| dc.description.abstract | A field study was carried out to determine the
prevalence of Bovine parasitic otitis in the semi arid (hot
dry) and the high potential (cold humid) areas of Kenya. A
prevalence ranging from 27.3% to 78.3% was recorded in the
semi arid areas of Kajiado and of between 5% and 13.6% in
the high potential areas of Makuyu (Hurang~a) where the
disease also occurred ina less severe form. There was a
significant difference in the prevalence (P < 0.001) and
severity of the disease between the two agro-ecological
regions. However~ the observations in the semi arid areas
were comparable to what have been reporteq_ from the hot and
humid (coastal) areas where the disease is known to be more
prevalent. Rhabditis (Rh) boyis alone was found to be
associated with the infection in the semi arid while Rh .
bovis and Rh. blumi in separate or mixed infection were
identified from the high potential areas. Where it occurred
alone 7 Rh. blumi was found to be associated with mild and
chronic cases.
Rb. bovis was not isolated from any of the dips used by
infected cattle while Rh. blumi was recovered from one dip.
The nematodes survived in dip samples from the understrength
dips for an average of 3 days for Rh bovis and more than 3
weeks for Rh. blumi •. In freshly prepared correct strength
acaricide solutions, both species were killed within 10
minutes by Amitraz a diamide (Triatix-Coopers) and in less
than 2 hours by Chlorfenvinphos (Supona, Shell and Supadip,
Wellcome). In Delnav (DeLnav DFF-Wellcome) and in water
Rh. bovis survived for only 3 days whereas Rh. blumi
survi ved for 28 days. Delnav and understrength
Chlorfenvinphos dips are good reservoirs of Rh. blumi but
can act as source of infection for both species during
cattle dipping.
In an experimental study to determine the
pathogenicity of the two Rhabditis species, three of the
four cattle infected with Rh. bovis developed a bilateral
moderate, severe, or very severe otitis externa within 5 to
17 days (10) after infection.
and histological changes were
The clinical, pathological
similar to what have been
reported on field cases of the disease. No animal infected
with Rh. blumi developed clinical otitis, but all of them
showed a unilateral or bilateral increase in soft cerumine
secretion from which worms were recovered. The reaction
receded soon after the worms disappeared from the canal.
One ear in which the reaction persisted for 76 days had a
hyperaemic mucosa. This together with two others, showed
a partly disrupted and necrotic epidermis and inflamed
dermis on histological examination. The changes however,
appeared to be a result of the pyogenic bacteria found in
the ears rather than from worms. These results support the
field study and other reported studies that Rh. blumi is a
less pathogenic free living species whose occurrence in the
ear may be a chance contamination. | en |
