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To the Editor: In the summers of 2003 and 2004, 2 microalgal blooms of potentially toxic dinoflagellates (genus Ostreopsis, usually distributed in tropical waters) occurred along the coasts of Bari, south Italy. Our findings suggest an association between this phenomenon and concomitant symptoms in people exposed to marine aerosols.

Methods
During mid-August 2003 and early September 2004, symptoms of rhinorrhea, cough, wheezing, and fever were observed during periods of 7 and 5 days, respectively, in people exposed to marine aerosols by recreational activities on the beach (swimming or sunbathing) or working activities (swimming attendants involved in entertainment activities in the water and on the beach, assistance to the swimmers, and cleaning the beach and swimming pools). Although a mild macroalgal mucilage was floating on the surface, the water appeared clear. Some people described a metallic taste of the water. Three days after the onset of symptoms during both summers, marine waters to which patients had been exposed were analyzed for temperature, salinity, pH, nitrogen and phosphorus contents, and phytoplankton presence/abundance. Follow-up testing was conducted 3 to 4 days after the last patient was identified. The study was approved by the Institutional Review Board and the patients gave written informed consent.

Results
Twenty-eight persons (9 men, 18 women, and 1 child; mean age, 38.6 y; range, 10-68 y) were identified with symptoms occurring during recreational or working activities on the beach (Table). The most common symptom was copious watery rhinorrhea, but dry or mildly productive cough, fever (temperature to 38°C), and bronchoconstriction with mild dyspnea and wheezes on chest auscultation were also observed. Conjunctivitis was also observed in 3 persons. There was no apparent relationship between symptoms and exposure duration or activities. No patients required hospitalization. Some symptoms ceased within a few hours after discontinuation of exposure, while cough, fever, dyspnea, and wheezing lasted up to 24 hours in some cases.

View this table: [in this window] [in a new window] Table. Characteristics and Symptoms of Patients Exposed to Tropical Algal Blooms

Water temperature, salinity, and pH were in the normal range for that geographical area and seasonal period; nitrogen and phosphorus contents were slightly elevated. The marine water had an unusual proliferation of the tropical microalga Ostreopsis genus (more than 1 million cells/L) during both episodes. On follow-up testing of the marine water samples, the algal bloom had resolved based on a decrease of the species concentration to trace amounts.

Comment
It is likely that the patients’ symptoms were related to the algal proliferation. An Ostreopsis population had bloomed along the investigated coastal areas (more than 1 million cells/L in the water column, despite the tendency for the species to reside close to the seabed, adherent to the bottom macroalgae), probably due to favorable and stable weather conditions for many days (a high atmospheric pressure, a calm sea, and an absence of wind). Although there was no experimental challenge of healthy volunteers exposed to marine aerosol with and without Ostreopsis blooms or isolation of a putative toxin, complaints occurred concurrent with the algal blooms and disappeared when the Ostreopsis population decreased. Most symptoms improved or disappeared very rapidly when the patients left the beach.

Although there is evidence that the respiratory route is involved in some algal poisonings such as with Karenia species in tropical areas,¹ to our knowledge this is the first documentation in the medical literature of an Ostreopsis algal bloom causing respiratory symptoms, particularly noteworthy because it developed in a temperate area. The phenomenon apparently also occurred in the summer of 2001 in the same area² and reports of other Ostreopsis species algal blooms along the Tyrrhenian coast^3-4 suggest similar symptoms in exposed persons.

Algal poisoning can occur through the consumption of contaminated seafood and fish, with varied syndromes that include neurological and gastrointestinal symptoms depending on the microalgal species involved. We did not notice any foodborne disease related to the Ostreopsis bloom, although the analogy with Karenia brevis (neurotoxic shellfish poisoning)¹ makes it likely to occur. Moreover, Ostreopsis is responsible for parrotfish intoxication with rhabdomyolysis found in Japan,⁵ and some cases of ciguatera fish poisoning.^6-7 Possible causes for changes observed in the worldwide geographical distribution of algal blooms include global warming and trade globalization (since some species are transported through the ships’ ballast water).⁸ If these are causal factors and if they continue, blooms of other species of toxic microalgae are likely to occur in the future,⁸ making this a public health issue that will need to be addressed.

Mauro Gallitelli, MD
mauro.gallitelli{at}libero.it
Department of Internal Medicine and Public Medicine
Section of Internal Medicine
University of Bari
Bari, Italy

Nicola Ungaro, BD
Laboratory of Marine Biology
Bari

Luigi Mario Addante, MD; Vito Procacci, MD
Department of Emergency Medicine
Policlinico
Bari

Nicolò Gentiloni Silver, MD
Chair of Emergency Medicine
Catholic University of the Sacred Heart
Rome, Italy

Carlo Sabbà, MD
Chair of Emergency Medicine
University of Bari

1. Kirkpatrick B, Fleming LE, Squicciarini D, et al. Literature review of Florida red tide. Harmful Algae. 2004;3:99-115. FULL TEXT | WEB OF SCIENCE 2. Di Turi L, Lo Caputo S, Marzano MC, et al. Ostropsidiaceae (Dynophyceae) presence along the coastal area of Bari. Biol Mar Medit. 2003;10:675-678. 3. Tognetto L, Bellato S, Moro I, Andreoli C. Occurrence of Ostreopsis ovata (Dynophyceae) in the Tyrrhenian Sea during summer 1994. Botanica Marina. 1995;38:291-295. 4. Sansoni G, Borghini B, Camici G, et al. Fioriture algali marine di Ostreopsis ovata e malesseri da inalazione di aerosoli marini. Genova. 2000;22:25-27. 5. Taniyama S, Arakawa O, Terada M, et al. Ostreopsis sp, a possible origin of palytoxin (PTX) in parrotfish Scarus ovifrons. Toxicon. 2003;42:29-33. PUBMED 6. Onuma Y, Satake M, Ukena T, et al. Identification of putative palytoxin as the cause of clupeotoxism. Toxicon. 1999;37:55-65. PUBMED 7. Yasumoto T, Oshima Y, Murakami Y, et al. Toxicity of benthic dinoflagellates found in a coral reef. Bull Jpn Soc Sci Fish. 1980;46:327-331. 8. Van Dolah FM. Marine algal toxins: origins, health effects, and their increased occurrence. Environ Health Perspect. 2000;108(suppl 1):133-141.

Letters Section Editor: Robert M. Golub, MD, Senior Editor.

JAMA. 2005;293:2599-2600.

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