Characterization and Control of Pathogenic Parasites in Nile Tilapia (Oreochromis Niloticus Linnaeus 1758) in Fish-farming Systems in Bungoma County, Kenya
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Date
2020
Authors
Makilla, Davies Mukwabi
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
In Kenya, fish farming has been expanding in recent years, with Government support
through financial and input subsidies to small scale farmers. The sub sector generates
a variety of benefits such as food and nutrition and develops trade. However, the sub
sector faces the challenges of fish diseases, given that the fish production facilities
support high-density living conditions that are favorable for spread of parasitic
diseases. Besides, when fish that is infected is consumed by humans, the humans may
be infected, especially when eaten fresh. Infected fish lowers their market value and
sunctions may also be imposed on fish exports. Knowledge of fish parasites in
aquaculture systems as well as treatment options available would enlighten fish
farmers on the specific actions to take in order to harvest quality fish. The study was
cross sectional carried out in Bungoma County from August 2015 to Decemebr 2017.
The main objective of the study was to characterize and evaluate control options of
pathogenic parasites present in fish farming systems in Bungoma County. Bungoma
County was chosen for this study because it is one of the Counties that has high
potential for fish farming. The County hosts one out of the public fish farms and
hatcheries at Chwele besides authenticated private fish hatcheries. He hatcheries are
sources of fish fingerlings as well as training and demonstration centres for fish
farmers. At every fish pond, six water quality parameters were assessed using a
portable auto sampler. Farmed Nile tilapia was randomly sampled to determine the
pathogenic parasites and bacteria present in various organs. Commercial fish feeds
were also purchased from two fish feed millers in Bungoma County and assessed for
parasite presence. Polymerase Chain Reaction (PCR) and genetic sequencing analysis
were conducted in order to assess the genes responsible for antimicrobial resistance.
The data was entered into Micro Soft Excel (Windows 10) spreadsheet and analysed
by SPSS Software. It was found that there was significant difference only in
temperature of the pond water sampled across the sub counties (F=15.5; df=5;
p<0.001). Helminthes recovered were Pallisentis tetraodontis, Pallisentis spp.,
Acanthocephalus spp., Procamallanus spp. and Philometroides spp. from Nile tilapia
and Cleidodiscus spp. from pond water. Bacteria that were isolated from Nile tilapia
were Vibrio vulnificus, Vibrio parahaemolyticus, Aeromonas hydrophila, and
Pseudomonas aeruginosa. In fish pond water, Aeromonas hydrophila was isolated
while Streptococcus iniae was isolated from fish feeds. Besides, there was a
significant difference in distribution of total viable aerobic colony counts in fish
ponds water across the different sub counties (H=6;df 5; P< 0.041). Furthermore, it
was found that there was significant difference in the distribution of Aeromonas
hydrophila in fish ponds across the different sub counties (H=3;df;P< 0.016). The
external parasites were eliminated by formalin (36% formaldehyde) at concentration
of 25ppm for 1h and Hydrogen peroxide at 75ppm for 30 min. The bacterial isolates
were found to be significantly different in responses to antimicrobial agents (OLR;df=
16; P<0.00). When the bacterial isolates were subjected to PCR, all five bacterial
pathogens isolated from fish, pond water and fish feeds were found to contain blaTEM
gene amplified at 424bp. The sequences blaTEM gene returned 100% identity with
GenBank Accession number; BankIt2236899 Seq1a MN114035 to Seq 9b
MN114052). This study found that the blaTEM gene was present in recovered Vibrio
parahaemolyticus, Aeromonas hydrophila, Pseudomonas aeruginosa and
Streptococcus iniae. It is recommended that Formalin and hydrogen peroxide as well
as potassium permanganate should used to manage fish helminthes in the ponds
Description
A Thesis Submitted In Fulfillment of the Requirement For
The Award of the Degree of Doctor of Philosophy
(Fisheries) In The School of Pure and Applied Sciences,
Kenyatta University
Keywords
Pathogenic Parasites, Oreochromis Niloticus Linnaeus 1758, Fish-farming, Bungoma County, Kenya