Don’t eat crayfish washed out by floods, be careful of rhabdomyolysis!

Haff disease, also known as lagoon disease, first appeared in the Baltic Sea region of Germany and is often caused by aquatic animals such as fish, shrimp, crabs, frogs, etc. Its typical symptoms are unexplained rhabdomyolysis, with patients experiencing soaring creatine kinase and body aches. Severe patients may experience "soy sauce urine" and renal failure.

The first large-scale report of Haff disease in China was in July and August 2010, when 23 people were infected in Nanjing. After an epidemiological investigation, it was found that they were distributed in 8 families and 4 restaurants in 6 districts of the city, and there was not much connection between them. However, they all ate crayfish, more than 10, and most of them liked to eat the shrimp heads and shrimp roe.

The investigators followed the clues and screened more than 900 substances, including antibiotics, pesticides, heavy metals, etc., but no suspected pathogens were found. In addition, no similar cases have occurred in other places near Nanjing, nor in Shanghai and Beijing, where crayfish consumption is huge.

Although there have been reports of "crayfish causing rhabdomyolysis" every year since then, they rarely cause a big stir. Until 2016, the number of patients suddenly increased. The first case appeared in Wuhan in March of that year. By early August, more than 130 people across the country had been infected, and some even received critical illness notices. The number of patients increased significantly in July and August, with the largest number of patients in Jiangsu and Anhui.

Since July, local government departments have successively issued warnings, and the Centers for Disease Control and Prevention has also strengthened epidemiological tracking. Although the cause of the disease has not yet been found, the common characteristics are similar to the case in Nanjing in 2010: eating more crayfish, and liking to eat the shrimp heads and shrimp roe. The crayfish cannot be blamed for this.

Although no clear cause of the disease can be found, experts highly suspect that it is caused by some algal toxin. This toxin should be heat-resistant, so it cannot be destroyed by cooking. It is likely to be fat-soluble or combined with fat, so it is easy to get it when eating shrimp roe.

In addition, experts also speculate that the outbreak of Haff disease may be related to floods in the south, because there happened to be major floods in 2010 and 2016 (in fact, floods occur every year in the south). The floods not only destroyed farmland and villages, but also "liberated" aquaculture animals, including crayfish.

Floods cause industrial and agricultural wastewater to overflow and water bodies to become eutrophic. After the floods recede, high temperatures in summer cause algae to multiply in large numbers and produce "water blooms" (similar to red tides), which in turn produce algal toxins. Crayfish that escape into the wild accumulate these toxins through algae, and if they are caught and eaten by people, they may be infected.

Affected by the epidemic this year, the catering industry is not as popular as before, but considering the floods in the south and the upcoming high temperature and low rainfall, rhabdomyolysis may occur again. Of course, this is just a guess that has not been verified. As a diner, choose a restaurant or market with a reliable source of goods, eat less or no shrimp heads, and you should be able to enjoy it with peace of mind.

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