The Philippine Journal of Fisheries 27(2): 119-133 July - December 2020 DOI: 10.31398/tpjf/27.2.2020C0008 FULL PAPER Assessment on the Occurrence of Anisakid and other Endoparasitic Nematodes Infecting Commercially-Important Fishes at Tayabas Bay Maribeth H. Ramos, Trazarah Hanoof E. Argarin, Beatriz A. Olaivar Bureau of Fisheries and Aquatic Resources, Regional Office 4A, Bambang Los Baños, Laguna Philippines ABSTRACT Anisakid nematodes are parasites commonly present in the marine environment. Parasites belonging to the family Anisakidae or the genus Anisakis can cause two different clinical manifestations: gastrointestinal disorders and allergic reactions known as anisakiasis. In this study, we examined 7,126 marine fishes belonging to four different commercially-important fish species;Rastrelliger kanagurta, Sardinella lemuru, Atule mate, and Selar crumenophthalmus for the presence of anisakid and other endoparasitic nematode infection. The fishes caught from Tayabas Bay were bought from three different landing sites from March 2017 to February 2018. The gonads, liver, and stomach of each fish species were incubated for 12-18 hours for rapid isolation and endoparasite evaluation. After the isolation of parasites, anisakid nematodes were fixed in vials with 70% ethanol for morphological analysis under the microscope. Six anisakid groups of genera, including Hysterothylacium, Terranova, Anisakis, Contracaecum, Raphidascaris, and Camallanus, and a non-anisakid group Echinorhynchus were identified. The results showed that the prevalence of anisakid infection in all species was 24.18 %, with a mean intensity of infection of 1.91. Rastrelliger kanagurta (Dalahican), Atule mate, and Selar crumenophthalmus were the most infected with 50.90%, 38.98%, and 30.52% prevalence rate, respectively, followed by Rastrelliger kanagurta (San Francisco) (24.18%) and Sardinella lemuru (7.46%). The collected data suggest that commercially-important fish caught in the Tayabas Bay waters are susceptible to parasitization by larvae of the genus Camallanus followed by Hysterothylacium and Terranova in their visceral organs. The prevalence of anisakid infection was almost similar between female (45.3 %) and male (47.21 %) fishes with a mean intensity of 1.95 & 1.96, respectively. Also, larger fishes were heavily infected with anisakid larvae than small fishes. Thus, the intensity and prevalence of the fish parasite can be used as a biological tag for benchmarking and stock assessment purposes. *Corresponding Author: [email protected] Keywords: Endoparasites, Anisakid nematodes, Received: January 28, 2020 prevalence, intensity, biological tag, Tayabas Bay Accepted: November 19, 2020 1. INTRODUCTION fishing industries and are potential human health hazards, both as causative agents of anisakiasis arine fish are known to be infected by many and potential food-borne allergens (Daschner and different parasites. Parasitic nematodes Pascual 2005). Anisakids with economic and public constitute one of the earliest known groups health importance are Anisakis, Pseudoterranova, Mof helminths in fishes (Molnár et al. 2006). Anisakid Contracaecum, genera of family Anisakidae (EFSA nematodes (Nematoda: Anisakidae) are common 2010) while Hysterothylacium, the genus of family parasites of marine fish used as definitive, intermediate, Raphidascarididae, is commonly considered not or paratenic hosts (Cruz et al. 2007). Some nematodes zoonotic (Iglesias et al. 2002), except for sporadic cases are endoparasites in marine mammals, sea birds, (González-Amores et al. 2015; Yagi et al. 1996). These and fish, with four major anisakids known to infect are commonly found in the viscera and musculature of marine fish (Dadar et al. 2016). Larvae of anisakid many teleost fish species (Costa et al. 2003). nematodes are a significant problem for commercial 119 | The Philippine Journal of Fisheries The Philippine Journal of Fisheries 27(2): 119-133 In Europe, anisakid nematodes are the most important marine fishes; to assess the prevalence, relevant group of parasites in terms of consumer abundance, and intensity of endoparasitic nematodes health risk and product quality, with Anisakis and infecting marine fishes at Tayabas Bay; and to correlate Pseudoterranova as the genera of greatest concern the sex, length, weight, and gonadal stage of the because several species are considered a human marine fishes with the number of parasitic infections health hazard (Mattiucci et al. 2017). Recent data on at Tayabas Bay. the possible use of anisakid nematodes have been presented as biological indicators of a) the definition 2. MATERIALS AND METHODS of fish stocks within a multidisciplinary approach, b) integrity and stability of trophic webs, and c) habitat 2.1 Study area disturbance (Mattiucci and Nascetti 2008). They are also playing an essential role in marine ecosystems Tayabas Bay is one of the major fishing by affecting their hosts’ population dynamics (Rohde grounds in the CALABARZON Region. It has the 1993). The information