Red Tides and Paralytic Shellfish Poisoning in the Philippines
Total Page：16
File Type：pdf, Size：1020Kb
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Aquatic Commons Red Tides and Paralytic Shellfish Poisoning in the Philippines Ruben A. Estudillo and Cielito L. Gonzales Oceanography Section, Fisheries Research Division, Bureau o f Fisheries and Aquatic Resources, Quezon City, Metro-Manila, Philippines Introduction New Guinea (1972 until early 1976), Brunei and Sabah (March-May 1976) and the Philippines Toxic marine dinoflagellate blooms have been (mid-1983). recognized for many years to have a significant The major species involved in the tropical Indo- impact on the utilization of shellfish resources and Pacific red tides was the armoured, bioluminescent human health because of the problem of paralytic dinoflagellate Pyrodinium bahamense Plate 1906, shellfish poisoning (PSP), which occurs in many which was recently reclassified as Pyrodinium areas of the world and seems to be intensifying and bahamense var. compressa Böhm 1931 (Steidinger spreading (Prakash et al. 1971; Taylor and Seliger et al. 1980), a species that is closely related to 1979). Less than 20 dinoflagellate species are known Protogonyaulax (= G onyaulax spp.) (Fig. 1), and or thought to produce toxins (Steidinger 1979). was unreported in the region before 1971 (Maclean Many filter-feeding shellfish, such as clams, 1979). The organism was first described from mussels, and scallops, feed on several of these red Waterloo Lake, a small, shallow, saline lagoon in tide forming toxic dinoflagellates and accumulate Nassau, Bahamas, in 1906 (Beales 1976) and its the toxins in their tissues without themselves being previous known distribution was restricted to the affected (Prakash et al. 1971; Twarog 1974; tropical and subtropical waters of the Caribbean Sea Hashimoto 1979). As a consequence, it may become (particularly Jamaica and Puerto Rico), eastern a serious problem when the affected shellfish are Pacific Ocean, Red Sea, Persian Gulf, and North eaten by warm-blooded animals that are Atlantic Ocean (Wall and Dale 1969) where it was particularly sensitive to the toxin. In extreme cases, reported to be nontoxic (Beales 1976). It has now, several species of clams and mussels may prove fatal however, been found to be responsible for fatal if eaten by man. To date, research efforts to develop paralytic shellfish poisonings in Papua New Guinea an antidote for the toxins have been relatively (Worth et al. 1975), Brunei and Sabah (Beales unsuccessful (Yentsch and Incza 1980) and the only 1976), and the Philippines (Estudillo 1984). effective control measure is the closure of the Harmful dinoflagellate blooms of Pyrodinium affected areas to shellfish gathering. bahamense var. com pressa and the paralytic Paralytic shellfish poisoning has long been shellfish poisoning it causes were experienced for known as a serious problem in four regions of the the first time in Philippine waters when they world, namely Europe, North America, the Pacific occurred along the coast of Eastern Visayas coast, and Asia (Twarog 1974). There are medical northwestward to the coast of Masbate and records of over 1650 cases of this food poisoning Sorsogon during the period from late June to early worldwide, which have resulted in at least 300 September 1983 (Fig. 2). In the latter part of fatalities (Dale and Yentsch 1978). Jay (1970) September, cases of paralytic shellfish poisoning asserted that paralytic shellfish poisoning in man involving one fatality were reported in Western has a mortality rate close to 10% and as much as Visayas. 22% in some areas. Severely affected by the red tide were the Most recently, red-tide outbreaks were reported mariculture project farms in Maqueda Bay and in tropical Indo-Pacific countries such as Papua Villareal Bay (western Samar), where green bay 52 Fig. 1. Pyrodinium bahamense var. compressa Böhm 1931 taken by scanning electron microscope (through the courtesy o f the Research Institute for Tropical Medicine and the U. P. College o f Engineering). 53 Fig. 2. Map showing the red tide survey area. Shadowed circles indicate areas where paralytic shellfish poisoning cases have been reported. Areas affected by the Pyrodinium blooms (red tide) are stippled. 54 mussels (locally called “tahong”) or Perna viridis than 35 m. The samples collected were preserved in Linne (= Mytilus smaragdinus) are being cultured. 