| dc.description.abstract | Cystic Echinococcosis, caused by Echinococcus granulosus is a major health
problem among the nomadic communities of Africa, with the highest incidence
in the world being reported in Turkana, Kenya.· However. the information
available on the disease has various gaps which, if filled, would lead to better
management of the disease. These studies were carried out in an attempt to
bridge some of the gaps. The studies aimed at evaluating ultrasound as a
diagnostic method for cystic echinococcosis. The other objective was to evaluate
various treatment methods used for the disease in humans using sheep and p:oal CJ "
models.
The first study was carried out in two parts. The first part was to determine the
sensitivity. specificity and kappa statistic using postmortem examination as the
gold standard. Ultrasound examination, followed by postmortem examination was
perfomed in 300 animals (16 sheep and 284 goats). Thirty-one animals (10.3%) were
positive for echinococcus cysts on ultrasound examination and 46 (15.3%) were
positive on postmortem examination. Twenty-one animals positive on postmortem
were falsely identified as negative on ultrasound examination. Of tile 254 animal"
identified as negative on postmortem, six (2.4 %) were falsely identified positive
on ultrasound examination. The sensitivity and specificity of ultrasonography was
54.36% and 97.64% respectively. Positive predictive value and negative predictive
value was 80.64% and 92.19% respectively. The degree of clinical agreement
between ultrasound and postmortem examinations (kappa) was 0.59.
The second part was to document pertinent ultrasonographic features in diagnosis
of Echinococcus cysts and the costs of performing ultrasonography in sheep and
goals. In this study, ultrasonographic examination of 15 animals with
Echinocccus cysts was performed. Normal ultrasonographic findings of the
abdominal organs are presented and illustrated. Ultrasound findings of
Echinococcus cysts and its differential diagnosis are also presented. The diagnostic
features for Echinococcus cysts were double membrane (endocyst and ectoryst),
presence of 'hydatid sand' (protoscoleces), and seplations (daughter cysts).
Echinococcus cysts needed to be differentiated from Taenia hydatigena cysts, empty
rumen and gall bladder in hunger animals. Ultrasonography could be used to
detect the location, size and nature of the cysts. The cost of ultrasound
examination per animal was $ 0.714.
In the second study, the applicability of Ultrasonography ill prevalence studies
of cystic echinococcosis was investigated. A total of 1390 goats were examined,
43.6 % (606/1390) of them from Northwestern Turkana, Kenya, and 56.4 %
(784/1390) from Toposaland, Southern Sudan. Echinococcus cysts were visualiscd
in 1.82 % (11/606) of the goats from Northwestern Turkana and 4.34 % (34/784) of
those from Toposaland. Ultrasonography was found to be limited ill detection of
Echinococcus cysts in the lungs. However, it was found to be an appropriate
technique where slaughter was not monitored. Ultrasonography also proved 1.0 be
a non-invasive and unbiased technique for prevalence studies of Echinococcus
because unlike slaughter, whole herds of goats were examined.
The third study was carried out to determine the prevalence of cystic
echinococcosis in domestic animals in northern Turkana, Kenya. Animals were
examined at slaughter in Lokichogio, Kakurna and Central Divisions of Northern
Turkana. A total of 6791 animals were examined at slaughter in the three study
areas. These included 5752 goats, 588 sheep, 381 cattle and 70 camels. In cattle,
sheep, goals and camels, the prevalence of Echinococcus cysts was found to be
19.4%, 3.6%, 4.5%, and 61.4% respectively. The prevalence of cystic
echinococcosis in cattle, sheep and goals was higher in Lokichogio than ill either
Kakuma or Central divisions. On the other hand, the prevalence of the disease ill
camels was higher in Central (84.6%) than either Lokichogio (70.6%) or Kakuma
(50%). The differences in prevalence rates in different study areas were attributed
to differences in environmental conditions, livestock stoking intcnsitv, and crossborder
migration of livestock.
In the fourth study, the efficacy of oxfendazole in treatment of Echinococcus
was investigated. Nine goats and four sheep, naturally infected with Echinococcus
cysts, were given oxfendazole orally at 30mg/kg twice per week for 4 weeks. Tilt'
animals were monitored by ultrasound examination during the treatment period
and 4 weeks after treatment. Ultrasound appearance of the cysts, postmortem
examination of the animals, viability of protoscolices and cyst wall histology
were used to determine the efficacy of oxfendazole. In the treatment group,
Echinococcus cysts showed a decrease in size, mixed echogenicity and complete or
partial detachment and calcification on ultrasound examination. There was no
visible change of cyst appearance in control animals on ultrasound examination.