on marine fishes’ food habits, second largest area in the region by 2,213 km2 next such as the predator-prey relationship, is useful to to Lamon Bay with 2,838 km2. The bay covers 16 assess the role of marine fishes in the ecosystem municipalities and one city in three provinces: Quezon, (Bachok et al. 2004). Marinduque, and Batangas. In Quezon Province, With increasing interest in fish production, Lucena City is the only city along Tayabas Bay; the parasite infestations are becoming a threat to fish 11 municipalities are Agdangan, Catanauan, General health management. Thus, limited studies on the Luna, Macalelon, Mulanay, Padre Burgos, Pagbilao, infection of endoparasitic nematodes in Philippine Pitogo, San Francisco, Sariaya, and Unisan. It consists waters, especially in Tayabas Bay, encouraged the of 121 coastal barangays, which include the study area, authors to perform parasitological studies. namely Barangay Matandang Sabang Kanluran of The general objective of this study is to Catanauan (13°58’65.89” N latitude & 122°27’11.33” generate baseline data on the anisakid and camallanid E longitude), Silongin and Inabuan, Poblacion and worms found in commercially-important species Cawayan I of San Francisco (13°34’33.21” N latitude & as biological indicators in the formulation of 122°51’82.19” E longitude), and Barangay Dalahican policies for the sustainable management of Tayabas (13°90’33.23” N latitude & 121°62’26.19” E longitude) Bay. Specifically, the authors aimed to identify the of Lucena, as shown in Figure 1. occurrence of parasites infecting the commercially- Figure 1. Map of Tayabas Bay showing commercially-important fishes sampling sites where sampling for this study was undertaken. 120 | The Philippine Journal of Fisheries Assessment on the Occurrence of Anisakid and other Endoparasitic Nematodes Infecting Commercially-Important Fishes at Tayabas Bay 2.2 Sample Collection and Preparation of Fish Sample We collected samples of Bali sardine (Sardinella lemuru), Yellowtail scad (Atule mate), Bigeye scad (Selar crumenopthalmus), and Indian mackerel (Rastrelliger kanagurta) (Figure 2) in three landing sites of Tayabas Bay, specifically at Dalahican, Catanauan, and San Francisco, Quezon Province (Figure 1). The selection of fish samples depends on the abundant catch of the most operated fishing gears in the respective sampling area that are available whole-year-round. Sampling size varied among fish species and sampling localities. In general, smaller sized species like sardines were sampled and examined in large quantities compared to medium-sized species such as scad and mackerel (Table 1). Figure 2. Commercially-important fishes of Tayabas Bay. The Philippine Journal of Fisheries | 121 The Philippine Journal of Fisheries 27(2):119-133 of Fisheries Journal Philippine The 122 | The Philippine Journal of Fisheries Journal Philippine 122 |The Table 1. Summary of the statistics of fishes: number of fish examined (N), number of infected fish (NI), sex ratio, mean length (cm) and mean weight (g), number of parasites (NP), prevalence (P%), mean abundance (MA) & mean intensity (MI) (standard error of the mean), median and infection rate (IR%) of larval anisakid, and camallanid nematodes parasites from the examined fish species in Tayabas Bay; D (Dalahican), SF (San Francisco). Fish species N NI Sex Ratio Mean length Mean weight NP P (%) MA MI ± SEM Median IR (%) (M/F) (cm) (g) Atule mate 744 290 1.52 20.43±0.21 107.25±50.48 711 38.98 0.96 2.53 ± 0.09 2 95.56 Rastrelliger kanagurta (D) 719 366 0.76 23.26±0.11 143.99±41.84 946 50.90 1.32 2.56 ± 0.08 2 131.57 Rastrelligerkanagurta (SF) 827 200 1.22 24.13±0.16 156.79±49.26 302 24.18 0.37 1.77 ± 0.09 1 36.52 Sardinella lemuru 2,641 197 0.95 13.62±0.14 23.15±11.96 224 7.46 0.08 1.22 ± 0.08 1 8.48 Selar crumenopthalmus 2,195 670 1.04 20.95±0.08 115.93±38.31 884 30.52 0.40 1.52 ± 0.05 1 40.27 OVERALL 7,126 1,723 1.04 20.89±3.78 114.62±54.95 3,067 24.18 0.43 1.91 ± 1.88 1 43.04 The fish were randomly collected twice or thrice a month from removed from plastic bags and placed immediately in a cylindrical tube or each landing center to reach the ideal target of samples of 2-5 kg per species. beaker and washed thrice with Physiological Saline Solution (PSS). These were Sampling was done for 12 months, starting March 2017 to February 2018. then transferred in a petri dish and thoroughly examined for the collection Commercially-important fishes in the area were bought from three landing of nematodes using an improvised needle. After the isolation of parasites, sites and were preserved and transported to the laboratory for examination anisakid nematodes were fixed in 70% ethanol for morphological analysis using plastic bags containing water with broken pieces of ice. Each fish sample under the microscope. Nematoda and Acanthocephala were dehydrated was weighed to the nearest gram (g) and total length (cm) measured from in a graded ethanol series and transferred to 100% glycerine for further the snout's tip to the longest caudal fin.