Can sharks get sick?

Can sharks get sick?

Ever since the publication of the book Sharks Don’t Get Cancer by Lane and Cormac in 1992, popular myths surrounding sharks have exploded.

Claims have since spread that sharks don’t suffer from diseases at all, and even that their blood or cartilage can be used to treat diseases in humans.

Sales of shark cartilage as a cancer treatment have been met with skepticism from the scientific community.

But is there any truth to the rumors? Can sharks get sick?

The answer is yes, and in fact, they get cancer too. However, they do appear to have much higher immunity to cancer viruses and other diseases, as well as being able to heal remarkably well compared with other animals.

With anything cancer-related, there’s always going to be a sort of hysterical and optimistic reaction from people with high hopes that the new cancer cure is just around the corner.

Because of this, it’s important to follow the science and get the facts right in order not to be caught up with the waves of potentially dangerous excitement.

Sharks do get cancer, but there may be an element of truth to some of the claims, even if it’s not so cut-and-dry. So, let’s take a look at what we know.

Can sharks get diseases?

Sharks have been around for over 450 million years! This means they’ve had plenty of time to develop their immune systems. And what an immune system! Scientists acknowledge the incredible capacity of sharks to fend off diseases that would harm or kill other animals, but sharks are not totally immune to every disease!

Basking sharks have been found with dermatitis and an inflamed heart, herpes in dusky sharks, and a viral infection of the red blood cells in leopard sharks.

Bacterial diseases in sharks are less common, but they do occur too: meningitis, skin infections, and neurological diseases have all been recorded in sharks and attributed to different strains of bacteria.

Vibrio carchariae, the bacterium responsible for the cases of meningitis, can even travel from shark to shark via a parasitic worm, spreading as a contagion.

Bonnethead sharks are unlucky enough to have a disease named after them. The Bonnethead Shark Disease is a fungal infection that can cause skin ulcers or deep hemorrhaging. It affects bonnethead sharks (obviously) and can be fatal to them, but hammerheads are also susceptible to it.

Parasites in sharks are also an issue. Miamiensis avidus is a brain-eating single-cell parasite that affects smoothhound sharks, as well as many other types of fish.

Sharks’ immunity to cancers, however, is a fascinating topic.

Are sharks immune to cancer?

The fact that sharks so rarely get diseases (and the popularity of that provocative book!) hasled to people wonderingabout cancer immunity in sharks and whether this immunity translates to anything useful in human cancer patients.

If sharks are immune to cancer, there must be something in their body that we can extract and use to help make us immune too!

Unfortunately the reality of the situation isn’t as straightforward or optimistic. At least, not yet.

Sharks have some of the highest immunity to cancer that we know of, however, they are not immune to it.

Even the book that started this rumor – Sharks Don’t Get Cancer – concedes that sharks do get cancer – they just don’t get it very often. The reason for sharks’ powerful immunity to cancer is still under investigation, but it has something to do with the certain molecules produced in a shark’s cartilage.

Great whites and bronze whaler sharks have both been spotted with cancerous growths – tumors – growing on them.

This has been documented since the 1800s, in other cartilaginous fishes, and since 1908 in sharks, so it’s not exactly news.

What is a little bit more recent is the suggested mechanism of action for the sharks’ immune systems.

The rarity of cancer in sharks and the observed ability of the shark immune system to fend off cancer has spawned a lot of research into how sharks avoid cancer so well. In particular, two proteins found in shark cartilage have been shown to have strong anti-cancer properties in hammerhead sharks.

This mechanism is thought to have potential in treating human cancers, and has led to shark-cartilage-based cancer treatments becoming available on the market, but are these treatments effective, or are they yet another pseudoscientific attempt to capitalize on the public’s fear and naivete?

Can shark cartilage cure cancer?

To date, there is no commercially available treatment based on using shark cartilage that has shown any effect in treating human cancers in the studies so far conducted.

In trials, shark cartilage was injected into tumors for up to 25 days or was consumed in dosages much greater than those recommended by the manufacturer, with no effect at all on the progression of cancer.

In fact, there is some evidence that shark cartilage treatments can be dangerous.

When cancer patients are understandably desperate for a cure, they can be encouraged by unqualified or even knowingly fraudulent actors to try complementary or ‘alternative’ treatments with no backing in the medical or scientific fields. In these cases, even if the treatment itself isn’t directly harmful, it can be used as a replacement for a potentially effective treatment, hindering or even reversing progress in the improvement of the condition.

The short answer to the question of whether shark cartilage can cure cancer is: no.

People should be extremely wary of anybody claiming it does!

Perhaps some of the proteins in shark cartilage hold secrets to treating cancers in humans, but as of now, it does more harm than good.

Sadly though, many people are scammed by bold claims from charlatans looking to make a quick buck.


Sharks have an exceptional immune system.

They have well-honed defenses against many diseases and rarely get sick – but they do get sick, and they do occasionally get cancer.

Though shark cartilage is probably the source of their powerful anti-cancer immune defenses, so far, no effective treatment for human cancers has been developed from it.

So, for now, please leave the shark cartilage to the sharks.