Category: Timely Topics

Toxoplasmosis Facts

“Toxoplasma gondii is common, worldwide and everywhere and affects a variety of mammals and birds” – Companion Animal Parasite Council

• Leading cause of toxoplasmosis in humans is through ingestion of undercooked meat. – CDC
• Direct contact with cats is not considered to be a risk factor for toxoplasma infection in people, particularly when cats are kept indoors and fed a commercial diet. – CAPC
• Toxoplasmosis is transmitted to humans from cats when humans accidentally swallow the parasite through contact with cat feces that contain Toxoplasma. – CDC
• Toxoplasmosis can be prevented if the following are done: clean the litterbox daily (the parasite takes 24 hours to become infective in cat feces), wash hands with soap and water after exposure to soil, sand, raw meat or unwashed vegetables, and ensure cats are kept indoors and eat only cat food. – CAPC
• Only about 1% of cats are active hosts of toxoplasmosis able to shed the parasite. – CAPC
• Infected cats shed for only about 1 to 3 weeks following infection. – CAPC
• Because cats only shed the organism for a few days in their entire life, the chance of human exposure is small. – CFHC
• Cats and dogs become infected with toxoplasma by ingestion of infected mammalian or avian tissues or ingestion of the parasite from articles contaminated by feline feces (e.g., soil, water, vegetation). – CAPC
• About 19% (˜60 million) of the human population in the United States has already been exposed to (may be infected with) Toxoplasma. Of those who are infected, very few have symptoms because a healthy person’s immune system usually keeps the parasite from causing illness. – CDC
• A 2013 study by VanWormer, et al. showed reduced prevalence of toxoplasmosis in cats who were fed and considered managed by humans as compared to wild felids and cats subsisting on wild prey.

Solutions to Consider

• Keep cats indoors and prevent them from hunting and consuming undercooked meat, encourage cat owners to scoop litterboxes daily.
• Support sterilization to reduce kitten births, since kittens and young cats are at greatest risk to become newly infected and shed the parasite.
• Advocate for wildlife officials, conservationists, animal welfare advocates and veterinarians to work together to solve problems using the latest science combined with humane methods.

Resources/ References

• Companion Animal Parasite Council (CAPC) – www.capcvet.org
• Centers for Disease Control and Prevention (CDC) – www.cdc.gov
• Cornell Feline Health Center (CFHC) – www.vet.cornell.edu/fhc/
• VanWormer, E., P.A. Conrad, et al. (2013). “Toxoplasma gondii, Source to Sea: Higher Contribution of Domestic Felids to Terrestrial Parasite Loading Despite Lower Infection Prevalence.” EcoHealth 10, 277-289

HVMA Cats and Toxoplasmosis Information Sheet 12 28 16

Hawaiian monk seals are listed as endangered under the U.S. Endangered Species Act and are protected by Federal and state law. This unique tropical pinniped is found exclusively within Hawaii’s waters, mostly throughout the low-lying atolls of the Northwestern Hawaiian Islands. However, monk seals have been recolonizing the main Hawaiian Islands over the past two decades. This subpopulation is estimated at 200-250 seals, and is growing. With that growth comes the recognition of new threats to the species such as fish hook ingestion, intentional killing, and now, an accumulating number of deaths from toxoplasmosis. This is not surprising, given the increasing geographic overlap between humans, cats, and Hawaiian monk seals.

A total of 8 monk seal mortalities (and 2 suspect mortalities) have been attributed to toxoplasmosis to-date. We arrived at this number by developing a case definition and retrospectively applying it to 306 cases of mortality from 1982-2015. To be classified as a protozoal-related mortality, we required: (a) pathological lesions consistent with protozoal disease and sufficient to cause mortality, and (b) confirmation of the organism in direct association with these pathologic lesions by immunohistochemistry. Supporting data such as serology and molecular analyses were provided when available. The results were recently published in the peer-reviewed journal, “Diseases of Aquatic Organisms.”

While 8 deaths may not sound like a large number, NOAA is growing increasingly concerned about the threat of toxoplasmosis for several reasons. First of all, the number of monk seal mortalities attributed to toxoplasmosis is an underestimate. More seals disappear each year than are found sick or dead. Even when carcasses are found, they may be too decomposed to definitively identify this infection as a cause of mortality. Vertical transmission to fetuses has been documented in monk seals, however failed pregnancies can be difficult to detect in wild animals. The outlook for treating sick seals is poor because of the rapid, severe, diffuse inflammatory response in the infected seal and because drug choices and delivery routes are far from optimal. Only two seals have been assessed prior to death, but both declined rapidly and could not be rehabilitated. Unlike threats such as fish hook ingestion or malnutrition, which can often be mitigated through rehabilitation, our options are severely restricted when it comes to treating seals for toxoplasmosis. Even if there were improvements in treatment modalities, most cases are simply found dead on the beaches. The population level impact of each mortality exceeds the loss of one seal because the future reproductive potential of that seal is also lost.

NOAA is one of a handful of Federal and state agencies that have met in 2016 to discuss the complex problem of cats in Hawaii and the threats (disease, predation) they pose to native wildlife. The group is still formalizing its mission, scope and membership, but for now, it is focused on compiling and disseminating the best available science on this issue. In time, subgroups will be developed to focus on specific topics. The group will seek participation from outside (non-agency) groups, including veterinarians – so stay tuned.

Through some of our ongoing research partnerships, we at NOAA are investigating the prevalence of exposure within the monk seal population using serology and molecular analyses. Evidence of previous exposure to T. gondii has been documented in a few apparently healthy monk seals as well, so we are very interested in this dichotomy. To address that, we are working with external partners and experts in this field to better understand the epidemiology of this pathogen in monk seals and the risk factors related to the host, pathogen and environment. I hope to be able to share the results of these studies with all of you in the years to come and I welcome your questions or dialogue on this topic.

Michelle Barbieri, DVM, MS

Wildlife Veterinary Medical Officer

Hawaiian Monk Seal Research Program

As the primary veterinarian for NOAA’s Hawaiian Monk Seal Research Program, Dr. Michelle Barbieri oversees wild monk seal disease surveillance, population health studies, vaccination, rehabilitation, and provides veterinary support to the program’s other research objectives.

References:

Honnold, S.P., Braun, R., Scott, D.P., Sreekumar, C. and Dubey, J.P., 2005. Toxoplasmosis in a Hawaiian monk seal (Monachus schauinslandi). Journal of Parasitology, 91(3), pp.695-697.

Barbieri, M.M., Kashinsky, L., Rotstein, D.S., Colegrove, K.M., Haman, K.H., Magargal, S.L., Sweeny, A.R., Kaufman, A.C., Grigg, M.E. and Littnan, C.L., 2016. Protozoal-related mortalities in endangered Hawaiian monk seals Neomonachus schauinslandi. Diseases of Aquatic Organisms, 121(2), pp.85-95.