Recent Hawaiian Monk Seal Deaths Linked to Toxoplasmosis
The recent deaths of three critically endangered Hawaiian monk seals on O‘ahu due to toxoplasmosis, could have been entirely preventable, according to a joint statement from the heads of the Hawai‘i Departments of Health & Land and Natural Resources.
Health Director Dr. Bruce Anderson said that 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 in other animals.
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.
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.
DLNR Chair Suzanne Case, is encouraging people not to feed cats and other animals near water. With only an estimated 1,400 Hawaiian monk seals still in existence, Case said “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,” she said.
“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.”
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.
“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.