During the week of May 14, 2018, three Hawaiian monk seals were found dead on O`ahu. One was RK60 (Nani) who was born on an islet off Oahu known as Rabbit Island in 2011. She’d given birth to one pup in May of 2017.
The second dead seal was RT10 (Ua Malie) who was born at Turtle Bay to R5AY (known as Honey Girl on Oahu and K01 on Kauai). She’d pupped three times before.
The third dead seal was a small but fully developed pup. NOAA officials feel this pup was born dead and, based on an examination, likely to RT10.
The Hawaiian Monk Seal Research Program responded by conducting necropsies on all three and today released the news that the cause of death for all three was toxoplasmosis.
In 2015, Kaua`i-born RB24 (Haupu) died of toxoplasmosis.
According to a joint statement from the Hawaii Department of Land and Natural Resources and Hawaii Department of Health, “The recent deaths of of three critically endangered Hawaiian monk seals on Oahu due to toxoplasmosis is very sad and could have been entirely preventable.”
The rest of the press release reads:
Cats are the only known reproductive host of the toxoplasmosis parasite. It reproduces in the feline digestive system. A single cat can excrete 145 billion eggs per year in its feces. Once released into the environment, these eggs can infect other animals, including humans, both on land and in the ocean. Toxoplasmosis parasites create cysts in muscle and organ tissues and can cause inflammation of the heart, liver, and brain.
Health Director Dr. Bruce Anderson explained that the parasite that NOAA veterinarians found caused the deaths of the seals is far more impactful than just killing seals.” In addition to impacting marine mammals and wildlife, toxoplasmosis is a risk to humans. It is known to cause serious problems for pregnant women and their unborn children,” Anderson said. “During pregnancy, infection by the toxoplasmosis parasite can damage the unborn child, causing miscarriages, stillbirth, or substantial birth defects including enlargement or smallness of the head.
For healthy individuals, symptoms and signs of toxoplasmosis infection are most often benign because a healthy person’s immune system usually keeps the parasite from causing illness. Very few people will have symptoms similar to the flu and most people probably do not know they have been infected. The Centers for Disease Control and Prevention estimates that approximately 10 percent of the population in the U.S. six years of age and older have developed antibodies to the parasite from a past infection. However, for those with compromised immune systems, those undergoing chemotherapy or with AIDS, and for pregnant women the disease can be very serious.
“The only thing certain about toxoplasmosis is that there are far more cases in humans and more deaths in seals, dolphins, native birds and other animals today than are recognized and reported,” said Anderson. “Since cats are the only animal that transmit the disease, it only makes sense that reducing the number of feral cats will reduce the risk of infection and serious illness or death,” Anderson added.
DLNR Chair Suzanne Case, is again encouraging people not to feed cats and other animals near water. “In addition to preying on native wildlife, cats pose a significant health risk to people, marine wildlife and birds,” Case explained. Toxoplasmosis can also infect Hawai‘i’s native birds, including the nēnē and the newly released Hawaiian crow, the ʻAlalā.
“Feeding cats near water obviously increases the risk of transmission but, given the nature of the watersheds in Hawai‘i, cats almost anywhere are probably contributing to the problem,” Case said. “The cysts can live for months in soil and can wash into streams and runoff and be carried into the ocean from almost anywhere. Feeding cats at state parks, boat harbors and other coastal areas increases the risk of transmission because the cysts don’t need to travel very far to get into the ocean.” Case added, “Frankly, feeding cats anywhere where their feces can ultimately wash into the ocean is a problem.”
One of the seals, RK60, killed by toxoplasmosis gave birth to a pup on Moku Iki off shore from Lanikai in the spring of 2017. This seal and her pup moved to Moku Nui and were featured in a safe wildlife viewing video produced by DLNR and shown over the past year to thousands of people who rent from Kailua kayak rental firms (see video link below).
In Hawai‘i, the National Oceanographic and Atmospheric Administration has recorded at least eleven Hawaiian monk seal deaths that are attributable to toxoplasmosis infection since the first confirmed deaths in 2001. Spinner dolphins are the only other marine species that have been documented as dying from toxoplasmosis in Hawai‘i, but there are many other marine mammal species around the world that have also been affected and infections have been linked to the marine food web. This, according to Case and Anderson, should be enough to prompt people to stop feeding feral cats near any bodies of water.
“With only an estimated 1,400 Hawaiian monk seals still in existence, we simply cannot afford to lose even one of these critically endangered mammals to a disease that is preventable. We hope people will provide as much love to our few very special seals as they do to the hundreds of thousands of feral cats around our islands,” Case said.
Multiple tests were conducted on each seal, all of which pointed to toxoplasmosis as cause of death in each case. Toxoplasmosis causes inflammation and disrupts organ function of the blubber, brain, heart, lung, uterus, and for the pup, placenta. Eventually, this led to multiple organ failure and death.
The total number of known monk seal mortalities due to toxoplasmosis is now 11. Toxoplasmosis is the leading cause of disease-related mortality in Hawaiian monk seals and a growing concern for the recovery of the species.
Alongside the growing threat of toxo is the emerging trend whereby more female seals are disproportionately affected–three males and eight females. This exacerbates the impact on the entire species, as each female lost means all her potential future offspring are lost as well.
Toxoplasmosis is caused by a microscopic protozoan parasite, Toxoplasma gondii. It enters the environment when its eggs are shed through the feces of cats. Billions of eggs can be dispersed into the environment from just one cat over a two week period of infection. The eggs remain alive and infectious for months to years after they leave the cat, where they can infect birds and mammals. The disease is responsible for killing native birds like the `alala and nēnē in the terrestrial environment. The organisms can also be washed downstream by rainfall and flow into the nearshore environment, where they infect monk seals as well as spinner dolphins. Because this is a mauka to makai problem, cats that roam and defecate outdoors in any part of the island ecosystem can become carriers and spreaders of toxoplasmosis and ultimately cause the death of native wildlife.
Seals that are sick from toxoplasmosis may not show obvious warning signs of illness, but some have shown subtle indications such as floating lethargically close to shore in areas with calm, protected waters in the past.
A more concerted effort to mitigate the risk of toxoplasmosis to endangered Hawaiian monk seals, as well as other wildlife species, is urgently needed. This primarily requires dealing with the source of environmental contamination: Hawaii has a large population of cats, including hundreds of thousands of feral cats,, that are allowed to freely roam and defecate outside. Infected cats typically do not show any signs of disease themselves. There is currently no vaccine against Toxoplasma gondii in cats. To diminish the threat of toxoplasmosis to seals, the input of organisms into the environment must be reduced, necessitating a significant reduction in the number of feral cats on the islands. Spaying and neutering cats does not change their capacity to perpetuate the parasite and spread it into the environment.
Cats that are kept exclusively indoors have a much lower chance of completing the T. gondii life cycle and are therefore highly unlikely to shed infective oocysts into the environment. Preventing abandonment and keepings cats indoors is best for the welfare of all animals – cats, native birds, monk seals and dolphins.
To learn more about toxoplasmosis, see our post from late March, entitled Toxo Talk.
