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.
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.
Last updated: 23rd April 2008
First published: 23rd April 2008
Write-up by Brett M. Christensen
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