On post-mortem examination, 53% of cysts from treated animals Wt're round to
be grossly degenerated. On microscopic examination, protoscolices were dead or
absent in 97% of cysts from oxfendazole treated animals compared to 2n% of
cysts from untreated control animals. Histological examination of the cysts
showed severe disorganisation of the adventitial layer with the invasion of
inflammatory cells in treatment group. This was absent in control group.
In the fifth study, the efficacies of oxfendazole and albendazole were compared
in treatment of cystic echinococcosis. 15 animals were randomly selected into :3
groups of 5 animals each. Two groups were subjected to treatment (with either
albendazole or oxfendazole) while the third group served as controls. In the
treatment groups, ultrasound examination showed similar findings as
oxfendazole group in study 4. Microscopic examination of protoscolices for
eosin dye exclusion and flame cell motility showed that 60.9% ('14/23) of the
cysts from albendazole group had dead protoscolices compared to 93.3% (14/15)
and 27.3% (3/1]) for oxfendazole and control groups respectively.
In the sixth study, PAIR (Puncture, Aspiration, Introduction of a scolicidal agent,
and Re-aspiration of the agent) technique was evaluated. The objective of this
study was to determine the effect of ethyl alcohol in the PAIR technique as
compared to puncture alone (without ethyl alcohol). Six animals were used in the
study. The animals were sedated with xylazine and, under ultrasound guidance
a total of 9 cysts were subjected to puncture and ethyl alcohol while 7 cysts was
subjected to puncture alone. One month after the treatment, the e niruals were
scanned with ultrasound and euthanised for postmortem examination.
Postmortem examination showed that both groups (puncture and ethyl alcohol
group and puncture alone group) had dead protoscoleces. However, the cvsts
that had both puncture and introduction of ethyl alcohol were grossly
degenerated and were surrounded by fibrosis of liver tissues. III contrast, lire
cysts where puncture alone was carried out, the cysts appeared int{ll-I.
The seventh study investigated the presence of different strains of Echinococcus
granulosus in domestic intermediate hosts. Endocysts or protoscolcccs from
human, cattle, sheep camels and pigs were examined by polymerase chain
reaction (PCR) technique. Primers for known DNA sequences for E. grouulosus
were used. The target sequence for amplification was part of mitochondrial 125
rRNA gene. The PCR was conducted in two steps, one involving a cestode
specific primer and the other involving a primer specific to E. granulosus sheep
strain. In the first step, the primer pair P60 for and 1'375.rev. amplified a 373bp
fragment of the DNA. A total of 2s0ng of DNA was added to a reaction mixture
containing 10mM Tris-HCI buffer, 2.smM MgCI2, 200uM dNTPs, 40~"'mols/1I1
P60Jor., 40prnolsj ul P37s.rev. and 2.SU Taq polymerase. Thermal cycling of llu:
amplification mixture was performed in an automated Cene Am I' FeE Svstoru
9700®. A cycle represents denaturation for 30 seconds at (.W'c, clllC'i1lillg for (,()
seconds at s2°e, and elongation for 40 seconds at 72oC. III ,111the SMlljll(H;
collected from humans, sheep, pigs, 88% of cysts from cattle and ?[)% of C\c;lc;
from camel had sheep strain E. gI'l1l111!oslls.12% of cysts from calt!c and l)O"() (If
cysts from camels had camel strain E. gmuulosus.
Based on the findings of these studies ultrasonography is an appropriate
technique for diagnosis of cystic echinococcosis in sheep and goats. It is noninvasive,
relatively inexpensive to perform and can be used even in remote areas
where laboratory facilities are not available and slaughter is not monitored.
However, it has a limitation of not detecting cysts in the lungs. Oxfendazole had
a higher efficacy against cystic echinococcosis than albendazole. Puncture and
introduction of 95% ethyl alcohol had similar efficacy against Echinococcus cysts
as puncture alone but ethyl alcohol treated cysts were more degenerated 1 month
post treatment, Both sheep and camel strains were identified in human and
animal intermediate hosts from Kenya. Further research is recommended in
oxfendazole therapy and PAIR technique. | en |
