S. NGAMUNA, G.D.M. d'IETEREN, P. ITTY, S.G.A. LEAK, J.H.H. MAEHL, M. MINENGU, S.M. NAGDA, R. W. PALING, J.M. RARIEYA, W. THORPE and J.C.M. TRAIL
The prevalence, species and intensity of trypanosome parasitaemia over an eighteen-month period, February 1986 to July 1987, are reported for some 700 N'Dama cattle managed in twenty-five village herds in forest and plateau areas of Idiofa, Zaire. The cattle were kept under the metayage system. Tsetse challenge was estimated over the same period in the two areas and its relationship to trypanosome prevalence examined. The duration of infection, the pattern of parasitaemia and the effects of trypanosomiasis and other diseases on PCV are reported. Preliminary performance data for these N'Dama cattle are also given. A description of the site has been given by ILCA (1986) and in article 3 of these Proceedings. The research protocol used was that of the ATLN (Murray et al., 1983).
Tsetse parameters
Two tsetse species were detected, G. fuscipes and G. tabaniformis, the latter only in the forest and at a relatively low density but high infection rate (Table 1). Tsetse challenge and trypanosome prevalence in cattle were higher in the forest than in the plateau, and both parameters were low relative to most Network sites (d'Ieteren et al., see article 10 of these Proceedings). Most parasitaemias in cattle (over 90%) were caused by T. congolense, corresponding to the major infection type in G. fuscipes, but contrasting with the high percentage (77%) of "vivax-type" in the forest tsetse (Table 1). The high proportion of "congolense-type" infections in G. fuscipes in the plateau area is unusual, as this tsetse species is not a good vector of T. congolense. This species took a high proportion of feeds (45%) from suids which are usually reservoirs of T. congolense (Table 2).
Table 1. Mean tsetse population parameters and related cattle parameters, February 1986 to July 1987.
|
Parameter |
G. tabaniformis |
G. fuscipes |
|
|
Forest |
Forest |
Plateau |
|
|
Tsetse relative density (fly/trap/day) |
0.1 |
2.5 |
2.3 |
|
Trypanosome infection rate (%) |
6.4 |
0.9 |
0.5 |
|
Tsetse challenge (density x infection rate) |
2.7 |
1.2 |
|
|
Trypanosome prevalence in cattle (%) |
4.6 |
1.4 |
|
|
Proportion of total infections |
0.86 |
0.77 |
0.75 |
|
in tsetse by major type |
vivax |
vivax |
cong. |
|
Proportion of monthly Trypanosome |
0.91 |
0.96 |
|
|
parasitaemias in cattle by major species |
congolense |
congolense |
|
Table 2. Results of blood meal analysis for G. fuscipes.
|
|
Warthog |
Man |
Domestic pig |
Bushpig |
Cattle |
Monkey |
Negative |
|
Number |
12.0 |
11.0 |
10.0 |
7.0 |
4.0 |
3.0 |
18.0 |
|
Percent |
17.5 |
16.9 |
15.4 |
10.8 |
6.2 |
4.6 |
27.7 |
Total number of blood meals tested = 65.0
Percentage of feeds taken on cattle = 6.2
Percentage of feeds taken on suids = 44.6
Trypanosome infection in N'Dama cattle
Mean monthly Trypanosome prevalence was 2.9% in the total study population, 4.6% for the cattle in the forest areas and 1.4% for the plateau cattle. Location within the forest area also affected Trypanosome prevalence (Table 3). There was no effect on Trypanosome prevalence of season (Figure 1), animal age or female physiological status (lactating, dry/gestating, empty).
Over 90% of parasitaemic months resulted from T. congolense infections, 5% from T. vivax and 2% from T. brucei. Less than 1% were mixed infections. Neither area, age class nor female physiological status affected the species of infection, nor the parasitaemia score of T. congolense infections which averaged 2.4. Table 4 shows the duration of T. congolense infections and the pattern of parasitaemia. If a parasitaemia was preceded or followed by two months with no detectable parasitaemia then it was termed an infection. In these N'Dama cattle, which received few therapeutic treatments, a high proportion of T. congolense infections (76%) were parasitaemias detected in a single month, while 21% covered two or three months. The short duration of T. congolense parasitaemias, in the absence of therapeutic treatments, indicates the self-cure capabilities of this N'Dama population. Very similar results were found in N'Dama cattle at Mushie Ranch, Zaire (Table 5).
Table 3. Mean monthly trypanosome prevalence and PCV of N'Dama cattle in villages within the forest and plateau.
|
Area |
Village |
No.a |
Trypanosome prevalence (%) |
PCV (%) |
||
|
Mean |
Range of herd means |
Mean |
Range of herd means |
|||
|
Forest |
Itunda |
94 |
7.4 |
6.4-7.5 |
33.3 |
31.6-34.7 |
|
Bushongo |
71 |
5.0 |
4.3-5.6 |
34.3 |
33.4-35.2 |
|
|
Mwilambongo |
185 |
3.0 |
0.0-8.3 |
34.7 |
32.1-40.7 |
|
|
Plateau |
Intswam/Busongo |
197 |
1.5 |
0.0-3.2 |
36.3 |
35.6-38.0 |
|
Ifwanzondo |
161 |
1.4 |
0.4-2.4 |
34.8 |
34.5-35.3 |
|
a Average number of animals tested per month.
