Symptoms of scombroid poisoning develop a few minutes to a few hours after eating the fish, and usually last four to six hours. Victims have one or a number of distressing symptoms: bright red flushing, especially of the upper body, itching and hives, headache, dizziness and rapid pulse, burning or blistering of the mouth, nausea, vomiting and sometimes diarrhea, abdominal cramps, and occasionally wheezing. Some patients later say that the suspect fish had a sharp peppery taste. On rare occasions, life-threatening symptoms such as severe wheezing or very low blood pressure can occur. If these symptoms seem similar to those of an allergic reaction, it is because they are both caused, at least in part, by high histamine levels in the patient’s blood.
That said, if identified correctly, scombroid is easily treated with antihistamines, and the outcome is usually quite good.
For scombroid poisoning to occur, three conditions are necessary. First, the fish’s meat must contain the amino acid histidine, which is found in many dark-fleshed bony fish. Second, microorganisms that produce histidine decarboxylase, an enzyme that breaks down the histidine, must be present. Such bacteria are normal residents in many fish. Third, time and temperature conditions must favor the production and accumulation of the breakdown products (histamine and others) that, when ingested by the unwary consumer, produce the symptoms. Fish kept at room temperature for as little as three to four hours can generate toxic levels of those substances, which accumulate in the flesh. To prove the diagnosis of scombroid poisoning, the fish must be tested in the laboratory for histamine and other vile-sounding chemicals, such as putrescine and cadaverine.
Part of the reason for Dr. Wilson’s swift diagnosis was the fish’s slightly peppery taste, which at the time of the meal she had ascribed to the paprika. Scombroid poisoning also came quickly to mind because she had been a victim of it years before, after eating bluefish in a small, popular restaurant in Cambridge when she was an infectious-diseases trainee at Harvard. She suspected it from the very beginning when Guyer began to feel ill, but when Stubblefield developed the same symptoms, it all but clinched the diagnosis.
If Wilson’s on-the-spot diagnosis proved correct, and if the inn failed to remove the fish from that night’s dinner menu, dozens more cases could occur; the dining room seated a couple of hundred people, and this was peak foliage season, so the place was packed. Therefore, after Stubblefield and Guyer called the hotel doctor, Fineberg telephoned the hotel manager. “I reported our concern about the bluefish and suggested it would be inadvisable to serve it for dinner,” he recalls. The manager replied that he had just called an ambulance for another sick lunch patron, and agreed he would not be serving the fish. “I reassured him that if we were right, nobody would die—although they might feel like they were going to,” says Fineberg.
Shortly thereafter, Wilson and Fineberg also developed facial flushing and headaches. Of the five people at the table who had eaten the bluefish, all except Guyer’s mother had now fallen ill. Once the bluefish was eliminated from the menu, no new cases developed.
Some stories might have ended there. Early Monday morning, however, Wilson phoned the CDC in Atlanta seeking advice about how to further evaluate this aborted epidemic. She was put in touch with Paul Etkind, the state epidemiologist for Massachusetts, who immediately launched a two-pronged investigation. First he set out to track the path of the fish from the distributor to the lunch table. Second, he distributed questionnaires to participants at the medical conference, the responses to which ultimately confirmed the suspicion that the bluefish and no other food was the culprit. Five of the seven diners who ate the bluefish had fallen ill, but no one who had not eaten the fish got sick. The likelihood of this pattern occurring by chance was close to nil.
Because the fish had been served in New Hampshire, Etkind notified his northern counterpart, Joyce Cournoyer, who promptly dispatched a field investigator. Etkind later learned that the fish had been purchased from a large Boston distributor. A team of examiners visited the supplier, tracking each step in how the fish was handled from the fishing vessel to the trucks that delivered it to the restaurants and other buyers. They checked temperatures of storage lockers and assessed the refrigerated trucks. This thorough investigation cleared the supplier of any wrongdoing.
