Prevalence and pathology of protozoan and monogenean parasites from fry and fingerlings of cultured Clarias gariepinus (Burchell, 1882) in Uganda

Aquaculture is considered the best option for the dwindling capture fisheriesin Uganda. Among the economically important aquaculture fish specieswith very successful breeding technologies is African catfish, Clariasgariepinus. However, farmers are constraint with massive fry and fingerlingmortalities, especially in intensive culture system. Despite the fact thatparasites and diseases are reckoned to be the causes of these mortalities,little has been done to authenticate this claim in Uganda. Therefore thisstudy investigated the cause of mortalities with the aim of establishinginformation on the prevalence and pathology of Protozoa and Monogeneaparasites occurring on C. gariepinus. Using routine parasitological andhistological techniques, a total of 334 fry and fingerlings of cultured C.gariepinus from three hatcheries were examined for parasite infestations.Five ectoparasites and one endoparasite species were recorded. Of these, theprotozoan Trichodina sp. and the monogenean Gyrodactylus sp. were thedominant parasites. The major routes of entry of parasites into the hatcherieswere through surface water supply and possibly via the semi aquaticorganisms like amphibians. During initial stages of infection, the prevalence,mean intensity and mean abundance of these parasites increased with fishage. At the later stage, Trichodina sp. declined probably due to hostresistance and competition for space with Gyrodactylus sp. Trichodina spappeared less susceptible to the 40ml/l formalin treatment thanGyrodactylus sp. Major pathological changes observed were oedema andhyperplasia in the gills, infiltration of melanomacrophage centers into theskin epidermis and mild epidermal cell hypertrophy of parasitized fish.Hyperplasia and oedema of gill and subsequent gill fusion seem to haveinterrupted respiration and hence caused death of the host. Concomitantoccurrence of Trichodina sp. and Gyrodactylus sp. aggravated pathologicaleffects on fish thus increasing mortality. Epistylis sp., Apiosoma sp. andTrichophrya sp. were considered less pathogenic. The results werediscussed in relation to parasite occurrence and parasite induced fishmortalities

Infection dynamics of Cichlidogyrus tilapiae and C. sclerosus (Monogenea, Ancyrocephalinae) in Nile tilapia (Oreochromis niloticus L.) from Uganda.

The infection dynamics of the gill monogeneans Cichlidogyrus tilapiae and C. sclerosus on Oreochromis niloticus with respect to habitat type (reservoir, stream, ponds and cages), host sex, size and seasons was determined between January and November 2008. During the study period, 45.2% of the 650 fish examined were infected with Cichlidogyrus spp. The infected hosts harboured an average of 8.6 \ub1 3.4 parasites/fish. Across habitat types, the proportion of infected fish was not statistically different. In contrast, the number of parasites recorded on infected fish from different habitat types differed significantly. The highest parasite number was recorded in reservoir-dwelling fish and lowest in stream-dwelling hosts. Concerning sex, more female O. niloticus were infected and harboured a high number of parasites than male and sexually undifferentiated fish. A weak negative relationship was found between rainfall and monthly parasite infections. However, a higher number of parasites and proportion of infected hosts were found during dry than in wet seasons, except in ponds. Results of this study show that differential exposure due to changes in fish behaviour associated with habitat modification and sex may account for the infection difference across the sampled sites. Meanwhile, rainfall and the associated hydrological events are important factors regulating monogenean infections in tropical aquatic environments. The continuous presence of Cichlidogyrus spp. in fish provides evidence of possible parasite outbreaks, indicating the application of biosecurity measures as crucial for the success of intensive fish farming

Veterinary and public health aspects in tilapia (Oreochromis niloticus niloticus) aquaculture in Kenya, Uganda and Ethiopia.

SUMMARY - The European INCO-DEV BOMOSA Project (Integrating BOMOSA cage fish farming systems in reservoirs, ponds and temporary water bodies in Eastern Africa) intends to establish small scale fish farming in marginal water bodies in Kenya, Uganda and Ethiopia, creating rural aquaculture networks with the aim to economically integrate aquaculture with agriculture. In order to study veterinary and public health aspects in Bomosa fish farming systems, a parasitological survey on wild and cultured tilapias (Oreochromis niloticus niloticus) has been carried out from March 2007 to October 2008. A total of 982 tilapias - 685 from Kenya, 222 from Uganda and 75 from Ethiopia - were sampled and subjected to complete parasitological examination. During the survey, fish from different environments (258 from open water reservoirs, 445 from ponds and 279 from BOMOSA cages) were sampled in order to evaluate the factors which could influence the parasite diffusion and outbreak of diseases. Quantitative data, such as prevalence, intensity and abundance, and qualitative data are presented together with the main abiotic and biotic risk factors identified as relevant for veterinary and public health aspects in tilapia aquaculture. RIASSUNTO - Nell\u2019ambito del progetto europeo INCO-DEV \u201cIntegrating BOMOSA cage fish farming systems in reservoirs, ponds and temporary water bodied in Eastern Africa\u201d si \ue8 condotto uno studio sui fattori sanitari di carattere strettamente veterinario e di potenziale interesse in sanit\ue0 pubblica che possono interessare l\u2019allevamento della tilapia (Oreochromis niloticus niloticus) in Kenya, Uganda ed Etiopia. Sono state sottoposte ad esami necroscopici e parassitologici 982 tilapie - 685 dal Kenya, 222 dall\u2019Uganda e 75 dall\u2019Etiopia. Dei soggetti esaminati, 258 provenivano da acque libere, 445 erano allevati in bacini in terra e 279 in gabbie galleggianti approntate secondo il sistema \u201cBOMOSA\u201d, sperimentato nell\u2019ambito del progetto al fine di garantire un migliore sfruttamento di risorse idriche marginali e temporanee e una gestione semplificata da parte delle comunit\ue0 locali. Vengono presentati i risultati quantitativi (prevalenza, intensit\ue0, abbondanza) e qualitativi delle indagini parassitologiche, unitamente alla descrizione dei fattori di rischio abiotici e biotici individuati in relazione agli aspetti veterinari e di sanit\ue0 pubblica che possono interessare le tilapie allevate nei sistemi acquatici presi in considerazione