A STUDY OF PREVALENCE OF FISH PARASITE IN HASHENGE LAKE, TIGRAY, ETHIOPIA

This study was conducted at Lake Hashenge, Tigray, Ethiopia from the period of November to April 2009 to identify parasites of fish. The objective of this study was to identify parasite of fish at Lake Hashenge to determine the prevalence of parasitic disease of fish, to have baseline information fish parasite in The lake Hashenge. A total of 442 different species of were sampled. These include 217 of Mirror carp and 225 of Oreochromis niloticus. The fish were thoroughly examined both externally and internally for the presence of parasites. The major parasites identified were CLinostomum species from 96(44.2%) of Mirror carp and 64(28.4%) of Orechromis niloticus. Clinostomum species were recovered from the feaces of the fish (gastrointestinal tract). The nematode genera of capillaria identified from the GIT of 13(6%) Mirror carp and 14(6.2%) Oreochromis niloticus. The genera of Acanthocephalus were recovered from the GIT of 29(13.4%) of mirror carp and 25(11.1%) Oreochromis niloticus. The adult of the genera camllanus was recovered from 20(9.2%) of Mirror carp and 27(12%) of Oreochromis niloticus. The P> 0.05 in the comparison between the fish species, sex, with genera of the parasite but the P<0.05 in the comparison between sample source and occurrence of the parasites.


INTRODUCTION
Fish are the most diverse group of vertebrates occupying a variety of marine and fresh water habitat; they are coldblooded or poikilothermic animals. Their body temperature varying passively in accordance with the temperature of the surrounding water. Although fish as a group are tolerant of a wide range of temperatures. From just below zero degree centigrade up to 45 degrees centigrade. Individual species generally have a preferred optimum as well as a more restricted temperature range .fish has enormous importance to human beings. They provide food for millions of people, in addition fish are important in the balance of nature, and they eat plants and animals and in turn become food for plants and animals. That s way fish helping in the balance of the total number of plants and animals on the earth (Fronson, 1916).
Catch fish industries has declined significantly and decline is due to a series of factor which include over fishing, loss of fish habitants and environmental pollution. Disease out breaks (infectious and non infectious) resulting high mortalities occur more often when fish are held under relatively crowded and confined conditions. Also mass mortality of healthy fish may occur even under good environmental conditions when an infectious agent is accidentally introduced in to the culture system (Freders, 1195).
Water is the most important constituent in which fish are stocked, fed and raised and into which their waste products are voided, changes in the environment affect fish more rapidly and profoundly than terrestrial animals. The adaption of the aquatic habit has many implications for the structure and physiology of fish. The higher density of water when compared with air makes the streamlining and shaping of the body on important prerequisite for successful aquatic life. Each species of fish has preferred ranges for the various parameters of water quality, such as temperature, dissolved oxygen and salinity and ideally the fish should operate at the optimum levels of each parameter to achieve fast growth and efficient performance (Nagasawa, 1979).
Ethiopia possesses many lakes which are important for the habitant of fish. In Ethiopia they are over 100 species of fish which are identified. Ethiopia has many lakes, but their contribution to the economy of the country is insignificant. The main factors which influence health, growth and survival of fish are water quality, environmental changes, manmade problems and presence of competitive aquatic host inside the habitat (Edward, 1978). Lakes are exposed to many pollutants including untreated sewage, agricultural and industrial wastes which enhance the concentration of heavy metals and compromise the health status of fish and its growth at regular period. In developing countries farmers found around the lake send their animals (sheep, cattle, horse, and donkey) towards the lake for the grazing and drinking purpose. These animals defecate and urinate at the shore or bank of the lake which serves as the main source of pathogen for fish health. In addition to this farmers wash their cloth at the border of the lake by using detergents which are harmful for growth and survival of fish (Donald, 1993).
Fish have a very full complement of disease like all animals with which to contend and many of these are due to external agencies which others arise internally .from external source such as viruses, bacteria, fungi and parasites are known to affect fish while internally they suffer from almost all the common organic and degenerative disorders such as noeplastic conditions in water, from predators and the capturing devices of fishermen even if they are not killed by disease or disordered (Lagler etal,1971).
Fish parasites can spoil the appearance of fish that result in consumer rejection. In our country there is no experience of farming of fish in inland waters of the country at this stage and no knowledge of disease in fish to be formed in these waters along with the growing interest in the development of disease as one of the major detrimental factors in culturing of fish. At present prediction of potential health hazards in largely extrapolated from data available on fish disease and infections in natural and semi natural habitants (paperna, 1980). Mucosal tissue is damaged at the attachment site, in fibroplasias that may extend through the sub mucosa and into the muscularis. Occasionally perforation of the gut wall occurs, the mucosal epithelium frequently is compressed or eroded along the trunk of the worm and the tips of the villi may be absent. Destruction of intestinal villi and necrotic, degenerative changes in mucosal epithelium almost certainly will reduce the absorptive efficiency of the fish intestine (Bullock, 1963).
Acanthocephalans lack an alimentary tract and hence uptake of nutrients derived both from leakage of host tissues and from dietary contents in the intestinal lumen of the host is through the tegument. Hydrolytic enzyme activity at the tegumental surface probably assists in obtaining nutrients and in rapid penetration by the worm. Some acanthocephalans penetrate deeply and induce formation of a nodule that extends in to the coelom of the host. Such nodules are extensively vascularaized. Increased leakage of proteins from the blood in to the nodules ensures steady supply nutrients for parasite (Chubb, 1982). The consequences of acanthocephalans induced reductions in energy efficiency and altered basal metabolism of host are likely to be focused more sharply with increasing emphasis an aquaculture (Bristol, 1984). Digenetic trematode is one of the major fish parasitic platyhelminthes. Digeneans require more than one host to complete their life cycle and their adult stage is parasitic in vertebrates. All major groups of vertebrates serve as hosts for adult digeneans. Aside from being hosts to adult digeneans, fish may be also be infected by the metacercarial larval stage. With one exception, mollusks; members of the genus aporocneotyle complete their larval development in polychaete annelids (Donges, 1974).
Metacercarial infection in fish is the main source of disease with subsequent economic loss. Metacercariae may affect growth and survival, or disfigure fish so that they lose their market value as a food or ornamental product (Parna, 1980). Digenean infection of fish required by direct cercariae penetration are linked to seasonal occurrences of snails and their levels of infection (Brooks, 1985).
Adult stage digeneans have a dorsoventrally flattened oval body with a smooth, spiny or corrugated surface, a sucker around the antero-ventral mouth and an additional ventral sucker or acetabulum. Both suckers used for attachment and locomotion. The digestive system consists of a pharynx connected to the mouth opening a short esophagus and two blinded intestinal caeca. The excretory system includes flame cells connected to a duct network which is connected to a posterior opening bladder. Most trematodes are hermaphroditic (with crossinsemination). The male system consists of testes, vasa effrentia and vas deferens, and a cirrus pouch containing a seminal vesicle, ducts, ejaculatorius and prostate glands. The female system is comprised of an ovary and paired vitellaria, an oviduct, vitelline ducts (Dollfusetal.1974).
So far, very few diseases have been described from fish of Ethiopian waters. Moreover there is no experience in farming of fish in inland waters of the country at this stage and no knowledge of disease in fish to be farmed in these waters (Eshetu, 2000).
Therefore, the objective of the current study is:  To identify the parasite of fish in lake Hashenge.  To determine the prevalence of parasite disease of fish in Hashenge.  To have base line information about fish parasites in the lake.