John Seiferth, a district sanitarian for the New Hampshire Department of Public Health, was also pressed into duty rapidly. “I was in North Conway when I received the call late Monday morning detailing the outbreak of presumed scombroid poisoning at the inn. I immediately headed north on Route 302 to inspect the premises. I recalled that I had been there just a few months before on a routine inspection.”
The notes from his earlier visit, which took three hours, showed numerous lapses in sanitary protocol. The concluding paragraph of the report advised the establishment: “Keep cold foods cold and hot foods hot. The large kettle of melted butter must be refrigerated to 45 degrees or less, or heated to 140 degrees or higher. Meats and fish when in preparation are to be put back in the cooler if not being cooked. Each cooler is to have a thermometer.” His report listed other issues as well, and the establishment was given just a 57 percent positive rating.
When Seiferth arrived this time, the investigation was anything but routine; a public-health nurse was already waiting for him. They met on the same porch where Guyer had stood just two days earlier, trying to analyze his symptoms.
When John Seiferth enters an establishment, he is not usually greeted like royalty. “People are not happy to see me; they are on the defensive, but they generally cooperate,” he says. “I remember going into the inn and talking to the chef. I asked him if any of the bluefish from Saturday’s lunch was still available. He told me that it had been thrown out yesterday and then he abruptly left the room.
“The nurse and I looked at each other. We both thought this hasty exit odd,” recalls Seiferth. But they continued their orderly examination of the premises, trying to trace the travels of the bluefish.
What they determined was that the inn had ordered one hundred pounds of bluefish on September 10 from the Boston distributor, and it was delivered on September 12. The fish was then separated into four twenty-five-pound blocks, which were frozen in the inn’s freezer. One of the blocks had been transferred to a walk-in refrigerator on October 1 to thaw for use on the next day. That fish was not served the next day, however, and remained in the walk-in cooler. A second twenty-fivepound block was defrosted in the cooler on October 4. The fish served to Guyer and his party came from those two blocks.
Two staff members, both cooks, said they had sampled the cooked bluefish with no ill effects. They both had an alternative theory about why some of the people got sick on that Saturday. The cooks believed that the problem was due to some residual soap on the silverware; that, they insisted, would explain why some people who ate the bluefish did not get sick.
In the cooler, Seiferth found cod and Boston scrod, Norwegian salmon and pollock, sole and blackfish, but no bluefish. He spent four hours inspecting the kitchen, recorded various temperatures, duly noted several health-code violations that he found, and then left.
On his way out, though, he still felt uneasy about the chef ’s awkward departure, and he thought it odd that none of the fish remained. On a hunch, Seiferth strolled around to the back of the inn, where the trash dumpsters stood. His sixth sense yielded an impressive dividend: a large amount of still-frozen bluefish in one of the dumpsters.
“The fact that the fish was still frozen was crucial for two reasons,” recalls Seiferth. “First, it meant that the chef had not been forthright, because the weather had definitely been too warm for the fish to have stayed frozen overnight. And second, because the fish had not decayed, we would be able to do a meaningful chemical analysis.”
The New Hampshire lab lacked the means for performing the necessary tests, so the fish was transported to the state line, where—as if it were nuclear waste or smuggled drugs—it was transferred to the custody of Massachusetts authorities, who brought it to the s
tate laboratory facilities in Jamaica Plain. There, the bluefish was defrosted under controlled conditions and tested. Normal levels of histamine in fish are close to zero, and the FDA has established a danger, or action, level for histamine at 50 milligrams per 100 grams of fish. In the bluefish from the resort, the Massachusetts authorities found a histamine concentration five times higher than that. Their tests for cadaverine and putrescine were also positive. According to Seiferth, the specific sample that was examined was probably the remainder of the two blocks that had been served on October 5 and then, for some questionable reason, refrozen.
The fact that the frozen fish still contained toxins highlights another important point about scombroid poisoning, most graphically illustrated by the case of the nuns and the tuna.
