months.
Figure 1. Monthly trypanosome prevalence of Fast African Zebu cattle at trypanosomiasis risk, Ghibe.
PCV
Mean monthly PCV for the cattle at trypanosomiasis risk was 26.5%. There was little variation for mean PCV between the high trypanosomiasis risk areas (Table 1) but a large difference in mean PCV between those cattle at trypanosomiasis risk and those at Wonchi, the trypanosomiasis-free area. Trypanosomes were the only blood parasites which were detected frequently in this population. Internal parasites were not monitored regularly during the period reported. Age classes (Table 3), but not female physiological-status classes, showed differences for PCV. Pre-weaners had the highest PCV and lowest trypanosome prevalence, while adult males had the lowest PCV and highest trypanosome prevalence. Trypanosome infection depressed PCV by 5 percentage units (about 18%) in the older age classes and by 7.5 units (25%) in pre-weaners (Table 3). Preliminary analyses indicated that only pre-weaners had reduced growth rates in the month following a trypanosome infection, 160g/d compared to 193g/d.
Cattle liveweights and Liabilities
Table 5 presents liveweight and viability estimates. In this high trypanosomiasis risk environment performance was similar or better to that of the same breed at lower trypanosomiasis risk in a Network study at Muhaka, Kenya (Maloo et al., see article 29 of these Proceedings). Mean cow post-partum weight was 204 kg and mean calf weight at 12 months of age 86 kg (Table 5). Calf viability to 8 months of age was good, over 95%. Draught oxen were used for work on average 14 days/month and those cows milked gave nearly 1 litre/day.
Table 5. Liveweight and viability estimates of East African Zebu cattle at high trypanosomiasis risk.
|
Performance character |
No. of records |
Mean |
s.d. |
CV (%) | ||
|
Calf growth | ||||||
|
|
8 mth weight (kg) |
110 |
62 |
15.4 |
24.8 | |
|
|
12 mth weight (kg)a |
85 |
86 |
20.5 |
23.9 | |
|
Cow liveweight post-partum (kg) |
199 |
204 |
29.6 |
14.5 | ||
|
Viability (%) |
Recorded deaths |
All losses | ||||
|
|
Calf, birth to 8 mth |
100.0 |
95.2 | |||
|
|
Annual post-weaner (9-36 mth) |
99.2 |
94.2 | |||
|
|
Annual cow (>36 mth) |
98.3 |
91.8 | |||
a Records from the Wonchi area did not contribute to these estimates.
Despite a high trypanosome prevalence, about 20%, East African Zebu cattle, given systematic therapeutic treatment, had low mortality rates, reasonable liveweights and provided milk and draught power.
ILCA. 1986. The ILCA/ILRAD Trypanotolerance Network: Situation
Report, December, 1985. Proceedings of a Network Meeting held at ILCA, Nairobi. ILCA. Addis Ababa, Ethiopia.
Murray, M., J.C.M. Trail, D.A. Turner and Y. Wissocq. 1983. Livestock Productivity and Trypanotolerance. Network Training Manual. Addis Ababa: ILCA.
