Ciguatera contracted by French tourists in Mauritius recurs in Senegal

To the Editor:

Ciguatera is food-borne disease caused by ingestion of marine fish contaminated by toxins produced by the dinoflagelate algae Gambierdiscus toxicus that flourishes in coral reefs. Because of this dinoflagelate/reef association, ciguatera occurs mainly in tropical and subtropical regions, i.e., the Indian Ocean, South Pacific, and Caribbean.¹ Although ciguatera is not endemic to Europe, several imported cases have been reported in tourists contaminated during travel in tropical regions.^2–3

Case report: In March 2010, 4 French travelers (2 men and 2 women from 49 to 53 years) were vacationing in Mauritius where they bought a freshly caught “yellow-edged lyretail” (Variola louti) from a local fisherman. A Mauritian woman advised against eating the fish because of the risk of toxicity after a big storm three weeks earlier. Despite this warning, the tourists ate the grilled fish. Within a few hours, symptoms appeared: nausea, vomiting, diarrhea, profuse sweating, bradycardia, and arterial hypotension. One of them was hospitalized for treatment of severe arterial hypotension by perfusion of macromolecular solution. The day after ingesting the contaminated fish, all 4 patients presented paresthesias, thermoalgesia, and intense generalized pruritus. Although other symptoms regressed within 48 h, these neurological manifestations persisted in all 4 patients for 4 to 7 weeks. Upon return to France, the victims contacted the Poison Control Center and were advised not to drink alcohol or eat tropical fish to avoid the risk of recurrence.⁴

In February 2011, two of the four patients (49 year-old-woman and her 52-year-old husband) took another vacation in southern Senegal. After informing hotel personnel that they could not eat fish due to the risk of recurrent symptoms, the couple was told that there was no risk since ciguatera did not occur along the coast of Senegal. On the sixth day of their stay, they gave in to temptation and partook of a noontime meal at which hotel guests were served the grilled flesh of a “giant African threadfin” (Polydactylus quadrifilis). Later the same afternoon, both the man and woman presented vomiting and diarrhea. By evening, both developed peripheral neurological signs including intense pruritus of the face and extremities, cold allodynia, thermoalgesia, dysesthesia of the hands and feet with an impression of walking on cotton, and diffuse paresthesias. In addition to these signs, the man presented invalidating restless leg syndrome. The other hotel guests remained symptom-free. Neurological signs persisted for 8 days in the man and 11 days in the woman.

Recurrence of ciguatera symptoms after consumption of tropical fish has been reported previously.^1,5 A possible explanation is that a small quantity of ciguatoxin can cause the return of symptoms after previous intoxication but cannot induce the illness in persons who have never been exposed.¹ This hypothesis is compatible with observations in our case since only the couple poisoned 11 months earlier presented symptoms. The other guests who ate the same fish did not develop symptoms. Patients with a history of ciguatera poisoning must avoid eating any type of tropical fish for a long period of time. The exact duration of this abstinence period remains unclear. Alcohol is another risk factor for recurrence.^2,3,5 In most cases, alcohol-induced symptoms are less intense and of shorter duration than those occurring after eating tropical fish. After returning from Mauritius, the 49-year-old female patient involved in our case reported a short recurrence of symptoms (duration, 6 h) after drinking a single glass of “rosé” wine.

Regarding geography, ciguatera is well known in Mauritius where cases are reported regularly,⁴ but it is not considered as endemic to the West African coast and have never been reported in Senegal. However, it should be noted that the geographical distribution of ciguatera changes constantly with new locations recorded every year.¹ Although the Caribbean area is classically considered as the only Atlantic risk zone, recent publications suggest the situation may be more complicated: fish contaminated with ciguatoxins have been found in Cameroon⁶ and several cases of ciguatera have been observed after ingestion of local fish species (Seriola rivoliana) in the Canary Islands⁷ that are not so far from the coast of Senegal.