Mini Lobster Contamination Warning

Summary:
Message warns people not to eat "mini lobsters" because they feed on sewerage, are full of worms and poisonous metals and can cause lung infections in humans (Full commentary below).



Status:
Misleading and inaccurate (Some elements of truth)

Example:(Submitted, April 2008)


Commentary:
According to this emailed warning, people should not eat "mini lobsters" because these small crustaceans can cause serious infection in the lungs of those who consume them. The message claims that these particular type of crustaceans are the "garbage cleaners" in sewage treatment plants and are full of worms and saturated with "poisonous" metals. It warns that consuming the mini lobsters can cause lung infections.

Although there are elements of truth in this warning, it is also misleading and inaccurate. Consuming mini lobsters, which are also called crayfish, freshwater lobsters, "yabbies", and various other names, can indeed lead to lung fluke infections caused by the parasite Paragonimus. There are several species of Paragonimus, but the most common is Paragonimus westermani, or the Oriental lung fluke. Infection can cause very serious health problems in humans. An article about Paragonimiasis on the Stanford University website notes:

©iStockphoto.com/Catherine Henry Not all mini lobsters (crayfish) are dangerously contaminated as suggested in this misleading and erroneous warning message

Following consumption of P. westermani, the larvae pass through intestines and into the lungs, causing the first symptoms of pneumothorax, pleural effusion, and eosinophilia. Later, once the worms are reproducing in the lung tissue, pulmonary infiltrates and hemoptysis occur, the sputum containing dark brown eggs. Without therapy, chronic infection could bring about pulmonary fibrosis, bronchiectasis, and persistent pleural effusion.

However, not all crayfish are infected by Paragonimus as suggested in the warning message. Crayfish are commonly eaten in many parts of the world and are taken from many different freshwater sources including controlled environments such as aquariums and crayfish farms. Thus, it is certainly not true that all mini-lobsters live on sewerage and harbour Paragonimus or worms, nor are they all contaminated with "poisonous" metals. Literally thousands of crayfish meals are consumed at homes and eateries around the world every single day without causing illness or disease.

Moreover, it is not only crayfish that carry Paragonimus. Other crustaceans, including crabs, can carry the parasite. It can also be passed on via unhygienic food preparation and even by consuming infected meat from other animals such as boar. Also, the infection is generally passed on via raw or undercooked crustaceans or meat. Food that is properly cooked and prepared should not pass on Paragonimiasis. An article about Paragonimiasis on eMedicine.com notes:

Among the factors that facilitate the life cycle of the flukes and subsequent transmission of infection to humans are (1) large numbers of reservoir and intermediate hosts, (2) behaviors such as spitting, and (3) culinary habits. In Asia, raw and undercooked crab or crayfish are popular foods. In Korea and Japan, raw crayfish are used to treat measles, diarrhea, and skin conditions. Some tribes in Africa eat raw crustaceans to cure infertility. Peruvians eat raw crab with vegetables and lemon juice. Paragonimiasis may also be acquired by consuming raw meat from a paratenic host that contains young flukes (eg, wild boar as "shashimi"). Infection may also be transmitted via contaminated kitchen utensils (eg, cutting boards, knives) or from cloths used to squeeze and strain juices from crabs for the preparation of soup.

The Stanford University article concurs:

In Asia, an estimated 80% of freshwater crabs carry P. westermani . In Japan and Korea, the crab specie Eriocheir is an important item of food as well as a notable second intermediate host of the parasite. Food preparation techniques such as pickling and salting do not kill the infective organism. In China, the practice of eating "drunken crabs" is especially risky: in an experiment in which crabs were immersed in wine (47% alcohol) for 3-5 minutes, then after five days fed to cats and dogs, the infection rate was 100%.

Paragonimus has a quite complex life-cycle that involves two intermediate hosts as well as humans. Eggs first develop in water after being expelled by coughing or being passed in human feces. In the next stage, the parasite invades an intermediate host such as a species of freshwater snail. In a later stage, they emerge and invade another host such as crabs or crayfish. Finally, the may be passed onto humans to complete the cycle. Therefore, it is entirely possible for crustaceans that do not live in or near sewerage treatment plants to carry the parasite. In fact, crayfish populations are quite susceptible to water pollution, including sewage, so a sewage treatment plant would certainly not be an ideal environment for them as is suggested in the message.

Thus, although Paragonimiasis is a significant threat, especially in Asia, it is quite misleading to suggest that it is only passed on by mini lobsters. It is also inaccurate to claim that all mini lobsters are contaminated, when this is quite clearly not the case. Passing on misleading and inaccurate health-related information is counterproductive. For example, a person who has seen and believed this warning might forgo a properly cooked meal of crayfish and opt for a dish comprising raw crab - a dish much more likely to pass on the parasite than the cooked crayfish. It is therefore especially important that recipients check the validity of such health warnings before passing them on to others.

References:
Paragonimiasis
eMedicne: Paragonimiasis

Last updated: 23rd April 2008
First published: 23rd April 2008

Write-up by Brett M. Christensen

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