If you like to eat tuna you may be worried about parasites. The truth is, there are several parasites that can be found in fish. These parasites can be harmful, including Salmonella, Anisakis and Gnathostoma. Fortunately, you can protect yourself from these parasites by knowing what to look for and how to avoid them.
Listeria
Using raw yellowfin tuna as a source of raw material, the present study aimed to investigate the behavior of Salmonella and Listeria monocytogenes in fish. The aim of this study is to assess the ability of these pathogens to survive freezing conditions and the effects of inoculation level on their populations.
Samples of raw yellowfin tuna were obtained locally. Blocks were weighed at 450 g per block. Each block was inoculated with culture suspensions. These were then transferred to sterile stomacher bags and stored in refrigerator for 14 days.
Salmonella and Listeria monocytogenes were detected by using primers. They were present in 14.3% of the raw material. One-Way ANOVA was used to evaluate the differences between each treatment.
During frozen storage, the levels of Salmonella and L. monocytogenes were reduced significantly. The decrease in Salmonella was observed in all three strains. After 12 weeks, the Salmonella population decreased from 2.56 log CFU/g to 1.98 log CFU/g, and the L. monocytogenes population also decreased from 102.54 log CFU/g to 104.04 log CFU/g.
Inoculated tuna samples were stored for up to twelve weeks at 5-7 degC and -18 degC. After storing at 5-7 degC, the population of Salmonella reduced by two to one log. At -18 degC, the population of Salmonella and L. monocytogenes increased, respectively.
Listeria monocytogenes populations were reduced by one to three log after fourteen days of frozen storage. Inoculated tuna samples with a high level of inoculation had a log reduction.
Gnathostoma
Gnathostoma is a parasite that affects the human body. It can cause vision loss, blindness, and nerve damage. The disease is caused by eating infected raw or undercooked fish. Symptoms can include eyelid edema, migratory erythema, and pruritic lesions.
People living in endemic areas should cook their fish. However, if they are not able to do so, they should avoid eating raw freshwater fish.
Infection with Gnathostoma is rare. Some of the countries that are known to be endemic to the disease include Thailand, Japan, and Indonesia. Among the other countries, Myanmar, the Lao People’s Democratic Republic (Lao PDR), and Vietnam are also endemic.
People who become infected with gnathostomiasis have a high mortality rate. Initially, they present with cutaneous lesions. Later, the worms crawl along the spinal nerves and migrate to the central nervous system. These larvae can also migrate into the gastrointestinal tract and into the eyes, ears, and lungs.
The disease is mainly caused by a trematode called the Gnathostoma spinigerum. This parasite is a zoonotic nematode that primarily affects humans. It can affect the skin, the eye, the gastrointestinal tract, and the trunk.
There are two species of gnathostoma that can infect humans. These are the Gnathostoma binucleatum and the Gnathostoma spinigerum. Both are found in Asia and are commonly referred to as chokofishi or Shanghai rheumatism.
A diagnosis of gnathostomiasis can be made based on a clinical picture, serologic tests, and histological examination results. In some cases, patients develop a second form of gnathostomiasis, known as ocular gnathostomiasis.
Anisakis
Anisakis parasites are parasites that are commonly found in seawater and can be transmitted to humans by the consumption of raw or undercooked fish. The symptoms of Anisakis infection include vomiting, diarrhea, abdominal pain, and nausea.
Anisakis species are known to use a variety of intermediate hosts. For example, Anisakis simplex type 1 has been detected in squid in Spain and krill in Antarctica.
Symptoms of Anisakis infection are caused by penetration of the infective larvae into the intestine. Depending on the stage of the larvae, they may enter the intestinal lining or remain in the intestine.
The life cycle of the Anisakis simplex parasite is complex. It has four stages. First, the larvae hatch from eggs in the host. They then encyst in the visceral organs of the host. When the larvae encyst, they release eggs through the host’s faeces. After a few weeks, the larvae migrate to the stomach, where they develop into adult worms.
Anisakids are a family of worm-like parasites. In humans, they are responsible for severe pathologies. Some of the species in this family are known to cause allergic reactions.
