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Isolation and Identification of Salmonella from Apparently Healthy Pet Dogs in Holeta Town, Western Shoa, Ethiopia
Sultan Aliyi1, Eyob Hirpa1*, Olifan Zewude1 and Yohannes Equar2
1Wollega University, School of Veterinary Medicine, Ethiopia
2Holeta Research Center and National Biotechnology Research Laboratory, Ethiopia
Submission: May 18, 2018; Published: June 07, 2018
*Corresponding author: Eyob Hirpa, Wollegw University, School of Veterinary Medicine, PO box 395, Ethiopia, Tel: +251933686525;
How to cite this article: Sultan A, Eyob H, Olifan Z, Yohannes E . Isolation and Identification of Salmonella from Apparently Healthy Pet Dogs in Holeta
Town, Western Shoa, Ethiopia. Curr Trends Biomedical Eng & Biosci. 2018; 15(2): 555907. DOI: 10.19080/CTBEB.2018.15.555907.
Salmonellosis is one of the most important Zoonotic diseases with global distribution and importance in both humans and animals therefore, a cross-sectional study was carried out aimed at isolation and identification of Salmonella from rectal swab sample of apparently health dogs in Western Shoa, Holeta Town, from November, 2015 to February, 2016. Rectal Swab samples were collected from 123 selected apparently healthy pet dogs’ by cluster sampling Technique for isolation and identification of Salmonella using standard operating procedure of ISO 6579, 2002. The overall detection rate of Salmonella were 17.1% (n=21). Moreover, 14.3% (n=10) and 20.8% (n=11) dogs were Salmonella positive in Burka Harbu and Goro Keransa, respectively. The higher detection rate of Salmonella were recorded in male 17.5% (n=18) than female 15% (n=3) however, the variation between sex were not statistically significant (P>0.05). This study also revealed the highest rate in dogs those fed on all what is available including scavenging by 19.1% (9/47) while animal fed on home left over feed was second ranked 16.9%,(10/59), but those fed only meat was 11.8% (2/17) and this variation also not statistically significant (P>0.05). In conclusion, this study indicates that the detection rate in apparently healthy pet dog shedding of Salmonella from the Western Shoa Holeta Town is high relative to the other species of animal in the country and this show dog play the major role in spreading of the disease to the humans as well as other animals.
Salmonellosis is one of the most important Zoonotic diseases with global distribution and importance in both humans and animals . A number of animal species including ruminants, carnivores, birds and reptiles can play a major role as a carrier in the spread of Salmonellae and transmit them to other healthy animals and humans . It can spread to humans by: close contact with infected animals including livestock, pets,
exhibited animals or wildlife, contact with blood, urine or faeces of an infected animal, water or soil that has been contaminated by infected animals, eating or drinking unpasteurized dairy products, undercooked meat or unwashed fruit and vegetables that are contaminated with faeces from an infected animal  (Figure 1).
Even if there is an infectious agent present, it does not always
result in disease but, depend on three: factors; the infectious
agent, a susceptible host and a way of spread . People most
at risk of being affected by a disease are those in close contact
with animals or animal products including: veterinarians,
farmers, abattoir workers, shearers, and people assisting with
animal births, pet owners, pig hunters, children, elderly people,
pregnant women and people with impaired immunity .
Today, dogs primarily live indoors, share living spaces
with their owners, and assume integral roles as companion’s
family members or service animals. Companion animals are
also increasingly used in therapeutic settings, for instance
in psychotherapy, or to support AIDS patients, children with
disabilities, orthopedic and cardiac patients, Alzheimer patients,
or the elderly. The potential risks associated with such contacts,
particularly for young children or immune-compromised
patients, are difficult to quantify .
Recently, it is believed that the incidence of this disease is
increasing in both man and animals. The intestinal carriage of
Salmonella by dogs is very important to public health. Over the
past 40 years, there have been several reports on transmission
of Salmonella from dogs to humans . The intimate relationship
between dogs and their owners has the potential to increase the
risk of human exposure to bacterial pathogens. In most dogs the
infection occurs in latent form and they shed Salmonella in their
feces and saliva for prolonged time (Figure 2) & .
