Toxoplasma gondii is a single-celled parasite that causes toxoplasmosis, which is manifested clinically in severe cases by jaundice, vision impairment, and liver and spleen enlargement. The microscopic protozoan is often found encysted in nerve tissue, and proliferative forms and cysts can infect numerous species of birds and many species of warm-blooded animals, which act as intermediate hosts. Feline species are the only definitive hosts for the organism. Cats harbor sexual stages of the parasite in their gastrointestinal tract and shed infectious oocysts in their stool. Intermediate hosts become infected by ingesting the sporulated oocysts from cats. Humans can contract the disease by ingesting inadequately cooked meat (especially lamb, pork, and mutton) of the intermediate hosts that have been infected, or by ingesting oocysts from soil or water contaminated with cat feces. In fact, toxoplasmosis is one of the leading causes of death attributed to food-borne illness, and precautions to ensure food safety must be followed. See also: Parasitology; Protozoa; Saliva-based immunoassay of waterborne pathogen exposure; Sporozoa; Toxoplasmea; Toxoplasmida; Zoonoses

According to the Intergovernmental Panel on Climate Change (IPCC), to avoid the major impacts of climate change, such as deadly heat and decreased crop yields, will require limiting global warming to a maximum increase of 1.5 to 2.0 degrees Celsius. The IPPC Working Group I report, Climate Change 2021: The Physical Science Basis, says that limiting global warming to 1.5 to 2.0 degrees Celsius will require the removal of carbon dioxide (CO₂) from the atmosphere in addition to converting fossil-fuel energy technology to renewable energy sources such as solar and wind power. Carbon capture and storage through direct technological capture or through enhancing biological or geological carbon sinks is neither simple nor inexpensive. Because no single carbon-capture method will solve the problem, many carbon approaches will likely be needed. See also: Carbon dioxide; Deadly heat in an era of global climate change; Extreme weather events; Fossil fuel; Global warming; Solar energy; Wind power

Researchers have discovered an antimalarial compound that shows promise for killing the deadliest malaria parasite, Plasmodium falciparum, at multiple stages of its life cycle. High-throughput screening of more than 4700 molecules yielded an effective antimalarial molecule that was further chemically optimized to produce a quinoline diamine, called DDD107498, which kills the parasite by inhibiting its ribosomes' ability to synthesize proteins. The research team, led by scientists from the Drug Discovery Unit of the University of Dundee in the United Kingdom, reported this result in the journal Nature (June 2015). See also: Haemosporina; Malaria; Medical parasitology; Parasitology; Pharmaceutical chemistry; Sporozoa

By July 6, 2018, beaches on the eastern coast of St. Vincent—an island located in the southeastern Caribbean Sea (Lesser Antilles)—were covered nearly one-meter deep with rotting brown algae (seaweed), known as Sargassum, posing multiple problems for both its human population and its marine ecosystems. St. Vincent was only one of the many Caribbean islands affected both economically (because of loss of tourism) and environmentally by largest Sargassum outbreak since 2011 when this seaweed began washing up on beaches. See also: Algae; Fucales; West Indies

Destructive blooms of Karenia brevis, a dinoflagellate species of algae that imparts a red color to ocean waters when the microorganisms grow and accumulate to unusually high quantities, are causing unprecedented environmental and ecosystem damage along the southwestern coast of Florida. Commonly known as red tides, these harmful algal blooms (HABs) deplete the levels of dissolved oxygen in ocean water and produce potent toxins—specific neurotoxins termed brevetoxins—that are poisoning and killing thousands of fish, sea turtles, and marine mammals, including dolphins and manatees. In addition, the harmful algal blooms are having a major economic impact because the beaches and waters affected by the red tides need to be closed to tourists and fishing enthusiasts. In many locations, dead fish and other marine animals are washing up along the southwestern Florida coastline. Compounding this issue, the brevetoxins often impart a foul odor to the air, making these areas quite unattractive. These areas are also potentially harmful to humans. For example, chronic inhalation of the red tide brevetoxins (which can become aerosolized) can result in pulmonary irritation and illnesses in humans. Also, the ingestion of shellfish contaminated by brevetoxins can cause serious gastrointestinal health risks to humans as well. See also: Algae; Cetacea; Chelonia; Ecological communities; Ecology; Ecosystem; Emerging diseases in marine mammals; Environmental toxicology; Fisheries ecology; Marine ecology; Sirenia; Toxin