On August 27, 1979, off the coast of New Jersey, six amateur sports fishermen caught twenty-eight yellowfin tuna, each fish weighing between forty-five and a hundred pounds. This represented an enormous catch—far more tuna than they knew what to do with. It was also far more than they had room for in the onboard icebox. So they placed the excess fish on the deck and periodically hosed it down with seawater. Once onshore, the fishermen divided their catch. One of them took his six fish and put them in his refrigerator at home, but he did not freeze them. His sister was a nun at a nearby Catholic monastery, so he took some of his fish, and some from one of the other fishermen, to the monastery, where he donated them as a gift. He did not refrigerate the fish during the transport.
Thankful for their bounty, these nuns donated one of the fish to a neighboring convent. At this second monastery, that tuna was cut into steaks and frozen for later consumption. About a month later, the nuns from this second monastery enjoyed a meal of broiled tuna. Within a few hours, twenty-three of them abruptly became ill. Their faces turned bright scarlet; they developed headaches, diarrhea, dizziness, nausea, and vomiting. Two of the older women, both in their sixties, had to be hospitalized overnight for monitoring, intravenous fluids, and treatment with antihistamines.
The nuns at the first monastery had eaten the eight tuna the fisherman gave them on five different occasions. Twice, they experienced typical symptoms of scombroid poisoning, but they had attributed this to improper cooking, not to contaminated fish. On one occasion, just before the New Jersey state health inspectors tracked the tuna backward from the second monastery to the first one, the nuns from the first monastery decided to take no chances: this time they boiled the tuna for a full hour to eliminate the cause of their prior illness. Within minutes of eating the boiled tuna, twelve of the twenty women became sick again— facial flushing, nausea, and dizziness. When the investigators tested the bit of fish that was left, they found histamine levels of 370 milligrams per 100 grams of fish. This was even higher than what was found in the New Hampshire outbreak.
The fact that the fish was still contaminated after an hour of boiling is important. Short of divine intervention, once a fish has spoiled, nothing will render it harmless: not freezing, not cooking, neither smoking nor canning. In fact, one large outbreak of scombroid poisoning was traced back to commercially canned tuna. Even vacuum packing after cooking does not prevent the disease if the histamine has already been formed. Salting may help a bit, but some bacteria are salt tolerant and can also lead to the histamine formation. Preservatives that kill bacteria will help reduce the problem, but they do not prevent it entirely.
How does fish need to be handled? Recall that the flesh of many fish contains high levels of the amino acid histidine, but that the fish do not contain free histamine. The enzymes in bacteria that often reside on the surface of and in the gut of the fish facilitate the reaction that generates histamine from histidine. This chemical reaction will occur only when the fish are stored at too high a temperature after being caught. For example, experiments show that one can store a mackerel for nearly three weeks at freezing temperature with little if any histamine formation. However, the same fish will form high levels of histamine in just five days if it is stored at 50 degrees Fahrenheit.
The period of time that the New Jersey tuna was on deck, refrigerated but not frozen, and then transported to the first monastery allowed this chemical reaction to take place. Although there are strict regulations for the commercial fishing fleet, there are no such regulations for sports fishermen, and more than 20 percent of all fish consumed in the United States is caught by recreational fishermen. Many of the fishing vessels used by these fishermen do not have adequate refrigeration capabilities to properly maintain the fish.
Scombroid-type fish have a fourteen-day shelf life at freezing if they are chilled rapidly (reducing their internal temperature to 30 degrees in less than six hours). This shelf-life is halved, however, when it’s stored at 41 degrees. It is important to remember that these time and temperature measurements include the time that fish is on the boat. Fish that is kept whole takes longer to freeze than fish that is cut open and filleted on board. Even gutting the fish without cutting it into filets will help in this equation, because removing the guts reduces the available bacteria that are crucial to the spoiling process. The bottom line is that it is important to rapidly chill the fish to the desired temperature and to maintain them at that temperature. Fish will store indefinitely if promptly frozen.
But why go through the bother of diagnosing scombroid poisoning in the first place? After all, it’s not fatal, and the symptoms eventually subside even without treatment.
