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Facts About Whale Parasites

Parasites are a common problem among cetaceans. Many times parasites do not pose a threat to whales and can be quite beneficial. In fact, the most beneficial parasites are actually crustaceans. There are a few parasites that can cause serious health issues and eventually death. Some of these include nematodes (round worms), trematodes (flukes), dignenea (tapeworms), and acanthocephala (thorny-head parasites).



Barnacles are considered the most common external parasite that are known to plague whales. What many people don't realize is that barnacles aren't actually parasites at all. They are considered crustaceans. Barnacles and whales tend to have more of a symbiotic relationship.

There are 1,220 species of barnacles. However, only a small fraction of these species actually attach to whales. The sessile barnacle, or acorn barnacle, is the most common. This barnacle will drift through the water as a larva ultimately attaching itself to the whale and extend out feather-like filters to catch plankton. They choose to attach to baleen whales, such as gray whales, so the whales will take them through currents typically filled with plankton.

Typically barnacles don't cause harm to the whale unless there is a high concentration around the whale's blowhole, which prevents the whale from breathing. The most common problem with barnacles is when a barnacle dies and falls off or is scraped off. It causes scaring to the whales skin that take years to heal if it heals at all.

Whale Lice

Whale Lice

Whale Lice

Whale lice are the second most common parasites whales suffer from. They are considered an amphipod crustacean. Whale lice have flat bodies with hooks at the tip of their legs. Many times these parasites can be found hidden within folds in the skin, wounds, and among barnacles, another type of parasite.

There are several species of whale lice. Cyamus scammoni is considered the largest and most common to be found on a whale. They differ from other species of whale lice because they have curly gills on their underside, whereas the other species have straight gills. They feed off of the surface of a whale with a diet of flaking skin typically around wounds and barnacles. These parasites seem to be more helpful than other parasites because they clear away dead skin.

Whale lice spend their entire life cycle on the body of whales. They can be transferred from whale to whale by touch, but they never free float or swim through the water to their next host. Female whale louse are generally only a half an inch, but male louse can grow to over an inch long. Another interesting fact about whale lice is that young whale lice grow inside a pouch-like structure under a female whale louse until they are ready to crawl out on their own.

lung worms

lung worms

Lung Worms

There are four species of lung worms that attack the lungs of whales, dolphins and other marine mammals. Lung Worms are a type of round worm that affects the lungs and can cause several complications including pneumonia. Heavy infestations can cause blockage to the airways along with inflammation that could create abscesses and eventually death if untreated.

Lung worms are typically less than seven centimeters long and are white with a thread-like appearance. These worms can even survive in the lung of a dead whale. They are much smaller than those in a live host. Infestations are generally causes by consuming fish or squid that are already infected. Most whales in captivity are fed frozen fish to aid in prevention of lung worms.

According to the Merck Veterinary Manual, an infestation of lung worms tend to be asymptomatic, meaning the whale rarely shows any clinical signs. Treatments are available. However, in some cases the lasting damage of treatment may be worse. Some cetaceans have had neurological damage and even sudden death.


A tapeworm is a long parasitic worm that absorbs nutrients through its skin from the digestive tract. The longest tapeworm came from a whale and measured at one hundred and twenty feet. The tapeworm will hook itself into the wall of the intestine with its teeth. They can cause a whale to become malnourished, but as long as enough nutrients are absorbed for the whale and the parasite there generally aren't complications.


Toothed whales are the most susceptible to the parasite Nasitrema sp. These parasites sometimes travel to the brain causing severe damage. They can also infect the heart, lungs, intestines, liver, and other organs. These parasites will lay over 10,000 spiny eggs a day causing significant damage to tissue. They also secrete a toxic waste that causes more damage to the tissue.

Sea Lampreys

Little is known about these parasites. Sea lampreys latch on to a host with their suction-cup mouth, tearing away skin with their razor-sharp teeth and tongue. They will secret a substance that will prevent the host from forming blood clots allowing them to feed as long as they like. Unfortunately, some hosts will die from infection or extreme blood loss. Fin whales, minke whales, and right whales tend to be the whales most affected by this pest.

Crassicauda sp.

This type of parasite attacks the kidneys of whales. They nest in large numbers in the vessels found in a whale's kidney causing severe damage to the kidney itself. Crassicauda sp. is a type of round worm that embeds its head into the kidney's tissue. The tail of this parasite is left exposed in order to release eggs in the urinary tract. The Crassicauda sp. parasite creates a fibrous structure in the vessels of kidney thus causing blockage preventing flow into and out of the kidney. Ultimately this causes kidney failure and death.

The Crassicauda sp. has also been known to attack the cranial sinuses of toothed whales. The damage is just as bad as when they attack the kidneys. With a cranial sinus infestation, it can affect their brain function. Many times whales afflicted with these parasites tend to beach themselves because their sense of direction is affected. Regardless, the end result is usually death.

Beluga whales and blow head whales are two whales most susceptible to the Crassicauda sp. parasite, however all baleen and tooth whales can be affected by this parasite.

As parasites become an increasing problem among whales, marine biologists are trying to learn more about the effects of parasites on their cetacean hosts. They are also researching various treatments in order to help whales not only in captivity but in the wild as well.

© 2015 Linda Sarhan