Since pre-history, mankind has had an affinity for clams. As humans migrated throughout the world and settled near rivers and along the coastlines, exposing them to the delicacy of clams.
They presented an easily transported and highly nutritious meal, commonly found in estuaries or little more than two feet under the waves and ranging in size from a 0.1mm to 1.2 metres, they came to be a staple of many coastal and islander diets. It has been estimated that early man was such an avid consumer of clams that some species of giant clam declined by as much as 70% as we migrated.
Once humans settled and moved away from a hunter gather lifestyle to an agricultural one, those that lived on islands, by the coast and near rivers continued to eat clams, and eventually cultivate them themselves on vast mud flats, in shallow rivers and shorelines and in estruses’. Evidence has been found of the Romans love for clams, as well as early Puerto Ricans over 2500 years ago, which further evidence suggesting the clams were likely farmed in both these instances.
Had our ancient ancestors been blessed with our modern understanding of health though, they may have stayed away from, Anadara granosa, aka Blood Clams. Cultivated in the Gulf of Mexico, the Atlantic and Southeast Asia, but especially in China, these clams have risen to notoriety and been banned in numerous countries, notably the United States.
Most clams lack haemoglobin in their blood, the protein molecule that gives our blood it’s colour. Blood Clams though, do contain haemoglobin. This gives them both their somewhat gruesome appearance when opened, often oozing blood all over the unlucky individual. More importantly though, it makes them susceptible to the same blood diseases as humans, notably Hepatitis A, typhoid, and dysentery.
Not every clam is deadly, and, on the surface, there is nothing wrong with Blood Clams. That is to say, if raised and harvested correctly, they are harmless. Indeed, many attests to their deliciousness and delicate taste. The problem is not with the clams themselves, but the environment they’re raised in.
It is only Chinese Blood Clams that are banned in the United States for one very simple reason — sanitation. Accurate records of the levels of pollution are difficult to come by in China, but the Shijang River, which feeds the Anhai Bay where 37.5 hectares of clams are cultivated, and Zhejiang Province, where 353 kilotons of Blood Clams are produced yearly, are both notoriously polluted places.
Sewage is left untreated and industrial factories are free to dumb an unregulated toxic cocktail of chemicals into local rivers. These rivers carry the pathogens downstream into the very heart of Blood Clam production. This would be a problem for any food stuff being produced in these treacherous waters, but the haemoglobin in Blood Clams acts as an incubator, carrying the disease, infecting the clam, and eventually whoever is unlucky enough to consume it.
Unusually high numbers of Hepatitis A sufferers have been found in Zhejiang Province, over 76,000 yearly cases during peak figures, a disease which is itself transmitted through food or water that has been contaminated by the faecal matter of an infected individual. Blood Clams are simply the perfect carrier.
This isn’t a hypothetical situation either, outbreaks have happened. In Shanghai in 1988, Blood Clams from Jiangsu Province, another high-risk Hepatitis A region, infected 300,000 people and killed 31. Estimates vary but the chance of contracting Hepatitis A from Blood Clams can be around 16%, though some less conservative sources placed it closer to 33%. Blood Clams are still enjoyed in Southeast Asia though, many choosing to take the risk for dangerous delicacy.
The danger comes not in the clams themselves, but in their source. With so much of Southeast Asia emerging as huge manufacturing centres with rapidly expanding populations, sanitation is often pushed to its breaking point, making the clams from this region perhaps deserving of being banned.
We shouldn’t ignore the fact that this is a man-made problem though, and one we’re trying to fix. The aforementioned Anhai Bay and Zhejiang have been undergoing massive environmental makeovers in the last decade, reducing the risk of contamination, and perhaps leading to an ecological recovery of the clams. But the lack of data from many of these countries, combined with a sometimes less-than-transparent policy on sharing that data, means that it can be near impossible to source clean, disease-free clams from the region.
They remain banned across much of the world for the time being, with raids on Chinatown stores in the United States for illegal Southeast Asian Blood clams being a fact of life for these communities.
For those wanting to try them, Blood Clams from the Gulf of Mexico and the Atlantic are generally considered safe and are available all across North and South America, as well as in parts of Europe, where they are sold as both street food and high-end cuisine. Often eaten raw with a little lime and cilantro, they allow us to reconnect with the flavours of our ancestors, while hopefully remaining disease free.
Side note: While some clams have been found to produce pearls, I couldn’t find any examples of Blood Clams producing them. Has anyone ever heard of this? Does the colouring of the clam affect the pearl in any way?