The first reason is that some cases are quite severe. The rapid pulse rate can be dangerous for older patients or those with preexisting cardiac conditions. As well, some patients can develop severe bronchial tube constriction, seriously low blood pressure, and, very rarely, heart failure. One British woman collapsed after eating mackerel in a restaurant in Ipswich, England. In the emergency department, she had a blood pressure of 60/40, which is dangerously low. Initially she did not respond to intravenous fluids; only when an alert doctor noted the red discoloration on her neck and chest did he administer intravenous antihistamines. Shortly after the antihistamines, the rash began to dissipate and the low blood pressure quickly resolved.
In another case reported by French physicians, a healthy thirty-sixyear-old woman presented herself to a Parisian emergency department twenty minutes after eating fresh cooked tuna. She had a diffuse red rash, headache, and a very rapid pulse and respiratory rate. Hours later, despite treatment, she worsened and developed severe heart failure. Her blood pressure also dropped to perilously low levels. She recovered, but only after a three-week stay in the intensive care unit, where she had to be placed on a ventilator to support her lungs and an artificial cardiac assist device to support her heart. She nearly died.
The second reason to diagnose scombroid poisoning is a pure public health issue. New cases can be prevented by discarding suspect fish, as was done in the New Hampshire outbreak. And future epidemics can be prevented by correcting the deficient storage practices that led to the outbreak in the first place. Another benefit of correct diagnosis is that affected patients will not be mistakenly labeled as being allergic to fish. Scombroid poisoning is relatively uncommon, compared to allergic reactions, and it is certainly less well known even to some doctors.
Patients who are incorrectly labeled allergic to fish will be uncertain about exactly what kinds of fish they are allergic to. Many of the species of fish that can lead to scombroid poisoning are very common and very nutritious sources of protein and omega-3 fatty acid. Avoiding eating these fish would be completely unnecessary. An incorrect diagnosis of allergy to fish would mean a lifetime of avoiding a very healthy, not to mention tasty, food.
In addition, patients treated in a hospital can avoid costly and potentially risky interventions. If a doctor misinterprets a case of scombroid poisoning as an allergic reaction, for example, one medication that might be given is adrenaline. This medicine may be entirely appropriate for patients with a severe allergic reaction, but it will do nothing to treat scombroid. Elderly patients and those wi
th preexisting heart disease can have serious side effects (including a heart attack) when they are given adrenaline. And last, the duration of symptoms can be lessened by prompt administration of antihistamines.
The last mystery of the New Hampshire outbreak is why Bernard Guyer’s mother never became ill. She had also eaten the bluefish. Several possible explanations exist. First, patients who are taking antihistamines for environmental allergies or as anti-ulcer therapy may have the ill effects of the toxins blocked by these medications. But neither Guyer nor his mother recalls her taking any such pills.
Second, it is known that the levels of histamine in any given contaminated fish are not uniform in all parts of the fish. Levels can vary more than fourfold over a distance of just an inch from one part of the fish to another, the levels being highest in portions taken from nearest the gut. That is probably why only twelve of the twenty nuns got sick too. But the likeliest explanation for Mrs. Guyer’s good fortune is that the fish served for lunch that day came from two defrosted blocks of bluefish, one of which had been thawed for four days, the other for only one day. Much less toxin would have accumulated in that second block. Her portion, lucky for her, most likely came from that batch.
11 The Case of the Overly Hot Honeymoon
Linda Corsetti, a student at Bowdoin College in Brunswick, Maine, was getting ready for a semester abroad. She had so much to do that she put off the required blood tests until the week before she was supposed to leave for Rome. After all, she was in perfect health.
“I didn’t think there’d be any problem,” she recalls. “I went to a lab and had the blood work done. A day later they called me up and said there was a problem, probably an error in recording the results, but to be safe, they asked me to return to have the tests repeated.”
Her blood was retested, but the results were the same: a low white blood cell count with an abnormally high percentage of lymphocytes. The doctor at the school wasn’t sure what the significance was; in fact, nobody was. But to Linda her abnormal blood count meant one thing. “I couldn’t go to Italy with the rest of the group. I was frantic,” Corsetti remembers. It was January 1984.
The Deadly Dinner Party: and Other Medical Detective Stories Page 17