Research of parasites with zoonotic potential for humans in skipjack tuna ( Katsuwonus pelamis )

The skipjack tuna (Katsuwonus pelamis) is commonly found in the tropical waters of the oceans. It is a fishing resource of high economic value and available for national and international markets. Therefore, it is important to know the fish parasites for a correct sanitary inspection, as the pathogenesis in humans can occur through spoliative, toxic or mechanical action. This study aimed to identify the zoonotic parasitic fauna that infects the beautiful-striped using morphological methods. A total of 06 samples were analyzed. The fish were necropsied for parasitological evaluation of the musculature and internal organs. The samples were visually inspected and the structures with morphology combining with parasitic shapes were analyzed both in stereoscopic and microscope. The parasites found were fixed in 70% alcohol for later identification. All samples showed the presence of zoonotic parasites for humans. Two genera of zoonotic parasites have been found for humans that have beautiful tuna as their hosts, namely Anisakis sp. (Nematoda) and Trypanorhyncha (Eucestoda). A 100% of the infections occurred in the muscles and 66.6% in the liver. The results reinforced the importance of inspection by responsible organisms on the importance of evisceration as quickly as possible to avoid migration of larvae to the muscle. Key-words: fish, anisakid, Trypanorhyncha.

Research of parasites with zoonotic potential for humans in skipjack tuna (Katsuwonus pelamis) Pesquisa  The skipjack tuna (Katsuwonus pelamis) is commonly found in the tropical waters of the oceans. It is a fishing resource of high economic value and available for national and international markets. Therefore, it is important to know the fish parasites for a correct sanitary inspection, as the pathogenesis in humans can occur through spoliative, toxic or mechanical action. This study aimed to identify the zoonotic parasitic fauna that infects the beautiful-striped using morphological methods. A total of 06 samples were analyzed. The fish were necropsied for parasitological evaluation of the musculature and internal organs. The samples were visually inspected and the structures with morphology combining with parasitic shapes were analyzed both in stereoscopic and microscope. The parasites found were fixed in 70% alcohol for later identification. All samples showed the presence of zoonotic parasites for humans. Two genera of zoonotic parasites have been found for humans that have beautiful tuna as their hosts, namely Anisakis sp. (Nematoda) and Trypanorhyncha (Eucestoda). A 100% of the infections occurred in the muscles and 66.6% in the liver. The results reinforced the importance of inspection by responsible organisms on the importance of evisceration as quickly as possible to avoid migration of larvae to the muscle. Key-words: fish, anisakid, Trypanorhyncha.

INTRODUCTION
There is an increase in the number of people who prefer to consume fish meat as a healthy food alternative, in relation to other meats. The low fat content of many fish species, the excellent nutritional value due to their proteins, vitamins and the effects of polyunsaturated fatty acids found in the species are important aspects for those who are concerned about health, in particular in developed countries where mortality from cardiovascular disease is high [1][2][3][4].
The presence of parasites in fish is a concern for sanitary surveillance with zoonotic potential, causing consumer rejection and the animals must be eliminated by sanitary surveillance that constitutes consequent economic losses.
In this regard, the regulation of the industrial and sanitary inspection of animal products, RIISPOA defines as unfit for consumption fish that have muscle infestation by parasites that may or may not harm the consumer's health [5]. Acute gastric infection is one of the infection risks caused by the consumption of live parasite larvae [6][7][8]. Zoonoses occur when infected raw marine products are consumed by humans as accidental hosts [4,9].
The sckipjack tuna (Katsuwonus pelamis) is a large pelagic fish commonly found in tropical ocean waters. [10,11]. It is a fishery resource of high economic value and available for national and international markets. All carnivorous fish with pelagic habits are likely to be infected by anisakid nematodes. As this fish is part of the human diet, information about possible infections is crucial. Studies to identify the zoonotic parasites found must be carried out in order to identify and understand the form of action in the human body.
The results are beneficial for basic information from epidemiological studies, food safety and biological markers. In relation to food safety, identification is a basis for the study of potential pathogenic hazards and risks that can lead to a negative impact on human health. Therefore, it is important to know the fish parasites for a correct sanitary inspection, as the pathogenesis in humans can occur by spoilage, toxic or mechanical action [12]. This study aimed to identify the zoonotic parasitic fauna that infects the striped bonito (Katsuwonus pelamis) using morphological methods.

