ANALYSIS OF EFFECTS OF TSETSE CONTROL ON LIVESTOCK PRODUCTIVITY AND HEALTH
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ANALYSIS OF EFFECTS OF TSETSE CONTROL ON LIVESTOCK PRODUCTIVITY AND HEALTH. Nicholas N. Ndiwa, Woudyalew Mulatu and John Rowlands International Livestock Research Institute. BACKGROUND.

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ANALYSIS OF EFFECTS OF TSETSE CONTROL ON LIVESTOCK PRODUCTIVITY AND HEALTH

Nicholas N. Ndiwa, Woudyalew Mulatu and John Rowlands

International Livestock Research Institute


BACKGROUND PRODUCTIVITY AND HEALTH

  • Trypanosomosis is a serious disease affecting livestock in many parts of sub-Saharan Africa including Ethiopia.

  • The parasite that causes the disease is carried by the tsetse fly.

  • Persistently high levels of trypanosomosis found in cattle at Ghibe in southwest Ethiopia, where ILRI works, occur because of drug resistance.

  • Thus, drug therapy on its own at Ghibe does not work.

  • The alternative is to reduce the numbers of tsetse flies.

  • Two interventions to control tsetse numbers have been implemented

  • 1. - with insecticide impregnated targets

  • 2. - with insecticide pour-on applied to the backs of cattle.


Drug treatments for disease cases PRODUCTIVITY AND HEALTH

Time-line of treatments and tsetse control interventions

Invasion of third tsetse species

Drug treatment for all cattle

Drug treatment for all cattle

Jul-89

Jul-91

Jul-93

Jul-87

Jul-95

Jul-97

Mar-90

Mar-92

Mar-94

Mar-86

Mar-88

Mar-96

Mar-98

Nov-90

Nov-92

Nov-94

Nov-86

Nov-88

Nov-96

Targets

Pour-on

Theft of the targets


Measurements were made monthly on the following: PRODUCTIVITY AND HEALTH

  • Packed cell volume (PCV)

  • Trypanosome prevalence

  • Body weight

Calves were ear-tagged at birth and their details recorded.

Disposal (deaths, disappearance or sales) were also recorded.


Productivity and health variables calculated PRODUCTIVITY AND HEALTH

  • Tsetse density

  • Mean body weight, PCV, trypanosome prevalence, no. of treatments - separately for males and females

  • Calf growth rate and 12-month body weight

  • Mortality rate in males, females and calves

  • Abortion rate and calf/cow ratio to reflect fertility level

  • Herd size


Possible time units for analysis PRODUCTIVITY AND HEALTH

One month?

Problems? - handling seasonal variation

- handling increasing ages of cattle

- handling pregnancy and lactation

- positive serial correlations from month to month

- other confounding random variables (e.g rainfall)

Three months?

Problems? - handling seasonal variation

- other confounding random variables

- also age, pregnancy, lactation

Six months?

- now possible to match with season (wet and dry)

- other factors not so important

Twelve months?

- best for matching with agronomic (planting and harvesting) and livestock production / management

- matches annual rain cycle


Data set structure PRODUCTIVITY AND HEALTH


Statistical model PRODUCTIVITY AND HEALTH

yijk=+si+pj+ck+(pc)jk+eijk

where s=season, p=period and c=control

Interaction not significant for any variable. Hence dropped for final model


Genstat output for analysis of body weights for bulls PRODUCTIVITY AND HEALTH

Estimates of parameters

estimate s.e. t(18) t pr.

Constant 217.24 5.53 39.28 <.001

SEASON 2 6.48 5.07 1.28 0.217

PERIOD 2 11.06 5.10 2.17 0.044

CONTROL 2 11.40 5.28 2.16 <.045

Accumulated analysis of variance

Change d.f. s.s. m.s. v.r. F pr.

+ SEASON 1 231.11 231.1 1.64 0.217

+ PERIOD 1 762.3 762.3 5.40 0.032

+ CONTROL 1 658.2 658.2 4.66 <.045

Residual 18 2543.3 141.3

Total 21 4194.8 199.8

Least square means

Control Body weight s.e.

0 226.52 4.21

1 237.91 3.18


Variable Tsetse control PRODUCTIVITY AND HEALTH

without withSEDP Change (%)

Bulls

Body weight (kg) 226.52 237.91 5.28 <0.001 8

PCV (%) 22.8 23.8 0.64 <0.01 7

Trypanasome prevalence (%) 0.36 0.31 0.042 <0.05 24

Annual mortality (%) 0.20 0.11 0.039 <0.001 62

Calves

Growth rate – wet season (kg/month) 0.22 0.23 0.025 0. 4

Body weight at 12 months (kg) 68 76 2.2 <0.01 12

Effect of tsetse control on selected variables


Targets PRODUCTIVITY AND HEALTH

Pour-on


Targets PRODUCTIVITY AND HEALTH

Pour-on


Targets PRODUCTIVITY AND HEALTH

Pour-on


Targets PRODUCTIVITY AND HEALTH

Pour-on


  • Conclusions PRODUCTIVITY AND HEALTH

  • The general health of cattle improved with increased body weights and reduced mortality.

  • This corresponded to decreased trypanosome prevalence, although the average trypanosome prevalence still remained comparatively high.

  • Insecticidal pour-on has an effect, not only on tsetse, but also on other nuisance flies. This may also have helped towards improved cattle health over this period.

  • The analytical approach we adopted provided an analysis that simplified the difficulties in dealing with confounding factors and serial correlations between successive measurements.


  • Conclusions PRODUCTIVITY AND HEALTH(continued)

  • We lagged the effect of tsetse control by 6-months based on the knowledge that the intervention of tsetse control has a delayed effect. The data appeared to show this.

  • Our method resulted in 13 observational units when tsetse control was applied and 9 when not; this was more than adequate for the statistical analysis.

  • The length of the study demonstrated that application of tsetse control can be sustainable.


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