You must save this file as Lastname_ Firstname_ JAA. For example: Smith_John_JAA
1. In your own words, describe what problems or limitations you see in the authors’ methodology (8pts).
2. In your own words, describe how the authors analyzed their data. What test/s did they use? 8pts.
How reliable are the results?
Found in the discussion section
3. Explain what the authors suggest as problems with the study that could lead to unreliable results. Include quotation marks around the exact wording, and indicate page number(s) (8pts).
4. In your own words, describe what problems you see in the study that could lead to unreliable results (8pts).
5. In your own words, describe if the conclusions made (about the results) by the author make sense to you? Are the conclusions too
oad or too na
ow based on what was done in the study? (8pts)
The importance of this scientific work
Found in the discussion section
6. Write (in your own words) the significant contributions of the experimental work in this journal article as reported by the authors. This is called
oader implications. This is usually found at the end of the discussion/conclusions section (8pts).
2
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International Journal of Fisheries and Aquatic Studies 2019; 7(2): XXXXXXXXXX
E-ISSN: XXXXXXXXXX
P-ISSN: XXXXXXXXXX
(ICV-Poland) Impact Value: 5.62
(GIF) Impact Factor: 0.549
IJFAS 2019; 7(2): XXXXXXXXXX
© 2019 IJFAS
www.fisheriesjournal.com
Received: XXXXXXXXXX
Accepted: XXXXXXXXXX
DW Wanja
1. Department of Veterinary Pathology,
University of Nairobi, College of
Agriculture and Veterinary Sciences,
Microbiology and Parasitology,
Kangemi, Nairobi, Kenya
2. Sokoine University of Agriculture,
College of Veterinary and Medical
Sciences, Chuo KIKUU, Morogoro,
Tanzania
PG Mbuthia
Department of Veterinary Pathology,
University of Nairobi, College of
Agriculture and Veterinary Sciences,
Microbiology and Parasitology,
Kangemi, Nairobi, Kenya
RM Waruiru
Department of Veterinary Pathology,
University of Nairobi, College of
Agriculture and Veterinary Sciences,
Microbiology and Parasitology,
Kangemi, Nairobi, Kenya
JM Mwadime
1. Department of Veterinary Pathology,
University of Nairobi, College of
Agriculture and Veterinary Sciences,
Microbiology and Parasitology,
Kangemi, Nairobi, Kenya
2. Sokoine University of Agriculture,
College of Veterinary and Medical
Sciences, Chuo KIKUU, Morogoro,
Tanzania
LC Bebora
Department of Veterinary Pathology,
University of Nairobi, College of
Agriculture and Veterinary Sciences,
Microbiology and Parasitology,
Kangemi, Nairobi, Kenya
PN Nyaga
Sokoine University of Agriculture,
College of Veterinary and Medical
Sciences, Chuo KIKUU, Morogoro,
Tanzania
HA Ngowi
Sokoine University of Agriculture,
College of Veterinary and Medical
Sciences, Chuo KIKUU, Morogoro,
Tanzania
Co
espondence
DW Wanja
1. Department of Veterinary Pathology,
University of Nairobi, College of
Agriculture and Veterinary Sciences,
Microbiology and Parasitology,
Kangemi, Nairobi, Kenya
2. Sokoine University of Agriculture,
College of Veterinary and Medical
Sciences, Chuo KIKUU, Morogoro,
Tanzania
Bacterial pathogens isolated from farmed fish and
source pond water in Kirinyaga County, Kenya
DW Wanja, PG Mbuthia, RM Waruiru, JM Mwadime, LC Bebora,
PN Nyaga and HA Ngowi
Abstract
Bacterial infections cause low to high mortality in fish, affecting the productivity of aquaculture. This
study aimed at determining the occu
ence of bacterial pathogens in farmed tilapia, catfish, goldfish and
koi carp and source pond water in Kirinyaga County. A total of 181 healthy-appearing fish and 27 water
samples from randomly selected fish farms in the county were processed. Bacteriological isolation was
done on aseptically collected skin and kidney swabs; gills and a portion of intestines from each fish and
water samples. Isolated bacteria were identified by colony morphology, Gram stain and biochemical
characteristics, and some further characterized using API-20E kit. A total of 329 bacterial isolates were
ecovered from fish organs and 39 from pond water samples. They belonged to 17 genera with 18
different identified bacterial species. The most prevalent species found on the skin, gills, intestines,
kidney, and water samples belonged to five genera: Proteus spp. (14.9%), Aeromonas hydrophila (8.2%),
Aeromonas caviae (6.3%), Plesiomonas (5.2%), Flavobacterium spp. (5.2%), Aeromonas so
ia (4.3%)
and Micrococcus spp. (4.3%). Some isolates (11%, n=42) could not be identified. Bacterial species
ecovered from fish samples were also found in the water samples except: Streptococcus spp.,
Pseudomonas luteola, Se
atia plymuthica and Klebsiella oxytoca. Raoultella te
igena was recovered
from water samples only.