10% formalin solution. Commercial harvest, sales, and consumption of Plankton samples were examined for toxic mussels and other shellfish were banned for almost dinoflagellates using a Nikon bacteriological 8 months, which resulted in great economic loss. microscope (model SC). Counting was carried out Paralytic shellfish poisoning reports have also on a 1 mL aliquot part placed into a shown that many people had been taken ill: a total Sedgwick-Rafter counting chamber. Numerical of 278 cases were reported involving 21 deaths, most estimates were made based on the diameter of the of them were due to the ingestion of the green mouth of the net, sampling depth, and volume of mussels from Maqueda Bay and Villareal Bay. the plankton samples. Counts were then converted The extensive toxic dinoflagellate blooms in to number of Pyrodinium cells per litre of water Eastern Visayas and along the nearby coast filtered by the net. provided an opportunity for the Bureau of Fisheries Regular plankton samplings (both vertical haul and Aquatic Resources (BFAR) to monitor and and surface tow) in Maqueda Bay and Villareal Bay investigate the blooms. and approaches were conducted with the same This paper deals with the type of monitoring and plankton net, but only for qualitative analysis. investigative work conducted from 22 July 1983 Trawling operations, using a German-type net until the blooms of the toxic dinoflagellate with dragging time ranging from 15 min to less than completely disappeared from the waters of the 2 hours, were made in Carigara Bay, eastern and affected areas and from the gills and viscera of the southern parts of Samar Sea, and its adjoining mussels. The results of the toxicological analysis waters for the purpose of collecting samples of fish carried out on the mussels are also presented in this and invertebrates for gut content analysis to paper. determine the extent of contamination and identify potentially toxic seafoods. Fish and invertebrate collections in the shallow Methodology waters of Samar Sea, Maqueda Bay, and Villareal Bay, on the other hand, were made by taking Two aerial observations were carried out to samples from the catch of subsistence fishermen assess the location, configuration, and possible operating in the area. Samples of fish and other spreading of the red tides. These were carried out marine products were also obtained from the using light aircraft from the Eastern Command of markets and fish-landing centres. the Philippine Air Force in Tacloban City. In Counting and recording of Pyrodinium cells in addition to these, sighting reports from commercial the gut of fish and invertebrates were carried out by Philippine Airline flights were also recorded. removing the gut/ viscera from the fish/ invertebrate Eighteen oceanographic stations were and dissecting it. The entire gut contents were then established in Carigara Bay and the eastern and placed on a glass slide and spread out. The number southern parts of Samar Sea where water samples of Pyrodinium cells were then counted under a were collected at standard depth intervals of 2 m in microscope and qualified into various categories. the upper 10-m layer and every 5 m thereafter using Bioassay tests were carried out on mussel Nansen reversing water bottles provided with samples collected monthly (or sometimes twice a protected and unprotected reserving thermometers. month) from a number of mussel farms along the Temperature readings were recorded at each depth coastal area of Maqueda Bay and Villareal Bay. and water samples were collected and analyzed for Fresh mussel samples were sent regularly to the salinity and dissolved oxygen employing the Bureau of Research and Laboratories (BRL) of the Knudsen-Mohr and modified Winkler methods Ministry of Health in Alabang, Muntinlupa, respectively. Metro-Manila, for “mouse bioassay” testing. The Transparency readings were taken using the calculation of the toxin level in micrograms per 100 standard Secchi disc. Sea surface and grams of shellfish meat, as suggested in the standard meteorological observations were also recorded. assay method of the Association of Official Vertical plankton hauls were made using a Analytical Chemists (Horwitz 1975), was not closing plankton net measuring 30 cm in mouth possible in the present study due to a lack of diameter, 110 cm in total length, and with a 90 µ m paralytic shellfish poison standard solution. mesh size. Five sets of plankton data, according to Determination of the presence and strength of the sampling depths, were obtained, i.e., 5-0, 15-10, 25- toxin in the tissue of mussels was, therefore, 20, 35-30, and 35-0 m, or from near the bottom to attempted (using the Bureau of Research and the surface if the depth of the station is shallower Laboratories “standard” procedure) in terms of 55 percentage mice mortality and death time. For each discharge from rivers into the sea was observed monthly test, about 200 mice were injected during this period. As a result, the red tide spread intraperitoneally with shellfish extract and observed out and was seen from commercial flights as together with the control mice, which were injected orange-red patches along the 70-km stretch of with acidified water. western Samar coastline from Villareal to Gandara (Fig. 4). The peak of the visible red tides occurred in the Results and Discussion latter part of July (Fig. 5). The fading of the visible red tides started in early August, which could be due Chronological Observations of the Occurrence to the continuous sunny days with only occasional of Red Tides rain showers, calm sea surface conditions, minimum The first recorded case of paralytic shellfish wind force ( 1 m/sec), and variable winds (W, NW, poisoning involved two deaths and occurred in the SW, SSW) in the area.