A REVIEvV OF CIGUATERA, TROPICAL FISH POISONING, WITH A TENTATIVE EXPLANATION OF ITS CAUSE1 JOHN E. RANDALL The Marine Laboratory, University of Miami ABSTRACT The categories of fish poisoning as proposed by Halstead and Lively (1954) are revised. An attempt is made to document what appear to be the established phenomena of ciguatera, an illness of occasional occurrence following the ingestion of various tropical reef and inshore fishes and pos- sibly certain echinoids and gastropods. The toxin appears to be cumulative and the most toxic fishes, generally, are large piscivorous types like barra- cuda, jacks, and groupers. Plankton-feeding fishes have not been implicated in ciguatera. Herbivorous and detritus-feeding fishes and mollusk-feeders may be poisonous. Fishes causing ciguatera are not found universally over large areas, but are localized, often in small sectors. A region once poison- ous may lose its poisonous fishes and vice versa. Previous theories of the cause of ciguatera are discussed, and a new hypothesis is presented. In this, it is assumed that a benthic organism, most likely a blue-green alga, is the source of the toxin. This organism would seem to be one of the first grow- ing in normal ecological succession in tropic seas. The localization of poisonous fishes is explained in terms of availability of new substratum for marine growth. Recommendations are made for further reasearch on ciguatera. INTRODUCTION Certain marine fishes have long been known to cause illness, and on occasions death, when eaten by man. Some cases of fish poisoning have undoubtedly been due to toxins produced by bacterial action on the fish following their capture. However, numerous accounts by scientific observers clearly indicate that toxins may be present in the flesh and viscera of freshly-caught fish. Halstead and Lively (1954: 165-167) have separated poisonings from eating marine fishes into four groups on the basis of sympto- matology: ciguatera; tetraodon poisoning; gymnothorax (moray eel) poisoning; and scombroid (tuna) poisoning. Ciguatera is a usually nonfatal illness of occasional occurrence following the ingestion of various tropical reef and semi-pelagic fishes such as barracuda (Sphy- raenidae), snappers (Lutjanidae), groupers (Serranidae), surgeon- fishes (Acanthuridae) jacks (Carangidae), and possibly certain edible gastropod and echinoid invertebrates. It appears to be the same throughout the tropics, although its origin from a single toxin awaits IContribution No. 212 from The Marine Laboratory, University of Miami. 1958] Randall.' Review of Ciguatera 237 demonstration. Tetraodon poisoning is a severe, sometimes fatal toxemia caused by puffers and porcupine fishes, the ovaries and other internal organs of which are especially toxic. It is distinct and well-documented (for a review, see Yudkin, 1944). Further evidence is needed, however, to recognize gymnothorax and scombroid poison- ings as different from ciguatera or not due to bacterial contamination. It is the belief of the author that gymnothorax poisoning is merely severe ciguatera, and examples of scombroid poisoning seem to be primarily bacterial in origin. Before discussing these dubious cate- gories of fish poisoning further, it is advisable to present the charac- teristics of the ciguatera syndrome. The symptoms of ciguatera appear from about one to ten hours after toxic fish are eaten; those most commonly given for the illness are: weakness or prostration, diarrhea, tingling or numbness of lips and hands and feet, confusion of sensations of heat and cold, nausea, joint and muscular pain, inability to coordinate voluntary muscular movements, difficulty in breathing, burning urination, and itching. Probably the most diagnostic symptoms are the tingling sensations in the hands and feet, frequently described as like "pins and needles". or "electric ~hocks", and the feeling of heat when cold objects are touched or cool liquids are taken into the mouth. Light cases may not exhibit these sensations, however. The author was mildly poisoned in the Tuamotus by eating a small amount of a 500 mm grouper (Plectropomus leopardus) which was cooked immediately after cap- ture. Only weakness, especially of the lower limbs, and diarrhea were evident. If two associates who ate large amounts of the same fish had not acquired typical ciguatera, the slight sickness of the author would not have been attributed to the ingestion of the fish. The gastrointes- tinal distress of ciguatera is usually of short duration, but the neural symptoms may last for many weeks. Various persons in the Society Islands who had suffered from ciguatera informed the author that the tingling sensations of the extremities may be intensified and prolonged by eating reef fishes which are nontoxic to individuals not in the recovery phase of the illness. In reference to ciguatera in the Carib- bean, Brown (1945: 34) wrote, "The effects may last for three months, and as long as the symptoms are present, any fish eaten will make them worse." Halstead <md Lively stated that gymnothorax poisoning develops more rapidly than ciguatera, is more