Most dogs are asymptomatic when they act as reservoirs
of shedding Salmonellae in their feces . Salmonella serovars
readily colonize in the canine large intestine and mesenteric
lymph nodes. Fecal shedding of the pathogen in naturally
occurring infections probably continues for a period of at least 6
weeks. Since the lymph nodes harbor the agent, the carrier state
may persist for much longer periods. Among different species,
dogs can be one of the most important reservoirs of Salmonella
for the following reasons: dogs are one of the most popular pets
in close contact with their owners, including children, and they
can shed the organism for weeks without any clinical signs .
Moreover, a high prevalence of infection caused by numerous
serotypes has been confirmed in cats and dogs. These animals
may be asymptomatic carriers or may suffer from gastroenteritis,
Salmonellosis with varying degrees of severity. Dogs can contract
the infection by eating the feces of other dogs, other domestic or
per domestic animals or man. It can also be infected by ingestion
of contaminated food and transmit the disease to man . In
Ethiopia, there is paucity of information on the role of dogs as
a potential source of Salmonella infection to humans despite an
increased dog keeping in the country.
Therefore, the objective of this thesis is:
A. For isolation and identification of Salmonella in dogs
and investigating the potential role of carrier status in pets’
The study was conducted in central Ethiopia, Holeta which
located at 40km west of Addis Ababa and at an elevation of
2400m.a.s.l in the central Ethiopia (903’N and 38030’E). The
area is characterized by mild subtropical weather, with average
minimum and maximum annual temperatures of 6.3 °C and 22.1
°C, respectively. Total population of city estimated to 25,593 both
sex (male=12, 6058 and female=12,988). Moreover, experience
bimodal rain fall pattern with a long rainy season extending from July to September while the short rainy season extends
from March to April .
A cross- sectional study design was conducted from
November, 2015 to February, 2016 for isolation and identification
of Salmonella in rectal swab sample of pet dogs in Holeta towns,
Oromia special zone surrounding Finfine (Figure 3).
The study area was selected purposively and sample was
taken from two randomly selected Kebeles out of four Kebeles
in town, by using clusters sampling technique. All Apparently
Healthy pet dogs in selected Kebele were sampled (i.e. from
Goro Keransa (n=53) and Burka Harbu (n=70) Keble). A total
of 123 rectal swab samples were collected from two Kebles,
while information of age, sex, feeding system, origin and breeds
of sampled animals were filled for each by interviewing their
Rectal swab sample was obtained with sterile cottontipped
applicators after restraining the animals. Commercially
available cotton swabs were moistened in sterile saline solution
before being inserted in the rectum and put on sterile plastic
fecal collection cups which contain 5ml of sterile saline solution
and transported ice-cooled to Animal Biotechnology Research
Laboratory of National Agricultural Biotechnology Research
Center at Holeta within 5 hours of collection for processing.
Questionnaires were specifically prepared for each source of
samples studied and information on age, breed, sex, feeding
style and origin of animals sampled was obtained.
The isolation of Salmonella from rectal was performed
after selective enrichment in 10ml of Rappaport-Vassiliadis-
Soy peptone broth(RV; Oxoid, UK) and incubated at 37 °C
for 24h(hour). A loopful of enriched broth was streaked on
MacConkey Agar (Oxoid), Brilliant Green Agar (Oxoid Limited,
Detroit, Mich., USA), Salmonella-Shigella (SS Agar) Agar,
Desoxycholate Citrate Agar and Xylose-Lysine Desoxycholate
(XLD) (Oxoid) Agar plates and incubated at 37 °C for 24h. The
plates were examined for the presence of typical colonies of
Salmonella, i.e. pink colonies with or without black centers
on XLD agar and colorless colonies on MacConkey agar, pink
colonies on BGA and colorless colonies on SS agar were subjected
to biochemical tests using standard methods. All presumptive
Salmonella colonies were sub cultured onto Nutrient agar, at 37
°C for 24h, and further confirmed by convectional biochemical
tests such as: Triple Sugar Iron (TSI) agar, Simmons Citrate agar,
Methyl Red (MR) and Indole test to confirm at genera levels, as
recommended by the guidelines of (ISO 6579, 2002) .