The study has shown that farmed fish and aquatic environments ha
or potentially pathogenic and
zoonotic bacteria which may cause significant fish diseases and public health risks. Therefore, there is
need to implement stringent management and biosecurity programs.
Keywords: Bacterial infections, aquaculture, fish diseases, public health, biosecurity
1. Introduction
Kenya has fast growing fish species (Oreochromis niloticus, Clarias gariepinus and
Oncorhynchus mykiss) aquaculture industry. The country is among the major aquaculture
producers of sub-saharan Africa, with an industry dominated by tilapines [1]. The capture and
wild fisheries contributes 0.8% of the Gross Domestic Product (GDP), providing direct
employment opportunities to over 500,000 people and supporting over two million people
indirectly [1]. However, fish supply in Africa has been declining for a number of reasons while
the demand has increased due to rapidly growing human population. In an effort to reverse
these trends, aquaculture projects have been massively promoted across the continent, Kenya
included. This is characterized by a record growth extensive small scale to intensive large
scale fish farms over the last decade. One significant setback for rapid intensification in
aquaculture is risk of diseases, caused by parasites [2-4], viruses [5], fungi [6] and bacteria.
Although aquaculture may not be exclusively implicated for the rising disease concern in
fisheries, it does provide key insights into: how the diseases may be spread, maintained and
whether it is significant enough to elicit action. Of the diseases, bacteriosis remains the most
damaging to fish production globally due to economic significance of diseases they cause [7].
There has been a steady increase in the number of species of bacteria implicated in causing
fish diseases. An estimated 125 different bacterial species belonging to 34 different bacterial
families has been reported to cause various fish diseases globally [8], including: Aeromonas
spp., Vi
io spp., Pseudomonas spp., Yersinia spp., Flavobacterium spp., Renibacterium spp.,
Mycobacterium spp., Edwardsiella spp., Citrobacter spp. and Streptococcus spp. [9]. However,
there is growing indication that the pathogenic species spectrum as well as the geographic and
host range is widening among fish pathogens [10], leading to the emergence of new pathogens.
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International Journal of Fisheries and Aquatic Studies
Most documented cases of fish diseases in Kenya have
na
owed their focus to parasitic infections in capture and
wild fish [11], and may thereby miss out on potentially
important disease-causing bacterial microbes. Concomitant to
this; it is essential to monitor the health of fish stock so as to
produce fish that is safe for human consumption There is
scarce information available on the occu
ence of bacterial
pathogens affecting the aquaculture sector in Kenya. While
most published studies have focused on isolation of single
acteria species; this study aims to isolate and identify
common bacterial pathogens in farmed food and ornamental
fish and pond water in Kirinyaga County, Kenya. Studies on
aquatic bacterial flora would provide information relevant in
developing more stringent biosecurity and sanitary measures.
2. Materials and Methods
2.1 Ethical approval
This research work was approved by the Faculty of
Veterinary Medicine Biosafety, Animal use and Ethics
Committee for Experimentations on live non-human
verte
ates, University of Nairobi, Kenya.
2.2 Study area and design
A cross sectional study was ca
ied out where fish and water
samples were collected from five sub-counties of Kirinyaga
County, between December 2017 and April 2018. The sub-
counties involved were Mwea East, Mwea West, Ndia,
Gichugu, Kirinyaga West and Kirinyaga Central (Figure 1).
Bacteria were isolated from the sampled fish and source pond
water and identified by colony morphology, Gram stain and
iochemical characteristics, while some were further
characterized using Analytic Profile Index (API) 20E
microorganism identification kit.
Fig 1: Kirinyaga County map showing the five sub counties (stars)
visited during the study. Map modified from Serede et al. [12].
2.3. Sampling procedure and sample size
Simple random sampling was used to select active and
available farms in the study area. The sample size was
calculated using the formula given by Naing et al. [13];
, where n is the sample size, Z is the Z statistic
for a level of confidence (1.96 for 95%), P is expected
prevalence (assumed pathogen prevalence level of 50%) and d
is the precision, which is equal to 5% XXXXXXXXXXThis gave a
sample size of 384. However, only 208 samples comprising:
88 tilapia, 53 catfish, 30 goldfish and 10 koi carp and 27
source pond water samples were collected, owing to
limitations in resources and time. Fifteen grow-out farms and
five
eeder farms were sampled based on availability and
consent of farmers and number of active fish ponds. To obtain
a proportional sample, 5-10 fish were purchased per pond
from selected farmers. Live fish were transported to Kerugoya
County Veterinary Department Laboratory for necropsy in
sterile 18 litre buckets.
Surface pond water samples were collected from the same
ponds where fish sampling was done. The water samples were
collected aseptically using a sterile 50ml screw capped
universal glass bottles, submerged 15cm to 20 cm below the
water surface at every sampling. Bottles with water samples
were labeled accordingly. Water samples were placed in a
cool box packed with ice, then transported to laboratory