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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