All data were entered into a Microsoft Excel spreadsheet
and transferred to SPSS statistical package version 20 statistical
software for analysis. Rate of detection of Salmonella by origin
of sampled animal and associate risk factors were expressed
as percentages. The prevalence was defined as the number of
Salmonella positives per the number of samples examined.
Pearson’s chi-square test was used to compare the association
of prevalence of Salmonella between selected Kebele and
computation of descriptive statistics such as, frequency and
percentage were applied to compute the questionnaires data.
From a total of 123 dogs examined, 21 (17.1%) were positive
for Salmonellae-carrying. Of the dogs, from which Salmonellae
were isolated, 70 (56.9%) were from Goro Keransa and 53
(43.1%) were from Burka Harbu Kebele. Moreover, 10 (14.3%)
and 10 (20.8%) Salmonella positive dogs were encountered in
Burka Harbu and Goro Keransa, respectively (Table 1).
On the other hand, 17 (18.3%) of infected dogs were less than
or equal to two years, while 3 (12.5%) of them were between two
and six years age, but only 1 (16.7%) animal detected in the age
grouped old or above six years. It also indicate that, 18 (17.5%)
and 3 (15%) positive animal were male and female, respectively.
In line with this 17 (17.8%) local and 4 (14.3%) cross breed dogs
were approved for Salmonella carrying. This study also revealed
the highest rate of infection in dog fed on all what is available
including scavenging by 9 (19.1%) out of 47 dogs, while animal
fed on home left over feed was second ranked 10 (16.9%) out
of 59 dogs, but those fed on meat was only two animals i.e., 2
(11.8%) from 17 animals fed on meat during sample collection
Apparently healthy dogs can harbor Salmonella and might
thereby serve as a potential source of human infection with
implications for public health. This study showed that the
asymptomatically shading rate of Salmonella in pet dogs located
in Holeta town of Central Ethiopia is 17.1% and first of its kind
in the country. However, today’s animal medicine estimated the
prevalence of subclinical carriage of Salmonella in clinically
healthy dogs to range from 0 to 44 % [11,12] and the results of the
current study are in agree with it. The prevalence of subclinical
shedding of Salmonella in apparently healthy household dogs has
been reported for a number of different countries, but it varies.
A study of 150 dogs from Hawke’s Bay, New Zealand showed
an absence of subclinical carriage  which contradicts our
finding. By contrast, a study of 251 dogs visiting parks in three
cities in south-western Ontario, Canada reported Salmonella in
1.2% of the dogs , which is lower than the current finding.
Salmonella serotypes reported in dogs could be due to the
sample size, year of sampling, sampling strategies, and isolation
methods performed, but may also be due to cultural differences
in feeding or hygiene practices or favorable climate conditions
for bacterial growth and survival. The prevalence of Salmonella
in dogs as reported in the literature is also highly variable
depending on the immediate environment in which the animals
live. For example, Salmonella isolation rates from stray dogs
have been reported to be significantly higher than those from
household dogs . Rectal swabs from kennel dogs in Tehran,
Iran indicated that 28 out of 181 (15.5%) were positive for
Salmonella , which is in line with our finding. In a shelter
in Bursa, Turkey 11% of dogs tested positive for Salmonella ,
and in Japan, 5.9% of stray or unwanted apparently healthy dogs
were positive for the presence of Salmonella in their intestinal
contents , the two finding are agree with our finding. In
northern Taiwan rectal swabs collected from 491 stray dogs
in a municipal animal shelter found 6.3% (31 dogs) dogs were
positive for Salmonellae .
