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Journal of Animal Production Advances
Isolation of Salmonella Species from Milk and Locally
Processed Milk Products Traded for Human Consumption and
Associated Risk Factors in Kanam, Plateau State, Nigeria
Karshima N. S., Pam V. A., Bata S. I., Dung P. A. and Paman N. D.
J Anim Prod Adv 2013, 3(3): 69-74
DOI: 10.5455/japa.20130330124355
Online version is available on: www.grjournals.com
ISSN: 2251-7677
KARSHIMA ET AL.
Original Article
Isolation of Salmonella Species from Milk and
Locally Processed Milk Products Traded For
Human Consumption and Associated Risk Factors
in Kanam, Plateau State, Nigeria
1
Karshima N. S., 2Pam V. A., 1Bata S. I., 1Dung P. A. and 1Paman N. D.
1
Department of Animal Health, Federal College of Animal Health and Production Technology Vom, Plateau State, Nigeria.
2
Department of Parasitology, National Veterinary Research Institution Vom, Plateau State, Nigeria.
Abstract
This study was conducted to determine the prevalence of Salmonella species in milk and locally processed
milk products traded for human consumption and assess the risk factors associated with Salmonella milk
contamination in the study area. The study utilized microbiological culture and isolation as well as
questionnaire analysis. A total of 600 samples were studied, 200 each for fresh milk (madara), full creamed
milk (kindirmo) and skimmed milk (nono). The study revealed an overall prevalence of 8.7% (52/600). About
0.2% (1/600), 3.0% (18/600), 1.0% (6/600), 2.0% (12/600) and 2.5% (15/600) of the overall prevalence were
recorded in Dengi, Gargah, Kanam, Gagdi and Gidgid districts of the Local Government Area (LGA)
respectively. This revealed a high level of statistical significance (P<0.05). Prevalence rates in relation to milk
type were 6.4% (38/600), 1.5% (9/600) and 0.8% (5/600) for fresh milk, full creamed milk and skimmed milk
respectively. This showed a high level of statistical significance (P<0.05). Based on sources of water used for
milk processing, prevalence rates were 6.8% (41/600), 1.7% (10/600) and 0.2% (1/600) for stream water, well
water and borehole water respectively. These differences were highly significant statistically (P<0.05). Risk
factors analysis revealed that 31.3% (188/600) of the respondents were not aware of salmonellosis and 82.2%
(493/600) were not aware of the risk of acquiring Salmonella via milk consumption. There were high
association between the prevalence of Salmonella in milk and the risk of sucking milk directly from the udder
of cows (P<0.00001, OR = 8.7448), the use of stream water in processing milk (P=0.0001, OR = 3.6733) and
failure to wash the udder of cows before milking (P=0.0041, OR = 0.2072). This study has revealed the
presence of Salmonella species in milk traded for human consumption and the risk factors associated with their
contamination in Kanam Local Government Area of Plateau State, Nigeria.
Keywords: Isolation, Salmonella, risk factors, milk, local milk products, human consumption.

Corresponding author: Department of Animal Health, Federal College of Animal Health and Production Technology Vom, Plateau State, Nigeria.
Received on: 09 Mar 2013
Revised on: 17 Feb 2013
Accepted on: 21 Mar 2013
Online Published on: 31 Mar 2013
69
J. Anim. Prod. Adv., 2013, 3(3):69-74
ISOLATION OF SALMONELLA SPECIES FROM MILK AND LOCALLY …
Introduction
Generally, milk has been described as a nearly
perfect food because it contains the essential
nutrients required by the body in appropriate
proportions. However, it is a very efficient vehicle
for bringing a large number of people into contact
with potential microbial hazards (Jordan, 2007).
The safety of dairy products with respect to foodborne diseases is a major global issue especially in
the developing countries where production of milk
and milk product takes place under poor hygienic,
sanitary and Agricultural practices (Jordan, 2007).
Bacterial organisms which may gain entry into
milk can multiply and cause spoilage, rendering raw
or processed milk unsuitable for human
consumption due to rancidity, musty odour, or toxin
production (Nanu et al., 2007). These organisms in
milk indicate inadequate milking procedures, poor
storage conditions, or unhygienic productions (Gran
et al., 2003; Girmaud et al., 2009). The presence of
pathogenic bacteria which may not be associated
with spoilage of milk such as Salmonella spp,
Brucella spp, Mycobacterium bovis, Listeria
monocytogenes and Campylobacter jejuni can
render raw and processed milk unsafe for human
consumption (Nanu et al., 2007).
Salmonellosis is the most common food-borne
bacterial disease worldwide (Forshell and Wierup,
2006). There have been increased outbreaks of
human salmonellosis in most parts of the world
resulting from animal infections (Forshell and
Wierup, 2006). The prevention and control of
animal salmonellosis has become a global issue, as
this has been established as the main source of
outbreaks in humans (EFSA, 2006).