Figure 1. Monthly trypanosome prevalence of N'Dama cattle in the Forest and Plateau areas of Idiofa.
Table 4. Duration of T. congolense infectionsa and the pattern of parasitaemia in N'Dama cattle.
|
Period of infection, months |
Pattern of parasitaemiab |
No. of infections |
Proportion |
|
1 |
- - C - - |
188 |
0.76 |
|
2 |
- - C C - - |
27 |
0.11 |
|
3 |
- - C - C - - |
15 |
0.10 |
|
|
- - C C C - - - |
10 |
|
|
4 |
- - C C - C - - |
1 |
0.01 |
|
|
- - C C C C - - |
1 |
|
|
5 |
- - C - C C C - - |
2 |
0.02 |
|
|
- - C C C - C - - |
2 |
|
|
6 |
- - C - C C - C - - |
1 |
0.01 |
|
|
- - C C C C C C - - |
1 |
|
|
Total |
|
248 |
|
a Two non-parasitaemic months preceding or following a parasitaemic month define the limit of an infection.b No parasitaemia detected in monthly blood sample.
c T. congolense detected in monthly blood sample.
Table 5. Duration of T. congolense infections in N'Dama cows and calves under ranch and village management with no therapeutic treatments.
|
Duration of infection, months |
Mushie Ranch |
Idiofa Villages |
|
|
Calves |
Cows |
Cattle |
|
|
1 |
0.78 |
0.75 |
0.76 |
|
2 or 3 |
0.19 |
0.19 |
0.21 |
|
4 or more |
0.03 |
0.06 |
0.03 |
|
Total number of infections |
100 |
473 |
248 |
PCV
Mean monthly PCV for the total population was 34.9%, with some variation between areas (forest 34.2%, plateau 35.6%) and large variation between herds (31.6 to 40.7%) (Table 3). Trypanosome infection consistently depressed PCV. In the forest area the average depression was 2.4 percentage units (7.0%) and in the plateau area 2.6 percentage units (7.3%). Strongyle egg burden and coccidia were common in pre-weaners and post-weaners but had little effect on PCV whether present individually, together or in animals infected with trypanosomes (Table 6).
Table 6. Mean PCV (%) of N'Dama cattle with and without a strongyle egg burden while infected or not infected by trypanosomes.
|
Strongyle egg burden |
Trypanosome infection |
Diff. |
% |
|||
|
No.a |
Negative |
No. |
Positive |
|||
|
Absent |
3078 |
35.4 |
85 |
32.9 |
2.5 |
6.9 |
|
Present |
1719 |
35.0 |
81 |
32.6 |
2.4 |
6.9 |
|
Diff. |
|
0.4 |
|
0.3 |
|
|
|
% |
|
1.0 |
|
1.1 |
|
|
a No. of animal-months.
Liveweights and viabilities of N'Dama cattle
Mean post-partum weight of N'Dama cows in this population was 232 kg, and mean calf weights at 8 and 12 months were 88 and 105 kg, respectively (Table 7), lighter than the corresponding weights of N'Dama cattle on well-managed ranches in Zaire (Feron et al., see article 24 of these Proceedings).
Table 7. Liveweight and viability estimates of N'Dama cattle in village herds in the Idiofa area.
|
|
No. |
Mean |
s.d. | |
|
Calf liveweights (kg) | ||||
|
|
8 months |
149 |
88 |
24.4 |
|
|
12 months |
86 |
105 |
31.3 |
|
Cow liveweight (kg) | ||||
|
|
Post parturition |
325 |
232 |
42.4 |
|
Viability (%) | ||||
|
|
Pre-weaner (0-8 months) |
|
98.1 |
|
|
|
Annual post-weaner (9-36m) |
|
96.3 |
|
|
|
Annual adult (>36 months) |
|
99.3 |
|
Neither a strongyle egg burden nor the presence of coccidia depressed pre-weaner or post-weaner growth. Pre-weaner growth was not affected by a trypanosome infection, but post-weaner growth was reduced by some 35%.
During the 18 months of this study, viability rates of the pre-weaner, post-weaner and adult N'Dama were low (Table 7) and similar to the rates observed for the N'Dama ranch cattle in Zaire (Feron et al., see article 24 of these Proceedings).
These preliminary results on the health and performance of N'Dama cattle managed in village herds at trypanosomiasis risk are a good illustration of the trypanotolerance of the N'Dama. The continued sequential recording of monthly tsetse parameters and cattle health and production data will, in addition, give estimates of N'Dama reproductive performance. These will provide information on which to evaluate factors including trypanosomiasis affecting N'Dama productivity in the metayage system.
ILCA, 1986. The ILCA/ILRAD Trypanotolerance Network. Situation Report, December 1985. Proceedings of a Network Meeting held at ILCA, Nairobi.
Murray, M., J.C.M. Trail, D.A. Turner and Y. Wissocq. 1983. Livestock Productivity and Trypanotolerance. Network Training Manual. Addis Ababa: ILCA.