Although Anisakis is not a common disease, its presence in the food chain is becoming more and more apparent. It is reported that Anisakis infects about 56 million people worldwide each year. Most cases have been in Japan.
Despite the increasing number of cases, anisakiasis is not common in Europe. However, it is increasingly occurring in Western countries.
Salmonella
Salmonella is one of the most common food-borne pathogens. It is responsible for 23,000 hospitalizations in the United States every year, and 1.2 million illnesses. Pregnant women, infants, and people with compromised immune systems are at high risk of illness from this pathogen.
In the past, there have been outbreaks of Salmonella in raw or undercooked fish, and in other forms of seafood. This type of food poisoning can cause diarrhea and abdominal pain, as well as vomiting. These symptoms can occur up to 72 hours after infection.
Salmonella is present in both raw and frozen seafood. However, the ability of these organisms to survive refrigerated storage has not been well documented. Therefore, refrigeration is the preferred method of food safety.
Although the FDA has not recommended freezing or cooking seafood to kill pathological bacteria, the FDA has mandated that all imported and domestic seafood be properly stored at a temperature of 5-7 degC to destroy any potential pathogens. Historically, freezing has been used in the seafood industry to kill parasites.
There have been few reports on the prevalence of Salmonella in tuna. Currently, there are no reliable estimates of the prevalence of Salmonella in raw yellowfin tuna. The aim of this study is to investigate the behavior of Salmonella in these foods.
Samples were analyzed for Salmonella using two strains: ATCC 6962 and SFL 0319. The two Salmonella strains were inoculated onto the surface of cut tuna cubes. Once inoculated, samples were transferred to sterile stomacher bags, sealed, and stored in a refrigerator for 14 days.
False story about tongue-eating parasites
Have you ever wondered what it is like to have a fish with a tongue-eating parasite? You might be surprised to learn that you’ve got one if you’re eating canned tuna. While it is not the same as having a real one, you may find that the resulting depletion of your dietary protein and vitamins may lead to some health problems.
Cymothoa exigua, also known as the tongue-eating louse, is a parasitic isopod that lives in many varieties of fish. It’s the only known organism to replace an entire organ of a host species. Typically, it infects the red snapper, but it’s found in a number of other fishes, too.
A recent report about tongue-eating parasites in tuna caught my eye. It was actually a wingless parasitic insect that climbed to the base of the fish’s tongue, sucks blood from its mate, and then uses the resulting mucus to nourish itself. This is a pretty neat thing to see, but I didn’t know it was possible.
The actual process is actually quite complex and it involves a lot more than one organism. Although the fish eats a small bit of the parasite’s mucus, it still has to endure the cycle of death and rebirth. Basically, it’s like a functional prosthetic that acts as a pseudo-tongue.
What you might not know is that this is a highly specialized fish that only lives in coastal waters, and that it’s even more likely to happen in saltwater environments.
Cooked vs raw tuna
Whether you are cooking or eating raw tuna, it is important to understand the risk of parasites. While these parasites are not harmful, they are often the cause of digestive issues, vomiting, and bloody stools. There are several measures to control the risk of parasites in your food.
The most effective method for killing fish parasites is to freeze them. Raw fish, including tuna, should be frozen at -20degC for seven days. This will kill most of the parasites, but not all.
In addition to freezing, heat treatments are another means of killing parasites. However, the FDA does not recommend these techniques.
When it comes to the risk of parasites in fish, the FDA states that “freezing at -4 (-20) or below for seven days” is the most effective. That said, most restaurants follow this recommendation.
It is best to avoid eating freshwater fish, especially if you are pregnant or have a compromised immune system. Freshwater fish can carry parasites such as tapeworms.
Some ocean fish also carry parasites, but the risk is lower. Tuna is resistant to parasites, so it is a safer fish to eat raw than other fish.
If you plan on preparing sushi, be sure to find a reputable fishmonger who is knowledgeable about the various types of seafood and their risks. You can also ask questions about the process of making sushi to ensure you are purchasing the safest fish.
