| dc.description.abstract | Cysticercosis and taeniasis in animals and man,
respectively are widespread in the world and are of great
economic and public health importance in East Af'r-i ce , In
Kenya, the prevalence of Cyst~~ercus bovi~ infection an
cattle is high. The total 10ss8s incurred each year from
condemnation, downgrA~ing and freezing of carcasses are
very high.
Efforts to rid the parasite by treatment of the people
and 'improved mat hot.: ,'+ meat inspection have so far met with
little success. A r-e lreb le arrtrmor-t ern diagnostic technique
plus a chemotherapeutic drug \tJhichwill kill cysts H. muscles
without re::ducingthe quality of meat might pro\lide an
answer to +he cont ro l of the cysticercosis/taeniasis problem.
The objectives of the present investigation were:
(l) to fract Ionet.e crude ant igen pr-epared +rorn t.apeworm
proglottides in order to increase specificity in the indirect
haemagglutination (IHA) test, (2) to try activated oncospheres
as antigen for the indirect fluorescent antibody (IFA) test,
(3) to standardize IHA and IFA tests, using sera from
experimentAlly infected calves, (4) to evaluate the
sensitivity and specificity of the IH.A. and IFA tests using
sera collected at slaughter. and (5) to use the IHA test in a
seroepiderniologic study of bovine cys t i.cer-cosis in Kenya.
Taenia saginata antigens were prepared from mature
tapeworm segments and ~vere partially purified by Sephadex
G-200 column chromatography. This procedure yielded thre8
protein fractions designated Fl, F2 and F3. The crude
antigen, protein fractions FI, F2 and F3 were analysed by
imnunodiffusion and immunoelectrophoresis against anticrudeT.
saginata. rabbit serum. Thr-ee distinct precipitin
bands were observed in .irrmrnod iFf'uaiun of the crude antigen
while three distinct precipitin bands and a few indistinct
bands were obtained in illmunoelectrophoresis of the crude
antigen. In imnunodiffusion, fraction FI gave one sharp
distinct precipitin band and two diffuse wide bands while
F2 showed several fuzzy bands. Fraction F3 showed a weak
precipitin reaction. lr1 imnunoelectrophor8sis, fraction FI
ehowed one distinct band, fraction F2 showed two distinct
bands and several weak bands while fraction F3 either did not
show any precipitin band or when it did, the band was weak
and not well defined.
When t he crude antigen and fractions Fl, F2 and F3 VJel.~e
tested for antigenic reactivity using the IHA test, it was
found that the crude antigen and fraction FI showed high
reactivity while fractions F2 and F3 showed a low degree of
reactivity.
Fraction Fl which was found to be highly antigenical1y
reactive was purified further by DEAr::Sfophadex A-50 and DEAE
cellulose DE 52 ion exchange chromatogr-aphy.
The IHA test was standardized with sera from seven
experimentally infected and four non-infected bull calves,
using both crude and partially purified antigens. Using
either crude or fraction Fl antigen, antibodies to C.
bovis were detectable from 2 weeks post-i.nfection to the
end of the experiment 4 months post-infecbon.
For evaluation of sensiti.vity and specificity of the
IHA test, sera from naturally infected and non--infect:ed
cattle were collected from the Kenya f"leatCorrmiss itin
abattGir, Athi River. Post-mortem records of each anirnal
were obtained during routine meat inspection. Sera from
285 cattle were tested. The IHA test using fraction Fl
antigen showed higher sensitivity and specificity than the
IHf\ test using crude antigen. Partial purification of the
crude antigen by Sephadex G-200 column chromatography
reduced cross-reactivity between sera frornanimals infected
with Echin~c..9l'cusgranulosus from 59.6% to 31.9%.
Fractions Fla and Flb obtained by DEAE Sephadex A-50 and
DEAE cellulose DE 52 ion exchange chromatography of fraction fl,
respectively, shcwed a lower level of cross-reactivity
with sera Fr-om cattle infected wi th E. granulosus than fraction
Fl. The sensitivities obtained with these two antigen fractions
(Fla and Flb), however, were very1dw (45% and 60%, respectively).
The IFA test was carried out using activated encospheres
fixed on gelatin &\ ides as antigen. It was standardized wi t.h
sera from the seven 8xperirnentr3lly infected and four non infected
bull calves used in the standardization of the IHA
test. Titres were found to be slightly higher than for
IHA test.
For evaluation of sensitivity and specificity of the IFA
test, the same 285 sera tested wi t.h the IHA test were screened.
A sensitivity of 91.5% anda specificity of 90.2% WETe obtained.
Cross-reactivity with I. granulosus was 10%.
In the seroepidemiological study, the IHA test using
crudeT.saginata antigen revealed that 82 out of 195 sera
from Rift Valley Province (42.1%) had significant titres
(1:64 or above) while 11 out of 202 (5.4%) sera of cattle
from Central Province had significant titres (l: 64 or above).
When fraction Fl was used in the IHA test 57 out of
the 195 (29.2%) sera of cattle from Rift Valley Province
gave significant titres while 12 out of the 202 [5.~%J sera
of cattle from Central Province gave significant titres.
When compared with results of parasitological findings
it was found that for animals coming from Rift Valley Province,
IHA test using crude antigen gave a significantly higher
percentage of positives than the parasitological survey. On
the other hand, for animals coming from Central Provinc8,
the percentage with positive titres was significantly lower than
that obtained by parasitological examination. 'Comparison of'
the percentages obtained by parasitological examination with
those obtained bv IH,l\ test using fraction Fl antigen showed
that there was no significant difference between the two
percentages in the case of errirne Ls coming from Rift Valley
Province, \A)hereas the percentE1ge of pos l tivc animals by IHA
test using fraction Fl antigen was significantly lower
than that obtained by parasitological survey in case of
animals coming from Central Province.
Based on the results obtained in this study the
following observations and conclusions were made:-
1. Under experimental conditions the IHA test showed good
sensitivity and specificity even when crude antigen was
used.
2. In naturally In+ect sd and non-infected adult slauziter cattle
the IHA test with crude antigen showed low
sensitivity especially in low grade infections. Crossreactivity
with E. granulosuswas high.
3. Partial purification of crude antigen by Sephadex r:--200
column chromatography increased both sensitivity and
specificity and reduced cross-reactivity with E.
granul_osus.
4. Further purification of fraction Fl antigen by DEAE
Sephadex A-50 and DEAE cellulose DE 52 reduced sensitivity
o-~ the IHA test. However-, prolonged storage of
fraction Fl before further purification may have given
rise to this problem.
5. Under experimental conditions the IFA test showed higher
titres than t~e IHA test.
6. In naturally infected and non-infected adult slaughter
cattle the IFA test showed higher sensitivity and specificity
than the IHA test with crude antigen. Both
sensitivity and specificity of the IFA test were not
significantly different from those of IHA test with
fraction Fl antigen.
7. The greatest drawback of the IFA test is that it gwes
non-specific fluorescence especially if the oncospheres
are not completely freed from the oncospheral membranes.
Fresh, mature I. saginata eggs are necessary if good
results are to be obtained.
8. Further work especially in preparation and purification
of 3ntigens is required before the IHA test can be used
as a routine d.iagnns t ic or epidemio1ogical tool in
bovine cysticercosis. | en |
