| dc.description.abstract | Fowl typhoid caused by ~. gallinarum has been reported
from all the parts of the world. In Kenya, it is widely
reported, recurrent and apparently resistant to eradication.
Little detailed work had previously been undertaken to determine
the ability of the causative agent to persist in materials
associated with husbandry namely soil, litter and layers mash.
More work on the ability of the organism to persist on poultry
pens was also necessary. The details of such work could then
explain the observed recurrences and resistance to eradication,
and could be used to draw suggestions on useful measures for
eradication.
Twelve isolates of ~. gallinarum were obtained from
.clinical cases and one was used to artificially infect the
forenamed materials and also sawdust-wood shavings mixture-to
represent unused but pre-contaminated litter. The same isolate
was also dispensed onto concrete walls and floor of a chicken
pen. The ability of ~. gallinarum to persist in water under
defined conditions of light and temperature was also investigated
in detail. Three isolates were used to infect tap· and trough
water. Survival in all materials was monitored by quantitative
culture for ~. gallinarum followed by selenite enrichment. In
the chicken pen, monitoring was also done before and after
disinfection with user recommended dilutions of four locally
available disinfectants.
The organism survived in used litter for 5 days when
moisture content was 25% v/wt and 10 days when moisture content
was 50% v/wt. In unused but pre-contaminated sawdustx
woodshavings mixture, ~. gallinarum organisms were not recovered
after one day despite increasing the moisture content to over
five times the natural content of 10% wt/wt. In soil and layers
mash respectively, 107 and 108 organisms per gram survived for 2
days even when the moisture content was increased to 4 times the
natural level of 6% and 12% wt/wt, respectively.'
owing to preliminary studies indicating persistence of
~. gallinarum in water, a further detailed study on this aspect
was neccesitated. Three isolates of ~. gallinarum were used,
subjected to defined conditions of light and temperature likely
to be encountered in the field in tap and trough water.
Persistence in water varied from 5 days to over 79 days depending
on physical conditions. The longest survival duration recorded
was 79 days but two isolates in trough water kept in the dark
survived 77 days. The longest duration for the same isolates in
light was 15 days only. Analysis of viable counts to compare
effects of light and of temperature could not give statistical
significance in each and every case.
On pen surfaces, recovery from the floor was higher
than from wall but the counts were not statistically significant.
When inoculated with 105 organisms per 25cm2, no recoveries from
both sites were possible, 3 days post inoculation. Persistent
infections could not therefore be established.
When decontamination and hygiene user dilutions of 4
disinfectants were tested in the laboratory, the most locally
used disinfectants were found to be ineffective. Establishment of
organisms in wat~r may give rise to recurrent outbreaks of disease in flocks with access to such water. The results of this
work could not point at persistence of §.. qallinarum in soil,
litter, layers mash and on premises. They show active reduction
of the organisms and therefore rule out establishment of §..
qallinarum infections in such materials and on concrete surfaces
as a sole cause of recurrent outbreaks of fowl typhoid. | en |
