Proceedings of the 10th International Colloquium on Paratuberculosis

#42 Seroprevalence survey <strong>of</strong> paratuberculosis in dairy and pastoral cattle in Uganda
Julius Boniface Okuni, Lonzy Ojok
Makerere University, Uganda
Between 1999 and 2002, lesions consistent with <strong>the</strong> description <strong>of</strong> paratuberculosis were observed from abattoir
specimens taken from slaughtered cattle. The aim <strong>of</strong> this study was to determine if <strong>the</strong>re was serological
evidence for <strong>the</strong> prevalence <strong>of</strong> <strong>the</strong> disease among <strong>the</strong> cattle population. A total <strong>of</strong> 1023 cattle were selected by
a multistage sampling technique from 66 cattle herds in 4 districts and tested for antibodies against M. paratuberculosis
using Pourquier ELISA. The tested animals were from 7 different breeds, namely, Holstein Friesians,
East African Zebu, Ankole long horn, Boran, Sahiwal, Jersey and Guernsey. At least 43 heads <strong>of</strong> cattle
(4.2%) were serologically positive. 24 <strong>of</strong> <strong>the</strong> 66 herds <strong>of</strong> cattle had at least one positive animal (36%) based
on <strong>the</strong> manufacturer’s cut <strong>of</strong>f. All <strong>the</strong> breeds <strong>of</strong> cattle except Guernsey had at least one infected animal. The
disease was found to be present in all <strong>the</strong> four districts surveyed. Infection was also observed in cattle under
all <strong>the</strong> different types <strong>of</strong> husbandry practices. This is <strong>the</strong> first time <strong>the</strong> prevalence <strong>of</strong> Johne’s disease has been
determined in Uganda. Paratuberculosis has hi<strong>the</strong>rto been silently spreading among <strong>the</strong> cattle population in
Uganda. This study provides information that will be used in future epidemiologic studies and control programs.
#44 Genetic variation in serological response to Mycobacterium avium subspecies
paratuberculosis and its association with performance in Irish Holstein-Friesian dairy cows
Margaret Good, Peter Mullowney, Andrew Cromie, Simon J More
Dept Agriculture, Fisheries and Food, Ireland; The Irish Cattle Breeding Federation, Ireland; Centre for Veterinary
Epidemiology and Risk Analysis, Ireland
Few estimates <strong>of</strong> <strong>the</strong> genetic variation in measures <strong>of</strong> susceptibility to MAP are available in <strong>the</strong> literature and
even less have attempted to elucidate <strong>the</strong> genetic associations between measures <strong>of</strong> susceptibility to MAP
and performance in dairy cattle. Therefore, <strong>the</strong> objectives <strong>of</strong> this study were to estimate <strong>the</strong> genetic variation
in serological response to MAP in 5,280 Holstein-Friesian dairy cows, and to quantify its genetic association
with performance traits measured in <strong>the</strong> first three lactations <strong>of</strong> genetically related animals. Univariate mixed
linear and threshold animal models were used to estimate variance components and genetic correlations were
estimated using bivariate sire linear mixed models; MAP serological response was treated as a continuous
variable and dichotomous variable. The prevalence <strong>of</strong> MAP in <strong>the</strong> sample population was 4.8%. However,
because <strong>of</strong> <strong>the</strong> data editing criteria used, this is not a representative statistic <strong>of</strong> <strong>the</strong> national prevalence. Estimates
<strong>of</strong> heritability for MAP serological response varied from 0.07 to 0.15 depending on <strong>the</strong> model <strong>of</strong> analysis
and whe<strong>the</strong>r serological response was treated as continuous or binary; standard errors varied from 0.024 and
0.062. Genetic correlations between MAP serological response and lactation milk, fat and protein yield were
negative although not always more than two standard errors from zero; stronger negative genetic correlations
were evident in older parity animals. Serological responseto MAP was not genetically correlated with milk fat
concentration but was positively genetically correlated with lactation milk protein concentration and negatively
correlated with calving interval. Positive genetic correlations existed between MAP serological response and
somatic cell count but <strong>the</strong> correlations were not greater than two standard errors from zero. There was little or
no genetic association between serological responseto MAP and survival. Results from this study corroborate
previous international suggestions that selection for reduced serological responseto for MAP is possible, although
this does not necessarily imply a concurrent selection for ei<strong>the</strong>r reduced prevalence <strong>of</strong> clinical disease
or increased resistance to MAP infection.
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