Food-borne salmonellosis has remained a
neglected zoonosis in Nigeria and other developing
countries of the world, despite an upsurge of cases
reported. Raw milk and milk products are
increasingly becoming important sources of human
infection with Salmonella. Food vehicles implicated
in most food-borne disease outbreaks is often
consumed or discarded before clinical symptoms
develop in the exposed individual (Fontaine et al.,
1980). The screening of milk and other dairy
products against pathogenic organisms will play a
vital role in curtailing human infection. This study
70
determined the prevalence and the risk factors
associated with Salmonella contamination of milk
and locally processed milk products in Kanam
Local Government Area of Plateau State, Nigeria.
Materials and Methods
Study Area
The study was conducted in Kanam Local
Government Area of Plateau State, Nigeria. Kanam
is located in the central zone of the state. The study
covered five districts namely Dengi, Gargah,
Kanam, Gagdi and Gidgid. The major occupation in
this area is crop and livestock farming.
Sample Collection
A total of 600 milk samples were collected
from five district of Kanam LGA of Plateau State,
Nigeria. Milk samples were collected using
systematic sampling technique. Using the sitting
arrangement of milk sellers, the fifth milk sellers
were sampled each day until 120 samples were
collected from each of the five districts. A total of
100 ml of thoroughly mixed milk were purchased
from milk sellers and transferred into sterilized,
clean and dry sample bottles and transported in ice
cool flash within 6 hours to the bacteriology
laboratory of the National Veterinary Research
Institute Vom, Nigeria for microbiological analysis.
Isolation and Identification of Salmonella
spp.
The isolation of Salmonella spp. was carried
out using the method described by Quinn et al.
(2002). The samples were enriched in RapportVasilliadis broth. A sterile swab from raw or locally
processed milk sample was inoculated into RapportVasilliadis broth and incubated at 37 OC for 24
hours. A loopful of Rapport-Vasilliadis broth was
streaked onto xylose lysine desoxycholate agar and
incubated for a further 24 hours at 37 OC. The
colonies were examined for the characteristic
pinkish colour of Salmonella with or without
hydrogen sulphite. Suspected colonies were then
subjected to indole, motility, oxidase, urease, citrate
and sugar fermentation tests for identification of
Salmonella spp.
Results
J. Anim. Prod. Adv., 2013, 3(3):69-74
KARSHIMA ET AL.
A total of 600 samples were studied, 200 each
for fresh milk (madara), full creamed milk
(kindirmo) and skimmed milk (nono) as shown in
Tables 1-3. The study revealed an overall
prevalence of 8.7% (52/600) as shown in Tables 13. About 0.2% (1/600), 3.0% (18/600), 1.0%
(6/600), 2.0% (12/600) and 2.5% (15/600) of the
overall prevalence were recorded in Dengi, Gargah,
Kanam, Gagdi and Gidgid districts of the Local
Government Area (LGA). This revealed a high level
of statistical significance (P<0.05) as shown in
Table 1. Prevalence rates in relation to milk type
were 6.4% (38/600), 1.5% (9/600) and 0.8% (5/600)
for fresh milk, full creamed milk and skimmed milk
respectively (Table 2). This showed a high level of
statistical significance (P<0.05). Based on sources
of water used for milk processing, prevalence rates
were 6.8% (41/600), 1.7% (10/600) and 0.2%
(1/600) for stream water, well water and borehole
water respectively (Table 3). This difference was
highly significant statistically (P<0.05). Risk factors
analysis revealed that 31.3% (188/600) of the
respondents were not aware of salmonellosis and
82.2% (493/600) were not aware of the risk of
acquiring Salmonella via milk consumption. There
were high association between the prevalence of
Salmonella in milk and the risk of sucking milk
directly from the udder of cows (P<0.00001, OR =
8.7448), the use of stream water in processing milk
(P=0.0001, OR = 3.6733) and failure to wash the
udder of cows before milking (P=0.0041, OR =
0.2072) as shown in Table 4.
Table 1: District based prevalence of Salmonella isolates in milk traded for human consumption
in Kanam LGA.
Number of samples
Number positive
District specific
Overall
District
examined
for Salmonella
prevalence (%)
Prevalence (%)
Dengi
120
1
0.83
0.2
Gargah
120
18
15.0
3.0
Kanam
120
6
5.0
1.0
Gagdi
120
12
10
2.0
Gidgid
120
15
12.5
2.5
Total
600
52
8.7
X2 = 2400.00 P < 0.00001, Degree of freedom = 16
Table 2: Prevalence of Salmonella isolates in milk traded for human consumption in Kanam LGA in relation to
milk type
Number of
Number positive
District specific
Overall
Milk type
samples examined
for Salmonella
prevalence (%)
Prevalence (%)
Fresh milk (Madara)
200
38
19.0
6.4
Full creamed milk (Kindirmo)
200
9
4.5
1.5
Skimmed milk (Nono)
200
5
2.5
0.8
Total
600
52
X2 = 1200.00, P < 0.00001, Degree of freedom = 4
Table 3: Prevalence of Salmonella isolates in milk traded for human consumption in Kanam LGA in
relation to water source.
