Research Results - (PDF, 101 mb) - USAID

can be devastating in susceptible populations. It
is transmitted by ticks that are widely distributed
in Kenya. A vaccine, if available, could be
used to prevent the disease. The first step
toward that goal is the identification of the
recombinant surface protein of the organism.
While evaluating recombinant libraries, a DNA
probe was found for Cowdria ruminantiumwhich
can be used to detect individual infected ticks.
This could be very important for epidemiology
studies to define areas where the disease occurs
and to define conditions where goats are at risk
of infection.
The SR-CRSP and the Kenya Agricultural
Research Institute developed an inactivated
vaccine for contagious caprine
pleuropneumonia vaccine for goats that induces
protection for at least a year. Current research is
directed toward development of a multivalent
vaccine. In addition to vaccine development, a
minimal intervention health program is being
developed for dual purpose goats in western
Kenya. Control measures must be economical if
they are to be used. They include assurances
goats are free of brucellosis, are vaccinated for
contagious
worm control
caprine
as needed,
pleuropneumonia,
and assurance
provided
that
kids obtain colostrum as soon as possible after
birth.
Research Results
The results will be reported underfour activities,
Activity No. 1. Evaluation of Possible
Genetic Resistance to Haemonchus
contortus.
Compare responses of kids with different
fecal egg counts to Haemonchus contortus
challenge.
Problem Statement and Approach
Infection of dual purpose goats and all
other small ruminants with Haemonchus is a
problem in Kenya. Infections of goats in west-
88
ern Kenya require regular treatment with
expensive drugs. One approach to alleviate the
problem is to identify goats genetically resistant
to either infection or the effects of infection. To
identify such goats, fecal egg counts are done
after natural challenge of kids. Those kids with
low fecal egg counts are treated and challenged
with parasite larvae and the results compared to
challenge of kids that have high fecal egg
counts.
Justification
If genetic resistance can be further
demonstrated and exploited, then placing a
more resistant goat on farms is the best longterm
control method for Haemonchus infections.
A resistant goat would save on the costly oral
and injectable drugs to control parasites, thereby
reducing a significant expense in the production
of dual purpose goats.
Progress
ur previour indte that
marked differences occur in the number of
Haemonchuscontortus that become established
among goats in challenge infections. Since these
observations may indicate genetic resistance
that could be incorporated into the ongoing
breeding program, our objective was to compare
responses of kids with different fecal egg counts
to H.contortus challenge. We initially planned
to compare two groups of at least 10 goats
each-one group with low egg counts averaging
less than 300 eggs per gram of feces (EPG), and
the other group averaging more than 1000 EPG.
Because of insufficient kids available for the low
EPG group, we have focused our efforts on
obtaining additional kids that resist H. contortus
infections. We have used two approaches to
identify these kids. In the first, four does from a
low EPG group were bred to one buck from the
same group. This produced five kids that were
raised in confinement and challenged with
10,000 H.contortus. One doe had undetectable
EPG on both the primary and secondary challenge
infections. Additional kids will be available
from this breeding stock for testing in the
coming year.