The study area
The study was conducted in Hashenge lake which is found in southern part of Tigray, Ethiopia, particularly in the woreda Ofla near to the town of Korem, which is 150 Km faraway from Mekelle, the capital city of Tigray region. The lake is oval in landscape and covering an area of 20 Km2 and the capacity the lake to contain water is supposed to be 22.6X108 m3. Hashenge Lake is the largest lake from Tigray region and has an average depth of 21 meter. The woreda Ofla has an annual rain fall of 800-900 mm and temperature in the range of 15-16 c0 and is located at longitude of 390 (east) and latitude 12031' (north). It has an altitude of 2450m above sea level. lake is natural and used as water source for both human being and animals, irrigation of agricultural land and nowadays used for fish farming system however before nine years the lake was not used for farming of fish because it did no has its own original fish species, but the agricultural bureau of Tigray region had been introduced fish species from other lakes of Ethiopia.

Study animal
The study population was different fish species (Oreochromis niloticus or Nile tilapia and Mirror carp) found at Lake Hashenge.

Study design
A cross sectional study was conducted from November 2008 to Aprill 2009 at Hashenge lake to determine the types of fish species and the prevalence of parasitic infestation or infection of fish .The desired sample size was calculated using the formula given by Thrusfield, 1955. 95% confidence interval, 5% desired absolute precision was considered as statically significant at 50% expected prevalence and by which 384 fish were sampled. But 15% was added to increase the precision of the estimated prevalence of the disease. Therefore, 442 fish were selected (formula step given below) using random systematic sampling method.
N=1.96 2 X P ex (1-P ex ) d 2 Where N= required sample size; pex =expected prevalence d 2 =desired absolute precision

Questionnaire survey
Questionnaire format was developed to gather information regarding the dominant fish species in the lake, the origin of fish where they came from and to assess for any incidence of loss of the lake population (fish species) and administered to 60 persons that include fishermen (n=20, 33.3%), restaurant workers (n =15, 25%) and farmers (n=25, 41.7%) and all of them were living at the villages vicinity to the lake.

Study methodology 2.5.1 Sample collection
A total of 442 fish were sampled and of which 217 Mirror carp and 225 Oreochromis niloticus species of fish were examined. All the fish were caught using gillnets with mesh size ranging from 60 to 120 mm that was used for the fishing practice at the lake Hashenge. All the specimens taken from fish were preserved in 10% formalin until it reaches to the place of laboratory examination, Mekelle University College of veterinary medicine parasitological laboratory. During the process of sampling, fish species, sex and site of sample taken was identified and recorded.