Sample collection
Specimens of skipjack tuna (Katsuwonus pelamis) were obtained through donation by the company Gomes da Costa LTDA, Itajaí, Santa Catarina, Southern Brazil. A total of six fish were packed in isothermal boxes and transported to the AQUOS-Aquatic Organisms Health Laboratory, at the Federal University of Santa Catarina (UFSC), where they were kept refrigerated until the necropsy.

Analysis of samples
In the laboratory, the fish were necropsied for parasitological evaluation of the musculature and internal organs. For this, the eyes, gills, gastrointestinal tract and viscera were removed and examined for collection of endoparasites.
Evisceration was performed from a ventral longitudinal section, from the anus to the cephalic region. To investigate the parasitism in the meat, two longitudinal cuts were made, on both sides, starting from the insertion of the tail towards the head until the level of the operculum, obtaining two fillets per fish.
The samples were visually inspected and structures with morphology combining with parasitic forms were analysed both in stereoscopic and under a microscope. The parasites found were fixed in 70% alcohol for later identification. The methods used for the collection and parasites identification followed Eiras et al. (2006) [13]. The morphological identification at the genus level of the parasites found was according to Campbell and Beveridge (1994) [14] for Trypanorhyncha and Castellanos et al. (2017) [15] for Anisakid nematodes. Morphological identification of the parasites was made using an Axio Imager A.2 differential interference contrast microscope (DIC, Zeiss, Gottingen, Germany).

RESULTS AND DISCUSSION
A total of six samples were analyzed, all of which showed the presence of zoonotic parasites for humans. Nematode parasites identified as the genus Anisakis sp. and cestodes Trypanorhyncha were observed being the last the most prevalent group. The results obtained were described in Table 1.  The results showed that 100% of the infections occurred in the muscle and 66.6% in the viscera (liver) of the analysed fish (Figures 1, 2 and 3). This highlights the importance of evisceration being carried out as quickly as possible, thus preventing the parasites from migrating to the fish's muscle tissue [16,17]. The muscle was the most affected organ, with a total of 123 parasites in 6 samples.   As for the parasites found, Anisakis sp. was the most reported in the literature when compared with Trypanorhyncha. Studies on allergic manifestations to fish parasite antigens are quite frequent, especially involving anisakids. However, only a few investigations have been carried out on this potential in other parasites, such as cestodes Trypanorhyncha.
The Trypanorhynca is the most common cestode parasitizing sharks and stingrays (definitive hosts in its adult form), as well as numerous invertebrates and teleost fish that can act as intermediate hosts (larvae forms -metacestoids), being it of worldwide occurrence [14,18]. Accidental human infection by Trypanorhyncha larvae is rare. However studies that have pointed out the allergenic potential of some species of the group [19][20][21][22][23][24]. Each year, new genera and species of Trypanorhyncha are described. Until 2012, 290 species were registered [23]. The presence of Trypanorhyncha larvae in fish, mainly in the muscular tissue (with greater commercial value), has for many years led to economic losses due to the health aspect. Sattari et al. (2014) [25] reported the presence of Trypanorhyncha metacestoids in sckipjack tuna obtained in the coast of Oman, in the Arabian Peninsula. Amato et al. (1990) [26] in a study identified the presence of Tentacularia coryphaenae in sckipjack tuna.
Few articles reported human infections by fish-borne nematodes [43,[46][47][48][49][50][51]. However, the greater the number of fish species infected, especially in the case of economically important species, the greater the risk to humans of ingesting fish-infected nematodes.

CONCLUSION
Two genera of zoonotic parasites were found for human and skipjack tuna showed to be the host for Anisakis sp. and Trypanorhyncha. The first, in the viscera, highlighted the importance of Larval dente immediate evisceration soon after capture, while the second was found in the muscle of the fish examined, reinforcing the importance of inspection by government organisms prior to processing.