High Burden of Gastrointestinal Helminth Parasites in Catshes: Clarias gariepinus and Heteropneustes fossilis

Objective: Catshes harbour a greater variety and occurrence of larval helminth parasites because they are exposed to more infective helminth larvae in their diet due to their predatory habit which makes them more susceptible to higher parasitic burden. This study was conducted at department of zoology in Post Graduate Campus, Biratnagar, Nepal to determine the prevalence of helminth parasites in the gastrointestinal tract of two species of catshes i.e Clarias gariepinus and Heteropneustes fossilis collected from the different water resources of Biratnagar, Eastern Nepal. Results: Out of 280 sh examination, 264 (94.28%) shes were found to be infected with helminths parasites. Clarias gariepinus infection rate was 84.0% with three species of parasites, one each of nematode i.e. Procamallanus laevionchus, cestode i.e. Proteocephalus species, and trematode i.e. Allocreadium species. Heteropneustes fossilis have prevalence rate of 100% with ve species of helminth parasites i.e. two nematode species namely Procamallanus heteropneustes and Eustrongyloides species, one cestode namely Lytocestus indicus, one trematode i.e. Phyllodystomum folium and an acanthocephalan i.e. Pomphorhynchus species were detected.


Introduction
Cat sh belongs to the order Siluriformis which are basically found to be bottom dwellers with feeding habit of almost all kinds of aquatic plant and animals as a natural food [1]. Cat shes are cultivated widely because of its high market value and due to its attractive bene ts such as high growth rate, easy to cultivate as it consume arti cial food easily and have less chance of losses due to its high resistant power to different diseases and environmental change. Cat shes are also considered as one of the most common and affordable source of animal proteins [2]. Due to air-breathing nature of cat shes, they can survive low aerated water bodies and at commercial level, its production can be achieved without arti cial aeration cost [3]. Clarias gariepinus, commonly known as African cat sh, is found in all from of freshwater and their importance has been increased in aquaculture for its high growth rate and low production cost with a cheap source of animal protein in human diet [4]. Heteropneustes fossilis is also known as stinging cat sh. This sh is also has a high consumer demand due to its good taste as it has fewer intramuscular spine with higher resistant to low oxygen content which makes it easy for cultivation [5].
Nowadays, parasitic infection has been considered as one of the important factor for economic and production losses in the sh culture due to sh mortality, reduction in sh growth and fecundity as well as increasing the vulnerability of sh to other diseases [6]. Luque and Poulin have also stated that cat shes harbour a greater variety and occurrence of larval helminth parasites because they are exposed to more infective helminth larvae in their diet due to their predatory habit which makes them more susceptible to higher parasitic burden [7]. Only few studies have been carried out on helminth parasites of fresh water shes of Nepal and in my knowledge no studies have been conducted on burden of gastro-intestinal helminth parasites of cat shes found in Nepal. Therefore, this study was designed to detect the occurrence and burden of helminth parasites present in the gastrointestinal tract of two cat shes i.e. Clarias gariepinus and Heteroponeustes.

Methods
This study was carried out in the Department of Zoology, Post Graduate Campus, Tribhuvan University, Biratnagar, Nepal over a period of six months (May 2017 to October 2017). Biratnagar is the capital city in Eastern Nepal having geographical location 26°28'60"N 87°16'60"E. It lies 399 km east of Nepal's capital, Kathmandu and 6 km north of the broder of the Indian state, Bihar. The shes were collected from different fresh water ponds and rivers near Biratnagar area. Cat shes were also randomly collected from local sh market of Biratnagar. The shes were washed properly in clean water and then transported in a clean plastic bag to the Zoology Laboratory of Post Graduate Campus, Biratnagar for further study.
The shes were dissected and the gastrointestinal tract was separated from the visceral mass of the body and kept in the Petri dish. The food tract was cut into pieces of one centimetre each for observation of helminths. The cut parts were placed in Petri dishes containing saline water. Each piece of the intestine was further carefully slit opened for the emergence of any adult parasites. The gut content was further observed under microscope by simple wet mount preparation for search of various helminth parasites.
The remaining gut content was preserved in formalin in vials. The external and internal morphological characters of each worm were recorded and identi ed by using standard keys [8][9][10].
Data were analyzed using statistical package for the social science (SPSS) version 16.0 and interpreted according to frequency distribution and percentage. Data were recorded regarding the prevalence of helminth parasites in two cat sh. The prevalence of helminth parasites was calculated according to Margolis et al [11], where, prevalence (p) = the number of infected host with one or more individuals of a particular parasites species divided by number of hosts examined (expressed in percentage).

Results
In this study, a total of 280 cat shes were examined for gastrointestinal helminth parasites which included Clarias gariepinus (n = 100) and Heteroponeustes fossilis (n = 180). Out of 280 cat shes included in the study, 264 (94.3%) were found infected. Among the two species of cat sh examined for their gastrointestinal helminth parasites, Clarias gariepinus was found to be infected by nematodes, cestodes and trematodes while Heteroponeustes fossilis was infected by all four groups of helminth parasites (Table 1).

