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Research, Policy and Practice

Table 1 Summary of parameters and methodology for estimating losses due to PPR in Turkana pastoral herds

From: Economic losses associated with Peste des petits ruminants in Turkana County Kenya

Parameter description Methodology for estimation of parameter
Herd age structure  
G y…a = proportion (%) of sheep/goats in age group young to adult Proportional piling (PP) of sheep and goat herds by age group (n = 27)
Losses due to mortality  
H y…a = PPR mortality (%) of sheep/goats in age group young to adult PP sheep (n = 43)/goat (n = 44) mortality by disease
H a = mortality (%) of pregnant female Mortality in adult sheep and goats
C y…a = value expressed in US$/TLU kg for sheep/goats in age group young to adult Value of sheep or goat in TLU (C me*W y…a)
Losses from reduced milk production  
S m…f = proportion (%) of male and female sheep/goats in the herds PP sheep (n = 6)/goat (n = 6)
L f = proportion (%) of lactating sheep/goats Derivative of PP from G y
P f = proportion (%) of pregnant sheep/goat Derivative of PP sheep (n = 6)/goat (n = 6)
I y…a = prevalence (%) of PPR in sheep/goats in age group young to adult PP for disease prevalence
I af = prevalence (%) of PPR in lactating sheep/goats PP for disease prevalence I af equals I a in adults
V l = volume of milk loss (litres) per day per PPR case Key informant interviews
T r = duration (days) of reduced milk production per acute PPR case Course of disease as described by Bundza et al. (1988)
V a = daily volume (litres) of milk produced per healthy sheep/goat Key informant interviews and literature (Njanja 1991)
T l = lactation period (days) Literature (Njanja 1991; Marete 2011)
C m = sale value of milk (US$/l) Key informant interview with milk sellers
C me = TLU value expressed in US$/unit weight of TLU TLU = 250 kg; cost of TLU is US$ 150. Value of TLU/kg is US$ 0.6 (ILCA 1988; Mude et al. 2010)
Losses due to weight losses  
W l = proportion (%) of body weight loss Key informant interviews
W a…y = average body weight (kg) of sheep/goat in age group young to adult Key informant interviews with livestock officials and keepers
K = inter-kidding/lambing interval in days Key informant interviews and literature (Njanja 1991)
B = birth weight (kg) of kid/lamb Literature (Njanja 1991)
N = sheep/goat population in study area in Turkana County KNBS 2010 Kenya population and livestock census data
Q = delay in conception in months due to disease Key informant interviews and livestock keepers