Fish Poisoning Disease In Dogs

The Salmon Poisoning Disease (SPD) has previously been reported in North America only along the western coast of the U.S.A. Dogs and other animals become infected by ingesting trout, salmon, or Pacific giant salamanders. Infected fish are found in the Pacific Ocean from San Francisco to the coast of Alaska, but SPD is more prevalent from northern California to Puget Sound. It is also seen inland along the rivers of fish migration. The causative agent is Neorickettsia helminthoeca. This organism is transmitted to dogs in cysts of the fluke Nanophyetus salmincola salmincola within the tissues of the salmon or trout. Overall, the parasite is relatively harmless. The danger occurs when the parasite itself is infected with a rickettsial organism called Neorickettsia helminthoeca. It's this microorganism that causes salmon poisoning. The presence of fluke eggs in the feces of dogs showing typical signs is very suggestive of a diagnosis of salmon poisoning disease.

Common symptoms of salmon poisoning include:

• vomiting
• lack of appetite
• fever
• diarrhea
• weakness
• swollen lymph nodes 
• dehydration

In SPD, signs appear suddenly, usually 5-7 days after eating infected fish, but may be delayed as long as 33 days, and persist for 7-10 days before culminating in death in up to 90% of untreated animals. Body temperature peaks at 104-107.6°F (40-42°C) 1-2 days later, then gradually declines for 4-8 days and returns to normal. Persistent vomiting usually occurs by day 4 or 5. Diarrhea develops by day 5-7; it often contains blood and may be severe. Dehydration and extreme weight loss occur.

Appropriate treatment, including various sulfonamides are effective, as are chlortetracycline, oxytetracycline, and chloramphenicol. Animals usually succumb because of dehydration, electrolyte and acid-base imbalances, and anemia. Therefore, general supportive therapy to maintain hydration and acid-base balance, while meeting nutritional requirements and controlling diarrhea, is often essential. Owners can prevent salmon poisoning disease by not allowing their dogs to eat raw salmon or trout and similar freshwater fish or snails [1].

Salmon Poisoning Disease In People

Fish poisoning can be divided in two categories. In ciguatera and puffer fish poisoning, the toxin is present in live fish, whereas in scombroid, it is produced only after capture, in the fish flesh, by contaminating bacteria because of improper refrigeration. Most shellfish-associated illness is infectious in nature (bacterial or viral), with the Norwalk virus accounting for most cases of gastroenteritis.

Scombroid poisoning has been associated with the consumption of dark-flesh fish (raw, cooked or canned) with high levels of histidine, which can be converted to histamine from Proteus bacteria in the fish. Fishery products that have been implicated in scombroid poisoning include the tunas skipjack and yellowfin), mahi mahi, bluefish, sardines, mackerel, amberjack, and abalone. The toxin forms in a food when certain bacteria are present and time and temperature permit their growth. Distribution of the toxin within an individual fish fillet or between cans in a case lot can be uneven, with some sections of a product causing illnesses and others not.

Neither cooking, canning, or freezing reduces the toxic effect. Common sensory examination by the consumer cannot ensure the absence or presence of the toxin. Chemical testing is the only reliable test for evaluation of a product. Histamine is produced in the muscle tissue of scombroid fish, such as tuna or mackerel, if it is kept at a temperature which is too high. Since the concentration of histamine is not evenly distributed through the fish's flesh, not everyone who eats the same fish will become ill to the same extent, and some may not even become ill at all.

Scombroid fish poisoning has gradually become a world-wide medical problem and probably is the most common cause of fish poisoning. Many other products also have caused the toxic effects. The primary cheese involved in intoxication has been Swiss cheese.

Signs of Fish Poisoning

Within 40 to 50 minutes of eating contaminated fish people can develop skin rash, itching, diarrhea, vomiting, palpitations, headache, nausea and abdominal cramps, an unusual taste sensation and breathing difficulties. Other symptoms include profuse sweating, and a feeling of intense thirst.

In dogs, tuna fish poisoning usually presents with diarrhea, vomiting and itching.

Diagnosis of Fish Poisoning

The diagnosis of scombroid fish poisoning could be misdiagnosed as food allergy or bacterial food poisoning if physicians are not aware of such poisoning. Toxin analysis of the fish flesh remains the most important step in approaching a confirmed diagnosis.

Treatment of Fish Poisoning

The duration of the illness is usually 3 hours, but may last several days. If the initial symptoms progress to nausea, vomiting, and diarrhea, they may require hospitalization, particularly in the case of elderly or impaired patients. Most cases receiving treatment with antihistamines have rapid and complete recovery.