However, other studies involving strays or kenneled dogs
show much lower rates of carriage that are not in line with the
findings presented here  failed to detect Salmonellae in the
intestinal contents of stray dogs (n = 100) in Trinidad, West Indies,
and an analysis of rectal swabs collected from kenneled dogs in
Istanbul, Turkey found only one out of 100 (1%) to be positive for
Salmonella , which are far from our current report. Shedding
of Salmonella in feces is also known to be common among the
racing greyhound population. Racing greyhounds in the USA
have been shown to have high rates of subclinical shedding
of Salmonella at 44% , and a more recent study reported
Salmonella in feces from 11% of asymptomatic greyhounds .
The high prevalence of Salmonella that are typically reported in
greyhounds may be traceable to the high-protein raw meat diet
provided for racing. A high prevalence of Salmonella in these raw
meat diets has been reported and identical enterotypes have
been found in the feces of dogs consuming the food, confirming
that the diet is the likely source of Salmonella .
In some instances, the dogs may not be colonized by
Salmonella and may just be passive carriers in which foodborne
Salmonella is transiently passing through the intestines.
However, studies have shown that raw meat diets contaminated
with Salmonella can lead to abortions and high levels of
morbidity and mortality in greyhounds through Salmonella
infection [23,24]. In line to this, two dogs which fed on meat
tested positive for Salmonella in current finding. In this study,
the overall incidence of Salmonella detected in dogs was 17.1%.
The rate of Salmonella isolation is higher than that reported
in Thailand (12.4%) , but one study in USA (20.8%) .
Reported more than our finding. Recently, one study reports very
low prevalence of dog Salmonellosis in midland region of United
Kingdom only one dogs (0.23%) out of 436 dogs , which is
far lower from current finding. This may be due to difference in
study area, level of animal and public health and time of study.
In Ethiopia, a prevalence of 5.3% to 15.4% was reported from
investigation on rural and urban community by .
Current study agrees with upper scale, even though species
variety is there. On the other hand, out of 300 meats sample
examined in Addis Ababa by , 14.7% were Salmonella positive,
which support our finding. However, one study in southern
Ethiopia was carried out on 107 food handler, report only one
person (0.93%) being Salmonella carrier , which far from our
finding. The cross-sectional nature of this investigation meant
that only a single rectal swab sample was analyzed from each dog,
which may be the reason that the prevalence of Salmonella was
low. However, although the prevalence of Salmonella might have
been higher if more than one rectal swab culture was performed
on each dog. The limitations of single rectal swab cultures for the isolation of Salmonella, due to intermittent shedding, are well
documented. Dogs with experimentally-induced latent infection
shed the agent irregularly for the subsequent 3-4 weeks. In rare
cases this shedding continues for up to 100 days [31,32]. Since
the agent is being shed at intervals, sampling times are very
important when searching the carrier status of the dogs and
in the present study we can only conclude that the dogs were
positive or negative for the presence of Salmonella at the time of
In conclusion, this study indicates that the detection rate
in apparently healthy pet dog shedding of Salmonella from the
Western Shoa Holeta Town is high relative to the other species of
animal in the country and this show dogs might play the a role in
spreading of the disease to the human as well as other animalsm
Based up on the above conclusions the following
recommendations are forwarded:
i. Anyone handling a pet or feces from a pet should wash
their hands immediately afterwards with soap and running
water or use an alcohol-based hand sanitizer.
ii. Dog feces should be picked up immediately to prevent
environmental contamination, especially in public areas like
parks where other dogs and children may play
iii. Prevent pets from drinking from puddles, ponds, lakes
or other water sources that may be contaminated with feces
from other animals.
iv. Dogs should be strongly discouraged from eating their
own feces or those of other animals.
v. Feeding a commercially prepared, heat-processed
diet helps to reduce the risk of Salmonella contamination in
the food, but even these products can occasionally contain
vi. Pet food should therefore be kept in a sealed container
and should never come in contact with kitchen surfaces or
food meant for human consumption.
vii. Do not leave wet pet food in dishes at room temperature
for prolonged periods, as this provides ideal conditions for
bacteria of many kinds to grow.
viii. Prevent pets from hunting and scavenging small wild
animals and birds. .
ix. Regardless of these findings, the possibility that dogs
may harbor Salmonella and other Zoonotic pathogens should
not be ignored.