Number of samples
Number positive
District specific
Overall
Source of water
examined
for Salmonella
prevalence (%) Prevalence (%)
Stream
317
41
12.9
6.8
Well
204
10
4.9
1.7
Bore hole
79
1
1.3
0.2
Total
600
52
8.7
71
X2 = 1200.00, P < 0.00001, Degree of freedom = 4
J. Anim. Prod. Adv., 2013, 3(3):69-74
ISOLATION OF SALMONELLA SPECIES FROM MILK AND LOCALLY …
Table 4: Analysis of risk factors associated with Salmonella contamination of milk traded for human consumption
in Kanam LGA.
Statistical significance
Risk factor
NQA
R
NR Prev (%)
P
Odd Ratio
95% CI
Aware of salmonellosis
600
Yes
412
37 (8.89)
0.6858
1.1380
0.6082, 2.1290
No
188
15 (8.89)
Aware that Salmonella can be acquired
600
Yes
107
12 (11.2)
0.3013
1.4305
0.7233, 2.8293
through milk consumption
No
493
40 (8.11)
Suck milk directly from the udder
600
Yes
302
46 (15.2) <0.00001
8.7448
3.6741, 20.814
No
298
6 (2.01)
Use stream water to process milk
600
Yes
317
41 (12.9)
0.0001
3.6733
1.8493, 7.2962
No
283
11 (3.89)
Forward milk from sick animals to the
600
Yes
211
18 (8.53)
0.9306
0.9738
0.5337, 1.7701
market
No
389
34 (8.74)
Wash udder before milking
600
Yes
128
3 (2.34)
0.0041
0.2072
0.0635, 0.6761
No
472
49 (10.4)
Wash hands before milking
600
Yes
443
43 (9.71)
0.1283
1.7678
0.8411, 3.7155
No
157
9 (5.7)
Discussion
Prevalence of Salmonella in milk and locally
processed milk products
The microbial contamination of milk is multifactorial originating from sources like the air, feed,
soil, faeces, grasses and the milking cow itself.
Other possible sources of milk contamination
include; utensils and water used in the collection
and processing of milk (Coorevit et al., 2008).
Salmonella contamination of milk (CDC, 2003; Van
Kessel et al., 2004; Karns et al., 2005) and milk
products (CDC, 1984; CDC, 1994) has been
reported in several parts of world confirming its
grouping as a neglected zoonotic pathogen. The
occurrence of Salmonella in milk and milk products
revealed by this study may not be unconnected with
the underscored factors.
The overall prevalence of 8.7% revealed by this
study is lower than the 11.8% reported by Karns et
al. (2005). However, it is on the higher side when
compared with the 2.6% and 0.0% reported by Van
Kessel et al. (2004) and Mhone et al. (2012)
respectively. These variations may be explained by
the differences in location, hygienic practices and
the availability of potable water. The quality of
Agricultural practices observed on the farms may
72
also cause variations in levels of contamination with
Salmonella.
Dengi district which is the most developed of
the whole study area recorded the lowest prevalence
rate. This may be explained by the availabilities of
veterinary services and potable water used for milk
procession. The use of water from the streams
which are visited by humans, domestic animals and
wildlife may be a possible reason for the higher
prevalence rate observed by samples from Gargah
and Gidgid. This is because these un-flowing
streams are easily contaminated by visiting animals.
The prevalence recorded by fresh milk samples
was statistically higher than that from full creamed
and skimmed milk. Both full creamed and skimmed
milk are boiled during processing to destroy
microbes. This may be the reason for the lower
prevalence recorded by these sample types. The unboiled nature of fresh milk may be the probable
reason for the higher prevalence observed. This
suggests that the milk contamination might have
arisen from the lactating cows, themselves, humans
or unhygienic milking practices (Addis et al., 2011).
Stream water is a source of water for both
humans and animals in the rural settlements. Both
domestic and wildlife visits such areas to drink
water thereby contaminating the water with dirt
J. Anim. Prod. Adv., 2013, 3(3):69-74
KARSHIMA ET AL.
from their wool or defecation into the stream. For
this reason stream water is believed to contain high
levels of bacterial load. This is also the likely
explanation for the higher prevalence recorded by
milk samples processed using water from the
stream. The lowest prevalence recorded by samples
processed by borehole water may not be
unconnected with the cleanliness of the water
source used for milk processing.
Risk factors associated with Salmonella
contamination of milk
There were high associations between the
prevalence of Salmonella in milk and milk products
and sucking milk directly from the udder of cows
(P<0.00001, OR = 8.7448), the use of stream water
for the procession of milk (P= 0.00001, OR =
3.6733) and lack of washing the udder of cows
before milking (P= 0.0041, OR = 0.2072). These
factors would have influenced the occurrence of
Salmonella species in milk samples studied.
Also 31.3% of respondents who were unaware
of the infection and those who were unaware of the
roles of water, dirty cows, sick animals and dirty
hands in the contamination might have cause
contamination of milk during processing. This lack
of knowledge would have played a key role in the
prevalence of Salmonella isolated from milk traded
for human consumption in Kanam Local
Government Area of Plateau State, Nigeria. It is
suggested that Good Agricultural Practices and
adequate hygiene be employed at the farm level and
milk be processed using potable water to ensure
public health.
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