Sampling procedure
The fish were examined thoroughly both internally and externally after it has been taken out by the fisherman from the lake, scraping were taken from the skin and fin ,preserved in 10% formalin and sample was taken from the gill and gastro-intestinal tract. An incision was made from the ventrum to the head then faeces have been collected from the small and large intestine.

Laboratory examinations
Skin scraping was taken from randomly selected fish type particularly from the route of the fin. The skin scraping has been preserved in 10% formalin and taken to the laboratory. In the laboratory scrapings were dissolved with 10% KOH and smear was examined using the 10x magnification power of the light microscope. Any sample which was not showing the typical intact parasites or whole egg was considered to be negative. Fecal direct to microscopy procedure was conducted to see parasitic eggs, larvae and adult parasites from the specific samples from each fish species. Fecal sedimentation and floatation techniques have been carried out to identify parasite egg and adults. Gill samples were also examined to assess external parasitism.

Data analysis
The obtained data from questionnaire survey and laboratory findings were summarized and then analyzed using simple mathematical calculations and SPSS version 10 analyzing software to calculate the prevalence rate of the parasitic infestation in the study fish species and chi-square test was calculated to test association between the fish species, sex and site or sample source with the occurrence of parasitic infestation.

Parasitological survey
The species Clinostomum were the most prevalent parasites affecting both species of Fish at Hashenge Lake.     As seen from table 3, there was no any significant (X 2 = 6.345, P (z) > 0.05) variation among the sex categories of the prevalence rate of the parasite.  Hashenge Lake was a dead sea which has not its original fish but according to the Questionnaire survey the fish species present in lake were brought from Lake Haik, 272 Km far from Mekelle, and this was supported by 55% of the respondents while 28.33% of the respondent said from Lake Tana. The questionnaire survey indicated that there was an outbreak in 1993 E.C. all the fish have been found dead but the cause of mortality was not known and this previous history of the occurrence of death was supported by 41.67% of the respondents. On the other hand, 58.33% of the respondents replied that they did not have any information about such phenomenon.

DISCUSSION
The helminthes egg parasites belonging to the genera Clinostomum, Capillaria and Acanthocephalus and the adult stage of the genera Camallans was found in the study fish species. The study was conducted in a total of 442 fishes from Lake among which 217(49.1%) were Mirror carp and 225 (50.9%) were Oreochromis niloticus. From the total examined fishes, 290(65.6%) was found to be positive for the genera of parasites. Comparisons were made among each other of the different variables.
The most prevalent egg of trematode was the egg of the genus Clinostomum which was recovered from the gastrointestinal of Oreochromis niloticus (28.4%) and Mirror carp (44.2%). The genus Clinostomum was the most abundant parasites found in the Oreochromis niloticus and Mirror carp. This finding of study was consistent the finding recorded by Teferra wondum (1990), with a prevalence rate of 74.3% in Oreochromis niloticus and 42% in the Mirror carp at Lake Tana. These findings were slightly higher than the finding of the current study in which prevalence rate of 28.4% for Oreochromis nilloticus and 44.2% for Mirror carp was identified. This difference in prevalence rate may be due to management of the water quality, feeding habits and overcrowding of fishes, presence of aquatic birds that contribute to the exposure of fish to the parasite (Anderson, 1992).
The nematode of Camallanus was found from 20(9.2%) of Mirror carp and 27(12%) of Oreochromis niloticus in the present study at the study lake. The result of current study agrees with the Fujita (1927) and is reported from fresh water fishes in Japan and is reported from many hosts from many countries. Nematode usually considered as the most economically important parasite of fishes of the world (Hafsteinsson and Rizvi, 1987).
The questionnaire survey revealed that the total respondents participated in the study were provided with query type of disease outbreak in the lake previously, about the origin and type of fish species and dominant fish species in the lake at present. Since fish is the main source of protein as food for human being great consideration should be given to the health status of the fish but in developing countries like Ethiopia, Fish farming is not greatly practiced (Bullock, 1963).
Famers who are dweller in the surrounding of Lake Hashenge do not consume fish meat. From the total respondents interviewed; 41.6% of them stated that there was an outbreak of fish disease in the lake while 58.33% of the respondents replied that they did not have any information about such situation of occurrence of disease outbreak in the lake. The most dominant fish species in the lake were Mirror carp and Oreochromis niloticus.

CONCLUSION AND RECOMMENDATIONS
Fisheries have a very full complement of disease like all animals. The disease may be due to internal and external sources. The present work which was conducted in Hashenge Lake, Tigray region, revealed that the prevalence of the parasites that affect fish were high, this may be due to lack of management of the lake and shortage of education about the importance of fish as source of food. The contribution of the farmers to the lake management was very poor and no attention was given to it at all. Based on the above conclusion the following recommendation was forwarded:  Creation of awareness about the importance of fish as source of food for society  Good water and environment management of the lake  Fish species which can be best fit to the climatic condition of the study area and water ecosystem should be selected and introduced to lake.  The governmental should be involved in the overall management of the water body and financially support for the successful start of fish production from the lake as to the desired level.  Training of fishery professionals about the occurrence of fish diseases should be practiced and further research should be conducted in order to increase the productivity of the lake.