violent, and convulsions and paralyses are prominent. The references from which these authors 238 Bulletin of Marine Science of the Gulf and Caribbean [8(3) concluded that gymnothorax poisoning is unique appear to be only Khlentzos (1950) and Ralls and Halstead (1955). Khlentzos re- ported on poisoning of 57 men on Saipan from eating a single moray eel (Gymnothorax flavimarginata) six feet in length and about one foot in thickness. Twenty minutes after the meal, they experienced tingling and numbness about the lips and tongue. In spite of gastric lavage, severe neurotoxic symptoms developed; 14 patients became comatose, and two died. Ralls and Halstead summarized similar case histories of six men poisoned (one fatally) by the same species of eel in the Marshall Islands. Belotte (1955) presented a case history of a 40 year old American who was hospitalized with ciguatera in Tahiti after eating a large specimen of the snapper Lutjanus monostigmus. This man was in a coma three days, and his illness seemed comparable to those perwns poisoned severely by moray eels. Two men in the Society Islands who became sick, but not as violently as the above individuals, following the ingestion of a moray eel (Gymnothorax sp.) related their symptoms to the author. Both men were very weak, had diarrhea, tingling sensations, and pain, especially in the joints. These symptoms are typical of ciguatera. Halstead (1954) has pointed out that scombroid poisoning is a histamine-type intoxication and not a neurotoxic one like ciguatera. In most instances the cases followed the eating of tuna, bonito, or skipjack which were a day or more old. Phisalix (1922: 607-608) wrote that the species belonging to the genera Scomber, Thunnus, and Cybium are remarkable for the rapidity with which their flesh alters after they are caught; unless they are "thrown from the net into boiling water" they can cause illness from bacterial action which could pass as fish poisoning. Halstead (1954) reported an atypical outbreak of scombroid poisoning at Johnston Island from Euthynnus yaito. The symptoms were identical with those of ciguatera. This small tuna is not exclus!.vely pelagic; it is frequently encountered over reefs and may enter lagoons and bays, Undoubtedly more valid categories of illness from eating marine fishes exist besides ciguatera and tetraodon poisoning. Probable exam- ples are toxic cyclostomes, chimaeras, elasmobranchs (especially the liver of sharks), Tetragonurus cuvieri, certain tropical clupeid fishes, Ruvettus pretiosus, the roe of Scorpaenichthys marmoratus, trunk- fishes (Ostraciidae), and the head of the goatfish Upeneus arge. Some of these other categories will be discussed more fully before dealing with ciguatera in detail. 19581 Randall: Review of Ciguatera 239 Information is not yet available to demonstrate whether or not tropical reef ~harks cause ciguatera. The toxicity of the liver of sharks, at least of pelagic species, may be due to the high vitamin A content (Wheeler in Wheeler and Ommanney, 1953: 47). Jensen (1914, 1948), Bcpje (1939), and Hjortland (1917) have reported some of the arctic sharks to be poisonous (references from Halstead and Lively, 1954). On at least two occasions Risso (1810) endured intense gastric pain, abdominal swelling and a sensation of heat in the throat after eating Tetragonurus cuvieri in the Mediterranean. He attributed the toxicity of this fish (believed to be a deep-water species, but has been taken at the surface) to its feeding on the siphonophore Stephanomia. Fitch (1952) was unable to demonstrate the toxicity of four speci- mens of Tetragonurus from California; stomachs of these fish con- tained unidentified coelenterates and ctenophores. Phis alix (1922: 587) (after Moreau de Jonnes) cites Mola mola as sometimes toxic, as does Mills (1956: 102). It also is known to feed on jellyfishes. The eating of certain tropical clupeid fishes has caused an illness, sometimes said to be seasonal, which is often violent and commonly fatal. Pacific Islands Monthly (Jan. 1956: 142) reported five deaths in Fiji from eating a local herring. Stephenson (1838: 122) gave the symptoms following the ingestion of the thread herring Megalops thrissa (=Opisthonema oglinum) of the Caribbean as nausea, vertigo, extreme heat and itching, violent pain in the stomach, tenesmus, great acceleration of pulse, cold sweats, insensibility, and convulsions. Death may occur within a half hour; survivors may be jaundiced. Strong (1944: 1545) stated that Meletta venenosa (considered a synonym of Harengula punctata by Fowler, 1928: 31) in New Caledonia has caused painful cramps, dyspnoea, cyanosis, cold sweats, dilated pupils and at times death (for a report of the autopsy of a man who died after eating this herring and records of other poisonous clupeoid fishes, ccnsult Phisalix, 1922: 599-601, 612). While discussing c1upeid poisoning with the author, Donald de Sylva made the suggestion that there may be a connection between blooms of the tropical planktonic blue-green alga Skujaella (Trichodesmium in the older literature) and the toxicity of herrings (which are plankton-feeders).