Discussion
Parasitic diseases of sh result in great economic loss due to effect on normal health conditions of shes, reduction of growth, abnormal metabolic activities and even death. The factors that directly in uence the parasitic fauna of shes are age, diet, abundance of shes, independent number of a parasite within sh and season. The characteristic of any water body can in uence and determine its parasitic fauna and when environmental conditions become suitable for mass reproduction of parasites, the parasitic diseases may spread very quikly [12]. Thus, proper identi cation of sh parasites, their prevention and correct therapy for treatable infestations dramatically improve the health and productivity of affected sh. In the present study, two species of cat sh found in Biratnagar area of Nepal were examined for occurrence and burden of gastrointestinal helminth parasites.
Among 100 Clarias gariepinus examined, 84.0% were found to be infected with helminth parasites. Three parasites were detected from gut content of this sh i.e. one nematode species, one cestode and one digenean treamtode. This result is in conformity with some other studies. Dan-kishiya and Zakari [13] reported nematode, cestode and trematode in wild Clarias gariepinus in Gwagwalada, Nigeria. Aliyu and Solomon [14] and Salawu et al [6] also detected some nematodes, cestodes and trematodes from Clarias gariepinus. The prevalence was 75.0% in study of Salawu et al [6], 59.4% in the study of Aliyu and Solomon [14], and 67.5% in the study of Kawe et al [4]. Difference in prevalence of parasites in sh may be due to many factors. Williams and Jones [15] suggested that parasitism is determined by the interaction between both biotic and abiotic factors and differs in various aquatic ecosystems. Reports have shown that helminths are generally found in all freshwater shes, with their prevalence and intensity dependent on factors of parasite species, host and its feeding habits, hygiene of the water body, and presence of intermediate hosts for the parasites [4].
In the current study, nematode species i.e. Procamallanus laevionchus was detected from 46.0% Clarias gariepinus and have higher burden than cestode namely Proteocephalus species (21.0%) and digenean treamtode i.e. Allocreadium species (17.0%). The higher incidence of nematodes than cestodes and trematodes revealed that nematodes were the commonest cause of parasitic infection in Clarias gariepinus and this is in conformity with with the ndings of Kawe et al [4] and Aliyu and Solomon [14]. Kawe et al [4] also detected Allocreadium species from 3.6% and Procamallanus laevionchus from 32.5% of Clarias gariepinus. Barson and Avenant-Oldewage [16] reported Proteocephalus species from 14% of Clarias gariepinus. Multiple infections by the helminth parasites was commonly seen in Clarias gariepinus. Among total Clarias gariepinus, Procamallanus laevionchus and Proteocephalus species were concurrently detected from 15.0% sh. Ajala and Awole [17] also reported multiple infections of helminth parasites in the gastrointestinal tract of Clarias gariepinus.
The cat sh culture in Nepal is of great signi cance because of highly nourishing and easy source of protein. Parasites attack the sh and destroy them and/or produce disease in their bodies, thus making them unedible. The stinging cat sh i.e. Heteroponeustes fossilis was also examined and all of them were found to contain some helminth parasites in their gastrointestinal tract with prevalence of 100%. Five parasites were detcted from gut content of this sh. Two nematode species namely Procamallanus heteropneustes and Eustrongyloides species were detected from 37.8% and 30.0% shes respectively. One cestode namely Lytocestus indicus (21.7%), one trematode i.e. Phyllodystomum folium (23.9%) and an Acanthocephalan i.e. Pomphorhynchus species (100%) were detected from the Heteroponeustes fossilis. Other studies from different countries also repoted variable prevalence of various parasites from gastrointestinal tract of Heteroponeustes fossilis. Yadav SN [9] also detected Pomphorhynchus species from gastrointestinal tract of 100% of Heteroponeustes fossilis, which is similar to the result of current study. In the study of Nimbalkar et al [18], the prevalence of Eustrongyloides larvae was 50% in this sh. Similarly, Ningthoukhongjam et al [19] identi ed cestode parasites from intestine of 50% of Heteroponeustes fossilis and Gupta R [20] reported Procamallanus heteropneustes from 31.3% and Lytocestus indicus from 5.7% of Heteroponeustes fossilis. Puinyabati et al [21] clearly discussed that the species and feeding activity of the sh host and the preference and composition of the food play an important role in the diversity of the helminth parasites in the gastrointestinal region of shes.
The present ndings con rm that helminth parasites are widespread in the gastrointestinal tract of cat sh found in the Biratnagar area of Nepal and the prevalence of helminth parasites is higher with heavy parasitic burden. Since it has been stated that helminth parasitic infection of sh affects its productivity, marketability, palatability and death of a good number of shes, it is necessary to detect the parasites and develop their effective control measures.

Limitations
This study is limited only to detection and identi cation of helminth parasites infecting gastrointestinal tract of two cat shes i.e. Clarias gariepinus and Heteropneustes fossilis. Parasites were identi ed only on the basis of morphological characteristics and genetic analysis of the observed parasites couldnot be determined. Also, seasonal variation of helminth parasitic infection in the gastrointestinal tract of cat shes were not observed.